sign in sign up
<<
Home , Backbone Limestone, Bailey Limestone, Brassfield Formation, Chouteau Limestone, Clear Creek Chert, Dalmanites

flU^S^^^M 57 IL6b

). 101 u^w^OGY OF THE JONESBORO 15-MINUTE QUADRANGLE, SOUTHWESTERN

Jonesboro, Mill Creek, Ware, and McClure 7.5-Minute Quadrangles

W. John Nelson, Joseph A. Devera, and John M. Masters

Department of Natural Resources ILLINOIS STATE GEOLOGICAL SURVEY OCT % 9 1996 BULLETIN 101 1995 LIBRARY. Y

GEOLOGY OF THE JONESBORO 15-MINUTE QUADRANGLE, SOUTHWESTERN ILLINOIS

Jonesboro, Mill Creek, Ware, and McClure 7.5-Minute Quadrangles

W. John Nelson, Joseph A. Devera, and John M. Masters

BULLETIN 101 1995 -» » «^ a n\f ILLINOIS STATE GEOLOGICAL SURVEY William W. Shilts, Chief OCT 2 9 799g 615 East Peabody Drive

Champaign, IL 61820-6964 I u ~ ^ ~^ ^ otiVE ACKNOWLEDGMENTS This study was supported by the U.S. Geological Survey, Department of the Interior, under Assistance Award No. 14-08-0001 -A0891. Additional funding was provided by the State of Illinois under the State Geologic Mapping Initia- tive. Many ideas on the nature and origin of tripoli were gained through dis- cussions with Richard B. Berg, and Richard W. Harrison provided valuable insights on the structural geology and tectonic history from his work in the adjacent Thebes Quadrangle. Dennis R. Kolata and Heinz H. Damberger reviewed the manuscript and provided many helpful comments; technical editing was performed by Bob Wathen, and figures were drafted by Vicki Rinehart. We thank the numerous landowners who allowed us access to their lands for geologic mapping. Special thanks are in order for Harley Rhodes, Harold E. Dillow, Karol L. Hunter, Kenneth D. Rosson, and Clifton More- land, who allowed us to drill stratigraphic test holes on their property. Karl L.

Bartlesmeyer, Bill Stout, Jr., and Dave Eddings of the Illinois Department of Transportation excavated a roadcut for us without charge in an attempt to expose the Iron Mountain Fault.

ILLINOIS

°""""ment Q' Printed by authority of the State of'Illinois/1995/1200 resources ®printed with soybean ink on recycled paper CONTENTS

ACKNOWLEDGMENTS

ABSTRACT 1

SUMMARY 3

INTRODUCTION 5 Purpose 5 Location and Physiography 5 Geologic Setting 5 Previous Studies 5 Methodology 6

STRATIGRAPHY 7 Mt. Simon (Lamotte) 7 Knox Group 7 7 St. Peter Sandstone 7 Dutchtown Formation 7 8 "Pecatonica Formation" 8 Plattin 8 Decorah Formation 9 9 Cape Limestone 9 10 Cape La Croix Shale Member 10 Thebes Sandstone Member 10 Orchard Creek Shale Member 10 Girardeau Limestone Member 11 Leemon Formation 11 11 Bainbridge Formation 12 Seventy-Six Shale Member 12 St. Clair Limestone Member 12 Moccasin Springs Member 14 14 Grassy Knob 15 Clear Creek Formation 15 Unaltered lithology 16 Altered lithology 16 19 Dutch Creek Sandstone Member 19 Unnamed limestone member 19 St. Laurent Formation 20 Unaltered lithology 20 Altered lithology 21 21 24 Springville Shale 24 State Pond Member 25 Upper member 25 Altered lithology 26 26 Unaltered lithology 26 Altered lithology 27 Ullin Limestone 28 29 St. Louis Limestone 30 Ste. Genevieve Limestone 30 Pope Group 31 System 32 (?) 32 McNairy Formation 32 Tertiary System 33

Wilcox Formation (?) 33 System 34 Upland silt and colluvium 34 Alluvial and lacustrine deposits 34

STRUCTURAL GEOLOGY 35 Eastern Homoclinal Area 35 Western Homoclinal Area 35 Harrison Creek Anticline 35 Major Faults 35 Atwood Fault 35 Delta Fault 37 Cape Road Fault 37 "Thumb Area" 38 Altered Area 38 Extent 39 Nature of alteration 39 Faults 39 Folds 41 Joints and clastic dikes 41 Causes of alteration 42 Post-Cretaceous Faulting 44 Summary 46

GEOLOGIC HISTORY 47 47 47 47 48 Late Mississippian through Early Cretaceous 48 Cretaceous and Tertiary 48

ECONOMIC GEOLOGY 50 Silica 50 Limestone 51 Clay and Shale 51 Oil and Gas 51 Fluorite and Metallic Ores 52

REFERENCES 54

FIGURES 1 Location map, showing study area (shaded), adjacent quadrangles, and major structural features 4

2 Stratigraphic column, showing Middle and Upper Ordovician units (except Leemon Formation) in the study area 6

3 Sexton Creek Limestone and St. Clair Limestone Member of Bainbridge Formation, north of the mouth of Dongola Hollow 12

4 Sexton Creek Limestone, showing the numerous closely fractured chert layers 13

5 Stratigraphic column, showing Silurian and Devonian units in the study area 13

6 Man-made exposure of the Clear Creek Formation 16 1

7 Abandoned underground silica mine in white tripoli of Clear Creek Formation 17

8 Ledge-forming chert of Clear Creek Formation 18

9 Contact of Dutch Creek Sandstone (above) to Clear Creek Formation 18

10 Breccia ted Dutch Creek Sandstone, consisting of angular sandstone clasts cemented by silica and iron oxide 19

1 Chart showing development of lithostratigraphic classification of Middle and Upper Devonian strata in southwestern Illinois 20

12 Graphic columns illustrating the lithologic variability of the St. Laurent Formation in and near the study area 22

13 Isopach map of New Albany Shale 24 14 T sopach map of Springville Shale 25

15 Basal Fort Payne Formation and upper Springville Shale in the altered area 26

16 Siliceous limestone of the Fort Payne Formation cropping out north of Lingle Creek 27 17 Isopach map of Fort Payne Formation 28

18 Crosslaminated Ullin Limestone (Jonesboro Quarry), showing the typical "speckled" appearance of the limestone 29

19 Large-scale planar crossbedding in upper Ullin Limestone at the Columbia Quarry Company's Jonesboro Quarry 29 20 Stratigraphic column showing Mississippian units of the study area 31

21 Steeply dipping Cretaceous-Tertiary sand and gravel 32 22 Map showing structural features of the study area and distribution of Cretaceous-Tertiary strata 36

23 Megabreccia, composed of blocks of altered Springville Shale and St. Laurent Formation in a soft claylike matrix 38

24 Profile of fault zone along an east-trending ravine 39

25 Faults on the north-facing wall of Lone Star Cement Company's open-pit silica mine 40

26 Sketch of fault and kink fold exposed in the bank of a creek 41

27 Sketch of a fault in the southwest bank of Johnson Creek 41

28 Anticline in the Springville Shale 42

29 Tight chevron fold in shale and siltstone of the St. Laurent Formation in You-Be-Damned Hollow 42

30 Fault in the Springville Shale 43

31 Fissure (2 ft wide) in Clear Creek Formation 43

32 Fault zone in south bank of Cooper Creek 44

33 Fault at the portal of an abandoned ganister mine near Elco 45

34 Small fault displacing Cretaceous-Tertiary sand and gravel 45

35 Twin "chaser" grinding mills of an abandoned silica plant 50

36 A sample of mammillary manganese dioxide from the St. Laurent Formation near the Delta Fault 53 TABLES 1 Thicknesses and lithologies of formations in the Knox Group in the Humble no. 1 Pickel well 8

2 Significant boreholes in the study area 52 Digitized by the Internet Archive

in 2012 with funding from

University of Illinois Urbana-Champaign

http://archive.org/details/geologyofjonesbo101deve ABSTRACT

The Jonesboro 15-Minute Quadran- north-northwest-south-southeast, gle in southernmost Illinois lies at northeast-southwest, and east-west. the border of three major geologic The tectonic history has not been provinces: the Ozark Dome, the Illi- worked out completely; many faults nois Basin, and the Em- were active in the late Paleozoic and bayment. Outcropping bedrock some underwent post- dis- ranges from the Maquoketa Forma- placement. tion (Upper Ordovician) through the Paleozoic rocks are thoroughly Pope Group (upper Mississippian). leached and silicified in most of the These rocks are mainly limestone, southern half of the study area. along with lesser amounts of shale, Altered rocks are riddled by innu- siltstone, sandstone, and bedded merable intersecting joints and chert. Paleozoic rocks regionally dip faults, most of which are too small east-northeastfrom the Ozark Dome to portray at the 1:24,000 scale. We toward the . Weakly interpret alteration as a product of lithified Cretaceous and Eocene (?) hydrothermal activity. Hydrother- sand, gravel, and clay occur as small mal fluids, heated by deep-seated downfaulted and erosional outliers igneous intrusions, percolated on Paleozoic bedrock. Quaternary through joints and faults. loess and colluvium mantle the up- Microcrystalline silica, derived lands, while alluvial and lacustrine from leached and silicified Lower sediments underlie valley bottoms. Devonian rocks, is the principal eco- The area contains several systems nomic mineral product of the area. of faults that reflect multiple epi- Substantial resources of Mississip- sodes of deformation. Most faults pian limestone suitable for various are strike-slip and high-angle normal; uses are available in the north- prevalent trends area north-south to eastern part of the quadrangle. V d ^

5 *

>? "ftijflW if-

Faults apparently controlled selective silicification of rocks in the study area, as illustrated by this outcrop of highly silicified Clear Creek Formation (Lower Devonian) along a northeast-trending fault. (View is directed to the noartheast.) Bedding strikes northeast and dips northwest. Originally a cherty limestone, the Clear Creek was totally converted to chert and trip- oli in this area. Location is SW NW SW, Sec. 14, T14S, R2W, Mill Creek 7.5-Minute Quadrangle. SUMMARY

The Jonesboro 15-Minute Quadran- stone, and limestone. It represents a distant eastern source area. The gle is situated in southernmost Illi- two upward-shoaling cycles, with Fort Payne Formation, fine grained nois along the Mississippi River. It siliciclastics derived from both a dis- siliceous limestone and bedded encompasses parts of three major tant eastern source and a nearby chert 10 to 140 feet thick, disconform- geologic provinces: the Ozark western source on the Ozark Dome. ably overlies the Springville. The Dome, the Illinois Basin, and the Silurian strata include the Sexton overlying Ullin, Salem, St. Louis, Mississippi Embayment. The Ozark Creek Limestone (30 to 40 feet of and Ste. Genevieve are a Dome section on the west features cherty limestone) and the Bain- laterally intergrading succession of rugged uplands underlain by Ordo- bridge Formation (120 to 180 feet of shallow-water limestones about vician through Devonian bedrock. limestone, marlstone, and red to 1,000 to 1,250 feet thick. The young- The Illinois Basin section, in the green calcareous shale). These rocks est Paleozoic rocks in the quadran- northeast corner of the quadrangle, apparently were deposited in tec- gle are intertonguing limestones, is rolling upland having karst topog- tonically stable, quiet-water marine shales, and of the Pope raphy commonly developed in Mis- settings. The Silurian-Devonian Group (upper Valmeyeran to lower sissippian limestone bedrock. The boundary lies in the lower part of Chesterian Series).

Mississippi Embayment section in the Bailey Limestone, which overlies Cretaceous and Eocene (?) sedi- the southeast corner is represented the Bainbridge. ments occur as scattered hilltop out- by nearly level Quaternary flood- Lower Devonian rocks include liers and along a discontinuous plain deposits in the Cache Valley. most of the Bailey Limestone, the north-trending belt in the eastern The broad floodplain of the Missis- , and the Clear part of the quadrangle. The belt is in- sippi River crosses the east flank of Creek Formation. These three forma- terpreted as a fault-controlled pale- the Ozark Dome along the west tions consist of light-colored, mi- ovalley. Deposits are tentatively edge of the study area. critic to fine grained, cherty, assigned to the Upper Cretaceous and Ordovician rocks siliceous limestone and bedded Tuscaloosa Formation (light-colored of the Jonesboro Quadrangle are chert. They total 750 to 900 feet chert gravel), the Upper Cretaceous known principally from borehole thick. Conditions of sedimentation McNairy Formation (brightly col- data. The oldest unit penetrated by are not well established, but the ored sand, silt and clay, with lenses drilling is the Upper Cambrian Mt. Bailey and Grassy Knob seem to re- of white quartz arenite and conglom- Simon (Lamotte) Sandstone. This is cord gradual deepening, and the erate), and the Eocene Wilcox Forma- overlain by more than 6,500 feet of Clear Creek gradual shoaling, of a tion (?) (sand and gravel with gray cherty, sandy dolomite of the Knox sea where much biogenic silica was to black, rounded chert pebbles). All Group (Upper Cambrian and Lower produced. The east flank of the of these appear to be fluvial and Ordovician). Middle Ordovician Ozark Dome rose and periodically overbank sediments, except rocks comprise the following: the shed siliciclastics eastward during McNairy quartz arenite, which prob- Everton Formation at the base, 240 Middle and Late Devonian time. ably is a marine shoreface deposit. feet of sandy dolomite; the St. Peter Middle and Upper Devonian rocks Structure of the quadrangle is Sandstone, about 45 feet of quartz progressively thin and are truncated complex. The regional dip is ENE, arenite; the Dutchtown Formation, westward onto the flank of the into the Illinois Basin. The north- 200 to 360 feet of petroliferous lime- dome. These strata include the Mid- trending Harrison Creek Anticline stone and dolomite; the Joachim dle Devonian Grand Tower Lime- probably overlies a basement fault. Dolomite, about 230 feet thick; the stone (skeletal limestone and quartz The Atwood and Delta Faults and "Pecatonica" and Plattin Forma- sandstone 10 to 125 feet thick) and several smaller faults that strike tions, 525 to 700 feet of mostly dark, St. Laurent Formation (cherty car- NNW are high-angle normal faults. micritic limestone; the Decorah For- bonates, shale, and siltstone 60 to Innumerable smaller faults occur in mation, 40 to 60 feet of argillaceous 200 feet thick) and the Upper Devo- the southern Jonesboro 7.5-Minute limestone and shale; and the Kimms- nian New Albany Shale (black shale, Quadrangle and through most of the wick Limestone, 115 to 160 feet of where present, up to 80 feet thick). Mill Creek Quadrangle. The most white, coarsely crinoidal, high- During Mississippian time the common trends are north-south, calcium limestone. The Maquoketa Ozark Dome was still a positive north-northwest-south-southeast, Formation of Cincinnatian (Late area, but it did not shed sediment to east-west, and northeast-southwest. Ordovician) age is the oldest unit ex- the study area. The Springville Shale Many of these faults show features posed in the Jonesboro Quadrangle. (lower Valmeyeran) is an upward- indicative of strike-slip, such as hori- The Maquoketa comprises 140 to coarsening prodeltaic wedge (distal zontal slickensides, "flower struc- 200 feet of shale, siltstone, sand- Borden delta) probably derived from tures," and pull-apart grabens. The amount and direction of displace- by heat from deep-seated igneous and for road gravel. Other forms of ment and the tectonic history are intrusions (Berg and Masters 1994). silica, called ganister and calico rock, poorly understood. Some faults dis- The altered rocks originally had were mined or quarried in the past. place Cretaceous and Tertiary strata, high silica content (detrital, bio- Limestone was quarried in the past but no examples of deformed genic, and diagenetic). This silica from several Mississippian forma- Quaternary deposits are known. was remobilized and recrystallized. tions and is being quarried today Paleozoic bedrock is intensively Silica is the principal economic just east of the quadrangle. The altered, leached, and silicified in a mineral deposit of the area. Tripoli is Ullin and Ste. Genevieve Lime- large part of the study area. Lime- a white, pure form of microcrys- stones, in particular, are suitable for stones have been dissolved away or talline silica, used widely as fillers, a variety of purposes. The Kimms- replaced by siliceous rocks known abrasives, and buffing and polishing wick Limestone (Ordovician) is a locally as chert, tripoli, novaculite, agents. Commercial tripoli is derived potential source of high-purity lime- ganister, and calico rock. The silici- from alteration of Lower Devonian stone. Petroleum prospects of the fied area is riddled with small-scale siliceous formations—chiefly the area are speculative; about 17 dry faults, which served as pathways for Clear Creek Formation and to a test holes, mostly shallow, have been silicifying fluids. The rocks were lesser extent the Grassy Knob and drilled in the quadrangle. Metallifer- probably altered by low-tempera- Bailey. Less pure forms of silica are ous cuttings from a deep borehole in ture hydrothermal activity, driven quarried for cement manufacture the quadrangle indicate the poten- tial for deep, metallic ore deposits.

ILLINOIS

BASIN

NEELY'S LANDING Whitfield and Middendorf 1988 WOLF LAKE Devera 1993 :OBDEN MAKANDA COBDEN OZARK Devera and Nelson 1 995 MAKANDA Jacobson and Weibel 1993 DOME CAPE GIRARDEAU NE CAPE WARE JONESBORO ANNA Middendorf et al. 1988 GIRARDEAU \ WARE (MO) NE Middendorf 1989 ANNA / J. Weller and Ekblaw 1940 CAPE McCLURE MILL CONGOLA CAPE GIRARDEAU, McCLURE (MO) GIRARDEAU' CREEK Satterfield 1973 DONGOLA Nelson, in preparation SCOTT CITY, THEBES (MO) / Johnson 1 985 / Harrison, in preparation .SCOTT / \ THEBES (IL), TAMMS, PULASKI CITY THEBES TAMMS PULASKI Pryor and Ross 1 962 \ / TAMMS ayment Devera, in preparation BMeMB /KY MISSISSIPPI ( / ^ 10 20 mi _L_ ^ l r- 1^ "T~ 37^N \ ) \ 10 20 30 km

Figure 1 Location map, showing study area (shaded), adjacent quadrangles, and major structural features. Authors of the quadrangle maps are listed to the right. INTRODUCTION

Purpose Ware Quadrangles were mapped The Ozark Dome Province, which This report accompanies geologic previously (Satterfield 1973, Midden- makes up the largest part of the maps of the Jonesboro and Ware dorf 1989). study area, has been recurrently up- (Nelson and Devera, 1994) and Mill The study area contains parts of lifted from to Recent. Creek and McClure (Devera et al. three physiographic provinces Surface bedrock is of Ordovician 1994) 7.5-Minute Quadrangles. These (Leighton et al. 1948). The north- through Devonian age. Strata dip quadrangles were mapped under eastern part (the area east of Illinois gently in most places and are dis- the Cooperative Geologic Mapping Rt. 127) is in the Shawnee Hills Sec- placed by faults having a variety of (COGEOMAP) program, a joint ef- tion of the Interior Low Plateaus trends. fort of the U.S. Geological Survey Province. This area of gently to mod- The Illinois Basin is an intracra- (USGS) and the Illinois State Geo- erately rolling topography is under- tonic basin that attained its present logical Survey (ISGS). lain by Mississippian limestone. form near the end of the Paleozoic The Jonesboro 15-Minute Quad- Karst topography is locally present. Era. The basin contains Cambrian rangle lies in a key area geologically. The land is used mainly as pasture through sedimentary Parts of three major geologic prov- for cattle and some row-crop farm- rocks and is structurally centered inces—the Ozark Dome, the Illinois ing; steeper slopes are left as wood- about 80 miles (130 km) northeast of Basin, and the Mississippi Embay- lots. Most of the area's population the Jonesboro Quadrangle. In the ment—fall within the study area lives in the Shawnee Hills Section. study area, the edge of the basin (fig. 1). Ordovician through Missis- Uplands of the western and most of may be regarded as the limit of Mis- sippian bedrock crops out in this the southern part of the study area sissippian strata. These rocks dip quadrangle, as do Cretaceous and are in the Salem Plateaus Section eastward and northeastward at 2° to Tertiary strata. The quadrangle lies of the Ozark Plateaus Province 12°; no large faults were mapped. just north of the New Madrid Seismic (Leighton et al. 1948). Steep rugged The Cache Valley at the southeast Zone, the most active earthquake hills and deep V-shaped ravines corner of the study area approxi- area in the central . Pre- characterize this section. A mature mately follows the north erosional vious geologists, such as J. Weller dendritic or trellis drainage pattern edge of the Mississippi Embayment, and Ekblaw (1940), observed com- has developed. The area is thinly a northward extension of the Gulf plex structure in this area but did populated and densely wooded; Coastal Plain. Beyond the study not map it in any detail or interpret farming (mostly for raising cattle) is area, Cretaceous and Tertiary sedi- it. Faults that displace Tertiary and largely confined to bottomlands mentary rocks crop out south and possibly Quaternary strata are re- along the larger valleys. The south- east of the Cache Valley. In the Jones- ported in adjacent areas (McCracken east corner of the study area is boro Quadrangle, Cretaceous and 1971, Johnson 1985, Harrison and within the Coastal Plains Province Tertiary strata occur as ridge-top out- Schultz 1992). Immediately north of (Leighton et al. 1948). The broad liers and in a south-trending pale- the study area, the Ste. Genevieve Cache Valley, the floodplain of the ovalley that follows the boundary Fault Zone follows a major Precam- ancestral Ohio River, follows the between the Ozark Dome and Illi- brian crustal boundary (Heigold and north erosional edge of the Coastal nois Basin. Kolata 1993). Economically, the Plain. The Cache floodplain, along Jonesboro Quadrangle contains valu- with the Mississippi River flood- Previous Studies able limestone and silica resources. plain in the western part of the quad- The only published geologic map The origin and geologic controls of rangle, is the scene of extensive row- for the Jonesboro 15-Minute Quad- silica deposits in southern Illinois crop farming and livestock grazing. rangle is the "preliminary" map of a have long been puzzle. J. Weller and Ekblaw (1940), compiled Geologic Setting on a planimetric base of 1:62,500 Location and Physiography The study area contains parts of scale and on the basis of field work The Jonesboro 15-Minute Quadran- three major structural provinces: the conducted mainly during the 1920s. gle contains the Jonesboro, Ware, Ozark Dome, the Illinois Basin, and A descriptive report accompanies the McClure, and Mill Creek 7.5-Minute the Mississippi Embayment (fig. 1). map. Weller and Ekblaw thoroughly Quadrangles in Union and Alexan- These structural provinces coincide, described Paleozoic rock units, but der Counties, Illinois, and Cape respectively, with the Ozark Pla- they purposely omitted small faults Girardeau County, (fig. 1). teaus, Interior Low Plateaus, and and treated Cretaceous and Tertiary Only the portion in Illinois was Coastal Plains physiographic prov- deposits in a cursory fashion. mapped for this report. The Mis- inces previously described. An unpublished manuscript and souri portions of the McClure and a hand-colored geologic map of the .

Jonesboro 15-Minute Quadrangle were produced by Savage (1920b). The Missouri portion of the McClure Quadrangle was mapped by Satter- field (1973); the Missouri portion of the Ware Quadrangle was mapped by Middendorf (1989). Other geo- logic maps for the general area are indicated in figure. 1. Methodology We mapped the Jonesboro, Mill Creek, and Illinois portions of the Ware and McClure Quadrangles be- tween October 1991 and May 1992, using USGS 7.5-minute topographic maps as base maps. A small area of the Mill Creek Quadrangle was mapped in 1989-1990 by Berg and Masters (1994) and spot-checked during the present study. Nelson used well records on public file at the ISGS to map the subsurface geol- ogy of the study area. These well records include drillers' logs, geolo- gists' sample studies, and geophysi- cal logs. Specifically for this study, Nelson examined cuttings from sev- eral wells

m ft

-100

50- -200

300 100-

-400

150-i-500

Figure 2 Stratigraphic column showing Middle and Upper Ordovician units (except Leemon Formation) in the study area.

The Jonesboro Quadrangle contains made on the basis of geophysical log St. Peter Sandstone Cambrian through Mississippian interpretation and sample and insol- The St. Peter Sandstone is one of the sedimentary rocks, weakly lithified uble-residue analysis by M.L. Sar- most widespread and easily recog- Cretaceous and Tertiary sediments, gent (written communication, 1992). nized formations of the central and unlithified Quaternary sedi- Formation names are the same as United States. It is predominantly ments. The oldest rocks exposed in those used for strata outcropping to white to light gray, fine to coarse the study area are Late Ordovician the west of the study area, on the grained, well rounded and frosted (fig. 2). Cambrian through Middle Ozark Dome in Missouri. For com- quartz sand that is generally weakly Ordovician rocks are known from parison, thicknesses of Cambrian cemented. Beds of sandy dolomite logs of deep boreholes and from ex- units in Missouri (from Martin et al. occur locally. The St. Peter is posures west of the study area in 1961) and of Ordovician units (from assigned to the lower Mohawkian Missouri. Thompson 1991) are also listed in Series (Middle Ordovician) and over- table 1. The table shows that the en- lies the Everton Formation discon- Mt. (Lamotte) Simon tire Knox Group and every constitu- formably in most places (Kolata and Sandstone ent formation thickens eastward Noger 1991, Thompson 1991). The oldest rock unit known in the from Missouri to the Pickel well. The St. Peter is 48 feet thick in the Jonesboro Quadrangle is the Cam- This eastward thickening conforms Humble no. 1 Pickel well and 40 feet brian-age Mt. Simon (Lamotte) Sand- with regional trends mapped by Sar- thick in the Ohio Company no. 1 stone, which was penetrated by the gent (1991, p. 82). Cross well, both of which are on the Humble Oil Company no. 1 Pickel Harrison Creek Anticline. At the borehole, in the NW SE NW, Sec. 21, Everton Formation nearest outcrops in Missouri, 8 to 10 T13S, R2W, in the Mill Creek Quad- The Everton Formation is a unit of miles west of the study area, the St. rangle. In this well, 122 feet of Mt. Si- Whiterockian age. It is composed of Peter averages about 100 feet thick mon was drilled, and the base of the interbedded sandy dolomite and (Thompson 1991, Nelson 1995). Two formation was not reached. The dolomitic sandstone, and it uncon- deep wells southeast of the study sandstone is described on the sample formably overlies the Knox Group area, in Pulaski County, Illinois, pene- log as white to pink, fine to medium (Kolata and Noger 1991, Thompson trated 130 to 150 feet of St. Peter. grained quartz arenite with silica 1991). In the Humble no. 1 Pickel Thinning of the St. Peter in the cement. This lithology is typical of well, the Everton Formation com- Pickel and Cross wells indicates that the upper part of the Lamotte Sand- prises about 240 feet of sandy dolo- the Harrison Creek Anticline rose stone on the Ozark Dome in Mis- mite that is light to medium brown during early Mohawkian sedimenta- souri (Hayes and Knight 1961) and and micritic to coarsely crystalline. tion. Alternatively, the thinning the upper Mt. Simon Sandstone in The Ohio Oil Company no. 1 Cross might simply reflect deposition of the subsurface throughout Illinois well, located in the NW NW NE, the St. Peter on an uneven erosional (Buschbach 1975). The Lamotte and Sec. 21, T13S, R2W, in the Jonesboro surface. Mt. Simon are correlative units of the 7.5-Minute Quadrangle, reached St. Croixan Series (Late Cambrian). total depth about 15 feet into the Dutchtown Formation Everton Formation. The Everton is The Dutchtown is about 200 feet Knox Group 56 and 106 feet thick, according to thick in the Cross well and 361 feet The name Knox Group is applied to the sample logs of two deep wells 8 thick in the Pickel well. In both the thick succession of Upper Cam- to 10 miles southeast of the study wells, the Dutchtown is composed brian and Canadian (Lower Ordovi- area in Pulaski County. The Everton of dark-colored, micritic to finely cian) carbonate rocks overlying the thickens southeastward, from about crystalline limestone, in addition to Mt. Simon Sandstone in the south- 70 feet in Perry County, Missouri, to dolomite that is argillaceous and ern part of the Illinois Basin. Equiva- more than 400 feet in the subsurface partly sandy. Identification of the lent formations that outcrop on the in southeastern Illinois (M.L. Sar- Dutchtown is more definitive in the Ozark Dome in Missouri are difficult gent, personal communication, Pickel well, for which geophysical to trace into the subsurface because 1994). Variations in thickness of the logs are available in addition to a of lithologic similarity and down- Everton may reflect (1) differential sample log. dip facies changes. subsidence during deposition, In its type area of southeastern A total of 6,624 feet of Knox strata (2) deposition of the Everton on an Missouri, the Dutchtown is com- was penetrated in the Humble no. 1 irregular erosional surface, and posed of dark brownish gray, Pickel well. Subdivision of the Knox (3) erosion of the Everton before micritic to very finely crystalline Group in the Pickel well (table 1) is deposition of the St. Peter Sandstone. limestone and dolomite, containing Table 1 Thicknesses and lithologies of formations in the Knox Group in the Humble no. 1 Pickel well (from M.L. Sargent, written communication, 1992). Thicknesses of the units at the nearest outcrops in southeast Missouri are given for comparison.

Unit Thickness Outcrop

(oldest first) (ft) thickness (ft) Lithology

Cambrian System Bonneterre Fm 600 375-400 Dolomite, sandy, glauconitic, increasingly sandy near base Davis Fm 136 170-225 Calcareous dolomite to dolomitic limestone, light to medium brown, oolitic Derby/ Doerun Fms 544 0-200 Dolomite, slightly sandy, very cherty 978 75-300 Dolomite, sandy, cherty, with quartz-filled vugs (drusy quartz) Eminence Dolomite 758 200-350 Dolomite, slightly sandy, very cherty; some oolitic chert

Ordovician System, Canadian Series Gasconade Fm 584 400-500 Dolomite, light brownish gray, cherty; basal Gunter Sandstone Member about 30 feet thick Roubidoux Fm 640 200-250 Dolomite, cherty, very sandy; sandstone, fine to medium, rounded, dolomitic Jefferson City Fm 606 250 Dolomite, slightly sandy, very cherty with oolitic chert Cotter Dolomite 871 350-500 Dolomite, sandy, with thin interbeds of sandstone Powell Dolomite 389 100-150 Dolomite, slightly sandy, with dolomoldic chert Smithville Dolomite 188 150 Dolomite, argillaceous to silty, with vitreous chert Unnamed unit 330 ? Dolomite, mostly fine grained, argillaceous

Total Knox Group 6,624 2,270-3,275

finely disseminated organic matter (1963). The Pecatonica was recently Although some geologists divide the and bitumen-filled vugs (Martin et mapped in several quadrangles in Plattin into formations, quadrangle al. 1961, Thompson 1991). The southeastern Missouri. Comparison mappers in southeastern Missouri

Dutchtown thins northward; it is of maps and lithologic descriptions treated it as a single unit. The Plattin about 185 feet thick in southern indicate, however, that the Peca- is difficult to subdivide in the sub- Cape Girardeau County and pinches tonica was not consistently differen- surface, although the Brickeys and out in Perry County, Missouri (Nel- tiated from the overlying Plattin Establishment Members can be iden- son 1995). Limestone in these quadrangles tified in some wells. (Nelson 1995). Thompson (1991, The Plattin is composed largely Joachim Dolomite p. 109) regarded identification of the of brownish gray mottled and bur- The Joachim Dolomite is composed Pecatonica in Missouri to be "tenta- rowed lime mudstone, similar to of light to medium gray and brown, tive and questionable" and placed that of the "Pecatonica Formation." very fine to fine grained sandy dolo- "Pecatonica Formation" in quotation It is argillaceous and contains chert, mite containing little chert. Lesser marks. Thompson stated that the but it lacks sand. Thin intervals of amounts of limestone occur in the "Pecatonica" is nearly identical in skeletal grainstone occur within the upper part of the formation. Thin lithology to the Plattin. Plattin. The Brickeys Member, at the interbeds of gray dolomitic shale are The "Pecatonica" was tentatively base, contains oolitic grainstone and present throughout the unit, and identified in the Humble no. 1 Pickel is overlain by the thin but very wide- sandstone interbeds are common in well as a 93-foot-thick interval of spread Establishment Shale Member.

the lower part (Thompson 1991). dark, micritic limestone; it overlies The oolitic limestone is distinctive in The Joachim in both the Ohio Com- sandy dolomite of the Joachim and well cuttings, and the shale can be pany no. 1 Cross and Humble no. 1 underlies a thin oolitic limestone identified on many geophysical Pickel wells is about 230 feet thick thought to be the basal Brickeys logs, particularly gamma-ray logs. and is lithologically similar to Member of the Three wells in the study area Joachim in outcrops in Missouri. The (M.L. Sargent, written communica- penetrated the entire Plattin. In the Joachim was reported to be 190 to tion, 1992). Other wells in and close Humble no. 1 Pickel well, the 275 feet thick in the Missouri part of to the study area lack logs that are Plattin (to the base of the Brickeys the Cape Girardeau Quadrangle sufficiently detailed to differentiate Member) is 432 feet thick, and the (Satterfield 1973). the "Pecatonica" from the Plattin. combined Plattin-'Tecatonica" thickness is 525 feet (M.L. Sargent, Pecatonica Formation" Plattin Limestone written communication, 1992). The Pecatonica Formation was Thompson (1991, p. 127) stated that Undivided Plattin-'Tecatonica" is named by Hershey (1894) for its the Plattin Limestone in southeast- about 665 feet thick in the Ohio Oil type locality in northern Illinois. It ern Missouri can be classified as Company no. 1 Cross well and 693 was extended into southeastern Mis- either a formation or a group, "ac- feet thick in the Mims no. 1 Potash- souri by Templeton and Willman cording to the needs of the worker." nick well (NW NW SE, Sec. 26, T13S,

8 R3W, McClure Quadrangle). Region- able. A lower argillaceous limestone mon, as are vugs, some of which are ally, the Plattin-'Tecatonica" thick- (Castlewood) is overlain by a - lined with asphaltic residue. Black,

ens southeastward; it is 500 to 525 iferous shale (Glencoe) and an upper semivitreous chert nodules are com- feet thick in the Cape Girardeau argillaceous or silty limestone mon 20 to 40 feet below the top of Quadrangle (Satterfield 1973), 345 to (Kings Lake). Only the Glencoe the formation. include the 420 feet thick in wells north of the Shale can be identified on most of distinctive "sunflower " Recep- study area in Jackson County, and the geophysical logs. In and near the taculites, in addition to gastropods, 715 to 780 feet thick in wells to the Jonesboro Quadrangle, the Decorah bryozoans, ostracods, illaenid trilo- southeast in Pulaski County. is about 40 to 60 feet thick, and the bites, and the Hebertella The contact of the Plattin with the Glencoe is 15 to 20 feet thick. The and Platystrophia. Light gray vuggy overlying Decorah Formation is un- Decorah Formation is disconform- and crystalline dolomite is reported conformable (Templeton and Will- ably overlain by the Kimmswick in the Kimms-wick in sample logs man 1963). Limestone (Thompson 1991). from wells north of the Jonesboro 15- Minute Quadrangle. The Kimms- Decorah Formation Kimmswick Limestone wick ranges from about 115 to 160 Geologists variously classify the The Kimmswick Limestone was feet thick in wells in and adjacent to Decorah as a formation (Decorah named for exposures at Kimmswick, the study area. The Kimmswick is Shale), a subgroup (Templeton and Missouri, about 20 miles south of St. assigned to the upper part of the Willman 1963), or a group (Thomp- Louis (Ulrich 1904). Although Tem- Mohawkian Series (Thompson son 1991). In and near the study pleton and Willman (1963) reclassi- 1991). area, the Decorah is only 40 to 60 fied the Kimmswick as a subgroup feet thick and cannot be subdivided of the in Illinois, Cape Limestone except in unusually good exposures geologists in Missouri continue to The Cape Limestone was named for (such as quarry faces and cores). rank the Kimmswick as a formation. Cape Girardeau, Missouri, by Tem- Most mappers in southeastern Mis- Thompson (1991) points out that the pleton and Willman (1963); the type souri either combined the Decorah Kimmswick in Missouri is substan- section is on Main Street north of and Plattin into one unit or did not tially different in lithology from the Broadway. This unit was previously distinguish the Decorah at all. The type Galena of northwestern Illinois. called the

Decorah is treated as a formation in The Kimmswick is a high-calcium (Savage 1920b, J. Weller and Ekblaw this report; the name Decorah For- limestone (coarse crinoidal grain- 1940). The Cape was classified as a mation is used instead of Decorah stone), whereas the Galena is a fine formation in the Shale because limestone is a major to medium grained, argillaceous, by Templeton and Willman (1963) constituent. and cherty dolomite. The Kimms- and as a separate formation by Cores from the northern Thebes wick in the Jonesboro area has the Thompson (1991). The type section Quadrangle, a few miles south of same lithology as occurs at the type consists of 8 feet of medium to dark the study area, provide the best in- locality and cannot be divided read- gray, very fossiliferous, crinoidal formation on the Decorah. In these ily into smaller units. Therefore, we limestone that is distinctly darker, cores, the Decorah comprises 8 to 17 use the name Kimmswick Limestone finer grained, and more argilla- feet of fossiliferous, shaley limestone rather than Kimmswick Subgroup of ceous than the upper part of the that has thin shale interbeds. The the Galena Group. Kimmswick (Thompson 1991). The limestone is light to medium brown- The Kimmswick crops out in the Cape is middle Cincinnatian (Mays- ish gray lime mudstone and skeletal Missouri part of the McClure and villian to early Richmondian; Sweet wackestone; the shale is light green- Cape Girardeau Quadrangles (Satter- etal. 1975) and is separated by dis- ish gray to brownish gray, slightly field 1973) and in the Thebes Quad- con-formities from the Kimmswick fissile, and calcareous. Bedding is rangle in Illinois immediately south below and the Maquoketa above wavy, contorted, and nodular. Tre- of the study area (J. Weller and (Templeton and Willman 1963, postome, bifoliate, and fistuliporid Ekblaw 1940, Pryor and Ross 1962). Thompson 1991). bryozoans; brachiopods, including Excellent exposures of the Kimms- We examined the Cape interval in Rafinesquina and Hebertella; gastro- wick are at the Grays Point Quarry several cores taken from the north- pods; rugose ; and in the Thebes Quadrangle. Several ern Thebes Quadrangle. Medium to fragments are common. The contact wells in the McClure and Mill Creek dark gray, fine grained limestone as with the Plattin Limestone is grada- Quadrangles penetrate the Kimms- thick as 22 feet occurs at the top of tional in these cores, whereas the wick. Also, cores of the Kimmswick the Kimmswick in some cores. This Decorah-Kimmswick contact is from the northern Thebes Quadran- rock is largely skeletal packstone, sharp and probably disconformable. gle were examined. In these out- but it contains layers of wackestone In wells lacking cores, the Deco- crops and wells, the Kimmswick is and lime mudstone. The contact rah can be distinguished from the white to light gray, mostly coarse with typical Kimmswick crinoidal Plattin below and Kimmswick Lime- grained crinoidal grainstone, which grainstone is either gradational or stone above by its greater clay con- contains practically no terrigenous sharp, but it is not noticeably discon- tent. The threefold division cited by clastic material. Thin intervals of formable. Whether the dark lime- Thompson (1991) can be recognized darker, finer grained wackestone stone in these cores is the Cape or a in wells for which good sample stud- and packstone occasionally occur in dark facies of the Kimmswick is not ies and geophysical logs are avail- the upper part. Stylolites are com- certain. A dark, fine grained limestone Limestone. The name Maquoketa Thebes Sandstone Member The that may be Cape was logged in Formation is used instead of Thebes Sandstone was named by several other boreholes in the area. Maquoketa Shale because sandstone Worthen (1866) for Thebes, Illinois. In the Humble no. 1 Pickel well, the and limestone are important con- The Thebes is restricted to a small Cape (?) is about 18 feet of brown, stituents. area of southeastern Missouri and very fine grained fossiliferous lime- In wells in the study area, the southwestern Illinois. stone. In the Mims no. 1 Potashnick Maquoketa ranges from 140 to 200 The Thebes crops out at the crest well, the Cape (?) is 23 feet of light feet thick. Similar thicknesses are re- of the Harrison Creek Anticline in brownish gray, very fine grained ported by Pryor and Ross (1962) for the SW NE SW, Sec. 16, T13S, R2W, shaley limestone. Two wells in Pu- the Thebes Quadrangle and by Sat- in the Jonesboro 7.5-Minute Quad- laski County encountered limestone terfield (1973) for the Missouri por- rangle, and in the bluff at Gale, NE that may also be the Cape; it is 5 feet tion of the McClure and Cape Girar- SW, Sec. 33, T14S, R3W, in the thick in one well and 12 feet thick in deau Quadrangles. The Maquoketa McClure Quadrangle. It is com- the other. thickens to 170 to 210 feet in wells posed of siltstone and very fine The mappability of the Cape southeast of the Jonesboro Quadran- sandstone in this area. These rocks Limestone is not resolved. The Cape gle. A regional isopach map of the are light to medium gray, greenish should perhaps be classified as a Maquoketa shows that the unit gray, and brownish gray, and lami- member of the Kimmswick instead thickens eastward across the Illinois nated to thinly bedded. They are of as a separate formation (fig. 2). Basin and that a locally thick area composed largely of subangular (more than 300 ft) occurs in western quartz sand having a clay matrix Maquoketa Formation (Whitaker 1988). and calcite cement. Interlaminations The oldest bedrock unit that crops The Maquoketa was assigned to of silty shale are present. The only out in the Jonesboro 15-Minute the Richmondian Stage of the Cincin- fossils noted are horizontal burrows Quadrangle is the Maquoketa For- natian Series by Sweet et al. (1975) and trails. Well records indicate the mation. The Maquoketa Shale was on the basis of faunas. Thebes is 25 to 60 feet thick in the named by White (1870) for outcrops Jonesboro Quadrangle. near Maquoketa, , where the Cape La Croix Shale Member The Outcrops and cores from the unit consists of shale with interbeds Cape La Croix Shale was named (as northern Thebes Quadrangle show of limestone. Templeton and Will- a formation) by Thompson (1991) the Thebes to be as thick as 110 feet man (1963) elevated the Maquoketa for Cape La Croix Creek in the north- and composed of siltstone to very to a group in Illinois. In southeast- ern part of the Cape Girardeau Quad- fine grained, argillaceous sandstone. ern Missouri and southern Illinois, rangle. The type section consists of Bedding or lamination is weakly de- some geologists classified the 17 feet of bluish gray, calcareous, veloped and commonly obscured by Maquoketa as a group (Middendorf platy shale containing occasional bioturbation. Numerous burrowed 1989, Middendorf et al. 1988, nodules and thin beds of limestone. intervals are present, particularly in Thompson 1991), whereas others This unit was described previously the lower part of the member. A called it a formation (Pryor and Ross as an unnamed member or forma- distinctive unit at the base of the 1962, Satterfield 1973, Johnson 1985). tion of the Maquoketa. Thebes is composed of dark gray Among those who mapped the The Cape La Croix does not crop mudstone containing small inarticu- Maquoketa, most portrayed it either out in the Jonesboro Quadrangle, late brachiopods and other fossils, as a single unit or combined two or but well records indicate that it is along with small, dark gray to black more members (formations) as a present. Drill cores from the Thebes spherical pellets (phosphate?). Mud- matter of convenience. Quadrangle show the Cape La Croix stone variegated in red, green, and Subdivisions of the Maquoketa to be 24 to 36 feet thick and com- ochre occurs at the top of the Thebes are thin (averaging 35 to 50 ft) in the posed of dark gray to olive gray clay in some cores. study area, and their contacts inter- shale or silty shale that commonly The Thebes thins eastward and grade vertically and laterally. grades to siltstone near the top. The northward in the subsurface, grad- Although distinct lithologically, shale is slightly fissile, calcareous, ing laterally to siltstone and silty these subdivisions cannot be and contains gastropods, nautiloid shale and intertonguing with the mapped reliably and portrayed at cephalopods, ostracods, , Cape La Croix Shale. It is restricted scales of 1:24,000 and smaller. More- and brachiopods. Thin interbeds to southern Jackson and part of over, these subdivisions can be rec- and lenses of fossiliferous lime mud- Pulaski Counties as well as all of ognized in only a small area of stone occur in the shale. The basal Union and Alexander Counties. The southeastern Missouri and south- portion of the Cape La Croix is a Cape La Croix and Orchard Creek western- most Illinois. The subdivi- soft, gummy claystone that yields Shales cannot be differentiated in sions thus fail the test of mappa- poor core recovery. The Cape La areas where the Thebes is absent. bility for valid formations (North Croix grades upward to the Thebes The upper contact of the Thebes is American Stratigraphic Code 1983) Sandstone Member. sharp but apparently conformable. and are properly classified as mem- Well records in the Jonesboro bers. Accordingly, we classify the Quadrangle indicate the Cape La Orchard Creek Shale Member Maquoketa as a formation divided Croix to be dark shale 35 to 60 feet The Orchard Creek Shale was into four members: Cape La Croix thick. Southeast of the study area, named by Savage (1909) for a creek Shale (oldest), Thebes Sandstone, well records show the member is 90 about 2 miles (3 km) south of Orchard Creek Shale, and Girardeau to 150 feet thick, apparently thicken- Thebes, Illinois, which is south of ing at the expense of the Thebes. the report area. The Orchard Creek

10 crops out in a small area near Gale Early workers in the region, in- being discontinuous and less than 25 in the McClure Quadrangle and cluding Savage (1920b), J. Weller feet thick. Pending further study, south of Harrison Creek at the crest and Ekblaw (1940), and Pryor and that rank is left unchanged. of the Harrison Creek Anticline. It is Ross (1962), assigned the Girardeau The Leemon does not crop out in not well exposed. The upper part of to the Silurian System. Study of the the Jonesboro 15-Minute Quadran- the Orchard Creek and the grada- conodont fauna by Satterfield (1971) gle, but it does occur in the Thebes tional contact with the overlying indicated that the Girardeau is Rich- Quadrangle (Savage 1920b, Pryor Girardeau Limestone can be seen mondian (late Ordovician). Brower and Ross 1962) and in nearby areas along Harrison Creek in the SW SW (1973) suggested, on the basis of a of Missouri. In those places, the NE, Sec. 16, T13S, R2W. More details study of the fauna, that the Leemon is an oolitic and skeletal of the Orchard Creek are known Girardeau was Richmondian or grainstone, commonly crossbedded from well records, particularly from slightly younger (Gamachian Stage). and containing thin interbeds of cores from the Thebes Quadrangle. He also suggested that it may be ear- shale. Phosphatic pebbles and clasts Lithologically, the Orchard Creek liest Silurian age. eroded from the underlying Girar- is similar to the Cape La Croix Mem- The Girardeau Member is ex- deau Limestone are common near ber. The shale is greenish gray to posed along the Harrison Creek the base (Thompson and Satterfield olive gray (less commonly dark gray Anticline in the southwestern part of 1975, Thompson 1991). to black), soft and fissile, and partly the Jonesboro 7.5-Minute Quadran- The Leemon probably is present silty, becoming siltier upward. The gle, in a small area north of Valley in several wells in and near the re- upper part is strongly calcareous, Mission in the Mill Creek Quadran- port area. It is logged as oolitic lime- the lower part less so. Nodules and gle, and in the bluffs northeast of stone and is less than 20 feet thick. thin interbeds of dense, argillaceous Gale in the McClure Quadrangle. An isopach map by Rogers (1972) lime mudstone increase in number The best exposure is a bluff south of shows the "Edgewood" (Leemon) and thickness upward, as the Harrison Creek near the center of largely absent east of the outcrop Orchard Creek grades into the over- Sec. 16, T13S, R2W. belt in far southern Illinois, but it lying Girardeau Limestone Member. In the study area, as at the type thickens northeast of the study area Satterfield (1971) found that the locality, the Girardeau is composed to more than 66 feet. Girardeau thickens westward at the of medium to dark gray and olive The Leemon ("Edgewood") origi- expense of the Orchard Creek and gray lime mudstone in thin wavy nally was assigned to the Silurian suggested that the two members are and lenticular beds. Dark gray chert System, but a study of the conodont facies equivalents. nodules are common in the upper fauna by Thompson and Satterfield Fossils from the Orchard Creek part. Interbeds of greenish gray cal- (1975) established late Richmondian include rare Flexicalymene sp., Cerau- careous shale occur throughout the (latest Ordovician) age. Later, rus sp., and disarticulated large vag- unit and become thicker and more Amsden and Barrick (1986) placed desid trilobites. More common are numerous toward the base. Fossils the Leemon of southwestern Illinois crinoid columnals and ramose bryo- are scarce; they include well pre- within the Stage. The zoans. served , carpoids, edrioas- contact of the Leemon to the Sexton The Orchard Creek is about 25 teroids, tentaculids, and trilobites. Creek Limestone is disconformable. feet thick in outcrops in the study The member is 20 to 30 feet thick in Where the Leemon is missing, the area, as well as in cores from the The- both outcrop and the subsurface. Sexton Creek Limestone rests on the bes Quadrangle. The unit is reported Identification of the Girardeau in Maquoketa Formation (Pryor and to be 60 to 70 feet thick in the Mis- well records is a bit tenuous because Ross 1962, Thompson 1991). souri part of the Ware Quadrangle the unit is thin and similar to the (Middendorf 1989), 30 to 60 feet overlying Sexton Creek Limestone. Sexton Creek Limestone thick in the Cape Girardeau Quad- The Girardeau is disconformably The type section of the Sexton Creek rangle (Satterfield 1973), 22 to 30 feet overlain by either the Leemon For- Limestone is in the Mississippi River thick in the Thebes Quadrangle mation or the Sexton Creek Lime- bluff in the SW, Sec. 27, T14S, R3W, (Pryor and Ross 1962), 50 to 80 feet stone. The Sexton Creek overlies the McClure Quadrangle (Savage 1909). thick in wells east of the outcrop in Girardeau along the top of the bluff This unit crops out northward along the Thebes Quadrangle, and as south of Harrison Creek; the contact the bluffs and also near the mouth of much as 100 feet thick in wells far- is sharp and planar to slightly irregu- Dongola Hollow in the McClure ther east in Pulaski County. lar. Where the Girardeau Member is Quadrangle. It is also exposed along eroded, the Sexton Creek directly the crest of the Harrison Creek Anti- Girardeau Limestone Member overlies the Orchard Creek Member cline in the northwestern Mill Creek The Girardeau Limestone was (Thompson 1991). and southwestern Jonesboro 7.5- named by Shumard (1855) for Cape Minute Quadrangles. A fine expo- Girardeau; locality the type is at Leemon Formation sure is just north of the mouth of Cape Rock, northeast of the city A unit previously called the Edge- Dongola Hollow in the SE NW, along the Mississippi shore. The wood Formation was renamed the Sec. 12, T14S, R3W, McClure Quad- type section in was described detail Leemon Formation by Thompson rangle (fig. 3). The lower part (in- by Satterfield (1971, p. 266) and and Satterfield (1975). The type local- cluding the basal contact) crops out Thompson (1991). The Girardeau ity of the Leemon is in the Cape on the south side of Harrison Creek has heretofore been ranked as a for- Girardeau Northeast Quadrangle. It in the center of Sec. 16, T13S, R2W, mation and placed in the Maquoketa is classified as a formation, despite Jonesboro Quadrangle. Group by Thompson (1991).

11 Alexandrian age, equivalent to the in Kentucky. Thompson (1987) suggested that the Sexton Creek ranges from the Alex- andrian into the lower part of the Clintonian Stage, Niagaran Series. Bainbridge Formation The Bainbridge Formation was named by Ulrich (1904, p. 110), and its type section was described in de- tail by Ball (1939). The type section is in the Mississippi River bluff in the SE SE NW, Sec. 24, T32N, R14E, Ware Quadrangle (Missouri). It con- sists of 120 feet of interbedded varie- gated red and green silty limestone and calcareous shale, grading up- ward into the Bailey Formation. Basal beds of the Bainbridge are cov- ered at the type section. The Bainbridge is ranked as a for- mation by some stratigraphers and as a group by others. The lower sub- division, the St. Clair Limestone, is too thin and poorly exposed to be mapped as a formation in the study area. Accordingly, we treat the Bain- .«*r bridge as a formation, containing the Seventy-Six, St. Clair, and Mocca- sin Springs Members (fig. 5).

W-* ~ - Seventy-Six Shale Member Satterfield Figure 3 Sexton Creek Limestone and St. Clair Limestone Member of Bain- and Thompson (1975) bridge Formation, north of the mouth of Dongola Hollow, NW SE NW, Sec. 12, named the Seventy-Six Shale Mem- T14S, R3W, McClure Quadrangle. The Sexton Creek is the lower unit that con- ber of the Bainbridge Formation for tains numerous thin dark chert layers; the St. Clair is the overlying thick bedded a village in the Altenburg Quadran- limestone. The height of the exposure is about 40 feet. gle, Perry County, Missouri. They described the member as vari- egated brick-red and green, partly The lithology is distinctive: Schneider Drilling Company Pearce fissile, calcareous, glauconitic shale medium brownish gray, slightly water well (Sec. 6, T14S, R2W). Re- that contains hematitic "buttons" argillaceous lime mudstone and ported thicknesses are 30 to 35 feet and ranges from a few inches to 4 skeletal wackestone, containing in the Missouri part of the McClure feet thick. We did not observe the regular layers of caramel-colored to and Cape Girardeau Quadrangles Seventy-Six Shale during this study, greenish gray chert (figs. 3, 4). Caly- (Satterfield 1973), 30 to 40 feet in the but Satterfield and Thompson fragments large Missouri part of the Ware Quadran- menid and (1975) reported that they dug it out biscuit-shaped colonies of Favosites gle (Middendorf 1989), and 15 to 40 of the bluff north of Dongola Hol-

sp. are in the upper part. feet thick in the Thebes Quadrangle 1 common low in the "NW /* NEM NWW', Sec. The Sexton Creek somewhat resem- (Pryor and Ross 1962). The Sexton 12, T14S, R3W, McClure Quadran- feet wells bles the Girardeau Limestone, but Creek is 45 to 92 thick in gle. The cited location is on the Mis- the Sexton Creek contains less shale located southeast of the Jonesboro sissippi floodplain and probably is and more chert (20-30% of the unit), Quadrangle. North of the report a misprint. The correct location it regular layers. area, in southern and has more The Jackson and Union probably is NW NW NE, Sec. 12. Sexton Creek is described in sample Counties, the unit is 30 to 95 feet logs as white to light and medium thick. An isopach map of the Alex- St. Clair Limestone Member brownish gray micritic limestone, andrian Series (Sexton Creek plus The St. Clair Limestone was defined which is argillaceous and contains Leemon) (Willman and Atherton in Independence County, , shale laminae and abundant chert. 1975) shows that the limestone thick- by Penrose (1891) and extended into The contact of the Sexton Creek ens to the north and east of the southern Illinois by Lowenstam with the overlying Bainbridge For- study area to a maximum of more (1949). It has been classified as a for-

mation is sharp, but it appears to be than 125 feet in Franklin County, mation but in this report it is consid- conformable. The Sexton Creek is Illinois. ered a member of the Bainbridge about 40 feet thick in outcrops in the Most workers since Savage (1920b) Formation. The "McClure Lime- study area. It is 30 feet thick in the consider the Sexton Creek to be of stone" shown on the stratigraphic

12 S^«t^«3»MPMPMSy CO o. LU UJ I- co cc o FORMATION MEMBER LU cc CO CO CD ORBED

Grand Tower Limestone Dutch Creek \ Ss Member

* 1 A |

A A A A A

A | A A A Clear Creek AAA A A o A A A A A > AT AAA QLU A A A A / A & / A A A A Figure 4 Sexton Creek Limestone A / A A A A with numerous closely fractured chert AAAAAAAA A A A A layers. Location is the same as in fig. 3. Grassy Knob A A A A A A The staff is 5 feet long. AAAAAA Chert AAAAAAAAAAAA column of Satterfield's geo- AAAAAA (1973) A A A A A A logic map of the Cape Girardeau A A | A |A /A A Quadrangle and Missouri portion of

I ft A I A Al m the McClure Quadrangle actually is A| — | A 1 A 0-rO the St. Clair. The name St. Clair - A/ A lA^TT clearly has priority over McClure A / A Bailey AH and is accepted in this report. A A 1 I A| Limestone 100 St. Clair crops out The Member / a I a along the Mississipppi River bluffs C~T --lA-l 50- in the McClure Quadrangle south- Al-jA -200 west of the mouth of Sexton Creek — 1 — /A^ o03 A - A A— and near the mouth of Dongola Hol- < low. Small exposures occur along CC Moccasin Z) 300 Harrison Creek Anticline in the Bainbridge Springs Mbr _J ca 100- - I — .1 - I r- I —J southwestern part of the Jonesboro to St. Clair Ls Mbr 7.5-Minute Quadrangle and north- Sexton Creek western Mill Creek Quadrangle. Alex 400 Leemon Exposures north of the mouth of Q cc Cin. Dongola Hollow are readily accessi- o Maquoketa 1 50-L ble and fairly complete. 500 St. Clair is of light The composed Figure 5 Stratigraphic column, showing Silurian and Devonian units in the gray limestone that is mottled in study area. pale red and greenish gray. It is argil- laceous lime mudstone to skeletal ins large, scattered pink to red echi- and small coiled foraminifera (Am- area, the member is 8 to 24 feet noderm stem fragments. The bed- modiscus) have been reported in thick. Satterfield (1973) reported 25

ding is thick and tabular, and it is well cuttings. The contact between to 30 feet of "McClure Limestone" in separated by stylolitic partings. The the St. Clair and the Moccasin the Cape Girardeau and McClure upper part of the unit is argilla- Springs Member is sharp, but prob- Quadrangles (Missouri portion), and ceous. In the subsurface, the St. Clair ably conformable. Pryor and Ross estimated the St. is identified as white to gray lime- Thickness of the St. Clair is about Clair to be 10 to 20 feet thick in the stone with pink, orange, and red fos- 25 feet in outcrops and wells in the Thebes Quadrangle. Well records sil fragments or "spots." Ostracods study area. Southeast of the study indicate the unit to be 30 to 50 feet

13 thick north of the study area. These type section (Ball 1939) and at out- Bailey Limestone findings are consistent with Lowen- crops in the Thebes Quadrangle The Bailey Limestone was named by stam's (1949) statement that the St. (Pryor and Ross 1962). A gradual Ulrich (1904) for the no-longer-extant Clair thickens progressively north- color change from predominantly community of Bailey's Landing on east and east from the outcrop area brick-red in the Moccasin Springs to the Mississippi River in northern in southernmost Illinois. predominantly greenish gray in the Perry County, Missouri. The Bailey The St. Clair was assigned to the Bailey marks the transition zone. is a unit of drab-colored, thin bed- Clintonian Stage of the Niagaran The lower part of the Bailey consists ded, and cherty micritic limestone Series by Thompson (1987). of gray to green cherty limestone. containing shale interbeds in the The limestone has numerous green- lower part 0- Weller and Ekblaw Moccasin Springs Member The ish gray shale interbeds that de- 1940, Croneis 1944). thick upper member of the Bain- crease in number and thickness The Bailey crops out extensively bridge Formation is the Moccasin upward. The base of the Bailey was in the Jonesboro 7.5-Minute Quad- Springs Member, named (as a forma- mapped at the lowest occurrence of rangle on both flanks of the Harri- tion) by Lowenstam (1949). The type gray, cherty limestone. son Creek Anticline and along the section of the Moccasin Springs is The Moccasin Springs is about 90 Mississippi River bluff south of At- the same as that of the Bainbridge. feet thick along the Harrison Creek wood Ridge (Nelson and Devera The Moccasin Springs is a slope- Anticline and about 145 feet thick in 1994). It extends southward through forming unit exposed only in ravines the Pearce water well in Sec. 6, T14S, the western part of the Mill Creek bluffs. and, in some places, on steep R2W, Mill Creek Quadrangle. It is re- Quadrangle and underlies large It underlies broad valleys along the ported to be 100 to 120 feet thick in areas of the McClure Quadrangle crest of the Harrison Creek Anticline the Cape Girardeau and McClure (Devera et al. 1994). Unfortunately, and crops out in the Mississippi Quadrangles (Satterfield 1973) and the few wells that penetrate the River bluffs near Dongola Hollow 100 to 130 feet thick in the Thebes Bailey lack accurate and detailed logs. and south of Sexton Creek in the Quadrangle (Pryor and Ross 1962). The Bailey is composed of light McClure Quadrangle. Most expo- Well records show that the Moccasin brown to yellowish gray, argilla- sures are fragmentary. The most Springs thickens east of the study ceous to finely silty, dolomitic lime complete sections are in gullies on area to as much as 270 feet in mudstone. Throughout the Bailey, the west flank of the Harrison Creek Pulaski County, Illinois. North of the the bedding is thin and wavy, and Anticline in the EVi SE SW, Sec. 9, study area, in northern Union and abundant chert occurs as nodules, and west of the center of the SW, Jackson Counties, the member is 180 lenses, and discontinuous layers. Sec. 16, T13S, R2W, Jonesboro 7.5- to 215 feet thick. A regional isopach Most of the chert in the upper part Minute Quadrangle. map by Whitaker (1988) shows the of the Bailey is off-white to yellow or The Moccasin Springs is com- entire Silurian succession thickening orange, and it is somewhat porous. posed of interbedded chert-free, both northward from the study area, Nodular chert having a distinctive very silty, and argillaceous lime- through Jackson County, and east- convoluted texture is common near stone (lime mudstone) and calcare- ward through Alexander, Pulaski, the top. In the lower part of the ous mudstone, shale, and siltstone. and western Massac Counties. Bailey, both limestone and chert are Both rock types are mottled and vari- The Moccasin Springs is gener- greenish and contain thin interbeds egated in brick-red, brownish red, ally considered to be of Niagaran of greenish gray shale, which is tran- purple, greenish gray, and olive age, but the upper beds may be sitional from the underlying Bain- gray. Limestone is the predominant Cayugan. Lowenstam (1949, p. 18) bridge Formation. Chert of the lithology, but shale interbeds in- reported that "the uppermost bed lower Bailey generally is dense and crease in number and thickness up- (of the Moccasin Springs type sec- occurs in thin, wavy beds rather ward. The only common fossils are tion) includes a Lissatrypa and other than in nodules. large nautiloid cephalopods in lime- fossils that suggest a late Silurian The fauna of the Bailey is sparse. stone near the base of the member. rather than Niagaran age." Grap- Sponge spicules, chitinozoans and In the study area, the Moccasin tolites from the upper Moccasin , and sparse trilobite and Springs and St. Clair are the only Springs in southern Illinois indicate echinoderm fragments are present. Paleozoic units containing much correlation with the lower Lud- Most macrofossils are in the upper red. These units are readily recog- lovian Stage of Europe (Ross 1962). third of the formation. They include nized in outcrops and well samples Conodonts from the Bainbridge of crinoid fragments and the trilobites by their distinctive color, and they northern Perry County, Missouri, in- Huntonia palacea, sp., and are thus noted on most drillers' logs. dicate late middle to early late Lud- sp. The trace fossil Zoo- An interval of shale about 30 feet lovian age (Rexroad and Craig phycos is common in the upper part thick commonly occurs at the top of 1971). On the COSUNA chart for Illi- of the Bailey. the Moccasin Springs Member. This nois (Shaver 1985), the Niagaran- The contact with the overlying shale was called the Randol shale in Cayugan Series boundary is shown Grassy Knob Formation is grada- a thesis by Rogers (1972), but this to be questionably correlative with tional. An interval of chert nodules term has remained informal. the middle Ludlovian. According to in a matrix of residual silt and clay The contact of the Moccasin Shaver, the Moccasin Springs is marks the contact in the Jonesboro Springs Member with the overlying largely Niagaran, and the overly- 7.5-Minute Quadrangle. Bailey Limestone is gradational in ing Bailey is Cayugan to Lower The Bailey is about 350 feet thick the study area, as is the case at the Devonian. along the west flank of the Harrison

14 Creek Anticline, where exposures bedded chert. In some places, this between the (or are best. South of the mouth of Harri- chert has been altered to white or Grassy Knob Chert where the Back- son Creek, a 300-foot bluff is Bailey very light gray, relatively soft and fri- bone is absent) and the Grand Tower from top to bottom. The Bailey may able microcrystalline silica or tripoli, Limestone. Savage's definition is be considerably thinner north of which resembles that of the younger used here. The unit is called Clear Harrison Creek on the west flank of Clear Creek Formation. Creek Formation rather than Clear the anticline in Sec. 9, T13S, R2W. In the subsurface, the Grassy Creek Chert because the unit is com- The Devonian-Silurian systemic Knob is predominantly chert similar posed of limestone in some areas. boundary probably lies in the lower to that observed on the outcrop. The Clear Creek Formation has part of the Bailey. Uppermost Bain- Light gray, micritic to fine grained the largest outcrop area of any bed- bridge strata contain Late Silurian cherty limestone and dolomite occur rock formation in the study area. It fossils, whereas conodont studies near the top in a few wells. crops out through most of the west- (Collinson et al. 1967) indicate the The Clear Creek Formation over- ern and southeastern parts of the upper Bailey is Lower Devonian. To lies the Grassy Knob with a conform- Mill Creek Quadrangle, much of the date, the lower and middle Bailey able, probably gradational contact western Jonesboro 7.5-Minute Quad- have not yielded fossils useful for throughout the study area. Litholo- rangle, and portions of the Ware and biostratigraphic zonation. gies of the Grassy Knob and Clear McClure Quadrangles. Many wells Creek are similar, and differentiating have been drilled into the Clear Grassy Knob Chert the two can be difficult. Abundance Creek but, unfortunately, most lack The Grassy Knob Chert was named of fossils is perhaps the best criterion detailed logs and none completely by Savage (1925) for a locality about for differentiation. Only a few poorly penetrate the formation.

10 miles north of the study area in preserved spiriferid (?) brachiopods The Clear Creek erodes to a very Jackson County, Illinois. At the type have been found in the Grassy Knob, steep and rugged topography that is section, the Grassy Knob overlies whereas the Clear Creek contains characterized by deep V-shaped the Bailey Formation and is overlain common, well preserved brachio- ravines and sharp-crested ridges. by the Backbone Limestone. The pods and trilobites. Both Grassy The drainage pattern is largely den- Backbone pinches out south of the Knob and Clear Creek are burrowed, dritic, but a trellis pattern, indicative Grassy Knob type section and does but burrows typically are horizontal of structural control, is developed in not occur in the Jonesboro Quadran- in the Grassy Knob and vertical in parts of the Mill Creek Quadrangle. gle (Devera 1994). the Clear Creek. The Grassy Knob Despite the steep topography, out- The Grassy Knob crops out on contains fewer clay partings and crops of the Clear Creek are small both limbs of the Harrison Creek more stylolites than does the Clear and fragmentary. Most information Anticline and in large areas of the Creek. Dense, thick bedded, brecci- on the Clear Creek comes from man- western Mill Creek and eastern ated and "popcorn" chert are more made exposures in silica mines and McClure Quadrangles. The upper typical of Grassy Knob than Clear quarries. part of the Grassy Knob is exposed Creek, as are yellow to off-white col- The Clear Creek Formation is 300 in the southeastern part of the Mill ors. The Grassy Knob contains less to 400 feet thick in the Jonesboro 7.5- Creek Quadrangle. This unit erodes microcrystalline silica than does the Minute Quadrangle and 200 to 300 to a very rugged topography and Clear Creek. feet thick in the Mill Creek and caps high hills such as Atwood The Grassy Knob and Clear McClure Quadrangles. Uncertainties Ridge in the Jonesboro Quadrangle Creek were not differentiated in two arise from poor exposure, compli- and Pine Knob in the Mill Creek parts of the quadrangle. The larger cated structure, and the locally prob- Quadrangle. Massive chert beds of area is in the central and south-cen- lematic lower contact. The Clear the Grassy Knob form discontinuous tral part of the Mill Creek Quadran- Creek and Grassy Knob cannot be cliffs and ledges in many places. gle; the smaller area is in the Ware differentiated in any well logs in the Bedded chert and microcrys- Quadrangle. The rocks are highly study area. In a well in Sec. 9, T15S, talline silica make up the Grassy silicified in both areas, blurring li- R1E, Pulaski County, the Clear Knob in outcrop. The chert is typi- thologic differences; lack of outcrops Creek apparently is 550 feet thick cally off-white to light gray, stained and structural complexity further and overlies Backbone Limestone. yellow or orange. Most chert is hamper interpretation. Northeast of the study area, in a dense and novaculitic, medium to The Grassy Knob is about 200 to well in Sec. 35, T11S, R1W, the Clear thick bedded, and very sparingly 250 feet thick in the Jonesboro 15- Creek overlies Backbone and is 419 fossiliferous. Chert at the top of the Minute Quadrangle. No thickness feet thick. Thus, available data indi- Grassy Knob is persistently brecci- trends are evident. cate that the Clear Creek thickens ated, and it overlies an interval of from the Ozark Dome to the Illinois highly porous, "popcorn"-textured Clear Creek Formation Basin. chert riddled with horizontal bur- The was named Two distinct lithologies of the rows. Lenses of breccia ted chert by Worthen (1866) for Clear Creek in Clear Creek are present in the study occur lower in the formation. In the the Cobden Quadrangle, north of area. The "normal" or unaltered northern part of the area, nearly mas- the Jonesboro Quadrangle. Worthen lithology, found mainly in the north- sive, ledge-forming chert occurs did not specify a type section, and ern Jonesboro 7.5-Minute Quadran- close to the middle of the Grassy his description of the limits of the gle, is limestone that contains chert Knob. The lower part of the Grassy Clear Creek is vague. Savage (1920a) lenses and layers. The "altered" Knob is predominantly dense, thick restricted the Clear Creek to strata lithology, found in most of the Mill

15 •<,

'Mr '*%(¥'

..*--

-vim**. * * •* *-? Si

Figure 6 Manmade exposure of the Clear Creek Formation near the NW corner, Sec. 11, T14S, R2W, Mill Creek Quad- rangle. The photo shows thin alternating layers of tripoli (white) and hard bedded chert (dark). Note the gently undulating layers and minor faults.

Creek and southern Jonesboro Quad- thick, but occasional layers reach The Clear Creek is fossiliferous, rangles, is bedded chert and micro- 1 foot in thickness. Some limestone particularly in the upper part. Forms crystalline silica (tripoli). near the top of the Clear Creek is identified include Dalmanites prat- silty to finely sandy, as reported by teni, Phacops cristata, sp., Unaltered lithology The unal- Allen (1985) and also as can be Leonaspis sp., Cordania sp., Eodevon- tered lithology of the Clear Creek found in sample logs from some aria arcuata, Strophostylus cancellatus, Formation is limestone containing wells in the study area. and Amphigenia curta. Strophemenid subordinate bands and nodules of Chert in unaltered Clear Creek is and spiriferid brachiopods and echi- chert. Typical exposures occur along dull white to light gray, slightly mot- noderm fragments are particularly tributaries of Cany Creek in the tled, and resembles unglazed porce- common. Trace fossils include verti- western part of Sec. 10 and the north- lain. In the upper Clear Creek, chert cal burrows, borings in ernmost part of Sec. 15, T12S, R2W. occurs in distinct lenticular beds and shells, and large domichnia cavities. In these areas and elsewhere, the layers of nodules, 1 to 4 inches thick. limestone is uniformly light gray Downward, chert generally blends Altered lithology Where it is and light brownish gray, faintly mot- into the enclosing limestone. Chert altered, the Clear Creek Formation is tled, very siliceous lime mudstone. of the middle and lower Clear Creek composed of chert and microcrys- The texture is generally aphanitic, is mostly tripolitic and calcareous, talline silica. Limestone was leached but some limestone appears very grading to highly siliceous lime- out and/or replaced by silica. finely granular. Scattered bioclasts stone. Contacts between tripolitic Altered Clear Creek is found in are present; they are largely echino- chert and limestone are intricately much of the study area (see the red derm and trilobite fragments, as intergrown; in places, the rock is dashed lines on the geologic maps well as whole shells of strophe- chert with "nodules" of limestone. of Nelson and Devera 1994, and menid and spiriferid brachiopods. This type of rock exfoliates on Devera et al. 1994). Well records Brachiopods are common in the up- weathered surfaces of stream banks. show that the Clear Creek is altered per part of the Clear Creek and un- Digging into unweathered rock to at least 400 feet below the surface common in the middle and lower yields siliceous limestone and lesser in some places. parts. Bedding is thin and wavy to amounts of chert, similar to that Bedded chert of the altered Clear nodular; most beds are 1 to 4 inches found near the top of the Clear Creek. Creek is mottled white to light gray,

16 *• r:

, f

i 4, %>.*> ^Sfc

Figure 7 Abandoned underground silica mine in white tripoli of Clear Creek Formation, overlain by hard, fractured, brownish orange bedded chert. The tunnel was driven through the crest of a ridge; it served room-and-pillar workings within the ridge and also provided a haulage road to mines on the other side of the ridge. The location is in the SE NE, Sec. 23, T14S, R2W, Mill Creek Quadrangle.

commonly stained red, yellow, and stone. Some clay, silt, and sand is nearly white, soft enough to be dug orange. The chert is dull to slightly distinctly laminated, however, indi- with hand tools, and indistinctly vitreous. Some of it is vuggy, contain- cating deposition from water in bedded. Most tripoli, however, is ing irregularly shaped cavities and open fissures and cavities. Good partly stained orange and red, and vertical cylindrical tubes (burrows ?) exposures of fissures filled with lami- contains thin layers and lenses of fri- less than 0.5 inch in diameter. Bed- nated sediment occur along Jackson able to hard, fractured, bedded chert. ding is thin, lenticular, and undulat- Creek in the NW NW, Sec. 24, T14S, Large clean exposures of interbed- ing. Occasional beds, as much as 2 R2W, Mill Creek Quadrangle. Other ded tripoli and chert are in the feet thick, of vuggy to partly brecci- clay layers and veins are not lami- active Lone Star Industries open-pit ated chert are interspersed with nated and pinch and swell in irregu- mine (NE NW, Sec. 15, T14S, R2W) thinly bedded chert. All this rock is lar fashion, indicating that clay was and the abandoned Jason no. 2 open- closely fractured and faulted; it is injected into fissures in the rock. pit mine (near the center of the SE, folded into small open synclines, Altered Clear Creek contains the Sec. 22, T13S, R2W, Mill Creek Quad- anticlines, and monoclines. Dips same fossils as unaltered limestone. rangle). Tripoli also is visible at the steeper than 20° are uncommon, Fossils are generally well preserved portals of many abandoned under- except along large faults. and are most abundant near the top ground silica mines (fig. 7). Unlithified clay, silt, and fine of the formation. Chert of the altered Clear Creek sand occur along bedding planes Soft microcrystalline silica (trip- Formation forms ledges and small and fractures in altered Clear Creek. oli) is interlayered with bedded cliffs along steep hillsides and Unweathered clay commonly is chert in the altered Clear Creek For- ravines in parts of the Mill Creek light gray to greenish gray and mation (figs. 6, 7). Most tripoli layers Quadrangle. Ledges as high as 50 grades, in part, to silt and fine sand are 3 to 10 feet thick, but they rarely feet occur just north of the center of composed of chert and tripoli frag- reach 50 feet or more. In some expo- the west line of Sec. 27, T14S, R2W. ments. Weathered clay is commonly sures, chert and tripoli are thinly Other extensive exposures are in the reddish or orange brown. Most clay interbedded (fig. 6). Layers are some- southeastern and west-central parts layers are less than 2 inches thick. what lenticular, although little infor- of Sec. 14, T14S, R2W. Ledge-form- Lamar (1953) attributed clay layers mation is available on their lateral ing chert is indicated with a stippled to dissolution of argillaceous lime- extent. The purest form of tripoli is pattern on the Mill Creek geologic

17 map (Devera et al.1994). This chert is white to light gray and grayish orange; weathered surfaces are com- monly dark gray and very rough and jagged. It is dull to slightly vitre- ous, very hard, and more or less vuggy due to selective weathering of burrows and trackways produced by organisms prior to lithification of the lime mud. From a distance, the chert appears thickly bedded to mas- sive; but, on close examination, thin, crinkly, and undulating bedding is evident on many layers. Much of the ledge-forming chert is recemented intraformational breccia of angular chert fragments and shows residual layering (fig. 8). Ledge-forming chert grades laterally within short distances to poorly exposed thin bedded chert and tripoli. Contrary to the interpretation of Berg and Masters (1994), this ledge- Figure 8 Ledge-forming chert of Clear Creek Formation in the SVi SW SE, forming chert is not confined to any Sec. 14, T14S, R2W, Mill Creek Quadrangle. Although the chert is brecciated, the particular stratigraphic levels in the bedding is partially intact. Clear Creek. In some areas, particu- larly in Sec. 14, T14S, R2W, ledge- forming chert follows northeast- trending faults or fracture zones. In the western Mill Creek Quadrangle, massive or brecciated chert com- monly crops out at the tops of steep slopes, forming a "caprock" beneath Quaternary surficial materials. Such chert apparently is a product of surfi- cial weathering. The only good exposure of the Clear Creek-Grand Tower contact is in the bank of Sexton Creek behind Pleasant Valley Church in the NW NW, Sec. 21, T14S, R2W, Mill Creek Quadrangle. Here the Dutch Creek Sandstone lies with sharp, uneven contact on a breccia of chert frag- ments, angular sandstone clasts, and contorted sandstone laminae in a sandstone/ matrix of soft clay (fig. 9). This brec- clay breccia cia may be insoluble residue of a sandy, argillaceous limestone. Although the sharp contact at the base of the sandstone bed indicates a disconformity, the presence of sandstone in the breccia suggests a fractured gradational, conformable contact. chert of the Elsewhere in the study area the Clear Creek contact is covered or is obscure Formation because of leaching, silicification, in situ brecciation, and faulting. The Formation lacks Clear Creek marker Figure 9 Contact of Dutch Creek Sandstone (above) to Clear Creek beds that might aid detection of a Formation. The sandstone contains numerous well preserved molds disconformity (if present). Thickness of fossils. Underlying the sandstone (middle of photo) is an interval variations of the Clear Creek are too of angular sandstone clasts in a matrix of sandy clay. Fractured chert poorly known to assess possible pre- is below that; clay is injected into the fractures. The staff is 5 feet long. Grand Tower erosion.

18 ent in most exposures, particularly spiriferid brachiopods, bivalves, rugose corals, conularids, the prob- lematic fossil Pleurodictyum, crinoid stems, and poorly defined burrows. Well samples indicate that the sand- stone commonly has calcite cement. The Dutch Creek commonly is brecciated in the area of altered rocks in the southern Jonesboro and Mill Creek Quadrangles. The breccia consists of sandstone clasts as large as 2 feet across, as well as lesser amounts of light-colored chert clasts, which are cemented by silica and iron oxide (fig. 10). Clasts commonly have rounded corners and fit adja- cent clasts in jigsaw-puzzle style, showing that little fragment dis- placement occurred after the rock was shattered. In many outcrops, Figure 10 Brecciated Dutch Creek Sandstone, consisting of angular sandstone only certain layers are brecciated clasts cemented by silica and iron oxide. Location is the SE NW NW, Sec. 23, and adjacent layers are undisturbed. T13S, R2W, Mill Creek Quadrangle. Joints, where present, penetrate both clasts and matrix. Evidently, jointing took place after the sandstone was Grand Tower Limestone to 25 feet thick. Records of four wells brecciated and recemented. The Grand Tower Limestone was in the Dongola Quadrangle, just east The Dutch Creek contains a basal named for Grand Tower (Jackson of the Mill Creek Quadrangle, indi- conglomerate on the south face of County, Illinois), which is about 10 cate that the Grand Tower is less Burner Hill, about 1,800 feet from miles northwest of the study area than 10 to about 40 feet thick in this the south line and 2,000 feet from (Keyes 1894). At the type locality, the area. Only two of these wells en- the east line, Sec. 24, T14S, R2W The Grand Tower is predominantly light- countered limestone in the upper conglomerate consists of scattered colored, slightly sandy, and cherty Grand Tower. angular light gray chert granules limestone. The Dutch Creek Sand- The Grand Tower Limestone in and silicified crinoid, bryozoan, and stone Member is at the base. southwestern Illinois is assigned to horn-coral fragments in a matrix of The outcrop of the Grand Tower the Stage, or lower part of sand cemented by iron oxide. The extends due south from the center of the Middle Devonian Series. The conglomerate indicates a disconfor- the north line of the Jonesboro 7.5- equivalent unit in western Kentucky mity at the base of the Dutch Creek. Minute Quadrangle to the center of and southwestern is the Jef- The Dutch Creek typically is 10 to 15 the north line of the Mill Creek fersonville Limestone (Shaver 1985). feet thick, but it reaches 25 feet. The Quadrangle, and thence south-south- upper contact is gradational. east to the Cache Valley south of Dutch Creek Sandstone Mem- Elco. Downfaulted inliers occur west ber Savage (1920a) named the Dutch Unnamed limestone member of the main outcrop belt. There is no Creek Sandstone for Dutch Creek in The unnamed, upper limestone limestone in the Grand Tower in the Jonesboro 7.5-Minute Quadran- member of the Grand Tower crops much of the study area; only the gle. No type section was designated, out in the northern half of the Jones- Dutch Creek Sandstone is present. but the unit is well exposed on the boro 7.5-Minute Quadrangle and is Where limestone is present (north- west-facing bluff near the mouth of present in wells east of the outcrop ern part of Jonesboro 7.5-Minute Dutch Creek in the NE, Sec. 19, T12S, belt in and near the study area. The Quadrangle), the Grand Tower was R2W. The Dutch Creek originally lower part of the limestone member mapped as a separate unit. Where was a separate formation, but was re- is typically white to light gray, fine limestone is absent, the thin Dutch vised to a member of the Grand to coarse grained skeletal grainstone Creek and the overlying St. Laurent Tower by Meents and Swann (1965). that contains little, if any, silt and Formation were combined as a sin- The Dutch Creek is white to very clay. The upper part is largely darker gle map unit. light gray, very fine to medium colored skeletal packstone and The Grand Tower thins south- grained quartz arenite, composed of wackestone. The limestone member ward in the study area. Four well subrounded to well rounded and is medium to thick bedded through- logs in the northeast quarter of the frosted quartz grains. The sandstone out, commonly crossbedded, and Jonesboro 7.5-Minute Quadrangle in- crops out as broken ledges, but it is slightly cherty. Some limestone in dicate thicknesses of 58 to 125 feet. more commonly found as large well cuttings contains well rounded, In the Mill Creek Quadrangle, where blocks displaced downslope by soil frosted quartz sand, similar to that only the Dutch Creek Sandstone is creep. Bedding is slightly irregular of the Dutch Creek. Fossils include present, the Grand Tower is only 10 and indistinct, and generally 0.5 to 3 echinoderm fragments and abun- feet thick. Molds of fossils are pres- dant whole and broken brachiopods,

19 corals, and trilobites. Large crinoid St. Laurent Formation complex fashion. It is not a layer- chonetid brachio-pods cake succession, stems and Dake (1918, p. 175) and S. Weller as visualized by are abundant in the upper Grand and St. Clair (1928) defined and North (1969) and other workers. The Tower. mapped the St. Laurent Formation only subdivision of the St. Laurent Good exposures of the limestone in Ste. Genevieve County, Missouri. we could identify was the Rendle- member were found in three places The type section comprises steeply man Oolite Bed (fig. 11), and we are in T12S, R2W: in the bank of Green dipping strata, 275 feet thick, along not certain that this is a single bed. Creek just south of Illinois route 146, St. Laurent Creek. Strata equivalent Aconodont study by Orr (1964) NW NE NW, Sec. 23; in a tributary to the St. Laurent in southern Illinois indicated that the St. Laurent ranges of Cany Creek just east of route 127 were named the Alto and Lingle For- from (late Middle Devon- north of the center of Sec. 10; and on mations and the Misenheimer Shale ian) to early (early Late the west-facing bluff in the WVi SE by Savage (1920a). Savage did not Devonian). Shaver (1985) assigned SE, Sec. 19. map these units, and his descrip- the St. Laurent Formation to the The limestone member of the tions of them are sketchy. Geologists Givetian Stage. The St. Laurent is Grand Tower is absent in the south who later mapped in southern Illi- equivalent to the Sellersburg Lime- half of the Jonesboro 7.5-Minute nois combined the Misenheimer, stone in western Kentucky and the Quadrangle and in the Mill Creek Lingle, and Alto as a single unit, and in Indiana Quadrangle. In some areas, plastic they recommended the name St. (Shaver 1985). clay and silt containing nodules, len- Laurent be adopted (J. Weller and ticular beds, and fragments of light- Unaltered lithology The St. Ekblaw 1940, J. Weller 1944). Never- Laurent Formation is an interval of colored, dense, dull to slightly theless, the names Alto and Lingle limestone, dolomite, shale, and silt- vitreous chert were found at the po- persisted in Illinois literature (fig. 11). stone, all of which intertongue in sition of the limestone. A good expo- The Misenheimer Shale eventually complex fashion (fig. 12). The car- sure can be found in the south bank was reduced to a member of the Lin- bonate rocks are mostly dark, of the creek in You-Be-Damned Hol- gle (North 1969). micritic, cherty, and very argilla- low in the SE SW NW, Sec. 35, T13S, We are formally extending the St. ceous to silty. Medium to dark gray, R2W. The material is thought to be Laurent Formation into Illinois and olive gray, and brownish gray are insoluble residue from dissolution rejecting the Alto and Lingle Forma- the usual colors. A dark punky rind of the limestone. tions. The Lingle and Alto Forma- develops on weathered surfaces. The contact with the overlying tions cannot be distinguished Much of the rock is dolomitic lime St. Laurent Formation is generally reliably either in outcrop or in sub- mudstone, lithographic to very sharp. Regionally, this contact is surface. Even at the type localities, finely granular, containing scattered reported to be disconformable on the Lingle and Alto are not lithologi- bioclasts. Bedding is thin, typically the margins of the Illinois Basin, cally distinct. Comparison of sec- 1 to 6 inches. Chert commonly com- and becomes conformable toward tions (fig. 12) shows that the St. poses 20% to 30% of the rock and the center of the basin (Meents and Laurent contains siliciclastic and car- occurs as small ovoid or irregular Swann 1965, Shaver 1985). bonate rocks that intertongue in

Cooper et al. Orr 1964 and Savage 1920a North 1969 This report 1942 Norton 1966

Mountain Glen Mountain Glen Grassy Creek Grassy Creek Sh in New Albany Shale Shale Shale Shale New Albany Group

Alto Formation Alto Formation Alto Formation Alto Formation

Walnut Grove Rendleman s c Ls Member / Oolite Bed Lingle Formation Lingle Formation g ooooooooo o o o o o o Misen- Lingle Misenheimer heimer £ Lime- Sh Member Shale £ St. stone St. / Misen- (facies) CD Laurent c Tripp Ls Mbr Misenheimer Laurent ~> heimer Fm Howardton Shale Fm > Shale Ls Member Grand Tower Grand Tower Grand Tower Grand Limestone Limestone Limestone Grand ."ower Tower Dutch Creek Dutch Creek Dutch Creek Dutch Crk Dutch Crk Ls Ls Sandstone Sandstone Sandstone SsMbr SsMbr

Figure 11 Chart showing development of lithostratigraphic classification of Middle and Upper Devonian strata in southwestern Illinois.

20 nodules and as discontinuous lay- higher in the study area than else- geologists (e.g., Collinson et al. 1967, ers. It is dark gray to black, some- where in southern Illinois. Outside Cluff et al. 1981) classify the New what vitreous, and dense. of the Jonesboro Quadrangle, the St. Albany as a group in Illinois, it is A bed or lens of light gray coarse Laurent generally consists of argil- ranked as a formation in this report crinoidal and oolitic grainstone 1 to laceous and silty carbonate rocks because it cannot be subdivided. 4 feet thick was observed at several with only thin shale interbeds. The New Albany is very dark outcrops and in cuttings of several Thickness of the St. Laurent in gray to black, brittle, highly fissile, wells (fig. 12). This is probably the the study area ranges from 80 to 200 siliceous or finely silty shale. It weath- Rendleman Oolite Bed of North feet, thinning southward. Region- ers to dark olive gray or brownish (1969). Oolitic limestone generally ally, the St. Laurent is thickest in gray and splits into paper-thin lay- occurs near the middle of the St. Union County, Illinois, and Perry ers. The uppermost 1 foot of the Laurent, near the base of a limestone and Ste. Genevieve Counties, Mis- shale is less fissile and is mottled in interval and overlying an interval of souri (North 1969). dark greenish gray and olive gray. shale and siltstone. The best outcrop The St. Laurent is overlain discon- The only common fossil is Tasman- is in the bank of Darty Creek, 900 formably by the New Albany Shale ites, an algal test that is called feet from the south line and 700 feet or by the Springville Shale where "spores" or "Sporangites" in many from the east line of Sec. 10, T12S, the New Albany is absent. The St. sample logs and older reports. R2W, Jonesboro 7.5-Minute Quad- Laurent-New Albany contact is ex- A very thin sandstone or sandy rangle. (The name "Darty Creek" posed (digging may be necessary) zone occurs locally at the base of the does not appear on the topographic along Darty Creek, in the SW NW New Albany. Several authors called map; the creek shown at this loca- SW, Sec. 11, T12S, R2W. Springville this zone the Sylamore Sandstone at tion bears no name. The name was directly overlies St. Laurent in a formation rank (Collinson and Scott used by J. Weller and Ekblaw [1940] streambank near the center of the 1958, Collinson and Atherton 1975, and in several subsequent publica- south line of Sec. 1, T13S, R2W, and Cluff et al. 1981). Clearly, a unit that tions, and there is no doubt regard- at the south border of the Jonesboro is only a few inches thick should not ing the location of the outcrop.) 7.5-Minute Quadrangle in the east be classified as a formation. The

Available data are insufficient to bank of the large stream in the NW, Sylamore Sandstone in southern Illi- show whether the oolitic limestone Sec. 23, T13S, R2W. At the latter out- nois is herein revised to the Syla- represents a single bed or a series of crop, the upper surface of the St. more Sandstone Bed in the New lenses. Laurent is thickly encrusted with a Albany Shale. Exposures of the Syla- The St. Laurent contains echino- botryoidal black mineral thought to more Bed are reported in the bank of derm stems and plates, spiriferid be manganese oxide. Darty Creek, in the SE SE, Sec. 10, and chonetid brachiopods, fenestrate T12S, R2W, Jonesboro 7.5-Minute bryozoans, trilobites, and rugose cor- Altered lithology Carbonate Quadrangle (Collinson and Scott als. Silicified corals are abundant in rocks have been dissolved and silt- 1958), and the bank of Clear Creek the lower part. A diagnostic fossil of stones and shales bleached in the in the NV4 NE NE, Sec. 34, T11S, the basal St. Laurent is the "button area of altered rocks, as indicated on R2W, Cobden Quadrangle (Orr 1964, coral" Microcyclus discus. the geologic maps of Nelson and p. 3). Digging is required to reveal Shale and siltstone constitute less Devera (1994) and Devera et al. these occurrences. than 20% to more than 80% of the St. (1994). Shales typically are dull The New Albany is absent in Laurent in the study area. These white to light yellowish gray, locally most of the area of altered rocks. The rocks vary from light gray, olive mottled, and banded with pale only New Albany we observed in gray, brownish gray, and dark gray green, pink, and violet. Lamination the altered area was float in a stream to nearly black; they are generally and fissility are preserved. Most bank near the center of the east line calcareous or dolomitic, grading to altered rock is very porous and low of Sec. 2, T14S, R2W, and shale that argillaceous and silty carbonate in density. Such rock probably was had been cast out from a manmade rock. Shale and siltstone are fissile originally limestone or dolomite pit about 0.5 mile south of the and have well developed planar to with a high silt/clay content. Dark stream. The shale at those places slightly wavy or lenticular lamina- brownish gray vitreous chert layers did not differ noticeably from nor- tions. Trace fossils (vertical and hori- and nodules are common in altered mal New Albany. St. Laurent. St. is diffi- zontal burrows and escape The Laurent The New Albany is 55 feet or thin- cult to distinguish the Spring- struc-tures) are common, but body from ner in most of the study area, but it fossils are rare. Some siltstone ville Shale in areas where it has been may reach 80 feet in Sec. 29, T12S, grades to very fine grained, thinly strongly altered. R2W (fig. 13). The New Albany is bedded sandstone. Dark brown to absent as a result of pre-Springville New Albany Shale dark gray vitreous chert nodules erosion in the southeastern Jones- and bands occur in shale and silt- The Upper Devonian /Kinder- boro 7.5-Minute Quadrangle and in stone at some outcrops. hookian black shale in southern Illi- most of the Mill Creek Quadrangle. The succession of beds in the St. nois has been alternatively called Eastward, in the Dongola Quadran- Laurent is highly variable (fig. 12). Chattanooga, Mountain Glen, gle, the New Albany thickens to 50 In general, there is more carbonate Grassy Creek, and New Albany to 110 feet. About 60 miles east of the rock in the upper portion and more Shale by various geologists. The study area, the New Albany reaches shale and siltstone in the lower por- name New Albany Shale (Borden a maximum of more than 450 feet tion. The siliciclastic content is much 1874) has priority and is accepted by (Cluff etal. 1981). most recent authors. Although some

21 North-trending ravine

1 Sturdevant no. 19 N /2 NE, Sec. 34, T11S, R2W Burr Lambert no. 1 Cobden Quadrangle State Pond Well Hagler Well NE NE NW, Sec. 14, T12S, R2W SE NW SW, Sec. 28, T10S, R2W Jonesboro Quadrangle Cobden Quadrangle

A | 7~^~A I A ZE T^T -/••ft-/- ~rvA-/77 A a-/ a-77 a/- A/ fr- / 5 1 5T /!.. /..^ /J

p I a a / a

.^_.. .*/ I 1 --I---/

A -I I slat. Assoc. Petroleum Co. no. 1 - Hays Well ^^ Ia'-I A-l W SW SE, Sec. 21, T10S, R3W/ ^^^ si a-ia^=~t Gorham Quadrangle

A I A— I A-Al A — A —

A — .. A o o oo" 4 - • a - a loo — A • A A - / I I \ \ .<-*#e \. %^ \ / - - I I 0° O 10 O |o , , \ / \ / ill a|-a| al >l - / al- /A-zxT

I - I / - /- - I- I- / / covered

o | o o I -

[ TO o | O O

covered

A A | a ~F r-r - I- - I - datum - base of --I- ~ St. Laurent Fm covered

Grand Tower Limestone

B W Clear Creek Formation j^. A I A Z ±

Figure 12 Graphic columns illustrating the lithologic variability of the St. Laurent Formation in and near the study area. (1) National Associated Petroleum Company no. 1 Hays well: the column was made on the basis of electric log and sample study by Elwood Atherton. (2) Burr Lambert no. 1 Hagler well: the column was made on the basis of electric log and sample study by Howard Schwalb. (3) North-trending ravine: the column is a measured section by Orr (1964) and Norton (1966). This is

:: '

1» 2» 5 mi 1 I — 5 km

Roadcut ravine on south side of Route 146 NE NE NW, Sec. 23, T12S, R2W Jonesboro Quadrangle

Rigney no. 1 • 6 Hileman Well NW SE SW, Sec. 21, T13S, R1W Jonesboro : Dongola Quadrangle : 15-Minute covered Quadrangle >•

—_^: .7^- r!~. _ A ..-/ ••• -/•• covered ^~p | FaE Streambed and adjacent |"— — A /A | A hillside, Lingle Creek covered A • — | A A Vz SW SW, Sec. 26, T13S, R2W - I- I- I- A j-A /- Mill Creek Quadrangle A !••• a a — - I - -u i--i- / & I M ••• • I A | A- - l I- A I o~oT= . -l- - Bend\eraao O 0| O O I Springville i - i Bed o | o o | o o | o SS Shale __?• OoWe

i b ia &—nr

0-rO

10- poorly exposed and structurally -5 complex 20- i r 30-_

I -10 A A I A A I

A A I A |A^ A A 40- A I I It A B

A | A I A A 50 ft -Ll5 m

I a a aTfl Clear Creek Formation • • I S I maAl7TT

the type section of the Alto Formation (Savage 1920a). (4) Sturdevant no. 19 State Pond well: the column was made on the basis of sample study by George Ekblaw (5) Roadcut and ravine: the measured section is by Norton (1966) and W.J. Nelson. (6) Rigney no. 1 Hileman well: the column was made on the basis of sample study by Elwood Atherton. (7) Streambed and adjacent hillside: the measured section is by Norton (1966). This is the type section of the Lingle Formation (Savage 1920a).

OCT 2 9 1996

II uluu ouKVEY 23 NEW ALBANY SHALE (Workman and Gillette 1956), the Chouteau does not meet the stand- ard of mappability required for a formation (North American Strati- graphic Code, Article 24d). The unit probably should be reclassified as a member in southern Illinois, yet the Chouteau is not allied lithologically to either the New Albany Shale below or the Springville Shale above. The matter of rank of the Chouteau is thus deferred, pending further study. The Chouteau is exposed at the spillway of State Pond in Sec. 14, T12S, R2W, and along Darry Creek, in the SW NW SW, Sec. 11, T12S, R2W, Jonesboro 7.5-Minute Quadrangle. Large float blocks of the limestone occur at several other sites north of Illinois route 146. The Chouteau also was identified in the logs of several wells near the east edge of the study area. It is about 1 foot thick at all of these places and was combined with the Springville Shale in map- ping (Nelson and Devera 1994). The Chouteau is absent south of route 146. The Chouteau is medium brown- ish gray lime mudstone that is mot- tled with greenish blue and contains scattered coarse fossil fragments, mainly echinoderm stems. The lime- stone is argillaceous, particularly near the base. Angular fragments of green clay, which were probably eroded from the subjacent New Albany Shale, are common. The up- per contact is sharp, slightly irregu- lar, and possibly disconformable. Collinson and Scott (1958) discussed a weathering profile in the Chou- teau and overlying shale at the State

Figure 13 Isopach map of New Albany Shale. Contour interval is 20 feet. Pond section but considered the dis- conformity local. The Chouteau is assigned to the The New Albany is disconform- the shale here is probably entirely Kinderhookian Series on the basis of ably overlain by the Springville Late Devonian. the conodont fauna (Collinson and Shale throughout the study area. Scott 1958). The contact is well exposed at the Chouteau Limestone spillway of State Pond in Sec. 14, Savage (1920a) observed thin calcare- Springville Shale T12S, R2W, Jonesboro 7.5-Minute ous lenses at the base of the type The Springville Shale was named by Quadrangle, and in the south bank Springville Shale in the Mill Creek Savage (1920a) for the village of of Darty Creek, in the SW NW SW, Quadrangle; J. Weller (1948) pro- Springville, which is near the south- Sec. 11 of the same township. posed the name Darty Limestone for east corner of the Jonesboro 7.5- The age of the New Albany in these lenses. Later, Workman and Minute Quadrangle. No specific type Illinois ranges from late Givetian Gillette (1956) and Collinson and section was designated, but Savage through Kinderhookian (Early Mis- Scott (1958) correlated the unit with listed several places near Springville sissippian) (Shaver 1985). Consider- the Chouteau Limestone (of Swal- where the shale is well exposed. The ing that the New Albany in the low 1855) and suppressed the name Springville is a unit of siliceous report area is thin, and bounded Darty. The name Chouteau is now shale and siltstone, typically green- above and below by disconformities, generally accepted. Because it is less ish gray where unaltered. Its thick- than 10 feet thick in southern Illinois ness ranges from 8 to 88 feet (fig. 14).

24 State Pond Member The State SPRINGVILLE SHALE Pond Member of the Springville Shale is a thin unit of soft greenish shale that directly overlies the Chouteau Limestone at the spillway of State Pond, in the SW NW SW, Sec. 14, T12S, R2W, Jonesboro 7.5- Minute Quadrangle (Collinson and Scott 1958). The member occurs else- where in the study area but is poorly exposed. It is composed of clay shale that is bright green to dark greenish or olive gray, mottled, soft, and slightly calcareous. Black, phos- phatic (?) pebbles occur in the State Pond Member at the type locality. A few inches of quartz sandstone are at the base of the State Pond where it disconformably overlies the St. Laurent Formation southwest of Kornthal Church, in the SE SE SW, Sec. 1, T13S, R2W, Jonesboro 7.5- Minute Quadrangle. The State Pond Member is 1 to 5 feet thick and grades into overlying silty shale of the upper member of the Springville. Collinson and Scott (1958) re- ported that the State Pond Member contains conodonts indicating earli- est Valmeyeran age.

Upper member The upper (un- named) member of the Springville Shale makes up 90% or more of the thickness of the formation. In areas where it is not altered, the upper member is composed of medium greenish gray to bluish gray silty or siliceous shale and siltstone. This rock is slightly fissile to blocky and occurs in irregular or lenticular lay- ers 1 to 2 inches thick. The rock coarsens upward, and layering be- comes thicker toward the top. Most of the shale and siltstone is only slightly calcareous, but the upper Figure 14 Isopach map of Springville Shale. Contour interval is 20 feet. part approaches a silty limestone in some areas (e.g., along Darty Creek).

Trace fossils, consisting of small bur- west of Kornthal Church in Sec. 1, The Springville is 35 to 75 feet rows and trails, are uncommon; no T13S, R2W. The upper contact is ex- thick at most places in the study body fossils were found. In places, posed just south of the church, and area; however, it ranges from 8 to 88 the lower part contains discontinu- the lower contact just east of the feet thick in the area. A comparison v ous layers of clay shale that weath- road junction near the south line of of the Springville (fig. 14) and New ers chocolate brown to purplish Seel. Albany isopachs (fig. 13) shows that brown. Small quartz-filled vugs The contact with the overlying the Springville commonly is thin in occasionally can be found in the Fort Payne Formation is well ex- areas where the New Albany is thick upper part of the Springville. posed in many places, and it is in- and vice versa. This pattern indicates Good exposures of the upper variably sharp and planar or slightly that the Springville filled depres- member can be seen at the Darty uneven. As Collinson and Scott sions eroded into the New Albany. Creek and State Pond localities, as (1958) reported, this contact prob- The upper member of the Spring- well as in a roadcut and adjacent ably is disconformable. The top of ville Shale is assigned to the lower abandoned shale pit in the NE, the Springville was used as struc- part of the Valmeyeran Series (Col- Sec. 23, T12S, R2W. Outcrops also tural datum on the Jonesboro geo- linson and Scott 1958, Shaver 1985). are common along the creek south- logic map (Nelson and Devera 1994).

25 ""9****.

Figure 15 Basal Fort Payne Formation and upper Springville Shale in the altered area. The closely jointed, tabular-bed- ded rock is "calico rock" of Springville. The dark crumbly material above is ganister of the Fort Payne. Locality is in You- Be-Damned Hollow, NE SE NE, Sec. 35, TBS, R2W, Mill Creek Quadrangle.

Altered lithology In the Mill cult to distinguish. Both formations actually Fort Payne. An interval of Creek Quadrangle and part of the yield "calico" colors, although colors 49.5 feet of bedded chert, which Lin- southern Jonesboro 7.5-Minute of the St. Laurent generally are paler eback (1966, p. 37) erroneously Quadrangle, the Springville Shale is than those of the Springville. Also, included in the Ullin type section, is altered to "calico rock" (Lamar 1953), most of the altered St. Laurent con- actually Fort Payne. a dull white to light gray siliceous tains nodules and thin bands of dark Unaltered rock that is banded and blotched gray to brown vitreous chert, a fea- Unaltered lithology is with pink, magenta, and orange ture that is absent in the Springville. Fort Payne dark-colored, highly brown. Most "calico rock" has thin, siliceous and cherry, fine grained or flaggy bedding but, near the top of Fort Payne Formation micritic dolomite and dolomitic lime- colors the Springville, blocky layers reach The Fort Payne is a formation of bed- stone. Typical are medium- 12 to 18 inches thick (fig. 15). In ded chert and siliceous limestone, dark to dark gray, olive gray and some outcrops, "calico rock" occurs named for Fori Payne, brownish gray. Weathered surfaces in tabular layers 4 to 8 inches (10- (Smith 1890). The name Fort Payne are dark and commonly bear a silica. Texture is 20 cm) thick, each layer separated by was first used formally in Illinois by porous rind of thinner intervals of ripple-laminated Lineback (1966). Previous authors micritic to very finely granular. Bio- siliceous rock. "Calico rock" rings used such names as Osage limestone, clasts, consisting of echinoderm frag- small brachiopods, are when it is struck with a hammer. Burlington-, and ments and In some areas, the upper Spring- Hartline chert. uncommon. Bedding is uneven to relatively thin; ville is altered to dark brown or Although Lineback (1966) stated wavy and most beds orange semivitreous chert that that the Fort Payne does not crop are 2 to 12 inches thick. The Fort resembles the overlying Fort Payne out in the Jonesboro Quadrangle, we Payne is commonly glauconitic; glauconite occurs as dark green to Formation. In general, the lower mapped it through the eastern Mill the size of part of the Springville is less Creek and Jonesboro 7.5-Minute black grains, which are quartz geodes are strongly altered than is the upper Quadrangles and northward into fine sand. Small part. Some of the lower Springville the Cobden Quadrangle. Fort Payne common. Chert, which commonly of the rock, retains its green color, albeit slightly in this area is similar to typical Fort makes up 20% to 30% bleached. Payne in Alabama (Thomas 1972). occurs as irregular bands and nod- In areas of intense alteration, the Some rocks that Lineback assigned ules that are dark gray to brown and Springville and St. Laurent are diffi- to the overlying Ullin Limestone are dull. Weathered chert from the Fort

26 Figure 16 Siliceous limestone of the Fort Payne Formation cropping out north of Lingle Creek near the center of the SW, Sec. 30, T13S, R1W. This is a typical exposure of unaltered Fort Payne in the Mill Creek Quadrangle.

Payne is light to medium brownish of the Fort Payne gradually changes coarse wood grain. Chert is dull to gray and has coarse, wavy banding upward to medium gray, very fine slightly vitreous, dense to slightly that resembles wood grain. In the to fine grained skeletal limestone vesicular, and commonly contains northern Mill Creek Quadrangle, the that contains less chert and dissemi- small quartz geodes. Beds are gener- Fort Payne commonly forms ledges, nated silica. Intertonguing Fort ally tabular and range from 1 to 24 and weathered surfaces are rough Payne and Ullin can be seen in out- inches thick, but most are 6 to 18 and jagged. Weathering accentuates crops near the boundary of the inches thick. The basal part is most the layering, which is faint in fresh Jonesboro and Mill Creek 7.5-Minute strongly silicified. exposures (fig. 16). At unweathered Quadrangles. In this area, the Fort Ganister (Lamar 1953) is granular, exposures (such as the abandoned Payne thickens southward from less pelletal, and very porous. It is red- quarry near Illinois route 127 in the than 20 feet to more than 100 feet dish orange, dark red, or burnt

NE SW SW, Sec. 19, T13S, R1W), the within a distance of 0.5 mile. orange in most exposures, but it is Fort Payne is thick bedded lime- The Fort Payne is thinnest, 15 feet white to light gray in some areas. It stone that has shaley partings spaced or less, in the southeastern Jones- is more difficult to dig ganister from 1 to 3 feet apart. boro 7.5-Minute Quadrangle (fig. 17). this formation than it is to dig tripoli Other good exposures of Fort In the northeastern Jonesboro Quad- from the Clear Creek Formation. Payne can be found in several areas: rangle, it thickens to 50 to 110 feet. The thin layering of the Fort Payne the bank of Darty Creek in the NW The Fort Payne is 100 to 140 feet is preserved in ganister. Occasional SW, Sec. 11, T12S, R2W; the roadcut thick in the northeastern Mill Creek layers of sticky orange to brown clay along Illinois route 146 in the NE Quadrangle; a few miles farther are present. Ganister grades laterally NE, Sec. 23, T12S, R2W; the stream- east, well records show it to be 300 to unaltered siliceous limestone and bed just south of Kornthal Church or more feet thick. bedded chert. Ganister grades to near the center of the EVi, Sec. 1, limestone along the bluff south of T13S, R2W; and the south bank of Altered lithology The altered Lingle Creek in the SW SW, Sec. 30, the east-flowing stream in the SW Fort Payne Formation is composed T13S, R1W, Mill Creek Quadrangle. SE,Sec. 13,T13S,R2W. of dense, hard, bedded chert and a Ganister grades to bedded chert in Contrary to the findings of Line- granular form of microcrystalline roadcuts along Illinois route 127 just back (1966), the contact with the silica, commonly called ganister. north of Elco, and also near aban- overlying Ullin Limestone is transi- The bedded chert is mottled or doned ganister mines in the hills tional throughout the study area. banded in brownish gray to orange east of Elco. Dark, very siliceous lime mudstone gray. Banding is ropey or resembles

27 FORT PAYNE FORMATION Most of the Ullin is light gray, but medium-dark gray and brownish gray limestone occurs in the lower part. Echinoderm fragments are darker than the matrix and impart a speckled appearance (fig. 18). Ullin limestone is laminated throughout, and parts are distinctly crossbedded. Crossbedding commonly stands out sharply in relief on weathered sur- faces (fig. 19). Most crossbed sets are 1 to 4 feet thick. Fossils other than and bryozoans are un- common; a few brachiopods were noted. The Ullin contains scattered chert nodules; they are light gray, concentrically banded, dull textured, and commonly 6 to 10 inches long and 3 to 4 inches thick. This chert is distinctive in float. In general, the Ullin becomes lighter colored and coarser grained upward. Medium gray or brownish gray, fine grained, faintly speckled limestone transitional to the Fort Payne occurs at the base. This lime- stone is glauconitic and slightly sili- ceous. The limestone becomes medium to coarse-grained upward and contains brownish gray echino- derm clasts in a dull white to very light gray matrix. The middle Ullin lacks glauconite and contains only scattered chert lenses. Near the top the Ullin is very coarse and strongly speckled, and fossil grains are poorly sorted. The Ullin Limestone is readily identified in well cuttings as speck- led, crinoid-bryozoan limestone. On drillers' logs, the Ullin is frequently reported as white or light gray, soft limestone; this is in contrast with the dark gray, hard, and cherry lime- stones of the underlying Fort Payne Figure 17 Isopach map of Fort Payne Formation. Contour interval is 20 feet. and overlying Salem Limestone. The Ullin has uniformly high spontane- Near Hartline Creek in Sec. 18 natural exposures and a quarry face ous potential and uniformly low and 19, T14S, R1W, bedded chert of near Ullin. The limestone that Line- natural gamma readings on geo- the lower Fort Payne forms dark back named Ullin was previously physical logs. scraggly ledges. This is the "Hartline called by such names as Osage, War- Lineback (1966) divided the Ullin into two members: the Ramp Creek chert" of J. Weller and Ekblaw (1940). saw, Warsaw-Salem, Burlington- "Hartline" chert is transitional be- Keokuk, and Harrodsburg. Member below and the Harrods- tween bedded chert and ganister. Lineback's definition of the Ullin burg Member above. He described Light bluish gray vitreous chert and is confusing because he assigned the Ramp Creek as a darker, finer reddish orange porous ganister are some rocks that are typical Fort grained limestone and the Harrods- intricately intergrown. Payne to the Ullin Formation. For burg as a lighter, coarser variety. Lamar previously described example, Locality 1 of the Ullin type (1959) illustrated the Ullin Limestone section (Lineback 1966, p. 37) and same two types The Ullin Limestone was named by includes bedded chert 49.5 feet thick. of limestone in the Jonesboro area Lineback (1966) for the town of We restrict the name Ullin to lime- (under the heading "Warsaw-Salem limestone"). Ullin, which is just east of the study stone that is composed predomi- Lamar's "Mill Creek area. Lineback described a compos- nantly of echinoderm fragments in type" corresponds to Lineback's ite type section consisting of two a matrix of bryozoan fragments. Harrodsburg Member, whereas

28 Lamar's "Kornthal type" matches Lineback's Ramp Creek. As Lamar observed, the two types of limestone intertongue with one another. The best place to see intertonguing of Harrodsburg and Ramp Creek is at the Ullin Quarry of the Columbia Quarry Company. This quarry con- tains part of the Ullin type section. Furthermore, the Ramp Creek lithol- ogy is transitional between the Fort Payne and the Harrodsburg, and intertongues with both. The Harrods- burg and Ramp Creek are better clas- sified as facies than as members. The outcrop belt of the Ullin lies mostly east of the area of altered rocks. A few inliers of Ullin were found near the east margin of the altered area. (They are mapped as Mississippian-Devonian undivided.) Altered Ullin consists of blocks of Figure 18 Crosslaminated Ullin Limestone (Jonesboro Quarry), showing the light gray, banded chert and lime- typical "speckled" appearance of the limestone, which is caused by darker cri- in matrix of plastic clay. Evi- stone a noid fragments in a lighter matrix. Staff is graduated in feet and inches. dently, most of the limestone was dissolved in the altered area. Thickness of the Ullin, as indi- cated by borehole data, ranges from 225 to 490 feet. The Ullin averages 345 feet thick in the wells that have the most reliable logs. The Ullin-Salem contact appears sharp in some exposures, but beds of Ullin lithology occur in the lower Salem, indicating intertonguing. Such interbedding was observed in gullies southeast of Darty Creek, in the center SW NE, Sec. 11, T12S, R2W, and a streambed and roadcut in the SE NE, Sec. 6, T13S, R1W. Sam- ple logs of wells in the Anna Quad- rangle also indicate intertonguing. The top of the Ullin was mapped at the base of the lowest dark lime- stone of Salem lithology. Salem Limestone The Salem Limestone was named by Figure 19 Large-scale planar crossbedding in upper Ullin Limestone at the Cumings (1901) for Salem, Indiana, Columbia Quarry Company's Jonesboro Quarry, just east of the study area in the where the limestone is quarried for SE NE, Sec. 17, T13S, R1VV, Anna Quadrangle. Staff is graduated in feet and inches. building stone. In its type area, the Salem is largely light gray oolitic grainstone that exhibits large-scale whose lithologic characters are more lime mudstone and fine grained crossbedding. In other areas, a wide narrowly constrained. skeletal limestone having few or no variety of limestone lithologies are In this study area, the Salem is a oolites and much chert. assigned to the Salem. For example, unit of medium to dark-colored lime- Two informal units make up the dark gray to black, argillaceous, stone that ranges from lime mud- Salem in the Jonesboro Quadrangle. and dolomitic lime mudstone was stone to grainstone but most com- The lower unit, which makes up one- mapped as Salem in the Fluorspar monly is packstone. Darker color, quarter to one-third of the formation, District (Baxter and Desborough finer texture, presence of oolites, and is interbedded dark micritic lime- 1965, Baxter et al. 1967). The Salem lack of crossbedding distinguish the stone and light skeletal limestone. Limestone seems to be a catch-all for Salem from the Ullin. The overlying The dark limestones are argillaceous strata between the Ullin (or equiva- St. Louis Limestone differs from the to silty, partly dolomitic lime mud- lent) and St. Louis Limestones, Salem in that it is predominantly stones and wackestones. They are

29 very thin or thinly bedded and con- In general, the St. Louis is an inter- based on chert. The most practical tain numerous nodules and discon- val of micritic to fine grained, cherty place for the contact in this area is tinuous layers of light grayish limestone and dolomite. Rocks fit- the lowest occurrence of oolitic lime- brown chert. The light-colored lime- ting this description in the study stone. Because the St. Louis/Ste. stones are fine to coarse grained area are mapped as St. Louis. Genevieve transition is poorly ex- skeletal packstones and grainstones, The most distinctive rock type in posed in the study area, the two for- which are generally poorly sorted the St. Louis is thick bedded, cherty, mations were combined as a single and sparingly oolitic. Fossil frag- dolomitic, micritic lime mudstone unit in the Jonesboro 7.5-Minute ments include echinoderms, brachi- that breaks with conchoidal fracture. Quadrangle (Nelson and Devera opods, and bryozoans. In contrast to This rock type is commonly called 1994). The only place where the con- the Ullin, where darker crinoid frag- "sublithographic." It is typically tact can be located closely is near the ments stand out against a white ma- medium gray or brownish gray on head of Kratzinger Hollow in the trix, fossil grains in the lower Salem fresh surfaces and weathers to NW SE, Sec. 18, T12S, R1W. are generally lighter than the matrix. lighter shades of gray and olive The St. Louis is approximately Light-colored lower Salem limestones gray. Some chert is light gray, but 100 feet thick in Kratzinger Hollow, are relatively pure carbonate contain- most of it is dark bluish gray to the only place where both contacts ing little chert, and bedding ranges nearly black and vitreous; it occurs can be located accurately. Sample from thin to thick. as large lenses and discontinuous logs from five water wells in the city The upper unit of the Salem Lime- bands. Also common are small vugs of Anna indicate the St. Louis to be stone is predominantly medium to and geodes filled with white sparry from 70 to 140 feet thick. The forma- dark gray and brownish gray, fine to calcite and drusy quartz. tion thickens eastward to 250 feet in coarse grained skeletal packstone Alternating with lime mudstone wells in the eastern part of the Anna and wackestone. Fossil fragments are beds of medium to dark gray, 7.5-Minute Quadrangle. A regional are poorly sorted, partly rounded, very finely to finely granular lime- isopach map of the St. Louis in and oolitically coated. Bedding is stone. Some of these beds are skele- southern Illinois shows that the St. generally 1 to 3 feet thick. The upper tal wackestones and packstones Louis thickens eastward to more Salem is at most slightly argillaceous similar to those of the upper Salem, than 500 feet in southeastern Illinois and contains only a few chert nod- whereas other beds are recrystal- (Atherton et al. 1975, p. 141). ules. Whole fossils are rare except lized mudstones that contain few or near the top, where silicified rugose no fossil fragments. Oolites are rare. Ste. Genevieve Limestone corals are common. The diagnostic Fossils include brachiopods, Mas- The Ste. Genevieve Limestone was fossil for the uppermost Salem and toids, crinoids, and rugose corals. named for Ste. Genevieve, Missouri, basal St. Louis is the "finger coral," Acrocyathus proliferus is abundant in by Shumard (1859). This formation Acrocyathus proliferus,which was called the basal St. Louis. generally is recognized as an inter- Lithostrotionella proliferum in many Light gray, fine grained skeletal val that is dominated by light-col- older reports; its present classifica- limestones dominate in the upper ored oolitic and skeletal limestones. tion was established by Sando (1983). part of the St. Louis. Occasional It contains lesser amounts of micritic The Salem-St. Louis contact is silicified colonies of Acrocyathus limestone, shale, and sandstone. gradational and intertonguing. Beds floriformis (found mainly as float) are The outcrop belt of the Ste. of skeletal packstone, typical of the present. Genevieve crosses the northeast cor- Salem, alternate with beds of typical Good outcrops of the St. Louis ner of the Jonesboro 7.5-Minute St. Louis cherty lime mudstone in can be found along the road and Quadrangle. This is an area of gen- the contact zone. Exposures of the stream in Kratzinger Hollow in tly rolling topography and numerous contact are east of State Pond in the small roadcuts and in two small, sinkholes. Outcrops are few and SE SE, Sec. 12, T12S, R2W, and in ra- abandoned limestone quarries north small in the Jonesboro Quadrangle, vines south of Anna in the EVi NE, of the road in the hollow. Outcrops but a nearly complete section can be Sec. 30, T12S, R1W. Intertonguing also can be found near the heads of seen at the active Anna Quarry just and lateral gradation of the Salem several ravines north of Kratzinger east of the study area. Information and St. Louis Limestones previously Hollow. The basal St. Louis is well given here is derived mainly from were documented by Lineback exposed in several small ravines just these quarry exposures and is sup- (1972). In the field, we mapped the south of Anna. plemented by data from nearby out- Salem-St. Louis contact at the low- The contact with the overlying crops, core descriptions, and sample est occurrence of lime mudstone. Ste. Genevieve Limestone is transi- logs of water wells. Thickness of the Salem Lime- tional and arbitrary. Other geologists The Ste. Genevieve contains sev- stone, as determined by well records mapped this contact at (1) the lowest eral types of limestone that are inter- in the Jonesboro and western Anna occurrence of light-colored oolitic bedded. (1) Roughly half the forma- 7.5-Minute Quadrangles, ranges limestone, (2) the highest occurrence tion is white to light gray oolitic and from 285 to 435 feet. of chert, (3) the highest occurrence skeletal grainstone that is typically of "lithostrotionellid" corals, or (4) a crossbedded. This rock occurs in in- St. Louis Limestone combination of the above (Atherton tervals 4 to 20 feet thick and is rela- Englemann (1847) named the St. et al. 1975, Sable and Dever 1990). In tively soft and lacks chert. (2) About Louis Limestone for St. Louis, Mis- the Jonesboro area, cherty lime- a quarter of the formation is light to souri. Concise definitions of the St. stone occurs throughout the Ste. medium gray and brownish gray, Louis Limestone are difficult to find. Genevieve, so the contact cannot be fine grained skeletal grainstone,

30 The Ste. Genevieve is fossilifer- co UJ D ous, although whole fossils are un- DC O FORMATION MEMBER common. Bryozoans, blastoids LU tr CO CD (Pentremites sp.), crinoids (including Yap keetown Ss_? Platycrinites penicillus), brachiopods Ches. CD ^ ^-T-^- Q. O Renault Ls (including Derbyia sp.), syringo- 0. Aux Vases Ss poroid corals, and Chaetetes sp. all were found in the upper Ste. Gene- o 1° °l*o (lo o I vieve at the Anna Quarry. o o • o o o Lenses of shale and sandstone

Ste. Genevieve less than 5 feet (1.5 m) thick occur in o O o o o/ o Limestone I J the upper part of the Ste. Genevieve. A / A Shale is medium greenish gray to o o o o o o nearly black, calcareous, fissile, o o o o o o partly silty, and fossiliferous. Sand-

| greenish gray, A~ A A [ stone is light gray and St. Louis A very fine grained, quartzose, and Limestone 1 g 1 4 I 1 calcareous. Similar shales and sand- stones occur in the lower part of the overlying Pope Group. The Ste. Genevieve intertongues with the overlying Aux Vases Sand- stone (Swann 1963, Nelson and Cole 1992). We mapped the contact at the base of the lowest sandstone unit. Because of the thick loess, we could only approximately locate the con- tact. The Ste. Genevieve is about 250 feet thick in the study area. About 245 feet of Ste. Genevieve is exposed at the Anna Quarry, and the base is concealed. Well records indicate the limestone to be about 220 to 300 feet thick in the northern part of the -100 Anna Quadrangle.

50 Pope Group -200 The Pope Megagroup was named for Pope County in southern Illinois by Swann and Willman (1961). Re- 300 vised to the Pope Group (Nelson 100 1995), the Pope is a lithostratigraphic unit equivalent to what was for- -400 merly called the Chester Group or Series. The name Chester is reserved for chronostratigraphic usage as 150-t-500 Chesterian Series (fig. 20). The Pope Group is largely Chesterian but in- Figure 20 Stratigraphic column showing Mississippian units of the study area. cludes late Valmeyeran rocks at the base (Swann 1963). The group con- packstone, and wackestone. This (4) A minor rock type, observed in tains alternating carbonate and silici- rock is harder than the oolitic lime- the lower part of the Ste. Genevieve clastic rocks. The term Pope Group stone and typically not crossbedded. in the Anna Quarry, is mounded was first used in Weibel et al. (1993). Intervals are generally 2 to 10 feet algal boundstone that contains abun- Rocks of the lower Pope Group thick. (3) Another quarter of the for- dant stromatoporoids and bryozoans. underlie the northeast corner of the mation is medium to dark brownish The four types of limestone occur study area. They do not crop out, gray, slightly dolomitic lime mud- in the Anna Quarry in layers that but they are known from borehole stone that contains as much as 30% pinch and swell. Contacts are grada- records and from nearby outcrops in bluish gray vitreous chert in bands tional in some cases, sharp and the Anna and Cobden Quadrangles. and nodules as thick as 6 inches. undulating in others. The upper Not enough detail is available to This rock closely resembles St. Louis contacts of oolitic units generally are map individual formations in the Limestone. Intervals of lime mud- sharp. Jonesboro Quadrangle. stone are generally 1 to 10 feet thick.

31 At the base of the group is sand- stone presumed to be the Aux Vases. It is light brownish gray to light greenish gray, very fine grained, quartzose, calcareous, and glauconi- tic. The thin, tabular beds display ripple marks, horizontal burrows, and dessication (?) cracks. In well samples, the sandstone commonly contains oolites the size of sand and fossil fragments, and grades to sandy limestone. Interbeds of green to gray and red variegated shale and claystone are present. Overlying the sandstone is an in- terval of limestone containing lesser amounts of shale and sandstone. The limestone ranges from light gray oolitic grainstone to dark gray, argillaceous, and dolomitic lime mudstone. Outcrops of coarse dark purplish gray grainstone and pack- Figure 21 Steeply Cretaceous-Tertiary stone, containing hematitic oolites dipping sand and gravel, SW SW SE, Sec. 11, T13S, R2W, Jonesboro Quadrangle. Bedding strikes and pink, purple, and green echino- N20°E and dips 40°SE. The staff is 5 feet long. derm fragments, occur along the creek in the NW SE NW, Sec. 8, T12S, (Anna Quadrangle). Shale and R1W composed mostly of white to light the Jonesboro Quadrangle. Deposits sandstone are similar to those in the gray, angular to subrounded chert thought to be McNairy include clay, basal Pope Group. Siliciclastic rocks fragments that are as much as 12 silt, sand, gravel, sandstone, con- apparently intertongue and inter- inches in maximum dimension. glomerate, and silcrete. Sand is the grade laterally with limestone. These clasts are mostly dull, porous, most common component. The portion of the Pope Group pitted, and more or less tripolitic, re- The main outcrop area of the within the Jonesboro Quadrangle is sembling unglazed porcelain. Many McNairy is a discontinuous belt less than 100 feet thick and is over- of them are derived locally from the trending south-southeast from the lain by Quaternary loess, alluvium, Clear Creek, Fort Payne, Ullin, and south-central part of the Jonesboro and colluvium. other cherty limestone units. Inter- 7.5-Minute Quadrangle into the Cretaceous System mixed with locally derived chert are northeastern Mill Creek Quadran- smaller amounts of darker, rounded gle. The belt, which varies from lA to Unlithified clay, sand, and gravel, as chert pebbles. The matrix is mostly 1 mile wide, enters the Dongola well as lithified sandstone and con- fine grained tripolitic chert and Quadrangle east of Elco and disap- glomerate, in the crop out Jonesboro some quartz sand. Roadcuts along pears farther south beneath Quater- Quadrangle. These deposits are Illinois route 127 and an abandoned nary alluvium in the Cache Valley. partly Cretaceous and partly Terti- gravel pit in the south-central part Sediment in this belt is largely un- ary age. The strata are poorly ex- of Sec. 7, T14S, R1W, are the best lithified sand, intermixed with mi- posed and differ somewhat from places to see Tuscaloosa-type gravel. nor amounts of clay, silt, and gravel. well known Cretaceous and Tertiary Field notes made when the Elco Scattered outliers of McNairy occur strata that occur southward in the gravel pit was in operation reveal mostly west of the main belt in the Mississippi Embayment. Thus, for- that the gravel was interbedded Mill Creek and southern Jonesboro mational assignments are tentative, with reddish brown sand, well 7.5-Minute Quadrangles. Outliers and Cretaceous Tertiary and depos- rounded chert gravel, and clay con- are composed largely of gravel, con- its are shown as a single unit on the taining scattered pebbles (unpub- glomerate, and lithified sandstone. geologic maps. lished ISGS field notes by J.E. Lamar McNairy sand is brightly colored 1927 and J.C. Frye, H.B. Willman, and variegated in red, orange, ochre, Tuscaloosa Formation (?) and A. Jacobs 1967). purple, and brown. It is mostly fine Named for Tuscaloosa, Alabama, General lithologic similarity is the grained, subrounded to subangular this formation is the oldest Creta- only basis for calling the Elco gravel quartz sand, containing minor or ceous unit known to occur in the Tuscaloosa. Relationships to other trace amounts of lithic fragments, Mississippi Embayment of southern Cretaceous and Tertiary units in the muscovite, and dark minerals in Illinois and adjacent states. Some area are not known. The gravel at a matrix of silt and clay. Coarse gravel in the Jonesboro Quadrangle Elco is at least 50 feet thick. grained sand is uncommon. Suban- is similar to the Tuscaloosa and is gular to well rounded chert pebbles tentatively assigned to that unit. The McNairy Formation The are scattered through the sand and best exposures of Tuscaloosa-type McNairy Formation (Upper Creta- occur as lenses, layers, and stringers gravel are near Elco in the Mill ceous) almost certainly is present in (fig. 21). Some sand grades to sandy Creek Quadrangle. The gravel is

32 silt and clay. Irregularly shaped cal McNairy strata, and therefore is rests mainly on lithologic evidence. pockets, veins, and dikes of light to assigned to the McNairy (Johnson The strata here are similar to un- medium gray clay are common in 1985; Richard Harrison, USGS, per- doubted McNairy strata farther sand and, in some areas, make up sonal communication, 1992). south in Illinois and western Ken- the bulk of the deposit. Much of the McNairy gravel occurs mainly as tucky (Olive 1980, Kolata et al. 1981, sand has no visible bedding or lami- scattered chert pebbles intermixed Trace and Amos 1984). The sand in nation. In areas where layering is vis- with sand. Laminae and beds of the Jonesboro Quadrangle contains ible, it commonly is steeply inclined, gravel, interlayered with sand, are less mica and more gravel than that contorted, and offset by small faults less common. The gravel is com- typical for McNairy. These differ- (fig. 21). posed mainly of off-white to medi- ences might relate to the source area. Some exposures of McNairy sand um gray and brown, rounded to The highly micaceous, gravel-poor are along small east-flowing streams subangular chert pebbles less than McNairy south of the study area in the NE SE and SW SE, Sec. 11, and 4 inches in diameter. Most of the peb- was derived largely from metamor- the SW NE, Sec. 24, T13S, R2W, Jones- bles are dull, more or less tripolitic, phic terranes in the Appalachian boro 7.5-Minute Quadrangle, and and not polished. Float and small Mountains (Pryor 1960). In the Jones- along the small stream that flows outcrops of such gravel are common boro area, however, much of the through the center of Sec. 24, T13S, 1 to 2 miles west of Mill Creek vil- McNairy sediment might have come R2W, Mill Creek Quadrangle. lage, particularly in the SW, Sec. 25, from the north, where the bedrock Silt and clay of the McNairy are and NW, Sec. 36, T13S, R2W. Coarse contains much chert and little mica. various shades of gray. The clay is gravel well cemented by iron oxide typically plastic; silt grades to very was observed in the NE SE, Sec. 35. Tertiary System fine sand. Most silt and clay lack A final rock type assigned to the (?) Chert bedding or lamination. They occur McNairy is a siliceous rock that gravel, sand, and conglomerate that as irregular lenses, blebs, and vein- meets the definition of a silcrete occurs mainly as hilltop outliers is like intrusions in sand. (Summerfield 1983). It crops out tentatively assigned to the Wilcox Well indurated quartz arenite near the top of a hill in the SW SW, Formation (Eocene). Gravel, the occurs in many places in the study Sec. 25, and in thickly vegetated gul- most common lithology, consists of area. This sandstone occurs only as lies trending southward from that subangular to well rounded chert float blocks, the largest of which are hilltop into the NW NW, Sec. 36, granules and pebbles that are as 15 feet in maximum dimension. The T13S, R2W The rock is dull white to much as 6 inches in diameter. The sandstone is white to light gray and light gray, banded, and mottled with pebbles range from light gray to weathers to a smooth, dark gray light red and yellowish brown. It is medium and dark bluish gray to case-hardened surface; it is com- well indurated and resembles "cal- nearly black. They are dull to vitre- posed almost entirely of very fine to ico rock" from the Springville Shale ous and have smooth but not highly fine (rarely medium), well sorted except for the lack of layering. Float- polished surfaces. Well rounded quartz sand. Grains are sub- to well ing grains of well rounded quartz white quartz granules and pebbles rounded (mostly well rounded) and sand and occasional small rounded as much as about V4 inch in diameter frosted. Planar crossbedding in sets chert pebbles are embedded in sil- also are present. Some gravel is inter- 6 to 12 inches thick can be seen in crete. Casts and carbonized impres- mixed with poorly sorted, fine to large blocks of this sandstone. sions of plant material, including coarse sand of quartz and chert Bidirectional or crossbedding was roots and rootlets, indicate that this grains. Most gravel occurs only as observed in sandstone boulders on rock is a silicified paleosol. Silcrete is float along gullies and streams or as hillsides near the Old Cape Road in both overlain and underlain by sand a component of colluvium, inter- the NW SE NE, Sec. 11, T13S, R2W, and gravel. mixed with loess near the tops of Jonesboro 7.5-Minute Quadrangle. Silcrete similar to that found dur- steep ridges. One of the few places Other occurrences include the hill- ing this study occurs in undoubted where more or less uncontaminated top in the SE SE, Sec. 11, T13S, R2W, McNairy strata in the Thebes Quad- gravel can be seen is near the top of and hilltops and gullies northwest rangle to the south. Two samples of a steep east-facing slope near the of Berryville (Jonesboro 7.5-Minute petrified wood from McNairy sand center of the SW, Sec. 1, T14S, R2W, Quadrangle). and gravel in the Jonesboro Quad- Mill Creek Quadrangle.

McNairy quartz arenite can be rangle were identified as similar to Wilcox (?) conglomerate is com- mistaken for the Dutch Creek Sand- Paraphyllanthoxylon illinoisense (Elisa- posed of chert gravel (similar to that stone (Devonian), except that the beth Wheeler, North Carolina State described previously) cemented by McNairy lacks molds and casts of University, Raleigh, written commu- silica (gray) or by iron oxide (dark marine fossils common in the Dutch nication, 1992). This tree is common red, brown, and nearly black). The Creek. Also, some McNairy quartz in the McNairy Formation in the matrix is sand that ranges from pre- arenite contains chert pebbles and Thebes Quadrangle near silcrete ex- dominantly quartz to a mixture of grades to chert-pebble conglomerate posures (Wheeler et al. 1987). How- quartz and chert grains. All grada- Quartz arenite in the study area is ever, Paraphyllanthoxylon is known tions exist—from clast-supported nearly identical to sandstone called from early Tertiary deposits as well conglomerate having little matrix, "Commerce quartzite" after Com- as Cretaceous (Wheeler, written com- through matrix-supported conglom- merce, Missouri (Thebes Quadran- munication, 1992). erate, to sandstone containing scat- gle). Commerce quartz arenite is Identification of the McNairy For- tered chert pebbles. Conglomerate both overlain and underlain by typi- mation in the Jonesboro Quadrangle varies from massive to crudely

33 stratified or, rarely, crossbedded. Nichols, USGS, written communica- were quarried for fill material in the Most conglomerate occurs as cob- tion, 1993). The Eocene lignite came NE, Sec. 29, T12S, R2W, Jonesboro bles and boulders in float but, in a from clay pits (now abandoned) 7.5-Minute Quadrangle. Some of the few places, it forms ledges. Outcrops near the village of Kaolin. Clay at silt in these pits grades to fine grained of conglomerate occur along the Kaolin reportedly overlay deposits sand that was windblown from the south side of the hilltop in the SVi of white to yellow, orange, and red adjacent Mississippi floodplain. NE NE, Sec. 11, T14S, R2W. micaceous sand (McNairy ?) and Most Wilcox (?) outcrops and was interbedded with lignite, grav- Alluvial and lacustrine deposits float in the study area are high on el, and limonite-cemented conglom- Undifferentiated alluvial and lacus- the hillsides west of the south-trend- erate of subangular to rounded chert trine sediments fill all of the major ing belt of McNairy sediments. Wil- pebbles as large as 3 inches in diame- valleys in the study area. These sedi- are cox (?) gravel and conglomerate ter (St. Clair 1917, Parmalee and ments most extensive in the were also found near the northeast Schroyer 1921, Lamar 1948, Nelson Mississippi and Cache Valley flood- corner of the study area in Sec. 1, 2, and Lumm 1985). Gravel that crops plains, where borehole records indi- 11, and 12, T12S, R2W Gravel of the out along ridge tops west of the Kao- cate thicknesses in excess of 100 feet. Deposits along smaller streams in Wilcox type probably occurs within lin clay pits is identical to Wilcox (?) the McNairy belt as well, where it is gravel in the Jonesboro Quadrangle the study area may be quite thick commonly found intermixed with (Nelson and Devera 1994). also, judging by the V-shaped pro- McNairy lithologies in float and in files of most bedrock valleys. slumped, overgrown stream banks. Quaternary System The deposits are composed of Auger borings by the ISGS in the Upland silt and colluvium All poorly sorted and poorly stratified southern part of Sec. 25, T13S, R2W, upland surfaces in the Jonesboro clay, silt, sand, and gravel. Cutbanks along Creek, Creek, recovered Wilcox (?) gravel overly- Quadrangle are mantled with wind- Cany Dutch and ing red McNairy sand along the blown silt (loess) and colluvium other large streams show thick- west edge of the McNairy belt. This composed of rock fragments inter- nesses as great as 40 feet above the limited evidence indicates Wilcox mixed with silt. Silt is typically at present stream level. These deposits are remnants of terraces. In some (?) gravels are younger than the least 10 feet thick on level and gen- McNairy tly sloping ridge crests, and it areas, small streams that enter wide The Wilcox Formation (Eocene) in exceeds 40 feet in bluffs near the valleys are "perched" on terrace rem- the northern Mississippi Embayment Mississippi River. Five cores drilled nants above present-day base level. is composed mainly of sand interca- in upland areas during this study Some cut banks reveal three or more lated with lesser amounts of silt, showed the total thickness of loess distinct layers of gravelly alluvium clay, and gravel. Pebbles in the Wil- to be 15 to 20 feet. The silt is substan- or silt, separated by mottled and cox in the Embayment are predomi- tially thinner on steep hillsides and rooted paleosols. These deposits nantly smaller than 1 inch in diame- absent or intermixed with weath- attest to several stages of alluviation ter. Gravel composed of white to ered rock debris (colluvium) in some and downcutting in drainages near clear quartz pebbles and dark olive areas. At least three distinct loesses the Mississippi. gray to grayish black chert pebbles are present in the study area (Leon Fraser (1980) studied the Pleisto- as large as 2 inches can be found in Follmer, personal communication, cene history of Hutchins Creek in the Thebes Quadrangle (Missouri 1993). These include the following: the adjacent Wolf Lake Quadrangle. and Illinois). This gravel is assigned (1) the Loveland Silt, a reddish Fraser determined that the bottom to the Wilcox (Johnson 1985; Richard orange to reddish gray, well leached of the bedrock channel of the Missis- Harrison, personal communication, clayey silt of Illinoian age; (2) the sippi River is as deep as 200 feet be- valley is 1992). The northern, upland setting Roxana Silt, a brown clayey silt of low present river level. This pre-Illinoian. early episode of of the Jonesboro Quadrangle might early Wisconsinan age; and (3) the An explain the presence of larger peb- Peoria Silt, a yellowish gray to aggradation, followed by downcut- bles in the Wilcox here. brownish gray, slightly clayey silt ting, took place during the Illinoian Palynological evidence further of late Wisconsinan age. Age. Slackwater lakes then formed supports the presence of the Wilcox In some streambank exposures, in tributaries of the Mississippi in Formation in the Jonesboro Quad- large polygonal cracks, lined with early Woodfordian and again in late rangle. Palynomorphs from lignite reddish brown clay, occur in the Woodfordian time. Each episode collected in the Cobden Quadrangle, Loveland Silt. These may represent of lake formation was succeeded north of the study area, are Eocene the C (basal) horizon of the San- by downcutting, as the streams in age (Aureal T Cross, Michigan gamon Soil (Follmer, personal com- reentered their old valleys and State University, East Lansing, per- munication, 1992). Exceptionally reworked the lacustrine deposits. sonal communication, 1984; D.J. thick deposits of Peoria Silt formerly

34 STRUCTURAL GEOLOGY

The Jonesboro 15-Minute Quad- rangle, where the Clear Creek For- and nearly symmetrical. Maximum rangle lies in one of the most struc- mation crops out. Details are scanty dips are about 20° on the west limb turally complex areas in the Mid- due to poor exposure and absence of and 15° on the east limb. The apex of continent. Previous geologists recog- marker beds. the fold is in the SVz, Sec. 16, and the nized the complexity but had diffi- No faults were mapped in this NV4, Sec. 21, T13S, R2W, where the culty portraying it. For example, the homoclinal area, but jointing is prom- Maquoketa Formation comes to the map of J. Weller and Ekblaw (1940) inent in limestone. Primary joints surface. The anticline has at least 350 shows only the Harrison Creek anti- strike north-south to north-north- feet of closure and more than 550 cline and three faults in the quadran- west-south-southeast, parallel to feet of total relief. The lower part of gle. These authors observed (p. 6), the strike of the bedding; secondary the west flank is concealed by allu- however, that "complicated structure joints are perpendicular or nearly vium, and no borehole data are avail- involving folds of considerable mag- so. Primary joints contain fillings of able for that area. The nearest out- nitude and a great number of faults sparry calcite as much as 1 inch crops west of the anticline are in of different types and ages and vari- wide. Some primary joints in the Missouri and at the same or slightly able intensity... are exceedingly dif- Anna Quarry contain sphalerite and higher structural elevation as the ficult to locate and trace because of fluorite, as well as calcite. Secondary west flank of the anticline in Illinois the general lack of readily recogniz- joints generally are unmineralized. (Middendorf 1989). able stratigraphic horizons and the At its southern end, the anticline inadequacy of outcrops." Western Homoclinal Area gradually plunges and dies out into Likewise, our maps cannot do The western homoclinal area is in a gentle east-facing homocline. On justice to the structural complexity the McClure and western Mill Creek the north, the east flank is truncated of the area. Poor exposures, lack of Quadrangles, west of the Delta Fault by the Atwood Fault. The anticline marker beds, and altered strata pre- (fig. 22). Silurian and Lower Devo- and fault pass under the alluvium of vent the tracing of most structures in nian rocks crop out here. The average Dutch Creek and Green Creek and the study area. Enough is exposed, dip in this area is 1° to 2° eastward. then die out. however, to provide an overview of Minor structures include a subtle Like most other large anticlines of the deformation. dome or anticline that brings Silurian the Ozark Dome, the Harrison Creek Structural features of the study strata to the surface near the mouth is an isolated structure, without par- area are grouped as follows (fig. 22). of Dongola Hollow in the McClure allel synclines. It is parallel to several • Eastern homoclinal area Quadrangle. A syncline that trends large nearby faults and is faulted • Western homoclinal area east-northeast was mapped in Sec. 13 along its east limb. A pronounced • Harrison Creek Anticline and 14, T14S, R3W. A few poorly ex- gravity high coincides with the anti- • Major faults posed faults of small displacement cline, implying that basement rocks • "Thumb area" are present. are uplifted (Segar 1965, Nelson and • Altered area Lumm 1985, p. 68-70). These data Harrison Creek Anticline • Post-Cretaceous faulting indicate that the Harrison Creek The largest fold in the study area is Anticline is a drape fold overlying Eastern Homoclinal Area the Harrison Creek Anticline. First a horst in crystalline basement. Gentle, uniform east to northeast mapped by Savage (1920b), the anti- cline Major Faults dips prevail in the eastern homo- was named by J. Weller and for clinal area (fig. 22). The west border Ekblaw (1940) Harrison Creek, Three large faults—the Atwood, of the area parallels Illinois route 127 which cuts across the highest part of Delta, and Cape Road Faults—were fold. and extends from the north edge of the J. Weller and Ekblaw (p. 25) mapped in the Jonesboro Quadran- the study area south to Elco. This stated that the anticline extends gle. All strike north-south to slightly area contains outcrops of Middle north to Bald Knob in the Cobden west of north and have overall dis- Devonian through Chesterian rocks. Quadrangle (about 3 miles north of placement down to the east (fig. 22). On the north, bedding strikes north- our study area), but our mapping Atwood Fault The Atwood Fault northwest and dips northeast at 12° indicates that it ends near Dutch was mapped by Savage (1920b) and or less. Southward the strike gradu- Creek in the Jonesboro 7.5-Minute Weller and Ekblaw ally changes to nearly north-south Quadrangle (fig. 22). J. (1940). The latter named the fault for and dips diminish to less than 5°. The Harrison Creek Anticline has Atwood Ridge. Our of the Eastward homoclinal dips of 2° to a slightly sinuous axis that strikes a mapping Atwood Fault differs little from 5° also occur in the northwest corner little east of north and is about 7 previous mapping. of the Jonesboro 7.5-Minute Quad- miles long. The fold crest is broad

35 anticline Cretaceous and boundary between _JL- mi V fault Tertiary strata altered and unaltered rocks 5 km

Figure 22 Map showing structural features of the study area and distribution of Cretaceous-Tertiary strata. Location of faults in Missouri are taken from Satterfield (1973) and Middendorf (1989).

36 The fault is about 3.5 miles long, strike subparallel. In some places, pieces of Dutch Creek Sandstone, and the north end is concealed by the Delta Fault splits into several and chert nodules and fragments of alluvium. Near its north end, the closely spaced parallel fractures hav- unknown origin. These clasts range fault strikes north-south; to the ing stepwise displacement down to from pebbles to boulders more than south, it curves to N15°W. The fault the east. Steep eastward dips (drag 10 feet in maximum dimension. surface was not observed, but it dips folds) occur within a few feet of the Most clasts are sharply angular, steeply. The east side is downthrown fault surface and in narrow slices although some have rounded corners. along the entire length of the fault. within the fault zone. These observa- Breccia is largely matrix-supported, Displacement probably is greatest in tions indicate that the Delta Fault is but parts are clast-supported. The Sec. 33, T12S, R2W, where upper a high-angle normal fault. megabreccia is faulted against Bailey Formation on the west is Southeast of the Delta Fault in Grand Tower and Clear Creek For- faulted against Clear Creek Forma- Sec. 21 and 22, T13S, R2W, are mations on the west and grades east- tion on the east. Throw here is at several smaller faults that strike ward into less strongly deformed o least 300 feet, and it may be as great N25^i0 W. These faults outline a Mississippian-Devonian strata. as 500 feet. graben in which Grand Tower and The Cape Road Fault splits into The Atwood Fault is a single St. Laurent Formations are down- three branches that outline a lozenge- plane or narrow fracture zone with dropped against Clear Creek Forma- shaped block in the SW, Sec. 14, T13S, little brecciation or drag. Minor tion. One of these faults is exposed R2W. Farther south, two faults ex- faults and joints adjacent to the At- in a silica mine; it is a nearly planar tend south-southwest. The fault wood Fault strike parallel with the normal fault that dips 80° to 85° zone is well exposed along a stream- fault. These observations indicate northeast and has a thin zone of bed in the NE NW SW, Sec. 23, T13S, that the Atwood Fault is a normal breccia. Drag folding adjacent to the R2W, near the north edge of the Mill fault. fault surface is consistent with nor- Creek Quadrangle. The main fault is A smaller parallel fault is about mal displacement. marked by a 10-foot-wide zone of 0.4 mile west of the Atwood Fault in iron-cemented breccia and gouge. give the Sec. 9, T13S, R2W. The smaller fault Cape Road Fault We The breccia zone strikes N20°E and also parallels the axis of the Harri- name Cape Road Fault to the fault dips vertically, separating shattered son Creek Anticline a short distance that extends south from the west chert of the Clear Creek Formation to the west. Maximum displacement part of Sec. 2 to the west edge of on the west from strongly folded of the smaller fault is roughly 300 Sec. 23, T13S, R2W It is named for and faulted shales of the St. Laurent feet, where upper Bailey Formation Old Cape Road (labelled "Plank Hill Formation on the east. Exposures of on the east is downthrown against Road" on the USGS topographic deformed and altered multicolored Bainbridge Formation on the west. map; Old Cape Road is the current shale occur along the streambed as name). Savage (1920b) mapped this far as 1,000 feet east of the main Delta Fault The Delta Fault was fault much as we do, except that he fault. first mapped by J. Weller and Ekblaw showed it extending farther south. Near its southern end, the Cape (1940) and named for the village of The Cape Road Fault does not Road Fault splits into three en eche-

Delta (of which Pleasant Valley appear on the map of J. Weller and lon faults that strike N20°E. These Church is the only extant structure). Ekblaw (1940). dip vertically or nearly so, and some Our map of the fault is similar to The fault is about 4.5 miles long, have wide zones of breccia (fig. 24). that of Weller and Ekblaw, except and its net displacement is down to Faults outline upthrown and down- that we do not extend the fault quite the east. Along most of its length, thrown slices of folded or steeply as far south. the Clear Creek and Grand Tower tilted rocks. In places the sense of The Delta Fault is about 4 miles Formations on the west are juxta- drag and the indicated stratigraphic long and nearly linear, striking posed with undifferentiated Missis- displacement are in opposite direc- N15°W. Along most of the fault, the sippian-Devonian strata on the east. tions (fig. 24). Good exposures of Clear Creek Formation on the west The throw is estimated to be 100 to these faults occur along the east- is faulted against Clear Creek, Grand 200 feet in most places. trending ravines in the NE SE, Sec. 27, Tower, and St. Laurent strata on the The Cape Road Fault differs from and along the south branch of Lingle east. Near the north end of the fault, the Atwood and Delta Faults be- Creek near the farmhouse in the SW the Grassy Knob Chert on the west cause it has much more extensive SW, Sec. 26, T13S, R2W A graben is juxtaposed with the Clear Creek brecciation. A zone of megabreccia about 50 feet wide is at the latter 3 on the east. Throw is probably 100 to as wide as /e mile is on the east side site; contorted and jumbled shale of feet 200 along the middle part of the of the fault for most of its length. the St. Laurent Formation is down- fault; lack of marker beds prevents The best exposures of megabreccia dropped into Dutch Creek Sand- accurate measurement. are along the stream that flows east stone. Breccia zones are as wide as 12 through the center of Sec. 11, T13S, A northeast-facing monocline feet along the Delta Fault. Breccia is R2W, Jonesboro 7.5-Minute Quad- continues farther south in line with composed of angular chert frag- rangle. In this and other areas, large the Cape Road Fault, from the NW, ments cemented by silica and iron and small clasts are chaotically jum- Sec. 35, T13S, R2W, to the west part oxide. fault The surface, observed in bled in a matrix of multicolored, soft of Sec. 19, T14S, R1W. Dips along several places, 60° 80° dips to east plastic clay (fig. 23). Clasts consist of the flank are typically 15° to 25° and and bears nearly vertical silicified mullion and leached Springville locally are steeper. Small faults are and slickensides. Smaller faults and and St. Laurent shale and siltstone, present, but poor exposures obscure joints adjacent to the main fault Fort Payne chert and ganister, a few

37 Figure 23 Megabreccia, composed of blocks of altered Springville Shale and St. Laurent Formation in 3 a soft claylike matrix. This breccia occupies a zone as wide as /a mile on the east side of the Cape Road Fault. Overlying Quaternary alluvium is undeformed. Locality is an east-flowing stream, NW NE SW, Sec. 11, T13S, R2VV, Jonesboro Quadrangle. The staff is 5 feet long.

them. The monocline coincides with tern of faults near the ends of the west, away from the Harrison Creek the southern part of the Cape Road Cape Road Fault is consistent with Anticline. Farther north, several Fault as mapped by Savage (1920b). right-lateral wrench faulting. faults that strike east-northeast out- At its north end, the Cape Road Megabreccias similar to those along line grabens and horsts. Either a Fault passes under alluvium in the the Cape Road Fault occur in the fault or a sharp flexure underlies the NW, Sec. 2, T13S, R2W, Jonesboro Thebes Quadrangle and are inter- northwest-trending valley of Dutch 7.5-Minute Quadrangle. A possible preted as pull-apart grabens along Creek northeast of the thumb. The continuation is exposed in the bank northeast-trending, right-lateral nearly linear, northeast-trending val- of Dutch Creek near the center of faults (Harrison and Schultz 1992). ley of Green Creek (east of the base the NW, Sec. 35, T12S, R2W Several of the thumb) may also contain a faults in this area offset chert of "Thumb Area" fault. Faults under Green Creek may altered Clear Creek Formation. The The name "thumb area" refers to an be offset continuations of faults that largest fault has a breccia zone more upland area, shaped like a thumb in cross the base of the thumb. than 5 feet wide, which is filled with map view. The "thumb area" is Evidently, the thumb area was large, angular blocks of silicified along the Mississippi River bluffs in deformed repeatedly. Thick Grand Springville Shale, St. Laurent Forma- Sec. 20 and 29, T12S, R2W (fig. 22) Tower, New Albany, and Springville tion, and probable Fort Payne. Clasts and has unusual stratigraphy and rocks imply Devonian to early Mis- are as large as several feet across structure. sissippian downwarping. Sub- and float in a matrix of brown plas- Paleozoic rocks in the thumb sequently, these strata were folded tic clay containing laminae of well range from upper Clear Creek For- and faulted. The Harrison Creek rounded quartz sand. The clasts are mation through Springville Shale. Anticline rose, tilting the base of the downdropped a minimum of 200 Outliers of Wilcox (?) gravel cap thumb northwest prior to Eocene (?) feet. Smaller faults in the bank also hills near the "base" (south end) of time. Wilcox (?) gravel was then de- dip vertically or nearly so, and they the thumb. Several units are thicker posited across the beveled edges of contain breccias composed of chert here than in adjacent areas. The dipping Paleozoic rocks. Additional, from the Clear Creek. Springville Shale may exceed 100 later downdrop is indicated by the The brecciation along the Cape feet in the thumb—the thickest fact that Wilcox (?) gravel is absent Road Fault is out of proportion with Springville found in the study area. on nearby higher hills. the modest vertical displacements. The New Albany Shale appears to Breccias are composed of younger be about 80 feet thick, whereas it is Altered Area rocks that dropped several hundred absent in outcrops east of the thumb. The altered area is a region where all feet downward but underwent little The limestone member of the Grand Paleozoic rocks are leached of carbon- grinding or crushing, implying that Tower Limestone is well developed ate and silicified. It contains impor- they collapsed into wide open fis- in the thumb but thin or absent in ex- tant commercial silica deposits. The sures. Such fissures can develop posures to the south and east. altered area is structurally distinct under divergent wrench faulting Structurally, the thumb is down- from surrounding areas, and tecton- (Wilcox et al. 1973, Woodcock and dropped. At the base of the thumb, ics evidently played a role in alter- Fischer 1986). The en echelon pat- Paleozoic strata dip 10° to 15° north- ing the rocks.

38 — w St. Laurent Fm •vT^1 %^HI£nLFmC(earCreek X V • Sl'-r.-^ — 'A v> X ** -X 1 X X X v iCIear dreek Frrv X X ?^A X rr, X C'cTear X Dutch Ck X Creek Ix X 100 ft * breccia and ^ 1 >! - gorge zone \ 25 m

Figure 24 Profile of fault zone along an east-trending ravine in the SE NE SE, Sec. 27, T13S, R2W. Faults strike about N20°E and outline a graben. On the easternmost fault, the "drag" is opposite to the stratigraphic offset, indicating that this fault either underwent a reversal of the direction of throw, or has a component of strike-slip.

Extent The altered area covers Tower Limestone, a relatively pure vertical. Most fault surfaces are pla- most of the Mill Creek Quadrangle, limestone, was largely dissolved; nar to slightly sinuous in dip direc- the southern part of the Jonesboro whereas, the Dutch Creek Sandstone tion. A few surfaces are strongly 7.5-Minute Quadrangle, and part of Member was brecciated. Argilla- curved, typically steepening down- the McClure Quadrangle. A small ceous limestones and calcareous ward. A few subhorizontal faults inlier of unaltered rocks occurs near shales of the St. Laurent Formation (parallel to bedding) were observed. Lingle Creek in the SW, Sec. 26, T13S, were altered to calico-colored, Some of them offset steeply dipping R2W. The border of the altered area slabby, siliceous rock and brown, faults. is marked on the geologic maps punky rock interbedded with chert. Displacements are difficult to (Devera et al. 1994, Nelson and The Springville Shale was silicified determine due to the small size of Devera 1994). and stained in calico colors. The Fort exposures and the scarcity of marker Lateral boundaries of the altered Payne was changed to bedded chert beds. In most places where throw area are well defined in some places, and ganister, and the Ullin Lime- could be measured, displacement diffuse in others. The east boundary stone was largely dissolved, leaving was less than 10 feet. Larger faults is fairly sharp; for example, on the residual chert nodules and reddish having 10 to 100 feet of throw occur south side of Lingle Creek (Sec. 30, brown clay. mostly in the Mill Creek Quadran- T13S, R1W), unaltered Fort Payne gle. Most of these are mappable only limestone changes to ganister in less Faults The altered area has a much because Dutch Creek Sandstone or than 100 feet. The west boundary in greater density of faults than does St. Laurent strata serve as marker the Mill Creek Quadrangle is highly the surrounding region. Hundreds beds. A fault having more than 100 irregular. Certain layers (presum- of faults, mostly too small to map, feet of displacement could easily go ably more permeable strata) in the were observed. Given the density of undetected in the uniform chert of Grassy Knob Formation seem to faults seen in good exposures such the Clear Creek Formation. have been altered selectively while as silica mines, thousands more Most faults in the altered area overlying and underlying beds were probably are concealed by loess, lack slickensides. Where present, unaffected. alluvium, soil, and vegetation. Few slickensides and mullion are com- The extent of alteration at depth exposures longer than 50 feet lack monly horizontal or nearly so. In a is little known. The deepest test faults. few places, the direction of horizon- holes are about 400 feet deep, and In the Jonesboro 7.5-Minute tal (strike-slip) displacement may be most lack accurate and detailed logs. Quadrangle and in northern parts of deduced. Two faults northwest of Available records indicate alteration the Mill Creek Quadrangle, most Dago Hill in the SW, Sec. 3, T14S, extends at least 400 feet downward faults strike north-south or nearly R2W, Mill Creek Quadrangle, strike in most of the altered area. Silica so; they are subparallel to the At- west-northwest and have horizontal miners confirm that underground wood, Delta, and Cape Road Faults. slickensides. The "smoothness test" rripoli deposits extend several hun- In the southern part of the Mill on the slickensides, combined with dred feet below the surface. Creek Quadrangle, the principal the orientation of pinnate fractures fault trend is N30^0°E; north-south along the faults, indicate left-lateral Nature of alteration Detailed faults are uncommon. Linear north- displacement. A fault in the NW descriptions of the lithologies of east-trending topographic features SE NE, Sec. 4, T14S, R2W, strikes altered units are in the Stratigraphy such as Sexton Creek, Sandy Creek, N40°W, dips 84° NE, and has stria- section. Briefly, all carbonate miner- Branch, the Valley Jim and Cache tions that plunge 70° SE, indicating als were removed, and silica was bluff at Tatumville be fault- may left-lateral oblique slip. concentrated. Altered rocks are controlled. East of the Delta Fault, Several upthrust faults or positive either bleached or blotched and several smaller faults strike north- flower structures (Harding 1985) banded in a variety of bright colors northwest. Faults that strike east- were observed. A good example of (calico rock). The Bailey, Grassy west to about N60°W occur through- a positive flower structure was ex- Knob, and Clear Creek Formations, out the altered area but are less com- posed on the highwall of the Lone which originally were cherty and sili- mon than other trends. Star Cement Company's silica ceous limestones, are altered to bed- Nearly all faults in the altered area quarry (NW, Sec. 15, T14S, R2W). ded chert and rripoli. The Grand dip steeper than 60°, and many are

39 Several curving high-angle reverse faults steepen downward and con-

verge to a single vertical fault (fig. 25). Another flower structure was ob- served in the bank of Lingle Creek (NW NE, Sec. 26, T13S, R2W). A small reverse fault and a small, tight -£^Lr^*- reverse kink fold both strike N80- 85°E and dip steeply north (fig. 26). Other compressional structures in- clude a monoclinal kink fold near the portal of an abandoned silica mine (SE NW NW, Sec. 14, T14S, R2W). The axial plane of the kink fold trends N70°W/70°SW. Nearly all of the reverse faults in the altered area dip at least 60°. What may be a large positive flower structure was mapped in the NE, Sec. 33, and an adjacent part of Sec. 34, T13S, R2W. A narrow block of Bailey Limestone and Bainbridge Formation is faulted against Bailey and Grassy Knob on both sides. Bor- dering faults strike west-northwest, parallel to nearby faults that have horizontal slickensides. Pull-apart structures, or negative flower structures, may be more com- mon than positive flower structures. Many fault zones in the altered area are filled with coarse breccia of angu- lar chert fragments and, less com- monly, Cretaceous-Tertiary gravel (fig. 27). Some faults that have only a few inches or feet of vertical sepa- ration contain breccia zones several feet wide. For example, a northeast- trending fault at the head of Sexton Creek (near the SE corner, Sec. 4, Figure 25 Faults on the north-facing wall of Lone Star Cement Company's T14S, R2W, Mill Creek Quadrangle) open-pit silica mine in the NE NW, Sec. 15, T14S, R2W, Mill Creek Quadrangle. has a breccia zone 30 feet wide but On the east (left) is a positive flower structure composed of several upthrust faults that and combine into a single vertical fault. that no detectable vertical offset. Breccia steepen downward Note the beds do not match on opposite sides of this structure. The hard brown chert zones occurring along vertical faults layer "A" traces across with little vertical offset, but chert layer "B" is not present typically are funnel-shaped, narrow- east of the fault. This is further evidence for strike-slip displacement. The nearly ing downward. Breccias also occur vertical fault west of the flower structure has a sinuous fault surface, indicative at the crests of small chevron anti- of strike-slip. The rock is altered Clear Creek Formation (interbedded chert and clines (fig. 28). J. Weller (1940, un- tripoli). The strike trend of faults could not be determined. The staff is 5 feet long. published field notes, ISGS open files) reported vertical fractures filled with gravel (Tuscaloosa?) in dropped against Dutch Creek Sand- side. For example, in the Lone Star the roof of a ganister mine (now stone. Clasts are as much as several Cement Company's silica mine, two abandoned) northeast of Elco in the feet across, and some are internally normal faults and one reverse fault NE NE NW, Sec. 18, T14S, R1W. deformed (fig. 29). Bedding of Dutch all strike N40-45°E. Normal and re- A large pull-apart structure is pres- Creek Sandstone west of the fault verse faults strike both north-south ent in You-Be-Damned Hollow in zone and St. Laurent Formation east and east-west at the Jason no. 2 the SW NW, Sec. 35, T13S, R2W. The of the zone both dip gently east. open-pit silica mine in the SE, Sec. 22, fault zone, which appears to strike Springville clasts in the breccia are T13S, R2W. Moreover, drag along north-south, contains a megabreccia downdropped at least 100 feet rela- many faults indicates movement zone nearly 100 feet wide. Blocks tive to adjacent strata. This breccia is opposite to the observed stratigraphic and fragments of limestone, silt- similar to that found along the Cape (vertical) displacement. Bedding on stone, and shale from the Devonian Road Fault. both sides of a fault may be folded St. Laurent Formation and Mississip- Normal and reverse faults com- in the same direction (upward or pian Springville Shale are down- monly occur parallel and side-by- downward), or bedding may be

40 nearly horizontal on one side of a fault and steeply tilted on the other (fig- 30).

Folds Folds in the altered area are predominantly brittle. Most folds are chevron or hinge-shaped (fig. 28). Flanking dips greater than 30° are uncommon except adjacent to faults. Small monoclines, anticlines, and synclines have vertical or steeply dipping axial planes, along which rocks are intensively fractured. Such folds pass laterally or vertically into faults of small displacement. Distin- Figure 26 Sketch of fault and kink fold exposed in guishing sharp hinge-like folds from the bank of the creek, 300 feet from the north line, 2,000 faults can be difficult when there are feet from the east line, Sec. 26, T13S, R2W. Both the reverse fault and the axial no marker beds (as is usually the plane of the kink fold strike N80-85°W and dip steeply north. These structures case). are more likely products of strike-slip faulting than of horizontal compression. Small arcuate folds and kink NW folds are associated with flower struc- tures. Most such folds trend east- west to east-southeast-west-north- west. These folds are closely associ- ated with faults. They may be fault- propagation folds. Bedding of the Clear Creek For- mation in the altered area gently undulates in seemingly random manner (fig. 6). Undulations may be partly tectonic structures and partly products of uneven settling during alteration.

Joints and clastic dikes Joint- ing is pervasive in all hard rocks of the altered area. Only soft tripoli and claylike shales do not display joints. Most large outcrops display two to four sets of joints. North- south joints are abundant and closely spaced throughout the altered area. Joints that trend north- northeast are abundant in some areas and uncommon in others. East-west joints occur throughout the altered area but rarely are closer than 1 foot apart. Joints that trend west-northwest are common, but they are widely spaced also. Thus, the trends and abundances of joints are closely similar to those of faults in the altered area. Narrow veins and dikes filled with clay, silt, sand, gravel, and chert fragments are widespread in the altered area. Trends vary, but many strike east-west to west-north- west-east-southeast and are vertical Figure 27 Sketch of a fault in the southwest bank of Johnson Creek, just east of or nearly so. clastic are the NW corner, Sec. 24, T14S, R2W. Fault strikes north-northeast and dips verti- Most dikes slightly sinuous in strike cally; chert and tripoli of Clear Creek Formation apparently are downthrown to and dip. the southeast. The fault zone is filled with a loose breccia of angular chert frag- Clay-filled veins and dikes are most ments intermixed with silt and clay, some of which is laminated, indicating deposi- common in the Clear Creek Forma- tion by water in large open crevices. The sinuous fault surface, wide breccia zone, tion but occur in other units, includ- and inconsistent "drag" folds indicate a component of strike-slip. ing Cretaceous-Tertiary sands and

41 gravels. Most dikes are only a few inches wide, but a few are as wide as 2 feet (fig. 31). Near the Delta Fault, dikes are numerous and strike west-southwest and north-north- west, normal and parallel to the fault. Altered Clear Creek Formation contains both vertical dikes and hori- zontal or inclined veins filled with sediment. The filling is light gray to light greenish gray plastic clay, mot- tled in pale pink and violet. Some veins also contain light gray silt and chert sand, as well as occasional large angular fragments of chert. Some vein-filling sediment is lami- nated (fig. 27), indicating deposition by water in open cavities. Some sedi- ment-filled veins and fissures are associated with faults (fig. 27), but most are not. Figure 28 Anticline in the Springville Shale, SE NE NE, Sec. 11, T13S, R2W, Causes of alteration Several pre- Jonesboro Quadrangle. The axial plane strikes about N30°E and dips steeply. At vious authors published theories on the crest of the fold, just left of the staff, fissures and angular rotated blocks of silirified shale indicate pull apart. staff is feet the causes of alteration. J. Weller The 5 long. (1944) suggested deep weathering and leaching beneath a Tertiary peneplain. Lamar (1953) concurred with Weller that the rocks were altered by groundwater close to the surface. Both Weller and Lamar thought that much of the complex structure in the altered area resulted from dissolution and collapse. Berg and Masters (1994) propose that the silica deposits are of hydrothermal origin. Their conclusion is based partly on similarity of southern Illi- nois silica to other deposits of known hydrothermal origin. Berg and Masters also note that large gravity and magnetic highs coincide with altered areas, implying the pres- ence of mafic plutons that served as heat sources. The deep-weathering hypothesis of Weller and Lamar fails to account for the fact that altered rocks extend at least 400 feet below the surface in Figure 29 Tight chevron fold in shale siltstone of the St. Laurent some areas, whereas unaltered rocks and Forma- tion in You-Be-Damned Hollow, SE NW, Sec. 35, TBS, R2W, Mill Creek crop out nearby. Deep weathering SW Quadrangle. Siltstone just east (right) of fold is horizontal. This exposure is part also does not explain silicification of of a megabreccia that contains clasts of St. Laurent and Springville Shale. The noncalcareous rocks, such as the staff is 5 feet long. Springville Shale. Weathering may have played a role in altering some rocks. Outcrops of Clear Creek lime- but the usual products are terra rosa gravity anomalies, provided heat stone commonly have tripolitic and karst topography. and perhaps acidic fluids that dis- rinds, and Fort Payne outcrops have We favor hydrothermal alteration, solved carbonate and precipitated rinds of ganister. These surficial as proposed by Berg and Masters silica. Certain layers, more permeable rinds are generally a few inches (1994). Hydrothermal activity would or chemically susceptible, were selec- thick at most. Limestone undergoes affect all lithologies and extend to tively affected. extensive dissolution in the subsur- depth, as is observed. Deep-seated Mineralization in and near the face throughout southern Illinois, plutons, indicated by magnetic/ altered area lends additional support

42 to the hydrothermal theory. Limo- nite, goethite, and botryoidal manga- nese oxides are common in the altered area, particularly along faults. The characteristic rose and magenta shades of calico rock are probably due to manganese. Iron and manganese oxides are common in low-temperature hydrothermal deposits, although they also occur in non-hydrothermal settings. Fluorite occurs in veins and cavities in the Ste. Genevieve Limestone at the Anna Quarry, a short distance north --••>"* of the altered area. Cuttings from the Humble Oil Company no. 1 Pickel well, drilled just west of the altered area, contained unusually high con- centrations of silver, arsenic, lead, molybdenum, and copper. Total me- tallic content of samples from the

r.* Pickel well was the highest among 29 wells sampled around the west- Figure 30 Fault in the Springville Shale, SW SE SE, Sec. 11, T13S, R2W, Jones- ern and southern margins of Illinois boro Quadrangle, strikes N20°E and the west (left) side is downthrown. Note the (Erickson et al. 1987). steep dip of the downthrown block contrasting with near-horizontal shale in the Our mapping reveals that bed- upthrown block. rock is intensively faulted and frac- tured throughout the altered area. Faults and joints trend in several directions, forming an intersecting gridwork. The density of faults in the altered area contrasts with the virtual absence of faults in the bor- dering eastern and western homo- clinal areas. Faults and fractures provide pathways for hydrothermal fluids. In particular, open fissures and pull-apart structures, common throughout the altered area, are highly permeable. Some of the most intensive silicification (e.g., near Elco and in the central Mill Creek Quad- rangle) occurs along mapped faults. Clastic dikes may be extensional or transtensional fissures that were filled with sediment carried by circu- lating fluid. In conclusion, low-temperature hydrothermal action was the pri- mary cause of altered rock in the study area. Deep-seated plutons sup- plied the heat. The fluids may have come from the plutons or from groundwater, circulated by convec- tion. Intersecting sets of closely spaced, extensional and transten- sional faults and fractures provided pathways for the hot water. An am- ple supply of fine grained biogenic and detrital silica lay in the Bailey, Grassy Knob, Clear Creek, Fort

Figure 31 Fissure (2 ft wide) in Clear Creek Formation Payne, and other formations. Acidic is filled with breccia of angular chert clasts and strikes hydrothermal fluids removed car- N38°E. It is located just west of the Delta Fault. bonate minerals and replaced them

43 Figure 32 Fault zone in south bank of Cooper Creek, 2,100 feet from the north line, 2,400 feet from the east line, Sec. 1, T14S, R2W, Mill Creek Quadrangle. High-angle reverse and normal faults strike approximately N20°W and displace Mississippian rocks against Cretaceous-Tertiary sand and gravel. The wide deformed zone and inconsistent direction of "drag" indicate a large component of strike-slip movement.

with silica. Units like the Clear displacement, which indicates a side downthrown. This is geometri- Creek, originally very siliciceous, component of strike-slip displace- cally a reverse fault. The other fault may have undergone little loss in ment. strikes N75°W and dips 75°N, with volume (although data on this sub- Another fault that offsets Creta- the north side downthrown (a nor- ject are lacking). Relatively pure car- ceous or Eocene strata against Paleo- mal fault). The normal fault appears bonate units, such as the Grand zoic rock is exposed along the east- to terminate against the reverse Tower Limestone, were largely dis- flowing stream about 700 feet from fault. Both faults have dip-slip dis- solved away, allowing overlying the south line and 300 feet from the placements of at least 10 feet. No rocks to collapse and fracture further. west line of Sec. 13, T13S, R2W, drag, mineralization, or slickensides Jonesboro 7.5-Minute Quadrangle. are present; only a thin layer of clay Post-Cretaceous Faulting The fault surface is obscure, but Cre- and sand gouge occurs along the

Tectonic faults that displace Creta- taceous (or Eocene) sand and gravel steeply dipping fault surfaces (fig. 33). ceous and Eocene sediments were dip steeply west and butt against Field notes made by J. Weller observed during this study. The ex- Springville Shale. The shale is highly (1940, ISGS files) while the ganister tent and nature of post-Cretaceous fractured and bears a drag fold that mine was active describe vertical fis- faulting is difficult to assess because indicates displacement down to the sures or veins filled with gravel in of the poor exposures and lack of west, a finding that would be consis- the interior of the mine. Weller did stratigraphic control. Exposures of tent with stratigraphic offset. This not mention the orientation of the faulted Cretaceous strata are small, fault forms the east side of a narrow fissures. required digging to reveal that and most graben trends north-south or Tuscaloosa (?) gravel probably details. Evidence indicates, however, slightly west of north. The west side was faulted in the Elco gravel pit that post-Cretaceous tectonic activ- of the graben is covered by slumped (now mostly backfilled) near the cen- ity was widespread and significant. material. A cross fault strikes N65°W ter of the north line of Sec. 18, T14S,

The main belt of Cretaceous and and displaces Springville and Fort R1E. Light gray chert gravel is still Eocene (?) outcrops parallels major Payne strata a short distance east of exposed in the pit and nearby road- faults and may be tectonically con- the graben. Abrupt elevation cuts along Rt. 127. Notes and a trolled. changes of the McNairy on opposite sketch from the pit by J.E. Lamar The best fault exposure is in the sides of the cross fault indicate that (1927, ISGS files) show gravel in a south bank of Cooper Creek 2,100 it also is displaced. deep rectangular depression, feet from the north line and 2,400 Tuscaloosa (?) gravel is faulted bounded by nearly vertical walls of feet from the east line, Sec. 1, T14S, against Paleozoic rocks near Elco. At Paleozoic bedded chert. The walls R2W, Mill Creek Quadrangle. The the portal of an abandoned under- of the pit ran north-south and fault zone strikes about N20°W, dips ground ganister mine, 800 feet from east-west. Lamar also depicted a steeply west, and juxtaposes Creta- the north line and 3,300 feet from north-south fissure, filled with clay ceous or Eocene (?) sand and gravel the west line, Sec. 18, T14S, R1E, two containing angular chert fragments on the east against Fort Payne chert faults displace light gray chert and intruded into sand and gravel and Springville Shale on the west gravel against ganister of the Fort on the pit floor. Although Lamar did (fig. 32). Drag folding is not consis- Payne Formation. One fault strikes not call these features faults, his tent with the observed stratigraphic N5°W and dips 75°W, with the east description implies they are faults.

44 Moreover, they are nearly parallel to faulted block, is exposed along a the faults at the abandoned ganister small south-flowing stream north of mine described above. You-Be-Damned Hollow in the NE Steeply dipping and faulted Cre- of Sec. 35, T13S, R2W, Mill Creek taceous or Eocene sand and gravel Quadrangle. The inlier is sur- crop out along a small stream in the rounded by tilted and faulted Missis- SW SW SE, Sec. 11, T13S, R2W, Jones- sippian rocks. Bedding of the sand boro Quadrangle. These sediments and gravel strikes approximately are folded into a monocline that east-west and dips 25°S. Exposures strikes N20°E and dips as steeply as of Springville Shale and Fort Payne 40°SE (fig. 21). Nearby, a small fault Formation occur immediately north displaces the gravel; it strikes of the dipping sand and gravel. north-south, and the west side is They are offset by a fault that trends downthrown (fig. 34). The fault and N80°E and dips 70°S. A short dis- monocline trend parallel to nearby tance south of the gravel inlier, faults in Paleozoic bedrock. Springville Shale dips 15°N. South- Deformed outcrops of McNairy ward, along the bed of the main and Wilcox (?) sand, clay, and gravel stream in You-Be-Damned Hollow, occur along an east-trending ravine Springville Shale is strongly jointed. in the NE SE, Sec. 11, T13S, R2W. Primary joints strike N5°W, secon- The McNairy is brightly colored dary joints east-west; bedding dips sand containing stringers and layers variably, as steeply as 20°E or 20°W. of chert gravel and lenses of gray Cretaceous and/or Tertiary sand silty clay. Elisabeth Wheeler (North and gravel occur in pull-apart brec- I Carolina State University, Raleigh, cia zones along faults in the altered written communication, 1992) identi- area. An example visible from a Figure 33 Fault at the portal of an fied a piece of petrified wood from county road is in a high cut bank of abandoned ganister mine near Elco, 800 this exposure as typical of McNairy Lingle Creek in the NE, Sec. 26, feet from the north line, 3,300 feet from NW . Light to dark gray, well T13S, R2W, Mill Creek Quadrangle. the west line, Sec. 18, T14S, R1W, Mill Creek Quadrangle. Cretaceous-Tertiary rounded chert gravel in the ravine is Structural control of the south- gravel on the north (right) is in fault tentatively identified as Wilcox. trending belt of Cretaceous-Tertiary contact with bleached ganister derived Steeply dipping and contorted layer- strata in the eastern part of the study from the Mississippian Fort Payne For- ing, as well as small normal faults area is indicated by the fact that the mation. The fault trends N75°W, dips were observed in McNairy and Wil- belt parallels the Atwood, Delta, and 75°N and is normal. A fissure (perhaps cox (?) sediments along this drainage. Cape Road Faults and the Harrison caused by subsidence of the mine open- A small inlier of McNairy sand Creek Anticline (fig. 22). Most faults ing) has developed along the clay-lined and gravel, probably in a down- that displace Cretaceous-Tertiary fault surface. The staff is 5 feet long. materials in this belt run north- south. Just north of the study area (in the Cobden Quadrangle), the west edge of the belt is a fault that juxtaposes Cretaceous and Eocene sediments with Paleozoic bedrock (Devera and Nelson 1995). No tectonic deformation of Qua- ternary sediments was detected. Sev- eral post-Cretaceous faults described previously are overlain by unde- formed Quaternary loess and allu- vium. Undisturbed sediments also overlie many expo- sures of faults that displace Paleo- zoic rocks. An especially instructive exposure is in a high cutbank of the east-flowing creek 2,300 feet from the south line and 1,700 feet from the west line of Sec. 17, T11S, R2W, Jonesboro 7.5-Minute Quadrangle. At this site, about 30 feet of subhori- zontal, unfaulted Pleistocene sedi- ments overlie Paleozoic megabreccia Figure 34 Small fault displacing Cretaceous-Tertiary sand and gravel, SW SW near the Cape Road Fault. The Pleis- SE, Sec. 11, T13S, R2W, Jonesboro Quadrangle. The fault strikes north-south and tocene strata include Peoria, Rox- the west (right) side is downthrown. The amount of displacement is unknown ana, and Loveland Silts overlying but probably small. Overlying Quaternary alluvium is not displaced.

45 two distinct layers of pre-Loveland oped principally in the late Missis- mal event is related to Late Creta- alluvium (Leon R. Follmer, personal sippian and Pennsylvanian Periods, ceous-early Tertiary igneous activity communication, 1993). with additional post-Pennsylvanian in the Mississippi Embayment. The To summarize, faults that dis- uplift (Kolata and Nelson 1991). inferred pluton in the Jonesboro place Cretaceous-Tertiary sediments The Atwood and Delta Faults are Quadrangle is in line with a series of in the Mill Creek and Jonesboro post-Devonian, high-angle normal known and inferred mafic plutons Quadrangles strike approximately faults. Northeast of the study area, along the west edge of the Embay- north-south and east-west, and similar normal faults strike north- ment in Arkansas and Missouri. All they dip steeply, nearly vertical in northwest in the Makanda (Jacobson of these plutons exhibit high gravity most cases. Vertical displacements and Weibel 1993) and Bloomfield and magnetic values (Hildenbrand probably range from a few tens of (Nelson 1993) Quadrangles. These 1984). The Little Rock (Arkansas) feet to 100 feet or more. Some faults, faults displace rocks as young as pluton crops out and is composed of particularly the north-south ones, Morrowan (Lower Pennsylvanian) nepheline syenite of probably have large components of and presumably are products of hori- age (Moody 1949). Northeast of the strike-slip displacement. No evi- zontal extension. Little Rock pluton is the Newport dence of Quaternary tectonic activ- The Cape Road Fault parallels the pluton, interpreted to be Upper ity was discovered. Atwood and Delta Faults but exhib- Cretaceous or . Associated its extensive brecciation and fracture with the Newport pluton are manga- Summary patterns that indicate dextral strike- nese deposits and silicified Paleo- The Jonesboro Quadrangle clearly slip. No other large fault in the area cene limestone (Glick 1982). has a complex tectonic history, and has similar features. Small, parallel Many faults in the altered area the order of events and their role in faults east of the Cape Road displace probably are strike-slip. Some are regional geology remain unclear. Cretaceous and Eocene (?) strata. compressional, but transtensional Mapping in adjacent areas may fur- Possibly, the Cape Road Fault origi- faults that produced pull-apart struc- ther clarify the relationships. nated as a normal fault, along with tures are more common. The domi- Gentle eastward dips in the east- the Atwood and Delta Faults, and nant trends are north-south, east- ern and western homoclinal areas later was reactivated under a differ- west, and northeast-southwest. In reflect subsidence of the Illinois ent stress field as a strike-slip fault. the adjacent Thebes Quadrangle Basin relative to the Ozark Dome. Altered (leached and silicified) many northeast-striking faults This subsidence took place during rocks in the study area are shattered exhibit right-lateral strike-slip and and after the Paleozoic Era. by three or four intersecting sets of outline pull-apart structures. Units The Harrison Creek Anticline is faults and joints. This fracture sys- as young as the Mounds Gravel similar in trend and geometry to the tem provided pathways for hy- (Pliocene ?) are displaced in the Du Quoin Monocline and the Salem drothermal fluids that were heated Thebes Quadrangle (Harrison and and Louden Anticlines farther north by deep-seated plutons. The nearest Schultz 1992, Nelson and Harrison in Illinois. Like them, it probably outcropping igneous rocks, in the 1993). Major northwest-trending overlies faults in crystalline base- Fluorspar District to the east, are faults on the Ozark Dome were inter- ment (Nelson 1991). The Du Quoin, Early (Zartman et al. 1967). preted as left-lateral transfer faults Salem, and Louden structures devel- More likely, the Jonesboro hydrother- by Clendenin et al. (1989).

46 GEOLOGIC HISTORY

In this section, we interpret deposi- Silurian Folk 1977). We tentatively favor rela- tional and tectonic events in the Silurian depositional conditions in tively deep water (below wave base, study area. A comprehensive treat- southwestern Illinois are poorly and deeper than either Bailey or ment is not attempted; emphasis is defined and have received little Clear Creek) for the Grassy Knob. given to new findings on Devonian, attention in the literature. According Evidence includes the sparse fauna Mississippian, and Cretaceous- to Whitaker (1988), the study area and presence of horizontal burrows Tertiary sedimentation and tectonic lay on a shallow, east-sloping ramp rather than vertical (escape) burrows. activity. between land on the Ozark Dome The Clear Creek Formation was and deeper water in the southern deposited as primary carbonate mud Ordovician part of the Illinois Basin. The region with a large dose of biogenic silica Pre-Maquoketa strata will not be dis- seems to have been stable techni- from sponges and radiolaria (Allen cussed here because information is cally, and sedimentation proceeded 1985). Common fossils and vertical limited. For a regional review, see under low energy conditions. There (escape) burrows indicate fairly Kolata and Noger (1991). is little evidence relevant to esti- rapid sedimentation albeit under A rapid marine transgression mating water depth. low energy conditions. Water depth began the deposition of the Maquo- Beginning in mid-Niagaran probably diminished toward the end keta; the Cape La Croix Member was (Moccasin Springs) time, increasing of Clear Creek time. Upward, brachio- deposited in relatively deep water. amounts of fine terrigenous elastics pods become more numerous, and Gradual shoaling is reflected in the were deposited in the study area. terrigenous silt and fine sand came upward increasing silt content, Although the source of these elastics in possibly from the Ozark Dome. A gradational to the Thebes Sandstone is not known, they are widespread major drop in sea level near the end Member. Part of the Ozark Dome in in southeastern Missouri and south- of Early Devonian time resulted in southeast Missouri was exposed ern Illinois. Sedimentation appar- widespread on the subaerially and supplied sediment ently continued without a break into flanks of the dome. to the Thebes Member. During depo- the Bailey Limestone and across the The eastern Ozark Dome was sition of the Thebes, the sea gradu- Silurian-Devonian boundary. uplifted recurrently from Middle ally became shallower; finally, the Devonian on into Mississippian sea floor was exposed in the tidal Devonian time; this strongly influenced thick- flats represented by the red and Terrigenous clastic input waned as ness and facies patterns in the study green mudstone at the top of the Bailey deposition proceeded, but area. Although direct evidence is Thebes. sponges and other organisms pro- lacking, basement faults may have The Orchard Creek-Girardeau duced large amounts of silica. The been reactivated during this time represents another sequence of fine grain size and thin, even layer- period. The "thumb area" in the rapid transgression (dark clay ing of the Bailey imply low energy western Jonesboro 7.5-Minute Quad- shales) followed by gradual shoaling but not necessary deep water sedi- rangle remained persistently low (increasing limestone content up- mentation. Banaee (1981), however, while adjacent parts of the Ozark ward). These strata closely resemble interpreted the Bailey as comprising Dome rose. the Fayetteville Shale (Mississip- carbonate turbidites laid down in a During the Eifelian transgression, pian) of Arkansas, which likewise relatively deep basin. quartz sand from the St. Peter and represents an upward-shoaling The heavily silicified, unfossilifer- older sandstones exposed on the sequence (Handford 1986). Lime- ous Grassy Knob Chert is an enig- Ozark Dome was reworked into the stones of the Orchard Creek-Girar- matic unit. Although the unit is shoreline deposits that later became deau are confined to the flanks of partly carbonate rock outside of the the Dutch Creek Sandstone Member. the Ozark Dome and do not extend altered area, bedded chert persists This was followed by deposition of into the more rapidly subsiding Illi- into the deep subsurface. This indi- clean skeletal carbonate (upper mem- nois Basin to the east. cates that part of the Grassy Knob is ber of the Grand Tower) in shallow After regression and erosion primary silica. The lithologically subtidal settings. Tectonic action came deposition of shallow, subtidal similar and partly coeval Arkansas ushered in the Givetian Age; the sediments of the Leemon Formation, Novaculite and Caballos Novaculite crustal block north of the Ste. Gene- which were then largely removed by continue to engender controversy vieve Fault Zone rose (S. Weller and another cycle of erosion, bringing after more than 100 of study. St. Clair 1928, Nelson and Lumm Ordovician history to a close. These novaculites have been 1985), along with parts of the eastern assigned to settings that range from Ozark Dome. Fine terrigenous elas- intertidal to abyssal (McBride and tics from these sources intertongued

47 with shallow water carbonates of variety of predominantly shallow Cretaceous and Tertiary

the St. Laurent Formation. subtidal, carbonate-shelf deposi- The Tuscaloosa (?) and McNairy For- Another drop of sea level in late tional settings. Crossbedded oolitic mations (late Cretaceous) are largely Givetian or early Frasnian time and crinoidal grainstones alternate of fluvial origin, but some parts occurred, and the St. Laurent strata and intertongue with cherty lime probably are shallow marine. The were eroded. Transgression first mudstones and wackestones. These most obvious nonmarine units are brought basal sand (Sylamore Bed) represent offshore bars, and lagoons rooted silcretes. Poorly sorted, and then the main body of the New protected by bars, respectively clayey, and lithic sands and gravels Albany Shale. The latter was laid (Cluff and Lineback 1981). In the are interpreted as fluvial deposits. down in still water under anoxic, study area, Paleozoic sedimentary They are found mainly along a paleo- reducing conditions (Cluff et al. history drew to a close with the in- valley or paleochannel trending 1981). The Ozark Dome, except for flux of terrigenous elastics (Pope north-south in the eastern part of the "thumb area," continued to rise Group) from a source area north- the study area. The well sorted

during New Albany sedimentation. west of the region. "Commerce" quartz arenite, with its Near the end of the Devonian Period, bidirectional crossbedding, probably Late Mississippian through sea level dropped and the top of the is a shallow subtidal marine deposit. New Albany was beveled in the Early Cretaceous Some of the well sorted, well study area. No sedimentary record remains in rounded chert gravels that inter- the study area of early Chesterian grade with quartz arenite may be Mississippian through Late Cretaceous time marine also. The feather-edge of the Chouteau although many structural features Fossil flora indicate that both Limestone reached the northern part probably developed during this long Late Cretaceous (McNairy) and

of the study area during the Kinder- episode. Widespread folding and Eocene (Wilcox (?)) strata occur in hookian Age. This transgressive lime- faulting in adjacent areas reflect the the area. The possibility of deposits stone contains rip-up clasts from the compressional Alleghenian and of other ages cannot be eliminated. New Albany. The Chouteau was suc- Ouachita orogenies and later conti- The stratigraphic succession is still

ceeded disconformably (?) by the nental rifting (Kolata and Nelson poorly known.

Springville Shale (lower Valmey- 1991). The McNairy and Wilcox (?) re- eran), which was a distal, prograd- The Harrison Creek Anticline is semble the same formations in the ing clastic wedge of the Borden probably a late Paleozoic structure. Mississippi Embayment, but they delta (Lineback 1966). In the techni- Devonian rocks are folded, but Cre- are coarser and contain less mica in cally positive southwestern part of taceous-Tertiary strata on the north- the study area. An upland source of the study area, the Springville over- west flank, near the base of the sediment north of the Jonesboro stepped the New Albany onto the "thumb," rest unconformably on Quadrangle is indicated. Rocks underlying St. Laurent Formation. various Paleozoic units at nearly the north of the study area contain little After another relative fall and rise same elevation. Hence, the anticline mica, but they do contain abundant of sea level, siliceous carbonates probably is pre-Cretaceous. The Har- chert and quartz sand. Farther south (Fort Payne) accumulated on the rison Creek is similar in trend and in the Embayment, mica in the eroded surface of the Springville. structural style to anticlines in the McNairy Formation probably was Fine grain size, sparse fauna, thin central part of the Illinois Basin, derived from other sources in meta- even layering, and lack of high en- which underwent uplift from late morphic rocks of the Appalachian ergy sedimentary structures indicate Mississippian through Pennsylva- Mountains (Pryor 1960, Potter and relatively deep water (below wave nian time. A similar age for the Har- Pryor 1961). Small, well rounded base) for the Fort Payne. The source rison Creek Anticline is indicated. quartz pebbles are common in Creta- of silica in the Fort Payne has not The Atwood and Delta Faults and ceous-Tertiary deposits; the Casey- been addressed. Possible terrigenous smaller, parallel faults are high- ville Formation (Pennsylvanian), sources include the Borden delta angle normal faults nearly parallel which crops out extensively just

(contrary to Lineback 1966, the Bor- with the Harrison Creek Anticline. It north of the study area, is the prob- den and Fort Payne may be coeval) is unlikely that these extensional able source. and the Ouachita trough. Biogenic faults formed at the same time as the Faults that strike north-south silica may also be involved. The anticline. The faults displace De- and east-west displace Creta- gradual, intertonguing change from vonian rocks and are not known to ceous-Tertiary sediments. Both sets dark, fine grained, siliceous sedi- affect younger units. High-angle nor- of faults bear the earmarks of strike- ments of the Fort Payne to light, mal faults having similar trends dis- slip displacement. North-south coarse, crossbedded sediments of place Pennsylvanian rocks in the faults, notably the Cape Road Fault, the Ullin Limestone reflects shoaling Makanda (Jacobson and Weibel probably underwent right-lateral into high energy settings above nor- 1993) and Bloomfield Quadrangles slip having a large extensional or mal wave base. The prevalent cross- (Nelson 1993). This evidence indi- pull-apart component. East-west bedding of the Ullin is not in accord cates that the Atwood and Delta faults near Dago Hill seem to be left- with Lineback's (1966) hypothesis Faults are post-Pennsylvanian and lateral. Northeast-trending faults, in that the Ullin is a deep water de- younger than the Harrison Creek the southern part of the study area, posit filling in a "starved basin." Anticline. probably are strike-slip faults also. The Salem, St. Louis, and Ste. In the Thebes Quadrangle, northeast- Genevieve Limestones represent a trending faults exhibit right-lateral

48 displacement and deform units as Paleozoic rocks were leached of thermal fluids or merely recirculated young as the Mounds Gravel (Plio- carbonate and silicified in a large groundwater through the fracture cene to early Pleistocene). The im- part of the study area. This altera- systems via convection. The most plied stress field of these faults is tion is interpreted to be the product likely time of alteration was Late identical to the current stress regime of hydrothermal activity. Deep-seated Cretaceous to early Tertiary, when in southern Illinois and the New intrusions provided the heat, and a series of syenitic or mafic plutons Madrid Seismic Zone (Harrison and intersecting, closely spaced fault were intruded along the west edge Schultz 1992, Nelson and Harrison zones provided the pathways. The of the Mississippi Embayment (Hild- 1993). intrusions may have supplied hydro- enbrand 1984, Glick 1982).

49 ECONOMIC GEOLOGY

Silica Company, a predecessor of Unimin. the Markgraf Materials Company in The Jonesboro Quadrangle contains The Jason pit is partially backfilled. recent years. Chert from Tatumville some of the largest known micro- Remains of an abandoned silica mill, was used for making refractory crystalline silica deposits in the operator unknown, are in the SE, brick and for sodium silicate, as well United States. Several types of silica Sec. 33, T14S, R2W. Foundations of as for road surfacing and construc- have been mined here; they are settling tanks and several large tion materials (Lamar 1953). The called tripoli, bedded chert or "novac- grinding wheels made of limestone Lone Star Cement Company of Cape ulite," chert gravel, ganister, and cal- are at the site (fig. 35). Girardeau (Missouri) operates an ico rock. The first three are being Most active and abandoned trip- open-pit silica mine in the EVi NW, mined at present, whereas ganister oli mines in southern Illinois are in Sec. 15, T14S, R2W, Mill Creek Quad- and calico rock are chiefly of historic the Clear Creek Formation or in rangle. Interbedded chert and tripoli interest. All of these forms of silica undifferentiated Clear Creek and from this pit are used in manufactur- are products of the alteration of sedi- Grassy Knob (Lower Devonian). Re- ing Portland cement. Impurities of mentary rocks, mostly siliceous and cently active mines are in the upper clay and iron oxide, which are un- cherty limestones. Causes of altera- Clear Creek. A few mines may have wanted in a tripoli operation, are tion were covered previously in the operated in the Bailey Limestone desirable in cement making. Structural Geology section. (Silurian-Devonian). Deposits are Many small operators in the area Tripoli in Illinois is a white, soft more or less stratiform, but their lat- have dredged chert gravel from variety of microcrystalline silica. It is eral continuity is poorly documented. creek beds and used it for surfacing used widely as a filler, abrasive, and Bedded chert in the study area roads. Weathered chert from road- buffing and polishing compound. often is called "novaculite," because side outcrops is quarried for the Tripoli has been mined in the Jones- it somewhat resembles Arkansas same purpose. A small plant near boro Quadrangle since at least the novaculite. Large chert quarries are Alto Pass, north of the study area, early part of this century (Berg and in the bluffs west of Tatumville, near screens and sorts streambed gravel Masters 1994). Early mines were the southeast corner of the Mill for road metal and other uses. small room-and-pillar operations Creek Quadrangle. The largest pit, Water-worn chert gravel of Creta- accessed via slopes and drifts driven in the EVi NW, Sec. 36, T14S, R2W, ceous (?) age formerly was quarried into hillsides. Most old mines lacked has been operated intermittently by timbering and relied on natural air currents for ventilation. Silica was drilled, shot with explosives, and loaded into wagons or trucks for shipment to local mills or shipping terminals. We mapped more than 200 abandoned mine adits; doubt- less, many more are concealed by soil, slope wash, and vegetation. Unimin Specialty Minerals of Elco, Illinois, currently operates one underground tripoli mine, one open- cast mine, and one tripoli processing plant in the study area. The under- ground mine is in the SW SE, Sec. 27, T14S, R2W, Mill Creek Quadrangle; the open-cast mine is in the NE NE, Sec. 28, T14S, R2W. The mill is located at Elco and served by a rail- road spur. Another Unimin process- ing plant is located at Tamms, Illinois, immediately south of the study area. The Jason no. 2 Mine (SE, Sec. 22, T13S, R2W, Mill Creek Figure 35 Twin "chaser" grinding mills of an abandoned silica plant in the SE, Quadrangle) was operated until Sec. 33, T14S, R2W, Mill Creek Quadrangle. The limestone grinding wheels rolled about 1988 by the Illinois Minerals around circular tracks to crush the silica.

50 from a pit near Elco in the NE NE Ullin Limestone is similar to the ooli- history, and properties of the clay NW, Sec. 18, T14S, R1W (Lamar 1953). tic variety of the Ste. Genevieve in are in St. Clair (1917), Parmalee and Ganister is a coarsely granular that it is too soft to use as aggregate. Schroyer (1921), and Lamar (1948). form of silica derived from the altera- Some Ullin Limestone takes a good Similar deposits of clay may be pre- tion of siliceous limestone of the Fort polish and makes a handsome build- sent in the Jonesboro Quadrangle, Payne Formation (Mississippian). ing stone (Lamar and Willman but drilling would be needed to Ganister formerly was quarried and 1955). Ullin Limestone was formerly locate any such deposits. mined underground at several sites quarried for that purpose near Korn- in the Mill Creek Quadrangle. Sev- thal Church in Sec. 1, T13S, R2W, Oil and Gas eral abandoned underground mines and also near the center of the SVi, About 11 oil and gas test holes were are south of Cooper Creek in Sec. 1 Sec. 24, T12S, R2W (Jerome Lutz, drilled (records are ambiguous) in and 2, T14S, R2W; more are in the local resident, personal communica- the Jonesboro Quadrangle (table 2). hills east of Elco in Sec. 18, T14S, tion). High-calcium limestone is No commercial production or shows R1W. The ganister mines were also available from the upper part of the of oil or gas are reported for any of single-entry room-and-pillar drift Ullin Limestone in the study area. these wells. The deepest test was the mines. The mined ganister was Analyses by Lamar (1957) indicate Humble Oil Company no. 1 Pickel white to light gray, rather than the that this rock is composed of more well (Sec. 21, T13S, R2W, Mill Creek usual orange or reddish brown. It than 95% calcium carbonate. The Quadrangle), which reached a total was used in making fire bricks and Ullin is as much as 450 feet thick. depth of 8,492 feet in the Cambrian linings for ovens and kilns (Lamar The Salem Limestone potentially Lamotte/Mt. Simon Sandstone. The 1953). Other materials are currently has economic uses. This dark, hard Pickel well was sited near the struc- used for these applications, and min- stone is nearly chert-free and 300 to tural apex of the Harrison Creek ing of ganister in southern Illinois more than 400 feet thick. The Fort Anticline. Another test hole on the has ceased. Payne Formation is an extremely Harrison Creek structure was the Calico rock is a compact, blocky tough, siliceous stone that weathers Ohio Oil Company no. 1 Cross, also fractured siliceous rock derived to rough, pitted surfaces. This rock in Sec. 21. This well was abandoned from the alteration of the upper part may be usable for aggregate in at a total depth of 1,500 feet in the of the Springville Shale (Mississip- asphalt highways. The Fort Payne is Ordovician Everton Formation. The pian). It received its name from its quarried for that purpose at the only other relatively deep oil test attractive multicolored mottled and Reed Quarry east of Paducah, Ken- hole in the study area was the Mims banded surfaces. This material for- tucky. A small quarry in the Fort no. 1 Potashnick well, which was merly was quarried on a small scale Payne was formerly operated south drilled to a depth of 1,525 feet. Other in the study area and used for of Springville in the SW, Sec. 19, test holes listed in table 2 were shal- masonry in foundations, walls, well T13S, R2W, Mill Creek Quadrangle. low, most less than 500 feet deep. linings, and similar applications. The stone may have been used for These are listed as oil and gas explo- railroad ballast. ration wells in the files of the ISGS, Limestone Small amounts of high-calcium but other wells in the same area, The Jonesboro Quadrangle contains limestone might be obtainable from drilled at about the same time to abundant limestone resources, and the Grand Tower Limestone (Devo- similar depths by the same opera- several quarries are active just east nian) northwest of Jonesboro. tors, are listed as water wells. of the quadrangle. The Ste. Gene- The closest petroleum production vieve Limestone is quarried at the Clay and Shale is near Marion, Illinois, more than 20 Anna Quarry in the Anna Quadran- The Springville Shale (Mississip- miles northeast of the Jonesboro gle, and the Ullin Limestone is pian) was mined for use as roofing Quadrangle. extracted from the Jonesboro and granules from a pit south of Illinois The chief producing formations Ullin Quarries of the Columbia route 127 west of Jonesboro, NW of the Illinois Basin are the Ste. Gene- Quarry Company in the Dongola NE, Sec. 23, T12S, R2W. The opera- vieve Limestone and younger rocks, Quadrangle. tion consisted of an open pit and sev- which are eroded or at cropline in

The Ste. Genevieve is composed eral drifts (J.E. Lamar, unpublished the Jonesboro Quadrangle. The of interbedded light gray, soft, oolitic ISGS field notes, 1927). According to Salem and Ullin Limestones have limestone and lesser amounts of Lamar (1948), the shale mine was yielded oil in the deep Illinois Basin hard, somewhat cherty, dolomitic abandoned prior to 1925 because the and contain permeable beds, but limestone. Oolitic stone is well shale was found to be unsuitable for these limestones yield only water in suited for agricultural limestone, its intended use. the study area. The St. Laurent For- whereas the harder dolomitic lime- Kaolinitic clay was mined during mation, Dutch Creek Sandstone, and stone is used as aggregate and road- the early 1900s near the now-aban- Clear Creek Formation (all Devo- surfacing material. The two types of doned village of Kaolin, just north of nian) as well as the Kimmswick stone occur in distinct layers and the study area. The clay was a sedi- Limestone (Ordovician) support oil can be quarried in benches. The Ste. mentary deposit of Eocene age, and production elsewhere in the basin. Genevieve is about 250 feet thick in it filled structural depressions (sink- Stratigraphic traps may occur in the study area. holes or grabens ?) in Mississippian these units in the study area. Nega- The Ullin Limestone is used for limestone. Workings consisted of tive factors include the following: agricultural lime and road metal, as open pits and shafts as deep as 100 (1) facies changes in the St. Laurent well as in power plant scrubbers. feet. Details of the geology, mining and Dutch Creek seem to be in the

51 Table 2 Significant boreholes in the study area.

Deepest Total

Operator, farm Location unit depth (ft)

Anna City Well no. 1 (W)* NE NW SE, 18-12S-1W Ullin Ls 787 Anna City Well no. 2 (W) NW SE SE, 19-12S-1W Ullin Ls 428 Jonesboro City Well (W) SWNW,30-12S-1W Ullin Ls 302

Beanland no. 1 Dillow (W) NE NE SE, 31-12S-1W St. Laurent 660

Beanland no. 1 Ury (W) NE NW NW, 31-12N-1W Grand Tower Ls ? 577

McRauer no. 4 Jonesboro (W) SE NE SE, 25-12S-2W St. Laurent 1,300 (well was drilled to 1,300 ft but log only goes to 300 ft) Sturdevant no. 13 Turner (W?) SE NE NW, 25-12S-2W Springville Sh 110

Sturdevant no. 1 Ury (W) NW NW NW, 7-13S-1W St. Laurent 340

Sturdevant no. 2 Ury (W) SW NW NE, 7-13S-1W St. Laurent 489

Sturdevant no. 1 Barnhardt (W) SE NE NE, 19-13S-1W Springville Sh 329 Andrew Davis (W) SW SW NE, 31-13S-1W Clear Creek 678 Carl Howell (W) NE SW SE, 24-13S-2W Clear Creek 580

Schneider no. 1 Pearce (W) NW NE SW, 6-14S-2W Maquoketa Fm 390 Al Froemsdork (W) SW SW NE, 12-14S-3W Plattin Ls 558

J. Meyers (W) SW NE NW, 12-14S-3W Kimmswick Ls 430 Richard Mosby (W) NW NW NE, 12-14S-3W Kimmswick Ls 395 C.C.C. Camp Delta (W) NE SW, 20-14S-2W Clear Creek 405

Landers no. 1 Dillow (O) NENESW,3M2S-1W Clear Creek ? 700

Sturdevant no. 17 Andrews (O?) 750 ft N of C, 11-12S-2W Springville Sh 355 Sturdevant no. 18 Spurlock (O?) SW NW NE, 13-12S-2W Springville Sh 545 Sturdevant no. 19 State Pond (O?) NE NE SE, 14-12S-2W Grand Tower Ls 425 Sturdevant no. 14 Greer (O?) 200ftNofC,24-12S-2W Springville Sh 240

Sherman no. 1 Dossett (O) NE NW SE, 9-13S-2W no logs 1,078

Ohio Oil Company no. 1 Cross (O) NW NW NE, 21-13S-2W Everton Fm 1,500

Humble no. 1 Pickel (O) SE SE NW, 21-13S-2W Mt. Simon Ss 8,492

Staicup no. 1 Newell (O) SE SW SW, 19-14S-1W unknown (bad log) 390 Staicup no. 2 Newell (O) SW NE NW, 30-14S-1W unknown (bad log) 1,200

Mims no. 1 Potashnick (O) NW NW SE, 26-13S-3W Dutchtown Fm 1,525

ISGS no. J-l Rhodes (S) NE SE SE, 2-12S-2W McNairy Fm 51

ISGS no. J-2 Hunter (S) NW SE SE, 11-13S-2W McNairy Fm 74 ISGS no. MC-1 Dillow (S) SE NW SE, 24-13S-2W McNairy Fm ? 58

ISGS no. MC-2 Rosson (S) SE SE SW, 25-13S-2W McNairy Fm 71

ISGS no. MC-3 Moreland (S) NW SW SE, 25-13S-2W Fort Payne Fm 72

W: water well; O: oil test; S: stratigraphic test wrong direction—clastic content Fluorite and Metallic Ores rite was observed in cores from the and porosity increase westward, in No mining of fluorspar or metallic Ste. Genevieve near the quarry. In the up-dip direction; and (2) wide- ore is recorded for the study area, the Illinois-Kentucky fluorspar dis- spread jointing may have allowed but fluorite, manganese oxide, and trict east of the study area, fluorspar volatile hydrocarbons to escape. The metallic minerals occur in the area. occurs as vein deposits along faults altered area in the central part of the Fluorite occurs in the Ste. Gene- and as bedded-replacement depos- study area is a very poor petroleum vieve Limestone at the Anna Quarry its. The Ste. Genevieve Limestone prospect because the rocks are thor- just east of the study area. The min- and the lower part of the Pope oughly shattered, leached, and silici- eral occurs along with calcite in ver- Group are the principal host rocks fied. Any hydrocarbons originally tical joints that strike north-south to for fluorite there. present probably were expelled dur- N20°W and, to a lesser extent, along Manganese oxide was observed ing alteration. fractures within chert nodules. Fluo- or reported at several sites in the

52 in the chert, and found small pellets of manganese oxide in a manmade pit about Vs mile north of the gully. Iron-cemented chert breccia indi- cated a fault (confirmed by our map- ping) to Lamar. The site reported by Lamar is now densely overgrown with brush and brambles, and we did not observe any manganese min- erals near Berryville. Unusually high concentrations of metals were reported by Erickson et al. (1987) in cuttings from the Hum- ble no. 1 Pickel oil-test hole in the Mill Creek Quadrangle. Erickson et al. (1987) analyzed the cuttings from 29 deep wells around the western and southern borders of Illinois. Among these wells were one near Galena, Illinois, in the Upper Missis- sippi Valley zinc-lead district, and several in the Illinois-Kentucky Figure 36 A sample of mammillary manganese dioxide from the St. Laurent For- fluorspar district. The Pickel well mation near the Delta Fault, NE SE SE, Sec. 17, T14S, R2W, Mill Creek Quadrangle. had the highest concentrations of sil- ver, arsenic, and lead, the second study area. All manganese findings Creek in the SW, Sec. 16, T14S, R2W. highest concentration of molybde- are in the St. Laurent Formation Manganese oxide also lines joints num, and the third highest concen- (Devonian) along faults near the that strike N20°W in chert of the tration of copper. The silver content margins of the altered area. One site Clear Creek Formation along the of samples from the Pickel well was is in the east bank of a stream near bed of Sexton Creek near the center six times greater than that of any the Cape Road Fault at the south of the EV4, Sec. 9, T14S, R2W. A man- other well. Nickel and zinc concen- edge of the Jonesboro 7.5-Minute ganese prospect pit near Berryville, trations in the Pickel well were not Quadrangle (NW SE NW, Sec. 23, NW SE SW, Sec. 23, T12S, R2W, particularly high, but visible sphaler- T13S, R2W). Spheroidal and botry- Jonesboro Quadrangle, was reported ite crystals were noted in the Bonne- oidal pellets of black manganese by J.E. Lamar (unpublished ISGS terre Formation, which is the princi- oxide encrust altered siliceous lime- field notes, 1940). Local residents pal host rock for ore in the southeast stone at the top of the St. Laurent told Lamar that the pit was worked Missouri lead district. Formation about 20 feet above creek secretly around 1905, then concealed The discovery of high metal con- level. A second site is in a small gra- by blasting. Lamar in 1940 observed tent in the Pickel well raises the pos- ben east of the Delta Fault in a gully a vein in a gully near the reported sibility of ore in the study area. The in the NE SE SE, Sec. 17, T14S, R2W, site of the prospect pit. The vein was Pickel well is near the west edge of Mill Creek Quadrangle. Here, large as much as 12 inches wide and con- the altered area, which we think was mammillary nodules of manganese sisted of several parallel stringers of formed by hydrothermal activity. oxide (fig. 36) occur in altered silt- manganese oxide. It followed the The most likely area for ore at shal- stone of the St. Laurent Formation. bedding of "rotted ochreous chert," low depth is along the margins of Float of similar material was found which dipped 10° to 15° east. Lamar the altered area, especially where on a hillside southwest of Sexton also saw manganese ore along joints limestones abut against major faults.

53 REFERENCES

Allen, R.S., 1985, Petrology, paleon- Brower, E.C., 1973, Crinoids from Cumings, E.R., 1901, Use of Bedford tology and origin of the Clear the Girardeau Limestone (Ordovi- as a formational name: Journal of Creek Chert (Lower Devonian) in cian): Paleontographica Ameri- Geology, v. 9, p. 232-233. Union and Jackson Counties, cana, v. 7, no. 46, p. 263-499. Dake, C.L., 1918, The Sand and southwestern Illinois: M.S. thesis, Buschbach, T.C., 1975, Cambrian Sys- Gravel Resources of Missouri: Southern Illinois University, Car- tem, in H.B. Willman et al., eds., Missouri Bureau of Geology and bondale, 86 p. Handbook of Illinois Stratigraphy: Mines, vol. XV, 2nd Series, 274 p. Amsden, T.W., and J.E. Barrick, 1986, Illinois State Geological Survey, Devera, J.A., 1994, Geologic Map of Late Ordovician-Early Silurian Bulletin 95, p. 34-46. the Wolf Lake Quadrangle, South- Strata in the Central United Clendenin, C.W., CA. Niewendorp, ern Illinois: Illinois State Geologi- States and the Hirnantian Stage: and G.A. Lowell, 1989, Reinter- cal Survey, Illinois Geologic Geological Survey, pretation of faulting in southeast Quadrangle 13, scale 1:24,000. Bulletin 139, 95 p. Missouri: Geology, v. 17, no. 3, Devera, J.A., and W. John Nelson, Atherton, Elwood, Charles Collin- p. 217-220. 1995, Geologic Map of the Cobden

son, and J. A. Lineback, 1975, Cluff, R.M., and J.A. Lineback, 1981, Quadrangle, Southern Illinois: Mississippian System, in H.B. Middle Mississippian Carbonates Illinois State Geological Survey, Willman et al., eds., Handbook of of the Illinois Basin: Illinois Geo- Illinois Geologic Quadrangle 16, Illinois Stratigraphy, Illinois State logical Society /Illinois State Geo- scale 1:24,000. Geological Survey, Bulletin 95, logical Survey, 88 p. Devera, J.A., W.J. Nelson, and J.M. p. 123-163. Cluff, R.M., M.L. Reinbold, and J.A. Masters, 1994, Geologic Map of Ball, J.R., 1939, Type section of Bain- Lineback, 1981, The New Albany the Mill Creek and McClure bridge Formation of southeastern Shale Group of Illinois: Illinois Quadrangles in Alexander and Missouri: American Association State Geological Survey, Circular Union Counties, Illinois: Illinois of Petroleum Geologists Bulletin, 518, 83 p. State Geological Survey, Illinois v. 23, p. 595-601. Collinson, Charles, L.H. Becker, M.P Geologic Quadrangle 15, scale Banaee, Jila, 1981, Microfacies and Carlson, F.H. Dorheim, G.W. 1:24,000. depositional environment of the James, J.W. Koenig, and D.H. Englemann, George, 1847, Remarks Bailey Limestone (Lower De- Swann, 1967, Devonian of the on the St. Louis Limestone: vonian), southwestern Illinois: a north-central region, United American Journal of Science, v. 3, carbonate turbidite: M.S. thesis, States, in H. Oswald, ed., Interna- p. 119-120. University of Illinois, Urbana, tional Symposium on the Devon- Erickson, R.L., M.S. Erickson, Bar- 61 p. ian System: Calgary, v. 1, p. 933- bara Chazin, J.W. Baxter, J.M.

Baxter, J.W., and G.R. Desborough, 971. Masters, and J.J. Eidel, 1987, Sub- 1965, Areal Geology of the Illinois Collinson, Charles, and Elwood surface Geochemical Investiga- Fluorspar District, Part 2, Karbers Atherton, 1975, Devonian System, tion in Western and Southern Ridge and Rosiclare Quadrangles: in H.B. Willman et al, ed., Hand- Illinois: A Pilot Study: Illinois Illinois State Geological Survey, book of Illinois Stratigraphy: Illi- State Geological Survey, Illinois Circular 385, 40 p. nois State Geological Survey, Mineral Note 98, 45 p. Baxter, J.W., G.R. Desborough, and Bulletin 95, p. 104-123. Fraser, D.R., 1980, Late Pleistocene C.W. Shaw, 1967, Areal Geology Collinson, Charles, and A.J. Scott, fluvial-lacustrine history of the of the Illinois Fluorspar District, 1958, Age of the Springville Shale Hutchins Creek-Clear Creek val- Part 3, Herod and Shetlerville (Mississippian) of Southern Illi- ley, southern Illinois: M.S. thesis, Quadrangles: Illinois State Geo- nois: Illinois State Geological Sur- Southern Illinois University, Car- logical Survey, Circular 413, 41 p. vey, Circular 254, 12 p. bondale, 123 p. Berg, R.B., and J.M. Masters, 1994, Cooper, G.A. et al., 1942, Correlation Glick, E.E., 1982, Stratigraphy and Geology of Microcrystalline Silica of the Devonian Sedimentary for- structure of post-Paleozoic sedi- (Tripoli) Deposits, Southernmost mations of North America: Geo- ments above the Newport pluton Illinois: Illinois State Geological logical Society of America Bulle- of northeastern Arkansas: U.S. Survey, Circular 555, 89 p. tin, v. 53, p. 1729-1794. Geological Survey, Professional Borden, W.W., 1874, Report of a geo- Croneis, Carey, 1944, The Devonian Paper 1236, p. 151-174. logical survey of Clark and Floyd of southeastern Missouri: Illinois Handford, C.R., 1986, Facies and Counties, Indiana: Indiana Geo- State Geological Survey, Bulletin bedding sequences in shelf-storm- logical Survey, Annual Report 5, 68, p. 103-131. deposited carbonates—Fayette- p. 134-189. ville Shale and Pitkin Limestone

54 (Mississippian), Arkansas: Jour- Keyes, C.R., 1894, Paleontology of Lowenstam, H.A., 1949, Niagaran nal of Sedimentary Petrology, Missouri (Part 1): Missouri Geo- Reefs in Illinois and Their Rela-

v. 56, no. 1, p. 123-137. logical Survey, v. 4, 271 p. tion to Oil Accumulation: Illinois Harding, T.P., 1985, Seismic charac- Kolata, D.R., and W.J. Nelson, 1991, State Geological Survey, Report of teristics and identification of nega- Tectonic history of the Illinois Investigations 145, 36 p. tive flower structures, positive Basin, in M.W. Leighton, D.R. Martin, J.A., R.D. Knight, and WC.

flower structures, and positive Kolata, D.F Oltz, and J.J. Eidel, Hayes, 1961, Ordovician System, structural inversion: American eds., Interior Cratonic Basins, in W.B. Howe, coordinator, The Association of Petroleum Geolo- American Association of Petro- Stratigraphic Succession in Mis- gists Bulletin, v. 69, no. 4, leum Geologists Memoir, 51, souri: Missouri Geological Sur- p. 582-600. p. 263-285. vey, v. 40, 2nd Series, p. 20-32. Harrison, R.W., in preparation, Kolata, D.R., and M.C. Noger, 1991, McBride, E.F and R.L. Folk, 1977,

Geologic Map of the Thebes Tippecanoe I Subsequence, Mid- The Caballos Novaculite revis- Quadrangle, Illinois-Missouri: dle and Upper Ordovician Series, ited: Part II: chert and shale mem- U.S. Geological Survey, GQ in M.W. Leighton, D.R. Kolata, bers and synthesis: Journal of

Series, scale 1:24,000. D.F. Oltz, and J.J. Eidel, eds., Inte- Sedimentary Petrology, v. 47, no. 3, Harrison, R.W., and A.P Schultz, rior Cratonic Basins: American p. 1261-1286. 1992, Faulting at Thebes Gap, Association of Petroleum Geolo- McCracken, M.H., 1971, Structural Illinois-Missouri: implications gists Memoir 51, p. 89-99. Features of Missouri: Missouri for New Madrid tectonism Kolata, D.R., J.D. Treworgy, and J.M. Geological Survey, Report of (abstract): Geological Society of Masters, 1981, Structural Frame- Investigations 49, 99 p. America, Abstracts with Pro- work of the Mississippi Embay- Meents, WE, and D.H. Swann. 1965, grams 1992, p. 190. ment of Southern Illinois: Illinois Grand Tower Limestone (Devo- Hayes, W.C., and R.D. Knight, 1961, State Geological Survey, Circular nian) of Southern Illinois: Illinois Cambrian System, in W.B. Howe, 518, 38 p. State Geological Survey, Circular coordinator, The Stratigraphic Lamar, J.E., 1948, Clay and Shale 389, 34 p. Succession in Missouri: Division Resources of Extreme Southern Middendorf, M.A., 1989, Geologic of Geological Survey and Water Illinois: Illinois State Geological Map of the Missouri Portion of Resources, vol. XL, 2nd Series, Survey, Report of Investigations the Ware Quadrangle: Missouri p. 14-20. 128, 107 p. Geological Survey, scale 1:24,000. Heigold, PC., and D.R. Kolata, 1993, Lamar, J.E., 1953, Siliceous Materials Middendorf, M.A., J.W Whitfield, crustal boundary in of Extreme Southern Illinois: Illi- and C.E. Robertson, 1988, Geo- the southern part of the Illinois nois State Geological Survey, Re- logic Map of the Cape Girardeau Basin: Tectonophysics, v. 217, port of Investigations 166, 39 p. Northeast Quadrangle, Missouri: p. 307-319. Lamar, J.E., 1957, Chemical Analyses Missouri Division of Geology and Hershey, O.H., 1894, The Elk Horn of Illinois Limestones and Dolo- Land Survey, scale 1:33,000. area of St. Peter Sandstone in mites: Illinois State Geological Moody, C.L., 1949, Mesozoic igne- northwestern Illinois: American Survey, Report of Investigations ous rocks of the northern Gulf Geologist, v. 14, p. 169-179. 200, 33 p. Coastal Plain: American Associa- Hildenbrand, T.G., 1984, Rift struc- Lamar, J.E., 1959, Limestone Re- tion of Petroleum Geologists Bul- ture of the northern Mississippi sources of Extreme Southern Illi- letin, v. 33, p. 1410-1428. Embayment from the analysis of nois: Illinois State Geological Nelson, W.J., 1991, Structural styles gravity and magnetic data, in PL. Survey, Report of Investigations of the Illinois Basin, in M.W. Gori and W.W. Hays, eds., Pro- 211, 81 p. Leighton, D.R. Kolata, D.F. Oltz,

ceedings of the Symposium on Lamar, J.E., and H.B. Willman, 1955, and J.J. Eidel, eds., Interior Cra- the New Madrid Seismic Zone: Illinois Building Stones: Illinois tonic Basins: American Associa- U.S. Geological Survey, Open State Geological Survey, Report of tion of Petroleum Geologists, File Report 84-770, p. 168-203. Investigations 184, 24 p. Memoir 51, p. 209-243. Jacobson, R.J., and C.P. Weibel, 1993, Leighton, M.M., G.E. Ekblaw, and Nelson, W.J., 1993, Geology of the Geologic Map of the Makanda C.L. Horberg, 1948, Physiog- Bloomfield Quadrangle, Johnson Quadrangle, Jackson, Union and raphic divisions of Illinois: Jour- County, Illinois: Illinois State Geo- Williamson Couties, Illinois: Illi- nal of Geology, v. 56, p. 16-33. logical Survey, Bulletin 99, 30 p. nois State Geological Survey, Illi- Lineback, J.A., 1966, Deep-Water Nelson, W.J., 1995, Bedrock Geology nois Geologic Quadrangle 11, Sediments Adjacent to the Borden of the Paducah l°x2° Quadrangle: scale 1:24,000. Siltstone (Mississippian) Delta in Illinois State Geological Survey, Johnson, W.D., 1985, Geologic Map Southern Illinois: Illinois State Bulletin 102. of the Scott City Quadrangle and Geological Survey, Circular 401, Nelson, W.J., and R.D. Cole, 1992, Re- part of the Thebes Quadrangle, 48 p. gional intertonguing of lithologic Scott and Cape Girardeau Coun- Lineback, J.A., 1972, Lateral Grada- intervals, Pope (Chester) Group, ties, Missouri: U.S. Geological Sur- tion of the Salem and St. Louis Illinois Basin (abstract): American vey, Map MF-1803, 2 sheets, scale Limestones (Middle Mississip- Association of Petroleum Geolo- 1:24,000. pian) in Illinois: Illinois State Geo- gists Bulletin, v. 76, no. 8, p. 1282. logical Survey, Circular 474, 21 p. Nelson, W.J., and J.A. Devera, 1994, Geologic Map of the Jonesboro

55 and Ware Quadrangles in Union logical Survey, Circular 332, 39 p., Savage, T.E., 1920a, Devonian forma- County, Illinois: Illinois State Geo- with map, scale 1:62,500. tions of Illinois: American Journal logical Survey, Illinois Geologic Rexroad, C.B., and W.W. Craig, 1971, of Science, v. 49, p. 169-182. Quadrangle 14, scale 1:24,000. Restudy of conodonts from the Savage, T.E., 1920b, Geology of Nelson, W.J., and R.W. Harrison, Bainbridge Formation (Silurian) at Jonesboro 15-Minute Quadrangle, 1993, Post-Cretaceous faulting at Lithium, Missouri: Journal of Pale- Illinois: Illinois State Geological head of Mississippi Embayment: ontology, v. 45, no. 4, p. 684-703. Survey, unpublished manuscript Geological Society of America, Rogers, J.E., 1972, Silurian and with geologic map, scale 1:62,500. Abstracts with Programs, North- Lower Devonian stratigraphy Savage, T.E., 1925, Oriskany rocks Central Section, p. 69-70. and paleobasin development, Illi- in Illinois: American Journal of Nelson, W.J., and D.K. Lumm, 1985, nois Basin, central United States: Science, 5th Series, v. 10, no. 56, Ste. Genevieve Fault Zone, Mis- Ph.D. thesis, University of Illinois, p. 139-144. souri and Illinois: U.S. Nuclear Urbana-Champaign, 144 p. Segar, R.L., 1965, A gravity and mag- Regulatory Commission NUREG/ Ross, C.A., 1962, Silurian monograp- netic investigation along the east- CR-4333, 94 p. tids from Illinois: Palaeontology, ern flank of the Ozark Uplift: North, W.G., 1969, The Middle Devo- v. 5, part 1, p. 59-72. M.A. thesis, Washington Univer- nian Strata of Southern Illinois: Sable, E.G., and G.R. Dever, 1990, sity, St. Louis, Missouri, 163 p. Illinois State Geological Survey, Mississippian Rocks in Kentucky: Shaver, R.H., coordinator, 1985, Circular 441, 45 p. U.S. Geological Survey, Profes- Midwestern Basins and Arches North American Stratigraphic Code, sional Paper 1503, 125 p. Region: Correlation of Strati- 1983, The North American Com- St. Clair, Stuart, 1917, Clay deposits graphic Units of North America mission on Stratigraphic Nomen- near Mountain Glen, Union (COSUNA) Project: American clature: American Association of County, Illinois: Illinois State Geo- Association of Petroleum Geolo- Petroleum Geologists Bulletin, logical Survey, Bulletin 36, p. 71- gists, Tulsa, Oklahoma. v. 67, no. 5, p. 841-875. 83. Shumard, B.F, 1855, Geological sec-

Norton, J. A., 1966, Petrology of the Sando, W.J., 1983, Revision of Litho- tion on the Mississippi River Lingle Limestone, Union County, strotionella (Coelenterata, Rugosa) from St. Louis to Commerce: Mis- Illinois: M.S. thesis, Southern Illi- from the and Per- souri Geological Survey, Annual nois University, Carbondale, 101 p. mian: U.S. Geological Survey, Pro- Report 1-2, p. 139-208. Olive, W.W., 1980, Geologic Maps of fessional Paper 1247, 47 p. Shumard, B.F, 1859, Observations the Jackson Purchase Area, Ken- Sargent, M.L., 1991, Sauk Sequence, on the geology of the county of tucky: U.S. Geological Survey Cambrian System through Lower Ste. Genevieve, Missouri: Transac- Map 1-1217, 11 p. and map. Ordovician Series, in M.W. Leigh- tions of the Academy of Science

Orr, R.W., 1964, Conodonts from the ton, D.R. Kolata, D.F. Oltz and J.J. of St. Louis, v. 1, p. 404-105. Devonian Lingle and Alto Forma- Eidel, eds., Interior Cratonic Smith, E.A., 1890, Geologic structure tions of Southern Illinois: Illinois Basins: American Association of and description of the valley re- State Geological Survey, Circular Petroleum Geologists Memoir 51, gions adjacent to the Cahaba coal 361, 28 p. p. 75-85. field, in Report on the Cahaba Parmalee, C.W., and C.R. Schroyer, Satterfield, I.R., 1971, Conodonts Coal Field (part 2): Alabama Geo- 1921, Further Investigation of and stratigraphy of the Girardeau logical Survey, p. 137-180. Illinois Fire Clay: Illinois State Limestone (Ordovician) of south- Summerfield, M.A., 1983, Silcrete as

Geological Survey, Bulletin 38, east Missouri and southwest Illi- a palaeoclimatic indicator: evi- p. 272-417. nois: Journal of Paleontology, v. 45, dence from southern Africa:

Penrose, R.A.F., Jr., 1891, Batesville p. 264-273. Palaeogeography, Palaeoclimatol- region of Arkansas: Arkansas Satterfield, I.R., 1973, Bedrock Geo- ogy, Palaeoecology, v. 41, p. 65-79. Geological Survey, Annual Re- logic Map of the Cape Girardeau- Swallow, G.C., 1855, The First and

port for 1890, v. 1, p. 102-174. McClure Quadrangles, Southeast- Second Annual Reports of the Potter, RE., and W.A. Pryor, 1961, ern Missouri: Missouri Geological Geological Survey of Missouri: Dispersal centers of Paleozoic Survey, Open-File Map OFM-82- Missouri Geological Survey, 239 p. and later elastics of the upper 73-G1. Swann, D.H., 1963, Classification of Mississippi Valley and adjacent Satterfield, I.R., and T.L. Thompson, Genevievian and Chesterian areas: Geological Society of Amer- 1975, Seventy-Six Shale, a new (Late Mississippian) Rocks in Illi- ica Bulletin, v. 72, no. 8, p. 1195- member of the Bainbridge Forma- nois: Illinois State Geological Sur- 1294. tion (Silurian) in southeastern vey, Report of Investigations 216, Pryor, W.A., 1960, Cretaceous sedi- Missouri: Missouri Geological 91 p. mentation in upper Mississippi Survey, Report of Investigations Swann, D.H., and H.B. Willman, embayment: American Associa- 57, p. 109-119. 1961, Megagroups in Illinois: tion of Petroleum Geologists Bul- Savage, T.E., 1909, The Ordovician American Association of Petro- letin, v. 44, no. 9, p. 1473-1504. and Silurian formations in Alex- leum Geologists Bulletin, v. 45, Pryor, W.A., and C.A. Ross, 1962, ander County, Illinois: American p. 471-483.

Geology of the Illinois Parts of Journal of Science, 4th Series, v. 28, Sweet, W.C., T.L. Thompson, and the Cairo, LaCenter, and Thebes p. 509-519. I.R. Satterfield, 1975, Conodont Quadrangles: Illinois State Geo- Stratigraphy of the Cape Lime- stone (Maysvillian) of Eastern

56 Missouri: Missouri Geological ley and H.A. Buehler, eds.: Mis- tion: Illinois State Geological Sur- Survey, Report of Investigations souri Bureau of Geology and vey, Illinois Petroleum 130, 32 p. 57, p. 1-60. Mines, 2nd Series, v. 2, p. 109-111. White, C.A., 1870, Report on Geo-

Templeton, J.S., and H.B. Willman, Weibel, C.R, W.J. Nelson, L.B. Oliver, logical Survey of Iowa: Iowa Geo- 1963, Champlainian Series (Mid- and S.P Esling, 1993, Geology of logical Survey, v. 1, 391 p. dle Ordovician) in Illinois: Illinois the Waltersburg Quadrangle, Whitfield, J.W, and M.M. Midden- State Geological Survey, Bulletin Pope County, Illinois: Illinois dorf, 1988, Geologic Map of the 89, 260 p. State Geological Survey, Bulletin Neely's Landing Quadrangle, Thomas, W.A., 1972, Mississippian 98, 41 p. Missouri: Missouri Division of Stratigraphy of Alabama: Geologi- Weller, J.M., 1944, Devonian System Geology and Land Survey, scale cal Survey of Alabama, Mono- in Southern Illinois: Illinois State 1:33,000. graph 12, 121 p. and 13 plates. Geological Survey, Bulletin 68, Wilcox, Ronald E., T.P. Harding, and Thompson, T.L., 1987, Stratigraphic p. 89-102. D.R. Seely, 1973, Basic wrench tec- column for Perry County, Mis- Weller, J.M., 1948, Correlation of the tonics: American Association of souri, in Frank Adler, coordinator, Mississippian formations of Petroleum Geologists Bulletin,

Mid-Continent Region, Correla- North America: Geological Soci- v. 57, no. 1, p. 74-96. tion of Stratigraphic Units in ety of America Bulletin, v. 59, no. Willman, H.B., and Elwood Ather-

North America (COSUNA) Pro- 1, p. 91-196. ton, 1975, Silurian System, in H.B. ject: American Association of Weller, J.M., and G.E. Ekblaw, 1940, Willman et al., eds., 1975, Hand- Petroleum Geologists, Tulsa. Preliminary Geologic Map of book of Illinois Stratigraphy: Illi- Thompson, T.L., 1991, Paleozoic Suc- Parts of the Alto Pass, Jonesboro nois State Geological Survey, cession in Missouri, Part 2: Ordo- and Thebes Quadrangles: Illinois Bulletin 95, p. 87-104. vician System: Missouri Geological State Geological Survey, Report of Woodcock, N.H., and Mike Fischer, Survey, Report of Investigations Investigations 70, 26 p. with map, 1986, Strike-slip duplexes: Journal 70, 282 p. scale 1:62,500. of Structural Geology, v. 8, no. 7, Thompson, T.L., and I.R. Satterfield, Weller, Stuart, and Stuart St. Clair, p. 725-735. 1975, Stratigraphy and conodont 1928, Geology of Ste. Genevieve Workman, L.E., and Tracey Gillette, biostratigraphy of strata conti- County, Missouri: Missouri Bureau 1956, Subsurface Stratigraphy of guous to the Ordovician-Silurian of Geology and Mines, vol. XXII, the Kinderhook Series in Illinois: boundary in eastern Missouri: 2nd Series, 352 p. Illinois State Geological Survey, Missouri Geological Survey, Wheeler, E.F., Michael Lee, and L.C. Report of Investigations 189, 46 p. Report of Investigations 57, part 2, Matten, 1987, Dicotyledonous Worthen, A.H., 1866, Geology: Illi- p. 61-108. woods from the Upper Creta- nois Geological Survey, v. 1, 504 p. Trace, R.D., and D.H. Amos, 1984, ceous of southern Illinois: Botani- Zartman, R.E., M.R. Brock, A.V. Stratigraphy and Structure of the cal Journal of the Linnean Society, Heyl, and H.H. Thomas, 1967, K- Western Kentucky Fluorspar Dis- v. 95, p. 77-100. Ar and Rb-Sr ages of some alkalic trict: U.S. Geological Survey, Pro- Whitaker, ST., 1988, Silurian Pinna- intrusive rocks from central and fessional Paper 1151-D, 41 p. cle Reef Distribution in Illinois: eastern United States: American Ulrich, E.O., 1904, The quarrying Model for Hydrocarbon Explora- Journal of Science, v. 265, no. 10, industry in Missouri, in E.R. Buck- p. 848-870.

57

Siliceous limestone of the Fort Payne Formation cropping out north of Lingle Creek.