A WWIMY AMI-Tm Ur m: vam DEVONIAN 801$ BLANC FORMATION IN MICHIGAN TM“: {or fine; Degree 0: Mr. 3. BE F‘s-E.” ”Sm?! : 7Mflflt. 2] MC; Ai Swim: Llii‘i: 2.21:5,“ : and B Qéua-w “£172.33: “333135. 1957 THhSlt-j "3 LIBRARY Michigan State University 4—— SUPPLEMENTARY MATERML 1N BACK OF BOOK .A SEDIMENTARY ANALYSIS OF THE LOWER DEVONIAN BOIS BLANC FORMATION IN MICHIGAN by DONALD LARRY GOODRICH A THESIS Submitted to the College of Science and.Arts of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geology 1957 (fa) 7/57 (3" (9419' -) A SEDIMENTARY.ANALYSIS OF THE LOWER DEVONIAN BOIS BLANC FORMATION IN MICHIGAN DONALD LARRY GOODRICH ABSTRACT .A quantitative analysis was performed on the sections from 2h wells representing the Lower Devonian, Bois Blanc formation, in the Michigan Basin. This quantitative study involved sampling, removal of water solubles, removal of acid solubles, disaggregation, sieving, mounting and analyzing the quartz grains. The results of these analyses were expressed as numerical values of the lithologic ratios, which were used in the constructioncfi‘the clastic, evaporite and chert-carbonate ratio maps. The interpretation oftflmztectonic conditions was made by superimposing'Uuaisopach map over the various lithofacies maps and making a study of the patterns formed. These patterns indicate that the major portion of the sediments were derived from the Wisconsin Arch region and were deposited1nukn*stable shelf conditions. ii ACKNOWLEDGMENTS The author wishes to express his sincere appreciation to Dr. B. T. Sandefur for his encouragement, interest and cooperation toward the completion of this manuscript. The writer also wishes to thank all of the other mem- bers of the Geology Department at Michigan State University for their assistance and advice on pertinent data relevant to this thesis. The cooperation of the Michigan Geological Survey and its aid in selecting some of the wells needed for this thesis was deeply appreciated. iii é CONTENTS {”3 INTRODUCTION History of the Michigan Basin . . . Sedimentary Facies . . . . . . . Lithotopes and Lithofacies Purpose . . . . . . . . STRATIGRAPHY OF THE 8018 BLANC FORMATION Discussion . LOCATION.AND SELECTION OF WELLS Requirements for Selection of Wells Selection of Wells LABORATORY PROCEDURES Sampling Method . . . . . . . . Removal of Water Solubles . . . . . . Removal of Acid Solubles . . . . . . . Disaggregation . . . . Sieving . Mounting and Analyzing the Quartz Grains . Errors in Sampling and Treatment . . . . . Results in Sampling and Treatment . . . . LITHOLOGIC iNTERPRETATIONS . . . . . . . Lithologic Ratios . . . . . . . Construction of Lithofacies Maps INTERPRETATION OF FACIES MAPS Methods of Geologic Interpretation . Geological Interpretation . . . GEOLOGIC HISTORY . CONCLUSIONS SUGGESTIONS FOR FURTHER STUDIES REFERENCES iv H \JMH¥KF‘ £7 ~0xo «D (r O\ \n¥7oaH HHHp—o [\_) NHHH R.) OCDCDN mm Cam I\.) 0\ NR) 030 33 36 37 38 Table II. III. IV. TABLES Generalized Column of Lower Devonian Formations in Michigan Correlated with the New York, Lower Devonian Formations . . . . . . . . . . . . Description of Wells Used in Bois Blanc Facies Analysis . . . . . . . . . . . . . . . . . Quantitative Analysis . . . . Lithologic Ratios . . . . . . . . . . . . . . Page 11 21 25 Plate 1. II. PLATES Representative Quartz Grains Found in the Bois Blanc Formation Relations Between lsopachs and Facies Lines Page 19 27 Map II. III. IV. MAPS Location of Wells Isopach I Clastic Ratio Evaporite Ratio Chert-Carbonate Ratio vii Page 10 Pocket Pocket Pocket Pocket INTRODUCTION History of the Michigan Basin Since the beginning of extensive oil and gas development hiMichigan, subsurface investigation of the Michigan Basin has lmen of increasing importance. In the pastiMDyears over 20,000 Ni and gas wells have been drilled in Michigan. These have meatly contributed to our knowledge of stratigraphy and struc- uue of the Basin. Newcombe (1933) describes the areal extent of the Mich- igan Basin Province as follows: The area comprising the Michigan Basin Province includes about 106,700 square miles and stretches from Fort Wayne, Indiana, on the south, to Whitefish Point, near Sault Ste. Marie, Michigan, on the north and from west to east about 370 miles. The Basin is postulated to have been formed during Pre- Cmunian times. The sedimentary rocks which conform to this flmucture were deposited during Paleozoic and late Cenozoic thws. During the Paleozoic, shallow bodies of water occupied Um Michigan Basin at successive intervals. The various phys- ical and chemical depositional agencies formed concentric smucers of sediments, each on top and smaller than the pre- cmding, with each saucer representing a period of time. The total thickness of Paleozoic rocks within the central part of the basin approximates 15,000 feet. The Cenozoic deposits are l only represented by the various glacial features and strata deposited during the Pleistocene glacial epoch. These depos- its occur as a mantle over most of the Paleozoic rocks, and attain a thickness up to 1200 feet in the northwestern section of the basin. The tectonic elements surrounding the basinenwzclosely related to the structural and depositional historycfl‘theNfich- igan Basin. Pirtle (1932) defines these elements as, l. The Wisconsin Arch in the west. 2. The two limbs of the Cincinnati Arch, the Findlay Arch in the southeast and the Kankakee in the southwest. 3. The Canadian Shield on the north. .A recent article by Green (1957), expresses some doubt as to the correlation of the Kankakee.Arch as part of the Cin- cinnati Arch complex. He stated, "no arching extends from Indiana into Illinois, where the Kankakee.Arch is supposedly located." Green (1957) suggested that the name Kankakee.Arch be dropped from the literature, and the name Francesville be given for the arch in Indiana. The principal lines of folding of the Paleozoic rocks within the Michigan Basin trend in a northwest-southeast di- rection. Pirtle (1932) believes these folds were controlled by lines of structural weakness, which existed in the base- ment rocks at the time of deposition. Newcombe (1933) believes the accumulation of oil and gas in local anticlines and folds within the basin were con- trolled by erosional unconformities, which show a direct re- lation to the various porous zones. The development of oil and gas within the basin has been of great economic importance. With the increasequnowledgeuof the sedimentary and structural characteristicsrevealedlwrthe drill holes, investigation of individual stratigraphic units will be a contribution to the future studies of the Michigan Basin. Sedimentary Facies In the past 20 years, the facies concept of sedimenta- tion has become increasingly important. The recognition and evaluation of facies changes are of prime importance for proper interpretation of the stratigraphic and structural fabric of an area. Moore (l9h9) defines sedimentary facies as, "areally segregated parts of differing nature belonging to any genet— ically related body of sedimentary deposits." Moore also emphasized that facies are "variants or aspects of strati- graphic units having mutually exclusive space distribution." Krumbein (1952) states, "these variants or aspects may be expressed in terms of lithology, faunal content, tectonic implication, inferred environment of deposition, or in other u ways." This would in turn give rise to lithofacies maps, biofacies maps, tectofacies maps and environmental pattern maps. .A sedimentary facies may involve a member, a formation or a group. Facies changes are the direct result of irregularities, such as variations in climate, changes in sea level, tectonic adjustments or erosional cycles. Lithotopes and Lithofacies Krumbein and Sloss (1951) refer to lithotopes as, "an area of uniform sedimentation." Single or successive litho- topes can be observed in an area of sedimentation, i.e., marine to lagoonal. Moore (19h9) has also defined lithofacies as, "groups of strata demonstrably different in lithologic aspect from laterally equivalent rocks." The lithologic aspect is con- trolled by the lithotopes of which the lithofacies are com- posed. Therefore, a number of lithotopes form a lithofacies, which are derived from the gross aspect of the lithology. The various groups of lithofacies can be expressed in the form of a lithofacies map. The various lithofacies maps provide a pattern and the means for interpreting the signifi- cant tectonics and environment that existed during the deposi- tion of a rock unit. Purpose The purpose of this investigation is to determine the structural and environmental conditions which existed during the deposition of the Bois Blanc (Lower Devonian) formation in the Michigan Basin. This will be done largely by the prep- aration and interpretation of lithofacies maps. Dice (1955)made acomposite study of the Devonian rocks in the Michigan Basin. Itis felt thatzamore accurate picture cfi‘thetectonic environment could be produced by analysing and interpretating lithofacies of the individual members of the Devonian period. The author hopes that the maps and data obtained from this analysis will provide a better understanding of the various features during the deposition of the Bois Blanc formation. STRATIGRAPHY OF THE BOIS BLANC FORMATION Discussion Until l9h5 the Bois Blanc formation was not recognized as a separate formation in the Lower Devonian series. The lithologic subdivisions of this formation were considered by some as the upper portion of the Bass Island formation (Upper Silurian); others thought it to be in the Sylvania formation (Lower Devonian). Landes, Ehlers and Stanley (l9h5), named and described the type section for the Bois Blanc formation. They described the type locality as, "the rocks of the formation are well— exposed on Bois Blanc Island, situated in Lake Huron, slightly less than 2% miles southeast of Mackinac Island." Most of the formation in the subsurface consists of light-colored carbonate and chert. The chert is most abundant in the lower partcfl‘the section and is usually interbedded with dolomite. The middle and upper parts consist mostly of limestone with some inter- bedded doiomite and are consideredcyiiUBfossiliferous by these authors. Rocks of the Bois Blanc formation crop out in the ex- treme northern part of the southern peninsula of Michigan. The strata is then only present in the subsurface, except in the southwestern area and along the southern margin of the 6 state where they have been removed by pre-Sylvanian erosion. The thickness of the formation is approximately 300 feet at the outcrop on Bois Blanc Island and it attains its maximum thickness of 1,000 feet in southwestern Ogemaw county. The strata then progressively thin out to the south and south- west. The Bois Blanc rocks lie unconformably on the Bass Is- land formation, except where the Garden Island formation exists in a patchy distribution in portions of the northern extremi- ties of the southern peninsula. Where the Sylvania formation is absent, the Bois Blanc formation is overlain by the lower formation of the Detroit River Group. Table I shows the stratigraphic position of the Bois Blanc in relation to Middle and Upper Silurian and Middle and Lower Devonian groups and formations. The Michigan formations were correlated with the New York formations of the same age. TABLE I GENERALIZED COLUMN OF LOWER DEVONIAN FORMATIONS IN MICHIGAN CORRELATED WITH THE NEW YORK, LOWER DEVONIAN FORMATIONS Michigan Lower Devonian (Generalized) Tl Lithology and Thickness of Michigan Section korre l ated New Yom Lower Devonian (Generalized) |¥ 15 c Dundee Limestone Marcellus H Formation O—EOO Feet Formation ° Dolomite Salt 8 Luca? Anhydrite ’ 0 Formation 0-11211 Feet g L. Dolomite limestone 0 .g Amherstberg and Sandstone (S tr Formation 0-200 Feet m ’ Sandstone ’m '3 Sylvania Dolomite, Chert '3 :3 Formation 0_540 Feet g c Bois Blanc Dolgmigtogfiert O Scholarie ,§ Formation 0-1000,Feet Formation c . _ 0 ,8 Dolomite,~ > A Garden Island 0 Sandstone Oriskany 3 g Formation 3 0-30 Feet Formation o . S S 3 Port Ewen g Formation '55 3 Olsen 2: Formation Bercraft Formation New Scotland and Coeymans Formation 1* Bass Island Dolomite Keyser Group 50-570 Feet Group Q Salina Salt, Anhydrite, Salina : = Group 'L- 13358558615522? Group 5.. p I: Lockport Dolomite Lockport “3 .3 Group 55-130 Feet Group » .3 w E Clinton Doégmite, Clinton ert CT . J U u Group 150,275 Feet roup J‘- --—m T "' ”Ln-1.; LOCATION AND SELECTION OF WELLS Requirements for Selection of Wells In this study, special consideration should be given to the selection of the wells for the analysis. Wells should be selected to give the best vertical and lateral coverage of a particular formation. Consideration should alsolngiventx>the type of drill- ing to obtain the subsurface samples. The common types of drilling,rotarvcn*cable-tool,haveaidirect bearing on sample collection. TTmzrotary typecfl‘drilling causesaacertain amount of contamination by cavings, while the cable-tool drilling is almost free of foreign materials. Selection of Wells The availability of wells that penetrated into the Silurian rocks, thusly giving a complete section of the Bois Blanc formation, were fairly poor. Twenty-four wells were selected for this study, with the majority of these wells drilled by the rotary method. The location of the wells are shown on Map 1. Table 11 describes the wells by county, town- ship, driller, farm and thickness of formations. .A binocular microscope was necessary to pick the top and bottom of the Bois Blanc formation, for most of the wells. 9 lO MICHIGAN DEPARTMENT or CONSERVATION GEOLOGICAL SURVEY DIVISION CfilfiLEI/O/J *N'NORIWV if AP Location URGd in T & o f Well 8 Bois Blane Facies Investigations 016M! ALC WA '4 anti/M or!“ “CLAN“ I5 0 [All]: ~ " (_ KALKAIKA cpAwFu-vfl O O M 1711 'uFOIg mun-nu [caravan u m m e. O “4"" UK! oscuu _ can GUOMN oc(‘~‘ '9 ”(£0371 [I 6“4 AHIL ANO O A WAYOd ”a" menu: 6947"” JAG/NA TUICO‘ 4 51 0). ll (ON '0' HI 2 2 2 «una- “It“ ”can 87 ION/A Cd IN row .3N/AI/A1355 O l o ”‘6‘” ”.1 ‘1 "dfi ,NGNAM (JV/NGJTM OfiA’AA-Alo “W T r“ 24 O l o I W)” 54“: A r Gal {5 NOW App‘wv IMMINA w rv ’ T— I i I I O I Lyn um“ . ‘- ' "'4P my‘tI’J MM” 0‘ 11 TABLE II WELLS USED IN ANAXLSIS Thick- County Company and ness of Well and Farm and Section No. Township Permit No. Sec. Twp. Rg. in Feet 1 Monroe Francis T. Canon 12 68 9E 38 Frenchtown E. Compau No. 1 No. 13867 2 Wayne Sun Oil Co. 7 SS 10E ES Taylor Sun InksterIct.No.l . No. 1757h 3 St. Clair Panhandle Eastern 31 SN 16E 13h Clay Sass No. l ' No. 19632 A Oakland Panhandle Eastern 11 LN 11E 70 Oakland Schroeder No. 1 No. 19633 51 Sanilac Shell Oil Co. 15 ION 15E 390 Buel Burch No. 1 No. llhOS 6 Huron Pure Oil Co. 22 17N 15E 522 Rubicon J. Stapleton No.1 No. ll83h 7 Bay Gulf Refining Co. 3h 15N RE 335 Kawkawlin Salina No. 1 No. 10551 8 Ogemaw Ohio Oil Co. 35 22N 2E 955 West Branch Reinhardt Con.No.l No. 12898 9 Oscoda Ohio Oil Co. 30 25N 3E 600 Mentor Mio Unit.Area No.1 No. 11995 10 .Alpena C. W. Teater 18 32N 6E 300 Long Rapids Nevins No. 1 No. 2960 11 Otsego Brazos Oil & Gas 15 29N 2W h58 Chester State-Chester HENo.l No. 16902 12 TABLE II--Continued County Company and Egigkgf Well and Farm and Section N0. Township Permit No. Sec. Twp. Rg. in Feet 12 Cheboygan Roosevelt Oil Co. 1 3hN 2W 310 Ellis Ormsbee No. 1 No. 1h936 13 .Antrim Ohio Oil Co. 1h 31N 8W 360 CentralLake PL Chamberlain No.1 No. 10004 Mi Leelanau Copeland-Barton 5 29N 12W 385 Centerville L. Overby No. 1 NO. 10103 15 Gr.’Traverse (Carter Oil Co. 9 25N 10W 390 Paradise Lemcool No. 1 No. 18512 If) Manistee Carter Oil Co. 35 2hN 15W 2h0 Pleasanton Fred Crook No. 1 No. 17709 17 Osceola Ohio Oil Co. 29 18N 10W 120 Lincoln P.N. Stedman No. 3 No. 12802 18 Mason Superior Oil Co. 25 17N 16W 80 Eden M. Sippy etal No. 17 No. 18905 19 Newaygo Sun Oil Co. 29 12N 11W 73 Croton Hotchew No. 1 No. 15373 20 Kent Skelly Oil Co. 3 SN 9W 50 Bowne .Alto L.P.G. Storage No. 1, No. 17535 21 Clinton Parsons Brothers 27 8N MW 95 Lebanon Angie Sillman No. 1 No. 19272 22 Shiawassee Panhandle Eastern '23 5N 2E 220 Perry S. Nemcik No. 1 No. 16738 23 Livingston Panhandle Eastern 25 2N SE 187 Genoa M a G Bauer No. 1 No. 11818 at Washtenaw Johnson & Pew 1h 28 3E 80 Sylvan Mohrlock Comm No. 1 No. 19751 13 The top of the formation contains light carbonates and some brown to gray nodular chert. The chert differs from the sandy, and white tripolitic variety found at the base of the Sylvania formation. Dark carbonates occur at the base of the Detroit River Group, which overlies the Bois Blanc formation where the Sylvania formation is missing. The bottom of the Bois Blanc formation is characterized by chert, which is lacking in the underlying Garden Island or Bass Island formations. LABORATORY PROCEDURES Sampling Method The samples used were obtained from the Michigan Geo- logical Survey or the Gulf Sample Well Library at Michigan State University. The section representing the Bois Blanc formation was picked from each set of selected sample wells. The vertical section ranged from about 50 feet to approximately 1,000 feet. The maximum allowable by the Michigan Geological Survey was removed from each sample vial to represent the section. The weight of sample per foot depended on the vertical distance represented by each vial. The sample was then stirred with a magnet to remove the small pieces of drill bit and other iron. Obvious contamination, such as fragments of shale, which are foreign to the section, were removed. The composite sample Was then weighed and made ready for the following treatments. Removal of Water Solubles Weigner (1927) found that by boiling the sample in water, the water soluble salts will go into solution and then may be removed by filtering or pipetting. Each sample was treated with about 200 milliliters of tap water and boiled for two hours. Ten milliliters of clear ILL 15 solution were siphoned off, and half a gram of silver nitrate was added to check the salinity of the solution. This process \Mas repeated until the precipitate formed was not more dense than that formed by treatment of normal tap water, indicating that about all chlorides had been removed. The sample was then dried and weighed. Removal of.Acid Solubles A.25 percent solution of hydrochloric acid was then added to the remaining sample, to remove the carbonates. After the effervescence has ceased; the sediment was allowed to settle. 'The supernatent liquid was drawn off and filtered. .A 50 per- Cent hydrochloric acid solution was added to the sediment, jpipetted and filtered, and then a 100 percent hydrochloric solution was added and gently heated to remote the less sol- ‘uble carbonates, which resisted the earlier treatments. The sediment was then washed several times, and tested with blue litmus paper, until no acid remained. The sediment was dried and weighed and its weight added to the dry weight of the ma- terial retained by the filter paper. The difference in weight \Mas reCOrded as acid solubles. Disaggregation The major portion of the argillaceous material and C{nartz grains are scattered in the carbonates of the Bois Blanc formation and were therefore, broken free from the 16 sample by the preceding treatments,lnn;there arenfirmnsamounts of argillaceous material and quartz grains, included in the chert. In order to determine these minor amounts some type of disaggregation was necessary. Krumbein and Pettijohn (1938) define disaggregation as, "the breaking down of aggregates into smaller clusters or into smaller grains." Two techniques of disaggregation were investigated and \Ialidated. First, the Super-Sonic disaggregation was investi- gated. Thistype of experiment has been suggested by various individuals, but no literature was found on the subject. For the experiment the author‘usedIflmaSonic<33cillator in the Microbiology department at Michigan State University. IX small sample of the Antrim shale was placed in the oscilla— tor, using water as the immersing medium. The machine was allowed to operate for seven minutes. Upon removal of the sample, it was found that approximately one-fourthcfl‘the ma- terial had been broken free from the massive fragments. The sample was poured into a vial and placed on a centrifuge for ten minutes, to speed up settling velocities. .After removing the sample from the centrifuge the solution was allowed an additional settling period of 2h hours. .At the end of this time, some of the material still remained in suspension. It is felt by the author that more experimental work Should be extended to the applicationcfl‘theideacfl?super-sonic 1? disaggregation, before it can be successfully used in this type of research. Potassium hydroxide was used for the second technique. Tddis proved to be the best disaggregation agent. .A crystal (3f quartz, and a fragment of chert, both of known weight were zillowed to boil in a supersaturated solution of potassium hy- lace. These relationships, in respect to other lithologic garoups, can be shown clearly on lithofacies maps. Lithofacies maps do not depict a complete geologic Iiistory, but they do offer the interpreter a simplified form (Sf complex stratigraphic data, so that broad concepts can be expressed . The ratios obtained from Table IV were plotted in their respective positions on a base map. Lines of equal ratios, expressed as an arithmetic number, were contoured from this data. An isopach map of the Bois Blanc formation was con- structed on semi-transparent paper. By placing the isopach Inap over the specific ratio map, interpretation of Krumbein's relationships of isopach and facies lines was facilitated. The maps constructed from the data compiled in Table IV are the Clastic ratio, evaporite ratio and chert-carbonate 2L1 ratio maps. The isopach map was constructed from the thick- nesses given in Table 11. These maps are located in the pocket on the back cover of this thesis. 25 TABLE IV LITHOLOGIC RATIOS Well Clastic Evaporite Chert-Carbonate Number Ratio Ratio Ratio 1 0.081 0.010u 0.683 2 0.080 0.0023 0.h1h 3 0.072 0.0086 0.299 A 0.099 0.0007 0.287 5 0.139 0.0015 0.1h6 6 0.058 0.0589* 0.579 7 0.079 0.0016 0.h16 8 0.106 0.0028 0.L9u 9 0.151 0.0039 0.h69 10 0.089 0.0060 0.712 11 0.1u3 0.00u2 0.h35 12 0.068 0.001h 1.002 13 0.118 0.0018 0.298 In 0.180 0.0128 0.275 15 0.165 0.0091 0.512 16 0.105 0.103 0.119 17 0.088 0.0069 0.356 18 0.0u3 0.0216 0.093 19 0.071 0.0079 0.105 20 0.19M 0.00u0 0.0hh 21 0.132 0.0234 0.316 22 0.137 0.0017 0.228 23 0.080 0.0099 0.159 2h 0.09M 0.0125 0.271 T This value was disregarded, because of proportion with the other values. —-———o it is completely out INTERPRETATION OF FACIES MAPS Methods of Geologic Interpretation Krumbein (N%i2)found that by superimposing isopach and fkacies contours, six types of patterns were evolved. These Eire illustrated in Plate 11, Figures 1 through 6, with the sc>lid lines representing the isopach lines and the dotted 1.ines as any specific lithologic ratio. In describing some of the patterns, Krumbein stated: 1. The linear subparallel [Plate 11, Figure 1] may occur under conditions where clastic sediments are spread over a subsiding area in decreasing amounts away from the source, so that the Clastic ratio lines tend to decrease as the isopachs increase, because of in- creasing lime deposition. 2. The curvilinear discordant pattern [Plate 11, Figure 3], may arise when a local concentration of clas- tics is poured into a subsiding area, as in a delta. Here the Clastic ratio lines may project farther into the basin than normally. 3. The concentric ovate pattern [Plate 11, Figure A] is characteristic of evaporites in an intracratonic basin. h. The irregular spotty pattern [Plate 11, Figure 6] occurs near the deteriorating edges of sheet sands, where the accumulation becomes patchy or spotty. Within an intracratonic basin, such as the Michigan 13asin, Krumbein (1952) recognized three predominate patterns. The interpretatiOn of these patterns would infer the tectonic Conditions, which controlled deposition. The three patterns their related tectonics are: 26 27 PLATE I I RELATIONS BETWEEN ISOPACl-IS (SOLID) AND FACIES LINEs- (AFTER KRUMBEINJSSé) LINEAR LINEAR SUBPARALLEL DISCORDANT FIG- I FIG- 2 CURVI LINEAR COWENTRIC DISCORDANT OVATE FIG 3 FIG' 4 DISCORDANT IRREGULAR OVA‘I’E SPOTTY FIG . 5 FIG. 6 28 1. Curvilinear-discordant pattern, suggesting a nearby orogenic or epeirogenic source. 2. Concentric-ovate pattern, infers a nearby epeirogenic or orogenic source, or a possible distant source. 3. Discordant-ovate pattern, indicates a nearby or distant epeirogenic source. If there has been erosion after deposition, the rela- t.ionship between facies and isopachs may not be clear. The STLratigraphic unit being studied should have a conformable t;op for proper interpretation. A discordant trend of the ilsopach and lithofacies lines suggests a possible erosional Irather than depositional surface. Geological Interpretation By superposing the isopach over the individual facies nmaps, separate interpretations were possible. The different IRypes of structures resolved from the maps will be made in rmaference to the counties Of Michigan. The Clastic Ratio Map. Starting in the northeast sec— ILion of the Southern Peninsula of Michigan, the significant IDattern in the.Alpena, Montmorency area is represented by the Chirvilinear discordant type. Proceeding to the south and “mist, the pattern changes into the linear discordant type in (DScoda,.Alcona, Roscommon and Clare counties. The outline reverts to the curvilinear discordant type in Ogemaw county. The northwest and western parts of the southern penin— Strla are represented by a linear subparallel pattern. This 29 i.s recognized in Benzie, Mason and Lake counties. To the south, the prominent pattern is the linear Cliscordant variety. This pattern seems to be more dominent 111 the southwest, in Kent, Calhoun and Gratiot counties. In a. restricted area in the region of Livingston county, an in- \remted curvilinear discordant pattern is noted. The thickest accumulation of sediments is in Ogemaw crounty. If more control were available, a discordant ovate IDattern would have been present and this would suggest depo- sition in an intracratonic basin from a nearby epeirogenic or‘orogenic source. This seems quite feasible, because the linear discordant pattern which is found north, west and south of Ogemaw county, suggest a possible shelf area, with the sediments coming from a western orogenic source. The curvilinear discordant pattern is seen further Ilorth and south away from Ogemaw county, suggesting deep or shallow neritic conditions. The western side of the lower peninsula, with its lin- eear subparallel pattern, is characteristic of a shelf area ‘receiving its sediments from a nearby orogenic or epeirogenic source, or even possibly a distant source. The major structural trends determined from the elastic ratio map are summarized as follows: 1..A broad trough is noted from Cheboygan, south to Clare county, with the source of materials possibly coming from the northwest. 30 2. A possible ridge, extending from Newaygo county eaast to Tuscola county, averages 20 miles in width. 3. Another trough, but not quite as broad, in the \Iicinity of Clinton county, is receiving its sediments from 'the southwest. This trough is separated by a ridge, from the small, but not very deep, set of eastern troughs. Two (Sf these depressions are receiving their sediments from the Idortheast and the other trough received deposits from the southeast. The Evaporite Ratio Map. In the Cheboygan, Alpena area, the curvilinear discordant pattern is again present. From Ogemaw county and westward to Grand Traverse, and then South to the southern extent of Clare county, the linear sub- parallel pattern prevails. South of this line, the dominant :pattern is the curvilinear discordant type, except in a por— tion to the southeast, where a linear discordant pattern is recognized. Krumbein (1952) states, "the concentric ovate pattern is characteristic of evaporites in an intracratonic basin." It is conceivable that possible pre-Sylvanian erosion would have destroyed a concentric ovate pattern in the southwest. The curvilinear discordant and linear subparallel pat- terns indicate a probable shelf deposition from a nearby orogenic source. The structural features represented on the evaporite ratio map are as follows: 31 1. A trough-like structure in Antrim county, with a source area of sediments from the north. 2. Another trough in the Crawford, Wexford areas, with the probable source of sediments from the west. 3. A fairly wide trough in the Oakland, Washtenaw area, \NhiCh received its sediments from the southwest. h. The prominent feature on the map is the concentra- tion of evaporites produced by basinal or restricted deposi- tion, in the vicinity of Kent, Clint, Newaygo, Montcalm and Gratiot counties. This deposit has a northwest trend. The Chert-Carbonate Ratio Map. .A curvilinear discord- ant pattern is again seen in the vicinity of northern Otsego and Cheboygan counties. Proceeding south or west, a linear discordant pattern seems to cover the major portions of the remaining area. Some spotty, linear subparallel patterns appear, such as in the south central area, around Livingston and Ingham counties, .but they are not as clearly defined as the particular linear discordant type. The pattern in the Cheboygan area, shows a possible deeper section, which received the sediments. This deeper intracratonic area is bordered on the south and west by a possible shelf feature. There is also the possibility that a discordant ovate pattern would have appeared again in the Ogemaw area, if more control indicated closure of the isopach lines. 32 The structures of the chert-carbonate ratio map are: 1..A trough in the Cheboygan, Otsego area, which was f‘airly broad, and trending to the southwest. 2..A second trough was found in Monroe and Washtenaw czounties. GEOLOGIC HISTORY With the knowledge of the features that have been Iolrought out by the facies maps, the various structural forms axssociated with the area, and the paleontologic forms that riave been recognized and identified within the formation, an erttempt will be made to reconstruct the geologic history im- rnediately before and during Bois Blanc time. The Silurian period closed very quietly in the Michi- gan.Basin. The epeirogenic sea that occupied the area was IDartially isolated and fairly warm. These features are at— ‘tributed to the deposition of the Bass Island formation. An unconformity exists between the Bass Island and 'the Garden Island formations. The correlative of the Garden I sland, the Oriskany sandstone in eastern New York, was de- E>osited on eroded Lower Devonian strata. This correlation C2an be observed in Table 1. .As you trace the formations VJestward to southwestern Ontario, the Oriskany strata lie Ciirectly on Upper Silurian sediments. This suggests the F>ossible conclusion that one of the first inundations of the [Devonian sea deposited these sediments in New York and also in.the Michigan Basin area. Withdrawal of the sea, accompanied by some subsidence in the eastern New York area, and subsequent erosion of some Of the sediments, opened the way for the deposition of the 33 3h Oriskany (New York) and the Garden Island (Michigan) forma- tions. An erosional unconformity also exists, but not quite as sharp between the Garden Island and the Bois Blanc forma- ‘tions. Small, low areas of the Garden Island formation re- rnained in the northern portion of the southern peninsula, and unare not subject to complete erosion. This would account for ixts patchy and restricted distribution. The major structural features that surrounded the Mich- iggan Basin, and were present during Bois Blanc time are: Tdde Cincinnati Arch to the south with its two limbs, the Ptankakee (?) to the southwest and the Findlay to the south- ezast; the Wisconsin Dome to the west, and the Canadian Shield Complex to the north. The Kankakee and Findlay arches started to rise in Eiarly Devonian time, and were well established at the con- <:lusion Of the Devonian period. The post-Garden Island emergence and erosion interval \das followed by widespread inundation of the Onondaga sea. 'The Bois Blanc formation was deposited in this sea, covering ‘the remnants of the Garden Island and the twice eroded Bass Island (pre-Garden Island and pre-Bois Blanc) sediments. Chert and dolomite are abundant in the lower portion of‘the Bois Blanc formation. The chert in this sectioncmcurs in.irregu1ar masses, beds, and nodules. Some speculation has lbeen made as to the origin of chert. Twenhofel (1950) stated 35 that nodular and irregular masses of chert can be attributed to primary deposition. He also attempted to correlate these cherty deposits with river mouths. Pettijohn (1957) regards Inost of the chert nodules and discordant masses as secondary and.of organic or metasomatic origin. Landes, Ehlers and Stanley (l9h5) discovered the reef fkarming coral, Favosites, present in the chert section. This Hiight be indicative of a biohermal structure. The middle section of the Bois Blanc formation is com- puased oflimestones, dolomitic limestones,and irregular masses 012 nOduIes of chert. Landes, gt _1. (1945) described this jpc>rtion of the formation as being highly fossiliferous, and C<>rrelated these fossils with the fauna of Lower Onondaga age Of7 sOuthwestern Ontario and New York. The upper portion is predominately limestone. Landes, 355 El: (19h5) recognized a southwest trending biohermal struc- tllfe in the vicinity of Mackinaw City. Erosion of the area, following the withdrawal of the (Dnondaga sea to the east, removed most of the Bois Blanc for- Ination from the flanks of the Kankakee and Findlay arches. 'The surface that remained, was subsequently covered by Syl- *— I \iania or higher Detroit River strata. CONCLUSIONS The geologic interpretation of the various facies maps, and other information substantiated the idea of a stable shelf (zondition in the western side of the Michigan Basin. .A few of tflde important reasons are listed below: Minor amounts of detrital material. 2. Abundant silt-size quartz. 3. Marine limestone, containing highly spherical quartz grains. h. Biohermal structures. 5. Linear subparallel pattern. Minor downwarping of the Michigan Basin also took place during Bois Blanc times. The concentration of evaporites in the southwest portion of the Southern Peninsula of Michigan, indicates a lagoonal type of environment might have been present. The basin deepened to the east, and the invasion of the LBois Blanc Sea was from the east. The basin was receiving sediments from all of the struc- tures surrounding the basin. The greatest thickness of sedi- Inents seem to have been derived from the Wisconsin Dome region. Pdinor amounts of sediments were also-being received from the (Canadian Shield complex. 36 SUGGESTIONS FOR FURTHER STUDY In the process of doing this research, many problems confronted the author. It is felt that some of these problems are in themselves, individual theses. More research should be done with chert. Quite a few articles have been written on the subject, but its possible origin is still in doubt. If the proper equipment is available, the new study of super-sonics, as applied to problems in sedimentation or other geologic fields, may prove of immense value. 37 REFERENCES Dice, B. B., (1955). "A.Quantitative Study of Composite Devo- nian Lithofacies in the Michigan Basin," Unpublished Master's thesis, Michigan State University, E8 pp. Eardley,.A. J., (1951). Structural Geology of North America. New York: Harper Bros., pp.7h-37. Green, D., (1957), "Trenton Structure in Ohio, Indiana and Northern Illinois," Bull. Amer. Assoc. Petrol. Geol., Vol. kl, pp. 627-6h3. Krumbein, W. C., (1952). "Principles of Facies Map Interpre- tation," Iour. Sed. Petrology, Vol. 22, No. B, pp. 200-211. Krumbein, W. C., (19h8). "Lithofacies Maps and Regional Sedi- mentary—Stratigraphic Analysis," Bull. Amer. Assoc. Petrol. Geol., Vol. 32, pp. I909-192h. Krumbein, W. C., and Sloss, L. L., (1951). Stratigraphy and Sedimentation. San Francisco: W. H. Freeman and Co., L97 pp. Krumbein, W. C., and Pettijohn, F. J., (1938). Manual of Sedimentary Petrography. .New York: Appleton-Century- Crofts, 5R9 pp. Landes, K. K., (1951). "Detroit River Group in the Michigan Basin," Geological Survey, Circular 133, 23 pp. Landes, K. K., Ehlers, G. M, and Stanley, G. M., (19h5). "Geology of the Mackinac Straits Region," Michigan Geological Survey, Pub..hh, 20h pp.. Milner, H. B., (l9h0). Sedimentary Petrqgraphy. London: Woodbridge Press Ltd., 666 pp. Moore, R. C., (19k9). "The Meaning of Facies," Geol. Soc. Am., Mem. 39, pp. 1-3h. Newcombe, R. B., (1933). "Oil and Gas Fields Of Michigan," Michigan Geological Survey, Pub. 38, pp. 1-l2h. 38 39 Pettijohn, F. J., (1957). Sedimentary Rocks. New York: Harper and Bros., 718 pp. Pirtle, G. W., (1932). "Michigan Structural Basin and its Relationship to Surrounding.Areas," Bull. Amer. Assoc. Petrol. Geol., Vol. 16, pp. 1&5-152. Tarr, W. A., (1938). Terminology of the Chemical Siliceous Sediments. Report of the Committee on Sedimentation, National Research Council, pp. 8-27. Twenhofel, W. H., (1950). Principles Of Sedimentation. New York: McGraw-Hill. ‘Weigner, G., (1927). "Method of Preparation of Soil Suspen- sion and Degree of Dispersion as Measured by the Weigner-Gessner Apparatus," Soil Science, Vol. 23, pp. 377-390. (Translated by R. M. Barnette) I/oc-I“ 81’ W5 : 17L [VIA/5 ' Demco-293 m .A. e . R M m _ E W B A 2 m _ will-I R IL N E S m u R ob E w M M Tu m _ 0 0 w w... w m N I s M . P B 0 N c m A 1 e u o- e W. P M H o... I... A o 8 es m. 0?? _ ONV 83° 85° 87° """""""'l mIU C m. m _ NI M ._ _ L H R & m. m _ E H F m N .1. m .N. _ C O R U A A win. I . .1“ S E S F mm m M S m w w o H R L P M . m e .2 a ovv omv 83° 85° 87° CH ERT— CARBONATE RATIO OF BOIS BLANC LOWER PENINSULA OF MICHIGAN SCALE 30 J 20 IO MlES INTERVAL = ISOPLETH ovv '-~ 4~..._. ,2 . "no—r ISOPACH 0F BOIS BLANC LOWER PENINSULA OF MICHIGAN N SCALE 1‘0“ L 0, IO 20 30 MILES ISOPLETH INTERVAL IOO' MICHIGAN STATE UNIVE I III I||IIIIIIIIW O 61 3 1293 30 5490 III“