ABSTRACT
The Late Cambrian Jordan Sandstone is subdivided into four members in southeastern Minnesota. Younging upward these are the Norwalk, Van Oser, Waukon and Sunset Point
Members. The very fine-grained feldspathic Norwalk and
Waukon Members are interpreted as offshore to lower shoreface lithofacies. The medium-grained quartzose Van
Oser Member is interpreted as a middle and upper shoreface lithofacies influenced by episodic sedimentation. The fine-grained feldspathic and dolomitic Sunset Point Member is interpreted as a tide-influenced shallow marine lithofacies; sedimentation was transitional from siliciclastic shoreface deposition to locally shoaling- upward carbonate deposition most probably associated with a laterally prograding offshore platform or development of laterally accreting and migrating tidal islands.
Deposition of the Jordan Sandstone occurred in an epicontinental shallow marine environment during a transition from marine regression, typified by Norwalk,
Van Oser and Waukon strata, to constant subsidence coupled with progradation of carbonate sediments, typified by
Sunset Point strata. Progradation of Sunset Point strata resulted from locally increasing rates of carbonate sedimentation. The provenance area of the Jordan Sandstone was the continental craton interior. Diagenetic Processes occurred under low temperatures and pressures. The paragenetic sequence in order of occurrence is: the precipitation of thin quartz syntaxial overgrowths and potassium feldspar expitaxial overgrowths, the precipitation of hematite, dolomitization, the dissolution of potassium feldspar and dolomite, the precipitation of calcite, the dissolution of calcite and a second precipitation of hematite. Lithostratigraphic units (i.e., members) of the Jordan Sandstone in Minnesota demonstrate conformable relationships and have diachronous lower and upper boundaries; the Cambrian-Ordovician boundary is diachronous and typically gradational in southeastern Minnesota. Sunset Point strata represent a viable member of the Jordan Sandstone and are best not included in the overlying Ordovician Oneota Dolomite as some workers have suggested.
II ACKNQWT.EPGEMENTS Preparation of this thesis has greatly benefited from the assistance, advice and co-operation of many individuals. Above all, I gratefully acknowledge my thesis supervisor, Dr. Richard W. Ojakangas, of the University of Minnesota- Duluth who proposed this study, edited several drafts of the text and provided valuable suggestions for its improvement. Dr. Glenn B. Morey of the Minnesota Geological Survey was an enthusiastic supporter of the study and suggested to Dr. Ojakangas that it would be an excellent thesis topic. Drs. David G. Darby and Curtis Anderson of the University of Minnesota-Duluth and Dr. Glenn B. Morey of the Minnesota Geological Survey served as members of the thesis committee; they made helpful suggestions and critically reviewed the manuscript. To Brian Hayden goes my special thanks for his companionship and discussions in the field. I also thank Jodie Holmgren for typing drafts of the thesis. Partial funding of this study was provided by the Geology Department of the University of Minnesota-Duluth and the Minnesota Geological Survey. Finally, it is a pleasure to express my gratitude to my parents, Mr. and Mrs. Joseph W. Thomas, and my wife, Helen Earnshaw, for their constant encouragement.
iii TABLE OF CONTENTS
ABSTRACT •.•• ...... i ACKNOWLEDGEMENTS ...... iii TABLE OF CONTENTS iv
FIGURES vii
TABLES •• x PLATES x
Chapter I INTRODUCTION • • • . . • . • . • • • . . • . . . 1 Pt1R.POSE . • • • • • • • • • • • • . • • • • . . 1 METHODS OF STUDY • • • . . . • • • . 1 Field Work • . • • • • . . • • 1 Laboratory Work • • • • . • • • • 2 PREVIOUS WORK • . • . • • • . • • . • . • • 4 History of Stratigraphic Nomenclature 4 Sedimentological Studies . . . • . • . . . 10
Chapter II LITHOSTRATIGRAPHY • . • . • . . • . . . • 11 JORDAN SANDSTONE • . . . . . • . • • . • . 11 NORWALK MEM.BER • • • • • • • • • • • 17 Physical Sedimentary Structures 18 Biogenic Sedimentary Structures 21 St. Lawrence - Norwalk Contact • • 23 VAN OSER MEMBER • • • • • • • • • • • • • • • • 26 Physical Sedimentary Structures . . • 26 Biogenic Sedimentary Structures • . . . . 31 Norwalk - Van Oser Contact • . • • 33 WAUKON MEMBER • • • • • • . • • • . . . 34 SUNSET POINT CCOON VALLEY) MEMBER ••••. 34 Physical Sedimentary Structures • . . 37 Biogenic Sedimentary Structures • • • 38 Van Oser - Sunset Point Contact . . • . . 40 Sunset Point - Oneota Formation Contact 42 Chapter III PALEONTOLOGY . • . • • . • • . . • . 43 MACROFOSSILS . . . . . 43 MICROFOSSILS ...... 44 Chapter IV PALEOCURRENTS ...... 47
iv Chapter V PE'rR.OLOGY' • • • • • • • • • • • • 56 OPERATIONAL DEFINITIONS . . . • • . • • • • • . 57 NORWALK MEMBER . . . • • • • • 58 Mineralogy . . . • . • . . 58 Texture ...... 63 VAN OSER MEMBER • . • • . • • • • 67 Mineralogy ...... • • . • . • . • 67 Texture . • • • . . • 77 WAUKON MEMBER. • • • • • • • • • • • • • • • 78 SUNSET POINT (COON VALLEY) MEMBER ...... 18 Mineralogy • • . . 78 Texture ...... 90 HEAVY MINERALS . . . • . • • 93 Chapter VI DIAGENESIS • . . • • 95 MINERALOGY 95 Cementation Sequence • 102 TEX.TORE • • • • • • • • • 104 Primary Porosity • 108 Secondary Porosity • • 108 Chapter VII INTERPRETATION AND DISCUSSION • • • . • . . 113 ENVIRONMENTS OF DEPOSITION • • • • • . • • • . 11·3 Norwalk Member ...... • 119 Van Oser Member . . • 128 Waukon Member . • . . . • • . • . . • • . 133 Sunset Point (Coon Valley) Member ••.• 135 PROVEN'ANCE • • • • • • • • • • • • • • . • . • 144 DIAGENETIC HISTORY • • . • . . 151 Dolomitization . • . • •• 157 TECTONIC SETTING AND CYCLICITY 159 CAMBRO - ORDOVICIAN BOUNDARY • . • • . • . 161 Chapter VIII CONCLUSIONS 167 REFERENCES CITED •• 171
v APPENDICES APPENDIX 1: Index Map of Minnesota Counties . . . . •. . . . 186 APPENDIX 2: Measured Section Location Descriptions ...... APPENDIX 3: Measured Section Descriptions and Thin Section Sample Locations ...... 189 APPENDIX t.. : Paleocurrent Data 202 APPENDIX 5: Monocrystalline Quartz Extinction Data . . . . 204
vi FIGURES
Figure
1. Location map of the 12 measured sections of Jordan Sandstone used in this study • ...... • . • • • • • 3 2. History of stratigraphic nomenclature • . • • . 5 3. Stratigraphic column of Upper Cambrian rocks in Minnesota • . . ' . . . . • • • • . 12 '-. Structural contour map of the top of the Jordan Sandstone in Minnesota • . . . 13 5. Isopach map of the Jordan Sandstone in Minnesota • ...... 15 6. Lithostratigraphy of Jordan Sandstone in Minnesota • . • . . . . • • . . • . 16 7. Stratification geometry terminology • • • • 19 8. Bedding thickness terminology • . . • . • • . . 20 9. Typical exposure of dolomitic siltstones of the St. Lawrence Formation • • . . . • 25 10. Typical exposure of mottled sandstones of the Norwalk Member • . • • . • 25 11. Typical exposure of trough cross- stratif ication in the Van Oser Member . . • . . • . . . . • . • . . 28 12. Unconunonly thick cosets of tabular cross-stratification in the Van Oser Member . • • . • . . • . . . . . 28 13. Continuous and discontinuous planar parallel stratification in the Van Oser Member . . . . • . • 30 l/a. Flat-pebble rip-up clast horizon in the Van Oser Member • • . . . • • • • • . 30 15. Arencolites as it typically occurs in the Van Oser Member . . • . • • 32 16 .. Skolithos as it typically occurs in the Van Oser Member • . . • . • • • 32 17. Schematic cross-section of the Jordan Sandstone from northeastern Iowa to central Wisconsin . . . • • • • • . • . 36 18. Laterally linked hemispheroid stromatolites in the Sunset Point (Coon Valley) Member •••.•••..•. 39 19. Green muds and silts interstratified with fine sands in the Sunset Point (Coon Valley) Member .•..•• 39 20. Planolites in the Sunset Point (Coon Valley) Member ••••••.•• . . . 41 21. Planolites in the Sunset Point (Coon Valley) Member • • . . • . • • • • • • 41
vii 22. Paleocurrent rose diagrams for the Van Oser Member of the Jordan Sandstone in Minnesota . . • • • • • • • • 48 23. Paleocurrent rose diagrams for the Norwalk Member of the Jordan Sandstone in Minnesota • . • • 49 2t.i.. Paleocurrent rose diagrams for the Sunset Point (Coon Valley) Member of the Jordan Sandstone in Minnesota . • • 50 25. Paleocurrent rose diagrams summarizing all measurements taken in the Norwalk, Van Oser, and Sunset Point (Coon Valley) Members of the Jordan Sandstone in Minnesota 51 26. Paleocurrent rose diagrams summarizing all measurements taken in the Jordan Sandstone in Minnesota 52 27. Detrital composition of Norwalk Member samples . • • • . . . • • • • • . • 62 28. Photomicrograph of a typical Norwalk Member specimen • . . . • . . . • . • 64 29. Types of framework grain contacts • . • . • • . 66 30. Detrital composition of Van Oser Member samples . . • • . • • . . • . • • • 68 31. Photomicrograph of a typical Van Oser Member specimen . . • • . . . . • . . • • 75 32. Detrital composition of Sunset Point (Coon Valley) Member samples ... 82 33. Photomicrograph of a typical dolomitic wackestone in Sunset Point (Coon Valley) Member ..••...... 83 3i.. Photomicrograph of a typical arkose in Sunset Point (Coon Valley) Member •..• 84 35. Photomicrograph of a typical crystalline dolomite in Sunset Point (Coon Valley) Member • • • . • • • • • • • • 85 36. Photomicrograph of an oolitic packstone in Sunset Point (Coon Valley) Member . 86 37.• Photomicrograph of oolite aggregates in a Sunset Point (Coon Valley) Member specimen • • . • • • • . • . . . . 91 38. Photomicrograph of a well rounded green tourmaline grain, Van Oser Member 94 39. Photomicrograph of a rounded etched garnet grain, Van Oser Member 94 I L..O. Photomicrograph of authigenic epitaxial \ potassium feldspar overgrowths on \ detrital feldspar cores, Norwalk Member • • • • • • . • . • • • • • 98 L..1. Photomicrograph of complete cementation by quartz, Van Oser Member •••••• 98
viii (6, 2 • Photomicrograph of syntaxial quartz overgrowths, Van Oser Member •..•••. 100 (6, 3 • Photomicrograph of iron-oxide cementation, Van Oser Member . . • . . . . . • 101 Exposure of liesegang banding in Van Oser Member . . . . . • . • . . • • • 101 (6, 5. Generalized paragenetic sequence in the Jordan Sandstone . • • . • • • • • • • • • 103 Photomicrograph of calcite cement replacing quartz grain in Van Oser Member . . . 105 Photomicrograph of porosity enhancement by dissolution of potassium feldspar in Norwalk Member • • • . • . • . . . • . 110 48. Photomicrograph of porosity enhancement by dissolution of dolomite in Van Oser Member . . • . • • . . • . . . . 110 Photomicrograph of secondary porosity reduction by late calcite cementation in Sunset Point (Coon Valley) Member ••..••....• 111 50. Size-velocity diagram for common elastic sedimentary bedf orms • . • • . • 122 51. Block diagrams illustrating hurranocky cross-stratification and swash cross-stratification • • • . . . . 125 52. Shoreline profile and terminology of sandy mainland coasts • . • 129 53. Tidal island facies model • . • . 139 5'6. Examples of sediment mixing processes on siliciclastic-influenced carbonate platfoxms ...... 141 55. Shallowing-upward sequences produced by progradation of a tidal flat wedge 143 56. Tectonic setting of Jordan Sandstone source area as distinguished using modal detrital data • • • . • • • • . • • 145 57. Photomicrograph of a multicycle quartz grain in Sunset Point (Coon Valley) Member • • • . . • • • • • . . • • 146 58. The Hollandale Embayment of the Ancestral Forest City Basin .•.••.••••.• 150 59. Summary of the main characteristics of secondary porosity models • . • . . . . . 156 60. Generalized stratigraphic column for southeastern Minnesota showing interpreted transgressions and regressions ...... 162
ix TABLES
Table 1. Paleocurrent data from Jordan Sandstone in south-central and western Wisconsin . • . • • . 55 2. Norwalk Member modal analysis data 60 3. Van Oser Member modal analysis data • • • • . . 69 fa.. Waukon Member modal analysis data • . • • • 79 5. Sunset Point (Coon Valley) Member modal analysis data • . • . • • . . • . . 87
PLATES
Plate 1. Southeast-northwest stratigraphic cross-section of the Jordan Sandstone • • • • • • • • • . Cin pocket) 2. Southeast-northwest stratigraphic cross-section of the Jordan Sandstone, alternative interpretation • . . . • • (in pocket)
x Chapter I INTRODUCTION PURPQSE Although the upper Mississippi River Valley is regarded as the type and reference area in North America for Upper Cambrian Series sedimentary rocks (Berg and others 1956), a recent comprehensive sedimentological of one Upper Cambrian formation, the Jordan Sandstone, had not been accomplished for its occurrences in Minnesota. Therefore, this study was undertaken. The purpose of this study is threefold: (1) to describe the lithostratigraphy, petrology, diagenesis, paleocurrents and paleontology of the Jordan Sandstone in Minnesota; (2) to better interpret the environments of deposition, provenance and tectonic setting; and (3) to re- examine the nature of the Cambrian-Ordovician boundary in Minnesota and to determine the validity of the present subdivision of the Jordan Sandstone into three members. METHODS OF STUDY Field of Work Field work for this study was completed during the months of June, July and August in 1986. Thirty significant exposures of the Jordan Sandstone were examined in southeastern Minnesota and the eight most complete and regionally representative sections were selected for detailed study. Each section was measured and described at
1 a scale of 1:12 and paleocurrent data were collected. A total of 358 lithological samples and 252 photographs were taken for reference and further study. The Minnesota Geological Survey provided to the author four unpublished measured section descriptions of the Jordan Sandstone. A map of measured locations described in this study is presented in Figure 1 and an index map of Minnesota counties is illustrated in Appendix 1. Township and Range co- ordinates and road mileages for each measured section are listed in Appendix 2. All measured sections are accessible by automobile. Laboratory Work In the laboratory, a total of 112 petrographic thin sections were examined to determine textural, mineralogical and diagenetic characteristics. A modal analysis was determined for 107 of the thin sections. For each modal analysis, the mineralogy was analyzed at 60 equally-spaced points on 10 random parallel traverses perpendicular to bedding (600 points). Fifteen heavy mineral mounts were also prepared and examined. Eighteen samples were disaggregated and examined for conodont microfossils. All
358 lithologic samples obtained in the field were examined in the laboratory with emphasis on trace fossil Cichnofossil) identification and on improving estimates of grain-size taken in the field.
2 2 0 0 km
Scale
t N
... 0
•••
Figure 1. Location map of the 12 measured sections of Jordan Sandstone used in this study. Refer to Appendix 1 and Appendix 2 for location descriptions.
3 PREVIOUS WORK History of Stratigraphic Nomenclature Owen (1852) provided the first description of rocks now comprising the Jordan Sandstone. No formal name was introduced for these rocks until Winchell (1874) proposed that the fine-grained sandstone exposed at the town of Jordan, Scott County, Minnesota, and the overlying coarser grained sandstone exposed in Van Oser's Creek near Jordan, be named the Jordan Sandstone (Figure 2). In 1875, R.D. Irving proposed the name Madison Sandstone for similar rocks near Madison, Wisconsin. Winchell (1886) correlated the Jordan Sandstone with the Madison Sandstone. Ulrich (1911) objected to Winchell's correlation and, in the first of numerous nomenclature revisions based predominantly on paleontology, Ulrich (see Walcott, 1914) restricted the Jordan Sandstone to only the coarser grained sandstone described by Winchell (1874). Ulrich assigned the finer grained sandstone to the underlying St. Lawrence Formation and proposed that the Madison Sandstone overlay the Jordan Sandstone. Twenhofel and Thwaites (1919) used the 1914 nomenclature of Ulrich but Thwaites (1923) suggested new nomenclature revisions. Thwaites proposed, on the basis of faunal characteristics, that the St. Lawrence Formation be assigned the name Trempealeau Formation, and that the fine-
4 .....l'lj IJQc Ii (1) .N
rt ::i:: ( ..... 0 tll rt Winchell Irving Ulrich Twenhofel Thwaites Ulrich Stauffer 'O 0 OJ Ii (1874) (1875) (19f4) & Thwaites ( 1923) ( 1924) ( 1925) OQ '< (I) (1919) tll 0 . Hl tll MADISON MADISON MADISON rt FM FM FM Ii Ill .....rt OQ JORDAN MADISON MADISON JORDAN JORDAN 01 Ii Ill SANDSTONE SANDSTONE JORDAN JORDAN FM SANDSTONE SANDSTONE 'O SANDSTONE SANDSTONE ::r'..... 0 ::1 NORWALK NORWALK 0 MBA MBR :J :E :E (1) LL. LL. ::1 0 ST. ST. ::::> ::::> ...... <( Pl <( ST. LAWRENCE LAWRENCE UJ UJ ST. rt ...J ...J s:: <( Ii LAWRENCE MENDOTA FM FM <( LAWRENCE (1) UJ UJ . LIMESTONE LIMESTONE a. a. FM UJ UJ CJ) a: a: CD ._ ._ MADISON MADISON MADISON MADISON MADISON FM FM MBR MBR FM JORDAN JORDAN u. VAN C1> SANDSTONE FM JORDAN JORDAN JORDAN JORDAN z OSER MBR MBR MBR MBR c:( MB.R :i! :i! :i! :i! 0 u. u. u. u. a: 0 NORWALK NORWALK ::> ::> ::> ::> , MBR c:( c:( c:( c:( MBR :? w w w w u...... I ...I ...I c:( c:( c:( c:( :i! w w w w u. ::> a. a. a. a. c:( ::ii! tu w ST. w w w 0 ...I a: a: w c:( .,_a: .,_ .,_ a: z UJ LAWRENCE .,_ UJ a. FM a: w c:( a: ...I .,_ ..,: U> -- Raasch Nelson Ostrom Austin Odom This ( 1951) (1956) (1967) (1972) & Ostrom Study (1978) SUNSET SUNSET SUNSET w SUNSET) COON SUNSET POINT FM POINT FM w POINT MBA z POINT . VALLEY z POINT MBR 0 UJ (SUNSET t- lL lL UJ 0 POINT 0 VAN OSER z VAN OSER z VAN OSER z ct z VAN OSER ct "' JORDAN JORDAN ct MBR UJ MBR ct 0 0 UJ MBR MBR FM a: a: z WAUKON z lL 0 ct 0 ct .., 0 .., 0 :::> a: a: ct NORWALK 0 NORWALK NORWALK 0 UJ MBR .., .., NORWALK ..J MBR MBR MBA ct w ..J a. lL lL ::!: lL lL lL UJ UJ w UJ w w a: u u u u t- z z z uz z UJ UJ UJ UJ UJ a: a: a: a: a: ..J ..J ..J ..J ..J ._: en en en en en grained sandstones described by Winchell (1874) be included as the youngest member of the Trempealeau Formation. Thwaites proposed the name Norwalk for the fine-grained sandstones and he assigned the calcareous sandstones that overlay the Trempealeau Formation to the Madison Sandstone. Ulrich (1924) agreed with Thwaites but assigned the coarser grained sandstones to the Jordan Sandstone, which was overlain by the Madison Sandstone and underlain by the Norwalk Member of the Trempealeau Formation. Stauffer (1925) proposed a return to the nomenclature of Winchell (1874) because the fauna thought to be characteristic of the Trempealeau Formation had also been identified above the fine-grained Norwalk in the coarser grained sandstone. Stauffer also suggested that the medium- to coarse-grained sandstone above the Norwalk strata be named Van Oser but no formal subdivision of the Jordan into members was proposed. Ulrich and Resser (1930, 1933) continued to use the nomenclature proposed by Ulrich (1924) but Trowbridge and Atwater retained Stauffer's (1925) nomenclature which assigned the Norwalk strata to the Jordan Sandstone. Wanenacher and others (1934) included the Jordan Sandstone in the Trempealeau Formation and Twenhofel and others (1935) included both the Jordan Sandstone and the overlying Madison Sandstone in an expanded Trempealeau Formation. Bridge 8 (1937) used the nomenclature of Twenhofel and others (1935) but Raasch (1939) returned the Madison Sandstone to formation status. Stauffer and others (1939) returned the Jordan Sandstone to formation status and formally defined two members, the Norwalk and the Van Oser. Although much of the paleontological knowledge of Upper Cambrian fauna in Minnesota culminated in the Wisconsin- Minnesota column of the National Research Council correlation chart for the Cambrian (Howell and others additional changes to the stratigraphic nomenclature of the Jordan Sandstone were forthcoming. To avoid possible confusion with the Mississippian Madison Limestone of Montana and Wyoming, Raasch (1951) proposed that the Madison Sandstone be renamed the Sunset Point after a bluff in Madison, Wisconsin. Raasch also assigned the Jordan strata to the Trempealeau Formation. One year later, the Cambrian- Ordovician boundary was placed by Raasch (1952) at the contact between the Sunset Point Formation and the dolomite of the overlying Oneota Formation. Nelson (1956) returned the Jordan to formation status but did not recognize individual members. The Jordan Sandstone has remained a formation since 1956 but the nomenclature of its members has been revised. Ostrom (1967) proposed three members for Jordan strata: the Norwalk, the Van Oser, and the Sunset Point. Austin 9 (1972) agreed with the three-member subdivision of Jordan strata. However, Odom and Ostrom (1978) suggested that the Sunset Point Member is restricted to the region near Madison, Wisconsin, and is a lens interstratified with the Van Oser Member. They proposed that the sandy dolomite overlying the Van Oser was a fourth member of the Jordan strata. The name Coon Valley, from the town of Coon Valley, Wisconsin, was proposed for the fourth member. Odom and Ostrom (1978) also proposed the name Waukon for a fifth member of Jordan strata locally present in northeast Iowa and southwest Wisconsin. Sedi,mentological Studies Most early studies of the Jordan Sandstone were predominantly associated with biostratigraphic characteristics of the formation. The first significant sedimentological studies of Jordan strata were by Ockerman (1930), Ahlen (1952), Boardman (1952) and Kraft (1952). Subsequent sedimentological studies associated with the Jordan Sandstone include those by Melby (1967), Wegrzyn (1973), Michelson and Dott (1973), Adams (1975), Odom (1975), Byers (1978), Dott (1978), Odom and Ostrom (1978), Porter (1978), and Kapchinske (1980). These subsequent studies are associated almost exclusively with exposures of the Jordan Sandstone in Wisconsin. 10 Chapter II LITHOSTRATIGRAPHY JORDAN SANDSTONE The Jordan Sandstone is Late Cambrian in age and is the youngest f orrnation of the Trempealeauan Stage in the Croixan Series (Figure 3). The Jordan Sandstone crops out in southeastern Minnesota, west-central Wisconsin and northeastern Iowa. It is also present in the subsurface of Wisconsin (Ostrom 1966), as well as central Iowa and northwestern Illinois (Kapchinske 1980). In Minnesota, outcrops of Jordan strata are located predominantly in the Mississippi and St. Croix River valleys but some exposures are also present in the Minnesota River Valley. The Jordan Sandstone also occurs in the subsurface of the Twin Cities Basin (Mossler 1972). The structural attitude of the Jordan Sandstone is approximately horizontal. A structural contour map of the present attitude of the top of the Jordan Sandstone in Minnesota (Figure shows Jordan strata dipping approximately degree to the southwest near the Mississippi River and degree to the southeast near the Minnesota River. Mossler (1983) provided the most recent compilation of Jordan Sandstone structural attitude data for Minnesota. According to Austin (1972) the Jordan Sandstone has an average thickness in Minnesota of approximately 26 m. 11 Generalized Stratigraphy Glacial Drill Forma101 OUATERNARY '",0- D o:OJI DE: VO NIAN -·' ... ._,,., I • l, •" I• : • • • · • •I e:ml11T1es1one •• 1. ,I J .l • I I ./. / l I I I I 1 I l I I I I l l ILATIEVILLI Cll.tWWOOO ORDOVICIAN 11 ,.,... :\':.'.·:::...... •• ! t•o•.••••• 7 . J- i / -I /..... I 'I 1-1 I I I I I I I CHRONOST RAT IGRAPHT I I I -/ • , f I I .t System Series Stage 7 7 I I I ;;;;. I T L I ,- z Pou"'._"'°', .' I ; ,,,,,,,. er :::>- \Ion Our er z f "' M1mbtr ...Jg Norwa lk f T -J er., Member , f 'T W'"' I ' '• 9 ::E: ':: i .c Member '09•' o E w- Sloca Eorih er Member I- . z z .9 z er cl IS .. , ·.· •• •• ••J\'.":. cl z J x 0 0 - u Totf'laf'\ Mtft'lt* CAMBRIAN a: 0 z /Bor kmoH m a: er Member 0 er Ironton Sondston1 cl (.) i-= Golnwill1 Sondstont z ·s..a, .,..,,1 .. "' er ::c ------""$1\olr .,.._,,· u H ...... -.. er CD .. ... tlCJ•VCI!' (/) w urut -'' 1 er c Mt Simon Sondstone Precambrian Figure 3. column of Upper Cambrian rocks in Minnesota. (After Ojakangas and Matsch 1982 and Austin 1972). 12 INDEX MAP 0 50KM SCALE Nr Figure Structural contour map of the top of the Jordan Sandstone in Minnesota. (Modified from Messler 1983). Contour interval is 100 feet. Geographic extent of Jordan Sandstone outlined by shaded area. 13 Austin noted that the Jordan section decreases in thickness from the Mississippi River valley west to the Minnesota River Valley. An isopach map of the Jordan Sandstone in Minnesota (Figure 5) shows subsurface thicknesses ranging from typically 15 m near the towns of Mankato and Austin to approximately 31 m near Winona and Minneapolis - St. Paul. In this study, the maximum thickness of Jordan strata, observed in Wabasha County (Location D, Figure 1) was at least m. On the basis of lithic characteristics, the Jordan Sandstone is divided into three members in Minnesota (Austin 1972). Younging upward these members are the Norwalk, Van Oser and Sunset Point. Odom and Ostrom (1978) concluded that the Sunset Point Member in Minnesota is the equivalent of a fourth member of the Jordan Sandstone in Wisconsin, the Coon Valley Member. A fifth member of the Jordan Sandstone, the Waukon (Figure 6), has been identified in southwestern Wisconsin and northeastern Iowa (Odom and Ostrom 1978, Porter 1978). The Jordan Sandstone is underlain by dolomitic siltstones of the St. Lawrence Formation and is overlain by dolomites of the Oneota Formation (Lower Ordovician). Discussion and interpretation of the following lithostratigraphic descriptions are in Chapter VII. 14 ..DEX MAP 0 SOKM SCALE f N Figure 5. Isopach map of the Jordan Sandstone in Minnesota. (Modified from Mossler 1983). Contour interval is 50 feet. Geographic extent of Jordan Sandstone outlined by shaded area. 15 CHRONOSTRATIGRAPHY TEXTURE & (/) w MEMBER Ct MINERALOGY w (/) w z z < z z ::> CJ) < < c < >< w z -a: 0- -' co a: < en< () w :E • c.. z 1- < < U) w c () a: a: I- 0..., :.•. =·-:,. ·. FINE- TO COARSE-GRAINED QUARTZ VERY ANE- TO FINE-GRAINED ARKOSES & SUBARKOSES VERY FINE- TO MEDIUM-GRAINED POORLY SORTED SUBARKOSES, WACKESTONES, OOLITIC PACKSTONES & SANDY CRYSTALLINE DOLOMITES Figure 6. Lithostratigraphy of Jordan Sandstone in Minnesota. 16 NORWALK MJ!MBER. The Norwalk Member is the basal lithic unit of the Jordan Sandstone. The thickness of this member in southeastern Minnesota typically ranges from a maximum of 11 m in the Mississippi River Valley near the Iowa border to thicknesses less than 6 m in the St. Croix River Valley. The Norwalk Member was not observed by the author in outcrops west of the Mississippi or St. Croix River valleys but other workers in Minnesota (Stauffer and Thiel Mossler 1972) identified Norwalk strata in outcrops of Scott County and in the subsurface of Anoka County. In southeastern Minnesota the Norwalk Member is typically composed of feldspathic sandstone and the majority of exposures are moderately dolomitic. The detailed mineralogical composition is described in Chapter V. The mean grain-size of Norwalk Member rocks ranges from silt to fine sand but very fine-grained rocks predominate. A coarsening-upward trend in grain-size occurs in some locations but a fining-upward trend was observed at one locality. Grain-size changes are presented in the schematic measured sections in Appendix 3. Induration of the Norwalk Member is typically poor; the rocks are commonly very friable. 17 Physical Sedimentary Structures In the following descriptions of stratification, geometry and thickness are defined according to the terminology of Collinson and Thompson (1982, pg. 13) (Figure 7) and Ingram (Figure 8), respectively. Stratification thicknesses of the Norwalk Member in southeastern Minnesota range from very thickly-bedded to thinly-laminated but medium- to thickly-bedded stratification predominates. A generalization of vertical changes in stratification thicknesses is not possible but in three measured sections (Sections A,C, and Din Appendix 3) stratification thickness increased upward. Lateral correlation between measured sections is not possible. Discontinuous and continuous planar parallel bedding geometry predominates in the Norwalk Member. Discontinuous and continuous wavy parallel bedding geometry is abundant near the base of the Norwalk Member in at least one locality (Section A). Planar parallel lamination is present in every section of Norwalk strata studied but is not abundant at any location. There is no preferential vertical position for lamination in Norwalk strata. Cross-stratification occurs in the majority of Norwalk Member exposures studied. Most cross-stratification is typically located in the upper 3 m of Norwalk strata and trough cross-stratification in sets 10 to 20 cm thick 18 Parallel £ !======! planar. parallel drscontinuous. planar. parallel ------wavy, parallel discon1inuous. wavy, parallel '- "O., - __,, ..> (.)= .._- ---- curved. parallel · d1scon11nuous. curveo-- . parallel- Non-parallel - planar. non-p11rallel drsconunuous . planar. non-parallel ------wavy, non-par;illel drsconunuous. wavy,-- non-parallel-- - - curved, non·paraHel d1scont1nuous--. curved,-- non-parallel Figure 7. Stratification geometry terminology. (From Collinson and Thompson 1982, p. 13). 19 VERY THICKLY BEDDED ____ Thicker than 1 m THICKLY BEDDED -- ______30 - 100 cm MEDIUM BEDDED ------1 0 - 30 cm THINLY BEDDED------3 - 10cm VERY THINLY BEDDED _ _ _ _ _ 1 - 3 cm THICKLY LAMINATED ______0.3 - 1 cm THINLY LAMINATED ------Thinner than 0.3 cm Figure 8. Bedding thickness terminology. (From Ingram 195t.). 20 predominates. Maximum trough cross-stratification set thickness is typically 30 cm. Tabular cross-stratification occurs in sets ranging from to 25 cm, but 10 to 15 cm thick sets are more common. Both angular planar foresets and tangential foresets occur. Isolated cross-stratified sets occur in greater abundance than cross-stratified cosets. Foresets of cross-stratified sets are typically laminations appr,oxirnately 1 rrun thick. Low-angle (less than 10 degrees dip) cross- stratification occurs in two measured sections of Norwalk strata (Sections Hand I). According to Harms and others (1975) there are two types of low-angle cross- stratification: (1) swash cross-stratification and (2) hurranocky cross-stratification. The low-angle cross- stratification at one location (Section H) has been identified as hummocky cross-stratification. Symmetrical ripple marks occur at one locality of Norwalk strata (Section H) and flat-pebble rip-up clasts occur at four locations (Sections A, B, H, I). Green silt and mud partings less than 1 mm thick occur at random within the fine- and very fine-grained sandstones of the Norwalk Member. Biogenic Sedimentary Structures The Norwalk Member contains two groups of biogenic sedimentary structures: (1) trace fossils {ichnofossils) 21 and (2) bioturbate textures. Three types of trace fossils were observed in Norwalk strata: (1) Arencolites, (2) Skolithos, and (3) Planolites. Two bioturbate textures were observed in Norwalk strata: (1) mottled bedding, and (2) homogeneous (massive) bedding. Homogeneous (massive) bedding may be produced by processes other than bioturbation but such processes are unlikely for Norwalk strata (refer to Chapter VII). Arencolites is the most abundant trace fossil observed in Norwalk Strata. It is identified by Frey and Pemberton as a simple vertical U-shaped tube preserved in three dimensions and contained totally within the sediment. In the Norwalk Member it is usually recognized as a gently curving inclined tube with an oval or circular cross-section typically 2 mm in diameter. As noted by Porter (1978) these tubes are commonly filled with a dolomite and sand mixture that is stained with iron-oxide to a darker color than the host sands. Skolithus is a simple tube commonly oriented perpendicular to bedding (Pemberton and Frey Skolithus is preserved in three dimensions and is contained totally within the sediment. In the Norwalk Member it has oval or circular cross-sections typically 2 to mm in diameter and is stained with iron-oxide to a darker color than the host sands. 22 \ Planolites trace fossils are sand-filled burrows preserved on the bases of sandstone beds or as impressions of these burrows in very thin shale layers within sandstones (Martinsson 1970). In the Norwalk Member, Planolites trace fossils are horizontal to slightly oblique burrows that typically curve in an irregular pattern. Cross-section diameters are typically 3 to 6 mm and continuous burrow segments ranges from less than 1 cm to 9 cm long. Many burrows intersect or cross over other burrows. Arencolites, Skolithos and Planolites are illustrated in the following descriptions of the Van Oser and Sunset Point (Coon Valley) Members, as they are better preserved in those members. Mottled and homogeneous bedding are the most abundant features of Norwalk strata attributed to a biogenic origin. Mottling occurs as irregular-shaped patches of darker colored sediments within lighter colored sediments or lighter colored sediments within darker colored sediments. Homogeneous bedding occurs in Norwalk strata as zones of sediment up to 2.5 m thick devoid or nearly devoid of sedimentary structures. If structures do occur they are typically truncated irregularly by homogeneous sediment. St. Lawrence - Norwalk Contact In Wisconsin, previous workers (Ostrom 1966, Wegrzyn 1973, and Porter 1978) reported that the nature of the 23 contact between the Norwalk Member of the Jordan Sandstone and the underlying St. Lawrence Formation varies depending on location. Ostrom (1966) noted that the contact at some locations in Wisconsin is sharp or erosional. Wegrzyn (1973) reported that the contact is transitional at localities he studied and Porter (1978) observed only one location where the contact is erosional; typically the contact was transitional. Typical exposures of the dolomitic siltstones characteristic of the uppermost St. Lawrence Formation and of the mottled very fine-grained sandstones characteristic of the Norwalk Member are illustrated in Figures 9 and 10. The St. Lawrence - Norwalk contact is defined by upward changes in grain-size and bedding style (Porter 1978). Grain-size typically changes from silt in the underlying Lodi Member of the St. Lawrence Formation to very fine sand in the Norwalk Member. Bedding style typically changes from very thin to thin, wavy and nodular dolomitic beds in the Lodi Member to thin to medium, less dolomitic planar, trough-shaped or mottled beds of the Norwalk Member. In Minnesota, the St. Lawrence - Norwalk contact is only exposed at four of the localities studied (Sections A, H, I and J). The contact was not of an erosional nature at any of these localities; typically grain-size increased from 24 Figure 9. Typical exposure of dolomitic siltstones of the St. Lawrence Formation (Section A). Jacob's staff is divided into 1 foot intervals. Figure 10. Typical exposure of mottled sandstones of the Norwalk Member (Section E). Jacob's staff is divided into 1 foot intervals. 25 silt to fine-grained sand over a transitional zone of 0.5 to 1 m. The contact is conformable. VAN OSER MEMBER The Van Oser Member is the middle lithic unit of the Jordan Sandstone. The maximum thickness of Van Oser strata measured in this study is 26 m (Section E). Typical thicknesses of this member in southeastern Minnesota range from 12 to 18 m. The Van Oser Member was observed by the author in all measured sections studied. No lateral trend in thickness was identified. In southeastern Minnesota the Van Oser Member is typically composed of quartzose sandstone and some exposures are moderately calcareous. The detailed mineralogical composition is described in Chapter V. The mean grain-size of Van Oser Member rocks ranges from very fine to coarse sand but medium-grained rocks predominate. Coarsening- or fining-upward trends in grain- size do not occur at the locations studied. Grain-size changes are presented in the schematic measured sections in Appendix 3. Induration of the Van Oser Member ranges from very poor to good but poorly indurated rocks predominate. Physical Sedimentary Structures Stratification thicknesses of the Van Oser Member in southeastern Minnesota range from very thickly-bedded to 26 thinly-laminated but thin- to medium-bedded stratification predominates. A generalization of vertical changes in stratification thicknesses is not possible. Lateral correlations between measured sections cannot be made. Curved, non-parallel bedding, typical of trough cross- stratification (Figure 11), is the predominant bedding geometry in the Van Oser Member. Trough cross- stratification is ubiquitous in the Van Oser strata studied. Trough thicknesses range from less than 10 cm to a maximum of 60 cm. Trough cross-stratified cosets are typically 0.5 to 1.5 m thick but can occur in thicknesses up to 6 m. Tabular cross-stratification is present at the majority of locations studied but is, with one exception (Section A), much less abundant than trough cross-stratification. Tabular cross-stratified sets are typically less than 30 cm thick but can occur in thickness up to 1.2 m. Unlike trough cross-stratification, tabular cross-stratified sets typically occur in isolation but relatively thick cosets (Figure 11) occur at one location (Section A). Herringbone cross-stratification, confirmed by bipolar paleocurrent measurements, occurs at two locations (Sections A and B) and apparent herringbone cross-stratification (paleocurrent measurements not possible) occurs at two additional locations of Van Oser strata (Sections G and K). Low-angle cross-stratification occurs at three locations (Sections B, 27 Figure 11. Typical exposure of trough cross-stratification in the Van Oser Member (Section G). Hanwer is cm long. Figure 12. Uncommonly thick cosets of tabular cross- stratification in the Van Oser Member (Section A). Jacob's staff is divided into 1 foot intervals. 28 E, and H). Generalizations about abundance or types of cross-stratification occurring at specific stratigraphic horizons cannot be made in the Van Oser Member. Continuous and some discontinuous planar parallel bedding and lamination (Figure 13) occur in almost every measured section of Van Oser strata. Thinly laminated planar parallel bedding commonly separates cosets of trough cross-stratification or sets of tabular cross- stratification. Flat-pebble rip-up clasts (Figure are, with one exception (Section G), ubiquitous in the Van Oser Member. The clasts are typically composed of very fine-grained to fine-grained sand and most are smaller than 1 by 3 cm in size. Clast orientations are typically subparallel to bedding in planar parallel beds or subparallel to foresets in cross-stratification. Planar parallel beds containing flat-pebble rip-ups may have erosional lower bounding surfaces. Asymmetrical ripple marks occur in one locality of Van Oser strata (Section E) and asymmetrical ripples, exposed only in cross-section, occur in one additional location (Section D). Green silt and mud partings and very thin beds rarely occur in the Van Oser Member. 29 Figure 13. Continuous and discontinuous planar parallel stratification in the Van Oser Member (Section C). Note typically poor induration. Jacob's staff is divided into 1 foot intervals. Figure Flat-pebble rip-up clast horizon in the Van Oser Member (Section A). Note erosional lower bounding surface. Tape measure units are inches. 30 Biogenic Sedimentary Structures The Van Oser Member contains two groups of biogenic sedimentary structures: (1) trace fossils and (2) bioturbate textures. All three types of trace fossils, occurring as described for the Norwalk Member, are also observed in Van Oser strata: (1) Arencolites (Figure 15), (2) Skolitbos 31 Figure 15. Arencolites as it typically occurs in the Van Oser Member (Section A, sample DT-20). Coin diameter is 2 cm. Sample displays cross-section of bed, arrows to top. r-T"""T"""ll"I> Figure 16. Skolithos as it typically occurs in the Van Oser Member (cross-section view, Section B). Tape measure units are inches. 32 Norwalk - Van Oser Contact Previous workers {Ostrom 1965, Wegrzyn 1973, Porter 1978) described the Norwalk - Van Oser contact in Wisconsin. Ostrom (1965) defined the contact as the change from fine- grained, thin- to medium-bedded sandstone, to a medium- to coarse-grained massive sandstone. Wegrzyn (1973) noted that the contact was either sharp or gradational over an interval of several feet. Porter (1978) suggested that the primary criterion to define the contact should be the first occurrence of narrow, deep, high-angle trough cross-bedding because cross-bedding is more easily recognized than subtle grain-size changes. The nature of the contact, where defined by the occurrence of the narrow, deep, high-angle trough cross-bedding, is typically sharp and may have erosional relief. However, by defining the contact in this way, medium-grained strata may be included in the Norwalk Member and very fine-grained strata may be included in the Van Oser Member. In this study, the criteria used to define the Norwalk - Van Oser contact are those suggested by Porter (1978); grain-size is the primary criterion only in the absence of high-angle trough cross-bedding (Section A). At the majority of measured sections in this study, the first occurrence of high-angle trough cross-bedding is also coincident with an increase in grain-size to fine- or more typically, medium-grained strata. Norwalk - Van Oser contacts. in southeastern Minnesota are typically sharp or erosional. A transitional contact occurs at only one locality studied (Section A). WAUKON MEMBER Odom and Ostrom (1978) suggested the name Waukon for the very fine-grained, feldspathic, moderately dolomitic, massive to thinly bedded, bioturbated sandstone that occurs locally, in southwestern Wisconsin and northeastern Iowa, within the Van Oser Member. Porter (1978) suggested that the very fine-grained strata within the Van Oser Member exhibit essentially the same characteristics as Norwalk strata. Porter proposed that interstratification of the Norwalk and Van Oser Members is a more appropriate explanation than the occurrence of a separate, locally present lithic member within Van Oser strata. In this study, very fine-grained strata with characteristics similar to those of the Norwalk Member occur within the Van Oser Member at least two localities (Sections A and D). At each locality the very fine-grained strata are approximately rn thick and occur 7 m above the base of the Van Oser Member. Upper and lower contacts are abrupt. SUNSET POINT (COON VALLEY) MEMBER The upper lithic unit of the Jordan Sandstone is the Sunset Point Member (Austin 1972). Odom and Ostrom (1978) 34 concluded that the type section of Sunset Point strata near Madison, Wisconsin, is a lens of highly feldspathic, very fine-grained sandstone interstratif ied with the Van Oser Member (Figure 17). They also concluded that the unit named Sunset Point in southwestern Wisconsin, northeastern Iowa and southeastern Minnesota is lithologically distinct from the type Sunset Point section. They proposed the Sunset Point Member in these three regions should be re-named Coon Valley after a type section chosen near the town of Coon Valley, Wisconsin. The thickness of the Sunset Point (Coon Valley) Member in southeastern Minnesota typically ranges from a maximum of 9 m in the Mississippi River Valley, near the Iowa border, to thicknesses of approximately 1 m in the St. Croix River Valley. The Sunset Point (Coon Valley) Member was not observed by the author in outcrops west of the Mississippi or St. Croix River valleys. In southeastern Minnesota, the Sunset Point (Coon Valley) Member is typically a heterogeneous lithic unit with a composition ranging from quartzose or feldspathic sandstone to sandy or oolitic dolomite. Detailed mineralogical compositions are described in Chapter V. The mean grain-size of Sunset Point (Coon Valley) strata ranges from very fine to coarse sand but fine-grained strata predominate. A fining-upwards trend in grain-size 35 c ::. Cl) Cl) Cl)... 00 ra (!) > C') --...Cl) ...- c. c: c.. Q) 9t: .!:1 ::>c: I I I z 0 0: 0 u.. algal f z mounds 3mlL-_...... _____. 40 Km Figure 17. Schematic cross-section of the Jordan Sandstone from northeastern Iowa to central Wisconsin. (From Odom and Ostrom 1978). 36 occurs at three localities (Sections A, D, and E). Grain- size changes are presented in the schematic measured sections in Appendix 3. Induration in the Sunset Point (Coon Valley) Member is typically good but poorly indurated horizons may· occur. Generally, Sunset Point (Coon Valley) strata are better indurated than the underlying Van Oser and Norwalk strata because of the presence of more carbonate cement. Physical Sedimentary Structures Stratification thicknesses of the Sunset Point (Coon Valley) Member in southeastern Minnesota range from very thickly-bedded to thinly-laminated but no specific thicknesses predominate. A generalization of vertical changes in stratification thickness is not possible, but at three localities (Sections B, C, and D) stratification thicknesses increased upward. Lateral correlation between measured sections is not possible. A wide variety of bedding geometry occurs in the Sunset Point (Coon Valley) Member and, unlike the Norwalk and Van Oser Members, no one or two types of bedding geometry predominate. The diversity of bedding geometries reflects the heterogeneous nature of this member; strata are continuously to discontinuously planar parallel bedded, planar parallel laminated, trough cross-stratified, and tabular cross-stratified. There is no preferential vertical 37 position for any of these bedding types. Typically, cross- stratification is much less abundant than in the underlying Van Oser Member and set thicknesses are thinner in Sunset Point (Coon Valley) strata. Apparent herringbone stratification (paleocurrent measurements not obtained due to two-dimensional exposure) occurs at two localities (Sections Band D). Other physical features of Sunset Point (Coon Valley) strata include the occurrence at one locality (Section A) of laterally linked hemispheroid stromatolites (Figure 18). The stromatolites are typically less than 20 cm in height and are associated with oolite beds. Oolite beds occur at one additional location (Section E). Flat-pebble rip-up clasts occur at 5 locations (Sections B, C, D, H, and K). The clasts occur subparallel to stratification or foreset laminae. Very thinly-bedded to thinly laminated green silt and mud horizons may be interstratified with very fine- and fine-grained sands (Figure 19) but silt and mud partings less than 1 mm thick are more typical. R_iogenic Sedimentary Structures The Sunset Point (Coon Valley) Member contains both trace fossils and bioturbate textures. As observed in Norwalk and Van Oser strata, Arencolites, Skolithos and Planolites are the trace fossil genera that occur in Sunset Point (Coon Valley) strata. In general, biogenic 38 Figure 18. Laterally linked hemispheroid stromatolites in the Sunset Point (Coon Valley) Member Ccross- section view, Section A). Coin diameter is 2.5 cm. Figure 19. Green muds and silts interstratified with fine sands in the Sunset Point (Coon Valley) Member (Section B). Tape measure units are inches. 39 sedimentary structures are much more abundant in the Sunset Point (Coon Valley) Member than in the underlying Van Oser Member and moderately more abundant than in the Norwalk Member. Planolites (Figures 20 and 21) is more abundant in Sunset Point (Coon Valley) strata than in the other members of the Jordan Sandstone. Homogeneous (massive) bedding is the predominate bioturbate texture in Sunset Point (Coon Valley) strata but mottled bedding also occurs. Homogeneous bedding occurs most frequently in the upper portions of the member. Van Oser - Sunset Point (Coon Valley) Contact In Wisconsin, recent studies (Odom and Ostrom 1978, Kapchinske 1980) described the Van Oser - Coon Valley contact as the first occurrence of dolomitic sandstones or sandy dolostones, typically containing poorly sorted sand and intraclasts. In this study, the Van Oser - Sunset Point (Coon Valley) contact as it occurs in Minnesota, may be difficult to recognize in the field (Sections E and A). However, the significant dolomite increase associated with the contact can commonly be recognized by a rapid increase in rock induration. The distinctive change in detrital mineralogy (from quartzose to feldspathic) at the contact cannot be easily observed in the field. The nature of the Van Oser - Sunset Point (Coon Valley) contact in Minnesota is variable. At two locations 40 Figure 20. Planolites in Sunset Point (Coon Valley) Member (sample DT-300, Section E). Note 9 cm long trace. Coin diameter is 2 cm. Specimen displays lower bounding surface. Figure 21. Planolites in Sunset Point (Coon Valley) Member (sample DT-128, Section B). Note intersection of traces. Coin diameter is 2 cm. Specimen displays lower bounding surface. 41 (Sections D and H) the contact is at an erosional bedding plane (truncation of stratification occurs). Abrupt conformable contacts (characterized by a sudden change in grain size) occur at three locations (Sections C, F, and Kl and transitional contacts occur at three additional localities (Sections A, B, and E). There is no evidence of significant regional erosion at the contact; it is conformable. Sunset Point (Coon Valley) - Oneota Contact As defined by Odom and Ostrom (1978) the Coon Valley - Oneota contact is placed at the top of the uppermost bed of conspicuously sandy dolomite. In Wisconsin the contact is transitional and careful examination of rocks in the transition zone is necessary for the accurate determination of the contact position. In Minnesota, the contact was studied at six locations (Sections A, B, E, H, I, and K). With the exception of the abrupt contact at Section H, the nature of the contact is transitional (refer to Chapter VII). The illustrations of the measured sections of the Jordan Sandstone in Appendix 3 do not distinguish the increasing dolomite content typical of the uppermost portions of the Sunset Point (Coon Valley) Member. 42 Chapter III PALEONTOLOGY M'.ACROFOSSILS Macrofossils were not observed in the Jordan Sandstone at the locations described in this study. Previous work on the biostratigraphy of the Jordan Sandstone was reviewed by Berg and others (1956). Generally, trilobites are the predominant macrofossils that occur in Jordan strata. These trilobites are divided into the Calvinella and Saukiella subzones of Howell and others and Nelson (1956). Calvinella spiniger, Dikelocephalus marginatus and Eurekia comprise the Calvinella subzone. Saukeilla pepinensis, Dikelocephalus marginatus, and locally, Walcottaspis vanhornei are the predominant species in the Saukiella subzone. Calvinella fauna occur in both the Jordan Sandstone and the underlying Lodi member of the St. Lawrence Formation. Saukiella fauna occur predominantly in Jordan strata and locally in underlying Lodi Member rocks. Typically, the upper strata of the Jordan Sandstone are devoid of fossils but fauna high in the stratigraphy at Stillwater, Minnesota and Scott County, Minnesota have been interpreted to represent the Saukiella subzone (Berg and others 1956). More recently, Kapchinske (1980) collected fossils from the Coon Valley Member high in the Jordan strata near Whitehall, Wisconsin. The assemblage identified consisted of Calvinella 43 tenuisculpta, Stenopilus latus, Euptychaspis kir)ci, Dikelocephalus tbwaites:, Saukiella, and Tellerina. Kapchinske (1980) also collected fossils from the Waukon Member of the Jordan Sandstone at DeSoto, Wisconsin. Fossils of only one species, Calvinella tenuisculpta, comprised the fauna. Porter (1978) described molds of whole brachiopod valves, trilobite free cheeks, and a hyolithid valve located in the Norwalk Member of Jordan strata at Arcadia, Wisconsin. MICROFOSSILS A total of eighteen samples were disaggregated and examined for conodont microfossils. The samples were representative of the finest grained strata found in each member of the Jordan Sandstone. Typically, the samples were obtained from thin layers of shale and siltstones within very fine- and fine-grained sandstone. Stone (1987) and Brasier (1980) outlined investigative laboratory techniques used in the study of conodonts. Sample disaggregation was accomplished using a bath of dilute acetic acid to dissolve calcareous cements. Once disaggregated, the mud- and clay-sized grains were removed by washing over a 200-mesh sieve. Conodonts were concentrated using the heavy liquid tetrabromoethane (specific gravity 2.96) and the resulting concentrates, 44 predominantly iron oxides, were dried and scanned on a picking tray. Of the eighteen samples selected for disaggregation and concentration, only one sample CDT-305) contained conodonts. The sample was from the lowest 2 cm of the Oneota Formation just above the contact with the underlying Sunset Point Member of the Jordan Formation. A total of 101 conodonts and conodont fragments were recovered from the specimen. The assemblage consists of conodonts from the families Oneotodontidae (Clark and others 1981, p. 117) and Prepanoistodontidae (Clark and others 1981, p. Specifically, 21 Oneotodontidae conodonts were identified form the genus Semiacontiodus, 18 from the genus Monocostodus, and 1 from the genus Oneotodus. Seven Drepanoistodontidae conodonts ·were identified from the genus Scandodus. Fifty-four conodonts and conodont fragments could not be identified. Melby (1967) obtained conodonts from both the Van Oser and Sunset Point (Coon Valley) Members of the Jordan Sandstone in southwestern Wisconsin. Conodonts from the genus Semiacontiodus were identified in the Van Oser Member and Acodus was identified in the Sunset Point (Coon Valley) Member. Furnish (1938) identified 20 species of conodonts from 12 genera in the overlying Oneota Formation. 45 Discussion and interpretation of the paleontology of the Jordan Sandstone are presented in Chapter VII. 46 Chapter IV PALEO CURRENTS Paleocurrent measurements of cross-bedding foreset inclination directions were made at all Jordan Sandstone measured sections in this study. Both trough cross-bedding and planar cross-bedding foresets were measured. So that measurements would be as unbiased as possible, not more than one measurement was taken from a cross-bedding set. Trough bedding axis plunge orientations visually estimated from vertical outcrop surfaces were not included in the database because the author perceived that the reproducibility of his estimates was equivocal and in most instances the polarity of the trough axis plunge could not be readily distinguished. More experienced investigators may encounter less difficulty in obtaining reproducable estimates. All cross-bedding foreset measurements are illustrated in their correct stratigraphic positions for each measured section in Appendix 3. Measurements are also displayed visually using 30-degree class interval rose diagrams in Figures 22, 23, 21.., 25, and 26. Van Oser Member measurements (Figure 22) resulted in two bimodal-bipolar rose diagrams (Sections E and L), one weakly bimodal-bipolar rose diagram (Section H), two trimodal rose diagrams (Sections F and!), and two ambiguous but possibly trimodal rose diagrams (Sections A and B). Four rose diagrams (Sections C, D, G, and K) do not 47 INDEX MAP 50KM SCALE r N SECTION G n=• Figure 22. Paleocurrent rose diagrams for the Van Oser Member of the Jordan Sandstone in Minnesota. Paleocurrent measurements are of trough cross- bedding and planar cross-bedding foreset inclination directions. 48 INDEX MAP 0 50KM SECTIONH n=9 SCALE Ni 8ECTIOHD n=4 SECTION A n=15 Figure 23. Paleocurrent rose diagrams for the Norwalk Member of the Jordan Sandstone in Minnesota. Paleocurrent measurements are of trough cross- bedding and planar cross-bedding foreset inclination directions. 49 ..DEX MAP Q S· :::tl ...IP 0 50KM SCALE f N SECTION C ,. n=• SECTION B :..,A n=6 ,,..... Figure Paleocurrent rose diagrams for the Sunset Point (Coon Valley) Member of the Jordan Sandstone in Minnesota. Paleocurrent measurements are of trough cross-bedding and planar cross-bedding foreset inclination directions. 50 INDEX MAP 0 50KM SCALE I N Figure 25. Paleocurrent rose diagrams summarizing all measurements taken in the Norwalk, Van Oser, and Sunset Point (Coon Valley) Members of the Jordan Sandstone in Minnesota. Paleocurrent measurements are of trough cross-bedding and planar cross-bedding f oreset inclination directions. 51 n=16 SUNSET POINT (COON VALLEY) MEMBER n=163 VAN OSER MEMBER n=44 NORWALK MEMBER Figure 26. Paleocurrent rose diagrams summarizing all measurements taken in the Jordan Sandstone (all members) in Minnesota. Paleocurrent measurements are of trough cross-bedding and planar cross-bedding foreset inclination directions. 52 represent a sufficient number of measurements to be meaningful. Norwalk Member measurements (Figure 23) resulted in one bimodal rose diagram (Section A), one predominantly unimodal rose diagram (Section H), and one bimodal-bipolar diagram (Section I). One rose diagram (Section D) does not represent a sufficient number of measurements to be meaningful. Similarly, the three Sunset Point (Coon Valley) Member rose diagrams (Figure represent insufficient data to be meaningful. Jordan Sandstone paleocurrent data may be visually summarized in two additional ways: (1) grouped according to stratigraphic member and (2) grouped according to measured section location. Measurements grouped according to stratigraphic member (Figure 25) show the predominance of Van Oser Member paleocurrent data and a possible bimodal character for all three members. Measurements grouped according to measured section location (Figure 26) also show the predominance of Van Oser Member data (compare similarities with Figure 22). Paleocurrent data from the Jordan Sandstone in south- central and western Wisconsin have been collected by Farkas (1960), Dalziel and Dott (1970), and Michelson and Dott (1973). These studies concluded that southerly vector means are regionally predominant in the Jordan Sandstone (Table 1). Miall p. 258) noted that 25 measurements per sample station are commonly regarded as the minimum necessary to obtain a statistically significant paleocurrent trend. In this study only four measured section locations (Sections A, B, H, and I) provided at least 25 paleocurrent measurements. Paleocurrent vector means calculated for Sections A, B, H, and I are, respectively, 131, 185, and 275 degrees. This suggests that southerly vector means also predominate in Minnesota. However, the bimodal to trimodal character of paleocurrent data at Sections A, B, H, and I renders the Minnesota vector means equivocal. Paleocurrent data variances for Sections A, B, H, and I are, respectively, 7067.9, 7218.5, 7560.2 and 8953.3. Potter and Pettijohn (1963) noted that the most common paleocurrent variance for marine depositional environments ranges from values of 6000 to 8000. Paleocurrent vector mean calculations are summarized by Potter and Pettijohn (1977). Paleocurrent variance calculations are summarized by Curry (1956). Paleocurrent data used in calculations for this study are presented in Appendix Discussion and interpretation of Jordan Sandstone paleocurrent data occur in Chapter VII. 54 Area Author No. Obs. Indicator Vector S.D. r. Mean South-Central Farkas (19601 45 Cross-bed dip 199° +1080 0 .17NS Baraboo-Dells Dott (19701 766 Cross-bed dip 250° +122° O.llNS Baraboo Islands* Dott (1970) 200 Trough axis plunge 1570 +95° 0.25 Baraboo-Dells Dott (1970) 331 Trough axis plunge 167° +e1° 0.35 West-Central Michelson 1467 Trough axis plunge 180° +65° 0.53 * Localities within 6 Jon of old monadnocks s:t1owing apparent influence of the islands upon paleocurrents. This category is a sub-set of "Baraboo-Dells". NS Statistically non-significant (i.e. showing no significant orientation). r Vector magnitude varies from zero (completely random) to 1.0 (perfectly oriented I. Table 1. Paleocurrent data from Jordan Sandstone in south- central and western Wisconsin. (After Farkas 1960, Dalziel and Dott 1970, and Michelson and Dott 1973). 55 Chapter V PETROLOGY One hundred and twelve samples of the Jordan Sandstone in Minnesota were selected for petrographic etudy. Samples were selected with emphasis on providing adequate coverage of geographical, stratigraphical and lithological variations. Petrographic thin sections were made from each sample. Each thin section was examined to determine mineralogical, textural and diagenetic characteristics. A modal analysis was determined for 107 thin sections. For each modal analysis, the mineralogy was analyzed at 60 equally-spaced points on 10 random parallel traverses perpendicular to bedding (600 points). Sorting, rounding and grain-size range and mean were petrographically estimated for all thin section framework components. Grain- size estimates for all 358 lithological hand specimens were completed using a binocular microscope. Fifteen heavy mineral mounts were also petrographically examined. Diagenesis is described in a separate chapter (Chapter VI) to emphasize the post-depositional changes. To facilitate comparison of the detrital components of Jordan Sandstone samples, the quartz, feldspar and rock fragment content of each thin section was recalculated to 100% and plotted on a ternary diagram. The detrital components of samples from the Norwalk and Sunset Point 56 {Coon Valley) Members with greater than 50 to 75% carbonate are also plotted but are distinguished by a separate symbol. Appendix 2 includes the locations of thin sections within their respective measured stratigraphic sections. Discussion and interpretation of the following petrologic descriptions are in Chapter VII. OPERATIONAL DEFINITIONS Twenty detrital, intrabasin·a1 and authigenic components of the Jordan Sandstone were identified during modal analysis. Common quartz, vein quartz, composite quartz, stretched metamorphic quartz, chert, orthoclase, microcline, plagioclase, lithic fragments, dolostone, muscovite and opaques comprise the detrital components. Glauconite and oolites comprise the intrabasinal components. Dolomite, calcite, quartz, potassium feldspar, illite and chlorite comprise the authigenic components. For the purpose of modal analysis, common quartz is defined within this study as monocrystalline quartz with either undulose or non- undulose extinction. Extremely rare monocrystalline quartz grains with abraded quartz overgrowths are also classified as common quartz. Vein quartz is defined herein as monocrystalline quartz containing abundant microscopic vacuoles and which has a distinctive cloudy microscopic appearance. Composite quartz is defined herein as polycrystalline quartz with uniformly sized crystals having 57 typically straight (polygonal) crystal contacts. Stretched metamorphic quartz is herein defined as polycrystalline quartz with elongate crystals having slightly sutured crystal contacts. Chert is defined herein as rnicrocrystalline quartz. Lithic fragments are defined herein as either siltstone, very fine-grained sandstone or fine-grained sandstone rock fragments. Dolostone is defined herein as those lithic fragments which are composed of crystalline dolomite. The remaining components have standard definitions (see Kerr 1977) and are described below for their occurrences within each stratigraphic member of the Jordan Sandstone. NORWALK MEMB.1;R Mineralogy Nineteen petrographic thin sections from the Norwalk Member were examined. All thin sections were stained with blue epoxy so that pores are more easily recognizable. Fourteen thin sections were stained with a sodium cobaltinitrite solution to aid in the identification of potassium feldspar. Five thin sections were stained with Alizarin Red to distinguish small amounts of calcite in predominantly dolomitic cements. A modal analysis was determined for each thin section. According to the classification of Pettijohn and others (1973, p. 158), of the 19 Norwalk Member samples examined, 8 58 are subarkoses and 11 are arkoses (Table 2). Five of the nineteen samples contain greater than 50% carbonate and would normally be named arkosic or subarkosic sandy dolomites. The mean detrital composition of the 19 Norwalk Member samples is that of an arkose (Figure 27). Quartz and potassium feldspar grains comprise the major detrital components of Norwalk Member rocks. Minor detrital components include glauconite, muscovite, garnet, tourmaline, zircon, and opaque minerals such as hematite and limonite. Comprising to of total sample volumes, common monocrystalline quartz grains are the predominant detrital component of Norwalk Member rocks. Due to the very fine grain-size of quartz grains in this member of the Jordan Sandstone, no attempt was made to obtain a ratio of quartz grains with undulose C>1°> extinction to those with straight extinction. Small abundances, typically less than 1%, of vein and polycrystalline quartz grains occur in some samples. Two types of potassium feldspar, orthoclase and rnicrocline, occur in Norwalk Member rocks. Orthoclase and rnicrocline grains account for to 28% and 1 to 5%, respectively, of total sample volumes. Orthoclase grains are typically untwinned but rnicrocline grains generally exhibit either tartan twinning (Hurlbut and Klein 1977, 59 SAMPLE: DT- 5 8 9 12 13 18 80 81 85 DETRITAL_GRAINS Corrunon Quartz 20 5'* lsB 14 26 17 Is 8 20 27 31 Vein Quartz 0 0 0 0 0 0 tr 0 0 tr Composite Quartz 0 0 0 0 0 0 tr tr tr 1 Str. Meta. Quartz 0 0 0 0 0 0 0 0 0 0 Chert 0 0 0 0 0 0 0 0 0 0 Felds:ear Orthoclase 7 7 6 5 10 Is 9 14 12 7 Microcline 1 3 2 3 Is Is 9 5 3 3 Plagioclase 0 0 0 0 0 0 0 0 0 0 Lithics 0 0 0 0 0 0 0 0 0 0 Miscellaneous Muscovite tr tr 0 0 tr tr 0 0 0 0 Opaques 3 2 2 3 3 0 2 5 tr 1 INTRABASINAL Glauconite 0 0 0 0 tr 0 0 0 0 0 AUTHIGENIC Dolomite 6/s 0 31 62 tr 7 ls 0 28 33 44: Calcite tr 0 0 1 4.2 0 0 tr 0 0 Quartz 1 1 tr 0 tr 1 tr 3 tr K-Feldspar 2 ,,. 3 5 0 9 13'* 9 6 Illite tr tr tr 0 0'* 0 0 0 0 0 Porosity 1 28 8 8 10 0 23 11 12 7 Table 2. Norwalk Member modal analysis data. See next page. 60 SAMPLE: DT- 86 145 149 192 199 204 206 257 .D.ETRITAL GRAINS Quartz Common Quartz 23 23 29 18 31 36 41 4-6 46 Vein Quartz 0 0 tr 0 0 1 tr 0 tr Composite Quartz 0 0 tr 0 0 0 0 tr 0 Str. Meta. Quartz 0 0 0 0 0 0 0 0 0 Chert 0 0 0 0 0 0 0 0 0 Feldspar Orthoclase 8 7 11 23 8 8 4 10 8 Microcline 3 3 4 tr 3 5 4 2 3 Plagioclase 0 0 0 0 0 0 0 0 0 Lithics 0 0 tr 0 0 0 0 0 0 Miscellaneous Muscovite tr 0 0 tr 0 0 0 0 0 Opaques 3 4 tr 3 3 1 1 1 1 INTRABASINAL Glauconite 0 tr 0 0 0 0 0 0 0 AUTHIGENIC Dolomite 48 0 0 41 0 8 1 5 5 Calcite 0 41 0 0 0 0 0 0 0 Quartz 1 tr 2 tr 1 1 2 1 1 K-Feldspar 5 8 21 11 19 13 10 14 16 Illite 0 0 0 tr 0 0 0 0 0 Porosity 9 14 32 4 31,i, 27 37 21 20 61 NORWALK MEMBER Q • Sample OFL 19 Samples Figure 27. Detrital compositions of Norwalk Member samples. Triangle classification from Pettijohn, Potter and Siever (1973, p. 158). 62 p. 101) or spindle twinning associated with quadrille structure (Kerr 1977, p. 306). As further described in Chapter VI, feldspar detrital grains typically occur with subhedral to euhedral authigenic overgrowths. Opaque grains, comprising 0.5 to 5% of total sample volumes, are the predominant minor detrital component of Norwalk Member rocks. Hematite and limonite are the opaque minerals typically present. Other minor components collectively comprise less than 1% of total sample volumes; muscovite, tounnaline, garnet, zircon and glauconite may occur in trace amounts. Just one grain of plagioclase was observed. A photomicrograph of a typical Norwalk Member specimen is presented in Figure 28. Mineralogical changes, within or between individual measured sections of the Norwalk Member, occur at random; no horizontal or vertical trends were identified. Texture Relative proportions of framework grains, cement and porosity greatly vary in Norwalk Member rocks. The proportions change vertically within individual measured sections and also horizontally between sections. Framework grains comprise from 24 to 68% of sample volumes (mean = non-detrital minerals account for 6 to 76% of sample volumes (mean= 39%), and porosity accounts for 0 to 34% of sample volumes (mean= 15%). Framework textures are either Figure 28. Photomicrograph of a typical Norwalk Member specimen (sample Section C). Note arkosic composition (feldspar stained yellow, quartz remains white) and high porosity (stained blue). Authigenic overgrowths on detrital feldspar grains have a subhedral to euhedral morphology. Width of view approximately 0.5 mm wide. Plane-polarized light. 64 intact or dispersed; no condensed framework textures were observed. Framework grains are typically oriented at random but muscovite grains are generally oriented subparallel to stratification. Grain contacts range from concave-convex to floating (no contact in plane of thin section); sutured contacts do not occur. Long and point grain-contacts predominate. Types of framework grain contacts are illustrated in Figure 29. Mean grain-size of Norwalk Member samples ranges from silt (0.03 mm) to fine sand (0.20 mm) but very fine sand mean grain-sizes (0.0625 to 0.125 mm) predominate. A coarsening-upward grain-size trend occurs in Sections A, J, H, and I but a fining-upward trend occurs in Section D. Typically there is no difference in mean grain-size between quartz and feldspar detrital grains but in some samples, the mean grain-size of quartz exceeds that of feldspar by approximately 0.01 to 0.02 mm. According to the sorting classification of Pettijohn and others (1973, p. 585), Norwalk Member samples are typically well sorted (standard deviation values 0.35 to 0.50). According to the rounding classification of Power (1953), Norwalk Member detrital grains are typically subrounded but in some samples subangular or rounded grains predominate. Floating groins Figure 29. Types of framework grain contacts. (From Pettijohn and others 1973, p. 91). 66 VAN OSER MD!BER Mineralogy Fifty-eight petrographic thin sections from the Van Oser Member were examined. All thin sections were stained with blue epoxy so that pores are more easily recognizable. Forty-eight thin sections were stained with a sodium cobaltinitrite solution to aid in the identification of potassium-feldspar. Four thin sections were stained with Alizarin Red to distinguish calcite from dolomite in mixed carbonate cements. A modal analysis was determined for each thin section. According to the classification of Pettijohn and others (1973, p. 158), of the 58 Van Oser Member samples examined, C..9 are quartz arenites and 9 are subarkoses. The mean detrital composition of the 58 Van Oser Member samples is that of a quartz arenite (Figure 30). Quartz is by far the major detrital component in Van Oser Member rocks. Minor detrital components include potassium feldspar, garnet, tourmaline, zircon, muscovite and iron-oxide opaque minerals. The modal analyses of Van Oser Member samples are presented in Table 3. A photomicrograph of a typical Van Oser Member specimen is presented in Figure 31. Six varieties of quartz grains occur in Van Oser rocks: non-undulose common monocrystalline quartz, undulose <>1° 67 VAN OSER MEMBER a • Sample QFL 58 Samples Figure 30. Detrital compositions of Van Oser Member samples. Triangle classification from Pettijohn, Potter and Siever (1973, p. 158). 68 SAMPLE: DT- 21 24 28 35 36 37 40 4__5 ___.!i__7. ___ DETRITAL GRAINS Qua.x::tz Common Quartz 62 60 60 59 53 67 64 70 70 69 Vein Quartz 1 2 1 tr 1 1 tr 1 1 1 Composite Quartz tr 1 1 0 tr tr 1 tr 1 tr Str. Meta. Quartz 0 0 0 0 0 0 0 0 0 0 Chert 0 0 0 0 0 0 0 0 tr 0 Orthoclase tr tr 1 1 1 0 tr 1 tr 0 Microcline 1 tr tr 1 1 0 0 1 tr 0 Plagioclase 0 0 0 0 0 0 0 0 0 0 Lithics 0 0 0 0 0 0 0 0 0 0 Miscellaneous Muscovite 0 0 0 tr 0 0 0 0 0 0 Opaques 1 3 1 1 2 4 2 1 1 1 INTRABASINAL Glauconite 0 0 0 0 0 0 0 0 0 0 AUTHIGENIC Dolomite 0 0 0 0 0 0 0 0 0 1 Calcite 32 33 35 36 42 0 0 0 0 0 Quartz 2 1 tr 1 tr 7 3 3 4 2 K-Feldspar 1 0 0 0 tr 0 0 0 1 0 Illite 0 0 0 tr 0 0 0 0 0 0 Porosity 0 1 tr tr 0 21 29 23 22 26 Table 3. Van Oser Member modal analysis data. See next five pages. 69 OT- 89 91; 98 103 105 109 114 117 153 157 :.TR.ITAL GRAINS iartz ·mmon Quartz 52 53 67 53 65 65 68 65 53 68 ·in Quartz 0 tr 1 tr 2 1 0 0 0 tr mposite Quartz 1 tr 2 1 tr 0 tr 1 tr 0 r. Meta. Quartz 0 0 0 0 0 0 0 tr 0 0 ert 0 0 0 0 0 tr 0 0 0 0 1lds:ear ·thoclase 5 tr 1 tr 1 0 0 1 3 tr .crocline 1 tr tr 0 tr 0 0 0 1 0 agioclase 0 0 0 0 0 0 0 0 0 0 .thics 0 0 0 0 0 0 0 0 0 0 scellaneoys scovite 0 0 0 0 0 0 0 0 0 0 aques 1 tr 0 2 1 0 0 tr 1 tr I'RABASINAL :i.uconite 0 0 0 0 0 0 0 0 0 0 l'HIGENIC .omite 9 17 0 32 13 0 0 1 8 1 .cite 29 28 0 tr 0 0 0 0 17 18 .rtz 1 0 2 tr 0 3 6 1 1 'eldspar 1 0 tr 0 tr'* 0 0 0 I; tr ite 0 0 tr 0 0 0 0 0 0 0 osity tr tr 27 10 11; 3L.i, 29 26 12 12 70 \ siAMPLE: DT- 158 160 166 172 210 213 223 227 234 235 .DlETRITAL GRAINS Quartz Co•mmon Quartz 68 69 63 66 60 62 55 55 62 72 Ve:in Quartz tr tr tr 0 2 tr 0 2 tr tr Composite Quartz 0 0 0 1 tr 2 0 tr tr 0 Str. Meta. Quartz 0 0 0 0 0 0 0 0 0 0 Chert 0 0 0 0 0 0 0 tr tr tr 0 0 0 0 3 tr ,. tr tr 0 Ml crocline 0 0 0 0 1 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 Lithics 0 0 0 0 0 0 0 0 0 0 Miscellaneous Muscovite 0 0 0 0 0 0 0 0 0 0 Opaques 0 0 0 13 tr 0 1 1 1 3 INTRABASINAL Glauconite 0 0 0 0 0 0 0 0 0 0 AUTHIGENIC DolomiteI 1 1 tr tr 1 8 0 21 10 0 Calcite 0 0 0 0 tr 0 0 11 21 0 1 tr 2 1 1 1 2 1 0 1 K-Feldspar 0 0 0 0 5 tr 6 tr 1 0 Illite 0 0 0 0 0 0 0 0 0 0 Po:t·osity 30 30 3/s 18 26 27 30 9 5 2/s 71 DT- 264 268 269 275 282 286 287 289 311 315 ID•TRITAL GRAINS Q\tartz colmmon Quartz 57 68 52 39 4-8 72 57 61 69 68 ve\in Quartz 1 1 1 1 tr 2 1 1 1 1 site Quartz 1 tr tr 0 tr 1 1 tr 1 1 Meta. Quartz 0 0 0 0 0 0 0 0 0 0 Cht rt tr 0 0 0 0 0 tr 0 0 0 [elds:ear 01thoclase 3 0 10 5 1 tr 2 0 tr Mi! crocline 1 0 2 2 '* 2 tr tr 1 0 0 Plagioclase 0 0 0 0 0 0 0 0 0 0 -Lithics , 0 0 0 0 0 0 0 0 0 0 Miscellaneous Muscovite 0 0 1 0 0 0 0 0 0 0 Opaques tr 1 2 '* 2 tr 2 1 2 2 INTRABASINAL Glauconite 0 0 0 0 0 0 0 0 0 0 AuTHIGENIC 13 8 tr 11 18 0 25 0 0 0 Ca] cite 0 10 0 26 0 0 0 0 0 0 Qu;riz 1 1 tr tr 1 2 1 2 2 3 K- t ldspar 3 0 10 3 1 tr 2 0 0 Ill"te 0 0 0 0'* 0 0 0 6 0 0 Por sity 20 11 22 9 22 21 13 25 26 26 72 DT- 317 320 322 325 329 331 334 335 342 31,i.3 GRAINS Colmmon Quartz 69 71 67 70 73 70 t.2 60 71 72 Vein Quartz tr 1 2 1 1 1 tr 1 1 tr corposite Quartz tr tr 1 1 1 1 0 1 tr 0 St!r. Meta. Quartz 0 0 0 0 0 0 0 0 0 0 Chert tr 0 0 0 0 0 0 0 0 tr FeldsEar Orthoclase 0 0 tr 0 tr tr ,,. 3 tr 0 Microcline 0 0 0 0 0 0 2 1 0 0 Plagioclase 0 0 0 0 0 0 0 0 0 0 Lithics 0 0 0 0 0 0 0 0 0 0 Miscellaneous Muscovite 0 0 0 0 0 0 0 0 0 0 Opaques ,,. 3 1 tr tr 0 2 1 0 tr INTRABASINAL Glauconite 0 0 0 0 0 0 0 0 0 0 AUTHIGENIC Do ] omite 0 0 tr tr 0 0 18 0 0 0 0 0 0 0 0 0 0 0 0 0 Quartz 2 1 1 tr tr 2 tr 3 ,,. 1 1 K-Fjeldspar 0 0 0 0 0 0 6 3 0 0 Ill:ite 0 0 0 0 0 0 0 0 0 0 Porosity 25 21.. 27 27 21,i, 27 25 28 23 26 73 51\MPLE: DT- 3i.t.. 3t..6 3t..8 350 351 353 35/s 357 JllITRITAL GRAINS Qu1artz- , Co:mmon Quartz 7 '* 7 '* 73 70 69 72 69 69 Vein Quartz 1 1 tr tr 2 1 1 1 Co1:nposite Quartz tr tr tr 1 1 1 tr 0 1 Stf . Meta. Quartz 0 0 0 0 0 0 0 0 Chert 0 0 0 0 tr tr 0 0 Fj ldsEar Orthoclase 0 0 0 0 0 0 0 0 Microcline 0 0 0 0 0 0 0 0 Plagioclase 0 0 0 0 0 0 0 0 Lithics 0 0 0 0 0 0 0 0 Miscellaneous Muscovite 0 0 0 0 0 0 0 0 Opaques tr tr tr tr 0 1 tr tr INTRABASINAL Glauconite 0 0 0 0 0 0 0 0 AUTHIGENIC Dolomite 0 0 0 0 0 0 0 0 Calcite 0 0 0 0 0 0 0 0 Quartz 1 2 2i. 7 3 K-Feldspar 0 0 '*0 '*0 0 0 0 '*0 Illite 0 0 0 0 0 0 0 0 Porosity 23 23 23 25 '* 19 27 26 74 Figure 31. Photomicrograph of a typical Van Oser Member specimen (sample DT-109, Section B). Note quartz arenite composition and high mineralogical and textural maturity. Field of view approximately 5.0 mm wide. Crossed nicols. 75 extinction) common monocrystalline quartz, vein quartz, polycrystalline quartz with polygonal crystal boundaries, stretched polycrystalline (metamorphic) quartz and chert. Together non-undulose and undulose corrmon monocrystalline quartz grains comprise from 39 to 74% of total sample volumes. Vein quartz and polycrystalline quartz typically comprise less than 2% of total sample volumes. Stretched polycrystalline quartz and chert grains occur in trace amounts (less than 0.5%) in 13 samples. The ratio of undulose to non-undulose common monocrystalline quartz grains was determined (Appendix 5) for 27 of the 58 Van Oser Member samples examined. Of the 27 samples, 18 contained more undulose grains than non- undulose ones. Of the 10,133 common quartz grains examined in the 27 samples, 5901 undulose grains and 4232 non- undulose grains were observed. This is a ratio of approximately 1.4 to 1. Two types of potassium feldspar, orthoclase and microcline, occur in the Van Oser Member. Orthoclase grains comprise 0 to 10% of total sample volumes but values of approximately 1% are typical. Microcline grains comprise 1 to 2% of total sample volumes. Large changes in detrital mineralogy within or between individual measured sections of the Van Oser Member are rare; the composition is very homogeneous. 76 Texture Framework grains comprise from 50 to 80% of total sample volumes (mean= 68%), non-detrital minerals account for 0 to of total sample volumes (mean c 13%) and porosity accounts for 0 to of sample total volumes (mean • 20%). No general trends occur in the relative proportions of framework grains, cement and porosity but two locations (Sections F and G) have consistently low proportions of cement (typically 1 Framework textures are either intact or dispersed; no condensed frameworks were observed. Framework grain contacts range from concavo-convex to floating but long and point contacts predominate. Sutured contacts do not occur and grains are generally oriented at random. Mean grain-size of Van Oser Member samples ranges from fine sand (0.15 mm) to coarse sand (0.70 mm) but medium sand mean grain-sizes predominate (0.25 mm to 0.50 mm). Coarsening-upward grain-size trends occur in portions of three measured sections CA, D, and E). In general, detrital potassium feldspar grains occur only as grain-sizes less than 0.20 mm in Van Oser Member samples. According to the sorting classification of Pettijohn and others (1973, page 585), Van Oser Member samples are typically well sorted (standard deviation values 0.35 to 0.50). Very well sorted rocks commonly occur at three 77 locations (Sections B, D, and F). Poorly sorted flat-pebble conglomerate horizons also occur in Van Oser 8trata. According to the rounding classification of Powers (1953), Van Oser detrital grains are typically rounded to well rounded; rounded grains predominate. WAUKON MEMBER Four petrographic thin sections from the Waukon Member were examined. According to the classification of Pettijohn and others (1973, p. 158), 2 of the samples are arkoses and 2 are subarkoses Grain-size in all samples is within the range for very fine sand (0.0625 to 0.125 nun). The samples are moderately to very well sorted and grains are typically subangular to subrounded. Essentially, no mineralogical or textural differences exist between Waukon Member and Norwalk Member samples. Modal analysis for Waukon Member samples may be compared with Norwalk Member analysis (Table 2). As discussed in Chapter VII it may be more appropriate to identify 'Waukon' strata as Norwalk strata that inter-tongue into the Van Oser Member than to distinguish it as a separate member in the Jordan Sandstone. SUNSET POINT (COON VALLEY) MEMBER Mineralogy Twenty-four petrographic thin sections from the Sunset Point (Coon Valley) Member were examined. All thin sections were stained with blue epoxy so that pores are more easily 78 SAMPLE: DT- 29 217 218 DETRITAL Q:uax:tz Common Quartz 31 45 34 50 Vein Quartz 0 1 0 0 Composite Quartz 0 tr tr tr Str. Meta. Quartz 0 0 0 0 Chert 0 0 0 0 Orthoclase 13 10 12 9 Microcline 6 4 3 Plagioclase 0 0 0'* 0 Lithics 0 0 0 0 l!IisQellaoeQll:;i Muscovite 0 0 0 tr Opaques 2 tr tr tr 1NTRAl3ASIBAL Glauconite 0 0 0 0 AQJHI GfilU C Dolomite tr 0 0 Calcite tr 0 '*0 tr Quartz 1 tr 1 1 K-Feldspar 12 8 15 15 Illite tr 0 0 0 Porosity 34 32 30 22 Table Waukon Member modal analysis data. 79 recognizable. Nineteen thin sections were stained with a sodium cobaltinitrite solution to aid in the identification of potassium feldspar. Twelve thin sections were stained with Alizarin Red to distinguish small amounts of calcite from dolomite. Classification of Sunset Point (Coon Valley) Member samples is difficult due to high carbonate (predominantly dolomite) content; 19 of the samples contain greater than 50% carbonate and 8 samples contain greater than 75% carbonate. Carbonate content of the samples ranges from 18 to 98%, reflecting the heterogeneous nature of this member. Accordingly, two classifications are used; the 5 samples containing less than 50% carbonate are classified as sandstones after Pettijohn and others (1973, p. 158) and the remaining 19 samples are classified after Dunham (1962). Dunham's (1962) classification groups carbonates on the basis of their depositional texture. Textural features of many Sunset Point (Coon Valley) thin sections, though now dolomite, are commonly recognizable. Dolomitized equivalents of most rock types in Dunham's (1962) classification are present in Sunset Point (Coon Valley) strata. According to Pettijohn and others (1973, p. 158), 2 Sunset Point (Coon Valley) Member samples are subarkoses and 3 samples are arkoses. The mean detrital composition of the 00 5 samples is that of a subarkose (Figure 32). If the detrital compositions of the 5 additional samples with 50 to 60% carbonate are included, the mean is still in the subarkose range. According to Dunham (1962), the 19 carbonate-rich samples are classified as follows: 5 crystalline dolomites, 2 packstones, 2 homogeneous wackestones and 10 heterogeneous wackestones. Wackestones are the predominant lithology. Photomicrographs of a wackestone, an arkose, a crystalline dolomite and an oolitic packstone are presented in Figures 33, 35 and 36, respectively. The modal analyses of Sunset Point (Coon valley) Member samples are presented in Table 5. Quartz and potassium feldspar grains comprise the major detrital components and minor components include glauconite, muscovite, hematite and lirnonite. Dolomite is the major carbonate component but calcite is predominant in one sample CDT-66). Oolites occur in three samples. Diagenesis and dolomitization are discussed in Chapters VI and VII. Conunon monocrystalline quartz grains comprise 2 to 50% of total sample volumes in Sunset Point (Coon Valley) Member rocks. The ratio of quartz grains with undulose <>1°> extinction to those with straight extinction was determined (Appendix for 5 samples. Grains with straight extinction predominate; of the 1076 grains examined, 358 had undulose 81 SUNSET POINT MEMBER ( COON VALLEY ) a • Sample OFL 9 Samples Figure 32. Detrital composition of Sunset Point (Coon Valley) Member samples. Triangle classification from Pettijohn, Potter and Siever (1973, p. 158) • 82 Figure 33. Photomicrograph of a typical dolomitized wackestone in the Sunset Point (Coon Valley) Member (sample Section B). Note fine dolomite matrix (A), oolitic rind on intraclast (B), poorly size-sorted quartz and potassium feldspar grains (C) and rounded quartz grain CD). Porosity stained blue. Circular blue spot (E) within oolitic rind is most likely a plucked grain. Width of view approximately 5.0 mm. Plane-polarized light. Dolomitized equivalents of all rock types in Dunham's (1962) classification occur in the Sunset Point (Coon Valley) Member. 83 Figure Photomicrograph of a typical arkose in the Sunset Point (Coon Valley) Member (sample DT- 176 , Section C). Note quartz grains (A), potassium feldspar stained yellow (B) and brown dolomite rhombohedrons (C). Porosity stained blue. Width of view approximately 2.5 nun. Plane-polarized light. Figure 35. Photomicrograph of a typical crystalline dolomite in the Sunset Point (Coon Valley) Member (sample Section 0). Crystallization of brown euhedral dolomite rhombohedrons has rendered original textural features unrecognizable. Note quartz grains 86 SAMPLE: DT- 60 61b 65 66 71 121 125 135 14Q__J44 DEl'RITAL GRAINS Quartz Common Quartz 40 16 9 29 40 35 44 50 39 4 Vein Quartz 0 1 0 0 tr tr 1 tr 1 0 Composite Quartz 1 0 0 0 0 tr tr 1 tr 0 Chert 0 tr 0 0 0 0 tr 0 tr 0 FeldsEar Orthoclase 1 0 tr 0 0 11 3 4 1 1 Microcline tr tr tr 0 tr 5 1 2 tr tr Plagioclase 0 0 0 0 0 tr 0 0 0 0 Lithics Dolostone tr 1 0 0 0 0 0 0 0 0 Miscellaneous Muscovite 0 0 0 0 0 0 0 0 0 0 Opaques 2 2 2 1 tr tr 2 1 tr 2 INTRABASINAL Glauconite 0 0 0 0 0 0 0 0 0 0 Oolites 1 51 0 0 5 0 0 0 0 0 AUTHIGENIC Dolomite 48 25 77 0 52 1 36 0 57 84 Calcite 4 2 7 70 0 0 1 0 0 Quartz tr 0 0 0 tr 4 1 11 tr 0'* K-Feldspar 0 0 tr 0 0 17 4 7 tr 0 Illite tr 2 0 0 0 0 0 0 0 0 Chlorite 1 0 0 0 0 0 0 0 0 0 Porosity 1 tr 5 0 2 26 7 24 tr 5 Table 5. Sunset Point (Coon Valley) Member modal analysis data. See next two pages. 87 SAMPLE: DT- 176 178 181 184 187 239 21,i.2 21,i.7 250 291 DETR.ITAL GRAINS QuaI:tz Common Quartz 31 27 30 22 9 39 19 2 l,i. 21 Vein Quartz 0 0 0 0 0 0 0 0 0 0 Composite Quartz 0 0 tr 0 0 tr 0 0 0 0 Chert 0 0 0 0 0 0 0 0 0 0 :[e1Q::?l2Q.r Orthoclase 7 3 8 1 0 2 3 2 Microcline 5 1 3 '*3 0 0 1 tr 1 tr'* Plagioclase 0 0 0 0 0 0 0 0 0 0 Lithics Dolostone 0 0 0 0 0 0 0 0 0 0 Muscovite 0 0 0 tr 0 0 0 0 0 0 Opaques 3 1 1 2 2 1 2 l,i. 6 5 INTRAEASINAL Glauconite 0 0 0 0 0 0 0 tr tr tr Oolites 0 0 0 0 0 0 0 0 0 0 Dolomite 16 60 33 1,i.8 73 31 61 87 71,i. 60 Calcite 0 0 3 0 0 11,i. 1 0 0 1 Quartz 2 tr 1 1 tr tr 1 0 0 0 K-Feldspar 16 2 5 5 tr 0 2 2 4 2 Illite 0 0 0 0 10 3 1 0 5 3 Chlorite 0 0 0 0 0 2 0 0 0 0 Porosity 20 6 15 15 '* 8 10 2 l,i. l,i. 88 SAMPLE: DT- 294 304 337 .Drn.ITAL GRAINS Quartz Conu-non Quartz 18 0 2 0 Vein Quartz 0 0 0 0 Composite Quartz 0 0 0 0 Chert 0 0 0 0 FeldsEar Orthoclase 4 2 7 0 Microcline tr 0 tr 0 Plagioclase 0 0 0 0 Lithics Dolostone 0 0 0 0 Miscellaneous Muscovite 0 0 0 0 Opaques 3 5 1 tr INTRAEASINAL Glauconite tr 0 tr 0 Oolites 0 0 0 0 AUTHIGENIC Dolomite 62 93 77 93 Calcite 1 tr 0 0 Quartz 0 0 0 0 K-Feldspar 3 0 2 0 Illite 5 0 B 5 Chlorite 0 0 0 0 Porosity 3 0 3 2 89 extinction and 718 had straight extinction. Grains of vein quartz, polycrystalline quartz with polygonal crystal boundaries and chert may also occur but typically account for less than 1% of total sample volumes. Potassium feldspar grains comprise 0 to 16% of total sample volumes. Of the two types of potassium feldspar present, orthoclase is more abundant: orthoclase grains typically comprise approximately 2 to of total sample volumes and microcline typically accounts for less than 2% of sample volumes. The abundance of wackestone and crystalline dolomite indicates a large carbonate mud component in many Sunset Point (Coon Valley) Member rocks. In the crystalline dolomites, detrital grains and lithic clasts comprise less than 10% of total sample volumes and in wackestones detrital grains account for 10 to approximately of total sample volumes. Oolites commonly occur with a large quartz grain nucleus. Oolite rinds may also occur around aggregates of several quartz grains bound together by carbonate mud (Figure 37). Texture In addition to heterogeneous mineralogy, Sunset Point (Coon Valley) Member samples also exhibit greater variation in texture than other Jordan Sandstone members. Framework Figure 37. Photomicrograph of oolite aggregates in a Sunset Point (Coon Valley) Member specimen (sample DT- 71, Section A). Note oolite aggregate CA), oolite with brown dolomite core (B), oolite with quartz grain core (C), poor sorting, and late calcite cement (stained red) filling secondary porosity in oolites (0). Porosity stained blue. Width of view approximately 5.0 mm. Plane- polarized light. 91 grains comprise from 0.5 to 71% of total sample volumes and porosity can account for 0 to 26% of sample volumes. Framework textures are typically dispersed but some intact frameworks occur. Framework grain contacts range from concavo-convex to floating; floating grains predominate. Sutured contacts do not occur and grains are generally oriented at random. Mean detrital grain-size of Sunset Point (Coon Valley) Member samples ranges from silt (0.05 mn) to coarse sand (0.60 mm) but fine sand sizes predominate (0.125 mm to 0.25 mm). A coarsening-upward grain-size trend occurs in the lower portion of one locality (Section C) but a fining- upward grain-size trend occurs at three localities (Sections A, D, and E). Grain sorting in Sunset Point (Coon Valley) Member rocks varies widely from sample to sample; sorting standard deviation values range from greater than 2.00 (very poorly sorted) to 0.30 (very well sorted). However, rounding of grains is more homogeneous throughout the member; rounded and subrounded grains predominate. Carbonate matrix textures are heterogeneous in the wackestones of the Sunset Point (Coon Valley) Member. Large differences in crystalline dolomite matrix grain-size commonly occur in random directions at thin section scale. Fossils and delicate sedimentary structures such as very 92 thin lamination, which may have been present previous to dolomitization, do not occur in the specimens examined. HEAVY MINERALS Fifteen heavy mineral mounts and all 112 petrographic thin sections were examined to determine the heavy mineral assemblage of the Jordan Sandstone in Minnesota. In addition to the almost ubiquitous iron-oxides hematite and limonite, only garnet and tourmaline were identified in the heavy mineral mounts. However, zircon was identified in numerous petrographic thin sections. Garnet grains (Figure 38) are typically rounded, etched and a light red-brown color. Tourmaline grains (Figure 39) are typically well- rounded, green and some contain a distinctive core. Zircon grains are typically subrounded to rounded and brown. Previous workers (Ockerman 1930, Boardman 1952) identified small amounts of rutile, staurolite, kyanite, augite and ilmenite-leucoxene in Jordan strata and noted the predominance of garnet, zircon and tourrnaline. 93 Figure 38. Photomicrograph of a rounded etched garnet grain, Van Oser Member (sample DT-237, Section 0). Field of view approximately 2.5 mm wide. Plane polarized light. Figure 39. Photomicrograph of a well-rounded green tourmaline grain, Van Oser Member (sample DT- 237, Section D). Field of view approximately 0.5 mm wide. Plane polarized light. 94 Chapter VI DIAGENESIS Diagenesis, as defined by Bates and Jackson (1980, page 171) includes all chemical, physical and biological changes undergone by a sediment after its initial deposition and during and after its lithification, exclusive of surficial \ alteration (weathering) and metamorphism. The typical range of temperature, pressure and chemical variation encompassed by diagenesis is from 0 - 200 degrees C, 1 - 2000 bars, and water compositions from fresh to hypersaline brine (Blatt I 1979). Diagenetic processes that occurred in the Jordan Sandstone include authigenesis, cementation, compaction, dissolution, replacement, recrystallization, and the formation of concretions. Diagenetic characteristics of 112 Jordan Sandstone thin sections were petrographically examined. Diagenetic mineralogy and the paragenetic sequence were determined for each thin section. Textural observations and estimation of relative amounts of primary and secondary porosity were also made. Discussion and interpretation of the diagenetic history occurs in Chapter VII . .MINERALOGY Authigenic minerals formed in the Jordan Sandstone include, in decreasing abundance, dolomite, calcite, potassium-feldspar, quartz, iron-oxide minerals, illite, glauconite and chlorite. Based on X-ray analysis, Wegrzyn 95 (1973) and Kapchinske (1980) concluded that illite is by far the predominant clay mineral but very minor amounts of kaolinite and mixed-layer clay minerals may also occur. Relative abundances of authigenic minerals in this study are included in Tables 2, 3, and 5. Dolomite occurs in 63 of the 112 specimens examined. Dolomite abundance varies stratigraphically, between members of the Jordan Sandstone, and laterally, between measured sections. Large stratigraphic variations are typified by I mean dolomite abundances of 32, 9, and 57% of total rock volumes in the Norwalk, Van Oser, and Sunset Point (Coon Valley) Members, respectively. Lateral variations are more difficult to generalize; dolomite is most abundant in the most southern measured sections of Norwalk strata but distribution in the Sunset Point (Coon Valley) Member is relatively uniform. In Van Oser strata, distribution is erratic. Morphologically, most Norwalk and Van Oser Member dolomite occurs as distinctive subhedral or euhedral rhombohedrons. However, in many Sunset Point (Coon Valley) and in some Norwalk Member specimens, much or all of the dolomite may occur with anhedral morphology and is typically more finely crystalline than subhedral or euhedral dolomite. Large variation in dolomite morphology may also occur within individual specimens, most corrunonly in Sunset Point (Coon Valley) specimens. 96 Calcite occurs in of the 112 specimens examined. Stratigraphic and lateral distribution of calcite within and between measured sections is erratic; two Norwalk specimens contain greater than 1% calcite, 15 Van Oser specimens contain a mean of 23% calcite and 12 Sunset Point (Coon I \ Valley) specimens contain a mean of 9% calcite. Calcite is I most abundant in the most southern measured sections. Morphologically, the calcite typically occurs as anhedral and subhedral spar crystals. Calcite spar crystals are commonly large enough to enclose several elastic grains. Authigenic potassium feldspar occurs in 59 of the 112 specimens examined. As with dolomite, stratigraphic variations in potassium feldspar abundance are easily recognized. Seventeen Norwalk specimens contain a mean of 10% authigenic potassium feldspar, 22 Van Oser specimens contain a mean of 2.5% authigenic potassium feldspar, and 16 Sunset Point (Coon Valley) specimens contain a mean of 5% authigenic potassium feldspar. Morphologically, most of the authigenic potassium feldspar occurs as epitaxial euhedral overgrowths on detrital feldspar cores (Figure However, euhedral or subhedral authigenic potassium feldspar may also occur without a recognizable core. Authigenic quartz, as overgrowths, occurs in 89 of the 112 specimens examined but its abundance is quite low; Norwalk, Van Oser and Sunset Point (Coon Valley) Member 97 Figure Photomicrograph of authigenic epitaxial potassium feldspar overgrowths on detrital feldspar cores CA) (sample DT-18, Norwalk Member, Section A). Field of view approximately 0.5 mm wide. Crossed nicols. Figure 41. Photomicrograph of complete cementation by quartz (sample DT-351, Van Oser Member, Section G). Field of view approximately 0.5 nun wide. Crossed nicols. 98 samples contain, respectively, means of approximately 1.0, 2.5, and 2.0% authigenic quartz. Petrographically identifiable quartz overgrowths are relatively rare in all but a few Van Oser and Sunset Point (Coon Valley) Member \ samples. Lateral trends in authigenic quartz abundance were \ not identified but one anomalous sample from a measured section in the Minnesota River Valley (Section G) was fully cemented by quartz of total sample volume) (Figure The authigenic quartz typically occurs as syntaxial overgrowths around detrital quartz grains (Figure or at contacts between detrital quartz grains. Iron-oxide minerals occur in at least trace amounts in all the samples examined. Little stratigraphic or lateral variation in iron-oxide abundance occurs; mean abundance is approximately 2% throughout the formation and variations between measured sections are generally small. However, high abundances of iron-oxide can occur locally (Figure and in most locations, even small amounts give the sandstones a typically orange-brown color. Well developed liesegang banding (Figure occurs at one location (Section A) • Illite occurs in most of the specimens examined but due to its small grain-size and low abundance it is present in only 18 of the 112 modal determinations. Only 9 of the Jordan samples examined, all from the Sunset Point (Coon 99 Figure Photomicrograph of syntaxial quartz overgrowths (sample DT-37, Van Oser Member, Section A). Note hematite (A), subhedral morphology of quartz overgrowths (B). Field of view approximately 0.5 mm wide. Plane polarized light. Porosity stained blue. 100 Figure Photomicrograph of iron-oxide cernentation (A)(sarnple DT-172, Van Oser Member, Section C). Field of view approximately 2.5 mm wide. Plane polarized light. Porosity stained blue. Figure Exposure of liesegang banding in Van Oser Member (Section A). Hammer is cm long. Note irregular calcite cernentation and induration (A). 101 Valley) Member, contain greater than trace amounts of illite. Glauconite occurs in 7 of the 112 samples examined, 2 from the Norwalk Member and 5 from the Sunset Point (Coon Valley) Member. The glauconite only occurs in trace amounts and typically exhibits the form of a rounded grain or pellet. Chlorite cement occurs in 2 of the 112 samples examined, both of which are from the Sunset Point (Coon Valley) Member. Cementation Seqµence Detailed petrographic examination determined the order of the cementation sequence in 112 Jordan Sandstone samples. Generalized cementation (paragenetic) sequences observed are presented in Figure Stratigraphic and lateral variations in the sequences are relatively minor; typically the main differences are in the abundances of carbonate or detrital potassium feldspar. The presence of authigenic chlorite in two of the 112 samples examined represents the most anomalous variation. Although it is possible to identify as many as 9 distinct stages in some cementation sequences, there typically is petrographic evidence for only to 6 stages. Detailed examination of samples using scanning electron microscopy may enable cementation events to be further subdivided. 102 PARAGENETIC SEQUENCE 1. K-SPAR OVERGROWTHS, MINOR QUARTZ OVERGROWTHS 2. HEMATITE & ILUTE 3. QUARTZ OVERGROWTHS 4. DOLOMITE/DOLOMITIZATION 5. DISSOLUTION OF K-SPAR, DISSOLUTION OF DOLOMITE 6. CALCITE CEMENTATION, . .. .. _ .. ... REPLACEMENT OF QUARTZ & K-SPAR BY CALCITE 7. DISSOLUTION OF CALCITE 8. HEMATITE & ILLITE Figure Generalized paragenetic sequence in the Jordan Sandstone. 103 TEXTURE Eleven primary diagenetic textures were identified in samples of the Jordan Sandstone. Four of these characteristic textures result from replacement processes which did not reach completion; they include (1) irregular embayed or "corroded" contacts between cement and detrital grains, (2) disruption of the original margin of a detrital grain by planar crystal faces of the replacement mineral, (3) ghosted outlines highlighted by impurities of the original mineral, and (4) authigenic minerals hosting inclusions of the precursor mineral. Poikilotopic textures (see Bates and Jackson 1980, page 486), and two discordant textures (concretions and cementation fronts) were also observed. The most basic primary diagenetic textures, pore- filling, pore-lining, fracture-filling and fracture-lining, occur frequently. Irregular embayed or "corroded" contacts occur frequently in specimens containing calcite. In the Jordan Sandstone these contacts result from the incomplete replacement of quartz (Figure 46), potassium feldspar, and dolomite by calcite. This replacement texture is very common in Jordan strata. Disruption of the original margin of a detrital grain by planar crystal faces of a replacement mineral occurs in 104 Figure Photomicrograph of calcite cement CA> replacing quartz grain CB) (sample DT-21, Van Oser Member, Section A). Field of view approximately 2.5 mm wide. Crossed nicols. 105 some specimens containing dolomite. Typically, dolomite replaces quartz and potassium feldspar. Ghosted outlines of detrital minerals occur in some specimens containing large amounts of calcite cement. Typically, calcite replaces quartz and less frequently, potassium feldspar grains in Jordan strata. Ghosted grain outlines are commonly associated with poikilotopic textures in Jordan strata. Poikilotopic textures occur frequently in specimens cemented by calcite. Typically large crystals of calcite enclose several entire detrital quartz or potassium feldspar grains (see Bates and Jackson 1980, p. Authigenic minerals hosting inclusions of the precursor mineral occur in some Jordan specimens containing large amounts of calcite or dolomite. Inclusions of quartz, potassium feldspar and iron-oxides may occur in the authigenic calcite or dolomite. Discordant textures, resulting from the formation of concretions and cementation fronts, are most common in Jordan strata containing abundant carbonate. Changes in dolomite morphology and crystal size are common. Calcite concretions may occur in otherwise highly porous sandstone. Pore-filling, pore-lining, fracture-filling and fracture-lining textures occur very frequently in Jordan strata. Fracture-filling and fracture-lining textures are common in dolomite specimens of the Sunset Point (Coon 106 Valley) Member. Pore-filling and pore-lining textures are common in elastic specimens. The authigenic minerals associated with these textures are calcite, dolomite, iron- oxides, illite and, less commonly, quartz and chlorite. To document the effects and relative amounts of any compaction in Jordan strata, the type and frequency of grain - to - grain contacts was determined for all elastic specimens. Four basic qualitative types (see Figure 29) of contacts were distinguished: (1) point, (2) straight, (3) concavo-convex, and sutured. Relative abundance of types of contacts was visually estimated. By far the majority of grain - to - grain contacts in both the Norwalk and Van Oser Members are point and long contacts. Relatively few concavo-convex contacts occur. No sutured contacts were observed. For example, at one location (section A) the visual estimates of contacts averaged 37% point contacts, straight contacts and 21% concavo-convex contacts for Norwalk specimens. The estimates averaged 51% point contacts, 37% straight contacts and 12% concavo-convex contacts for Van Oser specimens. Clearly, the effects of compaction, which would have resulted in more concavo-convex contacts, have not been significant. 107 Porosity Clastic rocks of the Jordan Sandstone are highly porous. Porosity accounts for 0 - of total rock volume in the Norwalk and Van Oser Member specimens examined (see Tables 2 and 3). Norwalk Member specimens have a mean porosity of 15%. Van Oser Member specimens have a mean porosity of 20%. Although carbonate-rich, porosity in 5 Sunset Point (Coon Valley) Member specimens still accounted for 15 to 26% of total sample volumes. As noted by Blatt and others (1980, p. the maxi.mum possible primary porosity in well sorted, uncemented and uncompacted sands is Despite having undergone varying degrees of cementation and moderate compaction the porosity of many Jordan specimens approaches 30% of total sample volume. These high porosities in a relatively old sandstone such as the Jordan leads to the suspicion that the amount of porosity may have been enhanced during diagenesis. Careful petrographic examination does, in fact, reveal a significant amount of secondary porosity in the Jordan Sandstone. Secondary Porosity Most secondary porosity closely resembles or exactly mimics primary porosity (Schmidt and McDonald 1979b). Although Shanmugam (1985) provided an elaborate set of 20 criteria for recognition of secondary porosity, the eight basic petrographic criteria identified by Schmidt and 108 McDonald (1979b) were suitable for the observations made in this study. These petrographic criteria are (1) partial dissolution, (2) molds, (3) inhomogeneity of packing, oversized pores, (5) elongate pores, (6) corroded grain margins, (7) intraconstituent pores, and (8) fractured grains. In the Jordan Sandstone the most easily recognized secondary porosity is the partial dissolution of potassium feldspar (Figure and dolomite (Figure along cleavage planes (honey-combed grains). Inhomogeneity of packing, oversized pores, "floating" grains and elongate pores are other results of porosity enhancement recognized in Jordan specimens. Corroded grains, unless dissolved along cleavage planes, are often difficult to recognize. The only molds identified were of oolites in two samples. A small number of fractured grains were observed but were attributed to destruction during rock cutting or thin section preparation. Secondary porosity was only rarely recognized as having been significantly reduced by a later cementation event. When such reduction was observed it was always by late calcite cementation (Figure Insignificant reductions in secondary porosity were observed to have been the result of late pore-lining by iron-oxides or illite. 109 Figure Photomicrograph of porosity enhancement by dissolution of potassium feldspar (sample DT- Norwalk Member, Section C). Field of view approximately 0.5 mm wide. Plane polarized light. Feldspar stained yellow. Porosity stained blue. Figure Photomicrograph of porosity enhancement by dissolution of dolomite (sample DT-103, Van Oser Member, Section B). Field of view approximately 0.5 mm wide. Plane polarized light. Porosity stained blue. Feldspar stained yellow. 110 Figure 49. Photomicrograph of secondary porosity reduction by late calcite cementation (sample DT-65, Sunset Point (Coon Valley) Member, Section A). Note brown crystalline dolomite CA), quartz grains CB), and calcite cement CC), stained red. Width of view approximately 5.0 mm wide. Plane- polarized light. 111 Unfortunately, the ratio of porosity to primary porosity in Jordan Sandstone specimens could not be quantified with any degree of accuracy. 112 Chapter VII INTERPRETATION AND DISCUSSION ENVIRONMENTS OF DEPOSITION Recent workers (Wegrzyn 1973, Adams 1978, Byers 1978, Dott 1978, Odom and Ostrom 1978, Porter 1978, Kapchinske 1980) concluded that the lithological members of the Jordan Sandstone in Wisconsin were deposited exclusively in various marine environments. Wegrzyn (1973) concluded the Norwalk Member is a deposit of the 'nondepositional shelf sediment zone' as described by Ostrom (1970). Modern analogues to rocks of this zone are the alternating beds of sand and finer sediments of the northwest Gulf of Mexico as described by Van Andel and Curray (1960). Wegrzyn interpreted the Van Oser Member as a deposit of the littoral zone and suggested that it was originally made up of 'a system of beaches, barriers, spits and nearshore zones where waves and longshore currents winnowed and redistributed the sediment' (Wegrzyn 1973, p. 117). Water depth was suggested to be less than 6 fathoms. Wegrzyn suggested that the lower portions of the Sunset Point Member were deposited in the 'nondepositional shelf sediment zone' and the upper portions were deposited in a zone seaward of the 'nondepositional zone'. The variations characteristic of the Sunset Point were attributed by Wegrzyn (p. 120) 'to an intermingling with neighboring sediment zones as the result of major wave 113 and current activity, indicating a lack of a stable environment.' Porter (1978) studied the Norwalk Member exclusively and suggested it was most likely composed of offshore and lower to middle shoreface deposits as defined by Harms and others (1975, p. 82) and Reineck and Singh (1975, p. 285). Porter also suggested inter-tidal sandf lat and upper shoreface to foreshore, or swash zone, as less likely but alternative depositional environments for Norwalk strata. Dott (1978) concluded that Van Oser Member rocks were probably deposited in the litteral environment and exhibit many characteristics of the sandy subtidal shoref ace environment as defined by Harms and others (1975). Dott noted that the Norwalk Member was most likely deposited in deeper water than the Van Oser Member. Dott suggested that storm and tidal processes greatly influenced deposition of Jordan strata. Adams (1978) interpreted the rocks of the Coon Valley Member (which he included in the lower Oneota Dolomite) as representing a transition from litteral sand bar deposition to intertidal and supratidal deposition. Odom and Ostrom (1978) concluded the Norwalk Member was deposited in a mostly subtidal lagoon environment and the Van Oser Member was deposited in a littoral environment influenced by tides. They also interpreted the Coon Valley 114 Member as having resulted from subtidal carbonate shelf deposition and local littoral and carbonate shelf intertidal deposition. Byers (1978) suggested a tentative interpretation of the Norwalk Member as subtidal and lower intertidal regions of a larger tidal flat. Reineck and Singh (1973) referred to this lower intertidal zone as the sand flat. Kapchinske (1980) concluded the Van Oser Member was most likely deposited in the agitated waters of the upper shoreface. Kapchinske also concluded the sandstones of the Coon Valley Member were deposited in the lower shoreface to off shore zones and that the upper portion of the Coon Valley represents a complex upward-shoaling succession deposited on a carbonate platform. The upward-shoaling successions locally include stromatolites interpreted to be representative of tidal zone deposition. The observation of length-slow chalcedony in Coon Valley mudstones was interpreted to be evidence of local evaporite development. All of the interpretations of depositional environment noted above fit into four major categories: elastic tidal flat environments, barrier island and strand plain environments, shelf and shallow marine sand environments and shallow-water carbonate environments. However, shelf and shallow marine sand environments and shallow-water carbonate envirnoments are complex and not easily interpreted. Each 115 of the four major environments are briefly commented on below. Weimer and others (1982) reviewed the characteristics and processes of elastic tidal flat environments. Although tidal flats are fairly well understood, they may exhibit considerable variation depending on sediment types and availability, presence or absence of vegetation, tidal range and coastal energy and morphology. As noted by Weimer and others (1982) a cautious approach is essential when comparing modern tidal flats to ancient deposits because the facies most likely to be preserved (channel-fill sediments) are the least obvious when looking at the surf ace of a modern tidal flat. Probably no other coastal facies is so potentially misleading during interpretation of ancient rocks (Weimer and others 1982). The characteristics and processes of barrier island and strand plain environments have been reviewed by Elliott (1978), Harms and others (1982), Mccubbin (1982) and Reinson Barrier island and strand plain environments show some significant variations depending mainly on local wave conditions, tidal range, sediment supply and relative sea- level changes. As noted by Reinson there was an overwhelming preference in most pre-1970 elastic shoreline studies for the use of just one barrier island model (the well-defined Galveston Island model). However, the 116 prograding Galveston Island model is only one of at least three distinct stratigraphic barrier island models. Shelf and shallow marine sand environments have been reviewed by Johnson (1978), Bouma and others (1982), Harms and others (1982), Walker and Tillman (1985). Shelf and shallow marine sand environments are not well understood. Walker noted that shallow marine systems are probably the most complex of the major elastic depositional environments and ideas relating to shallow marine systems are in a state of flux. Bouma and others (1982) noted that for shelf deposits it is impossible to present a set of diagnostic structures and textures. Tillman (1985) observed there is a wide spectrl,lrn of shelf sandstone types and Miall p. 291) noted that the interaction of waves, tides and storms in moving sediment and generating bedforms on elastic shelves is still poorly understood. Harms and others (1982) commented that lacking clear evidence of shoreline positions or sea-levels, interpretation in ancient shallow marine sequences is difficult and elusive. Shallow-water carbonate environments have been reviewed by Sellwood (1978), Enos (1983), Inden and Moore (1983), Shinn (1983), Wilson and Jordan (1983), and James Shallow-water carbonate environments are complex. As noted by Miall p. 292) carbonate sedimentation depends on a 117 wide variety of depositional controls including temperature, carbonate saturation, salinity, water depth, nature of water currents, light penetration, water turbidity, nature of sediment substrate and rates of relative sea level change. In addition to difficulties associated with the interpretation of ancient deposits in the four envirorunents discussed above, Dott (1978) and Dott and Batten (1988) noted several important problems dealing specifically with the interpretation of highly mature, sheet-like Cambrian sandstones: (1) the extraordinary lack of shale associated with these sandstones prevents the formation of many diagnostic sedimentary structures and sequences and also complicates direct comparison of ancient and modern facies, (2) the dearth of fossils and the low fossil diversity typical of these sandstones greatly restricts the amount of environmental evidence commonly available, (3) the laterally extensive sheet geometry (thousands of Jan2) of these sandstones has no modern analogues and is difficult to explain in terms of modern shelf processes, the very high maturity and associated textural homogeneity of these sandstones commonly results in a relatively small suite of sedimentary structures, and (5) the carbonate rocks associated with these sandstones are commonly highly dolomitized and many key diagnostic features are destroyed. As noted by Dott (1978) careful attention to 118 sedimentological and paleontological details is required if the depositional environments of these sandstones are to be understood with any sophistication. Careful examination of the Jordan Sandstone in Minnesota reveals numerous useful characteristics described in detail above (Chapters II to V). These characteristics include physical and biogenic sedimentary structures, lithological associations, mineralogical composition, paleocurrents, fossil content and sedimentary textures. They may provide either evidence of specific environmental conditions during deposition or important constraints on the range of possible conditions. Norwalk Member In Minnesota, the two most abundant sedimentary structures observed in the very fine-grained sandstones characteristic of the Norwalk Member are mottled and homogeneous massive bedding with discontinuous and continuous planar parallel bedding geometry. The other abundant physical and biogenic sedimentary structures are planar parallel lamination, trough and tabular cross- stratif ication, silt and mud bedding partings, and the trace fossils Arencolites, Skolithus, and Less common structures are flat-pebble rip-up clasts, low-angle cross- stratification and symmetrical ripple-marks. 119 Mottled bedding is typically interpreted as the result of sediment reworking by infauna! deposit feeders (Frey and Howard, 1972). Frey and Pemberton (1984) noted that deposit feeders do not proliferate in turbulent-water conditions and are best suited to quiet-water environments. Mottled bedding is also associated with a higher intensity of bioturbation than is the occurrence of distinctive burrows (Howard 1975, Rhoads 1975). In addition it is likely that mottled bedding is associated with high nutrient deposit concentrations and a low rate of sedimentation. Homogeneous (massive) bedding, as noted by Collinson and Thompson (1982, p. 100) may result from either depositional conditions or from destruction of original lamination. Lamination destruction can occur during intense bioturbation or from liquefaction and movement of the sediment. Unlaminated sediments can result from rapid deposition from suspension such as during deceleration of a heavy sediment load. In the Norwalk Member, homogeneous bedding commonly contains isolated zones of burrowing, mottling, and discontinuous bedding or lamination. These features suggest that the most probable origin of homogeneous bedding in Norwalk strata is the destruction of lamination during intense bioturbation. Water energies, sedimentation rates and nutrient deposit abundances are 120 suggested to be similar to those associated with mottled bedding. Planar parallel lamination in very fine and fine sands may form by two processes: deposition from suspension onto a planar substrate, or deposition from traction transport at relatively high mean water flow velocities (60-120 cm/second) (Harms and others 1982). Coarser sediment cannot be spread in suspension for significant distances except by currents with enough velocity to mold the bed by traction during deposition (Figure 50). Planar parallel lamination occurs in every measured section of Norwalk strata but is not highly abundant at any location. Most Norwalk Member planar parallel lamination is associated with massive (homogeneous) or mottled bedding but some planar parallel lamination is associated with flat-pebble rip-up clasts and cross-stratification. This suggests that most of the planar parallel lamination formed by deposition from suspension in mean water flow velocities less than 20 cm/second (see Figure but some lamination formed by deposition in upper plane bed conditions (mean water flow velocities of 60-120 cm/second). Trough and tabular cross-stratification set thicknesses typical of the Norwalk Member (10 to 20 cm), are formed at relatively high (60 - 100 cm/sec.) mean water flow velocities (Harms and others 1982). These cross-stratified 121 200 ANTIOUNES 150 u --CD ....., 100 RIPPLES E u eo -> t: Trough (..) 60 0 ...... ______. __.,,,,,... ---- _... --- ..J -- w :> 0 40 SMALL RIPPLES ..J LL. 30 ----- NO MOVEMENT 20 0.1 02 04 06 0.8 lO 1.5 2.0 SEDIMENT SIZE (mm) Figure 50. Size-velocity diagram for conunon elastic sedimentary bedforrns. (Modified after Harms and others 1982). 122 sets form only where the sediment is at least fine sand- sized. As with planar parallel lamination, trough and tabular cross-stratification occur in the majority of measured sections but are not highly abundant at any location. Silt and mud bedding partings may be deposited only if water flow velocities are very slow, typically less than 20 cm/second (see Figure Silt and mud bedding partings are moderately abundant in the Norwalk Member but typically they are less than 1 mm thick and represent a tiny fraction of the member. Planolites and Arencolites are typical of the Gruziana ichnofacies. The Cruziana ichnofacies is generally associated with medium- to low-energy conditions and substrates ranging from well-sorted silts and sands to poorly sorted sediments that have undergone biological reworking (Ekdale and others As noted by Frey and Seilacher (1980) the Cruziana ichnofacies is most characteristic of subtidal zones below fair-weather base but above storm wave base. Both suspension and deposit feeders inhabit such zones and intense feeding activity may obliterate primary sedimentary structures (Ekdale and others Arencolites, like is a suspension feeder trace and is more likely to be associated with higher-energy levels than Planolites which is a deposit feeder trace. 123 Skolitbos is characteristically associated with high- energy conditions that produce well-sorted arenaceous substrates (Seilacher 1967). The depositional environments typical of such conditions include the foreshore and shoreface zones of beaches, bars and spits (Howard 1972, 1975); however, these conditions may also be present in higher-energy parts of tidal flats, tidal deltas, estuarine point bars, and occasionally in submarine canyons and deep- sea fans (Ekdale and others As noted by Pemberton and Frey (1983, Skolithos also occurs in storm deposits of medium- to low-energy environments. Low-angle cross-stratification occurs in two forms: Cl) swash cross-stratification or (2) hurnmocky_cross- stratification (Figure 51). As noted by Harms and others (1982), swash cross-stratification may occur in the swash zone of the shoreline foreshore but the origin of hummocky cross-stratification is still speculative. Duke (1985) reviewed information on hummocky cross-stratification and concluded that most occurrences formed in shallow marine settings, in water depths on the order of metres to a few tens of metres and were produced by wave-generated oscillatory or multidirectional bottom flows with periods of the order of 1 - 20 seconds. Duke (1985) agreed with the generalization, advanced by Harms and others (1975), suggesting that 'preserved' examples of hummocky cross- 124 ...·: ·.: ::::: :::: :·:::: :::::.::: :·::::·: ::::: ;; :·:. ·::: :·. ·-· ...... HUMMOCKY CROSS-STRATIFICATION 2-10° ·' · _.:: :·'" ... .. • .•: ...... u: .. , .. ·...... , ,• ...... -- . ;;_: _": ...... ··. •·· .. ..· .. , ; ...... . . . : .'· .. ·... .· ·-·::·.. ·'. .. ·. :·-.::.:">.. .. ·.. .. ::: . SWASH CROSS - STRATIFICATION Figure 51. Block diagrams illustrating hummocky cross- stratif ication and swash cross-stratification. (From Harms and others 1982}. 125 stratification are primarily formed by processes involving storm waves in water depths below tidal and f airweather-wave influence and above storm wave base. Klein and Marsaglia (1987) and Swift and Nummedal (1987) argued against the above generalization but Duke (1987) convincingly defended the conclusions of his 1985 review. In Norwalk strata, low- angle cross-stratification occurs in two of the Minnesota measured sections but was positively identified as hummocky cross-stratification at only one location (section H). Prominent flat-pebble rip-up clast horizons within finer-grained sands indicate episodes of exceptional scouring (Dott 1978). Symmetrical ripple profiles, although commonly produced by wave action, should not be considered indicative of wave activity unless detailed ripple indices measurements are conclusive of symmetry (Collinson and Thompson 1982, p. 59- 61). The ripple index for the single occurrence of ripples observed in the Norwalk Member is non-discriminatory so a genetic interpretation is not possible. Several conclusions can be made regarding the paleohydrological characteristics of the Norwalk Member as described above: (1) A relatively low-energy paleohydrological regime was predominant. As noted above, the abundant mottled and homogeneous bedding in fine-grained sandstones so 126 characteristic of Norwalk strata are typical of quiet-water conditions in which deposit feeders may proliferate. The occurrence of Planolites and preserved silt and mud partings this conclusion. (2) A moderate to high-energy paleohydrological regime characterizes minor portions of Norwalk strata. As noted above, trough and tabular cross-stratification and associated planar parallel lamination are typical of higher energy conditions. The occurrence of Arencolites and Skolitbos supports this conclusion. (3) Episodic high-energy paleohydrological events characterize random portions of Norwalk strata. As noted above, the several flat-pebble rip-up clast horizons are typical of scouring episodes and the hummocky cross- stratification is most probably of storm process origin. The predominantly homogeneous texture of the Norwalk Member suggests that the general hydrological regime remained unchanged for long periods of time. Inferred storm events failed to transport sediment larger than fine-grain sized material into the Norwalk depositional environment. Multiple fining or coarsening-upward sequences do not occur. Coarsening of sediments near the top of the Norwalk Member at three locations is associated more with the relatively rapid change to Van Oser Member depositional conditions than 127 to a sustained rate of change within the hydrological regime. Other noteworthy conclusions and observations include: (5) The abundance of mottled bedding, homogeneous bedding, Skolithos, Arencolites, and Planolites suggests an entirely marine depositional environment for Norwalk strata. Evidence of emergence, such as dessication cracks, was not observed. (6) The absence of tidal channels, flaser bedding and herringbone cross-bedding points away from but does not . exclude tidal flat or intertidal environments. Although the lack of flaser bedding may be associated with a general dearth of shale within the environment, the total absence of recognized tidal channels is harder to explain. As described above, the characteristics of the Norwalk Member in Minnesota are not 'diagnostic' of a particular depositional environment. However, the most probable depositional environment is the offshore to lower shoreface (Figure 52) as defined by Harms and others (1982). Van Oser Member In Minnesota, the most abundant sedimentary structures present in the Van Oser Member sandstone are trough cross- stratif ication and continuous and discontinuous planar parallel stratification. Other abundant physical and biogenic sedimentary structures are tabular cross- 128 Strand plain, I 1 alluvial pla in1 Backshore Foreshore Shoreface 1 Offshore lagoon, or older 1 rocks I .- Swash, surf, breaker zone -t- MHWL -::: ··: ·.··.:: ,: .. .. · .·.·.. :s· ·I: ..-.··. ;··: :. ... : :" :·:· :. :·. :·,-::· .-::.·.: ... :: ... ··.. ------.,_._..,. ___ :_: ·.·.: · .-...... ··r·· · :.·: ::· ·: erm · · · · ·· . . . -. ._ ._ .. .- · .. : ·:· _ .. Dunes Runnel Ridges Longshore · · ·"';-:.....:...:. : & Runnels Bar Figure 52. Shoreline profile and terminology of sandy mainland coasts. (Modified after Harms and others 1982). 129 stratification, flat-pebble rip-up clast horizons, homogeneous (massive) bedding, and the trace fossils Arencolites and Skolitbos. There are several occurrences of herringbone cross-stratification but low-angle cross- 5tratification, assymetrical ripple marks, green silt and mud partings and the trace fossils Planolites occur infrequently. Trough cross-stratification set thicknesses typical of the Van Oser Member (10-60 cm) are formed at relatively high (55-120 cm/sec) mean water flow velocities (Harms and others 1982). Tabular cross-stratification set thicknesses (up to 120 cm) typical of the Van Oser Member are formed at slightly lower cm/sec) mean water flow velocities (Harms and others 1982). Planar parallel bedding in the medium-grained sands typical of the Van Oser Member forms at high (60-130 cm/sec) mean water flow velocities (Harms and others 1982). Herringbone cross-stratification is most likely to form in tidally influenced environments and results from reversals in current direction (Collinson and Thompson 1982, p. 81). The absence of herringbone cross-stratification does not necessarily indicate the absence of tidal currents. Assymetrical ripple marks typically result from currents flowing in one direction only (Collinson and Thompson 1982, p. 59). 130 The of formation attributed to flat-pebble rip-up clast horizons, homogeneous bedding, low-angle cross- stratification, silt and mud partings, Arencolites, Skolithos and Planolites are discussed above for their occurrences in Norwalk strata. Several conclusions can be made with respect to the paleohydrological characteristics of the Van Oser Member as described above: (1) A relatively high-energy paleohydrological regime was predominant. As noted above, the abundant trough and tabular cross-stratification and planar parallel bedding require water flow velocities ranging from to 130 cm/second. The widespread occurrence of the suspension feeder traces Arencolites and Skolithos support this conclusion. (2) A low-energy paleohydrological environment characterizes very minor and local portions of Van Oser stratigraphy. As noted above, infrequent occurrences of silt and mud partings and the deposit feeder trace Planolites support this conclusion. (3) Episodic very-high energy paleohydrological events characterize random portions of Van Oser strata. As noted above, the abundant flat-pebble rip-up clast horizons are evidence of scouring events. The Van Oser Member is typically too coarse-grained to develop hummocky cross- 131 stratification. Only one location (Section E) contained a portion of fine-grained Van Oser strata with possible hummocky cross-stratification. The paleohydrological regime was probably influenced, at least locally, by relatively strong tidal currents. Van Oser Member paleocurrent measurements (Chapter IV) resulted in two bimodal-bipolar rose diagrams, one weakly bimodal-bipolar rose diagram, two trimodal rose diagrams and two ambiguous rose diagrams. As noted above, the Van Oser Member contains several occurrences of herringbone cross-stratification confirmed by paleocurrent measurements. (5) As inferred for the Norwalk Member, the relatively homogeneous texture of the Van Oser Member suggests that the general hydrogeological regime remained unchanged for long periods of time. There are relatively few changes in grain- size and they appear to be at random. Multiple fining or coarsening-upward sequences do not occur. As described above, the characteristics of the Van Oser Member in Minnesota do not permit a sophisticated interpretation of the depositional environment. However, the characteristics of Van Oser strata are most typical of the upper and middle shoref ace environments as defined by Harms and others (1982). 132 The conformable succession of upper and middle shoref ace environments of the Van Oser Member over the lower shoref ace and off shore environments of the Norwalk member indicates that a regression occurred during deposition of these sediments. Characteristics typical of the aeolian and braided fluvial deposition described by Dott and others (1986) for portions of the Cambrian Wonewoc and Ordovician St. Peter sandstones in Wisconsin, were not observed in Van Oser strata in Minnesota. Waukon Member As noted above (Chapters II and V), Odom and Ostrom (1978) suggested that the very fine-grained strata occurring locally within the Van Oser Member be given member status and named Waukon. Porter (1978) proposed that interstratif ication of Norwalk and Van Oser strata is a more appropriate explanation than the occurrence of a separate, locally present lithic member within the Van Oser Member. In Minnesota the physical and biogenic sedimentary structures, texture and composition of the very fine-grained 'Waukon' strata are typically the same as those of the Norwalk Member. In Minnesota 'Waukon' strata occur in at least two locations (Sections A and D) and, as noted by Odom and Ostrom (1978), at outcrops across southwestern Wisconsin and northeastern Iowa. Porter (1978) suggested it is not 133 appropriate to give the very fine-grained 'Waukon' strata member status in the Jordan Sandstone because 'Waukon' strata were deposited in the same depositional environment as the Norwalk Member and had limited geographic extent. However, as illustrated on Plates 1 and 2, 'Waukon' strata may have a geographic distribution in Minnesota extending 60 km in a north-south direction and possibly as far as 150 km. Depending on the interpretation of the geological history of the Jordan Sandstone, 'Waukon' strata in Minnesota may have been deposited as either: (1) a large- scale interstratif ication of the Van Oser Member and the underlying Norwalk Member or (2) a 'lens'-shaped deposit separate from the Norwalk Member. As noted by the North American Commission on Stratigraphic Nomenclature (1983, pages 856 and 857) it may be appropriate to formally name a separate sandstone lens but tongues of sandstones are most appropriately distinguished informally. Since large-scale interstratification of the Van Oser Member with the underlying Norwalk Member (Plate 2) may have required a corresponding variation in subsidence rate, sediment supply rate, or rate of eustatic sea level change, and deposition of 'Waukon' strata as a separate lens (Plate 1) may have required less complicated explanations (such as the development of a slight structural shelf depression), it seems more probable that Waukon strata form a large lens- 134 shaped deposit and should maintain their status as a separate member of the Jordan Sandstone. However the most simple explanation is not always correct. Accordingly, new evidence in the form of appropriately located measured sections of the Jordan Sandstone, may show that large-scale interstratif ication of the Van Oser Member with the Norwalk Member is the better explanation. It should also be noted that although Norwalk and Waukon strata are interpreted to have the same depositional environments, inferred depositional environments and geological history have no place in the definition of a lithostratigraphic unit (North .American Commission on Stratigraphic Nomenclature 1983, page 856). Sunset Point (Coon Valley) Member Unlike the Norwalk and Van Oser Members there are no one or two types of predominant sedimentary structures characteristic of the Sunset Point (Coon Valley) Member in Minnesota. The diversity of sedimentary structures reflects the heterogeneous and transitional nature of this member. The most abundant physical and biogenic sedimentary structures are: continuous and discontinuous planar parallel stratification, trough cross-stratification, tabular cross-stratification, flat-pebble rip-up clasts, very thinly-bedded to thinly laminated green silt and mud horizons, silt and mud bedding partings, homogeneous 135 (massive) bedding, mottled bedding and the trace fossils Arencolites, Skolithos and Planolites. Less common features are laterally linked hemispheroid stromatolites, oolite beds, and apparent (paleocurrent measurements not possible due to two-dimensional exposure) herringbone cross- stratification. With the exception of laterally linked hemispheroid stromatolites and oolite beds, the processes of formation attributed to all of the above physical and biogenic sedimentary structures are discussed above for their occurrences in either Norwalk or Van Oser strata. Oolite beds in modern sediments occur only where strong bottom currents provide periodic transport and repeated burial and exhumation of sedimentary particles (Blatt and others 1980, p. Such currents are characteristic of tidal settings. As noted by Adams (1978) a water depth of two to ten feet is consistant with oolite formation in modern settings. Laterally linked hemispheroid stromatolites have been suggested to form predominantly in protected intertidal mud flats where wave action is not significant and algal mats can grow between hemispheroids (Blatt and others 1980, p. 136 The following conclusions can be made with respect to the paleohydrological chracteristics of the Sunset Point (Coon Valley) Member: (1) Although no specific sedimentary structure is predominant in Sunset Point (Coon Valley) strata, the collective suite of structures suggests a tidal paleohydrological regime. As noted above, the oolitic beds, stromatolites and apparent herringbone cross-stratification are'typical of intertidal carbonate environments. The occurrence of trough cross-stratification and flat-pebble rip-up clast ('intraclast') horizons support this conclusion. (2) The paleohydrological regime was generally of a lower energy than that of the Van Oser Member. The typically smaller grain-size, occurrence of mottled bedding, silt and mud bedding partings, very thinly-bedded to thinly laminated green silt and mud horizons, and the trace fossil planolites in the Sunset Point (Coon Valley) Member support this conclusion. (3) A moderate to high-energy paleohydrologic regime characterizes some portions of Sunset Point (Coon Valley) strata. As noted above, trough and tabular cross- stratification and associated planar parallel lamination are typical of higher energy conditions. The occurrences of Arencolites and Skolithos support this conclusion. 137 The paleohydrological regime was in a state of transition. The heterogeneous nature of the Sunset Point (Coon Valley) Member, its conformable stratigraphic relationships with the underlying quartz arenites of the Van Oser Member and the overlying carbonates of the Oneota Dolomite, the upward stratigraphic increase in carbonate content and the upward stratigraphic decrease in grain-size support this conclusion. Penecontemporaneous with this transition from siliciclastic sedimentation to carbonate sedimentation was local shoaling-upward, as suggested by the occurrence of oolite beds and stromatolites (Sections A and B) in the uppermost Sunset Point (Coon Valley) strata. As described above, the heterogeneous characteristics of the Sunset Point (Coon Valley) Member in Minnesota are most typical of deposition in a tide-influenced Cat least locally) shallow marine environment transitional from the siliciclastic upper and middle shoref ace environments of the Van Oser Member to locally shoaling-upward carbonate environments most probably associated with a prograding offshore platform or, as described by Pratt and James (1986), development of laterally accreting and migrating tidal islands (Figure 53). Kapchinske (1980) described well developed upward-shoaling in the Coon Valley Member in Wisconsin and Adams (1978) described local supratidal deposits, including evaporite breccias, in the lower Oneota 138 ------ (Modified from Pratt Tidal island facies model. Figure 53. and James 1986). 139 Dolomite immediately overlying the Coon Valley Member in Wisconsin. The evidence of tidal deposition in shallow epeiric seas is well documented in ancient carbonate and siliciclastic rocks (Klein 1977, Klein and Ryer 1978). The occurrence of mixed siliciclastic and carbonate in rocks of the Sunset Point (Coon Valley) Member in Minnesota is consistent with deposition in an environment transitional from the siliciclastic upper and middle shoreface to environments associated with a prograding carbonate platform. Mount (1984) reviewed more than 150 modern and ancient examples of mixed shelf sediments and grouped mixing processes into four general categories: (1) puncuated mixing, (2) facies mixing, (3) .in situ mixing, and (4) source mixing. Punctuated mixing, facies mixing, and .in are illustrated in Figure 54. Source mixing is caused by uplift and erosion of carbonate source terranes and admixture of carbonate detritus with siliciclastic material. Although voluminous carbonate production does not occur under the constant influx of siliciclastic sediment, it is particularly true for mixed sediments that sedimentation typically associated with major storm events provides a mechanism for the transfer of large amounts of sediment from one facies to another. Mixing of carbonate and siliciclastic sediments by rare, high-intensity storm events is termed punctuated mixing by Mount (1984) and is 140 A) PUNCTUATED MIXING ON RIMMED PLATFORMS Landward transport of peri- Transportoftidafftatandnear- lidal carbonate sediments dur- shore siliciciastic. belt ledi· majbf storms; formation of Tr91\Sferohubtidallemgenous ments into deeper, IUbtidal sptllowlr lobes, erosion of reefs and carbonate muds onto tidal erMronments by atonn-surge- end lhoals...... _ lats by slonn tides and WllleS. «>b, wind forcing. etc/ ...... / / '' = ----·.... -·-· ----·-- t;7·£v --- **" :cz-:.;.:__ .... m p . 8) FACIES MIXING ON RIMMED PLATFORMS C) IN SITU MIXING ON RIMMED PLATFORMS Precipitation of carbonate cements. lormation of algal mats and in situ accumulation of carbonate alloc:hems and mud in siliciclastic-dominated aubtidal to inter- tidal environments. .. •• Figure S/j.. Examples of sediment mixing processes on siliciclastic-influenced carbonate platforms. (From Mount 198/j.). Similar processes occur on ramps or open shelves. 141 the most probable process of sediment mixing for Sunset Point (Coon Valley) strata. Both seaward transport of siliciclastic material from nearshore siliciclastic deposits and landward transport of carbonate sediments are possible. The autochthonous generation of carbonate material within siliciclastic sediments, termed mixing, may have occurred in Sunset Point (Coon Valley) strata but was probably of much less significance than punctuated mixing. As described above, the conformable transition from the upper and middle shoref ace environments of the Van Oser Member to the generally lower energy environments proximal to a prograding offshore carbonate platform (or development of laterally accreting and migrating tidal islands) requires either a eustatic sea level rise or constant subsidence and a stable sea level. Both of these situations result in a transgressive sequence. James (1984) advocates the term shallowing-upward to distinguish transgressive shallow water carbonate sequences which are progradational during a constant rate of subsidence and a constant sea level. The progradation of tidal flat wedges model described by James (1984) and which requires a carbonate platform source area (Figure 55), may prove useful in the depositional interpretation of the lower portions of the Oneota Dolomite which conforrnably overlie the Sunset Point (Coon Valley) Member. 142 ACCRETION OF SHALLOWING-UPWARD SEQUENCES E--TIDAL FLAT----OPEN PLATFORM - SOURCE AREA ----- . s T : ...... \ -TIDAL SOURCE -s; NO SE DIME NT AT ION > . .. . .-, ... - NEW TIDAL FLAT - _.,..>tz,__- OPEN PLATFORM - SOURCE AREA --- . .. '> . . :;-.,, , .Si:.. .. x .-·.. upward sequences can be produced by general conditions apply m the case of both ;ketch illustratmg how two shallowing- progradation of a tidal flat wedge. These eustatic and autocyct1c models. Figure 55. Shallowing-upward sequences produced by progradation of a tidal flat wedge. (From James 198L.t). 143 PROVENANCE As noted by Pettijohn and others (1973, p. 306) the of sandstone provenance typically involves three main types of evidence: (1) composition of detrital grains, (2) composition of the underlying stratigraphy, and (3) paleocurrents and paleogeography. Dickinson and Suczek (1979) and Dickinson and others (1983) observed that several provenance types, based on tectonic setting, could be distinguished using modal data of sandstone detrital composition plotted onto specialized ternary diagrams. Modal data for Jordan Sandstone detrital components are plotted in Figure 56. The provenance type distinguished for Jordan strata is, as expected by the paleogeography and the regional geology, a continental craton interior. The very high monocrystalline quartz content, the high degree of quartz grain rounding and the rare occurrence of quartz grains with multiple abraded overgrowths (Figure 57) suggest a multicyclic origin. The heavy mineral suite, restricted to rounded tourmaline, garnet and zircon grains, is also consistent with a mature multicyclic origin. The dearth of grains with low mineralogical stability supports this interpretation. Studies by Helmold (1985) and McBride (1985) demonstrated that diagenesis may significantly change provenance determinations due to dissolution of feldspar 144 TRANSITIONAL ARC . 15 50 0 Van Oser Member Mean OFL Composition ( 58 Samples ) 0 Jordan Sandstone Mean OFL Composition ( 86 Samples) Figure 56. Tectonic setting of Jordan Sandstone source area as distinguished using modal detrital data. 145 Figure 57. Photomicrograph of a multicycle quartz grain (sample DT-63, Sunset Point (Coon Valley) Member, Section A). Note multiple abraded quartz overgrowths (A). Abraded quartz overgrowths are extremely rare in the Jordan Sandstone. Field of view approximately 1.0 mm wide. Crossed nicols. 146 grains and rock fragments. However, as noted by Odom (1975, 1978) the large variation in the 8tratigraphic abundance of feldspar in Cambrian sandstones of the Upper Mississippi River Valley are not related to provenance or dissolution. Support for this conclusion includes: (1) some stratigraphic units grade laterally from coarse and medium- grained sandstbnes to very fine-grained, feldspathic 1 I sandstones, Ci>I local thin beds of very fine-grained, I I feldspathic / andstone occur within medium-grained quartzose sandstones, (3) feldspar is abundant in the very fine- grain fractions of the quartzose sandstones. The detrital feldspar was selectively abraded in sustained high energy hydrodynamic environments and then sorted and deposited in lower energy environments. The amount of feldspar in very fine-grained sandstones was further increased by diagenetic development of authigenic epitaxial overgrowths. Examination of the stratigraphy underlying the Jordan Sandstone (see Figure 3) reveals several older Upper Cambrian quartz-rich sandstones including the Mt. Simon Sandstone, the Galesville Sandstone and the Ironton Sandstone. Dott (1978) noted that the heavy mineral suite of the Jordan Sandstone is essentially identical with that of the Galesville Sandstone (see Figure 3) suggesting it may have been one of the more important sources of rnulticyclic grains. Precambrian sandstones may also have contributed 147 detritus but Dott (1978) precluded the Baraboo Quartzite in Wisconsin as a source due to its very different suite of heavy minerals. Odom (1978) also noted that Late Precambrian sediments may have been source rocks for Cambrian sandstones. As noted by Morey (1972) rocks of Early or Middle Cambrian age have not been identified in the Upper Mississippi River Valley where the Mt. Simon Sandstone of Late Cambrian age directly overlies the Hinckley Sandstone of Late Precambrian age. In addition to the Hinckley Sandstone, the Souix Quartzite and Barron Quartzite may also have contributed detrital grains ultimately deposited in the Jordan Sandstone. Radiometric age determinations indicate that detrital feldspar in the Late Cambrian sandstones was initially derived from rocks of Middle Precambrian age (2100 Ma). Unfortunately, as described in Chapter IV, paleocurrent measurements in the Jordan Sandstone of Minnesota appear to be of little help in suggesting a possible source area or even the direction of the paleoslope. However, paleocurrent measurements from the Jordan Sandstone in Wisconsin (Farkas 1960, Dalziel and Dott 1970, Michelson and Dott 1973) show that southerly vector means are regionally dominant. A general thickening of the Jordan Sandstone from north to south is consistent with a southerly paleocurrent vector 148 mean and suggests a possible southerly dipping paleoslope and northerly geographic paleosource. A southerly dipping paleoslope is also consistent with the regional setting of Paleozoic rocks in Minnesota. As noted by Webers (1972) Minnesota was the site of at least three marine transgressions during Late Cambrian and Ordovician times. Sediments were deposited in a shallow depression, which rapidly shoaled to the north between the northeast-trending Transcontinental Arch and the northwest- trending Wisconsin Arch (Figure 58). This depositional basin is known as the Hollandale Embayment of the Ancestral Forest City basin. Isopach maps CMossler 1972, 1983) of the Cambrian stratigraphy underlying the Jordan Sandstone show a pronounced thickening towards the south-central portion of the embayment. Webers (1972) suggested that the maximum transgressive shoreline was approximately parallel to the present erosional limit of Paleozoic rocks in Minnesota. In conclusion, the examination of detrital grain composition, composition of the underlying stratigraphy, paleocurrent direction and paleogeography reveals only generalized geographic and speculative stratigraphic paleosources. This should not seem surprising in light of the highly mature multicyclic composition of the Jordan Sandstone. 149 WILLISTON BASIN Figure 58. The Hollandale Embayment of the Ancestral Forest City Basin. (From Webers, 1972). 150 DIAGENETIC HISTORY As noted by Scholle and Schluger (1979), diagenesis in elastic sedimentary rocks has been, until relatively recently, one of the least adequately studied subjects within the discipline of sedimentology. Diagenetic changes in elastic sediments are the result of a wide variety of chemical, physical, biochemical and biophysical processes (Schmidt and McDonald 1979a) and may be difficult to interpret. However, as noted by Pettijohn and others (1973, p. 389) important aspects of the geological history of sedimentary basins may be determined from diagenetic evidence. As noted in Chapter VI, Jordan strata show no evidence of significant burial compaction. Chilingarian (1983) provided a thorough review of compactional diagenesis. Diagenetic processes most likely occurred under relatively low temperatures and pressures. Early diagenetic processes rather than later burial diagenetic processes, were probably predominant. Early diagenesis includes all reactions between sandstone mineral phases and the porewater from the instant of deposition to relatively shallow burial before temperatures exceed 25 degrees C (Bjorlykke 1983). Bjorlykke (1983) reviewed the early diagenesis of marine sands. Marine sea water is either in compositional equilibrium with most common detrital mineral phases or so 151 near to the stability field of the minerals that the chemical potential available for equilibrium is very low. Thus, few diagenetic changes occur after deposition of sands in the marine environment. However, subsequent to deposition the original porewater may be replaced by porewater expelled from underlying sediments or meteoric water from the continental meteoric water lens. It is also possible for sea water to circulate down a few centimetres into underlying sand and produce some intitial cementation. And, as pointed out by Berner (1980, p. 136) bioturbation and bacterial processes associated with microbial decomposition of organic matter can significantly complicate diagenesis near the sediment-water interface. In Jordan strata, typically the earliest diagenetic changes include the precipitation of very thin quartz syntaxial overgrowths and potassium feldspar epitaxial overgrowths. As noted by Bjorlykke (1983) the solubility of quartz in marine water is only 6 ppm at 25 degrees C, and this low value is further reduced in shallow nearshore waters to about 1 ppm due to diatom precipitation. Thus, in nearshore water the concentration of silica in solution must be increased at least six times before quartz can precipitate in shallow marine porewater. Large amounts of silica must therefore be locally introduced before early diagenetic quartz cementation can occur. The most likely 152 source of large amounts of quartz for cementation in Jordan strata appears to be metoric water. Blatt (1979) reviewed quartz cementation processes and suggested that most quartz cement is precipitated by vertical circulation of groundwater at very shallow burial depths. Leder and Park (1986) pointed out that a large amount of quartz cementation can occur when sufficient volumes of upward migrating hot porewater encounter decreased temperature and pressure conditions at progressively shallower depths of burial. However, during progressive burial, compaction processes and pressure solution greatly reduce permeabilities and inhibit quartz cementation by fluids migrating upwards. The mode of ancient groundwater circulation in Jordan strata remains highly speculative. The precipitation of potassium feldspar in Jordan strata during early diagenesis is consistent with high alkali and silica concentration in meteoric porewater (Bjorlykke 1983). Odom and others (1979) noted that to precipitate significant amounts of authigenic potassium- feldspar, even in hypersaline pore fluids, requires an external source of K and Al. Possible sources include hypersaline environments which may have existed during deposition of Cambrian and Lower Ordovician carbonates, alteration of illite during dolomitization of carbonates, and hydrothermal processes. 153 Subsequent to the precipitation of authigenic potassium feldspar and quartz, an episode of hematite precipitation occurred. The occurrence of hematite in sandstones is reviewed by Van Houten (1973) but it was Walker (1976) who demonstrated that the hematite is a product of the diagenesis of iron-bearing detrital grains subsequent to deposition. No amorphous iron hydroxide precursor is required. Hematite is stable in a wide range of typical groundwater Eh-pH conditions (Blatt and others 1980, p. 352) at 25 degrees C. As noted by Walker (1976) any type of iron-bearing mineral provides a potential iron source for hematite. Subsequent to hematite precipitation a period of dolomitization occurred. Dolomitization is discussed separately below. Dissolution of potassium feldspar occurred subsequent to dolomitization. As noted by Bjorlykke (1983) feldspar dissolution may occur by hydrolysis in acid and neutral waters. Since solubilities of feldspars are very low, saturation is reached with just small amounts of dissolution by hydrolysis. Dissolution will only continue if there is a constant replenishment of porewater undersaturated with respect to feldspar. Three main types of models have been documented to suggest possible fluid flow mechanisms and fluid compositions which can facilitate large volumes of 154 cement or elastic grain dissolution: (1) sediment dewatering/late leaching due to C02 as described by Schmidt and McDonald C1979a) and refined by Siebert and others (2) elevated groundwater hydraulic head/early leaching by meteoric waters as described by Bjorlykke (1983, and (3) convection currents and temperature dependent dissolution as described by Wood and Hewett Main characteristics of these models are summarized in Figure 59. Bjorlykke (1983, noted that both the "sediment dewatering and late leaching due to C02 model" and the "convection current and temperature dependent dissolution model" have major limitations. It seems most likely that leaching by meteoric waters best explains feldspar and carbonate dissolution in Jordan strata. Periods of regression subsequent to deposition of the Jordan Sandstone may have provided sufficient hydraulic head elevation over long periods of time. Subsequent to the dissolution of potassium feldspar, a period of calcite precipitation occurred (dolomitized at a later time). Blatt (1979) noted that the geochemistry of calcite is quite complex. Three important factors cause much difficulty in predicting calcium carbonate solubility: (1) calcite solubility is very sensitive to pH change, (2) most of the chemical species involved are ions rather than neutral molecules, and (3) the relevant equilibria for 155 1 .. F'RESH WATER FLUSHING TOT AL. FLUX DEPENDS ON LEACHING II GROUND WATER HEAD OF FELDSPAR 2J SANDSTONE GEOMET!lY ANO CARBONATE AND PERMEABIL TY 3J TIME (S EOIMENT A TIOlll RATEJ POROSITY 2 UPWARDS FLOW OF PORE WATER OUE TO CCMPillC· TICN ANO OEHYDRA TIOH THE A VERA GE f'L.UX IS C•· PCLLtO ro•r LIMITED BY THE TOTAL OISSOLUT ION WAlO WATER CONTAINED IN THE DEPENDS ON BASIN. C0 2 PRODUCTION BY KEROGEN ANO CLAY MINERAL REACT ICNS. CONVECTION CURREWTS ORl\IEN BY DENSITY OIFF'ERENSES DUE TO TEMP. WILL NOT OPER· A TE ACROSS LOW PEfil.4EABILIT y -01flerent types of pore-waler BARRIERS ANO ABNOR· flow 1n sed1men1ary basins 111 meteoric "4AL PRESSURE (fresh I water. (2) compac11ona1 pore GRADIENTS. wuer. and 131 con•et11on currenis A•erage porosity anumed. Figure 59. Summary of the main characteristics of secondary porosity models. (From Bjorlykke 1983). 156 calcite precipitation involve a COz gas phase. Thus, generalizations about porewater geochemistry cannot be made for this stage of diagenesis. The remaining stages and associated changes in the diagenetic history of Jordan strata are repetitions of early stages interpreted above. All stages of diagenesis in Jordan strata are typical of shallow burial conditions as described by Blatt and others (1980, p. 360) and changes in the geochemistry and supply of meteoric water probably account for the major diagenetic changes. The only significant diagenetic process not already discussed is dolomitization. Dolomitization As noted above, the occurrence of dolomite is ubiquitous in the Jordan Sandstone. Morrow (1982a, 1982b), Land (1983) and Hardie (1987) reviewed dolomitization modes. Hardie (1987) observed that the two principal models currently used to explain the massive dolomitization of platform carbonates are the hypersaline brine model and the brackish-water mixing-zone model. The hypersaline brine model advanced by Friedman and Sander (1967) evolved from the idea of evaporite brine reflux (Adams and Rhodes 1960) and is typically applied to ancient dolomites associated with evaporites. The brackish-water mixing-zone model is typically applied to dolomites not associated with 157 evaporites. The two predominant variants of this model are the 'Dorag' model described by Badiozarnani (1973) and the 'schizohaline' model described by Folk and Land (1975). Dolomite can also form contemporaneously in arid tidal flat sabkha environments. As discussed above, tidal flat environments in the Jordan Sandstone were probably restricted to portions of the Sunset Point (Coon Valley) Member. It seems possible that some of the Sunset Point (Coon Valley) dolomitic mudstones and wackestones contain primary dolomite. However, the majority of Jordan strata appear to have been deposited in non-tidal flat environments and the ubiquitous dolomite occurrence both vertically and laterally require a diagenetic model. Although an evaporite brine reflux or mixing-zone process may have contributed to dolomitization in the Jordan Sandstone, application of either type of model is very speculative. Hardie (1987) noted numerous difficulties with both of these types of models and advocated four different considerations to dolomitization processes all of which deemphasize the 'special water' requirement: (1) the influence of time and temperature on the kinetics of dolomitization, (2) mass transfer processes, (3) burial diagenetic processes, and chemical information stored in fluid inclusions within dolomite. The analysis of fluid 158. inclusions in Jordan Sandstone dolomite may provide direct answers about temperatures of dolomite crystallization (or recrystallization) and compositions of the dolomitizing (or recrystallizing) fluids. Aulstead and Spencer (1985) successfully used fluid inclusion data in their study of some Devonian dolomites. In conclusion, current models of diagenetic dolomitization processes are equivocal and an attempt to explain dolomitization in the Jordan Sandstone within the framework of current models would be premature. TECTONIC SETTING & CYCLICITY Sloss and others recognized four continent-wide stratigraphic sequences in Cambrian to Jurassic rocks of North America. Two additional continent-wide stratigraphic sequences occur in Jurassic to Recent rocks of North America (Sloss 1963). These sequences have now been described on three continents and are probably of global extent (Sloss 1978; Soares and others 1978). Subsurface seismic stratigraphic research strongly supports this conclusion (Vail and others 1977a, 1977b). Global sea level changes resulting from volume changes of oceanic spreading centers is the most simple mechanism that may account for worldwide stratigraphic sequences (Hallam 1963, Russell 1968, Valentine and Moores 1972, and Rona 1973). Generally, low sea levels occur during low rates of sea-floor spreading and .159 high sea levels occur during episodes of rapid spreading. Major transgressions on cratons would accompany the rapid spreading rates associated with continental break-up and active subduction. Major regressions on cratons would accompany the low spreading rates associated with continental suturing (Vail and others 1977b, Schwan 1980). The earliest of the six North American sequences identified by Sloss (1963) is the Sauk Sequence of Cambrian time. This sequence is characterized by a slow extensive transgression terminated by rapid regression. Vail and others (1977b) calculated that the magnitude of the global rise in sea level which produced the Sauk Sequence transgression was only surpassed in the Phanerozoic era by the global rise in sea level accompanying the long break-up of Pangea. Similarly, the transgression producing the Sauk Sequence during Cambrian times probably resulted from the break-up of an Eocambrian supercontinent (Matthews and Cowie, 1979; Donovan and Jones, 1979). As discussed previously in this chapter, most recent workers agree that the general tectonic setting of the Jordan Sandstone is a continental craton interior. However, opinion is split regarding timing of the craton interior transgressions and regressions relative to the deposition of Upper Cambrian and Lower Ordovician strata. Austin (1972) and Odom and Ostrom (1978) maintained that the rocks of the 160 Jordan Sandstone were deposited during a period of change from regression to transg+ession. Byers (1978) suggested the opposite; that deposition took place predominantly during a period of change from transgression to regression. These opposite conclusions are based on widely differing interpretations of the depositional environments of Jordan strata and are presented schematically in Figure 60. The interpretation of depositional environments (described above) of Jordan strata examined by the author suggests that deposition occurred during a transition from regression (Norwalk Member and Van Oser Member) to transgression (Sunset Point (Coon Valley) Member). Interpretations of the depositional characteristics place both Norwalk and Sunset Point (Coon Valley) strata seaward of Van Oser strata. A general northward progradation of the Sunset Point (Coon Valley) occurred locally in response to increasing rates of carbonate sedimentation. A constant rate of subsidence, coupled with progradation, rather than a eustatic sea level rise is the preferred mechanism for deposition of the transgressive Sunset Point (Coon Valley) Member. CAMERO-ORDOVICIAN BOUNDARY As noted by Miall p. 110) there are problems with many existing chronostratigraphic boundaries. In the past, a preferred way to define a boundary between high- 161 I' Generalized CoUnn OllPll Oep:isitional Enviravnent Peood Fotmalo-1 L1fholoov .>'.o • o:a : • .. za CfDAll V&LU:Y 9 T ,- ·/ .• 1 •)O .. llllQUOUTA I I I . I R ·. IX.9UOUI I I - J J I I . j CIAl.IJIA I l I • T I I I Ill l l I I l I I I I Of) llfCOIW< IKAL.I tr z A < z < Pl.ATTfYILU: ...J z $ 7 a: z Q Cil.ENWOOO ---- T w 0 .. · -\IO > E> It KTlll ...-tOIC ., 0 . R 0 I I 7 . 7- I ,/ llO I I I · \ \ It 11 T? llUllOPll I , I I • \ I I I I ... 1111 I I I I I I I I , , R? I I I I OMIOTA DCILOMfTI I J r L I I T 1111 J 7 .. J0/1t&»M ... R '-JDC) I '7 n LAWMMCI r T I J T --·- -·-- . =:= -axi T flUollCOMIA --- -·------,_TON 55 .. ' . .. R COAi.£ IVILLI IL ---·· _., 3 T IE :----· (5 -·- ·· :·I Glacial 0 ..11 --··- ... .,., R 2 LJ Sandstone _""""'-:"':..=:=:z:-· ---·- ... ..o T St"1Je ·----.. lft POI IA.NDSlt»ll - - R e:ri3 LllTle$lcne _.., MDolomire T T • Transgresson ... R· Reqe 5SIO'l PREc.AMBRIAN ---- BYERS (1978) Figure 60. Generalized stratigraphic column for southeastern Minnesota showing interpreted transgressions and regressions. (Modified from Austin 1972 and Ojakangas and Match 1982). 162 ranking chronostratigraphic units had been to locate it at a hiatus where an abrupt faunal change occurred. However, this type of boundary is rare. Also, because a hiatus represents a break in time, it is quite probable that fossiliferous sediments deposited during the hiatus will eventually be located. Most stratigraphers now prefer to locate chronostratigraphic boundaries within sequences of uninterupted deposition containing distinctive biozones that are easily recognized and widely traceable (Hedberg 1976). Much of Phanerozoic stratigraphy is now undergoing revision (Carter, In North America, trilobite faunal zones defined from Upper Mississippi River Valley type and reference areas were used to locate Upper Cambrian chronostratigraphic boundaries (Berg and others 1956). Because subdivision of the Upper Cambrian was based predominantly on first and last occurrences of specific faunas, a long succession of detailed revisions took place during the 50 years prior to the publication of the Wisconsin-Minnesota column of the National Research Council correlation chart for the Cambrian (Howell and others Presently accepted nomenclature places the top of the Cambrian system at the top of the Saukia zone of the Trempealeauan stage in the Croixan Series. This location of the Cambrian-Ordovician boundary does not, however, generally apply to locations outside mid- 163 continental North America. During late Cambrian and Ordovician times the wide Iapetus Ocean separated the proto- North American continent from other land masses and the vast majority of trilobites and associated fauna differed from elsewhere (McKerrow 1978, p. 65). Recently, conodont faunas have been used to define the Cambrian-Ordovician boundary. Although little is known about the stratigraphic ranges and worldwide distribution of Cambrian conodonts, Cambrian conodonts have great stratigraphic potential (Sweet and Bergstrom 1981). In North America, Miller (1975) identified a conodont zone (Proconodontus zone) entirely within the Upper Cambrian Saukia trilobite zone, and Ethington and Clark (1971) recognized five conodont faunas in the Lower Ordovician. Conodonts identified as Semiacontiodus were found by Melby (1967) in exposures of the Van Oser Member of the Jordan Sandstone in Wisconsin. Acodus was found in the Sunset Point (Coon Valley) Member. Both Semiacontiodus and are typically located in Lower Ordovician rocks and by using conodonts the Cambrian-Ordovician boundary may be placed within the Jordan Sandstone rather than at the top, where it was placed using trilobite fauna. This discrepancy should not seem unusual in light of the problems of using two vastly different faunas to define the same chronostratigraphic boundary. It also seems reasonable to 164 assume that even while recognizing the great lateral extensiveness of Upper Cambrian formations deposited in the Upper Mississippi River Valley, there should be some degree of diachroneity between the chronostratigraphic Cambrian- Ordovician boundary, and the predominantly lithostratigraphic boundary between the Jordan Sandstone and the overlying Oneota Dolomite. Although some early workers, including Graham (1933) and Powell (1933), suggested the occurrence of a major unconformity between Jordan and Oneota strata, evidence from recent studies (Kraft 1956, Wegrzyn 1973, Odom and Ostrom 1978, Kapchinske 1980) confirms the conformable nature of the Jordan-Oneota contact. As noted above (Chapter II), the contact is typically transitional with the exception of the measured section at Stillwater, Minnesota (Section H), where it is relatively sharp but not erosional. Due to the transitional nature of the contact, there can be difficulty at some locations deciding where to put the Jordan-Oneota contact. Odom and Ostrom (1978), Kapchinske (1980) and this study demonstrate the feasibility of placing the contact at the top of the uppermost beds of conspicuously sandy dolomite. However, Adams (1978) included the entire Sunset Point (Coon Valley) Member of the Jordan Sandstone in the Oneota Dolomite. Adams did, though, recognize that his conclusions were based on data limited to the Madison, 165 Wisconsin area. In Minnesota, data collected for this study reflect the typically heterogeneous nature of the Sunset Point {Coon Valley) Member {Chapter II). The author is in agreement with Odom and Ostrom (1978) and Kapchinske (1980) that Sunset Point {Coon Valley) strata represent a viable member of the Jordan Sandstone and are best not included in the Oneota Dolomite. 166 Chapter VIII CONCLUSIONS The conclusions of this study can be surrrnarized as follows (see Chapter VII for details): (1) The characteristics of the Norwalk Member in Minnesota are not 'diagnostic' of a particular depositional environment. The most probable depositional environment is the offshore to lower shoreface. (2) The characteristics of the Van Oser Member in Minnesota do not permit a sophisticated interpretation of the depositional environment but are most typical of the middle and upper shoreface. Tidal currents within the Hollandale Embayrnent were a significant influence on Van Oser deposition. Episodic sedimentation which occurred during storm events is also characteristic of the Van Oser Member. (3) The characteristics of the Waukon strata in Minnesota are essentially identical to those of the Norwalk Member and were deposited in the same depositional environment as the Norwalk Member. Waukon strata may have a lateral extent exceeding 100 km in Minnesota. There are two possible relationships between Waukon strata and the Norwalk Member: Waukon strata are an intertonguing of the Norwalk Member into the Van Oser Member or Waukon strata are a lens- shaped deposit separate from the Norwalk Member. It is more probable that Waukon strata form a lens-shaped deposit and 167 5hould maintain their status as a separate member of the Jordan Sandstone. The heterogeneous characteristics of the Sunset Point (Coon Valley) Member in Minnesota are most typical of deposition in a tide-influenced shallow marine environment transitional from the siliciclastic upper and middle shoreface environments of the Van Oser Member to locally shoaling-upward carbonate environments most probably associated with a prograding offshore platform or development of laterally accreting and migrating tidal islands. The mixing of carbonate and siliciclastic sediments by rare, high-intensity storm events (punctuated mixing) is the most probable process of sediment mixing in Sunset Point (Coon Valley) strata. A progradation of tidal flat wedges model requiring a carbonate platform source area, may prove useful in the depositional interpretation of the lower portions of the Oneota Dolomite which conforrnably overlie the Sunset Point (Coon Valley) Member. (5) The provenance type and tectonic setting distinguished for the Jordan Sandstone is a continental craton interior. Examination of detrital grain composition, composition of the underlying stratigraphy, paleocurrent directions and paleogeography does not reveal an unequivocal geographic or stratigraphic source. However, the paleoslope may be inf erred to have dipped to the south and the most 168 probable source of elastic detritus was to the north. The heavy mineral suite is essentially identical to that of the Galesville Sandstone suggesting that the Galesville Sandstone may have been a major source of detrital components of Jordan strata. The mature multicycle origin of Jordan Sandstone framework components suggests that Precambrian sandstones may also have contributed detritus. (6) Diagenetic processes in the Jordan Sandstone most likely occurred under relatively low temperatures and pressures. Early diagenetic processes (before temperatures exceeded 25 degrees C) were predominant. The paragenetic sequence in order of occurrence is: the precipitation of very thin quartz syntaxial overgrowths and potassium feldspar epitaxial overgrowths, the precipitation of hematite, dolomitization, the dissolution of potassium feldspar and dolomite, the precipitation of calcite cement, the dissolution of calcite, and a second precipitation of hematite. (7) Deposition of the Jordan Sandstone most likely occurred during a transition from regression, typified by Norwalk and Van Oser strata, to constant subsidence coupled with progradation of carbonate sediments, typified by Sunset Point (Coon Valley) strata. Constant subsidence coupled with progradation resulted in a transgressive sequence in the Sunset Point (Coon Valley) Member although no eustatic 169 l rise in sea level is inferred. Progradation resulted from locally increasing rates of carbonate sedimentation. (8) The Cambrian-Ordovician boundary is diachronous and typically gradational in southeastern Minnesota. (9) Lithostratigraphic units of the Jordan Sandstone in Minnesota demonstrate confonnable relationships and have diachronous upper and lower boundaries. (10) Sunset Point strata represent a viable member of the Jordan Sandstone in southeastern Minnesota and are best not included in the overlying Oneota Dolomite. To avoid confusion it may be appropriate to rename the Sunset Point Member in Minnesota as the Coon Valley Member, which is the equivalent unit in Wisconsin. 170 REFERENCES CITED Adams, J.E., and Rhodes, M.L., 1960, Dolomitization by seepage reflux.ion: American of Petroleum Geologists Bulletin, v. p. 1912-1921. Adams, R.L., 1975, Stratigraphy, petrography and diagenesis of the lower Oneota Dolomite (Ordovician) of South- Central Wisconsin [M.Sc. thesis]: Madison, University of Wisconsin, p. 1978, Stratigraphy and petrology of the lower Oneota Dolomite (Ordovician) - south-central Wisconsin, in Lithostratigraphy, petrology, and sedilnentology of Late Cambrian-Early Ordovician rocks near Madison, Wisconsin: Wisconsin Geological and Natural History Survey, Field Trip Guidebook No. 3, p. 82-90. Ahlen, J.L., 1952, The regional stratigraphy of the Jordan Sandstone in west central Wisconsin CM.Sc. thesis]: Madison, University of Wisconsin, p. Aulstead, K.L., and Spencer, R.J., 1985, Diagenesis of the Key River Formation, northwestern Alberta: fluid inclusion evidence: Canadian Petroleum Geology Bulletin, v. 33, p. 167-183. Austin, G.S., 1972, Paleozoic lithostratigraphy of southeastern Minnesota, in Silns, P.K., and Morey, G.B., eds., Geology of Minnesota: a centennial volume: Minnesota Geological Survey, p. Badiozarnani, K., 1973, The dorag dolomitization model - application to the Middle Ordovician of Wisconsin: Journal of Sedilnentary Petrology, v. p. Bates, R.L., and Jackson, J.A., 1980, ·Glossary of geology: Falls Church, Virginia, American Geological Institute, 751 p. Berg, R.R., Nelson, C.A., and Bell, W.C., 1956, Upper Cambrian rocks in southeast Minnesota: Geological Society of America, 1956, Minneapolis Meeting, Guidebook for Field Trips, No. 2, p. 1-15. Berner, R.A., 1980, Early diagenesis: Princeton, New Jersey, Princeton University Press, 237 p. 171 Bjorlykke, K., 1983, Diagenetic reactions in sandstones, .in Parker, A., and Sellwood, B.W., eds., Sediment diagenesis: Dordrecht, The Netherlands, D. Reidel Publishing, p. 169-213. Formation of secondary porosity: how important is it?, in McDonald, D.A., and Surdam, R.C., eds., Clastic diagenesis: American Association of Petroleum Geologists Memoir 37, p. 277-286. Blatt, H., 1979, Diagenetic processes in sandstones: in Scholle, P.A., and Schluger, P.R., eds., Aspects of diagenesis: Society of Economic Paleontologists and Mineralogists Special Publication No. 26, p. Blatt, H., Middleton, G., and Murray, R., 1980, Origin of sedimentary rocks: Englewood Cliffs, New Jersey, Prentice-Hall, 782 p. Bouma, A.H., Berryhill, H.L., Knebel, H.J., and Brenner, R.L., 1982, Continental shelf and epicontinental seaways, in Scholle, P.A., and Spearing, D., eds., Sandstone depositional environments: American Association of Petroleum Geologists Memoir 31, p. 281-328. Boardman, D.C., 1952, Sedimentation and stratigraphy of the Jordan and Madison Formations in central Wisconsin CM.Sc. thesis]: Madison, University of Wisconsin, 33 p. Brasier, M.D., 1980, Microfossils: London, George Allen and Unwin, 193 p. Bridge, J., 1937, The correlation of the Upper Cambrian sections of Missouri and Texas with the section in the Upper Mississippi Valley: U.S. Geological Survey Professional Paper 186 - L, p. 233-237. Byers, C.W., 1978, Depositional environments of fine- grained Upper Cambrian lithofacies, in Lithostratigraphy, petrology and sedimentation of Late Cambrian-Early Ordovician rocks near Madison, Wisconsin: Wisconsin Geological and Natural Histroy Survey, Field Trip Guidebook No. 3, p. 67-81. Carter, R.M., A New Zealand case-study of the need for local time-scales: Lethaia, v. 7, p. 181-202. 172 Chilingarian, G.V., 1983, Compactional diagenesis, in Parker, A., and Sellwood, E.W., eds., Sediment diagenesis: Dordrecht, The Netherlands, D. Reidel Publishing, p. 57-167. Clark, D.L., Sweet, W.C., Bergstrom, S.M., Klapper, G., Austin, R.L., Rhodes, F.H.T., Muller, K.J. Ziegler, W., Lindstrom, M., Miller, J.F., and Harris, A.G., 1981, Miscellarea: Conodonta, in Robison, R.A., ed., Treatise on invertebrate paleontology, Part W, supplement Z: Lawrence, University of Kansas Press and the Geological Society of America, 202 p. Collinson, J.D., and Thompson, D.B., 1982, Sedimentary Structures: London, George Allen and Unwin, p. Curray, J.R., 1956, The analysis of two-dimensional orientation data: Journal of Geology, v. p. 117-131. Dalziel, I.W.D., and Dott, R.H., Jr., 1970, Geology of the Baraboo District, Wisconsin: Wisconsin Geological and Natural History Survey, Information Circular p. Dickinson, W.R., and Suczek, C.A., 1979, Plate tectonics and sandstone compositions: American Association of Petroleum Geologists Bulletin, v. 63, p. Dickinson, W.R., Beard, L.S., Brakenridge, G.R., Erjavec, J.L., Ferguson, R.C., Inman, K.F., Knepp, R.A., Lindberg, F.A., and Ryberg, P.T., 1983, Provenance of North American Phanerozoic sandstones in relation to tectonic setting: Geological Society of America Bulletin, v. p. 222-235. Donovan, D.T., and Jones, E.J.W., 1979, Causes of world- wide changes in sea level: Journal of the Geological Society of London, v. 136, p. 187-192. Dott, R.H., Jr., 1978, Sedirnentology of Upper Cambrian cross-bedded sandstone facies as exemplified by the Van Oser Sandstone, in Lithostratigraphy, petrology, and sedimentation of Late Cambrian-Early Ordovician rocks near Madison, Wisconsin: Wisconsin Geological and Natural History Survey, Field Trip Guidebook No. 3, p. 52-66. Dott, R.H., Jr., and Batten, R.L., 1988, Evolution of the earth (fourth edition): New York, McGraw-Hill. 173 l Dott, R.H., Jr., Byers, C.W., Fielder, G.W., Stenzel, S.R., and Winfree, K.E., 1986, Aeolian to marine transition in Cambre-Ordovician cratonic sheet sandstones of the northern Mississippi Valley, U.S.A.: Sedirnentology, v. 33, p. Duke, W.L., 1985, Hummocky cross-stratification, tropical hurricanes, and intense winter storms: Sedirnentology, v. 32, p. 1987, Reply: Hummocky cross-stratification, tropical hurricanes, and intense winter storms: Sedirnentology, v. p. Dunham, R.J., 1962, Classification of carbonate rocks according to depositional texture, in Harn, W.E., ed., Classification of carbonate rocks: American Association of Petroleum Geologists, Memoir 1, p. 108-121. Ekdale, A.A., Bromley, R.G., and Pemberton, S.G., Ichnology: the use of trace fossils in sedimentology and stratigraphy: Tulsa, Oklahoma, Society of Economic Paleontologists and Mineralogists, 317 p. Elliott, T., 1978, Clastic shorelines, in Reading, H.G., ed., Sedimentary environments and facies: · New York, Elsevier, p. Enos, P., 1983, Shelf environment, in Scholle, P.A., Bebout, D.G., and Moore, C.H., eds., Carbonate depositional environments: American Association of Petroleum Geologists Memoir 33, p. 267-296. Ethington, R.L., and Clark, D.L., 1971, Lower Ordovician conodonts in North America: .in Sweet, W.C., and Bergstrom, S.M., eds., Symposium on conodont biostratigraphy: Geological Society of America, Memoir 127, p. 63-82. Farkas, S.E., 1960, Cross-lamination analysis in the Upper Cambrian Franconia Formation of Wisconsin: Journal of Sed:ilnentary Petrology, v. 30, p. Folk, R.L., and Land, L.S., 1975, Mg/Ca ratio and salinity: two controls over crystallization of dolomite: American Association of Petroleum Geologists Bulletin, v. 59, p. 60-68. 174 Frey, R.W., and Pemberton, S.G., Trace fossils facies models, in Walker, R.G., ed., Facies models (second edition): Geological Association of Canada, Reprint Series 1, p. 189-207. Friedman, G.M., and Sanders, J.E., 1967, Origin and occurrence of dolostones, in Chilingar, G.V., Bissell, H.J., and Fairbridge, R.W., eds., Carbonate Rocks, Part A: Origin, Occurrence, and Classification: Amsterdam, Elsevier, p. Furnish, W.M., 1938, Conodonts from the Prairie du Chien (Lower Ordovician) beds of the upper Mississippi Valley: Journal of Paleontology, v. 12, p. Graham, W.A.P., 1933, Petrology of the Cambrian-Ordovician contact in Minnesota: Journal of Geology, v. p. Hallam, A., 1963, Major epeirogenic and eustatic changes since the Cretaceous and their possible relationship to crustal structure: American Journal of Science, v. 261, p. Hardie, L.A., 1987, Perspectives: Dolomitization - a critical view: Journal of Sedimentary Petrology, v. 57, p. 166-183. Harms, J.C., Southard, J.B., Spearing, D.R., and Walker, R.J., 1975, Depositional environments as interpreted from primary sedimentary structures and stratification sequences: Society of Economic Paleontologists and Mineralogists Short Course No. 2, 161 p. 1982, Structures and sequences in elastic rocks: Society of Economic Paleontologists and Mineralogists Short Course No. 9, p. Hedberg, H.D., ed., 1976, International stratigraphic guide: New York, John Wiley and Sons, 200 p. Helmold, K.P., 1985, Provenance of feldspathic sandstones - the effect of diagenesis on provenance interpretations: a review, in Dordrecht, The Netherlands, D. Reidel Publishing, p. 139-163. 175 Howard, J.D., 1972, Trace fossils as criteria for recognizing ancient shorelines, in Rigby, J.K., and Hamblin, W.K., eds., Recognition of ancient sedimentary environments: Society of Economic Paleontologists and Mineralogists, Special Publication No. 16, p. 215-225. 1975, The sedimentological significance of trace fossils, in Frey, R.W., ed., The study of trace fossils: New York, Springer-Verlag, p. 131-146. Howell, B.F., and others, 1944, correlation of the Cambrian formations of North America: Geological Society of America Bulletin, v. 55, p. 993-1003. Hurlbut, C.S., Jr., and Klein, C., 1977, Manual of Mineralogy (nineteenth edition): New York, John Wiley and Sons, 532 p. Inden, R.F., and Moore, C.H., 1983, Beach environment, in Scholle, P.A., Bebout, D.G., and Moore, C.H., eds., Carbonate depositional environments: American Association of Petroleum Geologists Memoir 33, p. 211-266. Ingram, R.L., 1954, Terminology for the thickness of stratification and parting units in sedimentary rocks: Geological Society of America Bulletin, v. 65, p. 937-938. Irving, R.D., 1875, Note on some new points in the elementary stratification of the primordiol and Canadian rocks of south central Wisconsin: American Journal of Science, 3rd series, v. 9, p. 440-443. James, N.P., 1984, Shallowing-upward sequences in carbonates, i.n Walker, R.G., ed., Facies models (second edition): Geoscience Canada Reprint Series 1, p. 213-228. Johnson, H.D., 1978, Shallow siliciclastic seas, in Reading, H.G., ed., Sedimentary environments and facies: New York, Elsevier, p. 207-258. Kapchinske, J.M., 1980, Petrology of the Coon Valley Member of the Jordan Formation near Lacrosse, Wisconsin [M.Sc. thesis]: Dekalb, Northern Illinois University, 131 p. Kerr, P.F., 1977, Optical mineralogy (fourth edition): New York, McGraw-Hill, 492 p. 176 Klein, G. deV., 1977, Tidal circulation model for deposition of elastic sediment in epeiric and mioclinal shelf seas: Sedimentary Geology, v. 18, p. 1-12. Klein, G. deV., and Marsaglia, K.M., 1987, Discussion: Hummocky cross-stratification, tropical hurricanes, and intense winter storms: Sedimentology, v. p. 333-337. Klein, G. deV., and Ryer, T.A., 1978, Todal circulation patterns in Precambrian, Paleozoic, and Cretaceous epeiric and mioclinal shelf seas: Geological Society of America Bulletin, v. 89, p. 1050-1058. Kraft, J.C., 1956, A petrographic study of the Oneota - Jordan contact zone: Geological Society of America, 1956 Minneapolis Meeting, Guidebook for Field Trips, No. 2, p. 2'-28. Land, L.S., 1983, Dolomitization: American Association of Petroleum Geologists Education Course Note Series No. 2,, 20 p. Leder, F., and Park, W., 1986, Porosity reduction in sandstone by quartz overgrowth: American Association of Petroleum Geologists Bulletin, v. 70, p. 1713- 1728. Martinsson, A., 1970, Toponomy of trace fossils, in Crimes, T.P., and Harper, J.C., eds., Trace fossils: Geological Journal, Special Issue 3, p. 323-330. Matthews, S.C., and Cowie, J.W., 1979, Early Cambrian transgression: Journal of the Geological Society of London, v. 136, p. 133-135. McBride, E.F., 1985, Diagenetic processes that affect provenance determinations in sandstone, in Zuffa, G.G., ed., Provenance of arenites: Dordrecht, The Netherlands, D. Reidel Publishing, p. 95-113. Mccubbin, D.G., 1982, Barrier-Island and strand plain facies, in Scholle, P.A., and Spearing, D., eds., Sandstone depositional environments: American Association of Petroleum Geologists Memoir 31, p. 247-280. McKerrow, W.S., ed., 1978, The Ecology of fossils: Cambridge, Massachusetts, M.I.T. Press, 384 p. 177 Melby, J.H., 1967, The stratigraphy of the Sunset Point Sandstone in western Wisconsin CM.Sc. thesis]: Madison, University of Wisconsin, 95 p. Miall, A.D., Principles of Sedimentary Basin Analysis: New York, Springer-Verlag, p. Michelson, P.C., and Dott, R.H., Jr., 1973, Orientation analysis of trough ication in Upper Cambrian sandstones of western Wisconsin: Journal of Sedimentary Petrology, v. p. Miller, J.F., 1975, Conodont faunas from the Cclrnbrian and lowest Ordovician of western North America: Geological Society of America Abstracts with Programs, v. 7, p. 1200-1201. Morey, G.B., 1972, Pre-Mt. Simon Regolith, in Sims, P.K., and Morey, G.B., eds., Geology of Minnesota: a centennial volume: Minnesota Geological Survey, p. 506-508. Morrow, P.W., 1982a, Diagenesis 1, Dolomite - Part 1: The chemistry of dolomitization and dolomite precipitation: Geoscience Canada, v. 9, p. 5-13. 1982b, Diagenesis 2. Dolomite - Part 2: Dolomitization models and ancient dolostones: Geoscience Canada, v. 9, p. 95-107. Messler, J.H., 1972, Paleozoic structure and stratigraphy of the Twin City region, in Sims, P.K., and Morey, G.B., eds., Geology of Minnesota: a centennial volume: Minnesota Geological Survey, p. 1983, Paleozoic lithostratigraphy of southeastern Minnesota: Minnesota Geological Survey Miscellaneous Map Series M-51, Plate 3, scale 1:500,000. Mount, J.F., Mixing of siliciclastic and carbonate sediments in shallow shelf environments: Geology, v. 12, p. Nelson, C.A., 1956, Upper Croixan stratigraphy: Geological Society of America Bulletin, v. 67, p. 178 North American Commission on Stratigraphic Nomenclature, 1983, North American Stratigraphic Code: American Association of Petroleum Geologists Bulletin, v. 67, p. Ockerman, J.W., 1930, Petrology of Madison and Jordan Sandstones: Journal of Geology, v. 38, p. Odom, I.E., 1975, Feldspar-grain size relations in Cambrian arenites, Upper Mississippi Valley: Journal of Sedimentary Petrology, v. p. 636-650. 1978, Mineralogy of Late Cambrian and Early Ordovician sandstones, Upper Mississippi Valley, in Lithostratigraphy, petrology, and sedimentation of Late Cambrian - Early Ordovician rocks near Madison, Wisconsin: Wisconsin Geological and Natural History Survey, Field Trip Guidebook No. 3, p. Odom, I.E., Willard, T.N., and Lassin, R.J., 1979, Paragenesis of diagenetic minerals in the St. Peter Sandstone (Ordovician), Wisconsin and Illinois, in Scholle, P.A., and Schluger, P.R., Aspects of diagenesis: Society of Economic Paleontologists and Mineralogists Special Publication No. 26, p. Odom, I.E., and Ostrom, M.E., 1978, Lithostratigraphy, petrology, sedimentology, and depositional environments of the Jordan Formation near Madison, Wisconsin, in Lithostratigraphy, petrology, and sedimentation of Late Cambrian - Early Ordovician rocks near Madison, Wisconsin: Wisconsin Geological and Natural History Survey, Field Trip Guidebook No. 3, p. Oja.kangas, R.W., and Matsch, C.L., 1982, Minnesota's Geology: Minneapolis, University of Minnesota Press, 255 p. Ostrom, M.E., 1965, Cambro-Ordovician stratigraphy of southwest Wisconsin: Wisconsin Geological and Natural History Survey, Information Circular 6, 57 p. 1966, Cambrian stratigraphy in western Wisconsin: Wisconsin Geological and Natural History Survey, Information Circular 7, 79 p. 1967, Paleozoic stratigraphic nomenclature for Wisconsin: Wisconsin Geological and Natural History Survey, Information Circular 8, p. 179 1970, Cambrian-Ordovician geology of western Wisconsin: Wisconsin Geological and Natural History Survey, Information Circular 11, 131 p. Owen, D.D., 1852, Report of a geological survey of Wisconsin, Iowa and Minnesota: Philadelphia, Lippincott, Grambo and Company, 638 p. Pemberton, S.G., and Frey, R.W., 1983, Biogenic structures in Upper Cretaceous outcrops and cores: Canadian Society of Petroleum Geologists Guidebook 8, 161 p. ______, 1984, Ichnology of storm-influenced shallow marine sequence: Cardium Formation (Upper Cretaceous) at Soebe, Alberta, in Stott, D.F., ed., Mesozoic of middle North America: Canadian Society of Petroleum Geologists Memoir 9, p. 281-304. Pettijohn, F.J., Potter, P.E., and Siever, R., 1973, Sand and Sandstone: New York, Springer-Verlag, 618 p. Porter, J., 1978, Stratigraphy and depositional environments of the Norwalk Member of the Jordan Formation (Upper Cambrian), southwestern Wisconsin [M.Sc. thesis): Madison, University of Wisconsin, 160 p. Potter, P.E., and Pettijohn, F.J., 1963, Paleocurrents and Basin Analysis: New York, Academic Press, 296 p. 1977, Paleocurrents and Basin Analysis (second edition): New York, Springer-Verlag, 425 p. Powell, L.H., 1933, A study of the Ozarkian fauna of southeastern Minnesota: Science bulletin of the St. Paul Institution, No. 1. Powers, M.C., 1953, A new roundness scale for sedimentary particles: Journal of Sedimentary Petrology, v. 23, p. 117-119. Pratt, B.R., and James, N.P., 1986, The St. George Group (Lower Ordovician) of Western Newfoundland: tidal flat island model for carbonate sedimentation in shallow epeiric seas: Sedimentology, v. 33, p. 313-343. Raasch, G.O., 1939, Cambrian Merostomata: Geological Society of America, Special Paper No. 19, 146 p. 180 1951, Revision of Croixan Dikelecephalidae: Illinois State Academy of Science Transactions, v. p. 137-151. 1952, Oneota Formation, Stoddard Quadrangel, Wisconsin: Illinois State Academy of Science Transactions, v. p. 85-95. Reineck, H.E., and Singh, I.E., 1975, Depositional Sedimentary Environments: Berlin, Springer-Verlag, p. Reinson, G.E., Barrier island and associated strand- plain systems, in Walker, R.G., ed., Facies models (second edition): Geoscience Canada Reprint Series 1, p. Rhoads, D.C., 1975, The paleoecological and environmental significance of trace fossils, in Frey, R.W., ed., The study of trace fossils: New York, Springer- Verlag, p. Rona, P.A., 1973, Relations between rates of sediment accumulation on continental shelves, sea-floor spreading and eustacy inferred from the central North Atlantic: Geological Society of America Bulletin, v. p. 2851-2872. Russell, L.K., 1968, Oceanic ridges and eustatic changes in sea level: Nature, v. 218, p. 861-862. Schmidt, V., and McDonald, P.A., 1979a, The role of secondary porosity in the course of sandstone diagenesis, in Scholle, P.A., and Schluger, P.R., eds., Aspects of diagenesis: Society of Economic Paleontologists and Mineralogists Special Publication No. 26, p. 175-207. ______, 1979b, Texture and recognition of secondary porosity in sandstones, in, Scholle, P.A., and Schluger, P.R., eds., Aspects of diagenesis: Society of Economic Paleontologists and Mineralogists Special Publication No. 26, p. 209-226. Scholle, P.A., and Schluger, P.R., eds., 1979, Aspects of diagenesis: Society of Economic Paleontologists and Mineralogists Special Publication No. 26, p. 181 Schwan, W., 1980, Geodynamic peaks in Alpino-type orogenies and changes in ocean-floor spreading during Late Jurassic - Late Tertiary time: American Association of Petroleum Geologists Bulletin, v. p. 359-373. Scotese, C.R., Bambach, R.K., Barton, C., Van Der Voo, R., and Ziegler, A.M., 1979, Paleozoic base maps: Journal of Geology, v. 87, p. 217-277. Seilacher, A., 1967, Bathyrnetry of trace fossils: Marine Geology, v. 5, p. Sellwood, B.W., 1978, Shallow-water carbonate environments, in, Reading, H.G., ed., Sedimentary environments and facies: New York, Elsevier, p. 259-313. Shanmugam, G., 1985, Types of porosity in sandstones and their significance in interpreting provenance, .in Zuffa, G.G., ed., Provenance of arenites: Dordrecht, The Netherlands, D. Reidel Publishing, p. 115-137. Shinn, E.A., 1983, Tidal flat environment, .in Scholle, P.A., Bebout, D.G., and Moore, C.H., eds., Carbonate depositional environments: American Association of Petroleum Geologists Memoir 33, p. 171-210. Siebert, R.M., Moncure, G.K., and Lahann, R.W., A theory of framework grain dissolution, in McDonald, P.A., and Surdam, R.C., eds., Clastic diagenesis: American Association of Petroleum Geologists Memoir 37, p. 163-175. Sloss, L.L., 1963, Sequences in the cratonic interior of North America: Geological Society of America Bulletin, v. p. 93-113. 1978, Global sea level changes: a view from the craton, in Watkins, J.S., Montadert, L., and Dickerson, P.W., eds,. Geological and geophysical investigations of continental margins: American Association of Petroleum Geologists Memoir 29, p. Sloss, L.L., Krumbein, W.C., and Dapples, E.C., Integrated facies analysis, in Longwell, C.R., ed., Sedimentary facies in geologic history: Geological Society of America Memoir 39, p. 182 Soares, P.C., Landim, P.M.B., and Fulfaro, V.J., 1978, Tectonic cycles and sedimentary sequences in the Brazilian intracratonic basins: Geological Society of America Bulletin, v. 89, p. 181-191. Stauffer, C.R., 1925, The Jordan Sandstone: Journal of Geology, v. 33, p. 699-713. Stauffer, C.R., Schwartz, G.M., and Thiel, G.A., 1939, St. Croixan classification of Minnesota: Geological Society of America Bulletin, v. 50, p. Stauffer, C.R., and Thiel, G.A., 1941, The Paleozoic and related rocks of southeastern Minnesota: Minnesota Geological Survey Bulletin No. 29, 251 p. Stone, J., 1987, Review of investigative techniques used in the study of conodonts, in Austin, R.L., ed., Conodonts: investigative techniques and applications: Chichester, England, Ellis Horwood and the British Micropalaeontological Society, 422 p. Sweet, W.C., and Bergstrom, S.M., 1971, Symposium on conodont biostratigraphy: Geological Society of America Memoir 127, p. Swift, D.J.P., and Nummedal, D., 1987, Discussion: Hummocky cross-stratification, tropical hurricanes and intense winter storms: Sedimentology, v. 34, p. 338-344. Thwaites, F.T., 1923, The Paleozoic rocks found in deep wells in Wisconsin and northern Illinois: Journal of Geology, v. 31, p. 528-555. Tillman, R.W., 1985, A spectrum of shelf sands and sandstones, in Tillman, R.W., Swift, D.J.P., and Walker, R.G., eds., Shelf sands and sandstone reservoirs: Society of Economic Paleontologists and Mineralogists Short Course Notes No. 13, p. 1-46. Trowbridge, A.C., and Atwater, G.I., 1934, Stratigraphic problems in the Upper Mississippi Valley: Geological Society of America Bulletin, v. 45, p. 21-80. Twenhofel, W.H., Raasch, G.O., and Thwaites, F.T., 1935, Cambrian strata of Wisconsin: Geological Society of America Bulletin, v. 46, p. 1687-1743. I 183 I I Twenhofel, W.H., and Thwaites, F.T., 1919, Paleozoic section of the Sparta and Tomah quadrangles, Wisconsin: Journal of Geology, v. 27, p. 614-633. Ulrich, E.O., 1911, Revision of the early Paleozoic systems: Geological Society of America Bulletin, v. 22, p. 6/sO. ______, 192/s, Notes on new names in the table of formations and on physical evidence of breaks between Paleozoic systems in Wisconsin: Wisconsin Academy of Science, Arts and Letters, Transactions, v. 21, p. 71-107. Ulrich, E.O., and Resser, C.E., 1930, The Cambrian of the upper Mississippi Valley, Part I, Trilobita: Dikelocephalinae and Osceolinae: Milwaukee Public Museum Bulletin, v. 12, no. 1, p. 1-22. ------' 1933, The Cambrian of the upper Mississippi Valley, Part II, Trilobita: Saukinae: Milwaukee Public Museum Bulletin, v. 12, no. 2, p. 123-306. Van Andel, T.H., and Curray, J.R., 1960, Regional aspects of modern sedimentation in the northern Gulf of Mexico and similar basins, and paleogeographic significance, in recent sediments, northwest Gulf of Mexico: Tulsa, American Association of Petroleum Geologists, p. 3'-5-364. Van Houten, F.B., 1973, Origin of red beds - a review 1961-1972: Annual Review of Earth and Planetary Sciences, v. 1, p. 39-61. Vail, P.R., Mitchum, R.M., Jr., and Thompson, S., III, 1977a, Seismic stratigraphy and global changes of sea level, part three: relative changes of sea level from coastal onlap: American Association of Petroleum Geologists Memoir 26, p. 63-82. ______, 1977b, Seismic stratigraphy and global changes of sea level, part four: global cycles of relative changes of sea level: American Association of Petroleum Geologists Memoir 26, p. 83-98. Valentine, J.W., and Moores, E., 1972, Global tectonics and the fossil record: Journal of Geology, v. 80, p. 167-18'-. 184 I ( I Walker, R.G., 1984, Shelf and shallow marine sands, in Walker, R.D., ed., Facies models (second edition): Geoscience Canada Reprint Series 1, p. 141-170. Walker, T.R., 1976, Diagenetic origin of continental red beds, in Falke, H., ed., The continental Permian in central, west and south Europe: Dordrecht, The Netherlands, D. Reidel Publishing, p. 240-282. Walcott, C.D., 1914, Croixan geology and paleontology: Smithsonian Miscellaneous Coll., v. 57, p. 353-363. Wanemacher, J.M., Twenhofel, W.H., and Raasch, G.O., 1934, The Paleozoic strata of the Baraboo area, Wisconsin: American Journal of Science, v. 228, p. 1-30. Webers, G.F., 1972, Paleoecology of the Cambrian and Ordovician strata of Minnesota, in Sims, P.K. and Morey, G.B., eds., Geology of Minnesota: a centennial volume: Minnesota Geological Survey, p. 474-484. Wegrzyn, R.S., 1973, Petrology of the Jordan Sandstone, western Wisconsin and eastern Minnesota CM.Sc. thesis]: Dekalb, Northern Illinois University, 148 p. Weimer, R.J., Howard, J.D., and Lindsay, D.R., 1982, Tidal flats and associated tidal channels, .in Scholle, P.A., and Spearing, D., eds., Sandstone depositional environments: American Association of Petroleum Geologists Memoir 31, p. 191-246. Wilson, J.E., and Jordan, C., 1983, Middle shelf environment, in Scholle, P.A., Bebout, D.G., and Moore, C.H., eds., Carbonate depositional environments: American Association of Petroleum Geologists Memoir 33, p. 297-344. Winchell, N.H., 1874, Geology of the Minnesota Valley: Minnesota Geological and Natural History Survey, 2nd Annual Report, p. 152-155. 1886, Revision of the stratigraphy of the Cambrian in Minnesota: Minnesota Geological and Natural History Survey, 14th Annual Report, p. 336. Wood, J.R., and Hewett, T.A., 1984, Reservoir diagenesis and convective fluid flow, in McDonald, D.A., and Surdam, R.D., eds., Clastic diagenesis: American Association of Petroleum Geologists Memoir 37, p. 99-109. J ( 185 ) I APPENDIX 1 95° I 0 200 km SCALE RCSEAV llOSMALL POLK . i llORllAN •llOW[ll 47° IUSCA AITKIN CA!S 8CCKER CLAY CR Ow WING WILKIN t N • TOWN NEAREST TO MEASURED SECT10N .! ! MURRAT 440 r i' •ocx i 96° 95° 94° 93° gzo INDEX MAP OF MINNESOTA COUNTIES 186 APPENDIX 2 Measured Section Location Descriptions Section A: Roadcut on southeast side on Winona County Road 15, approximately 2 miles south of Homer, Winona County, Minnesota in T. 106 N., R. 6 W., at bounary between Sec. 9 and 16. Section B: Roadcut on north side of Houston County Road approximately 1/2 mile west of junction with Minnesota Highway 26, Houston County, Minnesota, T. 101 N., R. W., N.W. S.W. Sec. Section C: Roadcut on north side of Wabasha County Road 26, approximately mile west of Weaver, Wabasha County, Minnesota, T. 109 N., R. 10 W., N.W. Sec. 30. Section D: Roadcut on north side of Minnesota Highway 60 at scenic overlook, approximately miles west from junction with U.S. Highway 61 in Wabasha County, Minnesota, T. 110 N., R. 11 W., Sec. 12. Section E: Roadcuts on Minnesota Highway 58, approximately 1 mile northeast of Hay Creek, Goodhue County, Minnesota, T. 112 N., R. W., Sec. 8. Section F: Cliff on north side of railway tracks, Washington County, Minnesota, T. 26 N., R. 21 W., Sec. 1, S.W. approximately 50 m east of Lock and Dam No. 2 on the Mississippi River. Section G: Cliff on north side of Minneopa Creek below water fall in Minneopa State Park, Blue Earth County, Minnesota, T. 108 N., R. 27 W., N.W. Sec. 21. Access via Blue Earth County Road 69 to picnic area above falls. Section H: Roadcut at junction of Minnesota Highway 95 and Elm Street in Stillwater, Washington County, Minnesota, T. 30 N., R. 20 W., Sec. 28. Section I: Outcrop along creek in valley, approximately miles west of Scandia, Washington County, Minnesota, T. 32 N., R. 19 W., N.E. S.W. Sec. 18. (Unpublished section, Minnesota Geological Survey, 1981). Section J: Outcrop approximately 1 mile south of Afton (junction of Minnesota Highway 95 and Washington County Road 21), Washington County, Minnesota, T. 28, N., R. 20 W., at boundary of Sec. 22 and 27. (Unpublished section, Minnesota Geological Survey, 1981). 187 { Section K: Outcrop in ravine along Minnesota Highway 95 approximately 1/2 mile north of Copas, Washington County, Minnesota, T. 32 N., R. 19 W., S.W. N.W. S.W. 1/4, Sec. 19. (Unpublished section, Minnesota Geological Survey, 1981). Section L: Quarry on west side of U.S. Highway 169, approximately 3 miles northeast of Jordan, Scott County, Minnesota, T. N., R. 23 @., N.E. N.W. Sec. (Unpublished section, Minnesota Geological Survey, 1981). Note: A General Highway for each county in Minnesota is available from the Minnesota Department of Transportation. I 188 ( I APPENPIX 3 Measured Section Descriptions and Thin Section Sample Locations Dolomite Massive (homogeneous) Sandstone L LH Stromatolites Planar Parallel Stratified Sandstone l::::JHB Herringbone Planar Parallel Crou - stratification Stratified Siltstone Oolitea Disc.,ntinuous Planar Parallel Stratified Sandstone Flat - pebble Discontinuous Rip - up Clasts Crou- stratified Sandstone Planolites I Om 0 Skolithos Arencolites VERTICAL 5m SCALE Trough Cross - stratification Tabular Cross - stratification 0 HCS Hummocky •12 Modal Analysis Cross - stratification Sample Symmetrical •20 Hand Sample Ripples Described In Text Asymmetrical Paleocurrent Cross-Bedding Ripples Measurement 189 SECTION A: Winona County Rd. 15 ONEOTA DOLOMITE SUNSET POINT (COON VALLEY) MBR NORWALK (WAUKON)MBR JORDAN SANDSTONE VAN OSER MBR .J NORWALK MBR ST. LAWRENCE FM md yf m we 'I'• . fI' cI' 190 SECTION B: Houston County Rd. 14 ONEOTA DOLOMITE •135 '\ SUNSET POINT /' /f (COON VALLEY) HCS? J ....-; •1094'\ \,...._//" VAN OSER MBR JORDAN SANDSTONE ·105\.- ·103 NORWALK MBR mo vi m we 'I'• fI' cI' 191 . SECTION C: Wabasha County Rd. 26 POINT _. (COON VALLEY) MBR •166 VAN OSER MBR JORDAN SANDSTONE •160 NORWALK MBR md vi m vc • 'I'• 'I' cI' 192 SECTION D: Wabasha County, Hwy. &O SUNSET POINT (COON VALLEY) MBR +- HB'? VAN OSER MBR JORDAN SANDSTONE NORWALK MBR _ '·VAN OSER MBR NORWALK MBR md YI m YC 'I'• I'f cI' 193 SECTION E: Goodhue County, Hwy. 58 ONEOTA DOLOMITE SUNSET POINT (cOON VALLEY).. MBR ,·. ,.,·.. ,..,_,. ·.-., •287•266 VAN OSER MBR AS • 275 ! JORDAN SANDSTONE ·. i IJ ii • ct: z'i ,,, NORWALK MBR mo'I' wl Im 1 I1we • I c 194 SECTION F: Hastings Lock & Dam ONEOTA DOLOMITE ------·-- SUNSET POINT (COON VALLEY) MBR. JORDAN SANDSTONE VAN OSER MBA , , I I "'°J"f Ilft' IWC s I c 195 SECTION G: Mankato f -... VAN OSER MBR JORDAN SANDSTONE t 111dI I wf 1 I'111 I'we • t c 196 SECTION H: Stillwater ONEOTA DOLOMITE SUNSc I POIN I (COON VALLEY) MBR VAN OSER MBR JORDAN SANDSTONE NORWALK MBR HCS? . • ·....;....,_. .._ . .1, \ ...... ST. LAWRENCE FM mCI wl m we UNPLeUSl-ED MEASURED SECTION, MINNESOTA GEOl.OGICAL SlJ:IVEY 'I'• I'f cI' 197 SECTION I: Scandia ONEOTA DOLOMITE SUNSET POINT (COON VALLEY) MBR \ ' VAN OSER MBR JORDAN SANDSTONE ST. LAWRENCE FM UNPLBU&ED MEASlffO SECTION. MINNESOTA GEOLOGICAL &mEY lllc:II I Yf' IIll 1 IYC1 .. f c 198 SECTION J: Afton ONEOTA DOLOMITE VAN OSER MBR JORDAN SANDSTONE NORWALKMBR ST. LAWRENCE FM mesI wt "' •c UNPUBUSHED MEASl.REO SECTION. GEOlOGICAI. Sll'IVEY •I ' I, ' cI ' 199 SECTION K: Copas ONEOTA DOLOMITE ,...,t .. _. SUNSET POINT f ------(COON VALLEY) MBR VAN OSER MBR JORDAN SANDSTONE NORWALK MBR mdvlmvc' I' I' J I UNPUBLISHED MEASURED SECTION. MINNESOTA GEOLOGICAL SURVEY a I c 200 SECTION L: Frac Sand Quarry JORDAN SANDSTONE UNPLeUSHED SECTION. MINNESOTA GEOLOGICAL SI.AVEY md "' Im ' .c '• I ' t Ic: ' 201 APPENPIX Paleocurrent Data (Note: see Chapter IV for explanation of data) Section A: azurniths = 100 , 294 ' 300 ' 254 ' 270 ' 276 ' 295 ' 98 ' 112 ' 75 ' 125 ' 25 ' 244 ' 82 ' 62 ' 77 ' 218 ' 104 ' 166 ' 165 ' 252 ' 74 ' 137 ' 200 ' 335 ' 126 ' 175 ' 110 ' 125 ' 162 ' 345 ' 119 ' ' 84 ' 162 ' 212 ' \ 117 • I \ \ tax x = En sinx = +8.4390 = -1.1528 En cosx -7.3202 arctan x = Vector Mean = 131 vector magnitude= R = JC8.4390)2 + (-7.3202)2 = 11.1715 % vector magnitude = L = CR/n) x 100 = 30.19% Variance: 5360 = 2(52.3 - .340 L) = 84.071 52360 = 84.0712 = 7067.9 Section B: azumiths = 134 , 232 , 161 , 274 , 212 , 235 , 220 ' 88 ' 140 ' 155 ' 90 ' 157 ' 147 ' 234 ' 125 ' 182 ' 324 ' 290 ' 47 ' 116 ' 164 ' 48 ' 34 ' 136 ' 90 ' 198 ' 240 ' 205 ' 20 ' 62 ' 252 ' 16 ' 154 ' 128 ' 275 ' 56 . tan x = En sinx = +4.6293 = -.4927 En cosx -9.3094 arctan = -26.440 Vector Mean = 154 vector magnitude = R = J(4.6293)2 + C-9.3094)2 = 10.3969 % vector magnitude = L = CR/n) x 100 = 28.88% Variance: 5360 = 2(52.3 - .340 L) = 84.9616 s 2360 = 84.96162 = 7218.47 Section H: azumiths = 60 , 150 , 130 , 280 , 170 , 120 , 150 ' 100 ' 110 ' 200 ' 60 ' 175 ' 235 ' 65 ' 340 ' 110 ' 275 ' 290 ' 300 ' 170 ' 130 ' 265 ' 255 ' 230 ' 250 ' 270 • tan x = En sinx = - .6226 = .09265 En cosx -6.720 arctan = 5.2932 Vector Mean = 185 202 vector magnitude = R = J(-.6226)2 + C-6.7200)2 = % vector magnitude = L = CR/n) x 100 = 25.9568% Variance: 5360 = 2(52.3 - L) = s 2360 = = 7560.2 Section I: azurniths = 65 , 5 , 250 , 30 , 225 , 310 , 315 , 110 ' 250 ' 250 ' 230 ' 10 ' 80 ' 190 ' 120 ' 130 ' 165 ' I I 260 ' 210 ' 40 ' 350 ' 150 ' 260 , 280 ' 300 ' 50 ' 100 ' 80 \ , 280 ' 200 ' 210 ' 315 ' 330 ' 300 • I \ tan x = En sinx = = -12.106 \ En cosx + .4107 arctan = -85.28 Vector Mean = 275 vector magnitude= R = J(-4.9721)2 + C.4107)2 = 4.9890 % vector magnitude = L = CR/n) x 100 = 14.6736% Variance: 5360 = 2(52.3 - .340 L) = 94.6219 5 2360 = = 8953.3 203 APPENDIX 5 Monocrystalline Quartz Extinction Data Van Oser Member Data: Undulose <>1°) extinction:straight extinction ratios were recorded for monocrystalline quartz grains in 27 samples: 273:86, 99:256, 129:190, 316:69, 328:93, 359:62, 258:157, 95:225, 198:202, 117:213, 231:161, 191:217, 285:121, 297:117, 202:130, 295:139, 317:111, 135:255, 128:126. \ Sunset Point (Coon Valley) Member Data: Undulose ()10) extinction:straight extinction ratios were recorded for monocrystalline quartz grains in 5 samples: 71:136, 125:176, 36:152, 204