—————-—.' .— - n — ‘ LITHOLOGEC S'EUDY OF A CAMBlOvORDOVIClAN CORE DELTA COUNTY. MICHIGAN Thesis for flu Degree of M. S. MECEEGAN STATE UNEVERSETY Richard A. Dixon 1961 - ... .‘ 77- IIIIIIIIIIIIIIIIIIIIIIIIIII iVIHWIHIIHHIIHHHIUIHHIIIIllllfilllllllllllllllllllHl _ L - 3 1293 1057.5 1212 F) LIBRARY L' Michigan State 1 University fimfi‘s UM‘ M—v—mzs T‘T 2‘ ”[L f" . . “r ‘fflfi‘f 1971;) m ,\ ’,1 ,f,‘ M «WI T?“*’?,, / ”4939fi.‘ Ii MICHIGAN STATE UNIVERSITY DEARTMENT OF GEOLOGY EAST LANSING MlCHIGAN LITHOLOGIC STUDY OF A CAMBRO-ORDOVICIAN CORE DELTA COUNTY, MICHIGAN BY Richard A. Dixon A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geology 1961 ii ACKNOWLEDGEMENTS The author is deeply grateful to Dr. C. E. Prouty, Head of the Department of Geology, Michigan State Univer- sity, under whose general guidance the problem was undertaken. Sincere appreciation is extended to Dr. B. T. Sandefur and Dr. H. B. Stonehouse for their constructive suggestions, encouragement and critical examination of the manuscript. Special thanks are offered to R. M. Ives, W. E. Mantek and A. Slaughter of the Michigan Geological Survey, who generously furnished the core, well samples and information essential to this study. TABLE ACKNOWLEDGEMENTS . . . . . . LIST OF ILLUSTRATIONS . . . INTRODUCTION . . . . . . . . General Nature and Scope LABORATORY METHODS . . . . . Samples Studied Laboratory Procedures LOCATION OF AREA . . . . . . GENERAL STRATIGRAPHY AND NOMENCLATURE DEVELOPMENT REGIONAL STRUCTURE . . . . . LITHOLOGY OF THE CORE . . . OF CONTENTS STRATIGRAPHIC IMPLICATIONS OF THE CORE . GEOLOGIC HISTORY . . . . . . SUMMARY AND CONCLUSIONS . . BIBLIOGRAPHY . . . . . . . . APPENDIX . . . . . . . . . . iii Page ii vi Hidia ll 26 28 48 58 63 67 73 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 10 ll 12 13 LIST OF ILLUSTRATIONS Correlation of Ordovician and Cambrian Formations of the Michigan Bas in O O O O O O O O O O O O O O O O O 0 Index Map — Location of Delta County, Michigan . . . . . . . . . . . . Location of Area and Samples studied 0 O O O O O O O O O O O O O O O 0 Development of the Ordovician and Cambrian Nomenclature of Northern Michigan . . . . . . . . . . . . Tentative Age and Correlation Of the Core 0 O O O O O O O O O O O O O 0 Proposed Correlation of Ordovician and Cambrian Formations of the MiChigan Bas in . O O O O O O O O O O O 0 Cumulative Frequency Curve. Glenwood Zone. TVD 225 Feet . . . . . . . . . . . Cumulative Frequency Curve. St. Peter Sandstone. TVD 233 Feet . . . . . . . . Cumulative Frequency Curve. Jordan Sandstone. TVD 345 Feet . . . . . . . . Cumulative Frequency Curve. Franconia Sandstone. TVD 492 Feet . . . . . . . . Cumulative Frequency Curve. Dresbach Sandstone. TVD 528 Feet . . . . . . . . Grain-Size Distribution of the Sandstones in the Core . . . . . . . . . . . . . . . Grain—Size Distribution of the Sandstones in the Core . . . . . . . . . . . . . . . iv Page 10 12 49 64 93 94 95 96 97 98 99 Table Table Table Table LIST OF TABLES Lithology of the Core . Depth Conversion in Feet Heavy Minerals of the Core List of Samples Page 74 86 87 91 INTRODUCTION General The interval including the Upper Cambrian through Middle Ordovician has been investigated lithologically by a number of workers in Michigan and surrounding areas. The results of the early and more recent investigations have led to a confused regional nomenclatural picture. A twofold classi- fication has evolved between the Northern and Southern Peninsulas of Michigan (figure 1). Michigan State University was fortunate in obtaining a key core from this sequence of rocks thereby making a litho- logical study possible. Nature and Scope The core under study is from a geographic location favor- ably situated to offer comparison between the Southern Peninsula subsurface rocks and the highly problematical stratigraphy of the Northern Peninsula outcrop of the "Her- mansville" and "Au Train" terranes. The core gives a con— tinuous picture of the interval from Middle Ordovician through early Upper Cambrian and cannot be duplicated in any known single outcrop in Michigan. It is hoped that a detailed lithologic study of the core using petrographic, mineralogic E 3 Michigan Basin m $T Northern Peninsula Southern Peninsula Trenton Trenton Black River Black River Glenwood St. Peter SS : o g Shakopee Dolomite U -a 8 @ New Richmond SS H O Hermansville (Au Train) Oneota Dolomite Prairie du Chien Group Jordan SS Lodi Dolomite Trempealau Formation ’//_ St. Lawrence Dol. g Franconia 88' -H B a Munising SS E Dresbach SS m H»~ (Eastern part) 0 O u "-4 H H m - m m Eau Claire SS a 5 C m H w 3 Mount Simon SS x m S Q J' b '11 SS a . " co 5V1 e JacobSVille (?) (Eastern part) (In part after Cohee and Bridge) Figure 1 Correlation of Ordovician and Cambrian Formations of the Michigan Basin. and sedimentary techniques may, through comparison with other subsurface wells and outcrop sections, help clarify the correlations throughout Michigan and surrounding areas. The paleontological aspect was not included in this study. However, it is presently being undertaken by another student at Michigan State University. LABORATORY METHODS Samples Studied This problem was primarily a laboratory study and all work was conducted at the Geology Department, Michigan State University. Samples from the core were taken at approximately ten foot intervals for the heavy mineral studies. Selection of samples for grain size analyses and thin section studies was determined by the megascopic variation in the lithology. Most samples for comparison purposes were supplied by the Michigan State Geological Survey in Lansing, Michigan and consisted of rotary and cable tool well cuttings. A few well cores were available for examination at the Michigan State Geology Department. Outcrop samples collected by Dr. C. E. Prouty from Northern Michigan were available to the author and were included in the investigation. A complete list of sample wells observed in this study may be found in the appendix. Laboratory Procedures Suggestions for preparation of samples for the following Stlldies were obtained from Krumbien and Pettijohn (1938). Mechanical analyses of size grades coarser than l/l6 mm werfle made with a standard set of Tyler sieves. Approximately one hundred and twenty-five grams of sample were shaken for a period of ten minutes in a Rotap Automatic Shaking Machine. The fraction of sample from each sieve was weighed and cumu- lative frequency curves were constructed on three-cycle semi—logarithmic paper. Statistical data were calculated from measures obtained from the curves: Quartile l = Q l Quartile 2 = Q2 = Median Quartile 3 = 03 Sorting = so =W/ 01/03 Skewness = SK = QlQ3/ (Mdz) Tetrabromethane was used in all heavy mineral separations. The l/8 mm to l/l6 mm grade, or a representative fraction thereof, was selected for analysis. The heavy fraction of this size grade was examined with binocular and petrographic microscopes. At least two hundred grains were counted from each fraction. Authigenic and secondary pyrite occasionally constitutes a large part of the heavy mineral fraction and was excluded from the calculations employed in construction of Table 3. Standard procedures for producing thin sections were followed. 6 The core under study extended through an interval from Middle Ordovician to Upper Cambrian. Therefore, study of available cuttings from other wells considered only this interval. Descriptions of the properties of the above- mentioned samples were based primarily on Low's Examination of well Cuttings (1951) and Whiteside's Geologic Interpreta— tions from Rotary Well Cuttings (1932). The following descriptive data regarding size of particles were adopted in this work: Sandstone Size: Very fine (.O62-.125 mm), Fine (.125-.250 mm), Medium (.250-.50 mm), Coarse (.50-1.0 mm), Very coarse (1.0-2.0 mm). Limestone and Dolomite Size: Very fine (invisible to .05), Fine (.05 to .25), Medium (.25—2.00), Coarse (over 2.00). The microscopic descriptions supplemented the megascopic examination and are included in the lithologic description of the core. The core was drilled at an angle of forty—five degrees and the measured depth (MD) was converted to true vertical depth (TVD). A list of samples, lithologic descriptions, heavy mineral conversion table, histograms, cumulative frequency curves and depth conversion table may be found in the -appendix. cmmHSUHE .mucsoo muamo mo coflumuoqllmmz xwpaH m musmflm muoo mo cofipmooH mumEonnmmm x A 32.3522 7 zonzzoa 1);} I . a/\ upkmsom -r-I 'r'I Au gHer x er ‘3 In rem- .'> :> . r((gmans-(Is mans ‘0 Spea- r8 8 Train Hville N ville - Trem- Eleau 5' Her- 5 O O '2 pea- w mans- q m. m z . 2 U leau Jordan I Ville (L 0rd) Trem— Fran- . ea- 0 'a _ m' _ Muni- p C “1 Fran e:?s a sing c: leau conia a r3 - g M Dres— f3 (SIS- ' - azo- H 0‘ e g E mania M . ' ghaCh g g gw’ . uniSin - - - {IL—'8 (“unl‘ g .3 L”. 8 .‘2 Cha— sing) (Fran- c: c: x: H H conia) 5 g 8 g pel “aflJa- 8. Dres- zEau 0. Rock Dacobs— Q. bach Claire 8‘ ‘3 ville D (LMUI’I- Dres— ISlng bach Jacobs- Jacobs- - Ville Ville : E-Q Jacobs- H ” ville 0% m A U a {Boobs- Jacobs- g ville Ville m :2 (Bay- Freda Freda (Bay- Freda m field) Freda field) g m x Freda H Freda w E [_ D __J Adapted from Hamblin (1958) 13 Walcott for the basal formation of the Saint Croixan series which was described as coarse sandstone and grit resting on the Precambrian surface (Trowbridge and Atwater, 1934). The Mount Simon is recognized in southeastern Michigan and reported to be 300 feet thick (Cohee, 1945a). According to Thwaites (1934), subdivision of the sandstone interval between the highest clean white sandstone (Dresbach) and the underlying Precambrian in northern Michigan is impracticable. Eau Claire Sandstone The term, Eau Claire, was first used by Wooster (1882). It is of Upper Cambrian age and named for exposures along the Eau Claire River, Eau Claire County, Wisconsin. In southern Michigan the Eau Claire consists of sandstone, shale, and a sandy, shaly dolomite; while in northern Michigan it is reported as entirely sandstone (Cohee, 1945a). Dresbach Sandstone The term, Dresbach, was proposed by Winchell (1886) for the beds of gray micaceous sandstone of Upper Cambrian age at Dresbach, Minnesota. The term has been used as a formation by some workers who then include Galesville, Eau Claire, and Mount Simon as members. A coarse sandstone, approximately lCND feet thick with thin dolomite beds has been recognized as Dresbach in southern Michigan by Cohee (1945a) . l4 Dresbach has been identified by Thwaites (1934), Cohee (1945a), and Oetking (1951) in the Northern Peninsula of Michigan but indicate it may be locally absent in some areas. Franconia Sandstone Berkey (1897) named the Upper Cambrian Franconia forma- tion from the Village of Franconia, Minnesota where beds characterized by abundant glauconite overlie the Dresbach formation. According to Cohee (1945a) the Franconia is thin in southeastern Michigan and is represented in the Northern Peninsula by a gray to pink sandstone from 10 to 90 feet thick containing glauconite and pyrite. Thwaites (1934) and Oetking (1951) state that the Franconia extends into north- ern Michigan. Munisinq Formation Lane and Seaman (1907) proposed the term Munising sand- stone for the upper 250 feet of the Lake Superior sandstone near Munising, Michigan. The Munising sandstone is considered to be equivalent to the Dresbach, Mazomanie (Franconia) and Trempealeau by Thwaites (1934) and Martin (1936); Franconia by Thwaites (1934); Eau Claire, Dresbach and Franconia by Cohee (1945a); Dresbach and Franconia by Oetking (1951). Driscoll (1956) and Hamblin (1958) subdivide the Munising SHandstone into the Basal Conglomerate, Chapel Rock, and Miner' 5 Castle members . 15 Au Train Formation Grabau (1906) introduced the term "Auxtrains” to northern Michigan stratigraphy and stated: In the Iron Mountain region Upper Cambric fossils are recorded from the basal sandstone, but this does not prove that the basal sandstone of Marquette and the pictured rocks is of the same age. In fact, from their position with reference to the transgression of the Cambric sea, these more northern sandstones must be regarded as of later age than that of the Menominie district. If the Hermansville limestone (Auxtrains formation would be a better name, from more typical exposures on that stream) proves eventually to be Beekmantown rather than Chazy (that is, Upper Stone River or Lowville), the late Cambric or early Ordovicic age of part of the Superior sandstone must be conceded. From studies of the south shore of Lake Superior, Oetking (1951) applied the term "Au Train" as a local or temporary designation of the Middle Ordovician strata which lie between the Munising sandstone and Trenton group. Oetking concluded that: The Au Train formation of the Lake Superior coast, previously termed Hermansville or "Calciferous" and thought to be Upper Cambrian or Lower Ordovician, contains fossils which correlate the strata of that locality with the Lower Middle Ordovician (Platteville) of the Wisconsin section. Due to the overlap of the Black River dolomite, the St. Peter, Lower Magnesian and Trempealeau of the Wisconsin section appear to be absent on the south shore of Lake Superior according to Oetking. However, he has rec0gnized 16 the Lower Magnesian and Trempealeau in wells farther south. Hamblin (1958) working with Cambrian sandstones of northern Michigan, implied that throughout the Northern Peninsula the Munising formation is overlain by a sequence of sandy dolomites and dolomitic sands. Following Grabau, he proposed that "Au Train" formation be used for these rocks, as the best exposures and thickest sections are at Au Train Falls in Alger County. A Middle Ordovician age was applied to the Au Train formation by Hamblin on the basis of some gastropods and cephalopods found in the unit. For this reason he thought that the Lower Ordovician and parts of the Upper Cambrian are missing in the area covered by his report. Hermansville Formation The youngest formation in the Menominee, Michigandistrict consists of a coarse—grained sandstone with abundant calcareous cement in alternation with pure dolomite or sometimes oolitic beds. 11: was named "Hermansville" by Van Hise and Bayley (1900). A.brief description of the type locality was included in their report; however, it is not clear just what type locality the authors had in mind. Smith (1916) reported that the Calciferan or Lower Magnesian sandstone, or possibly only the lower part of it, 17 is represented by the Hermansville limestone in wells along Green Bay. The "Geologic Map of the Northern Peninsula of Michigan" compiled by Martin (1936) indicates the Hermansville, a dolomitic sandstone, overlies the St. Croixan and is considered to be Ozarkian or Canadian. Bergquist (1936) reported that the Hermansville forma- tion, which lies unconformably over the sandstone of the Cambrian system, is younger and undoubtedly belongs to the Ozarkian. Thwaites (1943) suggested that the Hermansville appears to embrace all strata which Rominger (1873) termed "Calciferous" and "Chazy," that is, '2 . . both the Trempealeau and the Lower Magnesian." As the Hermansville is so poorly defined and apparently includes the Trempealeau and Prairie du Chien Thwaites proposed that the term should be abandoned. The questionable age and vague nomenclature applied to the sequence of rocks overlying the Cambrian sandstones and underlying the Middle Ordovician in the Northern Peninsula remain as a primary problem in stratigraphy within Michigan and the surrounding area. l8 Trempealeau Formation The Trempealeau formation, proposed by Ulrich (1924), is named for exposures at Trempealeau, Trempealeau County, Wisconsin. In Michigan the Trempealeau formation is sub- divided in ascending order into the St. Lawrence, Lodi and Jordan sandstone members. The Trempealeau formation consists predominantly of dolomite, sandy in parts, with minor amounts of shaly dolomite and dolomitic shale in southeastern Michigan and is primarily a sandstone and dolomite in the Northern Peninsula (Cohee, 1945a). St. Lawrence Member The St. Lawrence was named for exposures at St. Lawrence, Scott County, Minnesota by Winchell (1874). The St. Lawrence is a gray, sandy, very glauconitic dolomite overlain by dark gray to black dolomitic shale and dolomite in southern Michigan and is similar in the Northern Peninsula according to Cohee (1945a). Lodi Member The term "Lodi" was proposed by Ulrich (1924) for the yellow calcereous shale-like sandstone presumably exposed at Lodi, Columbia County, Wisconsin. The Lodi member is primarily a dolomite, somewhat sandy in Michigan. Cohee (1945a) recognized the unit in southeastern Michigan but not in the Northern Peninsula. 19 Jordan Sandstone Member The Jordan sandstone was named by Winchell (1874) for the exposures at Sand Creek near the town of Jordan, Scott County, Minnesota. Cohee (1948) reports a well—developed sandstone with well—rounded, pitted and frosted quartz grains in the North- ern Peninaula of Michigan. The sandstone is not generally recognized in southeastern Michigan. Thwaites (1934) indi— cates the Jordan is missing over much of the Northern Penin— sula and that the Ordovician-Cambrian boundary occurs at the top of the prevailingly red or pink, non—cherty, sandy dolomite which is overlain by a gray, cherty dolomite (Prairie du Chien). Prairie gE_Chien Group The Prairie du Chien group is classified as Lower Ordo- vician by the United States Geological Survey and includes Oneota, New Richmond and Shakopee formations, in an ascen- ding order. It was named for "exposures" in the vicinity of Prairie du Chien, Wisconsin (Bain, 1906). Kay (1935) reports that the Prairie du Chien consists mainly of dolomite but includes some sandstone and lies above the Cambrian and extends up to the St. Peter sandstone (Chazyan). 20 Oneota Dolomit§_ The Oneota was named by McGee (1891) for exposures on the Oneota River, Allamakee County, Iowa. According to Kay (1935) the Oneota dolomite includes the magnesian limestone succeed- ing the Cambrian Jordan sandstone and underlying the New Ridhmond sandstone. He reports the Oneota in Iowa as oolitic, conglomeratic, glauconitic and cherty dolomite at the base and overlain by light bluff, fine to medium textured, crystalline, evenly-bedded dolomite, succeeded by massive dolomite and chert. Cohee (1948) has recognized the Oneota dolomite in the Northern and Southern Peninsulas of Michigan. It consists of buff to brown dolomite, often sandy, oolitic, and cherty near the base. N_ev1 fichmond Sandstone The New Richmond sandstone was named for exposures at New Richmond, St. Croix County, Wisconsin by Wooster (1878). Heller (1956) reported the New Richmond member is represent- ed by fine to medium-grained quartzose sandstone,and firm to medium-grainedllight brownish-gray to buffIarenaceous dolomite. According to Cohee (1948) the New Richmond sandstone has been recognized from well cuttings in southwestern Michigan. Thwaites (1943) reported there are at least two 21 fairly persistent sandstone horizons within the Prairie du Chien group of northern Michigan: therefore, one should not attempt to apply a threefold division. Shakopee Dolomite The Shakopee dolomite was named for rocks exposed at Shakopee, Scott County, Minnesota. According to Heller (1956) the typical Shakopee dolomite is fine to medium- grained, light brownish-gray to buff, ranging from thin to thick—bedded. Chert is not a common constituent but when present it is an oolitic, arenaceous type. The beds succeed the New Richmond sandstone and are overlain by the St. Peter sandstone in the type locality. The Shakopee is present in southwestern Michigan according to Cohee (1948) and consists of dolomite, buff to gray, sandy in part,with thin beds of shale and small amounts of chert. As far as known the Shakopee dolomite has not been reported in the Northern Peninsula of Michigan. St. Peter Sandstone The St. Peter sandstone of Lower Ordovician age was named by Owen (1847) for exposures on the St. Peter River, now known as the Minnesota River, in southern Minnesota. The formation includes the sandstones succeeding the Prairie du Chien group and underlying the Glenwood shale 22 member of the Platteville formation (Kay, 1935). The forma- tion is composed of rather massive, white, medium-textured quartz sandstone that is quite friable with well—rounded and frosted grains. The St. Peter sandstone is generally absent in the Northern Peninsula and eastern Michigan according to Cohee (1948). The distribution of the St. Peter in western Michigan has been established from well samples. Thwaites (1934) indica- ted from his investigations that the St. Peter sandstone could not be identified in the Northern Peninsula. Horowitz (1961» after observing a core,reported that the St. Peter was approximately fifteen feet thick in Delta County, Northern Peninsula of Michigan. Glenwood Shale The Glenwood shale of Middle Ordovician age was named by Calvin (1906) for exposures in Glenwood Township, Winneshick County, Iowa. In the type locality the lower two-thirds of the shale is highly sandy with some thin beds of almost pure ' sand similar to that in the underlying St. Peter sandstone, whereas the upper part contains no sand. Weiss and Bell (1956) describe it as, "shale, sand, and sandy-shale," in Iowa and Minnesota. 23 Cohee (1945a) reports the Glenwood of southwestern Michigan to be primarily sandstone and sandy dolomite. He stated in his report: The Glenwood shale in some areas of Michigan may be transitional between the St. Peter sandstone and the overlying Platteville limestone or Black River limestone of Middle Ordovician age. Thwaites (1943) reports that in the Northern Peninsula of Michigan: The sandstone which immediately underlies the Black River dolomite of Limestone Mountain was found to be in large part fine-grained and apparently dolomitic. It is probably the Glenwood member of the Platteville dolomite. Horowitz (1961L on examination of well cuttings,conc1uded that the Glenwood was present in southern Michigan and recorded fifteen feet of sandy dolomite as Glenwood in Delta County, Northern Peninsula of Michigan. Black River Group Vanuxem (1838) named the Black River limestone from exposures along the Black River in New York. The Black River carbonates generally consist of brown and gray crystalline limestone and dolomite. Cohee (1948) reported the Black River in the Southern Peninsula of Michigan as light brown and gray, fossiliferous, dense to crystalline limestone and dolomite with the basal beds consisting of fine—grained dark gray to black argillaceous 24 limestone or of limestone and shale. Some chert fragments have been found in the Upper Black River. The Black River of the Northern Peninsula consists of buff to brown fine- grained crystalline limestone and dolomite. According to Hussey (1952), the Black River formation is represented by the Bony Falls member with excellent exposures along the Escanaba River, Delta County, Michigan. Trenton Group Limestone exposures at Trenton Falls, New York were named Trenton by Vanuxem (1842). In the Southern Peninsula of Michigan the Lower Trenton is lithologically similar to the Black River; however, in the Northern Peninsula it consists of buff to brown crystal— line limestone with some dolomite and gray to dark gray argillaceous limestone (Cohee, 1948). Exposures of the Trenton formation along the Escanaba River as reported by Hussey (1952), can be subdivided into three members, in ascending order the Chandler Falls, the Groos Quarry, and the Haymeadow Creek. Overlying the Trenton in Michigan are rocks of Upper Ordovician age consisting largely of gray and dark gray shale with minor amounts of dolomite and limestone. In southeastern Michigan Upper Ordovician rocks are divided into the Utica, Lorraine and Queenston shales in ascending order. Upper Ordovician outcrops in the Northern Peninsula are correlated in part with the Richmond formation. 25 26 REGIONAL STRUCTURE In describing the areal extent of the Michigan Basin, Newcombe (1933) stated: The area comprising the Michigan Basin 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. King (1951) proposed that: Drilling in the Michigan Basin reveals that nearly all formations from Cambrian to Mississippian thicken progressively toward its center, indicating that it was a persistent negative region subjected to long- continued subsidence. The rate of thickening varies from one unit to another, and the center of greatest subsidence shifted position slightly from time to time. According to Pirtle (1932), the structure is bounded by the Wisconsin arch on the west, and by two diverging limbs of the Cincinnati arch, the Kankakee arch to the south- west, and the Findlay arch to the southeast. A continuation of the Findlay arch, the so-called Algonquin arch in Ontario, forms the eastern boundary, and the complex Pre— cambrian rocks form a barrier to the north. The counties bordering the north shore of Lake Michigan are considered to be located along the north-northwestern flank of the basin where Paleozoic rocks of Ordovician and Silurian age from the bedrock surface. A discontinuous blanket of glacial drift of varying thickness overlies the 27 bedrock surface. The regional dip of the formations in Delta County is to the southeast at approximately forty feet per mile (Sinclair, 1960). 28 LITHOLOGY OF THE CORE A discussion of the lithology of the core is the main purpose in the following statements. The core under study has a diameter of two inches, therefore, represents a relatively limited sample for recognizing many of the sedimentary features. For ease of discussion and reference, each major litho- logic unit of the core was assigned a number. Unit I is the lowermost stratigraphically. A lithologic description of the core including the thickness of the units and sub- units has been compiled in Table l of the appendix. All references to depths applied to the core are true vertical depths, transposed from measured angle depth (Table 4). Haiti; Unit I, the lowermost 46 feet of the core consists of sandstone which grades in color from light brown, gray- white into a brownish pink near the base. The sandstone is well-sorted and predominantly medium-grained (figure 11 and 13). The unit is composed almost entirely of quartz grains. Coarser grains are subrounded and appear slightly frosted. Smaller grains tend to be more angular and clear, frequent- ly showing secondary overgrowth. Many of the quartz 29 grains contain gas bubbles indicating a possible igneous origin. Very minor amounts of feldspar and shale are present. Disseminated glauconite is noticeable throughout the unit and occasionally becomes concentrated in the thin shaly partings. The cementing material and degree of cementation vary considerably within the sandstone unit. Silica is the pre- dominant cementing material while calcium carbonate is limited to the upper portion of the unit. Often small angular quartz fragments constitute a matrix for larger grains there- fore acting as a clastic binder. It is primarily a friable sandstone occasionally becoming orthoquartzitic. Near the base of the unit scattered or floating fragments occur in the sandstone. These fragments vary in size, shape and color. The larger, 1-1/2'UD2 inch, fragments are angu- lar, red to reddish-purple iron formation and quartzite. White to milky, subangular vein quartz and quartzite and gray, fine-grained sandstone account for most of the remain- ing fragments. One small angular fragment of rhyolite and an occasional dark green slate fragment were found. The lower three Ext of the unit can be described as a conglom- erate consisting of the above—mentioned fragments with the addition of some weathered chert and green soapstone in a matrix of brownish-pink sandstone. 30 Most of the sandstone appears as if it were subjected to some type of burrowing organism as many round or oval-shaped holes occur quite frequently in the rock. They are often partially filled with a soft green clay. The heavy mineral suite of this sandstone unit consists pmimarily of zircon and tourmaline (Table 3). Zircon occurs generally as small, rounded, pink grains. Some light-gray zircon was present. Zircon increases in per- centage toward the base of the unit. Garnet, a pink to dark pink variety, is not abundant and decreases in percentage towards the base of the unit. Some of the garnet grains are well-rounded but many grains appear with a steplike pattern covering the surface. The pattern is a result of the development of crystal faces on the garnet grains. Tour- maline is abundant throughout the unit with brown to green wellsrounded grains being most common. Leucoxene occurs in appreciable amounts, often pitted on the surface of the well-rounded grains. Opaque minerals, ilmenite, pyrite and hematite, were present in minor amounts. Unit I Unit 11 is about 29 feet thick and consists of a light- gray to brownish-gray sandstone. Near the top and lower in 31 the unit the sandstone grades into a sandy dolomite. The grain size varies within the unit from very fine to very coarse, with an average of medium-sized grains (figure 10 and 12). Relatively poor sorting is characteristic of the unit. However, some well-sorted zones occur within the unit as illustrated by figure 10. Quartz constitutes most of the grains studied. Very minor amounts of feldspar and chert were found in the samples. Disseminated glauconite and pyritevmnmaespecially abundant near the top of the unit. Most of the quartz grains were well—rounded and the larger grains appear frosted. Subangular to angular, clear, occasionally pitted grains are more characteristic of the smaller size. Secondary overgrowths were quite common on the smaller grains but not as well developed as those of Unit I. Secondary quartz is the dominant cementing agent. The sandstone is friable to strongly cemented depending on the amount and nature of secondary quartz. Dolomite acts as the cementing material in the sandy dolomitic zones. The rapid increase in the percent of garnet and the sharp decrease of zircon is very evident in Unit II (Table 3). Some rounded garnet grains were noted. However, most of 32 the grains were pink to dark pink and covered with the step- like pattern so noticeable in Unit I. Black tourmaline was more common than the brown or green variety. Leucoxene, zircon and a very small amount of rutile were found. An increase in the amount of opaque minerals was significantly greater near the top of the unit. Authigenic pyrite consti- tutes the greatest amount with ilmenite and iron oxides comprising the remaining amounts of opaque minerals. There is no apparent change in litholOgy at the contact of Unit I and II which is placed at 515 feet in the core. A thin conglomerate band does occur near the base of Unit I but appears to be intraformational. The contact between Units I and II is drawn primarily on the significant change in heavy minerals, sorting and the size and character of the grains. 132.112. 1.1.1. Unit III shows a vertical change in lithology. The unit is 49 feet thick and grades from a greenish-brown into gray and pink towards the top. The base of Unit III is marked by a brownish-gray to green color and a thin conglomeratic zone of angular dolo- mite and sandy dolomite. It is primarily a poorly sorted sandstone, somewhat dolomitic, with thin interbedded 33 greensands. Disseminated glauconite occurs in the sandstone and occasionally is extremely abundant,forming thin greensands. Shaly beds containing silt and disseminated pyrite are common. The sand grains are very fine to medium grained with finer grains frequently showing secondary overgrowths. A few of the larger grains are rounded and frosted. Some feld- spar and chert particles were found. Overlying the greensands are gray sandy dolomite, grayish silty dolomite and dark gray to black shales. The shales and dolomite contain 1/4 to 1/2 inch pyrite bands and nodules. Authigenic pyrite often lines the vugs in the dolomite. Gray to pink, compact, relatively thick-bedded dolomite is more characteristic of the upper part of Unit III. The dolomite is medium to coarsely crystalline with very few euhedral crystals. Numerous vugs occur in the dolomite and are often lined with crystals. It is highly iron stained along the thin partings which may be old fractures or cracks. Pyrite is very abundant and may line some vugs. Glauconite and floating sand grains become less abundant towards the top of the unit. Other than pyrite and some iron oxides, garnet was the dominant heavy mineral. Near the top of the unit very few 34 heavy minerals were obtained with exception of the opaque minerals (Table 3). The pink to dark pink garnet grains are similar in appearance to those of Unit II. An increase in zircon and leucoxene and a decrease in tourmaline is evident as compared to Unit II. TThe contact of Unit II and III was placed below the highly glauconitic sands and conglomeratic zone at the base of Unit III, approximately 485 feet in depth. The degree of secondary overgrowths on the finer grains, fewer coarse, rounded frosted grains, extremely abundant authigenic pyrite, and the significant increase of zircon and leucoxene provide additional evidence for determining the contact between Unit II and III. 92.1.2.3: Most of Unit IV, approximately 74 feet thick, consists of a mottled buff and gray, silty to fine sandy dolomite with interlaminated calcisiltite and very fine quartz grains. The dolomite is generally very fine to medium crystalline and only occasionally coarsely crystalline. Most of the crystals are of an anhedral nature. The silt and very fine angular quartz grains are usually buff whereas the dolomite tends to be more gray. 35 Very few small vugs are scattered throughout the unit. Occasionally thin black shaly partings contain glauconite. Glauconite was not abundant but recognized throughout the unit. Thin and reddish iron stained streaks give the rock a banded appearance, especially in the silty beds. These reddish stains appear to be along the bedding surface and are probably due to the oxidation of iron sulfide. The lower part of Unit IV is relatively barren of heavy minerals with the exception of abundant pyrite and iron oxides (Table 3). Towards the top of the unit garnet becomes the dominant mineral comprising nearly 80 percent of the heavy mineral suite. The remaining 20 percent is composed of zircon, tourmaline and leucoxene. Pyrite is also abundant near the top of the unit. The garnet grains are very simi- lar in appearance to those of the lower units. The contact between Units III and IV is not sharp but rather transitional. The criteria for placing the contact between these two unitsaue based primarily on the differences of the dolomite. Unit III is a gray to pink, vuggy, medium to coarsely crystalline dolomite with a few thin buff, iron- stained silty beds. In contrast, Unit IV is buff to 36 gray, very fine to medium crystalline containing numerous interbedded iron-stained, silty and very fine grained quartz laminae. Heavy minerals are not diagnostic in placing the contact between these units as they are composed almost entirely of pyrite and iron oxides. The division of the units is drawn at approximately the 436 foot mark. MY. Interbedded sandstone, dolomitic sandstone and sandy dolomite comprise 19 feet of the core which is assigned as Unit V. The unit grades in color from light brown to brownish-gray. A sample from a good sandstone bed was taken for a grain-size analysis (figure 9 and 12). The results indicate the majority of grains are medium size; however, they range from coarse to fine. Many of the grains are well-rounded and appear etched possibly due to carbonate solutions. Some of the quartz grains suggest secondary overgrowth as crystal faces can be detected. Occasionally the sandstone is firmly cemented. The sandy dolomite is fine to medium crystalline containing fine to medium, rounded to angular quartz grains. The dolomite crystals range from anhedral to euhedral in outline. 37 Glauconite and some pyrite appear in thin dark shaly partings. An occasional feldspar grain was noted. Pink garnet comprises up to 90 percent of the heavy minerals. Very few rounded garnet grains are present. The appearance of most of the garnet grains are identical to those described in the lower units with the major difference being the absence of the dark pink variety. Well-rounded almost clear to light-gray zircon, brown to green tourmaline and leucoxene comprise most of the remaining 10 to 20 per- cent of the heavy minerals. A few grains of augite, rutile and epidote are found. The contact between Unit IV and V is of a gradational nature and was placed at approximately 363 feet on the core. This depth marks the first good, clean sandstone bed that appears to be more characteristic of Unit V, whereas below this point the fine sand and silty dolomite are more apparent. HEEL 1E The upper half of the unit is grayish, compact to vuggy, very fine to medium crystalline dolomite. It may be sandy or only occasional floating fine angular quartz grains are .present. There are some thin sandy beds and occasionaly thin greenish to dark gray shaly beds and partings. 38 The lower part of the unit becomes more of a sandy dolo- mite with fairly thick interbedded dolomitic sandstones. A range of fine to coarsely crystalline dolomite becoming oolitic towards the base is more typical of the lower part of the unit. The well-developed oolites appear to have quartz silt nuclei. A few vugs often lined with fine masses of dolomite crystals are present. The dolomite sandstone medium to coarse grained, is fairly well cemented. The grains are well-rounded to subangular and occasionally appear etched or frosted. Light-brown to medium-gray porcelaneous to oolitic chert cxxxmring in irregular masses and nodules is present near the base of the unit. Some thin silty, glauconitic, greenish shaly beds and partings are noticeable especially near the base. Very little iron or limonite stains this unit. Feldspar, pyrite and muscovite appear in very minor amounts. The heavy mineral content varies considerably within the unit. Garnet, the dominant heavy mineral, ranges from 40 to 80 percent of the heavy mineral suite (Table 3). The upper middle part of the unit contains the least garnet. Many of the garnet grains are large enough to identify with the 39 unaided eye. They are pink and characterized by the steplike pattern on the surface. Black, brown and green tourmaline, light-gray to colorless zircon and leucoxene comprise the bulk of the remaining heavy minerals. However, towards the middle of the unit, hornblende, epidote, kyanite and rutile are present in quantities from 0 up to 10 percent. The contact between Unit VI and the underlying Unit V appears to be a transitional one as sandy beds similar to those of Unit V occur into Unit VI. The contact is drawn at approximately 345 feet as this marks the lowermost chert and underlying thin shaly zone of Unit VI. warm Approximately 11 feet of light brown to brown, medium- grained sandstone composes Unit VII. There are a few shaly, sandy, vuggy crystalline dolomite zones within the unit. Irregular masses of secondary light buff dolomite occur near the base of the sandstone. Numerous secondary overgrowths of the quartz grains are very well-developed. Secondary quartz is the main cementing agent and the rock could be called an orthoquartzite. Very few rounded, frosted grains are present; most grains are extremely clear and angular. 40 Garnet remains as the dominant heavy mineral comprising 90 percent of the total (Table 3). Many of the pink garnet grains could be seen megascopically. A well-developed step- like pattern was prevalent on most grains. The remaining ten percent of the heavy minerals consisted of zircon, tour— maline and a small amount of leucoxene. The contact between Unit VI and VII was placed at about the 265 foot mark. A change in lithology from a grayish dolomite into a rather thick brownish quartzitic sandstone was the determining factor. Possible additional evidence is the larger size and greater abundance of garnet. Also, hornblende and epidote were absent in Unit VII. Unit VIII Unit VIII, approximately ten feet thick is predominantly a light-brown to gray sandy dolomite with some dolomitic sandstone and thin greenish shaly beds and partings. Fine to medium quartz grains are characteristic of the lower parts of the unit grading into medium to coarse grains toward the top. Some of the larger grains are subrounded and appear slightly frosted; smaller grains are clear and angular. The sandstone is firmly cemented and dolomite is the cementing agent. 41 The dolomite is fine to coarsely crystalline with many anhedral crystal outlines. Fine to medium subangular quartz grains are incorporated in the dolomite. Garnet, with the same characteristics of those in lower units, is the dominant heavy mineral and constitutes about 90 percent of the total (Table 3). A small quantity of colorless zircon and brown-green, well-rounded tourmaline account for ten percent of the heavy minerals. Leucoxene appears to be absent from this unit. Unit VIII appears transitional with the underlying unit. It therefore poses a problem as to whether it should be desig- nated as a definite lithologic unit and, if so, where the contact should be placed. However, there are some notice- able differences and a tentative contact between Units VII and VIII is placed at the 254 foot mark on the core. Below this point the very firmly cemented quartzitic sandstone of Unit VII predominate whereas above the sandy dolomites prevail. The increase in size of the quartz grains, fine to coarse, from the base towards the top of Unit VIII and the absence of leucoxene may be pointed out as features differing from Unit VII. 42 Unit Lg Light brown sandstone and sandy dolomite, approximately 16 feet thick, comprise Unit IX. A sandstone with many well-rounded to sub-rounded, frosted quartz grains occurs near the top of the unit. Frequently secondary overgrowths are shown on the smaller quartz grains. Many of these crystal faces appear pitted. Grain-size distribution ranges from fine to coarse with the majority of grains being medium sized (figure 8 and 12), but on the larger size end of the medium size range. The sandstone is generally friable with dolomite and silica acting as the cementing agent. Lower in the unit, very sandy dolomite with thin inter- bedded sandstone and greenish shale predominate. The dolo- mite is fine to coarsely crystalline and occasionally vuggy. Anhedral crystal outlines are most common. Quartz grains within the dolomite are fine to coarse, rounded to angular. At the base of the unit a grayish dolomite appears to be conglomeratic. Very coarse sand grains and pebbles, consist- ing of rounded to subrounded dolomite and chert are incor- porated in the dolomite. 43 The heavy mineral suite indicates over 80 percent garnet similar to that in the lower units (Table 3). A slight increase in the number of rounded garnet grains is apparent, however. Zircon grains are generally colorless, small and well-rounded. Well-rounded, brown tourmaline was more common than other varieties. A small quantity of leucoxene and a few rutile grains were present. The contact between Unit VIII and IX is placed at approximately 244 feet on the core. The conglomerate zone at the base of Unit IX which contains very coarse grains and pebbles terminates atthis point, suggesting a possible break in the section. The sandstone of Unit IX is much better rounded and frosted than the underlying unit. The increase in the amounts of zircon and leucoxene plus the more rounded garnet grains also suggest changing conditions. Eli—‘CX Unit Xlapproximately 30 feet thick, is composed primar- ily of gray to brownish gray arenaceous dolomite. A mottled light and dark gray argillaceous sandstone bed occurs near the top and a soft, loosely cemented sandstone bed exists lower in the unit. Some thin interbedded green shaly beds and glauconitic partings are present. 44 The very fine to medium crystalline dolomite exhibits dominately anhedral crystal outlines. It is occasionally limy and slightly vuggy. Quartz grains within the dolomite are fine to coarse, angular to well—rounded. Some secondary overgrowths are apparent on grains lower in the unit. The sands of the upper sandstone bed are fine to coarse with the larger grains being well—rounded and frosted. The smaller grains tend to be more angular. Abundant dark gray, argillaceous material is in the sand and appears’along with dolomite, to be the cementing agent. The lower sandstone bed contains very well-rounded almost spherical, highly frosted sand grains. It is predom- inantly medium grained (figure 7 and 12). Very few angular grains are present. The rock is soft and crumbly. The sand grains appear to be more or less embedded in a grayish clayey material. Garnet,as high as 88 percent, remains the dominant heavy mineral. Slightly rounded to irregular surfaced pink garnets occur in the unit. Zircon, tourmaline and leucoxene comprise about 15 to 25 percent of the heavy minerals (Table 3). Authigenic pyrite, as small irregular grains or clusters. is present and.increases toward the top of the unit. 45 The contact between Unit IX and X was established by the change in color and character of the dolomite and sandstone zone. It has been placed at the 228 foot mark. ME A vertical change in lithology is apparent in Unit XI. This unit is about 80 feet thick. The lower portion of the unit is characterized by a gray to brownish-gray limy dolomite. It is generally fine to medium crystalline, occasionally coarsely crystalline. Anhedral crystal outlines prevail. In some of the coarsely crystalline dolomite, euhedral crystals can be determined. Vugs occur in the dolomite and are often lined with small crystals. Many thin wavy green to black shaly beds and partings occur within the lower zone. Abundant pyrite is concentrated along the partings. The dolomite has fine quartz to silty, angular grains, near the base. Higher up in this zone some floating silt size quartz grains are present. The upper zone of Unit XI contains alternating thin wavy beds of limestone, dolomitic limestone and calcareous shale. The limestone and dolomitic limestone beds are light gray, very fine to medium crystalline and carry fossil fragments. The beds vary in thickness from a 46 fraction of an inch to a foot or more. The calcareous shaly beds are green and contain pyrite. Calcite veinlets occasion- ally occur throughout the zone. Very fine quartz and silt are infrequently incorporated in the limestone. This unit was practically barren of heavy minerals with the exception of abundant pyrite found in all the samples examined (Table 3). From 4 to 30 percent of the heavy mineral were composed of garnet, tourmaline and some leucox- ene in the lower zone of Unit XI. The upper zone and on upward to the top of the core contained only pyrite. The contact between Unit XI and the underlying Unit X is gradational. The contact is placed at 197 feet where there appears to be a sharp decrease in heavy minerals other than pyrite. Also, the dolomite above this point is not sandy, but rather silty; dolomite lying below contains quartz grains which are very fine to coarse, angular to subrounded. Unit XII Primarily limestone, argillaceous limestone, calcareous shales and some limy dolomite hawebeen designated as Unit XII. The unit is 117 feet thick, overlain by 7 feet of glacial drift at the location of the core. 47 The upper 24 feet of this unit is a fine to coarsely crystalline limestone with occasional secondary enlargement of the crystals. Limonite stain is apparent near the top. Fossil fragments and a few floating fine, angular sand grains are incorporated in the limestone. The alternating beds lower in the unit are characterized by very wavy bed- ding surfaces probably indicating near shore shallow water deposition. Near the base of the unit some irregular frag- ments of weathered chert are present. A conglomerate zone composed of round to thin flat pebbles occurs at the base of this unit. The contact between Unit XI and XII was drawn at 117 feet primarily on the basis of the conglomerate zone. 48 STRATIGRAPHIC IMPLICATIONS OF THE CORE One aspect of this study was to present data on the probable correlations of the lithic units of the core with similar units from southern Michigan and the surrounding area. The author realizes the evidence set forth in this report is not entirely conclusive and is subject to revision in the light of more refined studies. The tentative age and correlation of the lithic units are illustrated in Figure 5. Stratigraphic position, lithologic and heavy mineral similarities are used as the basis for determining the correlations as the paleontologic evidence is not included in the study. Unit I, a well-sorted sandstone with a relatively high zircon content, strongly suggesUsthe possibility of being equivalent to the Dresbach formation, Upper Cambrian, as recognized in Wisconsin. It has been identified in wells No. 2, 7, 8, and 10. The median size and sorting coefficient compares with Driscoll's (1956)-studies. Wilgus (1933), Oetking (1951), Driscoll (1956) and Hamblin (1958) report that the Dresbach or the equivalent in Wisconsin and northern Michigan has a relatively higher zircon than garnet content. 49 System Lithic Units Formation or Member Unit XII Trenton m 3 Unit XI Black River '3 a 2 Unit X Glenwood Zone .‘3 3 Unit IX St. Peter > o '8 0 Unit VIII 3 g, Shakopee H 0 “g Unit VII ,3 3; New Richmond .4 . -.-I c: Unit VI a.g Oneota ‘3‘ 6 _. 3 47.1 . :1 Unit V m Jordan 0) C. 76' S g Unit IV 3““ Lodi .13 s g 3 Unit III 3 0 St. Lawrence E B m m U I: a Unit II Franconia D Unit I Dresbach Figure 5 Tentative Age and Correlation of the Core. 50 The base of the core is characterized by angular fragments of quartzite and iron formation which is included in the Dresbach of this report. Core from below this conglomerate zone was not available for study: therefore, it is not known at this time whether the Dresbach overlies the older Cambrian sandstones or the Precambrian at this location. In southern Michigan it is reported as overlying the Eau Claire sandstone and as overlying a conglomerate exposed along the shore of Lake Superior in the Northern Peninsula. Oetking (1951) applies the term Dresbach to the lower sandstone of the Munising group. Driscoll (1956) and Hamblin (1958) refer to the Chapel Rock member as the lower sandstone of the Munising formation. Thwaites (1943) has referred to 75 feet of sandstone in Menominee County as Dresbach. The Dresbach formation is well defined in Wisconsin and has been recognized in the stratigraphy of southern Michigan. Therefore, the term is applied to the lower sandstone of the Munising sandstones. A generally sandy, poorly-sorted sandstone becoming glauconitic and dolomitic towards the top, designated as Unit II, appears to be equivalent to the Franconia formation 51 of the Upper Cambrian of Wisconsin. The Franconia has been distinguished from outcrop samples of Alger County and from wells No. 2, 7, 8, and 10. Pentland (1931), Oetking (1951), Driscoll (1956) and Hamblin (1958) indicate from heavy mineral studies that the Franconia or equivalent in Wisconsin and northern Michigan has a high garnet content which.increa&fistowards the top of the section. This feature is apparent in the heavy mineral suites of Unit II. Miner's Castle member is applied to the upper sandstone of the Munising formation by Driscoll (1956) and Hamblin (1958). Oetking (1951) uses the name Franconia for the upper sandstone of the Munising sandstone group. Thwaites (1943) stated ". . . The original Munising sandstone is the Franconia of Wisconsin." As the Franconia sandstone has been established in southern Michigan and is well defined in Wisconsin, the term is retained in this report and includes the upper sandstone of the Munising sandstones. Therefore, the Franconia over- lies the Dresbach at this location. The Trempealeau formation of Wisconsin includes a basal conglomerate and greensand, the St. Lawrence dolomite, the 52 Lodi (siltstone), the Jordan sandstone, in ascending order. Defined as such the Trempealeau formation overlies the Franconia and includes the remaining beds of the Upper Cambrian. Units III, IV and V of this report are regarded as St. Lawrence, Lodi and Jordan, respectively, of the Trempealeau formation, thereby, assigning them to the Upper Cambrian. The Trempealeau formation has been identified from wells No. 2, 4, 7, 8, 10 and from outcrop samples of Alger County. Study of heavy mineral suites of the Trempealeau, by Ockerman (1930) and Raasch (1935), indicate that there is a high dominance of garnet, especially in the Jordan member, where the mineral generally runs above eighty percent of the suite. They reported the remaining percentage as vari- ously apportioned among zircon, tourmaline and the titanium minerals. Similar high garnet dominance in the Lodi and the St. Lawrence may contain up to 25 percent zircon. Results comparable to the above-mentioned studies were found in Unit III, IV, and V. The Trempealeau has been recognized in the Northern Peninsula of Michigan by the Michigan Geological Survey and represents a complete Upper Cambrian classification compatible with that of the Southern Peninsula. 53 Heretofore, Grabau (1906), Oetking (1951) and Hamblin (1958) have applied the name Au Train to the rocks overlying the Munising sandstones in the Northern Peninsula and assigned them to the Lower Middle Ordovician. Assigned as such, an erroneous age is implied, and the term should be redefined or discontinued. In southern Michigan and Wisconsin, the Prairie du Chien group is composed of the Oneota dolomite, the New Richmond sandstone, and the Shakopee dolomite members. The Prairie du Chien is recognized in wells No. 2, 4, and 7 and core 1 and 3 in addition to the core under study. Unit VI, VII and VIII are assigned Oneota dolomite, New Richmond sandstone and Shakopee dolomite, respectively. The stratigraphic position of the Prairie du Chien group is between the Trempealeau and St. Peter sandstone at the location of the core. Lithologies of the three units are comparable to descriptions of the Prairie du Chien in other areas. Heavy mineral suites indicate a high garnet content with the addition of a small combined percentage of hornblende, epidote and kyanite in Unit VI. Thiel (1935) reported the New Richmond (Unit VII) contains up to 75 percent garnet in composite samples. Pentland (1932) has shown that 54 samples from the Prairie du Chien contain garnet, zircon and tourmaline with kyanite, hornblende and epidote occasionally occurring in relatively high amounts. A mineralogical study of insoluble residues of the Prairie du Chien by Powers (1935) indicates a close relationship of mineral assemblages in the three members which includes garnet, tourmaline, zircon, rutile, hornblende among others. The Prairie du Chien represents the Lower Ordovician in this area. As noted earlier, the Hermansville formation has been applied to rocks overlying the Cambrian sandstone in the Menominee district and various ages implied by the earlier investigators. Thwaites (1943) was under the impression that the Hermansville included both the Trempealeau and Prairie du Chien. As presented in this report the same strata are apparently equivalent to the Prairie du Chien, therefore, the term Hermansville, being poorly defined and without a definite type section, should be discontinued. Unit IX, sandstone and sandy dolomite, represents the St. Peter sandstone. It has been recognized in wells No. l, 2, 5, 8 and core 3. 55 The median size and sorting coefficient of Unit IX compare favorably to that of Thiel (1935) and Tyler (1936). According to Thiel (1935) the upper beds of the St. Peter in the Upper Mississippi Valley contain abundant garnet similar to the Glenwood beds which may represent an early phase of Glenwood sedimentation. A high garnet content was indicated from the heavy mineral suites of the St. Peter (Unit IX) and the Glenwood zone (Unit X) of this report. The thin conglomerate zone containing coarse sand and pebbles at the base of the St. Peter (Unit IX) may indicate a break in deposition reflecting the pre-St. Peter, post- Shakopee erosional period. Berkey (1906) indicates a narrow fringe of St. Peter extending across northern Michigan. Horowitz (1961) who studied the distribution of the St. Peter in Michigan concluded that it was present in Delta County. The St. Peter is generally considered as lower Middle Ordovician. The transitional nature and arbitrary contacts of Unit X have led the author to designate this unit the Glenwood zone. As such, the Glenwood zone occupies a position between the underlying St. Peter and the overlying Black River carbonates. 56 The Glenwood zone consists of sandy dolomite and somewhat shaly dolomitic sandstone. The heavy mineral content shows a dominance of garnet other than the increasing abundance of pyrite. As noted earlier, other investigators have indicated a high garnet content in the Glenwood. Thwaites (1943) reports that in the Northern Peninsula a sandstone immediately underlying the Black River dolomite at Limestone Mountain is probably the Glenwood member of the Platteville dolomite. Horowitz (1961) refers to a sandy dolomite in Delta County as Glenwood. The sandy beds within the Glenwood zone may be largely of St. Peter origin as it is well-sorted, with well-rounded and frosted quartz grains. Some workers feel the Glenwood is more closely related to the St. Peter than to the basal Black River in the Mississippi Valley region. For the above reason and those stated earlier, Unit X is referred to as the Glenwood zone of the Middle Ordovician. Unit XI, primarily dolomite grading vertically into interbedded dolomite, limestone and calcareous shales, represents the Black River at this location. The Black River was recognized in all the wells and core samples. 57 The main exposures of the Middle Ordovician Black River and Trenton are found in this area. Hussey (1952) proposes that the Black River is represented by the Bony Falls member along these exposures. Arbitrary contacts with underlying and overlying units havepmecluded further nomenclature refinement for Unit XI than merely Black River. Wavy, alternating beds of limestone, argillaceous lime- stone, calcareous shale and dolomite of Unit XII have been designated as Trenton. The Trenton has been subdivided by Hussey (1952) in this locality into the Chandler Falls, Groos Quarry and Haymeadow Creek members. No attempt was made to subdivide Unit XII in this report as an arbitrary contact was indi- cated with the underlying Black River. The contact was made on the basis of a thin conglomerate zone containing round to thin pebbles at the base of the Trenton. This conglomerate zone is frequently present near the base of the Trenton according to Hussey (1952). However, paleonto- logic dataare usually required to determine the Black River- Trenton contact and the subdivision of the Trenton. Unconsolidated glacial drift overlies the Trenton at the location of the core. 58 GEOLOGIC HISTORY The general consensus is that an unconformity exists between the Precambrian sediments and the Mt. Simon sand- stone. Sediments of continental origin probably are inclu- ded in the basal Mt. Simon sandstone. Hamblin (1958) con- cludes that the Northern Michigan Highland provided a source for Jacobsville sediments and the formation repre- sents continental deposition in an enclosed basin during the time marine sediments of Early and Middle Cambrian age were being deposited in other parts of the continent. He visualized the first advancement of the Paleozoic seas of this area was from the Northwest. Other authors contend that Early Paleozoic seas progressively transgressed over the weathered surface of the land from a south-southwest direction. The degree of weathering reflects mineralogic differences in the later sediments. The Dresbach sandstone possibly indicates deposition in a broad and shallow basin. These quartz sandy sediments are well sorted and mineralogically similar to older sedi- ments suggesting they may be partially second-cycle sands. Later, the rate of deposition decreased allowing the forma- tion of glauconite in the upper sediments of this time and a probable regression of the sea. 59 An unconformity apparently exists, between the Dresbach and overlying Franconia, as a pronounced change in heavy mineral and sorting is recognized. Hamblin (1958) postulated at this time transgressive seas of the Upper Cambrian came from the southwest and the land masses of northeastern Ontario provided a source area, thereby, accounting for the change in the mineralogy. Sedimentation continued at a I relatively slow rate as glauconite occurs throughout the formation. The transition from Franconia into Trempealeau time was relatively quiet as the continued presence of glauconite points to slow deposition. There is little evidence for the support of an unconformity occurring at this time. More than likely, the Trempealeau was deposited rather slowly in moderately shallow to very shallow water. After deposition of the basal greensands the supply of clastic material was limited and the conditions were more favorable for the deposition of dolomite (St. Lawrence). During the Lodi and continuing into Jordan time, clastic material became increasingly abundant and the depositional rate was accelerated. These coarser sands may indicate a regression stage and the last of the Cambrian seas. 60 Chemically stable heavy minerals of the Jordan sandstone are indicative of a remote source area or reworking of a pre-existing sedimentary formation. well-rounded zircon and tourmaline grains point to the possibility of more than one cycle of erosion. As the Ordovician seas transgressed onto the northern flank of the basin, transitional or interfingering beds of the Jordan andemxfi3.developed and account for the Jordan— like sands occurring in the lower Oneota of this report. Therefore, an unconformity between the Cambrian and Ordo- vician is doubtful in this area. Deposition continued throughout the remaining Prairie du Chien as the succeeding formations, the New Richmond sandstone and Shakopee dolomite, are of a transitional nature and closely related mineralo— gically. The sea may have been relatively stable with the amount and type of material being deposited controlled by the topography and character of the rocks of the source region. The controversy whether or not an unconformity is present between the Cambrian and Ordovician systems is pertinent to this problem,and as a matter of interest, some proposals are presented here. Newcombe's (1933) remarks on the history of the Michigan basin are as follows: 61 A period of warping and extensive erosion took place during the interval between Cambrian and Ozarkian (Lower Ordovician) time. In northern Michigan, the Ozarkian sea contained a large quantity of lime and magnesia which was precipitated on the sands then present along low tidal flats. A quantity of oolitic dolomite . . . . Oetking (1951) concluded from studies in northern Michigan that: The gap between the Croixan (Munising group) and the Middle Ordovician strata may represent either a period of non-deposition or a great erosional interval. A later transgression of the sea deposited the "Au Train" of Middle Ordovician (Black River). Kraft (1956) states from studies on the Oneota-Jordan contact zone in Minnesota: The evidence points to the conclusion that the Jordan sandstone grades upward into the Oneota dolomite and that the rocks were probably deposited during a marine transgression that advanced in a northerly direction. According to Hamblin (1958) a considerable unconformity separates the Miner's Castle member of Upper Cambrian age and the overlying Au Train formation, which he considers to be Middle Ordovician, in the Northern Peninsula of Michigan. Other workers in the Mississippi Valley region suggest that the sea in which the Oneota dolomite was deposited may have transgressed over a land surface of Jordan sandstone result- ing in a gradational contact. 62 At the close of Prairie du Chien time and prior to the deposition of the St. Peter sandstone, extensive erosion occurred throughout the Mississippi Valley region. The con- glomeratic zone at the base of the St. Peter of this report may be indicative of such an event. The St. Peter was deposited in a shallow sea encroaching northward over the land surface in this area and is apparently a near shore facieslas the St. Peter has never been reported farther north. The beds overlying the St. Peter, the Glenwood zone, are partly derived from the St. Peter and appear to be transitional between the St. Peter and Black River carbon- ates. The transitional phase may be due to the reworking of the underlying St. Peter or the fluctuating shoreline of a transgressing sea. Trenton-Black River seas transgressed farther north than the previous Canadian or Chazyan seas as evidenced by the Limestone Mountain outlier in the northwestern part of the Northern Peninsula (Houghton County). The Trenton— Black River rocks appear to represent near shore deposits which accumulated under fluctuating conditions in shallow waters as indicated by the wavy bedding and alternation of argillaceous limestone, shales and dolomite. 63 SUMMARY AND CONCLUSIONS A comprehensive lithologic study of a core, drilled at a 45 degree angle in Delta County, Michigan, using petrographic, mineralogic and sedimentary techniques was attempted. Well samples and cores from the Michigan area were studied for comparative purposes. The paleontologic aspect was not undertaken in the study. The core passed through an interval from Middle Ordovician through the Upper Cambrian sediments at this location, thus enabling the investigation of a more com— plete interval of rocks than is known to exist in any single exposed section in Michigan. The author intends the correlations set forth in this report to be applied tentatively and are subject to revision in the event of more advanced studies. The proposed classi- fication (figure 6) of the lithic units of the core tendstx> be in harmony with that of the subsurface rocks in southern Michigan, thereby, simplifying the nomenclature and age relationships of the lower Paleozoic rocks in this region. The tentative correlations were based primarily on the general stratigraphic position, lithologic and heavy mineral similarities. Definite contacts were not placed on some of 64 m 5 _3 Michigan Basin :3 2: $1 CD Northern Peninsula Southern Peninsula Trenton Trenton é IBlack River BlaCk River ,3 Glenwood Glenwood O 2 a St. Peter St. Peter m .H g, 0" .3 8 Shakopee 8 Shakopee > H s ‘3 ‘9 H a a) New Richmond a New Richmond 0 m -H m +1 S -H 'U C.) .C‘. m U c o 8 r0 Oneota 5 Oneota o m .H -H “ H -H m '7 H 3 m m g :3 '0: Jordan 8 8 Jordan (DC H H E"* . m u . m+’Lodi m m Lodi m9 9'5 5a 5;; :40 . a H S . a 54m St L wrence B m t L wrence 5 g Franconia Franconia H :4 :1 g 8 Dresbach Dresbach m U U u ? Eau Claire ? '0 Mount Simon Jacobsville Jacobsville (?) Proposed Correlation of Ordovician and Cambrian Formations of the Michigan Basin. 65 the lithic units as they warrant further study from a paleontological approach. The Dresbach sandstone was in part, separated from pre—existing sediments as it is well—sorted and mineralo- gically similar to older sandstones. By Franconia time the Cambrian seas encroached upon the broad shallow basin from the south as indicated by the definite change in sorting, heavy mineral suites and occurrence of abundant glauconite. Rather slow continuous deposition marked the arrival of Trempealeau sedimentation. Glauconitic sands and dolomite, followed by silty dolomite and finally sand— stone suggest a regressive phase and the last of the Cambrian seas. The Trempealeau sea may have been somewhat restricted and overlap of all the older Cambrian sediments in the Northern Michigan region did not take place. The oncoming transgressive sea of Prairie du Chien time, how- ever, flooded over all of the older sediments in the region. Interfingering or reworking of the older sediments into the basal Prairie du Chien seems apparent. Continued uninterrupted deposition followed, with sandy dolomite sandstone, bringing the Lower Ordovician sedimentation to a close. 66 An extensive erosional period followed, thereby wear- ing away the Prairie du Chien sediments around the northern end of the basin. St. Peter time marked the return of the sea over the area and progressively overlapping conditions existed throughout the Middle Ordovician as Black River— Trenton deposition can be traced farther north. The Paleozoic formations progressively thin out around the northern end of the basin. As a result of these various conditions and events,pre— vious investigators applied poorly defined terms and erroneous ages to the strata. The Hermansville and Au Train formations evolved from the controversy over the age and type sections of the strata overlying the Munising sandstone. Evidence presented in this report suggests the tentative correlation of these beds with the Prairie du Chien and Trempealeau, respectively. Therefore, the writer advocates the suppression of the former terms and suggests the nomenclature and age set forth in this report be applied to the strata represented in the core. 67 BIBLIOGRAPHY Bain, H. F. 1906 Zinc and Lead Deposits of the Upper Mississippi Valley. U.S.G.S. Bull. 284. Berg, R. R. 1954 Franconia Formation of Minnesota and Wisconsin. Geol. Soc. Am. Bull., Vol. 65. Berkey, C. P. 1906 Paleogeography of St. Peter Time. Geol. Soc. Am. Bull., Vol. 17. Bergquist, S. G. 1929 The Occurrence of Glauconite in the Hermansville Formation of Alger County, Michigan. Pap. Mich. Acad. Sci., Arts and Letters, Vol. 12. . 1932 The Cambrian—Ozarkian Contact in Alger County, Michigan. Pap. Mich. Acad. Sci., Arts and Letters, Vol. 22. Calvin, S. 1906 Geology of Winneshiek Co. Iowa Geol. Surv., Vol. 16. Cohee, G. V. 1945a Stratigraphy of Lower Ordovician and Cambrian Rocks in the Mich. Basin. U.S.G.S. Oil and Gas Investigations, Prelim. 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C. 1935 Résumé of St. Peter Stratigraphy. Bull. A.A.P.G., Vol. 19, NO. 8. Ernst, W. G. 1954 The St. Peter Sandstone—Glenwood Con- tact in Minnesota. Amer. Min., Vol. 39, Nos. 11-12. Farkas, S. E. 1954 Upper Cambrian Franconia Formation of Wisconsin. Jour. of Sed. Pet., Vol. 30, No. 3. Fettke, C. R. 1948 Subsurface Trenton and Sub-Trenton Rocks in Ohio, New York, Pennsylvania, and West Virginia. Bull. A.A.P.G., Vol. 32, No. 8. Grabau, A. W. 1906 Types of Sedimentary Overlap. Geol. SOC. Am. B1111. ,‘ V01. 17. Graham, W. A. P. 1933 Petrology of the Cambrian—Ordovician Contact in Minnesota. Jour. of Geol., Vol. 41. Giles, A. W. 1930 The St. Peter and Older Sandstones of Northern Arkansas. Ark. Geol. Surv., Bull., No. 4. Gutstadt, A. M. 1958 Cambrian and Ordovician Stratigraphy and Oil and Gas Possibilities in Indiana. Ind. Geol. Surv. Bull., No. 14. Hamblin, W. K. 1958 The Cambrian Sandstones of Northern Michigan. Mich. Geol. Surv. Pub. 51. Heller, R. L. 1956 Status of the Prairie du Chien Problem. G.S.A. Guidebook Ser.--Fie1d Trip No. 2. 69 Howell, B. G. 1944 Correlation of the Cambrian Formations of North America. G.S.A. Bull., Vol. 55. Horowitz, M. 1961 The St. Peter-Glenwood Problem in Michigan. Unpublished M.S. Thesis, Mich. State Univ. Hussey, R. C. 1936 The Trenton and Black River Rocks of Michigan. Mich. Geol. Surv. Pub. 40. 1952 The Middle and Upper Ordovician Rocks of Michigan. Mich. Geol. Surv. Pub. 46, Geol. Ser. 39. Index of Michigan Geology. 1823-1955 Mich. Geol. Surv. Pub. 50. Inman, O. L. 1952 Measures of Describing the Size Distri- bution of Sediments. Jour. of Sed. Pet., Vol. 22. Kay, G. M. 1935 Ordovician System in the Upper Mississippi Valley. Kan. Geol. Soc. 9th Ann. Field Conf. Guidebook. King, P. B. 1951 The Tectonics of Middle North America. Princeton Univ. Press, New Jersey. Kraft, J. C. 1956 A Petrographic Study of the Oneota— Jordan Contact Zone. G.S.A. Guidebook Serv.-—Field Trip No. 2. Krumbein, W. 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Rept. 74 TABLE 1 LITHOLOGY OF THE CORE Cornell Core, T.40N., R.23W., Section 5, Delta County, Michigan Thickness Thickness Megascopic and Microscopic of Unit to Base of Description Formation (Feet) (Feet) Elevation approx. 800 feet Glacial Drift . . . . . . . . . . . . , 7 7 Unit XII-—Trenton (117.7') Limestone, light gray to greenish near base, fine to coarsely cry- stalline, occasional secondary enlargement, limonite—stained near top, many thin shaly beds and partings near base, few floating fine sand grains, fossiliferous . . 24.8 117.7 Limestone, light to dark gray, very finely crystalline, highly argil— laceous, occasionally silty, wavy bedded, pyrite, fossiliferous, dark gray dolomite bed 1 ft. thick, 20 ft. below top . . . . . . . . . . . 7.1 92.9 Limestone-shale mottled light gray to green, alternating wavy thin beds of limestone and highly cal— careous shale, some beds slightly dolomitic and silty, contains pyrite, fossiliferous . . . . . . . 61.7 85.8 Dolomite, medium gray to dark gray, medium crystalline, occasionally coarsely crystalline, wavy bedded, thin shaly beds and partings, some calcite veinlets, few silt size quartz grains, weathered irregular chert fragments 8 ft. below top, slightly vuggy near base, contains pyrite, thin conglomerate at base, round to thin flat pebbles . . . I 24.1 24.1 Thickness of Unit (Feet) Unit XI--Black River (80.0') Limestone—shale, mottled light gray to green, wavy alternating beds, some beds dolomitic and silty, contains pyrite, fossiliferous, few vugs near base . . . . . . . . . . 15.6 Dolomite, mottled medium gray to green medium crystalline, occa— sional coarsely crystalline, limy, thin wavy shaly beds and partings, few floating silt size quartz grains, contains pyrite . . . . . . 8.5 Dolomite, light and dark gray, fine to medium crystalline, limy, very thin to greenish to black shaly partings, slightly vuggy, some very fine floating sand grains, highly vuggy zone 1 ft. thick, 16 ft. below the top . . . . . . . . . 15.6 Dolomite, light to dark, mottled near base, fine to medium crystal— line, limy, very vuggy near the top, many thin wavy green to black shaly beds and parting containing pyrite and silt size quartz grains. 22.7 Dolomite, gray to brownish gray, medium crystalline, thin green shaly beds, very thin black partings . . . . . . . . . . . . . 6.4 Dolomite, buff to gray, medium to coarsely crystalline, vuggy, very thin black shaly partings . . . . . 2.1 75 Thickness to Base of Formation (Feet) 80.0 64.4 55.9 40.3 17.6 11.2 76 Thickness Thickness of Unit to Base of Formation (Feet) (Feet) Dolomite, gray to brownish gray fine to medium crystalline, thin wavy black shale partings con- taining pyrite and silt size quartz grains . . . . . . . . . . . 4.3 9.1 Dolomite, brownish gray, fine to medium crystalline, vuggy, thin wavy black shaly partings . . . . . 4.8 4.8 Unit X--G1enwood Zone (30.5') Dolomite, gray to brownish gray, very fine to medium crystalline, limy, slightly vuggy, sandy, very fine to coarse, angular to rounded grains . 5.7 30.5 Sandstone, mottled light and dark gray, fine to coarse-grained, argillaceous with some large quartz grains which are rounded and appear frosted . . . . . . . . 1.4 24.8 Dolomite, light gray, very fine to medium crystalline, limy, many thin wavy black shaly partings, sandy, with some coarse rounded grains . . 6.4 23.4 Dolomite, light brownish gray, fine to medium crystalline, thin green glauconitic partings, vuggy, sandy, with rounded, frosted coarse grains, fine angular grains with overgrowths . . . . . . . . . 4.3 17.0 Dolomite, light gray, finely cry— stalline, slightly vuggy, sandy with rounded, frosted, very fine to medium quartz grains . . . . . . 5.6 12.7 Sandstone, gray to brownish gray, medium to coarse grained, friable, argillaceous; most grains are frosted and rounded to well- rounded . Dolomite, to medium crystalline, some thin interbedded green shales, coarse quartz grains appear rounded and frosted, fine to med- ium quartz grains frequently show overgrowths . Unit IX--St. Peter Sandstone, smaller grains, Dolomite, coarse, Conglomerate, Dolomite, shale, pebbles . 4 in. from bottom. large angular frag— ments of gray dolomite in a brown sandy matrix (16.3') light brown, light brown, coarsely crystalline, vuggy near top, very sandy with fine to angular to rounded grains fine to coarse grained, larger quartz grains rounded and frosted, fre- quent overgrowths occur on the some thin inter- bedded very fine grained dolomite fine to light to dark gray, fine sandy, with light brown to grayish, medium to coarsely crystalline with thin interbedded green and black sandstone bed 3 ft. Conglomeratic near bottom, very coarse sand grains and Thickness of Unit (Feet) 2.9 77 Thickness to Base of Formation (Feet) 16.3 13.4 Thickness of Unit (Feet) Unit VIII-—Shakopee (?) (10.3') Sandstone, light brownish gray, medium to coarse grained, highly dolomitic . . . . . . . . . . . . . 2.2 Dolomite, light to medium gray, medium to coarsely crystalline, vuggy, 1 1/2 in. thick interbedded fine brown sand and greenish shale at base . . . . . . . . . . . . . . 2.1 Dolomite, light brown, fine to medium crystalline, very sandy with fine to medium grains, some thin black to green shaly partings . . . 6.0 Unit VII——New Richmond (11.3') Sandstone, light brown to brown, medium grained, angular to few rounded grains, little frosting and numerous overgrowths firmly cemented, very fine grained silty, shaly, gray dolomite zone 1 ft. thick, 3 ft. below top, gray, vuggy crystalline dolomite 1 ft. thick 5 ft. above base, very fine grained buff secondary dolomite masses near base . . . . . . . . . . . . . . . 11.3 Unit VI--Oneota (78.0') Dolomite, light gray, very fine to finely crystalline, few vugs, slightly limy, sandy with fine to coarse grains, few thin sandy, ‘ shaly beds and partings with pyrite and glauconite . . . . . . . 2.1 Dolomite, mottled brown and gray, fine to medium crystalline, vuggy, sandy with fine to medium sub- angular grains . . . . . . . . . . 8.5 78 Thickness to Base of Formation (Feet) 10.3 11.3 78.0 75.9 79 Thickness Thickness of Unit to Base of Formation (Feet) (Feet) Dolomite, light gray, fine to medium crystalline, with thin brown sandy beds and greenish to black shaly beds . . . . . . . . . 2.9 67.4 Dolomite, mottled buff to dark gray, medium crystalline, small vugs, floating fine angular quartz grains . . . . . . . . . . . . . . 4.2 64.5 Dolomite, mottled buff to gray, medium grained, some large vugs, few floating fine angular sand grains . . . . . . . . . . . . . . 7.1 60.3 Dolomite, medium gray to brownish, very finely crystalline, sandy, with 1 1/2 ft. sandy,shaly zone 2 ft. below top, fine sandy zone near base . . . . . . . . . . . . . 7.8 53.2 Dolomite, light brown to buff, very finely crystalline, dense with very thin fine grained sandy beds . 14.2 45.4 Dolomite, brown, medium to coarsely crystalline, vuggy, few floating fine sand grains . . . . . . . . . 1.4 31.2 Dolomite, light brown to grayish, fine to medium grained, thin green shaly partings, some iron stained seams near top, 1 ft. sandstone zone 5 ft. below top, 3 ft. of sandstone, medium to coarse grained, 3 ft. from base . . . . . 10.7 29.8 Sandstone and sandy dolomite, brown to grayish brown, medium to coarsely crystalline, some oolitic dolomite, thin green to black glauconitic shaly partings Dolomite, buff to brownish, fine to medium crystalline, oolitic, sandy thin green glauconitic partings . Sandstone, brownish gray, medium to coarse grained, dolomitic, some chert and thin glauconitic shaly partings . . . . . . . . . . . . . Dolomite, light grayish to buff, fine to medium crystalline, oolitic with fine quartz grains, glauconite and chert, thin green shaly beds at base . . . . . . . . . . . . . . Unit V-—Jordan (19.2') Sandstone, light brown to grayish, medium to coarse grained, dolomi— tic, some glauconite . . . . . . . Dolomite, light brown, fine to medium crystalline, very sandy with fine to medium angular to rounded quartz grains, some thin glauconi— tic shaly partings . . . . . . . . Dolomite, brownish gray, fine to medium crystalline, vuggy, coarse grained sandy zone near top, 1 ft. of fine to coarse sand at base, few thin black shaly partings . . Thickness of Unit (Feet) 6.4 80 Thickness to Base of Formation (Feet) 19.2 15.6 Thickness of Unit (Feet) Unit IV-—Lodi (73.71) Dolomite, light brown to buff, very fine to medium crystalline, some small scattered vugs, silty, with fine quartz grains, some glauco— nite near top . . . . . . . . . . . 19.8 Dolomite, mottled buff to gray, very fine to finely crystalline, thin buff silty beds and partings, con— tains pyrite with iron oxide staining along bedding surface . . 24.1 Dolomite, mottled buff to gray, very fine to medium crystalline, numerous buff silty beds and part— ings containing glauconite, pyrite with iron oxide staining along bedding surface . . . . . . . . . . 7.1 Dolomite, buff to gray, very fine to medium crystalline, some buff silty, sandy dolomite with iron staining along bedding surfaces near top and base, thin glauconi- tic black shaly partings . . . . . 7.1 Dolomite, medium gray, medium cry- stalline, occasionally coarsely crystalline, some iron staining along bedding, thin glauconitic black shaly partings . . . . . . . 15.6 Unit III-—St. Lawrence (49.0') Dolomite, gray to pink, medium cry— stalline, vuggy near base, some thin buff silty beds, thin black partings, some iron staining, containing pyrite and glauconite. . 17.1 81 Thickness to Base of Formation (Feet) 73.7 53.9 29.8 22.7 15.6 49.0 Dolomite, pink to gray, medium crystalline, dense vuggy, frequent iron staining along fractures and parting, contains pyrite and glauconite . . . . . . . . . . Dolomite, pink to gray, medium to coarsely crystalline, vuggy, highly iron stained thin black partings, contains pyrite and glauconite. . . Shale, dolomitic, gray to black, pyrite bands and nodules. . Dolomite, dark gray, finely crystal— line, silty, abundant pyrite. . . . Dolomite, gray to dark gray, fine to medium crystalline, sandy, vuggy, some iron staining, glau— conitic, pyrite . . . . . . . . . . Sandstone, dark gray to brownish green, very fine to medium grained, few rounded grains, many angular grains, showing undergrowths, dolomitic, thin interbedded shale and glauconite, abundant pyrite and glauconite . . . . . . . . . . Sandstone, gray to greenish brown, very fine to medium grained, angu— lar grains showing frequent over- growths, dolomitic, thin inter- bedded green shales and sandy dolomite, abundant glauconite, pyrite, 1 ft. thick conglomerate zone at base containing angular to subround fragments of dolomite and sandy dolomite . . . . . . . . 82 Thickness Thickness of Unit to Base of Formation (Feet) (Feet) 7 0 31.9 9.3 24.9 2.1 15.6 2.8 13.5 1.4 10.7 5.7 9.3 3.6 3 6 Unit II--Franconia (28.8') Dolomite, gray to dark gray, medium crystalline, slightly vuggy, sandy, contains pyrite and glauconite . . . . . . . . Sandstone, gray to brownish gray, fine to coarse grained, angular to well rounded grains frosted and pitted, some overgrowths on smaller grains, interbedded sandy dolomite, abundant glauconite and pyrite . . . . . . . . . . . . . . Dolomite, light gray, medium crystal— line, some small vugs, sandy, conglomerate band 2 in. thick with angular fragments at base, pyrite and glauconite present . . . . . Sandstone, brownish gray, fine to coarse grained, some frosted rounded grains interbedded sandy dolomite, some vugs and limonite staining, intraformational conglom- erate band 1 in. thick near base, contains glauconite . . . . . . . . Sandstone, light brown to brown, fine to coarse grained, subangular to well rounded, frosted grains, smaller grains showing overgrowths Somewhat dolomitic thin green glauconitic shaly beds and partings, possible worm burrows.. . 83 Thickness Thickness of Unit to Base of Formation (Feet) (Feet) 4 2 28.8 6.4 24.6 1.4 19.2 7 8 17 8 10.0 10.0 Unit I--Dresbach (46.8 plus) Sandstone, light brown to white, fine to coarse grained, subangular to rounded grains, occasionally many thin green shaly partings, glauco- nitic, possible worm burrows par— frosted, somewhat dolomitic, tially filled with green clay . Sandstone, light brown to white, fine to coarse grained, subangular to rounded slightly frosted quartz grains, possible worm burrows par- tially filled with green clay, thin speckled limonite staining, green glauconite and partings . Sandstone, grayish brown, fine to coarse grained, angular to rounded grains with occasional frosting and overgrowths, thin green glau— conitic shaly partings, possible worm burrows partially filled with green clay, white to reddish— purple angular to rounded quartzite pebbles 3 ft. below the top Sandstone, grayish brown to pink, fine to coarse grained, occasional smal- frosting on rounded grains, ler grains showing overgrowths, thin green glauconitic shaly part- ings, scattered white, green to reddish quartzite pebbles . S ome Thickness of Unit (Feet) 13.4 84 Thickness to Base of Formation (Feet) 46.8 25.6 19.2 85 Thickness Thickness of Unit to Base of Formation (Feet) (Feet) Sandstone, brownish pink, fine to coarse grained, angular to rounded grains, occasional frosting on larger grains, scattered white to reddish quartzite pebbles, glauconite present in thin partings, con- glomeratic zone, angular white, green to reddish—purple quartzite fragments and green soapstone about 3 ft. thick at the base . . . 10.7 10.7 Bottom of core available for study 86 TABLE 2 DEPTH CONVERSION IN FEET TVD MD TVD MD 0 0 310 437.1 10 14.1 320 451.2 20 28.2 330 465.3 30 42.3 340 479.4 40 56.4 350 493.5 50 70.5 360 507.6 60 84.6 370 521.7 70 98.7 380 535.8 80 112.8 390 549.9 90 126.9 400 564.0 100 141.0 410 578.1 110 155.1 420 592.2 120 169.2 430 606.3 130 183.3 440 620.4 140 197.4 450 634.5 150 211.5 460 648.6 160 225.6 470 662.7 170 239.7 480 676.8 180 253.8 490 690.9 190 267.9 500 705.0 200 282.0 510 719.1 210 296.1 520 733.2 220 310.2 530 747.3 230 324.3 540 761.4 240 338.4 550 775.5 250 352.5 560 789.6 260 366.6 570 803.7 270 380.7 580 817.8 280 394.8 590 831.9 290 408.9 600 846.0 300 423.0 True vertical depth Measured depth TVD Black River Unit XI Unit X Glenwood Unit X Unit IX Peter St. Unit IX Unit VI Unit VI Garnet Shakopee 160 170 180 190 200 210 220 230 240 II II 250 Zircon TABLE 3 Percent by Number 10 20 3O 40 50 6O 7O 80 90 100 l 1 1 l t L 1 1 l _J - Pyrite - _ — Pyrite - ‘ I — P rite - /4 Y /E . [Ill .\.2\ \ x} !{Llu fl Z Tourmaline Leucoxene Others HEAVY MINERALS OF THE CORE New Richmond Unit VII Unit VII Unit VI Oneota Unit VI Unit V Jordan 300 Percent by Number 0 10 20 30 40 50 60 70 80 90 100 l l 1— I I I l I I 260 F . // 280 [/1 290 310 320 330 4 // - ///- TABLE 3 HEAVY MINERALS--Continued 1 LT Lodi Jordan St. Lawrence Unit V Unit Unit Unit III IV IV 360 370 380 10 l 20 1 Percent by Number 40 l 30 1 50 l 60 7O 1 4 - f 80 90 100 L l _J V// / ’ :1 390 //:2;;/rr— - Pyrite - 400 "- Pyrite & Iron Oxides- 410 Pyrite & Iron Oxides - 420 I Pyrite & Iron Oxides - 430 Pyrite & Iron Oxides - 440 Pyrite & Iron Oxides - /. 450 ' Pyrite & Iron Oxides - TABLE 3 HEAVY MINERALS--Continued Percent by Number 0 10 20 30 40 50 60 70 80 90 100 l I l l l 1 I l I l l 460 (D U £1 0 E 470 (U a 45 U) 480 Unit III Unit II / 49° _ ///I (O -H C —4 8 500 " C. :1 {U H m Unit II 510 Unit I 520 530 fi 540 (U .Q U) (D 23 550 560 Base of Core TABLE 3 HEAVY MINERALS--Continued 91 CmHHQEMUOHm 6.0m how ZQN me 0H ll UMOHHHmm CHwnvaBrHUHOZIOmVMUHQU .m. mmszozmz emume .um come 6mm 3m 244 he emmm Albedo meumgmemucmnsmx em> .6 seszomz “meme .um omsm mmm see 20m 6 emomm Hinges . .ume .UOmma .umz..m zazmqmmq meee>mcmsnmm men ome gem me Ha u: mueonnse u woem .o .o .v «same cmHHQEmo emm nmm mm Zme em :1 Hams nememe emenmmz .m «sommHmo emeHQEmo ommm mmm 24H m» m mmmmm seameoo Heo .m mmmo nmeme .um mnem mew 3m 2mm me mmomm HuBUOEmmHoz : .emm .oonm< .umz .H szsze m an e e m . m a pesnme e co Hmuoe coHpm>mHm COHDMUOA mmHmEMm HHUB mmqm2OUuo UHGUHE I :mflHQEmo HmmmD "mqu< mmqmzmo pmmuoaooeom .m ememoqoomom .um CH am m>OQm aofluomm HmQESC Show I Houmuwmo on um 2m sumac ummm ce m a coeumooq easemm season Hopes coflum>mam . . mmamsmm Hamz UODGHDGOUIIWMQm2B .UCON Uoo3cmHO .m>MDO mocmskum m>HDMHSESO h wnsmHm mumquHHHHE CH HUUUEMHQ H H0.0 H.O w W O.H _ . . \\\ _ . . _ . _ . _ . . _ . _ . . _ . 3.0 Mm _ " mmé om _ H 3.0 62 _ \ _ _ . . _ \ X\ OH O O O V M N 0 Ln Aouanbax; qurem peietnmno O O (\ KO 0 CD om OOH 94 pmmm mmm Q>B .mCoumoCmm Hmumm .pm .m>CCU >UCmame m>HHMHCECO m musmHm mumumEHHHHE CH HmmemHQ . H m m So 70 o o o 04 . _ _ 1 . _ . \\\. _ . . V _ _ _\ _ _ _ _ _ _ _ _ . \ _ _ 8.0 mm . _ SA om _ _ \ 3.0 oz .. _ \ _ _ _ _\ .\\K O O c> o C) O O b m K) v «I m H Aouenbax; qqfirem peqetnmng O (O OO OOH 95 H0.0 .ummm mem o>e .meounncmm cannon mCmDmEHHHHE CH HmumEMHQ H.O .w>HCU moCvamHm m>HDMHCECU Ho 0 wusmHm --PO m.O Ov.H Nv.O Mm Om US . u\ \ ‘ OH O O c> O O O m q' m N Kouenbex; qurem penetnmng O [\ O CO OOH 96 .uwmm Now Q>B .mCoumOCmm MHCOUCmum .w>HCO >UCmamum m>HUMHCECU OH mnsmHm mumumEHHHHE CH HmumEMHQ H0.0 H.O HO NO O.H . . \L _ _ _ _ _ _ mad mm _ mm.H Om " g _ \ _ _ r\ V\\ OH ON Om Ow Om 00 Oh Aouenbax; qqfitem peieTnan Ow om OOH 97 ummm mmm Q>B .wCoumpCmm Comnmmum .m>HCO moCngwum m>HUMHCECU HH wHCmHm mnmumEHHHHE CH HmuwSMHQ H0.0 H.O JO m0 mm O.H g . _., _ _ _ _ . . _ . _\ _ _ _\ _ _ N . _ _ . _ \ No.0 Cm _ _ Om.H Om _ _ 3.0 02 . \\ OH O O O O O O In 0 m m KouanbaI; qurem peqetnmna O [x 0 CD OO OOH 98 40% 404’ 30— 30~ 20- 203 10- 10« 0 0. 1 1/2 1/4 1/8 1/16 mm 1 1/2 1/4 1/8 1/16 mm Unit IX. Glenwood Zone Unit VIII. St. Peter SS TVD 225 Feet TVD 283 Feet 40 I" 4073 30 - 304 20" 20~ 10 - 104 0 0 1 1/2 1/4 1/8 1/16 mm 1 1/2 1/4 1/8 1/16 mm Unit V. Jordan Sandstone Unit II. Franconia SS TVD 345 Feet TVD 492 Feet % % 40 - 40. 30 I 301 20 n 20~ 10 j 104 0 0 1 1/2 1/4 1/8 1/16 mm 1 1/2 1/4 1/8 1/16 mm Unit II. Franconia SS Unit II. Franconia SS TVD 500 Feet TVD 510 Feet Figure 12 Grain-Size Distribution of the Sandstones in the Core. 96 40 1 30 . 20 - 10 - 0 1 1/2 1/4 1/8 1/16 mm Unit I. Dresbach Sandstone TVD 520 Feet 40 fi 30 . 20 ' 10 . 0 1 1/2 1/4 1/8 1/16 mm Unit I. Dresbach Sandstone TVD 540 Feet 40 /1 30 ‘ 20 ‘ 10 0 1 1/2 1/4 1/8 1/16 mm Unit I. Dresbach Sandstone TVD 560 Feet Figure 13 40 30 20 10 40 30 20 10 99 96 1/4 1/8 DreSbach Sandstone TVD 528 Feet 1 1/2 1/16 mm Unit I. 96 1 1/2 1/4 1/8 Dresbach Sandstone TVD 551 Feet 1/16 mm Unit I. Grain-Size Distribution of the Sandstones in the Core. HICHIGRN STATE UNIV. LIBRQRIES ll "ll 9 312 3105751212