Cambro-Ordovician of the Illinois Basin

RDOVICI -O AN O O R F B T M H A E C ILLINOIS BASIN Cambro-Ordovician of the Illinois Basin Overview

This GeoDigital Information study of the exploration potential of the deeper portion of Cambrian and Ordovician sandstones of the the Illinois Basin, but studies of these Illinois Basin is designed to assist relatively shallow fields were used in exploration and production geologists in combination with the extensive core control their understanding of factors that control from the basin margins to provide a hydrocarbon distribution and production framework for future exploration of these potential in these reservoirs. This research deep reservoirs. Special emphasis was is a logical compliment to the GDI study of placed on recognizing and mapping the deep Ordovician gas reservoirs in the potential hydrocarbon source rock intervals Michigan Basin. These lower Paleozoic and on defining thermal maturity trends of rocks of the Illinois Basin are similar in these source rocks within the basin. many ways to those in the Michigan Basin and, thus, offer similar reservoir potential. All or portions of 115 counties in This fact has created interest in the deep southeastern Illinois, southwestern Indiana, potential of this region. Adding to the and western Kentucky lie within the study reservoir potential of the Cambro- area. 366 wells penetrating more than 100 Ordovician rocks in the Illinois Basin is the feet below the Trenton Limestone (Galena fact that many large hydrocarbon reservoirs Group in Illinois) were included in the occur in equivalent age rocks in nearby stratigraphic database. While this is an parts of the U.S. Midcontinent such as average of only one well per 60 miles (and eastern Indiana, northwestern Ohio, much less than this for the deep part of the Kansas, and Oklahoma. basin), it reflects the relatively untested nature of the Cambro-Ordovician section in This study integrates a variety of data sets the study area. including wireline logs, cores, seismic lines, source rock analyses, and published This study defines successfully the regional literature to provide a comprehensive stratigraphic markers and intervals in the summary of the stratigraphy, lithologies, Cambro-Ordovician section of southern depositional environments, hydrocarbon Illinois, southwestern Indiana, and western source potential, and reservoir possibilities Kentucky. It also generates a in the Cambro-Ordovician section. comprehensive and internally consistent stratigraphic database for all study wells. Lower Paleozoic rocks in the Illinois Basin This includes the definition and correlation occur at depths ranging from 1,000 feet of stratigraphic markers that can be traced along the basin margins to more than laterally through parts or all of the 50,000 13,000 feet in the center of the basin. square mile study area. Approximately 20 Ordovician oil fields, located mainly near the basin margins, In addition, the study describes the major provide evidence that deeper fields may be lithologies within each stratigraphic interval present in the basin center. This regional based on core examination and log geological study focuses mainly on the interpretation. It also examines the petrography of reservoir and source rocks particularly the source and reservoir with emphasis on mineralogy, lithology, lithologies. These various data sets are types and origin of porosity, and the types of integrated to define promising plays and organic matter (in the source rocks). From trends for future exploration and this information, depositional models are development of Cambro-Ordovician generated for predicting the regional reservoirs in the Illinois Basin. distribution of the various lithologies,

Database

366 Study Wells 34 Cores Described (8,980'')

28 Regional Stratigraphic Markers 359 Thinsections

Organic Geochemical Analyses

A total of 64 samples from 32 wells were selected for source rock analyses to provide a representative stratigraphic and geographic distribution of geochemical data. Due to the absence of Cambro-Ordovician cores at the Kentucky Geological Survey, only cuttings were available from wells in western Kentucky. Cuttings were also used for several wells (e.g., #1 Cuppy, #1 Cisne, #1 Farley) in Illinois and Indiana where cores of promising source beds were not available.

Key Well Panels

Nine important wells in the database were selected for generation of Key Well Panels. These panels include a digitized log suite for a selected portion of the stratigraphic column (generally the Ancell to Trenton section), computer-generated lithologic interpretations for this part of the log, core descriptions where available, a synthetic seismic trace generated from the log data, and a short section of one of seismic lines (where available near the wellsite) showing the reflectors so that these can be correlated to the synthetic seismogram.

Cross Sections

7 Regional Cross Sections (VS 1" = 20 Field Cross Sections (VS 2.5" = 100') 100')

Regional Maps

8 Regional Isopach Maps 1 Sandstone Isolith Map (St. Peter)

1 Structure Map (Top of Trenton) 1 Hydrocarbon Show & Production Map

Report Contents

TEXT AND FIGURES - This extensively STRATIGRAPHIC DATA - Well illustrated report includes discussion, identification and stratigraphic marker data figures, and color photographs on such for the 366 study wells in this study are topics as: Depositional Setting, Stratigraphy available in digital form. This database and Lithofacies, Depositional History, includes the 28 stratigraphic tops, lithologic Petrography, Petrophysics, Exploration markers, and chronostratigraphic picks data Recommendations, and Bibliography. for the study wells. This information is referenced by well name, operator, and API CORE DESCRIPTIONS - This section number. contains the detailed descriptions of 8,980 feet of core from 34 wells throughout the MAPS AND CROSS SECTIONS - These Illinois Basin and on the Kankakee Arch two files contain a grid of cross sections and between the Illinois and Michigan basins. maps. Fifty six field maps, 20 field cross These descriptions provide a basis for sections, 37 regional maps and seven defining lithology and depositional regional cross sections are provided for sequences in the various formations of correlation and mapping applications. The Cambrian and Ordovician age in the Illinois regional maps show the distribution of wells, Basin. structural elements, sedimentary and diagenetic facies, porosity, and production. EXECUTIVE SUMMARY ATLAS - This section provides a brief review of major findings of the study. It includes small-scale versions of key maps and cross sections.

Cambro-Ordovician Study of Illinois Basin

TAZEWELL FORD MC- MCLEAN WARREN TIPPE- DONOUGH FULTON CANOE CLINTON TIPTON MASON MADI- SCHUYLER DE WITT SON CHAMPAIGN HAMIL- LOGAN FOUNTAIN MONT- BOONE TON MENARD PLATT VERM LL ON GOMERY CASS BROWN Study Boundary HAN- MACON HEND- MARION COCK SANGAMON RICKS MORGAN DOUGLAS PARKE EDGAR PUTNAM PIKE SCOTT VERM SHELBY CHRISTIAN MOULTR E COLES MORGAN

VIGO JOHNSON SHELBY CLAY GREENE PIKE CALHOUN CLARK OWEN MACOUPIN MONTGOMERY CUMBER- LAND INDIANA JERSEY ILLINOIS SULLIVAN LINCOLN EFFINGHAM GREENE JENN- FAYETTE JASPER CRAWFORD INGS JACKSON BOND TRIGG ST. MADISON CHARLES CLAY RICH- LAW- DAVIESS RENCE KNOX SCOTT MARION LAND WASHING- ST. LOUIS CLINTON MART N TON ORANGE ST. CLAIR CLARK FRANK- WAYNE PIKE FLOYD DUBOIS LIN WASHINGTON CRAWFORD JEFFERSON WABASH GIBSON JEFFER- MONROE EDWARDS HARR- JEFFER- SON ISON SON PERRY PERRY HAMIL- WHITE WARRICK RANDOLPH MEADE WASHING- TON BUL-

POSEY BURGH FRANKLIN VANDER- SPENCER LITT TON STE. HANCOCK GENE- ST. VIEVE GAL- BRECKIN- FRAN- JACKSON SALINE HENDERSON WILLIAMSON LATIN RIDGE SOIS PERRY DAVIESS HARDIN UNION MCCLEAN LARUE HARDIN WEBSTER OHIO GRAYSON MISSOURI CAPE UNION JOHNSON POPE REY- GIRARDEAU BOLL- LIVINGSTON CRITTENDEN NOLDS ALEXANDER HART HOPKINS EDMONSON INGER MASSAC CALDWELL MUHLEN- BUTLER WAYNE BERG PULASKI MCCRACKEN SCOTT BALLARD MARSHALL LYON KENTUCKY WARREN BARREN CHRISTIAN MISS- LOGAN ISSI- CARLISLE TODD TRIGG MON- 0 N 60 PPI GRAVES SIMPSON ALLEN NEW HICKMAN ROE MADRID MILES CALLAWAY FULTON STEWART MONTGOMERY ROBERTSON SUMNER MACON Cambro-Ordovician Study of the Illinois Basin

Study Table of Contents

TABLE OF CONTENTS

Table of Contents………………………………………………………………………… i List of Figures …………………………………………………………………… vi List of Maps, Cross Sections, and Key Panels ………………………………xxi

SUMMARY Summary Study Objectives ……………………………………………………...………… S-1 Study Area ………………………………………………………….…………… S-2 Regional Setting and Paleoclimate ……………………………..…………….. S-2 Stratigraphy of the Sauk Sequence …………………….…….………………. S-4 Stratigraphy of the Whiterockian Sequence …………….……..…………….. S-5 Stratigraphy of the Lower Tippecanoe Sequence ………..…………………. S-5 Lithologies ……………………………………………………….………………. S-7 Porosity Types …………………………………………………………………...S-10 Depositional History ……………………………………………………………..S-12 Source Rock Evaluation and Burial History ………………………………….. S-14 Exploration Concepts …………………………………………………….…….. S-17

CHAPTER 1 Introduction General Introduction ………………………………………………………..….. 1-1 Objectives of the Study ……………………………………………………..…. 1-2 Study Area …………………………………………………………………….… 1-3 General Stratigraphy …………………………………………………………… 1-4 Methods and Data ……………………………………………………………… 1-6 Study Wells ………………………………………………………….….. 1-7 Key Well Panels …………………………………………………...…… 1-7 Cores ……………………………………………………………………. 1-7 Petrography ………………………………………………………..…… 1-8 Source Rock Analyses ……………………………………………..…..1-8 Seismic Data …………………………………………………..……….. 1-9 Field Studies ……………………………………………………...……..1-9 Report Format ……………………………………………………………………1-9

CHAPTER 2 Exploration History Introduction …………………………...…………………………………………. 2-1 Trenton and Lima Fields …………..…………………………………………... 2-1 Early 1900s ……………………………………………………………..………. 2-5 1936 to 1959 …………………………………………………………………..... 2-7 1960 to 1969 …………………………………………………………………….. 2-9 1970 to 1979 …………………………………………………………………….. 2-11 1980 to 1990 …………………………………………………………………….. 2-13 Conclusion ………………………………………………………………………. 2-15

i CHAPTER 3 Regional Setting and Structural History Introduction ……………………………………………………………………… 3-1 Tectonic Framework and Basin Evolution …………………………………… 3-2 Late Precambrian ……………………………………………………….3-3 Cambrian Events ………………………………………………………. 3-3 Ordovician Events ……………………………………………………… 3-5 Silurian, Devonian, and Mississippian Events ……………………… 3-8 Pennsylvanian-Permian Events ……………………………………….3-11 Mesozoic Events ……………………………………………………….. 3-13 Cenozoic Events ……………………………………………………….. 3-14 Summary of Events ……………………………………………………. 3-14 Paleolatitude and Climate ……………………………………………………… 3-15

CHAPTER 4 Stratigraphy of the Sauk Sequence Introduction …………………………………………………..………………….. 4-1 Methods ……………………………………………………..…………………… 4-2 Sauk Sequence …………………………………………………………………. 4-3 Sauk 1 Subsequence ………………………………………………….. 4-5 ……………………………………... 4-5 …………………………………………. 4-6 Sauk 2 Subsequence ………………………………………………….. 4-8 Galesville and Ironton Sandstones ………………………….. 4-9 ……………………………………………….. 4-10 Knox Group: ………………………………… 4-10 Sauk 3 Subsequence ………………………………………………….. 4-12 Jordan and Gunter Sandstones ……………………………… 4-12 ………………………………………………. 4-13 Sauk 4 Subsequence ………………………………………………….. 4-13 New Richmond Sandstone …………………………………… 4-14 …………………………………………… 4-15 Conclusions ………………………………………………………………………4-16

CHAPTER 5 Stratigraphy of the Whiterockian and Lower Tippecanoe Sequences Introduction ……………………………………………………………………… 5-1 Whiterockian Sequence ………………………………………………………... 5-2 Tippecanoe Sequence …………………………………………………………. 5-4 Champlainian Series …………………………………………………... 5-5 Ancell Group …………………………………………………… 5-6 St. Peter Sandstone …………………………………………... 5-6 Dutchtown Formation …………………………………………. 5-11 Joachim Dolomite ………………..……………………………. 5-13 Platteville Group (Illinois) and Black River Group (Indiana) ………………………………. 5-16 Pecatonica Formation ………………………………………… 5-17 Black River Limestone ………………………………………... 5-18

ii Trenton Limestone/ ……………………………5-20 Cincinnatian Series ……………………………………………………. 5-22 Maquoketa Group ……………………………………………... 5-22 Conclusions ………………………………………………………………………5-25

CHAPTER 6 Lithology, Petrography, and Pore Types Introduction ……………………………………………………………………… 6-1 Methods ………………………………………………………………………….. 6-1 Precambrian Basement …………………………………………………………6-2 Mount Simon Sandstone ………………………………………………………. 6-2 Lithology and Petrography ……………………………………………. 6-3 Regional Distribution and Depositional Trends …………………….. 6-4 Porosity Types and Distribution ………………………………………. 6-5 Eau Claire Formation ……………………………………………………………6-6 Lithology and Petrography ……………………………………………. 6-7 Regional Distribution and Depositional Trends …………………….. 6-10 Porosity Types and Distribution ………………………………………. 6-11 Davis Formation ………………………………………………………………… 6-12 Knox Group ……………………………………………………………………… 6-14 Lithology and Petrography …………………………………………..... 6-14 Regional Distribution and Depositional Trends …………………….. 6-17 Porosity Types and Distribution ………………………………………. 6-18 Everton Dolomite ……………………………………………………………….. 6-21 Lithology and Petrography ……………………………………………. 6-21 Regional Distribution and Depositional Trends …………………….. 6-22 Porosity ………………………………………………………………….. 6-22 St. Peter Sandstone ……………………………………………………………. 6-23 Lithology and Petrography ……………………………………………. 6-23 Regional Distribution and Depositional Trends …………………….. 6-25 Porosity Types and Distribution ………………………………………. 6-26 Dutchtown Formation …………………………………………………………... 6-27 Lithology and Petrography ……………………………………………. 6-27 Regional Distribution and Depositional Trends …………………….. 6-28 Porosity Types and Distribution ………………………………………. 6-29 Joachim Dolomite ………………………………………………………………. 6-29 Lithology and Petrography ……………………………………………. 6-29 Regional Distribution and Depositional Trends …………………….. 6-30 Porosity Types and Distribution ………………………………………. 6-31 Black River Group and Platteville Groups …………………………………… 6-31 Lithology and Petrography ……………………………………………. 6-32 Pecatonica Formation ………………………………………… 6-32 Plattin Formation and Equivalents …………………………... 6-33 Regional Distribution and Depositional Trends …………………….. 6-34 Trenton Limestone and Equivalents ………………………………………….. 6-35 Lithology and Petrography ……………………………………………. 6-35 Regional Distribution and Depositional Trends …………………….. 6-36 Porosity Types and Porosity Distribution ……………………………. 6-37 Diagenesis ……………………………………………………………… 6-38 Maquoketa Group ………………………………………………………………. 6-44

iii Lithology and Petrography ……………………………………………. 6-44 …………………………………………………… 6-44 ……………………………………… 6-45 …………………………………………………. 6-46 Regional Distribution and Depositional Trends …………………….. 6-46 Conclusions ……………………………………………………………………... 6-48

CHAPTER 7 Depositional History and Sequence Stratigraphy Introduction ……………………………………………………………………… 7-1 Stratigraphic Sequences ……………………………………………… 7-1 Paleogeography and Climate ………………………………………….7-3 Tectonic Events ………………………………………………………… 7-3 Pre-Mount Simon Deposition ………………………………………………….. 7-4 Sauk Sequence Deposition ……………………………………………………. 7-5 Sauk 1 Subsequence ………………………………………………….. 7-5 Sauk 2 Subsequence ………………………………………………….. 7-7 Sauk 3 and 4 Subsequences …………………………………………. 7-9 Whiterockian Sequence Deposition …………………………………………... 7-10 Lower Tippecanoe Subsequence Deposition ……………………………….. 7-11 Lower Ancell Group ……………………………………………………. 7-11 Upper Ancell and Black River/Platteville Groups …………………… 7-13 Trenton/Galena and Equivalents ……………………………………...7-14 Maquoketa Group ……………………………………………………… 7-15 Conclusions ………………………………………………………………………7-16

CHAPTER 8 Source Rock Evaluation and Burial History Introduction ……………………………………………………………………… 8-1 Data Acquisition ………………………………………………………………… 8-1 Sample Evaluation Methods …………………………………………………... 8-2 Rock-Evaluation Technique …………………………………………... 8-3 Interpretation Guidelines ……………………………………………….8-5 Petrographic Description of Source Material ………………………………… 8-5 Galena Group Kerogenites …………………………………………….8-6 Other Types of Organic Matter ……………………………………….. 8-7 Results of Rock-Evaluation Analyses …………………….………………….. 8-8 Organic Richness ……………………………………………………… 8-8 Maturity (Tmax) …………………………………………………………... 8-11 Hydrocarbon Generation Potential …………………………………… 8-12 Kerogen Types …………………………………………………………. 8-13 Kinetics ………………………………………………………………….. 8-15 Hydrocarbon Generation Modeling …………………………………………... 8-16 Regional Erosion ………………………………………………………..8-16 Local Erosion …………………………………………………………… 8-20 Burial History Reconstructions ……………………………………….. 8-21 Conclusions ………………………………………………………………………8-26

iv CHAPTER 9 Exploration Concepts Introduction …………………………………………………………...... ………..9-1 Sauk 1 Subsequence …………………………………………………………... 9-1 Mount Simon Sandstone …………………………………………….... 9-2 Upper Eau Claire Formation ………………………………………….. 9-3 Sauk 2 and 3 Subsequences ………………………………………………….. 9-5 Sauk 4 Subsequence …………………………………………………………... 9-6 Whiterockian Sequence ………………………………………………………... 9-8 Lower Tippecanoe Sequence …………………………………………………. 9-9 St. Peter Sandstone …………………………………………………… 9-10 Upper Ancell Group ……………………………………………………. 9-12 Trenton/Galena Carbonates ………………………………………….. 9-13 Limestones with Interparticle Porosity ……………………………….. 9-13 Dolomites with Intercrystalline and Vuggy Porosity ………………… 9-15 Fracture-Related Vuggy Dolomites …………………………………...9-16 Conclusions ………………………………………………………………………9-17

BIBLIOGRAPHY Bibliography ……………………………………………………………………………… B-1

APPENDIXES

Appendix 1. Explanation of Lithologic Analyses and Fluid Saturation Calculations for Key Well Panels ……………………………………………………. A-1

Appendix 2. Rock-Evaluation Data …………………………………………………... A-20

Appendix 3. Sample Data Set for BasinMod Source Rock Modeling ……………. A-22

Appendix 4. Results of Kinetics Analyses: Samples IL13 and IL37 ………………. A-32

Appendix 5. Study Wells Productive from Cambro-Ordovician Strata ……………. A-41

Appendix 6. Study Wells with Core and Cuttings Oil Shows ………………………. A-42

Appendix 7. Drillstem Tests of Cambro-Ordovician Strata for Study Wells ……… A-44

v LIST OF FIGURES

SUMMARY

Figure S.1. Map showing the counties included in the GDI study area. The inset map shows the position of the Illinois Basin and the arches, which separate it from other Midcontinent basins.

Figure S.2. Locations of all wells used in building the stratigraphic database for the Cambro- Ordovician rocks of the Illinois Basin.

Figure S.3. Location of the Reelfoot Rift. A) Shaded area represents the location of the "New Madrid Rift Complex" as originally proposed by Braile et al (1982) and Sexton et al (1986). B) Updated interpretation of the northern end of the Reelfoot Rift.

Figure S.4. Relative timing of structural movement on many of the major features in and around the Illinois Basin.

Figure S.5. Isopach map of the entire Sauk Sequence from the top of the Shakopee Dolomite to Precambrian basement.

Figure S.6. Coastal onlap curve for the Illinois Basin region tied to the stratigraphic nomenclature for Illinois and the subsequences discussed in this report.

Figure S.7. Isopach map of the Everton (Whiterockian Sequence) in the Illinois Basin.

Figure S.8. Isopach map of the lower Tippecanoe and Whiterockian sequences.

Figure S.9. Comparison of stratigraphic nomenclature in current usage for the lower Tippecanoe Sequence and the GDI stratigraphic markers defined for this study.

Figure S.10. West to east cross section illustrating the relationship between the Trenton Limestone and Lexington Limestone across the shale-filled Sebree Trough.

Figure S.11. Regional lithologic and depositional trends for the Maquoketa Group.

Figure S.12. Schematic cross sections illustrating Early and Middle Cambrian rift basin stratigraphy and inferred facies relationships.

Figure S.13. Contoured map of the distribution of total organic carbon (TOC in %) for the samples analyzed from the Maquoketa Group.

Figure S.14. Contour map of Tmax values for the Maquoketa samples illustrating that the highest values are centered around Hicks Dome in southern Illinois.

Figure S.15. Contour map of net erosion based on calculations using coal moisture data from Damberger (1971).

Figure S.16. Burial history reconstructions for shallow and deep wells in the study area.

vi Figure S.17. Plots of cumulative hydrocarbon generation (mg/g TOC) for the same shallow and deep wells shown in Figure S.16.

Figure S.18. Map of cumulative hydrocarbon generation (BO/Acre-Foot) for the Maquoketa Group using actual measured TOC values for selected wells.

Figure S.19. Maps of cumulative hydrocarbon generation (BO/Acre-Foot) using values obtained elsewhere in the study area.

CHAPTER 1: INTRODUCTION

Figure 1.1. Generalized distribution of pre-Silurian oil and gas fields in and around the Illinois Basin.

Figure 1.2. Locations of Ordovician oil fields in the Illinois Basin.

Figure 1.3. Map showing the counties included in the GDI study area. The inset map shows the position of the Illinois Basin and the arches, which separate it from other Midcontinent basins.

Figure 1.4. Map showing general outlines for the Illinois Basin.

Figure 1.5. Illustrations showing important aspects of the Illinois Basin.

Figure 1.6. Coastal onlap curve for the Paleozoic (as defined by Vail et al, 1977) tied to a generalized stratigraphic section for southwestern Indiana near the center of the Illinois Basin.

Figure 1.7. Generalized distribution of Silurian reefs as mapped by Droste and Shaver (1980) who recognized a "hingeline" trend wrapping around the north end of the Illinois Basin.

Figure 1.8. "Type" log (Buttercup #1 Pensinger) showing the stratigraphic markers used and correlated by GDI in this study of the Cambro-Ordovician section in the Illinois Basin.

Figure 1.9. Example of the stratigraphic data sheet used to record formation tops and other information during this study showing GDI's alphanumeric codes.

Figure 1.10. Locations of the regional cross sections used by GDI to correlate the various Cambro-Ordovician stratigraphic units across the Illinois Basin.

Figure 1.11. Locations of all wells used in building the stratigraphic database for the Cambro- Ordovician rocks of the Illinois Basin.

Figure 1.12. Locations of the 9 wells selected for use in generating "key well panels."

Figure 1.13. Locations of the wells from which cores were described by GDI geologists for this study are indicated with a black dot and the well name.

vii CHAPTER 2: EXPLORATION HISTORY

Figure 2.1. Histogram showing number of well completions by decade for wells in the GDI database.

Figure 2.2. Generalized structure map drawn on the top of the Trenton Limestone showing oil and gas production trends in the Trenton, Lima, and Findlay fields as of 1887.

Figure 2.3. Histogram showing four stages in the history of oil production in Indiana.

CHAPTER 3: REGIONAL SETTING AND STRUCTURAL HISTORY

Figure 3.1. Map of U. S. Midcontinent region showing the position and structure of the Illinois Basin relative to nearby basins.

Figure 3.2. Generalized map showing Precambrian basement provinces in the central United States.

Figure 3.3. Location of the Reelfoot Rift. A) Shaded area represents the location of the "New Madrid Rift Complex" as originally proposed by Braile et al (1982) and Sexton et al (1986). B) Updated interpretation of the northern end of the Reelfoot Rift reflecting the ideas of Nelson (1990) who noted that seismic data fail to support the interpretation of a trifurcated rift complex.

Figure 3.4. Generalized paleogeographic reconstruction of the Illinois Basin area in Late Precambrian time showing inferred drainages, basement paleohighs, inferred wind direction, and so on.

Figure 3.5. Locations of important structural features in and around the Illinois Basin. Structural trends adapted from Treworgy (1981) and Schwalb (1982b).

Figure 3.6. Schematic diagram of the Illinois Basin area during Late Cambrian time. The Reelfoot Rift is by this time a subsiding embayment open to the ocean to the south.

Figure 3.7. Isopach maps of Middle Ordovician (Champlainian) sediment thicknesses in feet. Parts A and B were generated based on lithospheric flexure models of Beaumont et al (1988) and show predicted thicknesses at the time of deposition and at present.

Figure 3.8. Isopach maps of Upper Ordovician (Cincinnatian) sediment thicknesses in feet. Parts A and B were generated based on lithospheric flexure models of Beaumont et al (1988) and show predicted thicknesses at the time of deposition and at present.

Figure 3.9. Generalized paleogeographic reconstruction of the Illinois Basin area in Late Ordovician (Trenton-Galena) time showing the widespread carbonate platform present throughout most of the area.

Figure 3.10. Generalized paleogeographic reconstruction of the Illinois Basin area in Late Silurian time showing the early formation of the Illinois Basin.

Figure 3.11. Isopach map of the New Albany Group and equivalents in the Illinois Basin area.

viii

Figure 3.12. Generalized paleogeographic reconstruction of the Illinois Basin area in Late Pennsylvanian time showing areas of uplift (e.g., LaSalle Anticlinal Belt), inferred drainages, and reactivation of the Reelfoot Rift due to continental collisions at the plate margin.

Figure 3.13. Generalized subcrop map for the Pascola Arch.

Figure 3.14. Relative timing of structural movement on many of the major features in and around the Illinois Basin.

Figure 3.15. Sequence of maps showing the structural history of the Illinois Basin area.

Figure 3.16. Global reconstruction for Late Cambrian and Late Ordovician time showing the position of the North American plate lying astride the equator with the Illinois Basin study area at about 15° South latitude. Adapted from Scotese and McKerrow (1990).

CHAPTER 4: STRATIGRAPHY OF THE SAUK SEQUENCE

Figure 4.1. Isopach map of the entire Sauk Sequence from the top of the Shakopee Dolomite to Precambrian basement.

Figure 4.2. Coastal onlap curve for the Illinois Basin region tied to the stratigraphic nomenclature for Illinois and the subsequences discussed in this report.

Figure 4.3. North to south schematic cross section showing the stratigraphic relationships of the various Cambro-Ordovician rock units from northeastern Wisconsin south along the Mississippi River into Tennessee.

Figure 4.4. North to south cross section showing the relative thicknesses of the various stratigraphic intervals within the Sauk Sequence.

Figure 4.5. Schematic reconstruction of a composite measured section for the lower part of the Sauk Sequence as seen in outcrops in southern and central Wisconsin.

Figure 4.6. Outcrops of the Sauk 1 subsequence in Wisconsin.

Figure 4.7. Representative wireline logs for the Texaco #1 Johnson showing the log characteristics of the Cambro-Ordovician section studied.

Figure 4.8. Isopach map of the Mount Simon Sandstone and older sedimentary rocks showing the marked thickening of this section into the sag south of the Rough Creek Fault Zone associated with the Reelfoot Rift/Rough Creek Graben.

Figure 4.9. Outcrops of the Sauk 2 subsequence in Wisconsin.

Figure 4.10. Representative wireline logs for the Buttercup #1 Pensinger showing the log characteristics of the Cambro-Ordovician section in Indiana.

ix Figure 4.11. Isopach map of the Eau Claire "clastic unit" (E200-MTSM interval) in the lower part of the formation.

Figure 4.12. Regional cross section showing stratigraphic relationships southward through Indiana into the Rough Creek Graben.

Figure 4.13. Isopach map of the upper part of the Eau Claire Formation (E100-E200 interval) including both of the carbonate units.

Figure 4.14. Schematic reconstruction of a composite measured section for the middle and upper parts of the Sauk Sequence as seen in outcrops in southern and central Wisconsin.

Figure 4.15. Isopach map of the Late Cambrian Sauk 2 subsequence, which extends from the base of the Galesville Sandstone to the top of the Potosi Dolomite.

Figure 4.16. North to south regional cross section showing stratigraphic relationships in the Sauk 2 subsequence.

Figure 4.17. Lithologies for the uppermost part of the Sauk 1 subsequence and lower part of the Sauk 2 subsequence are plotted here on the wireline log of a well drilled near the crest of the Kankakee Arch.

Figure 4.18. Isopach map of the Galesville and fronton sandstone interval at the base of the Sauk 2 subsequence.

Figure 4.19. Isopach map of the Davis Formation showing the southward thinning and disappearance of this siliciclastic interval.

Figure 4.20. Isopach map of the Knox Group showing that this interval thickens significantly from less than 1000 feet to the northwest to more than 6000 feet in the sag associated with the Reelfoot Rift.

Figure 4.21. Isopach map of the Sauk 3 subsequence including the Oneota Dolomite and Gunter (=Jordan) Sandstone.

Figure 4.22. Outcrops of the Sauk 3 subsequence in Wisconsin and Minnesota.

Figure 4.23. Representative wireline logs for the Northern Illinois Gas #2 Cullen showing the distinctive character of the Jordan or Gunter Sandstone between the Oneota and Potosi dolomites.

Figure 4.24. Carbonates of the Sauk 3 and Sauk 4 subsequences in Wisconsin and Minnesota.

Figure 4.25. Schematic reconstruction of a composite measured section for the uppermost part of the Sauk Sequence and the lower (Ordovician) part of the overlying Tippecanoe Sequence as seen in outcrops in southern and central Wisconsin.

Figure 4.26. Isopach map of the Sauk 4 subsequence.

x Figure 4.27. Log response of the New Richmond Sandstone at the base of the Sauk 4 subsequence.

Figure 4.28. Isopach map of the New Richmond Sandstone. This siliciclastic interval thins southward and pinches out in the northern part of the study area.

Figure 4.29. Outcrops of the Sauk 4 subsequence.

Figure 4.30. Wireline log of the Shakopee Dolomite showing the thick, porous quartz sandstones that occur locally within the formation in the eastern part of the study area.

CHAPTER 5: STRATIGRAPHY OF THE WHITEROCKIAN AND LOWER TIPPECANOE SEQUENCES

Figure 5.1. Comparison of stratigraphic nomenclature in current usage and the GDI stratigraphic markers defined for this study.

Figure 5.2. Isopach map of the lower Tippecanoe and Whiterockian sequences.

Figure 5.3. Representative wireline log showing the nature of the contacts of the Everton with the underlying Knox Group (Shakopee Dolomite) and overlying St. Peter Sandstone.

Figure 5.4. Isopach map of the Everton (Whiterockian Sequence) in the Illinois Basin.

Figure 5.5. Schematic north to south cross section showing lithologic and stratigraphic relationships between rocks of the Whiterockian and lower Tippecanoe sequences.

Figure 5.6. Cross section through the Illini Development #3 Alderson well showing the unusually thick sections of the Everton and St. Peter encountered in that well.

Figure 5.7. Regional distribution of the St. Peter Sandstone.

Figure 5.8. Correlation of markers within the Ancell Group between the #C-17 Ford well (for which nearly continuous core is available) and the #1 Ford-Corbin.

Figure 5.9. Isopach map of the St. Peter Sandstone. As defined by GDI this is actually a sandstone isolith map of the basal siliciclastic interval of the Ancell Group.

Figure 5.10. Schematic cross section showing the relationships of the St. Peter Sandstone and the "pseudochronostratigraphic" markers defined by GDI within the Ancell Group.

Figure 5.11. Isopach map of the A400-St. Peter interval showing the thinning of this part of the Ancell Group to the north and east.

Figure 5.12. Isopach map of the A300 to A400 interval, approximately equal to the Dutchtown Formation, showing the very gradual thickening of this portion of the Ancell Group to the south.

xi Figure 5.13. West to east cross section showing the uniformity of deposition during Pecatonica time as opposed to the marked changes in thickness represented by the underlying rocks of the Ancell.

Figure 5.14. Isopach map of the A200-A300 interval in the Ancell Group showing the gradual thickening of these rocks to the south.

Figure 5.15. Isopach map of the entire Ancell Group from the top of the Joachim (A100 marker) to the top of the Everton (or Shakopee) Dolomite.

Figure 5.16. Isopach map of the Pecatonica Limestone (B700-A100 interval) showing the very gradual thickening of these rocks southward into the Rough Creek Graben.

Figure 5.17. West to east correlation of the Trenton Limestone (Galena Group in Illinois) and Black River Limestone (Platteville Group in Illinois) between the GDI Illinois and Indiana type logs.

Figure 5.18. Correlation of the Millbrig and Deicke K-bentonites from a well in eastern Missouri (as defined by Kolata et al, 1986) with GDI's B100 and B200 markers in a well on the eastern side of the Illinois Basin.

Figure 5.19. Isopach map of the Black River Limestone (Platteville Group in Illinois).

Figure 5.20. West to east cross section illustrating the relationship between the Trenton Limestone and Lexington Limestone across the shale-filled Sebree Trough.

Figure 5.21. Isopach map of the Trenton Limestone (Galena Group in Illinois; Lexington Limestone in west-central Kentucky).

Figure 5.22. Generalized map showing paleogeography and lithofacies in the eastern United States during deposition of the Lexington Limestone relative to the GDI study area in the Illinois Basin.

Figure 5.23. Two-well cross section showing the relationship of the Maquoketa Group and underlying carbonates in Illinois to a representative well drilled on the southeast flank of the Sebree Trough.

Figure 5.24. Isopach map of the Maquoketa Group showing the approximate position of the Sebree Trough.

Figure 5.25. Regional schematic cross section of the Maquoketa Group showing the nature of the thinning to the west.

CHAPTER 6: LITHOLOGY, PETROGRAPHY, AND PORE TYPES

Figure 6.1. Distribution of cores described by GDI geologists for this study.

Figure 6.2. Stratigraphic distribution of the cores described for this study.

xii Figure 6.3. A) Map showing distribution of the three Mount Simon cores (stars) described for this study. B) Representative core description for the Mount Simon Sandstone.

Figure 6.4. A) Regional distribution of the dominant cements in the Mount Simon Sandstone as mapped by Hoholick et al (1984). B) Regional distribution of secondary pore types in the Mount Simon as mapped by Hoholick et al (1984).

Figure 6.5. Paleogeographic and depositional trends in the GDI study area during Mount Simon time.

Figure 6.6. Core descriptions of the lowermost Eau Claire Formation and its contact with the underlying Mount Simon Sandstone.

Figure 6.7. Log to core comparison of the "Upper Shaly" (E130-E150) interval and the associated upper and lower carbonates in the upper Eau Claire section for the #S-5 Baer well located on St. Jacob Dome.

Figure 6.8. Fence diagram showing regional distribution of the different ooid-rich zones in the Eau Claire Formation and stratigraphic relationships of the overlying Davis Formation with the Galesville, Ironton, and Franconia formations to the north.

Figure 6.9. Regional depositional trends in the lower Eau Claire Formation throughout the GDI study area.

Figure 6.10. Lithologic and depositional trends in the upper part of the Eau Claire Formation (the Eau Claire carbonate interval).

Figure 6.11. Log to core comparison for the Davis Formation in the #S-2 Klein well located in Madison County, Illinois on the west side of the study area (location shown on inset map).

Figure 6.12. Generalized lithologic trends in the Davis Formation throughout the GDI study area.

Figure 6.13. Location of Knox cores examined during this study are shown on this generalized lithology map of the Knox Group.

Figure 6.14. Representative core descriptions of each of the three major dolomite formations within the Knox Group. A) Basal contact of the Knox Group (Potosi Dolomite) with the underlying Davis Formation. This part of the section suggests a single shallowing upward depositional cycle about 25 feet thick. B) Core description of the Oneota Dolomite as seen in the #1 Pensinger well (Clay Co., IN) showing dominant dolomite mudstone lithology. C) Core description of the uppermost Knox Group (Shakopee Dolomite) and its contact with the overlying St. Peter Sandstone.

Figure 6.15. Core description of the contact between the Oneota and Shakopee formations on the west flank of the Illinois Basin.

Figure 6.16. Core descriptions for the two study wells which provided Everton cores used in this study.

xiii Figure 6.17. Generalized lithologic trends within the Everton Dolomite.

Figure 6.18. A) Distribution of St. Peter Sandstone cores. B) The St. Peter core from the Cabot #1 Cabot well is typical of the formation.

Figure 6.19. Distribution of dominant cements and secondary pore types in the St. Peter Sandstone of Illinois from Hoholick et al (1984).

Figure 6.20. The St. Peter Sandstone is an irregular sheet of sandstone that is markedly thinner in the eastern part of the study area and is absent from central Kentucky.

Figure 6.21. A) Distribution of Dutchtown Formation cores. B) The Superior #C-17 Ford core was considered to be the "type" Atwell Group section for this study.

Figure 6.22. A) Distribution of Joachim Dolomite cores. B) Portions of Joachim Formation from the Superior #C-17 Ford core.

Figure 6.23. Distribution of anhydrite within the Joachim Dolomite.

Figure 6.24. A) Distribution of Black River and Platteville Group cores. B) Portion of the Black River Group from the Mobile. Drilling Co. #1 Mobile Drilling core illustrating the dominance of lime mudstone in these formations.

Figure 6.25. Lithology trends of the Black River and Platteville Group.

Figure 6.26. A) Distribution of Trenton and Galena Group cores. B) Representative Galena Group rocks described in the Mississippi River Fuel #A-4 Kolmer core.

Figure 6.27. Lithology trends of the Trenton Limestone and equivalents.

Figure 6.28. Generalized paragenetic sequence of diagenetic events that have affected the Trenton Limestone in the GDI study area.

Figure 6.29. A) Distribution of Maquoketa Group cores. B) Representative Maquoketa Group rocks described in the Miller #1 Sample core.

Figure 6.30. A) Maquoketa Group correlation between the #1 Sample, Sangamon County, Illinois and the #1 Mobile Drilling, Marion County, Indiana. B) Portions of the Maquoketa Group rocks in the Mobile Drilling Co. #1 Mobile Drilling core.

Figure 6.31. Maquoketa Group lithology and depositional trends.

Figure 6.32. Map illustrating the location of the Sebree Trough and differential thickening of the Maquoketa that infills this feature.

Figure 6.33. Maquoketa Group lithology distributions as described by Du Bois (1945) for the A) upper Maquoketa, B) middle Maquoketa, and C) lower Maquoketa.

xiv LIST OF PETROGRAPHY PHOTO PLATES

Plate 1. Basal Cambrian Deposits.

Plate 2. Mount Simon Sandstone

Plate 3. Diagenesis of Mount Simon Sandstone

Plate 4. Eau Claire Formation

Plate 5. Eau Claire Carbonates

Plate 6. Eau Claire Porosity

Plate 7. Davis Formation

Plate 8. Potosi Dolomite

Plate 9. Oneota Dolomite

Plate 10. Oneota Dolomite (cont.)

Plate 11. Shakopee Dolomite

Plate 12. Shakopee Dolomite (cont.)

Plate 13. Porosity in Shakopee Dolomite

Plate 14. Porosity in Shakopee Dolomite (cont.)

Plate 15. Everton Dolomite

Plate 16. St. Peter Sandstone

Plate 17. St. Peter Sandstone (cont.)

Plate 18. Porosity in St. Peter Sandstone

Plate 19. Updip St. Peter Sandstone

Plate 20. Dutchtown Type Section and Joachim Outcrop

Plate 21. A300 Interval (Dutchtown Equivalent)

Plate 22. A200 Interval (Ancell Group)

Plate 23. A100 Interval (Joachim Equivalent)

Plate 24. Black River Group – Indiana

Plate 25. Platteville Group – Illinois

xv

Plate 26. Textures in Black River/Platteville Group

Plate 27. Trenton Limestone – Indiana

Plate 28. Galena Group – Illinois

Plate 29. Galena Group - Illinois (cont.)

Plate 30. Porosity in Trenton/Galena

Plate 31. Diagenetic Textures in Trenton/Galena

Plate 32. Maquoketa Group - Scales Shale

Plate 33. Scales Shale and Fort Atkinson Limestone

Plate 34. Fort Atkinson Limestone and Brainard Shale

CHAPTER 7: DEPOSITIONAL HISTORY AND SEQUENCE STRATIGRAPHY

Figure 7.1. Lithologic sequence and relative sea level curve for Cambro-Ordovician deposition in the Illinois Basin.

Figure 7.2. Schematic cross sections illustrating Early and Middle Cambrian rift basin stratigraphy and inferred facies relationships.

Figure 7.3. Distribution of the dominant lithologies in the Cambrian formations of the northern Mississippi Embayment as reconstructed by Houseknecht (1989).

Figure 7.4. Regional isopach map of Upper Cambrian strata east of the Transcontinental Arch.

Figure 7.5. Map of the four depositional provinces, which compose the Sauk 1 subsequence.

Figure 7.6. Portion of a west to east regional seismic line across the Sparta Shelf region in western Illinois.

Figure 7.7. Regional isopach map of the Potosi Dolomite and equivalents across the northern Midcontinent.

Figure 7.8. Depositional provinces of the Sauk 2 subsequence.

Figure 7.9. Depositional provinces of the Sauk 4 subsequence.

Figure 7.10. Portion of regional seismic line across a part of the Rough Creek Graben in western Kentucky.

Figure 7.11. The lateral extent of the St. Peter Sandstone and A400 interval define three depositional provinces for the lower Ancell Group.

xvi Figure 7.12. Two depositional provinces of the upper Ancell and Black River/Platteville Groups are distinguished based on the extent of evaporitic deposits in the Joachim (A100 and A200 intervals).

Figure 7.13. Isopach map of Black River Group and equivalents across the Midcontinent region.

Figure 7.14. Depositional provinces of the Trenton Limestone and equivalents.

CHAPTER 8: SOURCE ROCK EVALUATION AND BURIAL HISTORY

Figure 8.1. Distribution of samples selected for Rock-Evaluation analysis.

Figure 8.2. Examples of kerogenite beds in the Galena Group.

Figure 8.3. More examples of kerogenite beds in the Galena Group and Trenton Limestone of the Illinois Basin.

Figure 8.4. Examples of organic matter in the Maquoketa Group.

Figure 8.5. Examples of other rocks analyzed by Rock-Evaluation to document the hydrocarbon source potential of pre-Galena section in the Illinois Basin.

Figure 8.6. Contoured map of the distribution of total organic carbon (TOC in %) for the samples analyzed from the Maquoketa Group.

Figure 8.7. Map showing areas of high organic richness (TOC >3%) for the Maquoketa Group superimposed upon the Maquoketa isopach map.

Figure 8.8. Contoured map of the distribution of total organic carbon (TOC in %) for the Galena Group/Trenton Limestone.

Figure 8.9. Overlay of areas rich in total organic carbon (TOC >5%) for the Galena Group/Trenton Limestone on the isopach map of these intervals.

Figure 8.10. Distribution of organic richness (percent TOC) for the Ancell Group based on the limited number of samples analyzed.

Figure 8.11. Distribution of organic richness (percent TOC) for the Knox and Davis intervals based on the limited number of samples analyzed.

Figure 8.12. Distribution of organic richness (percent TOC) for the Eau Claire Formation based on the limited number of samples analyzed.

Figure 8.13. Crossplots of Tmax versus depth. A) Plot of Tmax versus depth for all samples analyzed by Rock-Evaluation for this study. B) Plot of Tmax versus depth for all of the samples of Maquoketa Group shales selected for Rock-Evaluation analysis.

Figure 8.14. Contour map of Tmax values for the Maquoketa samples illustrating that the highest values are centered around Hicks Dome in southern Illinois.

xvii

Figure 8.15. Overlay of Maquoketa Tmax. values on top of Galena Group/Trenton Limestone structure map.

Figure 8.16. Crossplots of S1 versus various Rock-Evaluation data for the Maquoketa samples. A) Crossplot of Tmax versus S1. B) Crossplot of depth versus S1.

Figure 8.17. Contoured map of S1 distribution for the Maquoketa Group.

Figure 8.18. Crossplots of S2 and hydrogen index versus other Rock-Evaluation data for the Maquoketa samples.

Figure 8.19. Contoured map of the hydrogen indices (HI) for the Maquoketa Group samples in the study area.

Figure 8.20. Variation of the transformation ratio or production index (PI) with depth (= increasing maturity). After Espitalie (1977).

Figure 8.21. Transformation ratio plots for the Maquoketa samples. A) Crossplot of Tmax versus the transformation ratio (production index). B) Crossplot of depth versus transformation ratio (production index).

Figure 8.22. Comparison of Van Krevelen (kerogen type) diagrams using atomic ratios and hydrogen/oxygen indices as defined by Tissot and Welte (1978) and Espitalie (1977).

Figure 8.23. Van Krevelen diagram for the Maquoketa samples.

Figure 8.24. Van Krevelen diagram of Mid-Ordovician kerogen type assemblages A (platy) and B (fluffy) illustrating the mixed occurrence of both types I and II in these samples from wells in Iowa (after Jacobson et al, 1988).

Figure 8.25. Core-to-log comparison of Mississippi River Fuel #A-4 Kolmer designed to show the log characteristics of the kerogenite sample IL17.

Figure 8.26. Core-to-log comparison of the Pan American #2 Heltonville well for the kerogenite- bearing interval which yielded sample IL37.

Figure 8.27. Various crossplots of Rock-Eval data for the Trenton/Galena. A) Crossplot of Tmax versus depth showing a scatter of points similar to that seen for the Maquoketa samples. B) Van Krevelen diagram showing the presence of type I kerogens as indicated by the high hydrogen index values. C) Crossplot of Tmax versus S1.

Figure 8.28. Various crossplots of Tmax versus other Rock-Evaluation data for the Trenton/ Galena samples. A) Crossplot of Tmax versus S2. B) Crossplot of Tmax versus hydrogen index. C) Crossplot of Tmax versus transformation ratio or production index (PI).

Figure 8.29. Diagrams showing distribution of activation energies for kinetics sample 1L13 from the Maquoketa (Miller #1 Sample, Sangamon County, Illinois) and IL37 from the Trenton (Pan American #2 Heltonville, Lawrence County, Indiana).

xviii Figure 8.30. A) Coal moisture iso-rank lines for the Herrin #6 Coal in Illinois. B) Relationship of depth to coal moisture content. This curve indicates that over 5000 feet more erosion has occurred in southern Illinois than northern Illinois. Both figures from Damberger (1971).

Figure 8.31. Graph showing relationship of coal moisture content and depth of burial based on study of Cretaceous and Tertiary coals in Canada.

Figure 8.32. Contour map of net erosion based on calculations using coal moisture data from Damberger (1971).

Figure 8.33. Graph of compaction curves from Baldwin and Butler (1985).

Figure 8.34. Semi-log crossplot of sonic transit time versus depth for the Maquoketa.

Figure 8.35. Map of net erosion calculated from Baldwin-Butler (1985) equation.

Figure 8.36. Plot of calculated thermal maturity versus depth for the Miller #1 Sample in Sangamon County, Illinois.

Figure 8.37. Burial history reconstruction for the Miller #1 Sample well in Sangamon County, Illinois.

Figure 8.38. Plot of calculated Ro% maturity versus time for the Maquoketa and Trenton samples in the Miller #1 Sample well.

Figure 8.39. Plot of cumulative hydrocarbon generation (mg/g TOC) and the transformation ratio versus time for the Maquoketa Group in the Miller #1 Sample.

Figure 8.40. Plot of calculated maturity versus depth for the Texas Pacific #1 Streich in Pope County, southern Illinois.

Figure 8.41. Burial history plot for the Texas Pacific #1 Streich in Pope County, Illinois.

Figure 8.42. Plot of cumulative hydrocarbon generation (mg/g TOC) and transformation ratio versus time for the Texas Pacific #1 Streich.

Figure 8.43. Map of cumulative hydrocarbon generation (BPAF) for the Maquoketa Group using actual measured TOC values for selected wells.

Figure 8.44. Map of cumulative hydrocarbon generation (BPAF) for the Maquoketa using assumed immature value of 6.61% TOC (as measured in the Miller #1 Sample).

Figure 8.45. Map of cumulative hydrocarbon generation (BPAF) for the Trenton using assumed immature value of 14.39% TOC (as measured in the Pan American #2 Heltonville).

Figure 8.46. Map showing heat flow values used in burial history reconstructions for selected wells.

xix Figure 8.47. Plots of cumulative hydrocarbon generation (mg/g TOC) and transformation ratios against time for deeper horizons in the Texaco #1 Cuppy well in Hamilton County, Illinois.

Figure 8.48. Plots of cumulative hydrocarbon generation (mg/g TOC) and transformation ratios against time for deeper horizons in the Texas Pacific #1 Streich well, Pope County, Illinois.

CHAPTER 9: EXPLORATION CONCEPTS

Figure 9.1. Portion of a seismic section in southern Illinois showing a probable uplifted fault block on which porosity may be developed at the top of the Knox Group, and possibly in other horizons as well.

Figure 9.2. Isochron map of St. Peter Sandstone formation waters showing the rapid increase in salinity toward the deeper parts of the basin.

Figure 9.3. Types and regional distribution of Trenton/Galena reservoirs found in the Midcontinent region.

xx LIST OF MAPS, CROSS SECTIONS AND KEY WELL PANELS

Maps

Well Identification Production and Hydrocarbon Show Structure: Top of Trenton/Galena/Lexington Maquoketa Group Isopach Trenton/Galena/Lexington Isopach St. Peter Sandstone Isopach Everton Dolomite Isopach Knox Group Isopach Davis Formation Isopach Eau Claire "Buttercup Oolite" Isopach Eau Claire "Clastic Unit" Isopach

Regional Cross Sections

A-A' 2 Panels B-B' 2 Panels C-C' 3 Panels W-W' 2 Panels X-X' 2 Panels Y-Y' 2 Panels

Key Well Panels

Illinois: Beeson #1 Poiter Texaco #1 Cuppy Texaco #1 Johnson Texas Pacific #1 Farley Union #1 Cisne

Indiana: Buttercup #1 Pensinger

Kentucky: Exxon #1 Duncan Sun #1 Stephens Texas Gas Transmission #1 Shain

xxi Cambro-Ordovician Study of the Illinois Basin

Selected Figures from the Study

Figure S.12. Schematic cross sections illustrating Early and Middle Cambrian rift basin stratigraphy and inferred facies relationships. A) Cambro-Ordovician stratigraphy and lithology of southern Illinois as interpreted by Schwalb (1982c). B)Asimilar transect from Houseknecht (1989) showing alluvial fan and braided fluvial deposits of the Reelfoot Arkose fill the rift basin overlain by marine deposits of the St. Francis Formation and Lamotte Sandstone (= Mount Simon). The carbonate shelf of the Bonneterre formed above these clastic deposits.

Return to Text Figure 3.4. Generalized paleogeographic reconstruction of the Illinois Basin area in Late Precambrian time showing inferred drainages, basement paleohighs, inferred wind direction, and so on. Letters and symbology are explained in the legend on the previous page along with a location map showing the GDI study area within the area shown in the perspective block diagram.

Return to Text Plate 3A. #S-5 Baer, 4858 ft., Madison Co., Illinois. Thinsection photomicrograph of granite wash from St. Jacob Dome (cf. with photo of core slab in Plate 1C) showing dolomite cement between the rock fragments. Partial leaching of the potassium feldspar, which is stained brownish in the granite rock fragment (center), has left open pores that are filled with blue epoxy in this thinsection.

Plate 3B. Outcrop Sample, Lamotte Sandstone, Hwy 72, Madison Co., Missouri. This thinsection photomicrograph of the Lamotte (=Mount Simon) Sandstone contains embayed and euhedral volcanic quartz grains apparently derived from a nearby rhyolite (similar to that shown in Plate 1B). The rock is tightly cemented with dolomite as is the granite wash resting on basement at St. Jacob Dome (as shown inPlate 1C ). Rock fragments and stained feldspar grains are also present in the dolomite cement. Return to Text Page 6-3 Return to Text Page 6-5 Diagenesis of Mount Simon Sandstone Continued on Next Page Figure 6.8. Fence diagram showing regional distribution of the different ooid-rich zones in the Eau Claire Formation and stratigraphic relationships of the overlying Davis Formation with the Galesville, Ironton, and Franconia formations to the north. Diagram from Becker et al (1978, p. 22).

Return to Text Example of a Core Description