_ .. .. . . . .. » v~ n . - ..... .. "u .. ‘ »‘ - w-x- ' * * "-‘.‘.t"“ "' *"nxravtv'x‘i A ‘ ‘ _> ~ V ‘ I - ' ‘ v 3 1293 00784 9205 Illllllllllll‘lllllllll lulllllll ’ l LIBRARY Michigan State University This is to certify that the dissertation entitled Diagenesis of aluminosilicate minerals in the New Haven Arkose and East Berlin Formation (Triassic-Jurassic), southern Hartford Basin, Connecticut. presented by Mounir K. Saad has been accepted towards fulfillment of the requirements for Ph.D. Geology degree in Mix/WM Major professor Date féfi 22/ /77/ MS U is an Affirmative Action/Equal Opportunity Institution 0-12771 135/35 i‘? PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. DATE DUE DATE DUE DATE DUE 4| |[:_JL _7 7 7 __| l MSU Is An Affirmative Action/Equal Opportunity Institution emana-m DIAGBNBSIS OP ALUMINOSII-ICATH NINHRALS IN THE NEH HAVEN IURJNDEHBtAND EAST BERLIN FORMATION (TRIASSIC-JURASSIC), SODTHHRN HARTFORD BASIN, CONNECTICUT. by xcunir x. Saad A THESIS Submitted to nichigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Geological Sciences 1991 ‘7 ko/ cv' ABSTRACT DIAGENESIS OF ALUMINOSILICATE MINERALS IN THE NEW HAVEN ARKOSE AND EAST BERLIN FORMATION (TRIASSIC-JURASSIC) , SOUTHERN HARTFORD BASIN, CONNECTICUT. BY MOUNIR KAMEL SAAD Late Triassic and Early Jurassic fluvial sandstones of the Hartford Basin contain of a complex assemblage of diagenetic minerals. Sample examination using thin-section petrography, SEN, BSEH, EDS, and EHPA techniques was performed in order to constrain compositional and textural relationships among authigenic aluminosilicate minerals in the New Haven and East Berlin Formation. The diagenetic history of the New Haven Arkose (fluvial) and the East Berlin Formation (fluvial/lacustrine) is similar and shows that compaction was the earliest process in these rocks. However, albitization, illitization, and zeolite cementation are more extensive in the more deeply buried New Haven Arkose. an analysis reveals that illite is the predominant clay mineral present in these sandstones. The presence of interstratified illite-smectite layers suggest possible formation of illite from a smectite precursor. The abundance and distribution of albitized feldspars, chlorites, and zeolites varies between the stratigraphically shallower East Berlin Formation and the deeply buried New Haven Arkose. Albitization of K-feldspars, and authigenic chlorites, increase down section. Type 1 albite is common in the East Berlin Formation, whereas type 2 albite is common in the New Haven Arkose. Detrital chlorite is present in both formations, whereas authigenic pore-filling and pore-lining chlorite cement is confined to the New Haven Arkose. Chlorite increases in abundance with depth among the deeper samples. Petrographic and XRD results suggest the authigenic chlorites are jpolytype Ib and. detrital chlorite is. polytype IIb. Throughout the stratigraphic thickness of the New Haven Arkose, diagenetic facies varies from a zeolite (laumontite)i facies, to zeolite/chlorite facies, and finally to chlorite facies with increasing burial depth. The variation in abundance and distribution of different diagenetic cements and replacements found in the New Haven Arkose and the East Berlin Formation suggests that the main diagenetic processes are temperature and depth related. Dedicated to my lovely wife and my daughter "Without your support and sacrifice, my wife, this work will never be done". '-Feb. 22 p 1990 ACKNOWLEDGMENTS I would like to thank my advisor, Dr. Michael A. Velbel for his guidance, support, energy in keeping me inspired, and patience during my graduate experience at Michigan State University. I would like to thank my committee members Duncan Sibley, Max Mortland, and David Long for their encouragement and the teachings I had from their courses. I am particularly indebted to Duncan Sibley for the advice and help he gave me. Tom Vogel and Kazuya Fuj ita are thanked for their support and help during the hard times. I greatly appreciate the assistance and patience of Loretta, Cathy and Jackie from the geology office. A special thanks to Diane in finding out and tracking any possible article related to my research. The help of Bob Harris for his assistance and suggestions during the thin-sections preparation is sincerely appreciated. Thanks to my fellow graduate students Bob Brown, Marco Antonellini, Rich Carroll, Erin Lynch, Marcia Schulmeister, John Brannen, Steve Nordeng and many others for their friendship, interesting discussions and help during my ii graduate work. I would like also to acknowledge the assistance and help given to me by Amideast and the Egyptian Cultural and Educational Bureau during this "american" experience. Finally, I thank my beloved wife and daughter for their understanding and unconditional love, support and sacrifice. iii TABLE OF CONTENTS LIST OF TABESOOOOCOOOOOOOOOOOC00....OOOOOOOOOOOOOOOOOCViii LISTOF FIGURESOOOOOOOOOOOOOOOOOOOOOOOOOOO0.0.00000000000j-x CHAPTER 1: INTRODUCTION.............. ..... ...... .......... l Paleogeographic History..............................3 Geographic position.............. ..... . ......... 6 Description of the Studied Formations................7 New Haven Arkose....................... ..... ....9 East Berlin Formation................ ......... .15 Previous Petrographic Work and Objectives...........19 CHAPTER 2: SAMPLING AND ANALYTICAL METHODS...............25 Sample Collections and Localities...................25 Petrographic Thin-sections..........................25 XRD and Clay Preparation Techniques.................27 CHAPTER 3: PETROGRAPHY...................................29 New Haven Arkose....................................29 Stop 4.........................................37 Stop 3.........................................39 Stop 2.........................................49' East Berlin FomationOIOOOOOOOOOOOOOOOOOOOOOOOOO0.0.52 iv Stop1......................0.......0 0000000000 52 Distribution and Genesis of the Bulk Rock MineralogYeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee58 Provenance and Evolution of the Arkosic Sandstones..62 Paragenetic Sequence of the Hartford Basin sandstones.0...0.....00..00...0...000....0.... ..... 66 CMER 4: Cmy MINERAIDGY0000.00.0..00.00.00..........0074 Clay Mineral Identification.............. ........... 74 New Haven Arkose... ................................. 78 East Berlin Formation ..... . ......................... 83 l- Floodplain System........ ..... . ............. 86 2- Perennial Lake System..... ........ .. ........ 89 Origin and Distribution of the Clay Minerals ........ 95 Illite.................... ................... ..98 Chlorite... .......... . ......................... 99 Smectite...... ................................ 100 Vermiculite.................... ............... 101 Interstratified Illite-smectite.. ........... ..101 Corrensite........................ ............ 105 Origin of chlorite-smectite..............107 Origin of chlorite-vermiculite. .......... 109 Summary of the Clay Mineralogy...... ..... .... ...... 110 CHAPTER 5: DIAGENETIC ALBITIZATION OF FELDSPARS.........112 Petrology and Textures of Albitized K-feldspars....113 Type1.0....00... ..... 0....0....0.........0.0.120 Type 2.....0...........00.............0...0...123 Albitization of detrital P1agioc1ase.. .......... ...125 Electron Microprobe Analysis.......................127 Origin of Albitized K-feldspars....................127 Process of Albitization in the Studied Formations..136 sources Of SOdium......0.............0...0...0.....140 CHAPTER 6: CHLORITES...................... ..... .... ..... 143 Morphology of Authigenic Chlorite........ .......... 145 Grain-coating Chlorite-vermiculite.. ...... ....147 Pore-lining Authigenic Chlorite.. ............. 147 Pore-filling Authigenic Chlorite..............150 X-ray Diffraction .................................. 150 Electron Microprobe Analysis.... ................... 154 Chlorite Polytype Analysis... ...................... 156 Origin of the Chlorites......... ..... ..............160 Detrital Chlorite......... .................... 160 Authigenic Chlorite...........................161 Grain-coating chloritic clays............l62 Pore-filling and pore-lining chlorites...165 CHAPTER 7: ZEOLITES.....................................168 Laumontite........................... .............. 169 Controls on Laumontite Formation..............17l Analcime...........................................176 Controls on Analcime Formation................176 vi CHAPTER 8: SUMMARY AND CONchIONS.........0....00..0.00179 Future studies ..................................... 188 Appendix A: Microprobe analyses of albitized K-feldspar.189 Appendix B: Microprobe analyses of plagioclase feldspar.206 Appendix C: Microprobe analyses of K-feldspar. ....... ...212 Appendix D: Microprobe analyses of Chlorite.. ..... . ..... 222 Appendix E: Microprobe analyses of zeolite .............. 224 Appendix F: SEM and BSEM analyses... ............... .....226 LIST OF REFERENCES... ................................... 231 vii Table Table Table Table Table Table LIST OF TABLES Petrographic point counts of the New Haven Arkose. 30 Petrographic point counts of the East Berlin Fomtion000.00000000000000.0000... .......... 0000.53 Clay mineralogy of the New Haven Arkose. . . . . ...... 79 Clay mineralogy of the East Berlin Formation. ..... 84 Variation of authigenic aluminosilicate minerals with change in burial depth and temperature. . . . . . 181 Summary of possible origin of elements required for the main diagenetic processes....................187 viii Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure l 2 3 4a 4b 5a 5b 7a 7b 7c LIST OF FIGURES Basins of the Newark Supergroup along eastern North America (afterVanHouten, 1977). . . . . . . . . . . . . . . . . . .2 The stratigraphic framework of the Upper Triassic and Lower Jurassic in the Hartford Basin, Central connecticut (Hubert ital. ’ 1976) . . . 0 . 0 . . . . 0 0 . . . 0 0 0 4 Paleogeographic map showing various depositional environments of the East Berlin Formation. Paleowind direction was determined from paleocurrent readings in shallow water and shoreline sandstone of temporary and perennial lakes (Hubert at al. , 1976).........0.......................00.00.00.00008 Geological map of central Connecticut showing the location of the four sampling stops. . . . . . . . . . . . . . . 10 Schematic cross-section (A-A') of the Hartford Basin showing the relative stratigraphic position of the three stops of the New Haven Arkose. Cross-section direction is illustrated in Figure 4a. . . . . . . . . . . . . 11 Measured section of the New Haven Arkose at stop 2 along route 40, North Haven (modified after Hubert fifl0' 1978)0.00....0.000.000.0000000.000.0000.0012 Measured sections of the New Haven Arkose at stop 3and4................0.............0.0.0.0....0014 Stratigraphic section of the perennial lake cycle in the East Berlin Formation, stop 1, Cromwell (modified after Hubertgtgl. , 1976) . . . . . . . . . . . . . .17 QFR ternary diagram illustrating the sandstone composition of the New Haven Arkose and the East Berlin Formation (after Pettijohn er, a1. , 1987) . . .34 QFR ternary diagram of the mean values of percent point counts of the different stops. . . . . . . . . . . . . . . 35 QPK ternary diagram of point count data of the differentst°p800000...00....0....00.......0...00.36 ix Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 10 11 12 13 14 15 16 17a Pebble and cobble conglomerate in epidotic arkosic sandstone matrix of stop 4 of the New Haven Arkose. Notice the unconformity surface between Paleozoic Milford chlorite schist and Upper Triassic New Haven Arkose basal conglomerate.........................38 Photomicrograph of pore-lining chlorite. Notice hematite coating of detrital quartz and absence of chlorite at grain contacts. Sample # NH-4-6. (Frame dimensions: 0.4 mm x 0.6 mm) . . . . . . . . . . . . . . .40 Fractured potash feldspar f i 1 led with hemat ite- stained clay. Sample # NH-4-5. (Frame dimensions: 2.5mx3.BM)0....0....0..................000.040 Minor calcite cement filling fractured feldspar. Notice the optical continuity between fracture and pore-filling calcite. Sample # NH-4-3 . (Frame dimensions: 2.5mmx3.8mm)41 Deformed mica (biotite) during compaction of early cementing material. Sample # NH-4-5. (Frame dim.: 1.0mmx1.SM)...0...........0.......0..0.....0041* Clear euhedral quartz overgrowths rim detrital quartz grains. Sample # NH-4-3 . (Frame dim. : 2 . 5 mm x3.8m)...0.....0...0.......000....0.00.00.00.0042 SEM photomicrograph of pyramidally terminated quartz overgrowths. Sample#NH-4-5.....................42 Double hematite line outlines the boundary between the quartz-overgrowth and the detrital quartz grain. Sample # NH-4-3. (Frame Dim.: 1.0 mm x 1.5 mm)...............................................43 Photomicrograph of partly albitized K-feldspar riddled with abundant minute inclusions. Sample # NH’3’16e (Frame dime: 2.5mmx3o8 M)eeeeeeeeeeee43 Clear feldspar overgrowths rim detrital core filled with inclusions. Sample # NH-3-3 . (Frame dim. : 0 . 16 mx0024w)............0...........0....0..00...45 17h SEM photomicrograph of detrital K-feldspar (a) grain rimmed with small, jagged overgrowths. (B) is a close-up of these small (2-10 um) euhedral overgrowths. Sample # NH-3-11. Tic mark = 10 um. . .46 X Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 18 19 20 21 22 23 24 25 26 27 28 29 Complex assemblage of sericite, illite and chlorite pore-fillings. sample # NH-3-22. (Frame dim.: 1.0 mx105m,00.......0..........00......000......047 Radial authigenic pore-lining clay (illite-smectite ?) crust. Sample # NH-3-1. (Frame dim.: 0.4 mm x 0.6M)...0...............0..............0.......047 A) Laumontite as a pore-filling and replacement (arrows) of plagioclase feldspar. B) is a cross polar of A. Sample # NH-3-10. (Frame dim.: 1.0 mm x 1.5 mm)48 Calcite replacement along twinning planes of plagioclase feldspar. Notice the pore-filling calcite cement. Sample # NH-2-14 . (Frame dim. : 1. 0 Calcite pseudomorph (P) with ring of hematite which represents the original coatings on the replaced feldspar grain. Sample # NH-2-19 . (Frame dim. : 2 . 5 Deformed mica (biotite) surrounded by pore-filling calcite cement. Sample # NH-2-14. (Frame dim.: 1.0 mx1.5m,...0.......0....0....0...0............51 Hematite-stained clay (H) coats detrital feldspar in fluvial sandstone of the East Berlin Formation. Sample # EB-1-10. (Frame dim. : 0.4 mm x 0.6 mm) . . .56 Sutured contact between quartz grains caused by pressure solution. Sample # EB-l-lo. (Frame dim.: 0.4mx006mm>0....000.000.000.0000000000000000056 A microstylolitic solution seam near contact surface between coarse- and f inc-grained sandstone in the East Berlin Formation. Sample # EB-l-ll . (Frame dim.: 2.5mmx3.8mm)............................57 Summary of the paragenetic sequence in the New Haven Atkose (Stop 4).0.......0....0......0.............67 Summary of the paragenetic sequence in the New Haven ”kose (Stop 3)......0........0......0..........0.68 Summary of the paragenetic sequence in the New Haven Atkose (Stop 2)0.0.0.00000...0......00...0....00.069 xi Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 30 31 32 33 34 35 36 37 38 39 4O 41 Summary of the paragenetic sequence in the East mrlinpomtion (stop1).........................70 X-ray diffraction traces of the <2 um fraction of New Haven Arkose. Sample NH-4-6 shows chlorite and illite-smectitepattems...0.00000000000000000000082 x-ray diffraction patterns of the <2 um fraction of the New Haven Arkose. Sample NH-3-20 shows illite- smectite interlayer................ ..... ..........85 XRD pattern of the <2 um of sample EB-1-2 , a floodplain red sandstone in the East Berlin Formation. Sample contains illite and chlorite. . . . 87 XRD pattern of the <2 um of sample EB-1-2 of the East Berlin Formation. Sample contains illite and minor amount of kaolinite...... .......... .........88 XRD pattern of the <2 um fraction of sample EB-l- 25, East Berlin Formation. Sample contains chloritedvermiculite:interlayers..................90 XRD pattern of the <2 um of sample EB-1-13 , East Berlin Formation. Sample contains well-crystallized illiteandChlorite.....000.00.................0..91 XRD traces of the <2 pm of sample EB-l-19 , East Berlin Formation. It contains chlorite-smectite interlayer000000000.00000...0.........000.0.0000.093 XRD pattern for the <2 pm of sample EB-1-15, East Berlin Formation. Sample contains illite and expandable chlorite phases........................94 XRD pattern of the <2 um fraction. Black shale of the East Berlin Formation. Sample contains illite, smectite, and traces of kaolinite. . . . . . . . . . . . . . . . .96 Plot of the % chlorite vs. % K-feldspar for the three stops of the New Haven Formation. . . . . . . . . . . 104 Thin-section photomicrograph of partly albitized K- feldspar grain riddled with abundant inclusions. Sample # NH-3-16. (Frame dim. : 2.5 mm x 3.8 mm) . . .114 xii Figure Figure Figure Figure Figure Figure Figure Figure Figure 42 43 44 45 46 47 48 49 50 Photomicrograph of albitized K-feldspar grain showing blocky to tabular sector extension (chessboard albite) patterns. Sample # NH-3-16. (Frame dim.: 2.5mmx 3.8mm)116 Photomicrograph showing uniform extinction of albitized K-feldspar grain. Surrounding grains are mostly of quartz . Sample # NH-3-16. (Frame dim. : 1.0mmx1.5mm).................................116 Corresponding BSEI (A and B) of the albitized grain in Figure (42) revealing albitization features more clearly due to chemical inhomogeneity. B) is the enlarged image of (A). Sample # NH-3-16. Bar scale = 1000 um and 100 pm for A and B respectively. . . .117 Backscattered electron image of albitized K- feldspar. Notice that albite is dark gray and K- feldspar is light gray. Surrounding grains showing uniform dark gray shades are quartz. Sample # NH- 3-19. Barscale=100um.........................118 EDS pattern showing the elemental chemical composition of the albitized grain in figure (45). A) EDS pattern of albite (dark gray) and for K- feldspar (light gray), (B). Sample # NH-3-19.. . . .119 Photomicrograph showing albitized K-feldspar grain resembling chessboard albite. Blocky and tabular dark gray patches are albite (Alb) while light gray -yellow areas represent relict K-feldspar (Ksp) . Sample # NH-3-15. (Frame dim. : 2.5 mm x 3.8 mm) . . .121 SEM photomicrograph of type 1 albite showing delicate skeletal structures of a leached K-feldspar grains. Sample # EB-1-12. Bar scale a 100 um. . . .121 Enlarged SEM view showing parallel oriented albite crystals (arrows) within K-feldspar host. Sample #NH-3-360 Ticmarkzloum..0.0.00.0...00000000122 SEM photomicrograph of type 2 albitization showing no intracrystalline dissolution porosity. Sample # “-4-2. Tic mark: 100 um....0....0..0...0...0122 xiii Figure Figure Figure Figure Figure Figure Figure Figure Figure 51 SEM photomicrograph showing pseudomorphic replacement of K-feldspar by blocky albite crystals. Notice the preferred orientation of albite along cleavage planes of parent K-feldspar. Sample # NH- 2-6. Ticmark= 100 um124 52 SEM photomicrograph showing detrital feldspar pseudomorph formed by continuous growth of individual albites. Sample # NH-2-6. Tic mark = 10um................0.....0...............0.00.0124 53 ESE image showing a detrital plagioclase grain (light gray) replaced by albite (dark gray) . Notice the different range of gray tones within the grain. Also, notice that albitization starts along microfractures in the detrital plagioclase. Sample # NH-3-16. Bar sca1e= 100 um....................126 54a Ab Or An ternary plot showing the compositional variation of microprobe analyses (Appendix A) of albitized K-feldspar in the Hartford Basin (modified after Deer, Howie, and Zussman: 1963) . . . . . . . . . . . . 128 54b Or Ab An ternary plot showing compositional variations of the microprobe analyses (Appendix B) of detrital plagioclase feldspar in the Hartford agin.0000000..0.0...................0.....0..0.0129 54:: Or Ab An ternary plot showing the compositional variations of probe analyses (Appendix C) of rel ict K-feldspar in the Hartford Basin. . . . . . . . . . . . . . . . . 130 55 Plot of the percent albitized K-feldspar grains (from point counts data) versus depth in the New Haven and the East Berlin Formations. Trend showing increase in albitization with increase in depth............................................134 56 Variation in the dolomite versus chlorite in the sediments of the East Berlin Formation. . . . . . . . . . . 144 57 Grain-coating chlorite rimming around detrital grains and in between grain contact (arrows). Notice a later generation of chlorite cement within the voids. Sample # EB-l-25. (Frame dim.: 1.0 mm x 1.5M)0....0......0..............0...0.00.0...00146 xiv Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 58 59 60 61 62 63 64 65 66 67 68 Pore-lining chlorite covering different detrital grains, but absent at grain contacts (arrows) . Sample # NH-4-6. (Frame dim. : 1.0 mm x 1.5 mm) . . .146 SEM photomicrograph showing crenulated plates of chlorite-vermiculite grain-coatings of detrital framework. Sample # EB-1-25. Tic mark = 100 um. . .148 SEM photomicrograph showing euhedral rosette-like platelets lined on a detrital plagioclase feldspar grain and growing towards the pore. Sample # NH- 4-2. Ticmark=10 um............................149 Photomicrograph of multiple pore-lining chlorite superposed one on tap of the other. Sample # NH- 4-1. (Frame dim.: 0.4 mmx 0.6 mm)...............149 SEM photomicrograph showing pore-filling chlorite cement. Sample # NH-4-1. Tic mark = 10 um. . . . . .151 EDS pattern showing relatively Mg-rich chlorite at Stop (4)e sample#NH“4'6...........o...........152 XRD pattern of the authigenic grain-coating clay assemblage showing the marked differences in intensity of the (001) and (002) basal reflections of chlorite and the slight shift in spacing of the (001) reflection after heating. Illite/smectite (I/S) is also recorded. Sample # NH-4-1. . . . . . . . .153 XRD pattern of type IIb chlorite polytype, New Haven Arkose. Notice the intensity of 2 . 59 and 2 . 55 Angstrom reflections. Sample # EB-l-l7 . . . . . . . . . . 159 XRD pattern of type Ib chlorite polytype. Notice the characteristic reflections at 2 . 51 and 2 . 15 ADQStI'OIB. sample*"Ii-4-15eeeeeeeeeeeeeeeeeeeeeelsg SEM photomicrograph showing similar morphology between grain-coatings and corrensite. Sample # EB-l-ZSe Ticmark-10um........................163 Photomicrograph showing fan-like terminated clay due to the breakdown of mica. Sample # NH-4-6. (Frame dim.: 0.16mmx 0.24 mm)................-..167 Figure Figure Figure Figure Figure Figure Figure 69 7O 71 72 73 74 75 Photomicrograph laumontite pore-filling cement and replacement of feldspar. Sample # NH-3-10. (Frame dim.: 1.0mmx1.5mm)...........................170 XRD pattern of random powder sample showing the distinctive peaks of laumontite along with illite. sample#NH-B-IOeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee172 EDS spectrum showing characteristic elemental composition of laumontite (Ca, Al, and Si). Sample *NH-3-IOeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee173 XRD pattern of analcime in the Jurassic East Berlin Formation. Notice the presence of chlorite peaks inthissample000...0000000.00.00.00.00....000000177 Correlation of the temperature-dependent mineral assemblages in.Shales, sandstones, and volcanogenic rocks (after Hoffman and Hower, 1979) . . . . . . . . . . . . 182 Approximate pressures and temperatures under which various metamorphic ‘mineral facies form (after Philpotts'1990)eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee184 ACF (Al Ca Fe) plots of common. quartz-bearing mineral assemblages in the 'metamorphic facies. Boundaries and conditions are the same as in Figure 74 (after Philpotts, 1990).......................185 CHAPTER I INTRODUCTION This study is concerned with the clay mineralogy and sandstone diagenesis of the clastic sedimentary red-bed sequence of Lower Mesozoic age located in the Hartford Basin, Connecticut Valley and generally referred to as the Newark Supergroup (Van Houten, 1977: Olsen, 1978) . These sedimentary rocks consist of alluvial-fan, fluvial and lacustrine deposits interlayered with extrusive basalt flows and intrusive basalt dikes and sills (Hubert gt gl., 1978). The Hartford Basin is one of the most studied Mesozoic closed basins of eastern North America (Krynine, 1950: Hubert gt g1., 1978: Hubert gt g1., 1982). The Hartford Basin is a part of a linear system of fault-bounded basins extending for a distance of 2000 km along the eastern continental margin of North America (Figure 1). These basins developed during rifting which formed the Atlantic Ocean (Van Houten, 1977: Austin gt g1., 1980). The Newark Supergroup of sedimentary rocks within the Connecticut Valley forms a homocline that generally dips east and strikes north-south (Krynine, 1950; Van Houten, 1977). The Hartford Basin is a half-graben about 150 km long and up to 30 km across. The strata dip uniformly toward the eastern edge of the basin, where there is a complex west-dipping normal fault system bounding the basin on the east. The basin is bounded to the west by pre-Triassic metamorphic basement rocks. These faults separate the ~ EXPOSED coveneo Figure 1. Basins of the Newark Supergroup along eastern North America (after Van Houten, 1977). 3 uplifted Lower Paleozoic metamorphic rocks to the east from the down-dropped valley (Hubert gt g1., 1978). The Hartford Basin contains sedimentary and volcanic igneous rocks of Late Triassic and Early Jurassic age (Krynine, 1950). These rocks have a maximum thickness of about 4 km (Hubert gt 11., 1978). The Triassic strata of the Hartford Basin were subdivided into seven main formations of the Meriden Group: from bottom to top: New Haven Arkose, Talcott Formation, Shuttle Meadow Formation, Holyoke Formation, East Berlin Formation, Hampden Formation, and Portland Formation (Rodgers, 1968: Sanders, 1970). This classification is based upon lithology. The Hampden, Holyoke, and Talcott Formations are basalt flows: the other four units consist of terrigenous clastic sedimentary rocks. The stratigraphic framework of the Connecticut Valley is depicted in Figure 2. PALEOGEOGRAPHIC HISTORY In its pre-continental drift position, the rift valley was located in the tropics at about 15 degrees north paleolatitude (Hubert gt gl., 1978). The valley was floored by multiply-deformed, high grade metamorphic rocks of Early Paleozoic age. The initial sedimentary fill was the 2000 m New Haven Arkose of Late Triassic-Early Jurassic age (Krynine, 1950). Rivers flowed from the eastern highlands, depositing conglomerate and sandstone in alluvial fans along the base of a.fault-bounded escarpment. The rivers coursed south-west, ERG 44 _ _..fi_‘___ _+‘_____~m__’_.-—HM KM 4 ._ Q (I) ‘4’ —— PORTLAND FM. I ‘ D .1 3 5 ”Hm/HAMPDEN BASALT ; ——EAST BERLIN FM. S —" HOLYOKE BASALT “-‘SHUTTLE MEADOW 2 __l___ H"\ FM. 1 TALCOTT BASALT 2 0) (I) S . a: ——NEW HAVEN FM. 1 r— G I.“ O. O. D o 1 Figure 2 . The stratigraphic framework of the Upper Triassic and Lower Jurassic in the Hartford Basin, Central Connecticut (Hubert gt a]... 1976). ‘ch 5 constructing an alluvial-plain sequence of braided-river sandstone and pebbly sandstone and floodplain red mudstone (Smith, 1971 and 1972). Caliche paleosol profiles are abundant, reflecting a paleoclimate dominated by tropical semi-aridity with seasonal precipitation of about 100 to 500 mm (Hubert gt 31., 1978). In Early Jurassic time, tholeiitic basaltic magma rose along deep crustal fractures to form the fissure flows and interbedded volcanic agglomerate of the 65 m Talcott Basalt. The flows substantially lowered the gradient of the valley floor (Hubert gt 11., 1978). The overlying 100m Shuttle Meadow Formation is dominated by playa and perennial lakes that existed during intervals of relatively increased precipitation (Hubert gt g" 1982) . The lacustrine rocks include laminated dolomite-gray mudstone, gray sandstone, limestone, and thin, evenly bedded redbeds. Thin fluvial sequences of redbeds separate the lacustrine rocks. Dinosaur tracks are found in the mudstones of the Shuttle Meadow Formation, as well as in the East Berlin and Portland Formations (Hubert gt g1., 1978). Volcanic activity then resumed with huge outpourings along fissures of highly fluid basalt that form the 100 m HOlyoke Basalt. The lava flows were succeeded by the lacustrine and fluvial strata of the 170 m East Berlin Formation. One third of the formation consists of lacustrine CYcles of gray mudstone and sandstone-black shale-gray lIltldstone and sandstone. The lakes were perennial with ‘a-aO av’we - v -=".‘a c‘lib - ..-I .‘ x00:|5 0 ~ I . Pfi‘p uhw’u. . I 1 “.5 “in! 1 4 t1:' ‘ J R. :1. A a. “‘=Vh‘ I W.~‘621 - 'n . it: s: v. 0‘, NA 6 alkaline hard water (Hubert gt g1. , 1978) . Later, thin lava flows spread from fissures and vents located southwest of central Connecticut to form the 60 m Hampden Basalt. The overlying Portland Arkose is a 1200 m sequence consisting mostly of braided-river sandstone and floodplain red mudstone. Alluvial fans continued to coalesce along the front of the eastern highlands. Thin lacustrine beds of gray mudstone and sandstone are present in the lower half of the Portland Arkose (Hubert gt g1., 1978) . The strata in the rift valley have been intruded by basalt dikes and sills, tilted to the southeast, locally folded and faulted, and subjected to erosion (Krynine, 1950: Hubert gt gl., 1978) . When Recently, with the advent of plate tectonic theory and Paleomagnetic research, the geographic position of the Connecticut Valley during Late Triassic and Early Jurassic time has been tentatively placed between 10 to 25 degree north Of the paleoequator (Hallam, 1971: Philippe and Forsyth, 1972). With this information and numerous lacustrine Paleocurrent and slump fold measurements Hubert gt g1. (1976) , in their sedimentologic study of the East Berlin Formation, Proposed that the valley was under the influence of a Predominant northwest paleowind. In a later paper, Hubert (1977) suggested that the northwesterly winds blowing over Outcroppings of Paleozoic carbonate rocks to the west of the p‘ :0 seat .. v! I flanker . .. 4.0:. . 60.1.. .« ...u.. 36...: 0 l":. a...‘. 'l (M. “‘ ecu 'e ‘ ‘ca- ""vm. 7 rift valley provided calcareous dust for the formation of caliche deposits in the New Haven Arkose (Late Triassic-Early Jurassic). The research conducted by Hubert gt g1. , (1976) provides detailed interpretations of the fluvial and lacustrine sedimentary depositional environments of the East Berlin Formation. They conclude that the sediments were deposited in fluvial and lacustrine-paludal environments (Figure 3). Stream-channel sandstone, floodplain red mudstone and lacustrine red sandstone and siltstone were deposited under oxidizing and alkaline conditions. The black shale and gray mudstone and sandstone were laid down in large, perennial, oligomictic lakes, which at times extended over wide areas of the rift valley. DESCRIPTION OF THE STUDIED FORMATIONS Previous sedimentologic work by Krynine (1950), Sanders (1970) and Hubert gt g1. (1978) has yielded a stratigraphic framework, petrographic history and a broad understanding about depositional environment. Krynine's work emphasized the IMineralogy and petrology of the sedimentary rocks and the climatic significance of the red color of the sediments. Sanders (1970) revised the stratigraphy and developed a lacustrine model of deposition for the fine-grained sediments of the East Berlin Formation. Hubert gt :1. (1978) have summarized many of the currently accepted interpretations of depositional environments for the different formations found grill legend 0 OUTCROP I-s \ I Q ,‘ rmporwnr LAKE q. RIPPLE CRESTS Ill 40 MARSH 5/ ALLUVIAL rm pmssu' E or‘\‘ f BASIN -\':: POMPERAUG LAKE .& GNIER ; or lgijéfiif FMUflueflflLi”' f / / li'igure 3. Paleogeographic map showing various depositional environments of the East Berlin Fm. Paleowind direction was determined from paleocurrent readings in shallow water and shoreline sandstone of temporary and perennial lakes (Hubert gt gl., 1976). 1‘. 0‘: on” 0‘“ “.0: b. lei-I." ' “~‘-e\ Eizse 6-5. :3" a . ":~3‘E: I ‘-‘ 4‘1.‘ - V F "vi t. A in the Hartford Basin. Four accessible exposures representing East Berlin and New Haven Arkose Formations were selected for this study (stops 1-4, Figure 4a). An idealized cross-section of the Hartford Basin (A-A' , perpendicular to structural strike) illustrates the approximate geographic and stratigraphic location of stops 2-4, showing that stop 3 of the New Haven Arkose is stratigraphically higher than stop 2 and 4 (Figure 4b) . The following is a description of the stratigraphy and sedimentation of both formations. w v se A large outcrop of about 72 m of the New Haven Arkose is exposed along the North Haven section, Connecticut (stop 2, Figure 4). The rocks of the New Haven Arkose contain an alluvial Plain sequence of channel pale red sandstones and conglomerate interbedded with floodplain red sandy mudstone (Figure 5a) . Cross-bed sets of pebbly sandstone commonly exceed 0.5 m in thickness, suggesting avalanche deposition on prograding Slipfaces of braid bars (Hubert gt g1., 1978) . At this stop, numerous caliche profiles were observed, Produced by paleosol calcification of channel sand and floodplain mud. A combination of a slow sedimentation rate with a paleoclimate dominated by semi-aridity generated about 35 caliche horizons in the 72 m section. Hubert (1977) discovered widely distributed caliche paleosol profiles in 10 .maoum onwamaom Moon on» no sawuoooH on» mcfi3onm usoHuoocsou Hmuucoo no Qua Hanaooaooo ov mucosa ““0232 no...“ @ Q§§Qh Q§ths §§Qq \l‘h kJadm I\\.|u / hadhzou o.xmJOI 0.355.. 29258 $26.. 23%;. 53 h4mm 3oz on» no maoum owns» on» no cofiuwmom oanmmumfiuouum o>Huonu on» mcwzonm cfimmm ououuumm on» no A175 cowuoomnmmouo Dauoamcom av muoofim . 3:: . Ad ad sumo—am umuua 33305 co>mm cuuoz .ov ousou 98.1.. m noun no omoxud cm>mx 3oz as» no cowuoom oousmaoz on «Macaw 12 4 . a no... 9.3.305 20 3.28 on... v N uzenoaa 823. 8.. 5.238. I .. . .. “‘53 us 3 is .3uo.80¢u n oi 83 uzfit 5.3 3:85... 3.. 31 ~22...on 58! co 33.3338 8.. 3! Wu c o 1 20.83 359m: m o h a «.1 m a .. . ._._ E... I o— 1 M4,..- .u l -. : luv»... w E. \ . — «a 91 E m n— E .u. 3 l ‘I' 1 II- _ n E .. g z 2 cu... III. a I . a E_ ... 2 - g. m an i . 8 . 5-73 ' DO.‘ .3 5' IOU: 'U‘n s“ l . V 3‘ :0‘.. $5.}, r» .;'.c ~.lU “It. ."~ ffiln' ‘\ g. H _-—q _ _. . \i . _—~ 13 braided-stream sandstone and overbank mudstone in this section of the New Haven Arkose. Caliche profiles were not observed in the other studied outcrops of the New Haven Arkose (Stops 3 and 4, Figure 4). The alluvial plain sequence was deposited by braided rivers as evident by the presence of a complex pattern of plane beds, and planar tangential cross-beds overlain by pebbly sandstone and conglomerate (Hubert gt al., 1978). The rivers were ephemeral, with a large fluctuations in water discharge, shallow, floored by bars and channels, of high gradient and low sinuosity, and with a coarse bedload of pebbly sand (Smith, 1971 and 1972). The New Haven Arkose exposed in an old abandoned quarry (currently the Hamden Dump) consists mainly of floodplain facies that are cut by a dolerite dike, about 3 meters thick (stop 3, Figures 4 and 5b). These rocks consist of coarse- grained, thick-bedded sandstone and interbedded, thin-bedded siltstone. The sandstones are coarse-grained, arkosic, poorly sorted and pebbly. An outcrop of proximal alluvial fan facies of the basal New Haven Arkose at Woodbridge, Connecticut (stop 4, Figures 4 and 5b) shows that.these rocks unconformably overly the pre- Triassic Milford Chlorite Schist. The New Haven Arkose consists of interlayered and intertonguing cobble- and pebble- conglomerate and green, epidotic (detrital) , arkosic sandstone. Both the conglomerate and sandstone are poorly 8Orted. Bedding is extremely crude, roughly parallel to the 14 . v 0cm n Govm um mmoghd Hume/mm 302 03H MO mCOHHOTm Owhflmmmz Qm Gufimfim 0..” o d 9 J :28 25.5 28:2 5 ..Ad u..." u \ I co. 0 M 2.9353 3.9:- 0829 3080 E . .. m e 4 ...lmM v . 0000 no n 3:95:25 89850380 033.“ on. 0330 a . N V. .n a .nn. 6 o . v mOFm n . 3” a l1 s 3.6 3:28 @ , 4 n. .... 2.23% and l n .. 2.98:8 38s.: bosom R: 0?.— E o i: . .. ~— 4 0356 2.93:3 £83: com a e no.5 m up; ~28me : Z. on. in? basal :.~‘V' ~~I c.‘ a: ‘\ H5: ....‘ ~..:‘ ‘1 I; () (I! 15 basal unconformity. The conglomerate shows two distinct size composition associations, phyllitic cobbles and quartzo-feldspathic pebbles, suggesting two sources for the basal New Haven Arkose. The cobble fraction was derived locally from the Milford Chlorite Schist, whereas the pebble fraction and the sand fraction were probably derived from a more distant source (Klein, 1968). The mixed sorting of the rocks, the sand-grain angularity, the poor stratification, and the mixed population of the conglomerates support the proximal alluvial fan facies interpretation. MW About 62 m of the upper part of the East Berlin Formation, plus the contact with the overlying 60 m Hampden Basalt, are exposed near Cromwell, Connecticut (stop 1, Figure 4) . The rock types are mainly gray mudstone, black shale, and gray sandstone (perennial lakes); red mudstone (floodplains); evenly bedded red sandstone and siltstone with abundant ripple marks (shallow oxidized lakes) ; and pale-red channel sandstone (river channels). The black shale and gray mudstone record perennial lakes that existed from time to time in the rift valley (Krynine, 1950; Klein, 1969: Hubert g3; a1", 1976) . At some localities in central Connecticut these beds contain different groups of “‘0’, Wu..l ~v‘\ '1‘ae 16 fossil fish (Hubert gt g1., 1978). Olsen (1986) believes that the sediments of the early Mesozoic Newark Supergroup consist largely of sedimentary cycles produced by the rise and fall of very large lakes that responded to periodic climate changes controlled by variations in the earth's orbit. The recent study by Demicco and Kordesch (1986) provides a detailed sedimentary facies classification of the East Berlin Formation. They conclude that the mudstone facies are cyclic and record long periods of dry playa mudflat aggradation punctuated by the rapid expansion and contraction of perennial lakes. On the other hand, the sandy facies occur as single sedimentation units that record sheet floods across ephemeral floodplains. I agree with Hubert gt gt. (1978) interpretation of the mudstone facies cycles as representing climatic changes from wet-dry periods. The black shale and gray mudstone form symmetrical cycles, mostly 2 to 7 m in thickness (Figure 6). The center of each cycle is pyritic black shale that accumulated in the deeper, more central parts of a lake. .Above and below is gray mudstone with structures indicative of shallower water, including dolomite concretions, ripple marks, mud cracks, and dinosaur footprints. Ferroan dolomite laminae are present in some of the black shale and gray mudstone. The terrigenous grains in these drab-colored rocks were originally coated with limonite stains which were removed in solution, evidently as Organic-ferrous iron complexes (Hubert gt a1., 1978). 17 uuonsm nouns omauwooev Ha .Amhma .coaumauom cflauom ummm on» c« macho ome Hmficcmumm may no coHuoon Dacmoumauouum .w mus—3m ..Am MM msfiouu .H noun .828: 332.. a «a» .35..» m «82% ”53.66 a £53.. 83s .8 82.. 828.8 E .8458 28”."; one 2.2.x 83.: “:28? ans D . 3338 55:8 583 fix was E 2m>m>m 45):...“— uzounozfi 38 m =83! .26 N g... 63.. I mux<4 432sz nscq m20>m§ om: 9636 81 .353 unit: 36:363.» .3236qu exotewk mtg—.335 >m><40 >58 «.536 g: v.33. 1:3.» was}: axioqoo titux 95.59.! >38 .3553 92:38 $653.4 was.» 29.5 9.63.6 gt .huhhthtcubuh w-Stixq hksicug i‘gthk g >55 95$:th 5.69% .3636 99‘ .353 .3“ «Secures.» .3333 3639‘ 9555.0 >u><40 >3 “86.386 3.234 mac—.85” at...) 0850:! ac “NODUZOU .J‘KIII P; z. 05-D.| “A m: «I 1 A‘H‘ u‘. ‘ .; P ~e b.“ 5"" i N D. I}: -~. I' u. a .5... 18 Thin beds of gray, fine- to very fine-grained sandstone occur in some of the gray mudstones, forming intervals of thin-bedded sandstone and gray mudstone. Most of the sandstone is horizontally laminated, but there are some planar cross-beds. The sandstones are near the top and bottom of the cycles, implying accumulation in shallow water near the lake shores. The gray mudstone-black shale-gray mudstone symmetrical cycles require expansion and contraction of perennial lakes (Hubert 93; 31., 1978)- The Early Jurassic palynoflorule in the East Berlin Formation comprises more than 90% My; pollen from conifers that lived most abundantly on sandy areas of the alluvial fans and highlands (Cornet and Traverse, 1975). The rarity of xeromorphic cuticular adaptations in the flora, plus the many kinds of cryptograms based on spore diversity, suggest to these authors a humid climate with a short dry season. The palynoflorule is found in lacustrine gray mudstone and black shale, recording periods of increased rainfall that coincided with the existence of large perennial lakes. The paleoclimate of the Hartford Basin during Early Mesozoic time has been variously described as: glacial (Dana 1883), arid to semi-arid (Hubert, 1977), and warm and humid or seasonally wet (Krynine, 1950; Cornet and Traverse, 1975; Hubert g; 31., 1976) . The two latter hypotheses are considered viable on the bases of fossil as well as petrographic, mineralogical, and sedimentological evidence. Start tale 1 :ccxre 5:: th alterna . l I, n ‘ f‘o iaal l‘jirogt ‘ I i a \“‘ bed lCltt 13:;35 \A‘a; . Uh.“ ~ t 41 re ”‘v “MESS '15-» I'. ."A “~ng ‘ . § . ,“ t“as l9 Hubert g; 51., (1978) suggest that no one climate fits the whole time span during which deposition in the rift valley occurred. A semiarid (wet/dry) climate appears characteristic for the Upper Triassic (New Haven .Arkose), whereas an alternating' subhumid. (wet/dry)-semiarid. (wet/dry) climate prevailed in Lower Jurassic (East Berlin) time. Suchecki gt a1. (1988) studied. the isotopic imprint. of’ climate and hydrogeochemistry on the strata of the Hartford and Fundy basins. They concluded that in the Hartford Basin, caliche calcites in fluvial mudstones and sandstones have isotopic compositions that reflect paleosol processes during climatic conditions that varied from warm and dry in Late Triassic time to relatively cooler and probably wetter in the Early Jurassic. PREVIOUS WORK AND OBJECTIVES ‘Various theories addressing‘theldepositional environment of the sedimentary rocks in the Connecticut rift valley have been proposed, since Sir Charles Lyell (1845) first suggested that the sediments were deposited in a large tidal estuary similar to the Bay of Fundy. The facies interpretations of Krynine (1950), Hubert g; a1. (1976 and 1978) were discussed early in this chapter. In spite of considerable tectonic, structural, stratigraphic, and sedimentologic research carried out on the Triassic-Jurassic rocks of the Hartford Basin (Connecticut rift valley), very little is known about the mineralogy, ...' ,. '9 eh I H 20 petrology and diagenesis of these rocks. Particularly interesting problems are: the variations in the paleoclimate and its effect on diagenesis of the various detrital mineral assemblages; the extent of sediment diagenesis; the influence of the hot basalt flows on the underlying sediments; and the origin and paragenesis of certain authigenic minerals. Few sedimentological studies of the Triassic rift basins have made extensive use of thin-section petrography. Krynine (1950) studied the petrography, stratigraphy and origin of the Triassic sedimentary rocks of Connecticut. He included detailed, somewhat exhaustive, petrographic descriptions and characterizations of the sediments. In his stratigraphic classification, the East Berlin Formation was incorporated as a part of the Meriden Formation, a term no longer used. He specified three petrographic and textural components: 1) a coarse-grained (sandy or pebbly) arkose; 2) a fine-grained detrital clayey matrix; and 3) a chemical carbonate cement (generally calcite). Texturally, Krynine mentioned that the Triassic rocks of Connecticut are made up of conglomerates, sandstones, and shales of different degrees of rounding. These rocks are extremely coarse-grained and very poorly sorted. The mineralogy of the rocks allowed him to conclude that there was no significant contribution of sediments from sources west of the main basin's eastern border fault. Krynine was able to decipher the sequence of erosion in the source area by demonstrating an inverted metamorphic-to- granitic compositional sequence within the sediments. Such 21 vertical distributions allowed him to subdivide some of the formations, but to date, these divisions have had little application to sedimentological problems (Lorenz, 1988). Krynine also used his suite of over twenty trace or heavy 'minerals for purposes of east-west stratigraphic correlation, documenting that the bulk of the sediments in the Pomperaug outlier (west of the Hartford Basin; basin 12 on Figure 1) correlate with the New Haven Arkose. Another important use of the heavy-mineral study was in documenting primarily east- to-west paleodrainage. The heavy mineral grains are subangular to subrounded, reflecting the few tens of kilometers of stream transport from the source highlands east of the rift valley (Hubert and Reed, 1978). Weddle and Hubert (1983), according to Lorenz (1988), combined the distribution of petrographic characteristics of rocks with.paleoflow'patterns and facies distributions. They showed that, although Triassic sediments probably extended beyond their present limits in the Newark and Hartford/Deerfield basins, the two general areas were not connected as a continuous, broad area of subsidence and sedimentation. Vetter and Brakenridge (1986) tested.the paleogeographic reconstructions derived from cross-bedding by means of petrographic techniques. Their study is an attempt to produce a framework for the subsurface stratigraphic correlation of petrographic horizons in drill holes. ‘A-. “:5. 133: “A ‘u‘ 22 Hubert 93 a1. (1976) discussed the mineralogy of the East Berlin Formation and suggested that the evaporation of the perennial lake led to the formation of dolomite concretions and cement. The climate was wet-tropical with a pronounced dry season. Illite was found to occur abundantly in the red and gray mudstone and black shale. Corrensite in the gray mudstones of the perennial lake cycle sequences may have formed in shallow pools where waters were enriched in dissolved salts. April (1980) reported the presence of a regularly interstratified chlorite/vermiculite (corrensite) in red beds of the East Berlin Formation. The mineral is restricted to a zone of contact metamorphosed strata adjacent to and underlying the Hampden Basalt. Trioctahedral smectite and regularly interstratified chlorite/smectite are restricted to black shale and gray mudstone deposited in alkaline, perennial lakes of the East Berlin Formation (April, 1981). Vergo and April (1982) also reported the presence of an interstratified chlorite/smectite in contact aureoles produced by tholeiitic, basaltic intrusives at West Rock in New Haven Connecticut. Host of the aforementioned petrographic studies emphasized provenance or stratigraphic correlation. Few' petrographic studies have addressed diagenetic processes in the Hartford Basin. Heald (1956) studied the cementation of the Triassic arkoses in Connecticut and Massachusetts away from and near the eastern border fault and intrusives. He concluded that large amounts of cryptocrystalline quartz, 23 potash feldspar, and sericite were deposited in the sediments along the border fault, while microcrystalline secondary albite is the abundant cement type in the arkoses near intrusives. Hubert and Reed (1978) used thin-section data, by observing the textural and diagenetic relationships between detrital grains and the authigenic cements, to document the source of red coloration and diagenetic sequence in the Early Jurassic rocks of the East Berlin Formation. They concluded that the red coloration of the sandstones and mudstones is mainly due to hematite and this red color is authigenic. Hematite was produced by different post-depositional diagenetic processes including: aging of limonite; intrastratal solution of Fe-silicate grains: oxidation of magnetite: and replacement of Fe-silicate grains by dolomite cement. Hubert and Reed (1978) also noted that the proportion of quartz and feldspar among the grains are statistically similar in both of the fluvial and lacustrine environments, as are the authigenic mineral cements and their proportions. Plagioclase grains dominate over K-spar in a 7:1 ratio in the arkoses of the lacustrine deposits (Hubert and Reed, 1978). Microcline is more abundant than sodic plagioclase feldspar in the fluvial deposits (Heald, 1956). Recently, Hubert and MBriney (1988) studied the cementation and paragenetic sequence of the Hartford Basin sediments in Connecticut and Massachusetts. They conclude 'that albite overgrowths occur in all formations, environments 24 and parts of the basin. This. dissertation. began. as an. attempt to test the hypothesis that the clay mineral diagenesis in the sandstones and mudstones of the East Berlin Formation and the New Haven Arkose has influenced the evolution of sandstone reservoir properties. After work had begun, the lack of petrographic evidence on porosity evolution and, on the other hand, the enormity of a detailed mineralogical and diagenetic investigation soon became apparent. Research then focused on the diagenesis and mineralogy of the East Berlin Formation and the New' Haven .Arkose, which, proved to display‘ a great diversity in terms of diagenetic alterations and clay-mineral assemblages. The investigation of both paleoclimatically different formations eventually led to a detailed study of the paragenesis and origin of authigenic, detrital, and clay mineral assemblages. The reader should be aware, however, that the regional results and implications are by no means conclusive. They should be regarded as stepping stones for future detailed investigations in this and other basins. CHAPTER 2 SAMPLING AND ANALYTICAL ”T3008 SAMPLE COLLECTION AND LOCALITIES A total of 105 samples were collected from 4 localities in Connecticut. Samples were obtained from the New Haven Arkose and the East Berlin Formation. Locations of the sampling sites are shown in Figure 4. Twenty-eight samples were collected from the East Berlin Formation (stop 1, Figure 6) near Cromwella These rocks are exposed.along the excavated but unpaved access roads of the interchange between I-91 and route 9 in Cromwell, Connecticut (Figure 6). Sixty-nine samples were collected from three outcrops of the New Haven Arkose. Thirty-five samples were collected from the large exposure of the New Haven Arkose along route 40 (stop 2,. Figure 5a) in North Haven, Connecticut. Thirty-six samples of New Haven Arkose were collected from an exposure near a Hampden basalt intrusion (stop 3, Figure 5b) in the Hamden dump. Finally, six samples of the basal New Haven Arkose were collected from a small outcrop behind buildings of the Amity Shopping Center (stop 4, Figure 5b) , Woodbridge, Connecticut. PETROGRAPHIC THIN SECTIONS Ninety-five thin sections were prepared from all rock types selected from the East Berlin and New Haven Arkose Formations. Hand samples were cut into chips, and blue dyed epoxy was vacuum impregnated into the pore space. Each chip 25 26 was then ground on a coarse and then fine grinding wheel and then attached to a petrographic slide. Each thin section was ground to 30 microns thickness and coated with immersion oil and a coverslip. Selected feldspar rich-samples were later cleaned with acetone and stained with sodium cobaltinitrite and rhodizonate reagent for the identification of untwinned potash- and plagioclase feldspar respectively, following the method described by Bailey and Stevens (1960). Selected sandstone thin sections were point counted (500 point counts) for the different detrital and authigenic minerals using the "traditional" method discussed by Ingersoll gt al. (1984). Counts were made by using the microscope's medium magnification power (field of view = 1.8 mm). Both thin sections and sample chips were carbon coated for the Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) analysis. SEM analysis was performed on a JEOL JSM-35C and JEOL T20-CSI: EDS analysis were made by using a Tracor Northern 2000 and 5000. Selected thin sections were polished and carbon coated for the Electron Microprobe (EM?) and Back Scattered Electron Microscopy (BSEM) analyses. A total of 167 analyses were performed using a cmMECA MBX Automated Electron Microprobe Analyzer (EMPA) equipped with three wavelength dispersive spectrometers and secondary and backscattered electron detectors. The operating conditions for the analyses were an accelerating voltage of 15 kv, 10 nA beam current, and a 3 micron beam diameter. BSEM was performed using a KE four- 27 element solid-state back scattered electron detector. BSEM produces an image in which brightness relates to mean atomic number (Hall and Lloyd, 1981: Pye and Krinsley, 1983; Krinsley, Pye and Kearsley, 1983: Pye and Krinsley, 1984). X-RAY DIFFRACTION AND CLAY PREPARATION TECHNIQUES Approximately 5 grams of rock sample was crushed and ground with a ceramic mortar and pestle. The powder was washed in a 500 ml beaker where deionized water was added. Further disaggregation was accomplished by submerging the beaker into an ultrasonic bath for 5 minutes. The less-than~ two micron fraction was separated by gravity settling in the beaker at 20 degrees celsius using Stokes law for settling. After 3 hours of settling, the top 5 cm of the beaker was transferred by pipeting to a sealable container. If significant flocculation occurred the sample was treated with sodium hexametaphosphate (Calgon) and the fraction was then agitated in the ultrasonic bath for 5 minutes. An oriented specimen mount was then made by the method of Drever (1973) as modified by Keller g; a1. (1986). This involved placing the clay dispersion in a clean cylinder attached by clamp to a porous fritted glass filter overlain by a cellulose ester (0.45 micron filter. A vacuum pump was used to rapidly draw out the liquid, producing an oriented film of clay on the cellulose filter. The untreated clay specimen was then mounted on a glass slide by rolling a glass rod over the filter on to the glass slide. Prior to mounting, 28 treated samples were saturated with 1N KCl or 1N MgCl2 by passing them through the clay fraction. The samples were glycerol-solvated in the same way. Potassium saturated samples were heated to 300'C and 550°C for 1 hour in a furnace. The x-ray radiation used in the Rigaku-Geigerflex CN-2013 was Cult-alpha, run at 35kV and 25 mA. Scanning speeds were 1 degree-2 theta per minute, run at 1K cps. The divergence slit used was 1/6 degrees (2-theta): the receiving slit, 0.3 mm: and the antiscatter slit was 2 degrees (2- theta). The chart speed was 10 millimeters per minute and the time constant used was 2 seconds. CHAPTER 3 PETROGRAPEY The Triassic-Jurassic sediments of the Hartford Basin, Connecticut Valley consist of a mixture of arkosic sandstones and conglomerates, siltstones, red mudstones, black shales, and very subordinate limestones. NEW HAVEN ARKOSE Petrographically, the New Haven Arkose consists of a coarse, very poorly to poorly sorted mixture of angular to subangular quartz and feldspar, together with a little mica set in a red, ferruginous clayey matrix. Generally, these sandstones contain an average of 44% quartz, 37% feldspars, less than 3% rock fragments, and about 2% hematite-stained clay matrix (Table 1). They are classified as arkose according to the classification of Pettijohn g; a1. (1987) to be arkose (Figure 7a). Figure 7b illustrates the distribution of the mean QFR (quartz, feldspar, and rock fragments) values at the four stops. The distribution of quartz, plagioclase, and K-feldspar (QPK) is illustrated in figure 7c. Point counting for the rock fragments component (R) was made using the ”traditional" method as discussed by Ingersoll 35 a1. (1984). 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(STOP 3) I+ NJtFM.§flOP:n 0 E.B.FM. (STOP 1) 80 O O 60 4O 20 V AL 4 y v v v 20 4O 50 80 F Figure 7b QFR.ternary'diagram.of the mean values of percent point counts of the different stops. 36 0 o N. H. FM. (STOP 4) v A N. H. FM. (STOP 3) 90 +0 J + N. H. FM. (STOP 2) 80 $40 0 E. a. mtsmp 1) £9 70 +£21.41; + g + 0 133° + d2. 50 “’0 g I i- ++°-=“ A 0 , 50 ‘9 ,9 .1; 0 +15 40 M ~ A + A .30 4. 20 10 \l V V V A] V \l \l V 10 20 30 40 50 60 70 BO 90 Figure 7c QPK ternary diagram of point count data of the different stops. 37 grains within larger fragments to the category of the individual crystal or grain. The ”traditional" method (QFR, in this study) assigns such sand sized crystals and grains to the category of the larger fragments. However, results of point. counting of rock fragments by‘ both. methods (traditionally or'by the Gazzi-Dickinson method) are expected to be similar in this study, as the Hartford Basin arkoses are low in their rock fragment content of finely crystalline rock fragments. 5529.1 At this outcrop, representing the base of the rift- valley fill sequence, the New Haven Arkose unconformably overlies the Milford Chlorite Schist. The New Haven Arkose consists of poorly sorted arkosic sandstone and conglomerate cemented mainly by authigenic pore-filling chlorites. The conglomerates are pebble and cobble in size. The cobble fraction contains angular and. blade-shaped fragments of epidotic phyllite derived from the underlying Milford Chlorite Schist (Klein, 1969). Accessory cobbles of rounded, milky quartz also occur. The pebble fraction consists almost exclusively of rounded fragments of orthoclase and microcline, milky quartz, and granite pegmatite. The pebbles show better rounding than the cobbles; they are disc-shaped and spheroidal (Figure 8). The sandstones are green, coarse- to very coarse-grained, angular, poorly-sorted, arkosic and epidotic. Sizes range 38 Figure 8. Pebble and cobble conglomerate in epidotic arkosic sandstone matrix of stop 4 of the New Haven Arkose. Notice the unconformity surface between Paleozoic Milford chlorite schist and Upper Triassic New Haven Arkose basal conglomerate. - qumr 39 from 0.6 to 1.4mm. The sandstones contain about 35% monocrystalline quartz, 6% polycrystalline quartz, 15% microcline, 2% orthoclase, 4% plagioclase, 2% rock fragments, 9% opaque minerals and epidote, and 19% chlorite cement (Table 1) . The sandstone is cemented by pore-filling and pore-— lining chlorites (Figure 9). Fracturing of feldspars is prominent in all specimens. Fractures in microcline and plagioclase are filled with late diagenetic hematite-stained chlorite, sericite, and minor amounts of calcite cement (Figures 10 and 11). Deformed mica (Figure 12) suggests compaction due to burial of the New Haven Arkose. Quartz-overgrowth is more common than feldspar- overgrowth. The growths are small, euhedral, and clear rims (Figure 13). SEM shows pyramidally terminated quartz overgrowths on detrital quartz grains (Figure 14). A double hematite line is observed in some of the overgrowths (Figure 15). Partially a1tered.metamorphic rock fragments are noted. Albitization of feldspars, particularly microcline, is prominent in the lower part of the section. Under the optical microscope albitized feldspar grains are characteristically untwinned and mostly riddled with abundant minute brownish inclusions (Figure 16). $122.1 The New Haven Arkose exposed in this abandoned quarry (currently the Hamden dump) consists of sandstones with siltstone interbeds. The sandstones are coarse- to medium- 40 Figure 9. Photomicrograph of pore—lining chlorite. Notice hematite coating of detrital quartz and absence of chlorite at grain contacts. Sample # NH-4-6. (Frame dimensions: 0.4 mm x 0.6 mm) 1,5 ‘ \ "'- Figure 10 Fractured potash feldspar filled with hematite—stained clay. Sample # NH-4-5. (Frame dimensions: 2.5 mm x 3.8 mm) Fi .Figure 11 Minor calcite cement filling fractured feldspar. Notice the optical continuity between fracture and pore-filling calcite. Sample # NH-4-3. (Frame dimensions: 2.5 mm x 3.8 mm) Figure 12 Deformed mica (biotite) during compaction of early cementing material. Sample # NH-4-5. (Frame dim.: 1.0 mm x 1.5 mm) Figure 13 Clear euhedral quartz overgrowths rim detrital quartz grains. Sample # NH-4-3. (Frame dim.: 2.5 mm x 3.8 mm) Figure 14 SEM photomicrograph of pyramidally terminated quartz overgrowths. Sample # NH-4-5. (IN a... hit 43 Figure 15 Double hematite line outlines the boundary between the quartz-overgrowth and the detrital quartz grain. Sample # NH-4-3. (Frame Dim.: 1.0 mm x 1.5 mm) In: J _-- Figure 16 Photomicrograph of partly albitized K- feldspar riddled with abundant minute inclusions. Sample # NH-3-16. (Frame dim.: 2.5 mm x 3.8 mm) 01 CE p; f: 44 grained, angular to subangular, poorly sorted, pebbly and arkosic. Grain size ranges from 0.3 to 0.7mm. Pebbles of milky quartz, granite, schist and gneiss rock fragments are scattered throughout the sandstones. The sandstones consist of about 36% monocrystalline quartz, 4% polycrystalline quartz, 30% microcline, 2% plagioclase, 3% mica (biotite and muscovite), 1% zeolite cement, and 4% hematite-stained chlorite matrix (Table 1). Fracturing and albitization of potash feldspar are common (Chapter 5) . Minor feldspar- and quartz-overgrowth are restricted to samples near the base of the section (Figure 17a). SEM examination shows small euhedral overgrowths partly covering a detrital feldspar grain (Figure 17b). A complex assemblage of clay’minerals including sericite, chlorite, and illite represents the main type of cement in these sandstones (Figure 18). Local pore-lining and pore-filling chlorites (Chapter 6) and illites or mixed-layer illite-smectites were observed in these samples (Figure 19) . A minor amount of calcite is present in these arkoses, but most of it occurs as a replacement of detrital feldspar grains rather than as an interstitial cement. Thin-sections show'that zeolite, mainly laumontite (from XRD analysis; Chapter 7), is optically clear to light yellow in color, low birefringence, with well developed cleavage and undulatory extinction. It occurs as pore-filling cement and partly replaces the feldspar (Figure 20). Laumontite has been fbund only in samples NH-3-9 through NH-3-15 in the lower Figure 17a 45 Clear feldspar overgrowths rim detrital core filled with inclusions. Sample # NH-3-3. (Frame dim.: 0.16 mm x 0.24 mm) 46 (B) Figure 17b SEM photomicrograph of detrital K-feldspar (a) grain rimmed with small, jagged overgrowths. (B) is a close-up of these small (2-10 um) euhedral overgrowths. Sample # NH-3-11. Tic mark = 10 um. Figure 18 Complex assemblage of sericite, illite and chlorite pore-fillings. sample # NH- 3-22. (Frame dim.: 1.0 mm x 1.5 mm) Figure 19 Radial authigenic pore-lining clay (illite-smectite ?) crust. Sample # NH- 3-1. (Frame dim.: 0.4 mm x 0.6 mm) Figure 20 A) replacement feldspar. (Frame dim. 48 (B) (arrows) of B) 1.0 mm x 1.5 mm) Laumontite as a pore-filling and plagioclase is a cross polar of A. Sample # NH-3-10. 49 part of the section. Considerable zeolite occurs in the arkoses in Hampden and northern New Haven but is uncommon in other areas (Heald, 1956). 55.9.9.2 The New Haven Arkose exposed at this outcrop consists of medium- to coarse-grained, angular to subangular, poorly sorted, pebbly, arkosic pale red sandstone and conglomerates with red sandy mudstone interbeds. They range in size between 0.4 and 0.6mm. This arkose contains an average of about 36% monocrystalline quartz, 8% polycrystalline quartz, 17% microcline, 10% plagioclase, 1% opaques (mainly hematite cement), 4% muscovite and biotite, and 2% detrital chlorite (Table 1) . Albitization of potassium feldspars (Chapter 5) as well as fracturing of feldspars are prominent in most of the samples, but diminish near the top of the section. Multiple generations of calcite occur as an interstitial filling, fracture filling, and as a replacement of feldspars (Figure 21) . Feldspars were partially or completely replaced by calcite, as indicated by a ring of hematite within the calcite (Figure 22) . In some specimens a few grains are completely replaced and the remaining grains are unaltered. Pervasive calcite cements were observed in the arkoses of this stop, whereas no calcite cement was observed at the other stops of the New Haven Arkose. The calcite is undeformed; yet 50 Figure 21 Calcite replacement along twinning planes of plagioclase feldspar. Notice the pore-filling calcite cement. Sample # NH-2-14. (Frame dim.: 1.0 mm x 1.5 mm) -V 1" Figure 22 Calcite pseudomorph (P) with ring of hematite which represents the original coatings on the replaced feldspar grain. Sample # NH-2-19. (Frame dim.: 2.5 mm x 3.8 mm) Figure 23 Deformed mica (biotite) surrounded by pore-filling calcite cement. Sample # NH- 2-14. (Frame dim.: 1.0 mm x 1.5 mm) 52 surrounds bent mica and fractured feldspars (Figure 23). Light-green pleochroic detrital chlorite occurs in many arkoses, particularly abundant in specimens near the bottom of the section. Minor amounts of authigenic pore-filling chlorites are present in most of the samples. No quartz- or feldspar-overgrowths have been recorded in the arkoses of this outcrop. I Laumontite was detected in only four samples (NH-2-1 through NH-2-4) near the base of the section. Similar to stop 3, laumontite is present as a pore-filling cement and partially replaces detrital feldspar. EAST BERLIN FORMATION The fluvial and lacustrine sandstones of the East Berlin Formation (stop 1) are arkoses (Figure 7a). The proportion of quartz and feldspar among the grains are similar in both environments, as are the authigenic mineral cements and their proportions. SEER—1 The East Berlin sandstones are medium- to coarse-grained, angular to subangular, moderately to poorly sorted arkoses. Their size ranges between 0.35 and 0.55mm. They consist of about 31% quartz, 8% plagioclase, 6% microcline, 12% calcite cement, 17% hematite-stained clay matrix, 8% dolomite, 6% muscovite and biotite (Table 2). 53 I I I I I I I 4 I I I 44 44 4 4 4 4 44 4I4I4u I I I I I I I 44 I I I I 44 4 44 4 4 44 4I4I4- I I I I I I I 44 I I I I 44 4 4 44 I 44 4I4I44 I I 4 I I I 4 4 I 4 4 44 44 4 4 4 I 44 4I4I44 4 I 4 I 44 I 4 4 I 4 4 I 44 4 4 4 I 44 4I4I44 4 I 4 4 4 I 4 44 I I I I 44 I 44 4 4 44 44I4I44 4 I 4 I 44 I 4 44 I 4 I 44 4 4 44 4 4 44 44I4I44 4 I 4 I 44 4 44 I I 4 I I 44 4 4 4 4 44 44I4I4u 4 I I I I I I I 44 I I I 44 4 44 4 4 44 44I4I4- 4 I I I I I 4 44 I . 4 4 I 44 4 44 4 4 44 44I4I44 I I I I I 4 4 4 I I I 44 44 I 4 4 4 44 44I4I4- N I I I I I I ON I I I vN NN I N. v N 0' ONINIII N I I I I I I I 44 I 4 I I 44 4 44 4 44 44 44I4I4- 4 I I I I I I 44 I I I 4 44 4 4 4 44 44. 44I4I44 I I I I I I 4 44 I I I 44 44 4 4 I 44 44 44I4I44 I I I I I I I 44 I I 4 I 4 4 4 44 44 44 44I4I44 I I I I I I I 4 I I I 44 44 I 4 4 44 44 44I4I44 4 I 4 I I I I I 44 I I 4 44 44 I I 44 44 44I4I44 I I I I I I I 44 I I 4 I 44 I 4 4 44 44 44I4I4u I I I I I I I 44 I 4 4 44 44 4 4 4 44 44 44I4I44 4 I I 4 I I I 44 44 4 I I 4 4 44 4 I 44 44I4I44 4 I I I I I I 4 I I I 4 44 4 44 44 I 44 44I4I4- I I I I I I . I 4 I I I 4 4 4 44 4 I 44 44I4I44 11m I I I I I I 4 I I 4 44 44 4 44 44I4Imm . 44 4o .444_Huuo .4.4 _.o.o _.444 .094- no 4444 44444 4444444446 4.4.4 4444 44444440 444444440 4444: 44044 44444 444444 444.44 4444 .coNumEuom :NNuom anon on» no mussoo ucNom ONAQouoouuom .N GNQQB 54 4 I I 4 I I 4 4 I I 4 4 44 4 44 I 4 I 44 4I4I44 4 I I I I I I 4 I I I I 44 4 44 I 4 I 44 4I4I44 4 I I I I I .I I 44 I I I 44 44 4 4 I 4 4 44 4I4I44 I I I I I I I 44 I I I 44 4r 4 4 I 4 4 44 7?..- 44 4a 2434 _.I40 :4..— F66 _ .43 644441 .4440 .uomal .04.: no no 4444 44444 444444.448 4.4.4 4444 44444444 44.44.4443 4444.. 44.444 4444.. 444444444 44444444 4444 44444.4 44.4.44 4444 4.4.44004 4 44449 55 In the fluvial pale red sandstones, quartz overgrowths are less common than albite overgrowths. Both overgrowths are superposed on hematite-stained clay that rims the detrital grains (Figure 24). The hematite formed by post-depositional aging of limonite (Hubert and Reed, 1978). In the lacustrine gray sandstone, the quartz and albite cements are superposed on clay rims unstained by hematite, because limonite was dissolved in the reducing lake water, evidently as organic- ferrous iron complexes (Hubert and Reed, 1978). Calcite is more common as cement than as replacement of feldspars. Dolomite cements are confined to the lacustrine cycle. It is believed that the dolomite was precipitated by partial evaporation of the perennial lake (Hubert gt 1;. , 1978). Few samples, near the base of the section, show evidence of pressure solution. Conspicuously sutured grain contacts (Figure 25) and closely spaced microstylolite seams are prevalent (Figure 26). This indicates that mechanical compaction has initiated quartz pressure solution (Adams, 1964; Pettijohn et 31., 1987). Pressure solution diminished considerably near the contact with the overlying Hampden Basalt, but was relatively high near the underlying Holyoke Basalt (Heald, 1956). Compared with the fractured grains of the New Haven Arkose, the absence of fracturing of framework grains in the sandstones of the East Berlin Formation is overwhelming. This may be due to the high abundance of Figure 24 Hematite-stained clay (H) coats detrital feldspar in fluvial sandstone of the East Berlin Formation. Sample # EB-l-lo. (Frame dim.: 0.4 mm x 0.6 mm) Figure 25 Sutured contact between quartz grains caused by pressure solution. Sample # EB-l-lo. (Frame dim.: 0.4 mm x 0.6 mm) 57 Figure 26 A microstylolitic solution seam near contact surface between coarse- and fine- grained sandstone in the East Berlin Formation. Sample # EB-l-ll. (Frame dim.: 2.5 mm x 3.8 mm) 58 hematite-stained clay that minimizes the effect of mechanical compaction on the quartz and feldspar grains as they are floating in the clay. A different variety of zeolite, analcime, is also present in two gray mudstone samples (EB-l-25 and -26) . The presence of analcime was initially established by XRD, however, analcime could not subsequently be identified in thin-section or with the aid of the SEM. A detailed discussion of zeolites will be addressed in chapter 7. DISTRIBUTION AND GENESIS OF THE BULK ROCK MINERALOGY The variety of major minerals is limited in the sedimentary sequences of Connecticut Valley. Ubiquitous occurrences of quartz, most of which is detrital, were observed in the different stops. To a lesser extent, quartz occurs as one of a number of authigenic cements, forming overgrowths on detrital quartz grains. Feldspar is the second most abundant mineral observed in these rocks. It occurs in all samples but samples collected from the caliche red mudstones of the New Haven Arkose (stop 2) . Plagioclase and microcline are the most abundant feldspars, occurring as detrital grains. Syntaxial authigenic plagioclase overgrowths are common among the New Haven Arkose rocks. April (1978), after Reed (1976), reported that the range in compositions of detrital plagioclase grains in the East Berlin Formation is An0 to Anz, while authigenic overgrowths are nearly pure albite. Detrital orthoclase 59 appears more frequently in the lacustrine deposits of the East Berlin Formation, but is not restricted to these rocks. Calcite and dolomite are the major carbonate minerals observed in the Hartford basin's rocks. Both are primary cementing agents, yet dolomite occurs also as concretions and isolated rhombs. Dolomite is restricted to the East Berlin Formation, and was not observed in the New Haven Arkose. Both minerals occur together in fewer than 28% of the East Berlin formation samples. On the other hand, calcite cement occurs in both formations, but is more abundant in the New Haven Arkose. Apparently, during and after deposition of the sediments in New Haven time (Late Triassic), the sedimentary environment remained deficient in magnesium such that dolomitization did not take place. This is unlike the condition reported by Hubert gt g1, ( 1976, 1978) for the Lower Jurassic East Berlin Formation in which calcite and Hg- calcite were extensively dolomitized early after burial by magnesium-rich pore waters. The abundance of calcite in the New Haven results in part from the numerous caliche paleosol horizons reported by Hubert ( 1977) and Hubert gt g1. , (1978) . They attributed the development of these horizons to semi- arid climatic conditions and to an influx of Ca++ from weathering in the source area and possibly from CaCC)3 dust derived from Lower Paleozoic carbonate rocks to the west. Hematite occurs pervasively as coatings or stains on detrital grains in the red beds of all formations. It is easily identifiable in thin sections as the source of the red 60 color in most samples. Hubert and Reed's (1978) four suggested modes of origin for hematite in the East Berlin Formation were summarized in chapter 1. Authigenic pyrite, in cubic and framboidal form, occurs only. in the black shale and lacustrine gray mudstone and siltstone of the East Berlin Formation. Hubert gt gl. , (1976) point out that reducing conditions must have been present during deposition of the lacustrine black shale and gray beds for authigenic pyrite to form. H28, derived from the decomposition of organic matter, combined with ferrous iron brought into solution by the reduction of detrital iron oxide- hydroxide grain coatings. The high organic content, color and undisturbed carbonate laminae of both rock types as well as the presence of unaltered magnetite grains (Hubert and Reed, 1978) and abundant articulated fish fossils in the black shales (Hubert gt 3].. , 1978) are further evidence for reducing anoxic sulphidic conditions (Berner, 1981) during and after sediment deposition. Laumontite occurs only in about 40% of the New Haven Arkose samples at stop 3 and 11% at stop 2, but no laumontite was observed in stop 4. The presence of laumontite in stop 3 and 2 was initially established by thin section petrography, and confirmed by XRD, SEM and EDS. Heald ( 1956) reported the presence of laumontite in some samples of the New Haven Arkose in Hamden and northern New Haven, Connecticut. He noted that laumontite fills pore spaces and partly replaces the feldspar, especially potash-feldspars, in contact zones near intrusives. 61 The fact that laumontite occupies cracks in fractured detrital grains and surrounds deformed mica indicates that it formed after at least initial compaction of the sediments (Heald, 1956) . Although laumontite may result from alteration of original feldspar in sediments (Hay, 1966), part of the material for the laumontite in the Triassic may have been introduced because much of it occurs as interstitial filling. The introduced material may be of igneous origin, for laumontite is present in some of the diabases and in the contact zone at Pine Rock in Hampden, Connecticut (Heald, 1956) . April (1978) reported the presence of analcime in the gray mudstone and black shale of the East Berlin Formation. In this study analcime occurs in only two (about 7%) of the twenty-eight samples of the East Berlin Formation. It was only detected by XRD, as it could not be identified in thin section or with the aid of SEM. This suggests that analcime exists as a well dispersed cement and may have formed as a direct precipitate from concentrated alkaline solutions or as a syngenetic alteration product of a zeolite or clay mineral precursor (Hay, 1966). In either case, its presence in the gray mudstones indicates a depositional or early diagenetic sedimentary environment influenced by sodium-rich alkaline solutions (Iijima and Utada, 1966). Huscovite occur as flakes visible in hand specimen and usually along with chlorite constitutes the bulk of the matrix surrounding detrital grains in most of the red siltstones and 62 sandstones. Brown biotite flakes occur in between detrital framework grains. Partial to nearly complete oxidized biotite (dark reddish brown) , sometimes bent due to compactional deformation are also noted. Intrastratal solution of Fe-silicate grains (biotite) was pervasive in the fluvial and lacustrine sandstones and believed to be the source of iron for hematite (Hubert and Reed, 1978). Sedimentary and metasedimentary lithic fragments, including chert, quartzite and schist, are the main rock fragment types in the Hartford Basin sandstone. Some fragments show partial alteration to clay minerals (smectite ?) and calcite replacement. The composition of the rock fragments reflect partial derivation from sedimentary cover or metamorphic envelopes that partly mask or shield basement gneiss and granites. ' PROVENANCE AND EVOLUTION OF THE ARKOSIC SANDSTONES Sandstone provenance refers to the group of factors that influenced the sand production in its source area (Pettijohn gt g1., 1987). Sandstone compositions are influenced by the character of sedimentary’ provenance, the nature of the sedimentary processes within the depositional basin, and the kind of dispersal paths that link provenance to basin that are governed by plate tectonics (Dickinson and Suczek, 1979) . Therefore, plate tectonics ultimately controls the distribution of the different types of sandstones. 63 Krynine (1950) believed that the necessary condition for production of arkosic sands was high relief with consequent rapid erosion rather than unfavorable climatic conditions. Distinguishing between these possibilities in an ancient arkose is difficult, but on the whole, it seems more likely that high relief is more important than rigorous climate in arkose formation (Pettijohn gt g1., 1987). Dickinson and Suczek (1979) found that the detrital framework modes of sandstone suites from different kinds of basins are a function of provenance types governed by plate tectonics. They utilized triangular diagrams that show that framework. 'proportions of quartz, the two feldspars (plagioclase and K-feldspar), polycrystalline quartzose lithics, and unstable volcanic and sedimentary lithic fragments successfully distinguish the key provenance types. In this study, the main detrital framework components (quartz, feldspars, and rock fragments) were plotted on a QFR ternary diagram (Figure 7a) and. then, compared. to Dickinson. and Suczek's diagrams. The comparison shows clearly that the detrital arkosic Hartford Basin sandstones were derived from the continental block (uplifted basement) provenance. Sands shed by rapid erosion from fault-bounded uplifts of pre- Triassic continental basement rocks accumulated in the nearby Hartford Basin without much transport, giving rise typically to quartzo-feldspathic sands of arkosic character. The percent-average QFR diagram (Figure 7b) shows that the composition of the East Berlin and the New Haven arkoses are 64 very similar with a slight increase in the rock fragment (sedimentary and metamorphic) content in the East Berlin Formation. QPK plot (Figure 7c) shows a high concentration of points in the direction of quartzose end which reflects increasing maturity or stability for detritus derived from continental block provence (Dickinson and Suczek, 1979). Several studies discussed the relation between sand composition and paleoclimate (Hack.and Suttner, 1977; Walker, 1978). These studies used thin-section petrography in order to compare the abundance of unstable constituents (feldspars and rock fragments) in ancient and modern sands under different paleoclimates. As mentioned in chapter 1, the Late Triassic climate was warm and dry, changing in Early Jurassic time to relatively cooler and probably wetter conditions (Hubert gt g1. , 1978, Suchecki gt 31. , 1988) . Velbel and Saad (1991) studied the Triassic Chatham Group sandstones of the Deep River basin (another Mesozoic rift-valley: #1 in figure 1), North Carolina, where the ancient sediments were produced under more arid conditions than the modern wet climate. They found that these subarkose to sublitharenite sediments have higher unstable grain contents (Qso-wFo-sol'o-so) than modern sands derived from similar source rocks but under a humid climate. This indicates that weathering is more important than diagenesis in determining the modal framework composition of the Chatham Group sandstones, as diagenesis tends to destroy unstable rock fragments, whereas weathering under arid climate causes preservation of rock fragments in the absence of 65 diagenetic effects. Compaction and cementation, without extensive replacement of the framework grains, were the main diagenetic signature in the Chatham Group sandstones. In contrast, in the Hartford Basin, unstable detrital framework grain abundances were modified by intense diagenetic processes, especially replacement of detrital grains by different authigenic minerals. Velbel and Saad (1991) concluded that diagenesis did not destroy lithic fragments in the Chatham Group. Rock fragments were modified by diagenesis in the Hartford Basin. This might explain the lower unstable grain contents (0,0,90F5_,51.0,2o) in the sediments of the Hartford Basin than those of the Chatham Group sandstones. However, a more likely explanation for the difference in the lithic fragment content between the Chatham Group and the Hartford Basin sediments is probably due to differences in the source rock of both basins. The Chatham group sublitharenites- subarkoses were derived from pre-Triassic metamorphic rocks of the adjacent Appalachian Piedmont (McCarn and Mansfield, 1986) , whereas the source of the arkoses of the Hartford Basin is the uplifted pre-Triassic crystalline basement rocks. This suggests that detailed study of early diagenetic minerals in addition to detrital minerals, is helpful for reconstructing paleoclimatic conditions, along with studies of the framework grain response to the various factors affecting these sediments. 66 PARAGENETIC SEQUENCE OF THE HARTFORD BASIN SANDSTONES The paragenetic sequence in the basin's sandstones varies stratigraphically from the New Haven Arkose to the East Berlin Formation. It varies slightly within the New Haven Arkose from one stop to another. Figures 27-30 summarize the diagenetic sequence in the four stops based on the relative timing of the precipitation of authigenic material after deposition as evident from the petrographic examination. In general, the paragenetic sequence in both formations begins with mechanical compaction of the sediments. Compaction in the New Haven Arkose was much more extensive than in the East Berlin Formation as evident by the absence of fracturing of detrital grains in the latter. The greater amount of compaction in the New Haven Arkose is related to additional sediment deposition on this formation as it was buried deeper than the East Berlin Formation. Hematite coatings formed after compaction as evident by coating all detrital grains and along their contacts. Hematite precipitation continued after quartz-overgrowth as evident by the presence of double hematite lines (Figure 15). Formation of chlorite grain coatings (stop 1) and pore- linings (stop 4) took place after the hematite coating as hematite separates detrital grains from chlorite cement. The highest chlorite content was seen in the New Haven Formation (stop 4). Authigenic syntaxial feldspar and quartz overgrowths were formed after the coatings. In most samples the overgrowths 67 23316383818 0! THE III IIVII 123088 (STOP 4) ow Compaction Fractures Hematite coating Pore-lining chlorite Pore-filling chlorite Quartz overgrowth Albitization Clay minerals (illite) Calcite replacement and cement YOUNG Figure 27 Summary of the paragenetic sequence in the New Haven Arkose (stop 4) 68 RARAGIUIBIB OF THE III HAVEN BRIDGE (STOP 3) oln vouuc Compaction . a Fractures : ea Chlorite pore- b.3m. filling (minor) Hematite coating ee #4 Quartz overgrowth . : Feldspar overgrowth L Albitisation : 44 Sericite? t, -*~% Clay minerals L, 44 (i11ite/sm.?) Zeolite ;__—...2 Figure 28 Summary of the paragenetic sequence in the New Haven Arkose (stop 3) 69 RARAGENBSIB OF TE! '8' HAVEN BRIDGE (STOP 2) mo Compaction : 4 Fractures F7 a Hematite coating : YOUNG Chlorite pore- filling Albitisation v sericite? P Clay minerals (illite/sm.?) Calcite replacement and cement Zeolite ? Figure 29 Summary of the paragenetic sequence in the New Haven Arkose (stop 2) 7O RARAGENESIS OF THE EAST BERLIN TORNATION (STOP 1) olo vounc Compaction :— 4: Hematite coating . J r fi Chlorite coating Quarts overgrowth . Feldspar overgrowth , Albitisation to % Clay minerals ‘ A4 (illite & sm.?) ‘ ‘ 7 Calcite replacement t______---u.“_m ' and cement Pressure solution . -_---. Dolomite cement ,Lg ? r ---—-------------0.0I-. Figure 30 Summary of the paragenetic sequence in the East Berlin Formation (stop 1). 71 are euhedral formed on detrital grains. Quartz overgrowths formed either contemporaneously with feldspar overgrowths or shortly after them. Petrographically it is hard to tell which phase began forming first, but thin section evidence clearly shows that the quartz overgrowths continued to form after the feldspar overgrowths. The ubiquitous presence of these overgrowths suggests that the pore fluids had a high concentration of sodium and silica, and that dissolved aluminum was present. Pressure solution can be another source of silica, but only in the sandstones of the East Berlin Formation. Additional sodium was required for albitization of potassium feldspars. Petrographic evidence does not clearly indicate when authigenic sericite and clay minerals formed in the New Haven sequence; however, they probably formed after the feldspar overgrowths and albitization. In the East Berlin Formation clay-mineral formation occurred before the feldspar overgrowths, as seen by a clay rim that separates overgrowths from the detrital feldspar grain. Diagenetic pore-filling chlorite cement could have precipitated either long after or immediately after the overgrowths and albitization. Calcite formed early in the New Haven Arkose as evident by its filling fractures in feldspar grains; this can be due to redistribution of carbonate in these caliche-rich rocks. Calcite replacement of feldspar could have formed earlier than the pore-filling cement, which formed later in the diagenetic 72 sequence, possibly as a result of deep burial and albitization of feldspars. There is a possibility that the pore-filling calcite is late in ‘the sequence, but. that its optical continuity with the rest of the fracture filling type (Figure 11) could easily be the result of many generations of calcite all being recrystallized at the end. Evidence of multiple generations of calcite was observed in the New Haven Arkoses (Figure 21). Under cathodoluminescence of sample NH-2-14 in figure 21, scattered parts of the calcite pore-filling are non-luminescent (dark red), whereas calcite replacement of feldspar grain which is in a different crystallographic orientation shows bright red luminescence suggesting multiple generations of calcite. This evidence supports the idea of recrystallization (neomorphism) of calcite. The above discussion shows how complicated the paragenesis of calcite may be; i.e. complex history of caliche, calcite fracture filling, and recrystallization optically continuous with pore- fillings. A detailed genetic investigation of the different types of carbonates in these sediments is suggested for future studies. Zeolite replacement of feldspar and pore-filling cement are considered to be the latest formed diagenetic phase in the New Haven Formation (stop 2 and 3) as evident by the absence of the calcite cement in the zeolite rich samples. Early dolomite cement is restricted to the alkaline lacustrine cycle of the East Berlin Formation. It is believed that its formation is due to evaporation of the magnesium- 73 rich lake water. A detailed discussion of some of the above mentioned diagenetic features (albitization, chloritization, and zeolites) and their proposed origin, supported by SEM, EDS, EHP, and BSEM evidences, will be addressed in the following chapters. CHAPTER 4 CLAY HINERALOGY The clay minerals identified in the New Haven Arkose and East Berlin Formation are illite, chlorite, smectite, vermiculite, kaolinite, expandable chlorite, mixed-layered illite-smectite, mixed-layered chlorite-smectite, and mixed- layered chlorite-vermiculite. The following is a presentation of the clay mineralogy of each formation as interpreted from their characteristic XRD reflections. CLAY MINERAL IDENTIFICATION The clay minerals were identified by their characteristic basal X-ray diffraction reflections. As described in chapter 2, various chemical and thermal treatments as well as peaks from non-basal planes (random mounts) were used to distinguish between clay mineral groups (e.g., smectite vs. vermiculite, dioctahedral vs. trioctahedral) and to identify' mineral species within groups (e.g., chlorite polytypes). No attempt was made in this study to determine quantitatively relative clay mineral abundances, except in a general way. Illitgt A basal sequence of 10, 5, and 3.33 Angstroms that remained unmodified after’ glycolation. was identified as illite. Heat treatment to 300'C and 550'C for 1 hour also caused no significant changes in d-spacings. 74 75 $121139... Basal reflections at (approximately) 14, 7, 4.7 and 3.5 Angstroms not affected by glycolation represent the chlorite phase. Heat treatment to 300'C and 550'C for 1 hour reinforces the 14 Angstrom (001) peak, whereas higher order reflections weaken or disappear. In some instances glycerol solvation causes a 14.2-14.5 Angstrom peak to broaden and shift to 15 Angstrom. Heat treatment at 550‘C displaces the peak to 13.8-14.1 Angstroms. This behavior seems to be indicative of expandable or swelling-chlorite type layers. Brindley (in Brown 1961) suggested that imperfections or "discontinuities" in the interlayer brucite sheets of swelling chlorite may allow organic molecules to enter and cause limited expansion to occur. It is possible that some random mixed-layering of chlorite and swelling chlorite layers does exist: however, in the absence of any low-order superlattice peak characteristic of ordered mixed-layering, this clay phase will herein be referred to as expandable chlorite. Chlorite polytypes were identified by h01 reflections (Hayes, 1970; Brown and Brindley, 1980) . Results of chlorite polytype analyses are given in chapter 6. m Clays of the smectite group were recognized by an (001) 14-15 Angstrom reflection expanding to 18 Angstroms upon magnesium saturation and glycerol solvation and collapsing to 10 Angstroms with heat treatment at 300’C and 550’C. The glycerol treatment confirmed smectite rather than a low charge vermiculite as the clay mineral (Walker, in Brown 1961). K- 76 saturation of the smectites in some cases caused contraction of the lattice to 12 Angstroms, but also frequently resulted in a diffuse range of reflections or complete collapse down to 10 Angstrom. Changes in relative humidity can easily cause K-saturated smectites to exhibit a range of hydration states such that the d(001) gradually shifts from 10 Angstroms (dry) to 12.5 Angstroms (wet) (Eslinger and Pevear, 1988). Therefore, K-saturation was not employed as a definitive test to distinguish smectites from vermiculites (12 Angstroms vs. 10 Angstroms collapse respectively) or as an indicator of the layer charge on the smectite. W Vermiculites, depending upon their layer charge, may or may not expand with glycerol-solvation (Walker, in Brown 1961). Vermiculites were recognized and distinguished- from smectites in this study by their inability to expand upon magnesium saturation and glycerol solvation. The (001) 14- 14.5 Angstrom peak contracts to 10 Angstroms upon both 1(- saturation and heat treatment to 300°C and 550'C. Although vermiculite and chlorite reflections may be juxtaposed and unresolved in a diffractogram, the higher order (001) reflections of vermiculite are normally weaker than those of chlorite. K-saturation and heat treatment, however, are the definitive tests used to discriminate between the two minerals. 77 mm Kaolinite was identified by its basal reflections at 7.15 and 3.58 Angstroms. However, in the presence of chlorite this is not diagnostic. The disappearance of the (001) 7.13-7.15 Angstrom peak upon heating to 550'C for 1 hour distinguishes kaolinite from chlorite. The resolution of the (004) chlorite peak at 3.55 Angstrom from the (002) kaolinite peak at 3.58 Angstrom in some samples aided in the discrimination of these two minerals. Kaolinite was identified in only two samples from the East Berlin Formation. W Mixed layered illite-smectite was recognized using the criteria of Reynolds (1980) , and Eslinger and Pevear (1988). Shifts in the position of (001) reflections between air-dried and glycerol-solvated samples as well as the symmetry of the major basal peaks were used to characterize the nature of the interlayering (random vs. ordered) and in some instances the approximate relative abundance of each component. Both 1:1 regularly interstratified chlorite-smectite and chlorite-vermiculite were recognized by superlattice reflections at 28.5-29 Angstroms and a series of rational higher order reflections at 14.3-14.7, 9.7, 7.2, and 4.78 Angstrom. Upon glycerol-solvation, the superlattice peaks of both shift to ~31-32 Angstrom with corresponding shifts of the ( 002) peaks to ~15.5-15.9 Angstrom. The two minerals are best distinguished by their behavior upon magnesium saturation and glycerol solvation; the chlorite-vermiculite showing no shift 78 in d-spacings relative to air-dried positions and the chlorite-smectite exhibiting a shift of the superlattice peak to 32 Angstrom corresponding to expansion of the smectite layers from ~15 to 18 Angstrom. Both K-saturation and heat treatment at 550’C for 1 hour result in peaks at 23-24 Angstrom and 11.8 to 12 Angstrom for the (001) and (002) reflections respectively. NEW HAVEN ARKOSE The <2 micron fraction of 60 samples from the New Haven Arkose was examined (Table 3). X-ray diffraction analysis demonstrates that illite is the dominant clay mineral in all samples, along with subordinate amounts of smectite. Slight shifts and asymmetries of the 10 Angstrom reflection between air-dried and glycerol-solvated XRD patterns suggest that in some samples the illite may be mixed-layered illite-smectite, in most cases revealed by a diffuse peak between 10 and 12 Angstroms in the air-dried state, which is not affected by potassium saturation but disappears with glycerol-solvation and heat treatment (Figure 31). In some samples, a d(060) reflection at 1.50-1.51 Angstroms indicates the mineral to be dioctahedral. Chlorite is present in the different stops of the New Haven Arkose. It was identified in 48 of the 60 samples and for some of the samples it displays a weak and diffuse reflection, probably poorly crystallized, whereas in the rest of the samples it shows a strong reflection at 14.3-14.4 79 Table 3. Clay mineralogy of the New Haven Arkose STOP 80 SAMPLE I LL . 08L . SM . 88-4-6 A — - 88-4-5 4 88-4-4 88-4-3 88-4-2 3 a: 2! > 3' V 3' 3’ :> 5 >‘ I I 88-4-1 nn-s-as wn-3-34 un-3-33 nn-a-sz NH-3-31 un-a-ao wn-a-zs un-3-27 3 wn-z-zs un-3-24 nn-a-zs I/S un-a-zz 88-3-21 M M - A I/S A I/S A wm-a-zo I/S 88-3-19 NH-3-18 88-3-17 y D' 3’ :F V 3’ {F > 3' {F 5 3’ :9 3 3' 3’ :P > I 88-3-16 80 Table 3 (Cont'd.) 88-3-14 A - M - 88-3-13 A - - - 88-3-12 A - - I/S 88-3-10 A - M - 88-3-8 A - A I/S 3 nn-3-7 A - A I/S un-a-s A - M - un-a-s A - M - nn-3-4 M - M - 88-3-3 A - - - wn-a-z A - - - 88-3-1 A - - - STOP 80 SAMPLE ILL . 08L . SM . III/84 NH-2-33 A - tr tr 88-2-30 A - - - 88-2-29 A tr - - 88-2-28 A - - tr NH-2-26 A - tr tr NH-2-25 A tr tr 2 88-2-22 A tr tr 88-2-21 A - - tr 88-2-20 A - A M 88-2-16 A tr A M 88-2-15 A M M 88-2-14 M M M 88-2-13 M tr A A 81 Table 3 (Cont'd.) 88-2-12 88-2-11 88-2-10 88-2-9 88-2-7 2 88-2-6 88-2-5 88-2-4 88-2-3 > 3’ :V F 3' 3’ {F V 3’ :V V 88-2-1 A = Abundant tr = Trace M = Minor A A tr tr M - tr - tr - tr - tr A _ M - M - - = 8086 82 Glycerol-solavtcd Mg-sanmtcd/Gly. K-satutated SSO'C Figure 31 x-ray diffraction traces of the <2 mm fraction of New Haven Arkose. Sample NH- 4-6 shows chlorite and illite-smectite patterns. 83 .Angstroms (Figure 31). Samples collected from stop 4, stratigraphically located in the lower portion of the New Haven Arkose, (Chapter 1, Figure 4) show the predominance of chlorite in all samples. A minor amount of mixed-layered illite-smectite is also present in only one sample at stop 4, and discret smectite is absent. Samples collected from mudstones and sandstones from stops 3 (near the Hampden basalt intrusion) and 2 (caliche- rich paleosol horizons), situated stratigraphically higher in the. NeW’ Haven sequence, are :mainly composed. of illite, smectite, and.mixed-layer illite-smectite. In some samples, a strong d(060) reflection occurring at about 1.502 Angstroms suggests a dioctahedral illite type. A weaker, yet distinct reflection at approximately 1.53 Angstroms indicates a trioctahedral smectite type. Chlorite occurs in portions of these outcrops. EAST BERLIN FORMATION The East Berlin Formation (stop 1) contains a varied clay mineral assemblage. Clay minerals identified in the 25 samples examined are illite, chlorite, smectite, vermiculite, swelling chlorite, kaolinite, and a number of interstratified minerals including illite-smectite, chlorite-smectite and chlorite-vermiculite (Table 4). Figure (32) shows randomly interstratified illite-smectite, where a small 18 Angstrom peak appears by glycolation (Eslinger and Pevear, 1988) . Generally, these rocks are illitic with most containing subordinate amounts of chlorite. 84 Table 4. Clay mineralogy of the East Berlin Formation STOP SAMPLE ILL. CHL. SM. VERM. CHL/SM CHL/VER OTHER EB-1-28 tr EB-1-25 A EB-1-24 EB-1-23 tr EB-1-20 tr EB-1-19 A EB-1-18 y EB-1-17 ff 3 EB-1-15 EB-1-14 1 EB-1-13 EB-1-12 EB-1-11 EB-1-10 EB-1-9 EB-1-S EB-1-7 EB-1-6 EB-1-S EB-1-4 EB-1-3 EE-1-2 3 3' 3’ 2! 3 3: 3’ :V 3 3: i! 3 3’ :F 3 EB-1-1 A = Abundant tr tr tr M - tr tr - tr - tr = Trace M A - A tr M tr A A M A tr A tr M - M = Minor EXP EXP EXP Kao .chl .chl .chl .tr 3 8080 85 10a Glycerol-solvatcd Mg-satmatod/Gly K-saturatcd 3M'C ‘ in a? a?) 72‘ degree: 20 Figure 32 x-ray diffraction patterns of the <2 um fraction of the New Haven Arkose. Sample NH-3-20 shows illite-smectite interlayer. dist: w: IE: rock syst oxid syst repr cry: (Tak is refj <1 am for idE am: of 34: 86 The various lithologies in the East Berlin Formation are distinguished by distinct clay mineral assemblages. Hubert gt g1. , (1976) assigned two major depositional systems for the rock units in the East Berlin Formation: l) the flood plain system consists of stream channel, floodplain and shallow oxidizing temporal lake sediments, and: 2) the perennial lake system contains gray siltstone-mudstone and black shale representing shallow and deeper lakes respectively. W Floodplain system red beds are characterized by well- crystallized illite and abundant to minor amounts of chlorite (Table 4 and Figure 33). Illite is dioctahedral and chlorite is trioctahedral in character as indicated by d(060) reflections occurring at 1.502-1.506 Angstroms and 1.544- l.546 Angstroms respectively. April (1978) reported the predominance of the (high temperature) 2M polytype of illite in these rocks, ranging in abundance from 65 to 100% 2M in the <1 micron fraction. In this study, the presence of type Ib chlorite in these sediments that suggests an authigenic origin for this mineral (refer to Chapter 6 for the method of identification and diagnostic peaks of this polytype). Minor amounts of vermiculite were detected in the floodplain red mudstone samples # EB-l-4, EB-1-24 and EB-1-25. Minor amount of kaolinite and illite are observed in these rocks (Figure 34). Samples collected near the Hampden Basalt-red mudstone contact contain abundant well crystallized 1: 1 interstratified 87 3.33 ,5, 51) Air ' . I 4.75 Mg-satnratod/Gly. K-satnratod SSO'C #30 20 10 4 2 deym 20 Figure 33 XRD pattern of the <2 pm of sample EB-l- 2, a floodplain red sandstone in the East Berlin Formation. Sample contains illite and chlorite. 88 10 lugumuauVGy; 14.3 K-saturated SSO'C deg-4:620 Figure 34 XRD pattern of the <2 pm of sample EB-l- 2 of the East Berlin Formation. Sample contains illite and minor amount of kaolinite. chlor occur in th Basal a qr mine deti is i 89 chlorite-vermiculite (Figure 35). April (1980) reported the occurrence of regularly interstratified chlorite-vermiculite in these floodplain red mudstones directly beneath the Hampden Basalt. Samples obtained further away from the contact show a gradual decrease in the abundance of the mixed-layered mineral. The trend is noted by observing changes in the definition of the superlattice peak. This basal reflection is a sensitive indicator of the degree of ordering for these interstratified clays. A well developed superlattice suggests perfect to near perfect 1:1 ordering, whereas a poorly defined superlattice reflections implies a random interstratification, for the mixed-layered chlorite-vermiculite (Millot, 1970) , (Figure 35). 2) nggngial lgke sygtgm The clay mineralogy of the lacustrine gray beds is dominated by illite, chlorite and/or interstratified chlorite- smectite (Table 4) . Minor amounts of swelling chlorite and/or discrete smectite are also present in nearly 1/3 of the samples (Figure 36) . Illite is present to some extent in every sample. April (1978) characterized the illite to be 100% 1Md mica and highly crystalline as evidenced by a sharp basal reflections. An illite d(060) reflection at 1.50-1.51 Angstroms indicates a dioctahedral nature for this mineral. Chlorite was identified in only five samples. It is trioctahedral as indicated by strong intensity d(060) reflections at approximately 1.54 Angstroms in samples containing only the dioctahedral illite-chlorite assemblage. 9O 14.25 Air-dried Glycerol-solvated 550'C so 25 16 i 2' degme: 20 Figure 35 XRD pattern of the <2 um fraction of sample EB-1-25, East Berlin Formation. Sample contains chlorite-vermiculite interlayers. 91 i m 4 2 tkyonzo 8r- Figure 36 XRD pattern of the <2 um of sample EB-l- 13, East Berlin Formation. Sample contains well-crystallized illite and chlorite. The i1 as th« of thc to be varie many Chara refle Angs1 trea' 550°| shif that dch 1.5< Saml to I fOr 38) Dec New Ch int 92 The intensities of the sequence of basal reflections as well as the position of the d(001) imply a high magnesian content of the chlorite (Brindley, in Brown 1961) . Chlorite was found to be IIb polytype which is characteristically a detrital variety (Chapter 6). A mixed-layered chlorite-smectite occurs abundantly in many of the gray mudstones and siltstones. The mineral is characterized by a distinct superlattice d(001) basal reflection at 29 Angstroms which shifts to 32 Angstroms (14 Angstroms chlorite-18 Angstroms smectite) upon glycerol treatment after magnesium saturation (Figure 37) . Heating to 550'C for 1 hour induces structural contraction causing a shift in the d(001) to 24 Angstroms with a d(002) spacing at 12 Angstroms. A strong 1.536 Angstrom reflection indicates that the mineral is trioctahedral. A small amount of dioctahedral illite is probably associated with the mixed- layered mineral as indicated by a weak d(060) reflection at 1.506 Angstroms. Swelling chlorite occurs to a minor extent in some samples. It is identified by a 14 Angstrom peak that broadens to 14.5-15 Angstroms after glycolation and by heating to 550'C for 1 hour, after which it remains at 14 Angstroms (Figure 38). Suchecki gt 31., (1977) described a similar mineral occurring in the rocks of the Cow Head klippe, western Newfoundland, and characterized it as a mixed-layered chlorite-expandable layer clay with random interstratification. April (1978) believes that the 93 143 Glycerol-saluted 8.1 13.1 lwkamnaa222;,»flL__,J\~a__Apj\j{'A 36 10.1 8.99 K-saturatod 7.17 an ”4 soo'c ' . i U/ 10 550'C 8) 20 m 20 10 4 —2‘ Figure 37 XRD traces of the <2 pm of sample EB-l- 19, East Berlin Formation. It contains chlorite-smectite interlayer. 885 14.6 333 7.12 SD Ait-driod 10-0 110 Its Mg-saturatod/Gly. 10 14.1 K-saturatod 10 14.2 amt: 30 Z) 10 4 2 degree: 20 Figure 38 XRD pattern for the <2 um of sample EB- 1-15, East Berlin Formation. Sample contains illite and expandable chlorite phases. 95 expandable layer might well in itself be an expandable or swelling chlorite. The black shales of the lacustrine sequence contain major amounts of discrete smectite and illite, some interstratified illite-smectite and minor amounts of chlorite (Figure 39) . Dioctahedral illite and trioctahedral smectite are present as evidenced by d(060) reflections occurring at 1.50 and 1.52 Angstroms respectively. Interstratified illite-smectite occurs in many samples of the black shales. Identifications were made by observing shifts in the position of the first order reflection toward the low angle (higher d-spacing) side. ORIGIN AND DISTRIBUTION OF THE CLAY MINERALS The Hartford Basin is characterized by terrestrial sedimentation: however, the clay-mineral assemblages in many areas of the basin are similar. The distribution of clay minerals in the.Triassic-Jurassic deposits of the Connecticut Valley resembles the general scheme proposed by Millot (1970) . Clay minerals in sedimentary rocks may originate in a number of ways. Generally, three principal processes account for their genesis: 1) detrital inheritance: 2) transformation; and 3) neoformation (Millot, 1970). Mechanical or detrital inheritance implies that the clays in the depositional environment are derived from the source area and remain unaltered during burial. Whether or not the clay lattice will be modified is determined by the clay mineral's stability and 96 Mg-sanuatcd/Gly. 10.05 10 Kosanuatcd 7.17 SSO'C degte: 20 Figure 39 XRD pattern of the <2 um fraction. Black shale of the East Berlin Formation. Sample contains illite, smectite, and traces of kaolinite. ‘ 97 the chemical nature of the sedimentary environment. Clay mineral transformation may take place during weathering, sedimentation or diagenesis (burial metamorphism) . This may occur by either aggradation or degradation processes (Millot, 1970) . These processes are illustrated by reactions such as: chlorite - vermiculite: illite - vermiculite: chlorite - mixed-layered chlorite-smectite. Finally, neoformation or authigenesis is the process by which clay minerals are newly synthesized in the sedimentary environment. Reactions involving existing clay minerals, non- clay minerals, pore waters and gels may produce neoformed clay minerals under innumerable physicochemical conditions (Millot, 1970). Although these processes are well documented in the literature, criteria for determining the genesis of clay minerals in sedimentary rocks are few in number. The origin of some of the clay-mineral assemblages seems clear in the light of the sedimentologic and mineralogic evidences, yet the genesis of others is problematic and open to several interpretations. Generally, the distribution of clay minerals in the Triassic-Jurassic beds of the Connecticut Valley can be described in terms of clay-mineral occurrences in lithologies that represent three major depositional environments namely: 1) floodplain environment (red beds): 2) shallow lacustrine environment (gray beds): 3) deep lacustrine environment (black shale) (Xrynine, 1950: Hubert gt 31., 1976: Hubert, 1977: Hubert gt 31., 1978). April (1978) summarized the clay 98 mineral distribution in the three major depositional environments in the basin as follows: a) WWW - containing abundant 2M illite of detrital origin with subordinate amounts of chlorite, smectite and interstratified illite-smectite and rare occurrences of vermiculite and kaolinite. M W - containing the assemblage 1Md illite + chlorite with subordinate amounts of interstratified chlorite-smectite, discrete smectite and expandable chlorite. This clay mineral assemblage indicates much authigenic mineral formation and less detrital influence (April, 1978). C) W - characterized by 1Md illite + trioctahedral smectite assemblage with minor amounts of chlorite and mixed-layered illite-smectite. The following is an attempt to depict the possible origin of the clay mineral assemblages in the study area. Illite Illite is believed to have originated primarily, in the shallow buried East Berlin Formation, as a detrital phase inherited from the mechanical and chemical breakdown of micas in the crystalline metamorphic and igneous rocks in the source highlands. In X-ray diffractograms, illite d(001) reflections are often sharp and intense indicating the presence of a well crystallized material. 99 Subjected to weathering during soil development in the source area and/or during transportation and reworking in the basin, it is not unlikely that some, if not much, of the detrital illite suffered some degree of chemical/structural degradation. Broad and weak reflections in diffractograms indicate that illite is present mainly in degraded form. The occurrence of well-crystallized illite does not necessarily imply that they were deposited as such. Millot (1970) stated that the degree of crystallinity may reflect subsequent rejuvenation (recrystallization) during burial. Therefore, the well-crystallized illite could indicate a relatively higher diagenetic stage (Gottfried and Kotra, 1988), assuming that the minerals were affected only by burial during diagenesis. Illite in the deeply buried (> 3 km, burial temperature: about 110'-150'C) New' Haven .Arkose is ibelieved. to have originated diagenetically; Extensive illitization of illite- smectite mixed-layer is believed to be the source of illite in these rocks. This is demonstrated by the down-section increase of illite and decrease of smectite (Tables 3 and 4). Chlorite Chlorite occurs in any particular sample in one or more of the following forms: 1) discrete chlorite: 2) expandable chlorite: 3) interstratified chlorite-smectite: and 4) interstratified chlorite-vermiculite. According to Millot (1970) and Dunoyer De Segonzac (1970), the three phases could 100 represent various stages in the diagenetic transformation of a degraded 2:1 clay mineral (smectite ?) by magnesium-rich waters in the order from interstratified form to a discrete form. In X-ray diffractograms, chlorite d(001) reflections are often sharp and intense indicating the presence of a well- crystallized material. Identification of the chlorite polytypes suggest the presence of a detrital IIb type variety mainly in the East Berlin Formation and.parts of stop 2 of the New Haven.Arkose (Chapter 6). Authigenic chlorite cement (Ib polytype: Chapter 6) is present in the other stops of the New Haven Arkose. Chlorite is either absent or shows weak reflections in diffractograms in samples from the East Berlin Formation. That suggests that chlorite suffered some degree of physical or chemical degradation due to diagenesis, or it was never there. A detailed discussion on the distribution, texture and origin of chlorite will be presented in chapter 6. m Authigenic precipitation of smectite in the pores of the red muds is favored, although it is possible that some smectite may have been inherited from the detrital load (April, 1978). Hubert .gt, 31., (1978) stated. that the floodplain environment of the East Berlin Formation experienced numerous wet and dry periods. This is evidenced by the occurrence of abundant mudcracks, short-lived shallow oxidizing lakes, dinosaur footprints, raindrop impressions, 101 trails, etc. It seems reasonable to infer that during periods of protracted dryness in the poorly drained floodplain lowlands, ions in solution became concentrated in both surface and pore waters (April, 1978) . Under such conditions the authigenic smectite is favored (Millot, 1970: Dunoyer de Segonzac, 1970: Keller, 1970). With smectite forming in the floodplain during times of drought, it is not difficult to visualize sediment redistribution with the onset of heavy winds, rain or flood (April, 1978). This might account for the apparent lack of correlation between clay-mineral assemblages and depositional subenvironment. Also, diluted by large volumes of detrital illite and chlorite, smectite would remain a minor constituent in the sediments. 1211112111132: Few samples contain minor amounts of vermiculite. It may have been derived as a detrital component from the chemically weathered source area or from the degradation of illite and chlorite in soil horizons developing on the floodplain (April, 1978). Before burial, vermiculite was probably a much more abundant constituent in the floodplain sediments. Aggradation to illite and/or chlorite following adsorption of magnesium and potassium.during burial eventually reduced‘vermiculite to minor importance in the sedimentary sequence. WW Samples collected from the upper part of the New Haven 102 Arkose contain.the clay mineral assemblage illite + smectite. Hower gt 31., (1976) proposed the following equation for the conversion of smectite to illite in Gulf Coast sediments: smectite + K-feldspar (+ mica ?) - illite + quartz + chlorite. (1) Assuming the original clay-mineral assemblage of the upper New Haven sediments was dominantly illite + smectite, conversion of some smectite to illite-smectite would produce the observed assemblage of illite + chlorite + illite-smectite + discrete smectite. The persistence of the assemblage illite + smectite indicates that maximum temperatures in the upper part of the sequence did not exceed those attributed to the upper limit of smectite stability (Hower gt 31., 1976: Velde, 1977). Velde (1977) gave this temperature as about 100'C. Ramseyer- and Boles (1986) reported the occurrence of smectite and illite-smectite interlayers at a burial temperature of about 120‘C to 140'C. Palynological data of Cornet and Traverse (1975) shows spore color and reflectance to indicate that the rocks of the Shuttle Meadow Formation (located just above the New Haven Formation) have not been subjected to temperatures above 200'C. The absence of discrete smectite in the lower part of the New Haven Arkose indicates that the temperature ceiling for smectite stability was exceeded in the lower part of the sequence during the conversion of smectite to illite- smectite, and ultimately to illite (stop 4, Table 3). Pratt gt 31. (1988) studied the thermal history of the Hartford 103 Basin and proposed a regional pattern of thermal maturation increases down the stratigraphic section, i.e. increases with depth of burial. They reported a low level of thermal maturity in the Portland Formation (uppermost formation in the succession) and suggest that these rocks did not reach burial temperatures above 90°C. The East Berlin and Shuttle Meadow sediments (thermally mature) reached burial temperatures of 90 to 110'C. Samples from the Triassic New Haven.Arkose were not analyzed, but their equivalent in the Newark Basin (the Passaic Formation) were thermally overmature with respect to petroleum generation. Therefore, the New Haven .Arkose probably reached a burial temperature >110°C, as it is the deepest formation in the stratigraphic section. Additional evidence in support of this inference comes from the observation that K-feldspar is abundant in the chlorite-deficient rocks, yet present in minor amounts or almost absent from the chlorite bearing rocks. Figure 40 is a plot of the percent chlorite versus the percent K-feldspars of some New Haven Arkose samples (Table 1): it shows an inverse relationship between the two minerals. Note that in the New Haven Arkose, the greatest depletion of K-feldspar, and the greatest abundance of authigenic chlorite, occur in the deepest samples (stop 4) . Equation (1) shows that K- feldspar is one possible source of potassium for the formation of illite-smectite and eventually illite from smectite, and that chlorite is one of the products, so the inverse relationship between K-feldspar and chlorite is consistent 104 % CHL. VS 76 K-SPAR 50 u u .. 0 N.H.FM. (STOP 4) ”+ A 8.11.91. (STOP 3) 40 “A + N.H.FM. (STOP 2) ‘ £1: 3 o 15.13.94.610? 1) : 1~ U) 30 iféa 0 _ C3 48' .J ‘~ 0) Lu “1' 20 '~ :5 .. + a“ .4) (D as __ C) 0 10 0 " 216° no 98 r=o3 o 10? H . 0 10 20 30 76 CHLORITE Figure 40 Plot of the % chlorite vs. % K-feldspar for the three stops of the New Haven Formation. 105 with reaction (1). Corn-mains The term corrensite was originally proposed by Lippman (1956) to describe a mixed-layered clay mineral with regularly alternating layers of chlorite and swelling chlorite. Since that time, the terms corrensite, corrensitic-material and corrensite-like have been used to describe a variety of similar mixed-layered clay minerals in a spectrum of lithologies and modes of origin. These clays result from the regular, or near-regular, interstratification of chlorite with swelling chlorite, smectite or vermiculite (Early gt 31., 1956: Bradley'and Weaver, 1956: Lippman, 1956: Peterson, 1961: Johnson, 1964: Dunoyer de Segonzac, 1970: Blatter gt 31., 1973: Post and.Janke, 1974: Ross and.Kodama, 1976: April, 1980 and 1981: Vergo and April, 1982). Brown (1961) suggested that a specific name be furnished to a mixed-layered clay for which "the interstratification is regular and the nature of the layers is establishedfi. .Martin- Vivaldi and MacEwan (1960) attempted to clarify the nomenclature of mixed-layered clays. They concluded that there is much confusion over the meaning of the term corrensite. For the sake of concision, and not to confuse the matter further, the term corrensite will be used to describe an ordered 1:1 interstratified chlorite-swelling layer clay mineral. 106 Mechanisms controlling corrensite formation are not yet fully understood: this mineral forms under a wide variety of conditions. Two distinct, rather general models for corrensite formation that are related to this study will be focused on. Millot (1970) used the term aggrading and degrading to describe these models. The aggrading model was synthesized using information from Weaver and Pollard (1975), Carstea gt 31., (1970) and Dunoyer de Segonzac (1970). They assumed that the initial material is some 2:1 layer silicate such as smectite or vermiculite. By exposing it to a diagenetic or metasomatic environment rich in magnesium, the mineral may begin aggrading by random fixation between tetrahedral sheets of Mg-hydroxy (brucite) interlayers. The development of asymmetric structural charge distributions on the lattice causes fixation to become more ordered and results in regular alternations of 2:2 (chlorite) and 2:1 (smectite or vermiculite) sheets. The degrading model differs from the above mentioned one in that the parent material from which the corrensite forms is usually a chlorite (Bradley and Weaver, 1956: Johnson, 1964: Post and Janke, 1973: Ross and Kodama, 1976). Structural disruption of interlayer brucite sheets by weathering or oxidation can cause selective removal of alternate interlayers. This may result from asymmetries in the structural charge distribution within the 2: 1 layers (April, 1978). Ross and Kodama (1976) have shown that for chlorites, those with intermediate Fe+2 contents (brunsvigites) 107 are most likely to alter to a regularly interstratified chlorite-vermiculite. It should be noted that this model seems to be more directed toward explaining the genesis of interstratified chlorite-vermiculite rather than chlorite- smectite. The following is a idiscussion of the origin and occurrences of corrensite in the East Berlin Formation. As mentioned earlier in this chapter no corrensite was detected in the New Haven Arkoses. This discussion is based on XRD analysis, more discussion of the distribution and origin of corrensite based on petrographic, SEM, and polytype analyses in Chapter 6. Origin and Occurrence of the Chlorite-smectite Interlayers- Diffractograms of samples from the upper parts of the East Berlin Formation show well- to poorly ordered mixed-layer chlorite/smectite. The behavior of corrensite to different treatments is illustrated in Figure 37. The air-dried and glycerol-solvated samples display a peak at about 28.5 Angstroms and about 31 Angstrom respectively. Upon Mg- saturation and glycerol treatment, a well defined peak at 32 Angstroms appears as the result of regularly alternating 14 and 18 Angstrom layers. The swelling layers partially collapse to 12.5 Angstrom with potassium saturation and totally collapse upon heating to 300'C and 550'C: the 24 Angstrom superlattice peak is now the result of the regular interstratification of 10 Angstrom collapsed swelling layers 108 and 14 Angstrom chlorite. The behavior of the swelling layers is characteristic of smectite rather than vermiculite. The author believes that the mixed-layered chlorite- smectite in the East Berlin sedimentary sequence is formed by the alteration (chloritization) of a precursor smectite. Smectite occurs in.minor amounts in the gray mudstones and is also the predominant clay mineral in the black shale of the lake cycle sequence. It is clearly absent to rare in the corrensite-rich upper parts of the East Berlin Formation, implying that the original smectite altered to corrensite. According to Hubert gt _1. (1976), structures including ripple marks, dolomite concretions, mudcracks and dinosaur footprints indicate deposition of the upper lake cycle in shallow water. The authors also stated that the combined mineral assemblage of the black shale and gray mudstone- suggests alkaline, hard water lakes with abundant Mg“, Ca“, Na+ cations and HCO,’ and so,“ anions. Under these conditions authigenic smectite is favored (Weaver gt 31., 1975). However, with extended evaporation of the lake waters conditions would shift to favor corrensite over smectite. With the increased evaporation dolomite ‘would begin to precipitate. As a result, pH would rise in the increasingly alkaline lake water which would favor the precipitation of analcime (Hay, 1966). Corrensite formation likely began in the depositional environment and continued during burial as alkaline, magnesium-rich pore-waters continued to react with the 109 sediment . Origin and Occurrence of the Chlorite-vermiculite Interlayers- Samples collected from the East Berlin Formation near the contact with the overlying Hampden Basalt contain a well ordered corrensite. With increasing distance from the contact a more poorly ordered corrensite plus relatively greater amounts of illite are predominant. Figure 35 is a series of diffractograms illustrating the behavior of corrensite with different treatments. The diffraction pattern for the air-dried sample clearly shows the presence of a superlattice peak at approximately 28.5 Angstroms that expands upon glycolation giving a d(001) reflection at about 30.5 Angstroms. These data indicate a well ordered 1:1 interstratification of a 14-14.5 Angstrom peak which swells to 16.5-17 Angstrom with glycol solvation. Failure of the swelling layers which expanded with glycerol to do the same upon Mg-saturation and treatment with glycerol suggests a character more related to vermiculite rather than smectite. The restricted occurrence of the 1:1 regularly interstratified chlorite-vermiculite to the East Berlin floodplain red mudstone adjacent to the lowest Hampden lava flow prevents an origin strictly by inheritance. Rather, it is almost certain that the corrensite is an alteration product formed as a direct result of the physicochemical conditions brought about by emplacement of the lava flow. As reported 110 previously, corrensite occurs below the basalt. The occurrence of 1:1 regularly interstratified mixed-layered minerals as the result of hydrothermal alteration has been previously reported by a number of authors (Velde, 1977: April, 1978 and 1980). The clay mineral composition of the East Berlin Formation grades from expanding chlorite, to chlorite-smectite, and finally to chlorite-vermiculite (Table 4) as you get closer to the basalt (Figure 6). That suggests that the corrensite originated mostly by aggrading transformation of a smectite precursor. Sources of magnesium are believed to be related to contact with the Hampden basalt, as noticed by the concentration of corrensite near the lava. Near the contact, hydrothermal fluids originating from the lava and from the synchronous alteration of basalt fragments by superheated pore waters provided a source of magnesium. Further from the contact, magnesium was primarily derived from the thermal dissociation of dolomite (April, 1980). SUMMARY OF THE CLAY MINERALOGY This study of the clay mineralogy of the Triassic- Jurassic rocks of the Hartford Basin has led to the identification of the following clay minerals: illite, chlorite, smectite, vermiculite, expandable chlorite, mixed- layered illite-smectite, chlorite-smectite and chlorite- 111 vermiculite. The floodplain sediments of the.New'Haven Arkose contain illite, chlorite, smectite, and interstratified illite- smectite and rare occurrences of vermiculite. The lacustrine sediments of the East Berlin Formation contain illite, smectite, subordinate amounts of chlorite, and corrensite. The distribution of chlorite and mixed-layered illite- smectite in the New Haven Arkose indicates that maximum temperatures in the upper sedimentary sequence of the Hartford Basin did not exceed those attributed to the upper limit of smectite stability (100-150’C). The absence of smectite in the basal New Haven Arkose, the abundance of authigenic chlorite, and the decreased K-feldspar abundance all indicate more extensive illitization, and possibly temperatures above smectite stability, at the base of the section. Thermal dedolomitization in the red mudstones beneath basalt flows resulted in the transfer of magnesium from carbonates to silicates and the formation of a 1:1 regularly interstratified chlorite-vermiculite (April, 1980). Uptake of magnesium by precursor smectite resulted in the formation of an expandable chlorite followed by a 1:1 regularly interstratified chlorite-smectite in the upper gray mudstone of the perennial lake cycles. This mineral was further altered to regular interstratified chlorite- vermiculite near the overlying basalt. DIAGENETIC ALEITIEATIO8 OP PELDSPARS Diagenetic albitization of potassium feldspars has been recognized in the various formations of the Hartford Basin. Petrographic, SEM, and BSEM investigations revealed that albitization is prominent in the New Haven Arkose, whereas it is uncommon in the East Berlin Formation. The following is an attempt to describe and characterize the texture and origin of the albitized feldspar in the Hartford Basin rocks. Albitization of K-feldspars in igneous and metamorphic rocks has long been known (Anderson, 1937: Starkey, 1959: Smith, 1974) , but analogous albitization in sandstones during burial diagenesis has not been as well documented. Middleton (1972) reported that K-feldspar present in Charny sandstones (Quebec) has been albitized during diagenesis. Lajoie (1973) questioned Middleton's conclusion, suggesting a detrital rather than diagenetic origin of the albites. Recently, diagenetic albitization of K-feldspars has been recognized by a few more workers (Ogunyomi gt 31., 1981: Walker, 1984: and Saigal gt 31. , 1988) in sandstones from different parts of the world. Albitization of plagioclase in sedimentary rocks has been recorded by several workers from different parts of the world (Iijima and Utada, 1972: Surdam, 1973: Merino, 1975: Land and Millikan, 1981: Boles, 1982) . Therefore, albitization of detrital feldspars is a widespread and important process which 112 113 can significantly alter the original sandstone framework composition, form several byproducts (e.g., illite, kaolinite, and calcite: Saigal gt 31., 1988), and modify pore size and geometry (Boles, 1982) . These changes can influence reservoir properties: therefore it is important to recognize diagenetic albitization. In this study, the author believes that albitization has occurred in situ, during burial diagenesis as seen by the pervasive albitization observed in the Upper Triassic New Haven Arkose (deeply buried) compared to the minor amounts present in the Lower Jurassic East Berlin Formation (shallow buried). The following is a presentation of a comprehensive description of textures of diagenetically albitized K-feldspar grains as revealed by optical microscopy, SEM, EDS and BSEM, and a shorter discussion of albitization of plagioclase. PETROLOGY AND TEXTURES OF ALBITIZED K-FELDSPAR Standard optical microscopy revealed that the albitized feldspar grains are characteristically untwinned and mostly riddled.with.abundant.minute.brownish inclusions (Figure 41). A wide range of variation from only slight to complete pseudomorphic replacement of K-feldspar by albite has been observed in the different stops of the New Haven Arkose. Generally, albitization in the New Haven Arkose tends to be incomplete and patchy high in the section, while nearly complete pseudomorphic replacement is more common lower in the section (Table 1). Saigal gt 31. (1988), in their study of 114 Figure 41 Thin-section photomicrograph of partly albitized K-feldspar grain riddled with abundant inclusions. Sample # NH-3-16. (Frame dim.: 2.5 mm x 3.8 mm) 115 the Jurassic clastic reservoir rocks from offshore Norway, found that albitization occurs at depths ranging between 3.0 km to >3.5 km for the shallow and deep depths respectively. Morad gt 31. , (1990) in their study of the Triassic sandstones from the Snorre Field, Norwegian North Sea, reported that albitization of K-feldspar would increase at greater burial depths and at higher temperatures (>3 km and higher than lOO'C). The albitized patches may be irregular or planar lamellar in shape. The planar lamellar structure resembles perthitic texture and is similar to those structures described by Middleton (1972)., and Ogunyomi gt 31. (1981) . Partially altered grains with irregular and tabular patches of albite characteristically show a blocky to tabular sector extinction pattern (usually resembling textures of chessboard albite) ,- while complete albite pseudomorphs generally show uniform extinction (Figures 42 and 43). Similar blocky to tabular sector extinction patterns have recently been reported by Gold (1987 ) in partially albiti zed plagioclase grains . Backscattered electron images and EDS patterns clearly reveal that the grains with sector-extinction patterns are chemically inhomogeneous (Figure 44) . Domains of albite are represented by darker shades of gray, while relict K-feldspar domains are represented by lighter shades of gray (Figure 45) . The compositional contrast illustrated by backscattered images was confirmed by EDS and electron microprobe analyses (Figure 46, and Appendix A). This compositional inhomogeneity causes v V .‘ l, 4 2‘. L” .- ..l “(H F :“W‘? Figure 42 Photomicrograph of albitized K-feldspar grain showing blocky to tabular sector extension (chessboard albite) patterns. Sample # NH-3-16. (Frame dim.: 2.5 mm x 3.8 mm) Figure 43 Photomicrograph showing uniform extinction of albitized K-feldspar grain. Surrounding grains are mostly of quartz. Sample # NH-3-16. (Frame dim.: 1.0 mm x 1.5 mm) (m Figure 44 Corresponding BSEI (A and B) of the albitized grain in Figure (42) revealing albitization features more clearly due to chemical inhomogeneity. B) is the enlarged image of (A). Sample # NH-3-16. Bar scale= 1000 um and 100 gm for A and B respectively. 118 Figure 45 Backscattered electron image of albitized K-feldspar. Notice that albite is dark gray and K-feldspar is light gray. Surrounding grains showing uniform dark gray shades are quartz. Sample # NH-3- 19. Bar scale = 100 um. 119 ? (A) F3 IIZ RH HUI (8) Figure 46 EDS pattern showing the elemental chemical composition of the albitized grain in figure (45). A) EDS pattern of albite (dark gray) and for K-feldspar (light gray), (B). Sample # NH-3-19. 120 blocky to tabular sector extinction patterns in the partly albitized grains which often resemble textures of chessboard albite (Figure 47) . The characteristic minute brownish inclusions (Figure 41) are useful in finding untwinned albitized grains and have been reported by several workers (Middleton, 1972: Ogunyomi gt 31., 1981: Boles, 1984: Walker, 1984). These "dusty" or cloudy inclusions are believed to be composed of submicroscopic fluid inclusions and/or hematite (Walker, 1984). Under SEM and BSEM, the albites reveal two main varieties of textures: 1) Numerous tiny euhedral albite crystals growing within leached K-feldspar grains: 2) blocky, euhedral albite crystals forming pseudomorphs of detrital K-feldspar and lacking any dissolution porosity. Iypg_1- This type of albitization.is common in.the upper parts of the New Haven and parts of the East Berlin Formations. Saigal gt 31., (1988) found this type of albitization to be common at depths between 2.2 and 3 km (65 degrees to 90 degrees celsius). Albitized feldspar of this type shows few to numerous euhedral albite crystals growing within leached K-feldspar grains of a delicate skeletal structure (Figure 48). The albite crystals vary in size from about 2 to 25 microns and show sharp edges and corners. The crystal faces are smooth and most of the albite crystals show growth parallel to the cleavage planes of the parent feldspar grain and, accordingly, are preferentially oriented (Figure 49) . Scattered growth of only a few tiny albite crystals within a Figure 47 Photomicrograph‘ showing albitized K- feldspar grain resembling chessboard albite. Blocky and tabular dark gray patches are albite (Alb) while light gray -yellow areas represent relict K-feldspar (Ksp). Sample # NH-3-15. Frame dim.: 2.5 mm x 3.8 mm SEM photomicrograph of $5731 albite‘_‘ showing delicate skeletal structures of a leached K-feldspar grains. Sample # EB—l-lz. Bar scale = 100 um. Figure 48 Figure 49 Enlarged SEM view showing parallel oriented albite crystals (arrows) within K-feldspar host. Sample # NH-3-36. Tic mark = 10 um. Figure 50 SEM photomicrograph of type 2 albitization showing no intracrystalline dissolution,porosity. Sample # NH-4-2. Tic mark = 100 um. 123 significantly leached K-feldspar grain is also common. Such leached K-feldspar grains retain their delicate skeletal structure, suggesting that their dissolution has occurred in situ after early burial compaction, Boles (1982) , Gold (1987) and Saigal gt 31. (1988) reported similar dissolution textures in partly albitized plagioclase grains in sandstones from the Gulf Coast and offshore Norway. The tiny albite crystals in notably leached K-feldspar grains can easily be overlooked in a rapid SEM examination, particularly when viewed under low magnification. HES—2.- Pseudomorphic replacement of detrital K-feldspars by blocky albite crystals is usually seen in samples from the lower parts of the New Haven Arkose, particularly the basal unit that overlies the Milford Chlorite Schist (stop 4) . Albite crystals are generally less numerous but bigger and more massive in appearance than those in type 1. Like type 1, albite crystals show typical smooth surfaces and sharp edges and corners. There is very little or no intracrystalline dissolution (Figure 50) . Boles (1982) observed a lack of dissolution textures in completely albitized plagioclases. Close SEM examination reveals that albite starts growing simultaneously at several places in a preferred direction, along cleavage planes of the parent grain (Figure 51) . With continuous growth, coalescence of individual albite crystals takes place, and eventually, a pseudomorph of detrital feldspar is formed (Figure 52) . Partial to complete stages of albitization can be seen within ' I . . ..g. out, ' Wt ‘4 4 n “ I'V‘ ' I a . '- .‘k ”j.. ‘ \' . ¢ _ 1 ' .; 4' ‘ \ I, g I) .1 ‘1); 1,, "_ " _ Figure 51 SEM photomicrograph showing pseudomorphic replacement of K-feldspar by blocky albite crystals. Notice the preferred orientation of albite along cleavage planes of parent K-feldspar. Sample # NH-2-6. Tic mark = 100 um. Figure 52 SEM photomicrograph showing detrital feldspar pseudomorph formed by continuous growth of individual albites. Sample # NH-2-6. Tic mark = 10 pm. 125 a single thin-section. ALBITIZATION OF DETRITAL PLAGIOCLASE Albitization of plagioclase is not quite so obvious as albitization of K-feldspar. Several grains were examined and show partial albitization. Random examination of contrast- mottled grain under BSEM imaging reveal that albitized plagioclase is not as common as albitized K-feldspar. In the few grains investigated in this study, most of the plagioclases are twinned, although absence of albite twinning is common for albitized feldspars of diagenetic and igneous or metamorphic origins (Boles, 1982) . However, individual albite crystals in diagenetic pseudomorphs may display twinning (Morad gt 31., 1990). Albitization of plagioclase starts preferentially along microfractures (Figure 53). The diagenetic albite is optically clear and in many samples, optical orientation of the albite follows the orientations of the two sets of twin lamellae in the plagioclase. Morad gt 31. (1990) mentioned that without careful microscopic examination, these albite pseudomorphs can easily be misinterpreted as unaltered detrital plagioclase. SEM and BSEM studies shows different tones of gray color, detrital plagioclase is light gray and albitization is dark gray (Figure 53) , due to the variation in the average atomic number between detrital and albitized parts. 126 Figure 53 ESE image showing a detrital plagioclase grain (light gray) replaced by albite (dark gray). Notice the different range of gray tones within the grain. Also, notice that albitization starts along microfractures in the detrital plagioclase. Sample # NH-3-l6. Bar scale = 100 um. 127 ELECTRON MICROPROBE ANALYSIS Figures 54a, b, and c summarize the different feldspar compositions in the Hartford Basin sediments. Microprobe analysis of detrital K-feldspar show composition of a nearly pure orthoclase end member (Figure 54c). Probe analysis of albitized K-feldspar (e.g., sample NH- 3-16: stop 3) indicate that the diagenetic albite is pure (Ab = 94 to 99%), (Appendix A). However, diagenetic albite deviates somewhat from formula of ideal albite, particularly by having high total sum of K‘ + Ca” (Ab,,._00r5.oAn1_o) . Analysis performed on the remnants of detrital plagioclase and the albitized part of it, shows An composition higher than the albitized part (Aha-SOrLTAnmJ) , (Appendix B). This suggests a gradual decrease in An towards the domains of pure albite composition (Appendix A and B: sample NH-3-16), therefore suggests that albite has been formed by replacement of the plagioclase rather than.by simple void filling (Boles, 1982: Pittman, 1988). This is supported by the presence of remnants of plagioclase within the domains of diagenetic albite (Figure 53). ORIGIN OF ALBITIZED K-FELDSPARS Diagenetic versus detrital origin of the albitized grains in sandstones has been the topic of considerable discussion (Lajoie, 1973: Walker, 1984) since the publication of Middleton's (1972) paper on albite of secondary origin in the Charny sandstones of Quebec. Detrital albite grains as well 128 Or 0 N.H.FM. (STOP 4) A N.H.FM. (STOP 3) 90 + N.H.FM. (STOP 2) o E.B.FM. (STOP 1) 80 70 60 50 40 30 20 \l \l \l \l \l \l \l \l Ab Figure 54a. Ab Or An ternary 60 7O 80 90 An plot showing the compositional variation of microprobe analyses (Appendix A) of albitized K-feldspar in the Hartford Basin (modified after Deer, and Zussman: 1963). Howie, 129 Or 0 N.H.FM. (STOP 4) go A N.H.FM. (STOP 3) + N.H.FM. (STOP 2) O 5.3m. (STOP 1) 80 70 60 50 40 30 20 10 6 ° 3 n'. ,; V v V V V V V _ Or Ab An ternary plot showing compositional variations of the microprobe analyses (Appendix B) of detrital plagioclase feldspar in the Hartford Basin. Figure 54b. 130 Or 0 N.H.FM. (STOP 4) A N.H.FM. (STOP 3) + N.H.FM. (STOP 2) O E.B.FM. (STOP 1) 7O 50 50 4O 30 20 10 \/ \l \/ \l \/ \/ 10 20 30 50 7O 80 90 Ab An Figure 54c. Or Ab An ternary plot showing the compositional variations of probe analyses (Appendix C) of relict K-feldspar in the Hartford Basin. 131 as authigenic albitized K-feldspar were observed in the studied formations of the Hartford Basin. Saigal gt 31., (1988) established a combination of petrological and chemical characteristics to prove that albitization has occurred in situ during burial diagenesis. Many of their criteria fit perfectly the Hartford Basin albites. The evidence is as follows: 1) Crystal Morphology SEM studies reveals that albite crystals in both of the albite textural types are nearly euhedral with sharp edges and corners and smooth crystal faces. If this albite had formed in the source area, the crystals would have subjected to some chemical and physical alteration during weathering in the source area, and transportation. Also, albitized K-feldspar grains show delicate skeletal structures that suggest that dissolution has occurred in situ. Particularly, sharp crystal edges and corners, having the highest free energy, are the most susceptible to dissolution. Also, crystal edges and corners are expected to be rounded during transportation of the albitized grain from the metamorphic source rock area. 2) Twinning All of the albitized grains are untwinned. Absence of twinning is considered an important feature of diagenetic albite (Kastner, 1971: Kastner and Siever, 1979: Saigal gt 31., 1988). As revealed by SEM studies, albite nucleates at several places on the parent K-feldspar grain and eventually individual albite crystals grow and converge to form untwinned 132 albite pseudomorphs (Walker, 1984). The partially albitized grains resembling chessboard albite reveal on close examination that the checkered pattern is caused by compositional inhomogeneity and not because of albite twinning (as described earlier). Lack of chessboard twinning in albite pseudomorphs also confirms that the checkered pattern in partially albitized grains is not due to typical chessboard twinning. Texturally, the classic chessboard albite shows more regular, uniformly thick, parallel, and sharper extinction patterns than those described by the partially albitized grains (Starkey, 1959: Walker, 1984: Gold, 1987: Saigal gt 31., 1988). Moreover, most studies suggest that the chessboard albite forms by the replacement of K-feldspar involving the combination of external and internal stresses and inherited characteristics of“ the ‘potash feldspar lattice in ‘the replacing albite (Starkey, 1959). In contrast, the albite replacement in the Hartford Basin sandstones is clearly a low-temperature, dissolution-reprecipitation process, not a high-temperature metamorphic recrystallization, which is discussed later in this chapter. 3) Composition Microprobe analyses show that albite is almost pure (Ab = 96.1 to >99.8%), irrespective of textural type (Appendix A: Figure 54a). This chemical purity also suggests a diagenetic origin for the albite (Kastner, 1971: Kastner and Siever, 1979: Boles, 1982 and 1984: Walker, 1984: .Morad 1986). 133 Microprobe data show that replacement albite and albite overgrowth are similar in composition (Ab - 99.1 to 99.9%), (Appendix A: Figure 54a). Detrital plagioclase has a different composition (AbMJAanruJ) , (Appendix B: Figure 54b). This similarity in composition between albite overgrowth and replacement albite provides good evidence that albitization has occurred during burial diagenesis and is not a feature inherited from the clastic grains. 4) Inclusions The presence of abundant minute dusty inclusions is another characteristic of albitized grains (Ogunyomi gt 31., 1981: Boles, 1982: Walker, 1984: Saigal gt; 31., 1988). Petrographically, their grayish white appearance under reflected light suggests that are only vacuoles. 5) Change in Albitization with Depth A plot of point counting data of % albitized K-feldspar versus depth (Figure 55) shows that albitization starts near 1.5 km (lower parts of the East Berlin Formation) and reaches a maximum by 3.5 km, where nearly complete pseudomorphic replacement is more common. This increase of the percentage and degree (partial to complete) of albitized K-feldspar with depth also suggests that albitization has taken place during burial diagenesis. The less abundant albitization in the basal New Haven Arkose (stop 4), which.was most deeply buried (> 3.5 km), suggests that burial depth alone is not the only factor that controls albitization. 134 Figure 55 Plot of the percent albitized K-feldspar grains (from point counts data) versus depth in the New Haven and the East Berlin Formations. Trend showing increase in albitization with increase in depth. 135 fl 8 a .0 m m a m c m A n a. m o. u. u. n” E I M I e a + o (.J((.«aa((1q(....1414q.......4 a......413....<««14q1411q..qad11 (q4a<<..aqhhbfibbbbbpbohhbbhbb>>>b PDDDhDDDPhDPFFDDDDDPDDFLDDDDD} bEDDDDDbDFHDILDLH’Pdt'bbFFF? Libb.)t}b?>bbbi?bi.bb>bbh’bbbbbbba m “w w Aw w “a m .u m w ma a N “w w ma a m" 0 ”w w «W n mu a mu 0 .e Ihawo .e Ihdwo .E xpdwo .2 theme 20 x ALBITIZATION Figure 55 SEM examination of albitized grains clearly shows that albite nucleates at several sites on the parent K-feldspar grain (Figure 50). Eventually, these individual crystals grow and coalesce to produce albite pseudomorphs (Figure 51). The sharp contacts between relict K-feldspar and pure albite crystals support the suggestion of Boles (1982) that albitization proceeds by a dissolution-precipitation mechanism. The fact that albitized grains of the New Haven Arkose at greater depths (> 3.5 km) lack dissolution textures, while at shallower depths (< 2 km) the albites of the East Berlin Formation show abundant dissolution textures, suggests that the rate of K-feldspar dissolution versus albite precipitation may be responsible for the resulting albite type. It is believed that K-feldspar dissolution has been more rapid than albite precipitation during the formation of type 1 albite, while a balance between the two would favor the formation of type 2 albite. Saigal gt 31. (1988) suggested that the rate of albite precipitation increases at greater depths due to higher temperatures and replacement of K- feldspars by pseudomorphic albite (type 2) is favored at greater burial depths (> 3.5 km). Aagaard gt 31. (1990) supported the view of Saigal gt 31. (1988), that albitization of K-feldspar is going on these sandstones at burial temperatures between 65 and 125'C. However, rates of dissolution also increase with temperature and the existing data indicates that both K-feldspars and albite have the same 137 activation energy. Therefore Saigal's explanation is probably not favorable. Albitization of plagioclase at an earlier burial stage than for K-feldspar has been observed by Kaiser (1984) and Milliken (1989) in the Oligocene Frio Formation of Texas Gulf Coast. Land and Milliken (1981) found that the zone of K- feldspar disappearance is between 3,600 m and 4,200 m (130- 150'C) in the Frio Formation. Gold (1987) observed that in sandstones from Louisiana Gulf Coast the K-feldspar is unaltered at depths shallower than 4,800m (125'C), whereas the plagioclase is albitized. Morad gt 31. (1990) reported that albitization of detrital plagioclase has been accomplished by dissolution-precipitation processes at about 75-100'C. Thus, there is a similarity in the diagenesis behavior of detrital feldspars between some of the Gulf Coast sandstones and those of the Hartford Basin where minor albitization of K-feldspars were observed in the East Berlin Formation (<120'C) (Pratt gt 31., 1988). As depth increased more K-feldspar albitization were noted (Figure 55), except in the basal part of the section. A mechanism for the removal of potassium and supply of sodium is required for the dissolution of K-feldspar and precipitation of albite. If albite precipitation was homogeneous on.K-feldspar grain surfaces, then replacement of K-feldspar will take place only on grain surfaces forming thin rims of albite. Such rims will act as shields and preserve the remaining part of the clastic K-feldspar grain. 138 Microporosity observed between authigenic albite crystals may have acted as pathways for the outward diffusion of K? from the K-feldspar core and inward diffusion of Na‘ to form albite. Accordingly, during the deep burial of the New Haven Arkose, these micropores may have mended to produce a tight authigenic Na-feldspar. Replacement of K-feldspar by albite can be expressed by the following reaction: 10118130, + Na’ - NaAlSi3OB + K‘ (1) This reaction is believed to be essential in producing type 2 albitization where byproducts and dissolution textures are absent. Middleton (1972) and Walker (1984) suggested a similar direct replacement mechanism. The presence of intracrystalline dissolution textures associated with type 1 albite (Figure 48) in the East Berlin Formation suggests that replacement of detrital K-feldspar in the East Berlin Formation is not.by equal volume. Part of the dissolution texture may have formed during feldspar leaching by meteoric water (i.e., before albitization), while some could be due to albitization. Some of the Al and K released during albitization can be incorporated into illite. Alteration of smectite to illite consumes K’ produced from reaction (1) , and releases Na‘ that is likely to contribute towards albitization. The growth of albite crystals along the K-feldspar cleavage planes suggests that the replacement is. guided. by’ cleavage planes. Perhaps cleavage surfaces have greater free energy or higher 139 dissolution rates. Also, albitization is enhanced along grain fractures where fluid can easily infiltrate. Boles (1982) and Milliken gt 31,, (1985) mentioned that surface dissolution kinetics, lattice defects, and plutonic versus volcanic origin of K-feldspar are other factors that could be critical for the albitization process. The fact that albitization is more pronounced lower in the section (> 3.0 km) suggests that higher temperatures are favored. Type 2 albitization of the New Haven Arkose, forming complete pseudomorphs with no dissolution textures, is likely to occur under faster rates of nucleation and crystal growth of albite. The higher the temperature the faster would be the rates nucleation and crystal growth. This may account for the dominant occurrence of type 2 albites at greater depths (> 3.0 km). The absence of prominant albitization at stop 4 is a puzzling question because the QFR data (Figure 7a) show that the total feldspar is the same at stop 4 as at stops 2 and 3. Also the percent K-feldspar decreases with the increase of chlorite at stop 4 (Figure 40). But this does not mean that the feldspar at stop 4 is mainly unalbitized plagioclase, as evident by the low content of plagioclase at stop 4 (Table 1 and Figure 7c), i.e. the decrease of K-feldspar relative to the increase of chlorite does not mean the plagioclase content should be higher than K-feldspar, but it means that K-feldspar was altered to mica (illite) or that K moved out of the system. 140 More than one reaction can be written to express albitization of plagioclase. Due to low mobility, Aly'might be conserved in these reactions. Land (1984) suggested the following reaction: Anorthite + 2Na’ + 411,310, .. 2Albite + Ca‘ + 8820 (2) According to this reaction, the volume of albite produced upon albitization of plagioclase is twice the volume of anorthite component. The presence of albite overgrowths formed in the Hartford Basin sandstones, the lack of microporosity in the albitized plagioclase, and the presence of zeolite in the New Haven Arkose indicate that this reaction might be important. Another explanation is that kaolinite was formed as a byproduct of the albitization reaction proposed by Morad gt 31. (1990): Anorthite + HCO3 + H+ + H20 - Kaolinite + Calcite (3) K? released from albitization of K-feldspar is used in the illitization of kaolinite: 2 K-feldspar + 2.5 Kaolinite + Na+ -» Albite + 2 Illite + 2 Quartz + 2.5 1120 + 11“ (4) The small amounts of kaolinite formed in these sandstones indicate that reactions 3 and 4 may not have been important. Win The sources of sodium needed for albitization in the Newark Supergroup are not clear (Oshchudlak and Hubert, 1988) . Generally, high sodium concentrations are not necessary for albitization (Schwartz and Longstaffe, 1988). Several 141 possible sources of sodium are proposed for the sandstones of the Hartford Basin. Perhaps much of the sodium was provided by mobile pore fluids with substantial flow rates that carried sodium from outside the basin (Hubert and Meriney, 1988) . In this model, heated water rose through the basin fill, transporting dissolved sodium obtained from crystalline rocks beneath the basin. Again, the near absence of albitization at stop 4 could be due to the rapid filling of the basin with sediments that the albitization reaction never had enough time to be completed. The East Berlin Formation shows little evidence for albitization and authigenic albite, whereas the New Haven Arkose is dominated by both. A satisfactory explanation might be that the New Haven Arkose was more deeply buried than the overlying East Berlin Formation and that explains why it has the highest proportion of highly altered plagioclase grains and the most albitized K-feldspar and authigenic albite. The plagioclase grains are altered, but not cavernous or skeletal, so it is likely that dissolution of plagioclase grains was volumetrically a minor source of the sodium needed for albitization. \ Also, some sodium may have been released during conversion of smectite and interlayered smectite/illite to illite (reaction 1, Chapter 4: Hower gt 31., 1976) . My data show that samples of the New Haven Arkose (stop 3: Figure 5b) from within several meters of the dolerite dike are slightly more albitized than those away from the dike near 142 the bottom of the section. The thermal gradient created by the dike may have promoted migration of sodium ions towards the higher temperatures. Van Houten (1965), in his study of the Lockatong Formation in the Newark Basin, estimated this temperature to be between 350 and 700'C. .Another possibility is that some sodium may have moved in hydrothermal solutions associated with emplacement of the sill in a manner similar to that suggested for arkoses in the Hartford Basin by Heald (1956). C8LORITES This chapter is focused on the discrimination of different types of chloritic clays in the fluvial and lacustrine rocks of the New'Haven and East Berlin Formations, Hartford Basin. This includes the identification and distribution of detrital and authigenic chlorite, polytype analyses, diagenetic history versus burial depth, and origin of the various types of chlorite. The New Haven Arkose contains abundant chlorite of both authigenic and detrital origin, whereas the East Berlin Formation is dominated by detrital chlorite (Chapter 3 and 4). Flakes of detrital chlorite generally occur in discrete laminae, often aligned along bedding planes, as matrix, or as reworked mudstone clasts. The authigenic chlorite occurs as thin isopachous coatings around detrital grains, as a pore- filling cement, and occasionally as a pore-lining cement that is absent at grain contacts. As mentioned earlier, the petrographic studies show the presence of a number of cements in addition to chlorite, including quartz overgrowth, feldspar overgrowth, calcite, dolomite, and local zeolite cement. In the East Berlin Formation, there is an inverse relationship between the amount of dolomite and the minor amount of chlorite cement (Figure 56) . Textural evidence suggests that the grain-coating (chlorite-vermiculite) and pore-lining chlorite formed very 143 144 % CHL. VS DOL. fi ' 30 3 5.3.94. (STOP 1) ‘ % CHLORITE o LQSg~LL % DOLOMITE 10 Figure 56 Variation in the dolomite versus chlorite in the sediments of the East Berlin Formation. 145 early in the diagenetic sequence (Chapter 3) . This would imply according to Hower gt 31. (1976), that it was formed during or after significant illitization of smectite. The more widely occurring pore-filling chlorite which occurs only in the New Haven Arkose relates to a later event during burial (Chapter 3) . This may account for the near absence of chlorite cement in the shallow sediments of the East Berlin Formation. The following is a detailed description of the morphology of the different authigenic chlorite textures as shown by petrographic, SEM, BSEM and EDS techniques. This will be followed by XRD and polytype study of different types of chlorite as an attempt to interpret their mode of origin. MORPHOLOGY OF AUTHIGENIC CHLORITE Three main varieties of authigenic chlorite were encountered in the basin: grain-coating, pore-lining and pore- filling cements partially cementing in between detrital feldspar grains. In thin-section all forms of chlorite are pale green in color under transmitted light and show gray- yellow birefringence colors in polarized light. Distinction between grain coating and pore-lining chlorite is based upon the presence or absence of chlorite at grain contacts (Wilson and Pittman, 1977) . Microscopic investigation shows that grain-coating is present on and between grain contacts (Figure 57), whereas pore-lining chlorite is absent at grain contacts (Figure 58). Figure 57 Grain-coating chlorite rimming around detrital grains and in between grain contact (arrows). Notice a later generation of chlorite cement within the voids. Sample # EB-1-25. (Frame dim.: 1.0 mm x 1.5 mm) Figure 58 Pore-lining chlorite covering different detrital grains, but absent at grain contacts (arrows). Sample # NH-4-6. (Frame dim.: 1.0 mm x 1.5 mm) 147 This form of chlorite-vermiculite mixed layer (corrensite) is very distinctive and it is only observed at stop 1 of the East Berlin Formation. The corrensite crystals have grown perpendicularly onto the host grains forming an isopachous rim of cement. Under the electron microscope, the enveloping corrensite typically shows slightly curved or crenulated plates (Figure 59) , arranged in a cellular or honeycomb pattern. Individual crystal plates may not always be resolved. In this form, chlorite resembles the crinkly morphology of mixed-layer chlorite/vermiculite (corrensite) that probably formed from a chlorite-smectite precursor (Tompkins, 1981: Helmold and Van de Ramp, 1984: Humphreys gt 31., 1989) , but a non-swelling chlorite structure can be confirmed by XRD (sample 4 EB-l-ll, Table 4). W This form of chlorite is confined to few samples from stop 4 of the New Haven Arkose. Generally, this chlorite consists of idiomorphic chlorite platelets arranged in a rosette-like pattern on a plagioclase feldspar grain (Figure 60), typically 3-8 microns in maximum dimension as evidenced by SEM. Petrographic examination revealed the presence of two generations of superposed pore-lining chlorites. Pale green chlorite fringes grow perpendicular to the substrate grains and line the pores, in contact with a finer green chlorite filled with dark inclusions (Figure 61). 148 Figure 59 SEM photomicrograph showing crenulated plates of chlorite-vermiculite grain-coatings of detrital framework. Sample # EB-1-25. Tic mark = 100 um. ‘3 .—— Figure 60 SEM photomicrograph showing euhedral rosette-like platelets lined on a detrital plagioclase feldspar grain and growing towards the pore. Sample # NH- 4-2. Tic mark = 10 um. Figure 61 Photomicrograph of multiple pore-lining chlorite superposed one on top of the other. Sample # NH- 4-1. (Frame dim.: 0.4 mm x 0.6 mm) 150 W This form of chlorite usually consists of subhedral to euhedral crystal plates arranged in a haphazard face-to-edge cardhouse arrangement. Some pores are totally occluded, whereas adjacent pores may remain empty (Figure 62). Sometimes the cement forms fan-shaped clusters of crystals (rosettes) up to 10 microns in diameter. Samples from stop 4 are dominated by this type of cement, however a few samples from stop 3 of the New Haven Arkose show its presence. X-RAY DIFFRACTION Some chlorite-rich specimens are recognizable petrographically, but most are only revealed by x-ray analysis of clay mineral suites. XRD analyses were taken on the <2 micron fraction of both sandstones and mudstones from the four stops of the studied formations. Throughout the succession the mudstones record a detrital clay assemblage of chlorite and illite with variable amounts of mixed-layer chlorite- smectite and chlorite-vermiculite (other clay minerals are discussed.in.Chapter'4). EDS analysis shows that.the detrital chlorite is mainly Mg-chlorite (clinochlore species) (Figure 63). The authigenic chlorite was found to have weak and broad (001) 14 Angstroms and (003) 4.7 Angstroms reflections, but the (002) 7 Angstroms reflection and the (004) 3.55 Angstroms reflection were very sharpTand intense (Figure 64). The small broad (001) reflection was largely unaffected by glycerol- 151 Figure 62 SEM photomicrograph showing pore-filling chlorite cement. Sample # NH-4-1. Tic mark = 10 um. 152 ( 11111111111111]!11111111111111lllLlJlllllllLlllllJ - r- -—( 9" H (D .1 C _. )— (3 Z I.“ IL —-4 )- [IllIIIWIIIIIIIWTIIIIIIIIITIIflIIIIIIITIIIIIIIII Do -— N 0 Q n 0 N O 0 O I: —. Figure 63 EDS pattern showing relatively Mg-rich chlorite at stop (4). Sample # NH-4-6. 153 3.55 13.62 $813 degree: 20 Figure 64 XRD pattern of the authigenic pore-lining clay assemblage showing the marked differences in intensity of the (001) and (002) basal reflections of chlorite and the slight shift in spacing of the (001) reflection after heating; Illite/smectite (I/S) is also recorded. Sample # NH-4-1. 154 solvation, although a slight reduction in intensity was noted. When heated to 500 degrees celsius, the (002) reflection decreased slightly in intensity. On the basis of XRD alone, the chlorite has suppressed (001) reflections that, in the absence of chemical data, would be characteristic of a typical chamosite structure (Wilson, 1987). Auweak, low intensity 001 reflection and intense (002) reflection would seem to be a characteristic of authigenic chlorites (Wilson, 1987: Humphreys gt 31., 1989). ELECTRON MICROPROBE ANALYSIS Use of an electron microprobe allows the chemistry of the chlorites, in particular the relative amounts of Fe, Mg and Al, to be determined. There are limitations to these analyses. The principal drawback is that the probe can not separate ferrous from ferric iron. Another serious problem results from the fine grain size of the authigenic chlorite and its common occurrence coating detrital grains: it is often difficult to direct the beam onto the clay plates without probing the host detrital grain or other contaminants because the volume analyzed (the surface area, about 2 microns in diameter, and also the depth of penetration into the sample of about 5 microns) is often greater than the dimensions of individual clay particles (Humphreys gt 31., 1989). With respect to spatial resolution, probe analyses are thus inferior to those obtained from analytical transmission electron microscopy (ATEM) . Minor discrepancies in chemical 155 analyses might occur between the two techniques because of normalization of data with ATEM. Finally, there is the possibility of minerals such as hematite becoming attached to the clay plates and adversely affecting the measured Fe:Mg:Al ratios (Curtis gt 31., 1984). Given these difficulties, seven authigenic chlorite samples were probed. Whittle (1986) estimated the compositions of authigenic chlorite from XRD data using the equation after Brindley (1961) and Shirozu (1958). The regression. equation of Brindley (1961) allow the estimation of chlorite tetrahedral compositions to within 10%, or 0.1% A1. He estimated the octahedral composition to within 10% Fe using the regression equation after Shirozu (1958), providing the species are trioctahedral. Post and Plummer ( 1972) investigated IIb chlorites from Flagstaff Hill, California by XRD, DTA and IR spectroscopy and found that Brindley's equation gave a good correlation between tetrahedral Al and basal spacing. However, Whittle (1986) concluded that the compositions of the Ib chlorites derived by calculation from XRD are not the same as compositions of the same material determined by TEM/EDS. He reported major differences in compositions between both methods for’ both. the ‘tetrahedral and. octahedral sheets. Therefore, caution should be exercised when estimating the composition of sedimentary chlorites by XRD. Probe analyses for a total of seven samples from the New Haven Arkose and the East Berlin Formation are summarized in Appendix D. .Although authigenic chlorites of similar optical 156 characteristics have commonly been described in the recent literature (Hayes, 1970: Curtis gt 31., 1984, 1985), there is considerable variation in their reported chemical compositions (Appendix D). In this study, variation in composition of authigenic chlorite were detected within the same polished thin-section (e.g. sample NH-4-2: Appendix D). Compared to the average structural formula for the authigenic chlorites recorded in the literature (Boles and Franks, 1979: Curtis gt 31., 1984, 1985: Whittle, 1986), the Triassic New Haven Arkose chlorites (stop 4) are notably Si- rich and include high amounts of Mg. However, other samples representing East Berlin grain-coating chlorites are equally Mg-rich. CHLORITE POLYTYPE ANALYSES Generally, the various polytypes of a given species result from.different ways of stacking identical layers. The (001) reflections for any stack of such layers are identical: the differences appear mainly in the hkl reflections. The best way of determining polytypes is by comparing the XRD pattern of an unknown with standard patterns. A ripidolite chlorite (Ib type) sample number CCA-l from Flagstaff Hill, El Dorado County, California, was used as a clay standard for the polytype study. Mixtures of two polytypes, or presence of additional ‘minerals, can. create. 200'C. On the other hand, they reported the presence of laumontite at temperature between 100-190'C. 'They concluded that.generally chlorites reflects a higher metamorphic grade than laumontite. 167 ‘LL _ I. Figure 68 Photomicrograph showing fan-like terminated clay due to the breakdown of mica. Sample # NH-4-6. (Frame dim.: 0.16 mm x 0.24 mm) C8APTER 7 EEOLITES Zeolites are among the most common authigenic silicate minerals found in unmetamorphosed sedimentary rocks (Hay, 1966 and 1978). Zeolites are hydrous aluminosilicates consisting of a tetrahedral framework.of O atoms surrounding either a Si or an Al atom extended in three-dimensional network, which typically provides structural channels (Zelazny and Calhoun, 1982). Ghent (1979) defined the zeolite facies to bridge the gap between diagenesis and metamorphism. He concluded that the zeolitic assemblages can form under conditions ranging from seawater-sediment interface to contact metamorphic aureoles. Previous studies have proven the occurrence of two main types of zeolites in the sandstones of the Hartford Basin. Heald (1956) reported that many arkoses in Hamden and northern New Haven, Connecticut, contain a considerable amount of the laumontite variety of zeolite. He noticed that in some specimens the zeolite fills pore spaces and partly replaces the feldspar. He concluded that laumontite was formed after at least initial compaction of the sediments as it occupies cracks in fractured detrital grains and surrounds deformed mica. Van Houten (1962) found analcime in some sandstones in the Triassic Lockatong formation of the Newark Series rift- valley sediments. April (1978) also found analcime in the 168 169 black shale and gray mudstone of the lacustrine sediments of the East Berlin Formation. In this study, two varieties of zeolite were found in the studied formations of the Hartford Basin. Analcime is only present in. the upper gray ‘mudstone of the East Berlin Formation, whereas laumontite is present in two stops of the New Haven Arkose. LAUMONTITE Laumontite has been identified in only seven samples from stop 3 and four samples from stop 2 in the middle and upper parts of the New Haven Arkose. Laumontite was not detected in stop 4 of the New Haven Arkose or in the East Berlin Formation. laumontite was identified principally by thin-section petrography, and later confirmed. by XRD, SEM, and EDS techniques. Microscopically, its color is mainly light yellowish-gray to optically clear, of low-birefrengence, with well-developed.cleavage and undulatory extinction. It occurs as pore-filling cement interstitial to framework grains. It also occurs as partial replacement of detrital plagioclase grains. Laumontite pore-fillings are partially surrounded by earlier-formed hematite and authigenic clay or silicate (mainly quartz) overgrowth, suggesting that laumontite is late in the paragenesis (Figure 69) . laumontite cement may be optically continuous with laumontite replacing detrital 170 Figure 69 Photomicrograph laumontite pore-filling cement and replacement of feldspar. Sample # NH-3-10. (Frame dim.: 1.0 mm x 1.5 mm) 171 feldspar, and where replacement is pervasive, distinction between the two modes is especially difficult. Laumontite replacement of detrital plagioclase varies from incipient alteration to complete replacement, and is the most common mode of occurrence of laumontite. Where replacement is extensive, the laumontite is usually murky brown and contains inclusions of sericite ('2) and epidote inherited from the plagioclase precursor. XRD'diffractograms show the diagnostic intense laumontite peak at 4.15 Angstroms and the characteristic peaks at 3.5, 9.40-9.42, 3.26, and 6.84 Angstroms (Gude, 1981) , (Figure 70). Under the SEM, laumontite appears as a blocky pore-filling cementing detrital quartz and feldspar grains. Chemical analyses of laumontite in low-grade metamorphic rocks indicate that the zeolite is typically free of sodium and potassium and is near ideal compositions, Ca(Alzsi,O12).4H20 (Ghent, 1979: MUmpton, 1981). The laumontite of the New Haven Arkose has the typical composition according to EMP analysis (Appendix E). EDS analysis also indicates that laumontite is composed of the major elements Ca, Si and Al (Figure 71) . EDS pattern of laumontite matches perfectly those given by Welton (1984) . WW As evident by optical microscopy, laumontite crystallization postdates the formation of all other authigenic minerals except calcite. Laumontite replacement of detrital grains, and its sharp boundary relationships with silicate overgrowths and authigenic clay rims, all support its 172 39 30 10 42 Figure 70 XRD pattern of random powder sample showing the distinctive peaks of laumontite along with illite. 173 1111]] III] III] IIIJIIJJJ Ill] 11]] 1111 LIJJ ll 81 AL CA fl. II]! [III [1'1 r1] ac .- N 4“) V D ‘0 B O 0~ O u Figure 71 EDS spectrum showing characteristic elemental composition of laumontite (Ca, Al, and Si). Sample # NH-3-10. 174 late origin. The presence of laumontite is often taken to indicate low-gradetmetamorphic(conditions (pre-greenschist facies) and thus its thermal stability limits are of interest (Boles, 1981). Boles (1981), after Seki gt 31. (1969), reported the apparent formation of laumontite at 75 i 5°C in the Katayama geothermal field, Japan. However, if laumontite is authigenic, it may have formed at temperatures considerably lower’than.described.above (Boles, 1981). The range and upper thermal stability limit are better known. Hoffman and Hower (1979) reported the presence of laumontite in the faulted disturbed belts of Montana, at temperatures between 100- 190°C. Ghent (1979) agreed with their temperature ranges and added that laboratory tests show possible formation of laumontite at temperatures up to 185°C. In the laumontite-producing reaction the anorthite component in detrital plagioclase, with the addition of silica and water, is converted into laumontite: albite is another product of this alteration (Helmold and Van de Ramp, 1984): NaAlSi303.CaAlzsizoa + 28102 + 41120 - NaAlSi303 + CaAlZSi,O12.H20.4HZO (5) One possible explanation of the formation of laumontite can be due to the variation in the pore-fluid chemistry and fluid pressure. One possible model to explain the variation in fluid pressure between petrologically similar sandstones requires the formation of laumontite in a overpressured zone, a zone where diagenetic reactions proceeded very slowly 175 because of the rate of pore-fluid throughput (Hayes, 1966). Overpressuring may have occurred in the New Haven Arkose during the time of laumontite formation: this is supported by the fact that laumontite is restricted to the deeply buried New Haven Arkose (stop 3 and 2) and was not detected in the East Berlin Formation” In ‘this situation, pore fluids enriched in Na? from the dewatering of smectite-rich shales deliver enough Na+ to the sandstones to allow albitization of feldspars and possibly of some calcium-bearing plagioclase, which in turn supplied Ca+2 necessary for the formation of laumontite. The absence of any calcite cementation or replacement textures in the laumontite rich beds of stop 3 and 2 suggests that all of Ca” was consumed in the formation of laumontite. Boles and Coombs (1977) illustrated the above mentioned process by the following reaction: Plagioclase + 2 $102 + 4 H20 - NaAlSisoa + culzsi,o,2.4nzo (6) Laumontite distribution appears to be controlled by pore- fluid chemistry and post-compaction permeability variation. Compaction, formation of laumontite, and precipitation of late stage calcite are the three principle processes adversely affecting reservoir properties of the New Haven sandstones. The fact that laumontite occupies cracks in fractured detrital grains and surrounds deformed mica indicates that it formed at least after initial compaction of the sediments. Although laumontite may result from alteration of original feldspar in sediments, part of the material for the laumontite in the Triassic may have been introduced because much of it 176 occurs as interstitial filling. The introduced material may be of igneous origin, for laumontite is present in near some disbases in Hampden (stop 3). A possible explanation for the absence of laumontite in stop 4 of the New Haven Arkose may be related to burial depth. Increasing burial depth (and temperature) as we move downscetion toward stop (4) , laumontite become unstable. This implies that the basal New Haven Arkose exceeded the upper thermal stability limit of laumontite ( loo-200°C, Hoffman and Hower, 1979). ANALCIME As mentioned earlier, XRD analysis was the only technique with which analcime was detected. Diffraction patterns show the presence of characteristic peaks at 3.42, 5.59, and 2.92 Angstroms (Figure 72). W128 The fact that analcime (NaAlSi206.HzO) could not be identified in thin-section or with SEM suggests that the mineral exists as a well dispersed cement and may have formed as a direct precipitate from concentrated alkaline solutions (April, 1978: Fuchtbauer, 1983) , or as a syngenetic alteration product of a zeolite or clay mineral precursor (Hay, 1966). Van Houten (1962) found analcime in and associated with some sandstones of the Upper Triassic Lockatong Formation, New Jersey. He concluded that this is due to the deposition of the Lockatong rocks in a lacustrine environment as groups of 177 A A A A Figure 72 XRD pattern of analcime in the Jurassic East Berlin Formation. Notice the presence of chlorite peaks in this sample 178 detrital and chemical cycles related to climate. .Analcime in the Lockatong rocks probably formed at an early stage of diagenesis from a colloidal precursor or aluminosilicate mineral (Van Houten, 1965). Precipitation of analcime in the East Berlin lake water might have occurred as pH values of 9 or 10 were reached in the lake or pore waters as evaporation proceeded (April, 1981). Hay (1966) reported observing precipitation of analcime directly from strongly alkaline (pH = 9.70), sodium carbonate brines in Lake Natron, Tanzania. The lack of any microscopic and SEM evidences of analcime textures limit the knowledge about its paragenetic and diagenetic relationships to the different detrital grains and to other diagenetic minerals. C8APTER 8 SUMMARY A8D CONCLUSIO8S Despite the difference in depositional environment and paleoclimate between the New Haven Arkose and the East Berlin Formation, the paragenetic sequence, in general, shows only minor variations of the diagenetic features between the two. This relates to burial diagenesis rather than depositional facies controls. The only exception to this among the silicates is the presence of analcime, which points to a slightly evaporitic environment of alkaline East Berlin lakes. The variation in the diagenetic features between stops 2, 3 and 4 of the New Haven Arkoses and stop 1 of the East Berlin Formation are believed to be due to stratigraphic and thermal controls. Stratigraphically, the New Haven outcrops~ are arranged in the folowing order, from deeper to shallower: stop 4, 2, and 3 (Chapter 1, 2). The East Berlin Formation is hundreds of meters or more higher in the section than the outcrops of the New Haven Arkose examined in this study. The paragenetic sequence of the studied formations shows a variation in the diagenetic minerals with depth. Stop 4 (depply buried) contains no zeolite and minor amounts of albitization but it has abundant pore-filling and -lining chlorites and calcite: stop 2 has zeolite (laumontite) , albitized K-feldspar, calcite, and late pore-filling chlorite: and at stop 3 (shallower) minor early pore-filling chlorite, abundant albitized K-feldspar, and zeolite (laumontite) are 179 180 present. At stop 1, in the East Berlin Formation, minor amounts of early grain-coating interstratified chlorite, calcite, pressure solution and minor albitized.K-feldspar and zeolite (analcime) are the diagenetic features. It is clear that by increasing burial we move from very minor grain- coating interstratified chlorite towards a gradual increase in chlorite plus zeolite and ultimately large amounts of chlorite. The Portland Arkose is above the oil window (immature), the East Berlin and Shuttle Meadow formations fall within the oil window (mature), and the lower New Haven Arkose below the oil window and in the gas window (overmature), (Pratt gt 31., 1988). This suggests that the East Berlin falls in the temperature range (90°-110°C) whereas the deeply buried New Haven Arkose was subjected to higher temperature (> 110°C).- Throughout the stratigraphic thickness of the New Haven Arkose, facies varies from a zeolite facies (stop 3), to a zeolite/chlorite facies (stop 2), and finally to a chlorite facies (stop 4) with increasing burial depth. Table 5 summerizes the authigenic mineral composition of the four stops of the New Haven Formation and the East Berlin Formation in relation to depth, temperature ranges of metamorphic facies (Hoffman and Hower, 1979: Figure 73), and.burial temperatures from the organic maturation indicies of Pratt gt 31. (1988). This supports the above discussion that by increasing depth the authigenic mineral composition varies the different temperature ranges until it reaches the zeolite (pre- 181 0.oHH A 0.0mmuoh mufiuoaso .m.z e : 0.ommno> oufiuoaao n N O 0.oHH A 0.oo~uooa mueucossqo .m.z m a V a 0.633 A 0.oo~uooa «paucossqq .m.z n 0.oaauom 0.ooanow msfloamca .m.m H Anna"..mm mm nuance mnaoam.suz oammzun .H.z.o .aaumon. 0.9 00242 0.9 Houqa.aao¢ .zm moan mamas .Ousucuomaon can sumac stusn cw coccco cue: nusuocwa ousowanmocwssas owceuwcucs no coauswusb .n ounce 182 l l 1 I I ' 1 == SMECTI TE SHALES ---—--—-——--(IIS) RANDOM -- --(l/S) ALLEVARDITE -——--(IIS) KALKBERG .. — ILLITE 2M MICA -- CHLORITE-- -—-— ? KAOLIN --- K-FELDSPAR =Ibd CHLORITE SANDSTDNES --_. ‘ -..- lb CHLORITE llb CHLORITE--- —— ? HALLOYSITEIKAOLIN d ---__--____--_ KAOLINITE -__..-- ? DICKITEINACRITE .. =--- ? CORRENSITE LAUMONTITE - -- VOLCANICS PREHN ITE -- -- '— PUMPELLYITE - HEULANDITE -- ANALC ITE TEM PERATURE(°C) L l l l l l 50 100 150 200 250 300 350 Figure 73 Correlation of the temperature-dependent mineral assemblages in shales, sandstones, and volcanogenic rocks (after Hoffman and Hower, 1979). 183 greenschist) facies of stop 4. Philpotts' (1990) temperature/pressure diagrams (Figure 74 and 75) , confirm these temperature ranges. Study of paragenetic sequences shows that compaction was the earliest process followed by fracturing of these rocks. The dissolution or albitization of K-feldspars is the main source of K7 for the smectite-illite transformation and for sericitization (?). Sources of Na” for albitization in the East Berlin Formation could be from the alkaline rich lake water and pore waters rich in sodium or it could be supplied from the smectite-illite transformation: in the New Haven Arkose, Na“’ either’ came from.(external sources, or from smectite illitization. The down section increase of pore- filling chlorite (Table 1 and 2) might suggest a local source of Mg” from the underlying metamorphic rocks. Recall that- pore-filling chlorite is late in the paragenetic sequence in the lower New Haven Arkose at stop 4 (Figure 27), and stop 2 (Figure 29). Also, the breakdown of detrital biotite can be a possible source of Mg” in the New Haven arkose. The Mg++ source for the chlorite in the East Berlin Formation could be from the redistribution of Mg++ rich alkaline lake waters and/or early-formed dolomite. Detrital calcite was present in caliche rich New Haven Arkoses, and it has been redistributed and recrystallized to a complex generations of cements. Calcium needed for the formation of zeolites could be from.the redistribution of preexisting Ca" in the caliche: a. minor' part of it came from. albitization of detrital 184 1.2 I 1.1 )— 1.0 - 0.9 )- Grenulite -— 0.4- 0.3— 02— 0.1)— Figure 74 Approximate pressures and temperatu- res under which various metamorphic mineral facies form (after Philpotts, 1990). 185 0.9 '- 0.8-— 0.7— Pressure (0P3) g j 8 g] (11*- 0.0 Figure 75 ACF' (Al Ca Fe) ‘plots of common quartz-bearing mineral assemblages in the metamorphic facies. Boundaries and conditions are the same as in Figure 74 (after Philpotts, 1990). 186 plagioclase. Table 6 is a summary of the possible origin of the important elements of aluminosilicate minerals. Where smectite-illite transformation reaction can produce Na for albitization and K for illitization: 3.9316 + l.57KNaCa2Mg,Fe,A1“Si3BO1oo(OH)20.lOHzO = KMMgZFe,35111223135010,(OH)20 + 1.57Na’ + 3.14Ca“ + 4.28Mg°° + 4.78Fe‘3 + 24.6631“ + 570"“ + 11.4on' + 15.71120 (Boles 8 Franks, 1979) . Other sources for K for illitization and Ca (for laumontite) are albitization reactions of K-feldspar and Plagioclase respectively: A- 1822399231: 10.131308 + Na’ = NaA181308 + K’ (Walker, 1934). 8- 21.391.921.353: Nao.7,Cao.erl1.2,Si2.7soa + 0.23112o + 0.5411‘ = 0.74113111151308 + 0.25Aizsizos(on), + 0.27Ca“ + 0.033102 (Land, 1934). To conclude, I believe that the main diagenetic processes are depth related. The fact that albitization.of K-feldspars is minor at shallower depths and lower temperatures in the East Berlin Formation, with a notable increase towards the deeper parts of the basin (New Haven Arkose) supports this inference. Also, within the New Haven Arkose, the change from laumontite facies (stop 2) to laumontite/ Ib chlorite polytype (stop 3) and finally to type Ib/IIbo can scan cowusaom Hosuwcuouoax IO coaumucmemo .AH copay muasoaoo Sauna (a nauauoano a: .A.Bm s0>cm 302v oueuown 0cm muwuoaco cheuuoo no csooxcoun Home 00003 once (0 .omcaooamcan no cowucuwuwnad In coaucucoamo a ucmfioocamou so .A.sm c0>c= 302v OdomOOHcc Onowacu In caducosscq .Ouauown Houfluuoo no czocxcoum (a coaumuflufiaaa u .nuoomonulm mo sawucuwuwnad no .000003 oommuom 00:00 no Oxca o>wucuooc>0 scum OOPAMOO moasHu once meadow (O ..m moumv acoaoocamam oxen cues coucaoommo mcowuaaom Hmsuocuoucam (0 coflucufiuana< dz .cowuosuoumccuu ouwaaw on oufluomsm (n .cflmcn on» ooflmuco Roam oz oowuuco ucnu mowsHuuwuom dawnoz (c zHono namummom momoozm Banana" .neomoooun 08.2—06st case on» non 00.12500 succeeds no 36.30 canamnom no hues—ace .o canon. 188 Future Studies This study‘ is considered as the opening for later differently directed projects. My main concern in this study was the diagenesis of some aluminosilicate minerals. Further studies can include the complex calcite distribution, isotope study of different diagenetic chlorite types, albitization near and away from igneous intrusions, and detailed study on the zeolite facies in the New Haven Arkose and East Berlin Formation, and may later explore the similarity or differences in the Shuttle Meadow Formation and the Portland Arkose of the Hartford Basin. Also, detailed studies of illite-smectite interstratification is strongly suggested. APPE8DICES APPE8DIX A Microprobe analysis of albitized K-feldspar Appendix BAHELE M25) 83° “52°: 8102 2;) CAD no2 880 880(T) BAD TOTAL AB OR New Haven Arkose (stop 4) HE'S'! 12.251 0.011 20.053 68.408 0.010 0.026 0.028 0.023 0.181 0.062 101.054 99.9 0 0.1 nn-4-1 11.495 0.019 20.584 67.320 0.120 0.616 0.003 0.014 0.075 0.041 100.287 96.5 0.7 2.8 189 88-4-2 11.646 0.000 19.674 67.293 0.026 0.056 0.006 0.000 0.043 0.062 98.805 99.6 0.1 0.3 33-4-3 11.588 0.013 19.487 67.057 0.108 0.079 0.009 0.000 0.051 0.000 98.391 99.0 1.0 0 A. Microprobe analysis of albitized K-feldspar. 88-1-3 11.452 0.000 20.281 67.281 0.151 0.628 0.019 0.012 0.015 0.072 99.910 96.3 1.0 3.0 Stop 4 (Cont'd.) 8AMP nag) MGO 111.203 8102 :5) GAO 1'102 FEO(T) BAO TOTAL OR 112-4:4 11.325 0.000 20.097 67.067 0.086 0.659 0.002 0.014 0.073 0.000 99.323 96.4 0.5 3.1 190 New Haven Arkose (stop 3) 10.681 0.028 21.457 66.212 0.112 1.858 0.000 0.028 0.087 0.041 11.851 0.001 20.221 70.073 0.020 0.201 0.004 0.000 0.000 0.000 191 11.700 0.000 19.938 69.294 0.042 0.184 0.034 0.000 0.017 0.021 11.667 0.000 19.904 69.085 0.067 0.250 0.021 0.044 0.022 0.051 11.404 0.008 19.931 68.512 0.098 0.359 0.000 0.032 0.030 0.082 W OR 90.1 1.0 8.9 99.1 0.0 0.9 99.1 0.0 0.9 98.4 0.4 1.2 97.7 0.6 1.7 Stop 3 (Cont'd.) 192 111120 11.243 11.569 11.678 MGO 0.005 0.000 0.000 111.203 19.622 20.023 20.186 6102 65.285 69.341 69.666 1:20 0.379 0.054 0.023 CAO 0.323 0.511 0.414 no2 0.000 0.027 0.020 MNO 0.014 0.002 0.000 230(2) 0.000 0.019 0.009 BAO 0.000 0.000 0.062 Egggn 96.873 101.547 10 57 AB 96.3 97.6 98.1 on 2.1 0.0 0 A8 1.6 2.4 1.9 11.666 0.01 19.978 68.852 0.073 0.225 0.000 0.016 0.000 0.133 5 98.5 0.4 11.078 0.051 20.044 67.928 0.243 0.179 0.029 0.058 0.094 0.000 97.9 1.3 Stop 3 (Cont'd.) 193 N15) 11.868 11.460 8.414 11.821 11.806 H00 0.010 0.009 0.000 0.003 0.002 31.203 19.925 20.072 20.929 20.229 20.207 8102 68.184 68.803 70.277 69.489 69.110 K20 0.079 0.118 0.045 0.043 0.046 CAD 0.171 0.272 0.405 0.314 0.333 TIO2 0.000 0.006 0.039 0,035 0.045 MNO 0.000 0.014 0.014 0.000 0.000 FBO(T) 0.101 0.034 0.049 0.074 0.028 BAD 0.000 0.062 0.000 0.062 0.134 TQIAL 199.999 199,959 199,122 192,921 191,211 A3 98.8 98.1 97.2 99.0 98.0 OR 0.4 0.6 0 0 0 AN 0.8 1.3 2.8 1.0 2.07 194 Stop 3 (Cont'd.) N35) 11.664 11.084 11.445 11.614 11.847 MGO 0.005 0.000 0.000 0.000 0.010 All-203 20.055 20.052 20.536 19.881 20.274 BIO2 68.215 67.932 67.129 67.471 69.085 If) 0.068 0.824 0.069 0.029 0.023 CLO 0.231 0.172 0.673 0.613 0.173 TIO2 0.000 0.016 0.000 0.020 0.020 MNO 0.039 0.007 0.039 0.018 0.023 PBO(T) 0.000 0.085 0.055 0.052 0.000 BAG 0.072 0.010 0.000 0.010 0.041 T 10 . 9 AB 99.0 94.0 97.0 97.2 99.2 OR 0 5.0 0.0 0 0.0 AN 1.0 1.0 3.0 2.8 0.8 Stop 3 (Cont'd.) m - - N120 11.342 moo 0.004 111.203 19.654 8102 66.702 :5) 0.066 020 0.316 noz 0.000 uno 0.038 PBO(T) 0.051 BAG 0.040 zgzgn 98. 88 98.5 on 0 AN 1.5 11.553 0.005 19.986 68.490 0.069 0.380 0.000 0.014 0.000 0.041 195 -3- 11.829 0.000 20.049 68.325 0.060 0.205 0.007 0.018 0.064 0.000 99.0 0.0 1.0 11.811 0.000 20.040 68.813 0.057 0.309 0.000 0.009 0.011 0.083 99.0 0.0 1.0 -3-27 11.265 0.051 20.419 67.615 0.305 0.351 0.000 0.039 0.038 0.052 100. 95.9 2.1 2.0 Stop 3 (Cont'd.) p - - - . - .. - - - - N35) 11.454 11.843 11.839 11.792 11.643 MGO 0.004 0.000 0.000 0.007 0.000 31.203 20.551 19.876 19.954 20.276 19.611 BIOz 68.741 67.884 67.602 68.574 69.146 320 0.038 0.017 0.190 0.078 0.042 CAD 0.642 0.285 0.294 0.380 0.145 T102 0.002 0.030 0.000 0.000 0.000 MNO 0.000 0.000 0.035 0.000 0.016 PEO(T) 0.047 0.006 0.055 0.064 0.013 830 0.051 0.021 0.000 0.000 0.082 W AB 97.0 99.0 98.0 98.0 99.1 OR 0 0.0 1.0 0.0 0.2 AN 3.0 1.0 1.0 2.0 0.7 196 “3%) 300 435% 8102 ‘f’ can noz nuo r30(r) BAD MAMA—M OR New Haven Arkose (stop 2) 12.015 0.000 19.897 68.996 0.071 0.122 0.013 0.000 0.049 0.031 99.1 0.4 0.5 11.771 0.000 19.887 67.612 0.104 0.233 0.007 0.000 0.000 0.000 98.3 0.6 1.1 197 11.728 0.000 19.900 67.784 0.057 0.200 0.000 0.000 0.021 0.021 99.1 0 0.9 11.332 10.876 0.005 0.000 20.118 21.147 65.881 65.346 0.091 0.293 0.786 1.332 0.008 0.007 0.009 0.000 0.024 0.000 0.000 0.031 99103; 95.8 92.1 0.5 1.6 3.7 6.3 Stop 2 (Cont'd.) M N353 H90 355% 81:02 K53 CAD no2 PBO(T) BAO TOTAL OR 198 mwmmm 11.446 0.000 19.202 64.009 0.098 0.336 0.000 0.046 0.000 0.000 95.137 97.9 0.5 1.6 11.248 0.005 20.414 66.376 0.051 0.773 0.000 0.000 0.009 0.103 98.979 96.1 0.3 3.6 11.127 0.000 21.210 65.013 0.124 1.419 0.000 0.007 0.011 0.031 98.943 92.8 0.7 6.5 11.620 0.006 20.095 66.815 0.650 0.172 0.000 0.000 0.009 0.010 99.376 95.7 3.5 0.8 11.674 0.003 19.937 .66.977 0.103 0.267 0.002 0.011 0.004 0.000 98.980 98.2 0.6 1.2 Stop 2 (Cont'd.) M mmmm NA§> ”GO ”“203 8102 :5) C30 2102 230(2) BAD TOTAL OR 11.815 0.000 20.275 68.069 0.127 0.282 0.025 0.012 0.000 0.000 100.605 98.0 0.7 1.3 11.512 0.000 20.505 67.056 0.126 0.693 0.000 0.018 0.024 0.021 99.956 96.1 0.7 3.2 199 10.734 0.014 21.258 64.953 0.083 1.823 0.013 0.037 0.017 0.082 99.015 91.0 0.5 8.5 10.983 0.000 21.397 64.575 0.070 1.810 0.000 0.000 0.028 0.021 98.884 91.3 0.4 8.3 MAJ. 11.909 0.000 20.195 67.870 0.011 0.263 0.000 0.000 0.021 0.000 100.271 98.8 0 1.2 Stop 2 (Cont'd.) 8L§PL§ nag: H30 Anéh 8102 :5: C30 2102 MNO ?BO(T) 330 TOTAL AB OR 200 mag-3.21.2 11.763 0.001 20.319 67.143 0.026 0.355 0.004 0.000 0.030 0.000 99.643 98.4 0 1.6 10.543 0.009 19.652 68.090 2.181 0.051 0.003 0.005 0.000 0.124 100.656 87.8 12.0 0.2 gg-2-19 11.218 0.003 20.651 66.869 0.100 0.923 0.021 0.028 0.034 0.010 99.858 95.1 0.6 4.3 3!-2-§Q 11.850 0.000 20.169 68.352 0.057 0.162 0.016 0.005 0.021 0.031 100.662 98.9 0.3 0.8 NH-2-30 11.972 0.006 20.323 67.903 0.061 0.298 0.029 0.000 0.056 0.031 100.679 98.7 0 1.3 Stop 2 (Cont'd.) mm 335) 300 AL203 8102 3;) can 2102 330(2) 8A0 TOTAL OR 38:33): W m rim-3 12.047 0.007 20.139 67.329 0.012 0.127 0.000 0.039 0.009 0.000 99.709 99.4 0 0.6 11.702 0.000 20.205 67.431 0.014 0.198 0.003 0.019 0.000 0.000 99.572 99.1 0.0 0.9 201 11.658 0.000 20.444 67.314 0.112 0.406 0.000 0.002 0.131 0.000 100.068 97.5 0.6 1.9 11.094 0.000 20.828 66.067 0.066 1.304 0.021 0.002 0.082 0.021 99.486 93.5 0.4 6.1 -2-3 11.778 0.004 20.344 67.801 0.052 0.273 0.009 0.012 0.000 0.062 100.333 98.7 0 0.6 East Berlin Fm. 202 (stop 1) 11.988 0.005 19.925 67.640 0.026 0.032 0.020 0.007 0.049 0.052 99.744 99.7 0.1 0.2 11.221 0.077 21.352 66.818 0.758 0.144 0.000 0.000 0.120 0.000 100.489 95.1 4.2 0.7 -12.102 0.000 19.770 67.450 0.039 0.073 0.000 0.000 0.075 0.021 99.529 99.5 0.2 0.3 11.974 0.009 19.427 67.370 0.048 0.031 0.019 0.037 0.015 0.000 98.930 96.6 0.3 0.1 11.037 0.001 19.329 66.999 0.040 0.040 0.010 0.009 0.028 0.041 97.534 99.6 0.2 0.2 Stop 1 (Cont'd.) 8 LE N153 ”GO 335% 8102 K5) C30 2102 330(2) BAD TOTAL OR 88-1-9 11.234 0.013 20.818 67.295 0.119 0.874 0.000 0.000 0.000 0.072 100.425 95.2 0.7 4.1 g§-!-£ 9.500 0.052 23.309 64.259 0.949 2.303 0.000 0.009 0.098 0.031 100.511 83.5 5.2 11.3 203 B - -5 10.114 0.124 22.631 64.704 1.117 1.091 0.001 0.000 0.125 0.000 99.905 88.3 6.4 5.3 11.872 0.008 19.884 68.045 0.075 0.027 0.000 0.016 0.054 0.000 99.982 99.5 0.4 0.1 58-1-6 12.387 0.021 20.105 67.790 0.016 0.024 0.000 0.009 0.045 0.000 100.397 99.9 0 0.1 Stop 1 (Cont'd.) m 3320 ”GO 355% 8102 3;: C30 2102 ”NO FBO‘T) BRO TOTAL 33 OR 204 3344-- 33_1_6-- LL18-- 333:1 3311-- 11.937 0.000 20.013 67.944 0.009 0.023 0.022 0.000 0.077 0.010 100.036 99.9 0 0.1 11.851 0.000 20.129 66.720 0.071 0.359 0.002 0.002 0.024 0.000 99.158 98.0 0.4 1.6 11.756 0.001 19.803 67.178 0.018 0.088 0.005 0.000 0.000 0.031 98.880 99.5 0.1 0.4 12.105 0.065 20.089 68.638 0.151 0.103 0.004 0.000 0.172 0.041 101.369 98.7 0.8 0.5 11.741 0.010 20.224 66.766 0.089 0.476 0.000 0.000 0.004 0.000 99.309 97.3 0.5 2.2 Stop 1 (Cont'd.) §A§2LE 315) 360 3¢2°3 8102 3;) 0140 2102 NRC 330(2) 330 TOTAL 33 OR 205 53-1-19 EB'J'IZ 53-1-12 53.1.]: 11.895 0.027 19.769 67.696 0.039 0.060 0.013 0.000 0.068 0.103 99.669 99.5 0.2 0.3 11.373 0.049 20.120 68.404 0.279 0.176 0.025 0.000 0.282 0.000 100.708 97.6 1.6 0.8 12.386 0.000 20.814 71.125 0.047 0.232 0.012 0.000 0.051 0.052 104.719 98.7 0.3 1.0 12.247 0.000 20.837 69.955 0.088 0.451 0.009 0.000 0.036 0.000 103.622 98.0 0 2.0 APPENDIX B Microprobe analysis of plagioclase feldspar Appendix QAHBLE 335) ”GO M203 8102 35) CAD 2102 “NO FBO(T) BAO TOTAL AB OR B. Microprobe analysis of plagioclase feldspar. New Haven Arkose (stop 3) 32:33 9.827 0.000 22.634 65.076 0.323 3.072 0.000 0.028 0.009 0.010 100.977 83.7 1.8 14.5 m 33:22:. 38:22 33.22:; 9.895 0.015 22.480 65.255 0.311 3.136 0.026 0.000 0.036 0.021 101.176 83.6 1.7 14.7 206 8.935 0.000 23.059 62.455 0.306 4.420 0.015 0.000 0.026 0.031 99.246 77.2 1.7 21.1 10.027 0.004 21.843 64.696 0.288 2.587 0.000 0.030 0.000 0.021 99.495 86.0 2.0 12.0 10.080 0.000 21.849 64.960 0.580 2.316 0.000 0.000 0.006 0.000 99.792 85.9 3.2 10.9 Stop 3 (Cont'd.) M 335) M60 3‘20: 8102 3;) 030 2102 330(2) 330 TOTAL OR 33:2:1 10.119 0.000 21.859 65.619 0.361 2.150 0.001 0.000 0.022 0.000 100.132 87.6 2.1 10.3 flfl-9-9 9.828 0.001 22.305 65.376 0.328 2.866 0.025 0.000 0.039 0.010 100.779 84.5 1.8 13.7 207 33:3:19 10.847 0.002 21.167 67.140 0.157 1.598 0.018 0.011 0.034 0.000 100.973 91.7 0.9 7.4 ng-g-10 10.678 0.001 21.204 66.905 0.170 1.594 0.006 0.014 0.099 0.062 100.732 91.5 1.0 7.5 Eg-3-16 9.171 0.002 22.437 62.113 0.297 3.406 0.028 0.021 0.039 0.000 97.514 81.5 1.7 16.8 Stop 3 (Cont'd.) M 335) ”GO 335% 8102 Kg: CAO 2102 330(2) BAO TOTAL OR 33-3-2; 10.289 0.000 21.536 64.496 0.158 2.097 0.014 0.041 0.034 0.000 98.665 89.1 0.9 10.0 ng-g-gs 9.913 0.006 22.112 64.285 0.150 2.897 0.003 0.000 0.032 0.040 99.437 85.4 0.8 13.8 ug-g-gs 9.751 0.000 22.069 63.781 0.116 2.958 0.024 0.043 0.088 0.030 98.861 85.1 0.7 14.2 n3-3-27 8.885 0.009 23.123 62.221 0.238 4.127 0.019 0.007 0.036 0.000 98.665 78.5 1.4 20.1 EE-9-30 8.535 0.000 24.253 61.617 0.149 5.194 0.026 0.002 0.058 0.113 99.948 74.2 0.8 25.0 2102 330 330(2) 330 TOTAL OR New Haven Arkose (stop 2) mm 10.066 0.000 22.326 64.807 0.169 3.093 0.009 0.000 0.013 0.000 100.482 85.1 0.9 14.0 33:2:1 9.206 0.007 22.776 63.147 0.533 4.010 0.018 0.021 0.113 0.021 99.851 78.2 3.0 18.8 209 n:z:1 10.351 0.000 22.067 64.813 0.188 2.576 0.000 0.000 0.019 0.052 100.066 87.0 1.0 12.0 33:2:19 9.454 0.000 22.478 62.794 0.198 3.433 0.020 0.000 0.000 0.062 98.438 82.3 1.1 16.6 33:2:12 10.617 0.013 21.122 64.598 0.399 1.658 0.004 0.000 0.028 0.021 98.459 90.0 2.2 7.8 Stop 2 (Cont'd.) BAHELB nag) KOO 8102 31203 3;) GAO 2102 330(2) 330 TOTAL OR EE-Z'JS 10.079 0.000 22.660 62.397 0.138 3.075 0.000 0.000 0.024 0.000 98.372 84.9 0.8 14.3 210 ug-2-19 9.871 0.000 22.503 64.136 0.368 3.185 0.034 0.021 0.015 0.000 100.133 83.2 2.0 14.8 33:21: 10.321 0.003 21.453 64.553 0.327 2.354 0.024 0.000 0.030 0.000 99.064 87.2 1.8 11.0 QLHELB 335) ”GO 3¢2°3 8102 3;) GAO 210z MNO FEO(T) BAO TOTAL AB OR East Berlin Fm. 33-]-g 10.550 0.000 21.659 63.595 0.158 2.218 0.018 0.000 0.000 0.062 98.259 81.1 9.4 9.5 39-1-7 9.387 0.005 23.845 61.631 0.032 4.535 0.000 0.018 0.086 0.000 99.540 78.8 0.2 21.0 211 (stop 1) 23.1.}; 9.888 0.010 23.402 65.155 0.184 3.265 0.008 0.000 0.043 0.000 101.955 83.7 1.0 15.3 APPENDIX C Microprobe analysis of K-feldspar Appendix QLHRLE 335) KOO 335% 8102 35) CAD 2102 NRC FBO(T) BAO TOTAL AB OR New Haven Arkose (stop 4) 19.124 63.285 14.599 0.019 0.000 0.035 0.000 0.270 98.300 9.1 90.9 0 18.730 64.036 15.570 0.000 0.000 0.009 0.017 0.363 99.015 2.8 97.2 0 212 18.719 63.904 14.434 0.000 0.001 0.005 0.002 0.218 97.908 6.2 93.8 0 C. Microprobe analysis of K-feldspar. 18.999 64.603 14.035 0.000 0.000 0.000 0.017 0.000 98.453 7.8 92.2 0 18.969 64.940 13.994 0.002 0.000 0.000 0.015 0.000 99.028 10.9 89.1 0 Stop 4 (Cont'd.) M “32’ “GO Aldo; 8102 35: CAD 21:0z 330(2) BAO TOTAL OR NH-4-6 0.927 0.000 18.793 63.965 14.288 0.003 0.041 0.000 0.094 0.125 98.236 9.0 91.0 0 213 Mlz" "GO 2140, 8102 :5) GAO 2102 “NO PEO‘T) BAO TOTAL OR New Haven Arkose (stop 3) 0.000 18.857 65.163 15.537 0.012 0.001 0.000 0.006 0.186 100.988 10.7 89.3 0 214 18.520 64.539 15.823 0.011 0.011 0.000 0.034 0.176 100.015 7.9 92.1 0 64.612 15.177 0.019 0.000 0.000 0.021 0.124 100.047 10.8 89.2 0.0 0.011 18.464 63.357 16.360 0.000 0.000 0.007 0.032 0.331 98.963 3.5 96.5 0 0.000 18.802 65.528 15.983 0.000 0.011 0.000 0.000 0.299 100.301 6.1 93.9 0 Stop 3 (Cont'd.) am 335) ”GO lufips 8102 3;: CAO 2102 ”NO PEO(T) BAO TOTAL AB OR 33-2-16 4.106 0.000 11.564 42.762 0.035 19.779 18.564 0.002 0.430 0.000 97.243 27.4 0 72.6 33:33.9 “-3- 0.916 0.002 18.703 64.061 15.511 0.028 0.027 0.028 0.047 0.104 99.425 92.0 8.0 0 215 1.082 0.004 18.927 63.961 15.333 0.006 0.000 0.000 0.030 0.042 99.384 9.9 90.1 0.0 flfi-Q-IG 1.272 0.009 18.791 64.916 14.769 0.064 0.013 0.009 0.002 0.010 99.856 11.2 88.8 0.0 !§-3-g§ 0.936 0.003 18.556 65.213 15.749 0.000 0.000 0.000 0.000 0.000 100.456 8.3 91.7 0 Stop 3 (Cont'd.) mm “2° KOO 3¢2°3 8102 :53 CAD 210z HNO FBO(T) BAO TOTAL OR 216 wmmmm 1.213 0.029 18.782 64.570 14.666 0.043 0.000 0.000 0.070 0.591 99.964 11.3 88.7 1.423 0.000 19.221 65.142 14.391 0.010 0.002 0.032 0.002 0.208 100.431 13.4 86.6 0.0 0.983 0.012 18.202 63.525 15.366 0.003 0.018 0.000 0.015 0.233 98.346 8.9 91.1 0 0.938 0.000 18.716 64.385 15.923 0.044 0.010 0.000 0.028 0.041 100.085 8.2 91.8 0 2.505 0.002 19.042 63.563 12.857 0.077 0.000 0.135 0.062 0.896 99.140 22.8 76.9 0.3 Stop 3 (Cont'd.) W 3153 300 3355 810z Kg: 030 2102 330 330(2) BAO 20233 33 OR 217 mmmmw—a 1.027 0.024 18.793 64.826 15.764 0.006 0.000 0.030 0.103 0.000 100.572 9.0 91.0 0 1.056 0.006 18.939 64.179 14.668 0.050 0.015 0.000 0.040 0.176 99.129 10.3 89.7 0 1.164 0.011 19.079 64.757 14.273 0.035 0.011 0.000 0.013 0.313 99.656 10.6 89.4 0.0 1.227 0.000 19.155 64.236 13.721 0.023 0.000 0.000 0.047 0.302 98.710 12.0 88.0 0.0 1.377 0.020 18.872 64.614 13.582 0.043 0.000 0.000 0.023 0.166 98.698 13.0 87.0 0.0 218 New Haven Arkose (stop 2) m m 33:2:12 m 33:22; 33:2:11 NAZO 1.059 0.250 1.253 0.299 1.206 MOO 0. 009 0. 000 0. 014 0. 007 0. 000 ALZO3 18.940 18.610 19.033 18.914 18.990 8102 63.821 63.373 63.964 64.088 62.798 K20 14.802 16.012 14.588 16.127 14.377 CAO 0.049 0.000 0.102 0.080 0.065 TIOZ 0.000 0.032 0.017 0.000 0.002 DINO 0.018 0.000 0.000 0.011 0.000 PBO(T) 0.051 0.000 0.000 0.023 0.034 BAO 0.279 0.000 0.227 0.000 0.621 TOTAL 99.030 98.277 99.197 99.550 98.093 A3 9.8 2.3 11.5 2.7 11.3 OR 90.2 97.7 88.0 96.9 88.7 A)! 0 0 0.5 0.4 0 Stop 2 (Cont'd.) BAH L 315) “GO 3‘203 8102 ‘5’ GAO 2102 330(2) 330 TOTAL OR 33-2-19 0.699 0.000 18.851 64.962 15.305 0.000 0.000 0.000 0.019 0.000 99.837 6.5 93.5 0 ng-g-gs 1.056 0.000 18.749 63.585 14.584 0.040 0.022 0.000 0.011 0.290 98.338 9.9 90.1 0 33:22: 0.430 0.011 18.618 63.734 15.326 0.000 0.000 0.000 0.056 0.218 98.392 4.1 95.9 0 “33’ use 355% 8102 ‘5’ can 2102 330 330(2) BAO TOTAL OR East Berlin Fm. 32.1.. 0.492 0.007 19.231 64.066 14.975 0.007 0.032 0.000 0.008 0.923 99.742 4.4 95.6 0.0 220 33-1-5 0.307 0.009 18.610 63.482 14.878 0.009 0.047 0.000 0.376 0.540 98.259 3.3 96.7 0.0 (stop 1) 33.1.1- - 33.1.4- - 33:1:1 0.338 0.007 19.217 65.678 14.776 0.009 0.000 0.000 0.036 0.550 100.611 3.4 96.6 0 0.688 0.000 18.711 64.174 15.836 0.010 0.009 0.041 0.004 0.340 99.814 6.2 93.8 0 0.376 0.024 18.688 64.510 15.350 0.001 0.000 0.000 0.000 0.010 98.961 3.6 96.4 0.0 Stop 1 (Cont'd.) EAHELE 335) ”GO 3¢2°3 8102 3;) CAD 2102 "NO FBO(T) BAO TOTAL AB OR 33-1-19 0.651 0.019 18.936 63.001 14.766 0.002 0.000 0.041 0.002 0.682 98.100 6.3 93.7 0 1.030 0.000 18.909 63.478 13.709 0.117 0.007 0.002 0.000 0.125 97.377 9.9 90.1 0 221 53.1.]; 32.1.]; 0.760 0.002 18.754 62.548 15.549 0.000 0.008 0.000 0.017 0.774 98.411 6.9 93.1 0.0 APPENDIX D Microprobe analysis of chlorite Appendix QAHELE NAé) H60 8102 35) can 2102 FEO(T) BAO TOTAL New Haven Arkose (stop 4) D. Microprobe analysis of chlorite. 0.051 18.829 18.945 29.547 0.193 0.717 0.011 0.443 14.664 0.000 83.399 0.116 15.414 25.263 30.673 0.532 0.188 0.050 1.309 14.028 0.000 87.573 222 0.065 16.212 23.405 28.578 0.230 0.074 0.036 1.044 18.574 0.019 88.328 0.070 16.299 24.959 33.109 0.602 0.195 0.037 0.528 12.488 0.000 88.287 0.069 17.104 26.164 34.063 0.647 0.163 0.000 0.518 11.981 0.000 90.709 East Berlin Fm. (stop 1) W 33412-— 3111-- 335) 300 32203 8102 xx) 030 2102 PEO(T) EAO TOTAL 0.064 20.964 20.369 30.252 0.068 0.109 0.000 0.681 15.031 0.050 87.588 0.060 16.533 22.130 33.932 0.927 0.313 0.046 0.608 13.294 0.010 87.854 223 APPENDIX E Microprobe analysis of zeolite Appendix E. Microprobe analysis of zeolite. New Haven Arkose (stop 3) EAHBLE E!:1:12 33:1:12 Efizizlfl 82:1:12 35:1:11 NAZO 0.033 0.086 0.037 0.295 0.081 MOO 0.010 0.000 0.000 0.013 0.000 AL203 21.345 22.213 22.131 22.090 23.038 BIO2 50.853 51.734 51.901 52.934 54.335 K20 0.788 0.547 0.536 1.326 0.822 OAO 10.730 11.399 11.355 10.533 11.280 TIO2 0.017 0.011 0.000 0.001 0.009 NNO 0.000 0.000 0.000 0.032 0.000 PEO(T) 0.056 0.058 0.056 0.045 0.006 BAO 0.000 0.021 0.000 0.010 0.031 TOTAL 83.833 86.070 86.010 87.280 89.601 224 Stop 3 (Cont'd.) fiAHPLE 335) “GO 5&203 8102 35) CAD 2102 PEO(T) BAO TOTAL flfl-3-11 0.296 0.017 22.866 54.805 1.681 10.607 0.008 0.000 0.023 0.031 90.334 0.090 0.000 22.231 51.386 0.655 11.310 0.017 0.000 0.000 0.031 85.721 M Efi___11-3- . 0.161 0.000 21.805 50.666 0.955 10.933 0.010 0.016 0.028 0.031 84.605 APPENDIX P SEM and BSEM analyses Appendix F. SEM and BSEM analyses stop sample 831! 38314 NE-4-6 x x NH-4-5 - - NE-4-4 x x 4 NB-4-3 x x NE-4-2 x x NH-4-1 x x NE-3-36 - x NE-3-35 - x NH-3-34 - - NE-3-33 x - NE-3-32 - - NE-3-31 - - NE-3-30 x x NE-3-29 - - 3 NE-3-28 x x NB-3-27 x x NE-3-26 - - NE-3-25 x x NB-3-24 - x NH-3-23 x x 33-3-22 - - 226 Appendix F (Cont'd.) 227 stop Sample 8E! BSEM 33-3-21 - - 33-3-20 - — NE-3-19 x x NE-3-18 - x NE-3-17 - - NE-3-16 x x NR-S-IS - - NE-3-14 x - NE-3-13 - - NH-3-12 - - NR-3-11 x x 3 NE-3-10 x x NH-3-9 x x NR-3-8 - - NE-3-7 x x NE-3-6 - - NE-3-S - - NE-3-4 - - NE-3-3 x x 33-3-2 x - 33-3-1 x x 228 Appendix F (Cont'd.) stop Sample BEN BSEM NR-2-35 x x NE-2-34 x x NE-2-33 x - 33-2-32 - - NE-2-31 - - NE-2-30 x x NH-2-29 - x NH-2-28 - - NE-2-27 - - NE-Z-ZG x - 33-2-25 - x 2 NR-2-24 x - NE-2-23 - - NE-2-22 x x 33-2-21 - - Nfl-Z-ZO - - 33-2-19 x x 33-2-18 - - 33-2-17 x x 33-2-16 - - 33-2-15 - - 33-2-14 x x 33-2-13 x x 229 Appendix F (Cont'd.) 8203 Buplo BE)! 8831: 33-2-12 x x 33-2-11 - - 33-2-10 x x Nfl-Z-Q x x NE-z-O - - NH-2-7 x x 2 NE-Z-G - - NE-Z-S - - NB-2-4 x x NB-2-3 - - un-z-z x x 33-2-1 - - BB-l-ZB - x BB-1-27 - - EB-l-ZG - - 33-1-25 x x BB-1-24 - - 1 EB-1-23 - x 33-1-22 - - 83-1-21 x x 33-1-20 - - EE-1-19 - - 230 Appendix F (Cont'd.) 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