STRUCTURE AND TECTONICS OF THE ROUGH CREEK GRABEN WESTERN KENTUCKY AND SOUTHEASTERN ILLINOIS W. John Nelson Donald K. Lumm ISGS Guidebook 24 1992 Department of Energy and Natural Resources ILLINOIS STATE GEOLOGICAL SURVEY STRUCTURE AND TECTONICS OF THE ROUGH CREEK GRABEN WESTERN KENTUCKY AND SOUTHEASTERN ILLINOIS W. John Nelson Donald K. Lumm Prepared for the Annual Meeting of the Geological Society of America Cincinnati, Ohio October 26-29, 1992 ISGS Guidebook 24 1992 ILLINOIS STATE GEOLOGICAL SURVEY Morris W. Leighton, Chief Natural Resources Building 615 East Peabody Drive Champaign, Illinois 61820 Cover photo by D. L. Reinertsen (Illinois State Geological Survey). Horseshoe Quarry, looking east. Steeply dipping beds are siliceous limestone of Fort Payne Formation. This photo was taken in 1960 when the quarry was much less overgrown by vegetation. Printed by authority of the State of lllinois/1992/WO0 CONTENTS INTRODUCTION 1 STRUCTURAL HISTORY 1 Cambrian 1 Ordovician 4 Silurian and Devonian 4 Carboniferous 4 Post-Pennsylvanian 4 REGIONAL FAULT SYSTEMS 5 Rough Creek-Shawneetown Fault System 5 Lusk Creek Fault Zone 6 Pennyrile Fault System 6 DISCUSSION 7 FIELD-TRIP STOPS 7 Stop 1 7 Stop 2 9 Stop 3 10 Stop 4 10 Optional Stop 4a 12 Stop 5 12 Stop 6 13 Optional Stop 6a 13 Stop 7 13 Stop 8 16 ACKNOWLEDGMENTS 17 REFERENCES CITED 18 ROAD LOG 21 FIGURES 1 Map showing regional structural features and locations of field-trip stops 1 2 Generalized stratigraphic column for western part of Rough Creek graben 2 3 Tracing from seismic section showing interpreted structure of Rough Creek-Shawneetown fault system northwestern Webster County, Kentucky 3 4 Illustrated profile of the east side of the Green River Parkway at Stop 1 6 5 Interpretive diagram showing relationship of structures at Stop 1 to the master fault of the Rough Creek fault system 8 6 Illustrated profile of the east side of the Hoover Hill roadcut, Stop 2 8 7 Illustration of paleoslump at Sebree interchange, Stop 3 10 8 Photograph of Horseshoe Quarry, looking east 11 9 Interpretive cross section at Horseshoe Quarry (Stop 4) and Horseshoe Gap (Stop 4a) 12 10 Cross section of Lusk Creek fault zone at Clay Diggings (Stop 5) 13 11 Illustrated profile of the east side of the CSX Railroad cut north of Crofton, Kentucky (Stop 7) 14 12 Illustrated profile of the roadcuts on the east side of the Pennyrile Parkway north of Crofton, Kentucky 16 Route map of the field-trip area 20 Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/structuretectoni24nels Reelfoot rift and Rough Creek graben; boundaries dotted where concealed in Mississippi Embayment boundary of Mississippi Embayment reverse fault; upthrown side indicated normal fault; downthrown side indicated strike-slip fault 't— anticline syncline monocline field-trip stop Figure 1 Map showing regional structural features and locations of field-trip stops (circled numbers). INTRODUCTION This field trip focuses on the structure and tectonic history of the surface faults that outline a failed intracra- tonic rift or aulacogen. The Rough Creek graben is the eastern segment of a dogleg-shaped aulacogen in the central Mississippi Valley (fig. 1). The southwestern segment of the aulacogen is known as the Reelfoot rift. The Rough Creek graben and the Reelfoot rift are prod- ucts of continental breakup near the beginning of the Cambrian Period. Their boundary faults have been re- peatedly reactivated under different stress fields throughout Phanerozoic time. Segments of the bound- ary faults that displace surface bedrock are the Rough Creek-Shawneetoum fault system along the northern bor- der of the Rough Creek graben, the Lusk Creek fault zone along the northwest margin of the Reelfoot rift, and the Pennyrile fault system along the southern border of the Rough Creek graben (fig. 1). Evidence for Pennsylvanian and younger displace- ments of these faults will be examined on this field trip. At many of the field-trip stops, there is evidence for two or more episodes of displacement, commonly involving reversals in the direction of throw. A stratigraphic column (fig. 2) illustrates the Paleo- zoic units mentioned in this field guide. STRUCTURAL HISTORY CAMBRIAN The Rough Creek graben was named and defined on the basis of geophysical data by Soderberg and Keller (1981), although Avila (1971) and Smith and Palmer (1974) earlier postulated a pre-Knox (Late Cambrian or older; fig. 2) graben south of the Rough Creek fault system. Gravity, magnetic, and borehole data confirm the presence of the graben, and seismic sections provide detailed information on its structure. We have examined System Series Formation Group PENN. Upper McLeansboro _i 1— — ■ — . . _ . _ «r-l T ■ 1 Carbondale Tradewater Middle — — — Lower . ..©... ^ ..:». \ »: •'• Caseyville MISS. Chest. 1 . . . .~ r .-'~"^~ — - J — ^-x_5> i i i i r* i i i i i (many) Pope Valm. ! 1 1 1 Ste. Genevieve St. Louis Fort Payne Mammoth Cave I I 1 1 A 1 A 1 Al i r i II 1 1 A 1 A A | A A 1 A A|A A|A A|A A|A DEV. Upper New Albany Middle 1 1 1 1 1 Sellersburg- Jeffersonville TT-rT — r-r^-r~r-T--r~^~ Lower Clear Creek 1 A / A / A A Pi A | A A | A 1 A A / A / A SIL 1 - 1 1 1 - 1 -1 1 l~l- ORD. Cine. Maquoketa Champ. 1 1 1 1 1 1 1 1 / 1 / / / 1 / Canad. ■■ : /:v::/''' : '/:::' \ St. Peter I / ' / / / Knox / /a /- . J / ■ ■ / / A / / * / / / /• • • /••■ / A /.../' CAM. Upper or St. Croixan A / A / A / / A / /A / • ■ - / / /■ / A / / f / /-A / A / / f / / / ../ A /■• / A / / / / •/* / / / ' / A / ../ / A /.. / / / / * A ■■/ /■/ Mt. Simon : : : :.'.'.!: : .- 1 -'. : : . .". PRECAMBRIAN Crystalline rocks t Lower and Middle Cam- brian (?) clastic rocks in Rough Creek Graben V , l\- \ 1 | ! A / \ > 7\ . * , " iv-i-d ^ -> \ ' " l r-~- ^ \/ \ j m ft O-i-O 1500-1-5000 Figure 2 Generalized stratigraphic column for western part of Rough Creek graben, with names of units mentioned in this guidebook. Chesterian and Pennsylvanian strata Valmeyeran strata Silurian and Devonian strata Middle and Upper Ordovician strata Precambrian crystalline ^ basement 1 Figure 3 Tracing from seismic section (Bertagne and Leising, 1991, fig. 15-2) showing interpreted structure of Rough Creek fault system in northwestern Webster County, Kentucky. Fault system marks northern margin of Rough Creek graben, which contains a greater thickness of Middle and Lower (?) Cambrian strata. Discrepancies in thicknesses of units on opposite sides of faults reflect reversals of displacement. Original figure lacked a scale; depth to basement is approximately 14,000 feet (4300 m) north of fault system and 23,000 feet (7,000 m) south of fault system. published and proprietary seismic reflection sections acquired by oil companies. They demonstrate the pres- ence of the pre-Knox graben. Four sections reproduced in Bertagne and Leising (1991) show the following: • Below the Knox Group, the master fault of the Rough Creek-Shawneetown fault system is a listric normal fault that dips south and penetrates crystalline base- ment (fig. 3). Pre-Knox strata are as much as 8,000 feet (2,440 m) thicker south of the fault than they are north of the fault. Within the graben, pre-Knox strata are thicker to the north, toward the fault. • Configuration of the Lusk Creek fault zone is similar to that of the Rough Creek-Shawneetown fault system, but displacements are smaller (Bertagne and Leising, 1991, their fig. 15.4). • The Pennyrile fault system marks the approximate southern boundary of the graben. This system is com- posed of high-angle, partly listric normal faults that dip northward and have pre-Knox displacements of as great as several thousand feet (Bertagne and Leising, 1991, their fig. 15.5). • Within the Rough Creek graben are horsts and gra- bens that are outlined by pre-Knox listric faults (Bert- agne and Leising, 1991, their fig. 15.6). The only well to date that has been drilled into the pre-Knox graben-fill is the Texas Gas Exploration Com- pany No. 1 Shain in Grayson County, Kentucky, near the east end of the Rough Creek graben. This well pene- trated 2,360 feet (720 m) of pre-Knox shale containing thin lenses of arkose and a few thin beds of oolitic limestone. Middle Cambrian trilobites in the shale were identified by C Lochman-Balk (Schwalb, 1982). The well did not penetrate the crystalline basement. The Rough Creek graben is one of several aulacogens that developed in North America as a result of the breakup of a supercontinent near the beginning of the Cambrian Period (Keller et al., 1983; Bond et al., 1984; Kolata and Nelson, 1991a, 1991b). Rifting and concurrent sedimentation in the Rough Creek graben may have commenced during the Proterozoic Eon, but most of the action probably took place during Early and Middle Cambrian time. Most faulting had ceased by St. Croixan (Late Cambrian) time, but the graben area continued to be a depocenter controlled by thermal and isostatic subsidence (Kolata and Nelson, 1991b; Treworgy et al., 1991). ORDOVICIAN Thermal and isostatic subsidence continued in the Reel- foot rift during the Ordovician Period (Kolata and Nel- son, 1991b; Treworgy et al., 1991). Most faults in the graben apparently were inactive, although segments of the Rough Creek and Lusk Creek fault zones were reac- tivated as reverse faults during the St. Croixan or Cana- dian Epoch. Seismic sections by Bertagne and Leising (1991, their figs. 15.2 and 15.4) show the Knox Group to be thicker by as much as 1,600 feet (530 m) north of the faults. The interpretations of Bertagne and Leising are in agreement with our interpretations of unpublished, pro- prietary seismic sections in the same area. Other pro- prietary seismic sections show a greater thickness of the Knox Group north of parts of the Cottage Grove fault system in southern Illinois. St. Croixan and Canadian strata are displaced down to the north on all of these fault systems. SILURIAN AND DEVONIAN So far as is known, no tectonic activity took place in the Rough Creek graben during the Silurian Period . Normal faulting took place along both the northern and south- ern boundaries of the Rough Creek graben during the Devonian Period. Displacement of the eastern part of the Rough Creek fault system, in Grayson and Ohio Counties, Kentucky, was interpreted from subsurface mapping by Freeman (1951). The Clear Creek Formation (Emsian) is present south of the fault system and absent to the north. The Jeffersonville Limestone (Eifelian), Sellersburg Limestone (Givetian), and New Albany Shale (Devonian-Mississippian) all thin or pinch out north of the fault system also. From these relationships, Freeman (1951) suggested a recurrent uplift of the crus- tal block north of the Rough Creek fault system from late Early Devonian through Late Devonian time. An isopach map of the New Albany Shale in western Kentucky (Schwalb and Potter, 1978) shows a greater thickness of that unit south of the Rough Creek-Shaw- neetown fault system and north of the Pennyrile fault system. The New Albany Shale is 10 to 100 feet (3 to 30 m) thicker on the downthrown sides of faults than on the upthrown sides. The total thickness changes of De- vonian rocks across the Rough Creek-Shawneetown fault system in Grayson County, Kentucky, are as great as 800 feet (245 m) (Freeman, 1951, pi. 21). CARBONIFEROUS Paleogeomorphic features and thickness and sedimen- tation patterns detected from outcrop and subsurface data support interpretations of tectonism concurrent with Chesterian (Late Mississippian) through Des- moinesian (Middle Pennsylvanian) sedimentation in the Rough Creek graben. Basal Pennsylvanian rocks fill paleovalleys that are eroded into Chesterian strata. Fea- tures that have been cited in support of Carboniferous tectonism include rectangular drainage patterns, paleo- valleys parallel or coincident with fault zones, abrupt diversions of drainage, and abnormally deep incisions within faulted areas (Davis et al., 1974; Greb, 1989a, 1989b). Thickness and lithofacies patterns of the Caseyville Formation (Morrowan, Lower Pennsylvanian) appear to be fault-controlled in parts of western Kentucky (Greb, 1989a) and southern Illinois (Weibel et al., 1991). Large paleoslumps and other features of soft-sediment deformational structures are particularly numerous near surface faults and may have been triggered by earth movements. Such structures have been observed in the Caseyville Formation and the overlying Tradewater and Carbondale Formations (Morrowan through Des- moinesian, Lower and Middle Pennsylvanian) (Potter, 1957; Nelson and Lumm, 1987; Greb, 1989a, 1989b; Lummetal., 1991). POST-PENNSYLVAN1AN Exposed structures in the Rough Creek graben are pre- dominantly products of post-Pennsylvanian tectonism that reactivated rift-boundary faults. According to Nel- son and Lumm (1987), an early episode of reverse fault- ing elevated crustal blocks south of the Rough Creek- Shawneetown fault system and southeast of the Lusk Creek fault zone. This faulting probably took place un- der north-south to northwest-southeast compression as- sociated with orogenesis in the southern Appalachian region during the Permian Period. Ultramafic dikes in the western part of the Rough Creek graben have been radiometrically dated as Early Permian (Zartman et al., 1967), and they are emplaced along north-south to northwest-southeast tension fractures that developed under the same stress regime. Subsequently, during early Mesozoic time, the Rough Creek graben was sub- jected to northwest-southeast extension, which induced normal faulting throughout the graben. Hence, the pre- viously uplifted blocks south of the Rough Creek and Lusk Creek zones were lowered. This episode of normal faulting was largely com- pleted before Upper Cretaceous and Tertiary sediments were deposited in the Mississippi embayment. Minor displacements of Cretaceous strata at the margin of the embayment in western Kentucky have been interpreted as the final adjustments along faults (Rhoades and Mis- tier, 1941). The area is not seismically active today and no evidence of Quaternary tectonic activity has been documented. REGIONAL FAULT SYSTEMS ROUGH CREEK-SHAWNEETOWN FAULT SYSTEM The Rough Creek-Shawneetown fault system ranges in width from less than 1 mile to 5 miles (1 to 8 km) and is composed of faults that form a braided pattern in plan view. The system strikes about N 70° W near its eastern terminus in Grayson County, Kentucky, and extends to the west to Saline County, Illinois. Near its western terminus, the fault system abruptly bends to a heading of S 30° W, and continues about 12 miles (19 km) to its junction with the Lusk Creek fault zone. The total length of the system is about 140 miles (225 km). The master fault of the system is at or near the north- ern border of the Rough Creek fault system. This fault is the upward continuation of the major rift-boundary fault that evolved during Cambrian time. The fault is geometrically a normal fault below the Knox Group and a reverse fault in the Knox and younger strata. These conclusions have been made on the basis of numerous seismic reflection sections and at least 16 boreholes that penetrate the master fault (Smith and Palmer, 1974, 1981; Nelson and Lumm, 1987; Bertagne and Leising, 1991). The dip of the master fault varies from 60° to 75° S, except near Morganfield, Kentucky, where the dip is locally as gentle as 25° S (Smith and Palmer, 1974, 1981). The greatest stratigraphic displacement is about 3,500 feet (1,070 m), near the western end of the fault system in eastern Saline County, Illinois. Strata north of the master fault, in the footwall, gen- erally are horizontal or gently dipping and few faults are present (fig. 3) (Smith and Palmer, 1974, 1981; Nelson and Lumm, 1987). In contrast, the hanging wall of the master fault is intensely deformed. Typically, the hang- ing wall is either a faulted arch as in figure 3 or a series of imbricated fault slices that dip steeply southward. The fault slice at the Horseshoe Quarry (Stop 4) is an example of the latter. Most hanging-wall faults are high- angle normal faults; a few are reverse faults (Smith and Palmer, 1974, 1981; Nelson and Lumm, 1987). The Eagle Valley/Moorman syncline is an asymmet- rical structure located south of the master fault. Strata at the axis of the syncline are at the same elevation or lower than their counterparts north of the fault system. Hence, the net displacement across the Rough Creek-Shawnee- town fault system is small, compared with the great displacement among fault slices within the system. Of particular importance for deducing the overall structure and chronology of the Rough Creek-Shawnee- town fault system are the imbricated fault slices within the fault system. In Saline County, Illinois, the Horse- shoe upheaval (Horseshoe Quarry; Stop 4 on the field trip) exposes Lower Mississippian and Upper Devonian rocks that are juxtaposed with Pennsylvanian rocks to the north for a stratigraphic offset of 3,500 feet (1,070 m) (Nelson and Lumm, 1987). One mile (1.6 km) west of the upheaval, an oil test hole penetrated the master fault, passing from Lower Devonian rocks in the hanging wall to Pennsylvanian rocks in the footwall. The indicated throw is approximately 3,500 feet (1,070 m), and the average dip of the fault from the ground surface to the wellbore is about 70° S. A block of Lower Mississippian Fort Payne Formation is bounded on both sides by Chesterian rocks along the master fault at the Morgan- field South oil field in Union County, Kentucky (Smith and Palmer, 1974, 1981). Conversely, younger strata are downdropped and preserved in other fault slices. One such slice located a few miles southeast of Morganfield contains the only reported Permian rocks in the Illinois basin (Kehn et al., 1982). We propose that these structures were produced by two episodes of post-Pennsylvanian dip-slip faulting. The first episode involved compression and produced reverse faults, which raised the southern block. The second event was extensional and produced normal faults, whereby the southern block was lowered to nearly its original position. Narrow horst blocks such as the Horseshoe upheaval are interpreted as remnants of the hanging wall that were severed and left behind during the episode of normal faulting. These interpreta- tions were first presented by Smith and Palmer (1974), and later amplified by Nelson and Lumm (1987) and Bertagne and Leising (1991). The concept of early com- pression and late extension (or "relaxation"), however, was suggested much earlier by J. M. Weller (1940, p. 49-51) and S. Weller and Sutton (1951). An alternative interpretation proposed by earlier workers is that the Rough Creek fault system is a prod- uct of predominantly strike-slip movement (Clark and Royds, 1948; Heyl, 1972; Viele, 1983). These authors cited the braided pattern of high-angle faults, the incon- sistent direction of net displacement, and an anticlinal upthrust pattern reminiscent of "flower structures" in support of strike-slip. Countervailing evidence, how- ever, includes (1) absence of en echelon foldbelts or en echelon fault zones, (2) pronounced asymmetry of the N Pt Pennsylvanian Tradewater Formation Pcv Pennsylvanian Caseyville Formation Mm Mississippian Menard Limestone Figure 4 Illustrated profile of the east side of the Green River Parkway at Stop 1. This is a simplified version of a diagram by Krausse etal. (1979). fault zone in cross section (Smith and Palmer, 1981), (3) drag folds that are horizontal and parallel with the major faults, (4) the lack of lateral offset of a 60° bend near the western end of the fault system, and, most compelling, (5) the lack of lateral offset of pre-Pennsylvanian paleo- channels that cross the fault system (Nelson and Lumm, 1987). The evidence does not preclude oblique-slip dis- placement, but it indicates that the predominant move- ments were dip-slip. LUSK CREEK FAULT ZONE The structure of the Lusk Creek fault zone is similar to that of the Rough Creek fault zone. The Lusk Creek fault zone is mostly composed of normal faults and some reverse faults in a zone as much as 0.6 mile (1 km) wide. Drag folds and slickensides indicate movement was dip-slip. The net displacement is less than that of the Rough Creek fault zone and is down to the southeast. At some locations, however, narrow horsts analogous to the Horseshoe upheaval are present within the fault zone. The composite structure suggests two episodes of post-Pennsylvanian deformation. The first episode was compressional and produced reverse faults that ele- vated the southeast block. Subsequently, extension pro- duced normal faults and lowered the southeast block. PENNYRILE FAULT SYSTEM The Pennyrile fault system is predominantly composed of high-angle normal faults having overall displacement down to the north. Reverse and strike-slip faults have been reported by Jillson (1958), Rose (1963), and Higgins (1986), but these faults are small and few details have been published. The system trends east to west along most of its length; individual faults commonly strike east-northeast and are en echelon. Stratigraphic offsets on individual faults range from a few inches to 800 feet (245 m). In a railroad cut and highway cut north of Crofton, Christian County, Kentucky (Stops 7 and 8), the master fault of the Pennyrile fault system is located at the southern margin of the fault system. A steep monocline north of the master fault is interpreted as a fault-propa- gation fold. Along the flank of the monocline and imme- diately to the north, numerous subparallel high-angle normal faults of small displacement outline horsts and grabens. We interpret some of these faults to have been subsequently rotated by drape folding. Reverse faults with minor offsets may reflect localized compression within the fault zone. There is no evidence for large- scale reverse or strike-slip displacement (Lumm et al., 1991). Several miles north and south of the Pennyrile fault system are parallel sets of normal faults. Palmer (1969) described 21 striated surfaces of normal faults exposed in coal mines about 10 miles (16 km) north of Crofton. The fault surfaces dip from 54° to 90°, and the slicken- sides indicate only vertical (dip-slip) movement. Palmer (1969, p. C76) stated, "The uniformity and smoothness of the grooves and the absence of separate superim- posed layers of slickensides suggest the likelihood of only one generation of movement." In summary, post-Pennsylvanian displacement of the Pennyrile and the adjacent, parallel fault systems were produced by crustal extension. Dip-slip normal faults that originated during Cambrian rifting were reacti- vated under crustal extension. The en echelon pattern of faults suggests that the extensional stress axis was ori- ented north-northwest to south-southeast, not quite per- pendicular to the east-trending Cambrian faults at depth. 30 m no vertical exaggeration DISCUSSION The ancestral Rough Creek-Shwneetown, Lusk Creek, and Pennyrile fault systems originated as normal faults during Cambrian rifting, and the region experienced additional normal movement during Devonian and Carboniferous time. The post-Pennsylvanian histories of the fault systems diverge. The Rough Creek and Lusk Creek fault systems experienced first reverse, then nor- mal displacements, whereas the Pennyrile fault system experienced recurrent normal faulting and only local- ized reverse faulting. Kolata and Nelson (1991a) attributed reverse faulting at the northern margin of the Rough Creek graben to compressional stress associated with the Alleghenian orogeny in Late Pennsylvanian and Permian time. They related extensional (normal) faulting in the region to the breakup of Pangea in Triassic and Jurassic time. No direct evidence exists in the Rough Creek graben to confirm the timing of either event. The question arises, why did major compression affect only the northern boundary faults? The southern (Pennyrile) boundary faults not only parallel the northern, but are closer to the presumed southern Appalachian source of compres- sion. Future crustal models of faulting in this and other interior cratonic basins must take into account these apparent discrepancies. FIELD-TRIP STOPS STOP1 Green River Parkway, milepost 53, lat 37°31'30"N, long 86°55'10"W, Pleasant Ridge quadrangle, Ohio County, Kentucky (figs. 4 and 5). This roadcut is the best available exposure of the Rough Creek-Shawneetown fault system, and it has been featured on previous field trips. Our interpreta- tions differ from those presented by Krausse et al. (1979), Higgins (1986), Cowan and Williams (1988), and others. The Rough Creek fault system is more than 3 miles (5 km) wide in central Ohio County. The zone of large stratigraphic displacements (greater than 400 feet (120 m)) is approximately 1 mile (1.2 km) wide in this roadcut (Goudarzi and Smith, 1968). The Parkway roadcut is at the southern edge of the zone of large faults, approxi- mately 4,000 to 5,000 feet (1,220 to 1,525 m) south of the master fault. The roadcut trends north to south, approxi- mately perpendicular to the major structures. In simplest terms, the structure in the Parkway road- cut is an asymmetrical faulted anticline. The Menard Limestone (Mississippian) is at the core of the fold, and is unconformably overlain by the Caseyville and Trade- water Formations (Pennsylvanian) (fig. 4). The anticline has a gentle north limb and a steep, locally overturned south limb. Dips on the north limb become steeper toward the axial plane of the fold. The axial plane strikes N 75° W and dips about 60° N. The fold axis plunges gently eastward. Numerous small faults displace Pennsylvanian rocks on the north limb of the anticline. Most of these faults are low-angle normal faults that dip south; however, several small offset reverse faults also are present. Near the north end of the roadcut on the east side of Parkway is a low-angle fault that has a vertical offset of about 15 feet (4.5 m). The net displacement is normal, but shales in the footwall are strongly contorted, indicating an element of compression. (Digging may be necessary to expose the contorted shales.) The structure at the core of the anticline is complex. Abrupt changes in the thicknesses of some strata, par- ticularly the shales, reflect ductile deformation and faulting subparallel to the bedding. On the east side of N STOP 1 ROADCUT Mbc IP A Mv. Mbc^ P Pennsylvanian strata Mv Mississippian Vienna Limestone Mbc Mississippian Beach Creek Limestone Member of Golconda Formation Figure 5 Interpretive diagram showing relationship of structures at Stop 1 to the master fault of the Rough Creek fault system. The main fault at Stop 1 is interpreted as a backthrust in the hanging wall of the south-dipping master fault. The diagram is based in part on the geologic map by Goudarzi and Smith (1968). N slickensides (Pt Pennsylvanian Tradewater Formation Pcv Pennsylvanian Caseyville Formation Figure 6 Illustrated profile of the east side of the Hoover Hill roadcut, Stop 2. Parkway, faults subparallel to the bedding are present on the south limb of the anticline, where basal Pennsyl- vanian coals are repeated. Many of the smaller structural details, omitted from figure 4, are illustrated in figure KY-18 of Krausse et al. (1979). Details omitted include tight to isoclinal folds that have horizontal axes and vertically plunging slickensides, both of which suggest dominantly dip-slip displacements on faults. On the west side of the Parkway, north of the crest of the anticline, is a fault that may have undergone a reversal of displacement. Beds of gray shale dip very steeply northward, indicating a downward displace- ment of the northern block, yet the limestone beds in the central block are higher than correlative beds south of the fault zone. We postulate that the initial episode of reverse faulting, north side up, was followed by normal faulting with the north side downthrown. A principal fault in the roadcuts (main fault in fig. 4), is located about 100 feet (30 m) south of the anticlinal crest. This fault strikes east-west and tips steeply north- ward. Krausse et al. (1979) interpreted it as a normal fault; however, both the stratigraphic relationships and small drag folds present indicate that the north side is upthrown, establishing this as a reverse fault. We interpret the main fault as a backthrust that may intersect the master fault at depth (fig. 5). The anticline north of the main fault may be a fault-propagation fold. The concave-upward profile of the north limb of the anticline may reflect subsidence of the hanging wall under a later episode of extension. The numerous small- offset normal faults may be products of later extension also. STOP 2 Hoover Hill roadcut on U.S. Rte. 231, 7 miles north of Hartford, Kentucky, lat 37°30'0"N, long 86°58'25"W, Pleasant Ridge quadrangle, Ohio County, Kentucky (fig. 6). Two large-offset faults and several small faults dis- place Pennsylvanian strata near the northern edge of the Rough Creek fault zone at this stop. Goudarzi and Smith (1968) interpreted the unexposed master fault to be near the base of the hill about 500 feet (150 m) north of the roadcut. The exposed structures suggest reversals of displacement; horizontal slickensides indicate an ele- ment of strike-slip faulting. The principal fault in this roadcut strikes N 70° E and is vertical (fig. 6). Sandstone breccia and faint vertical striations are visible on the fault plane east of the high- way. North of the fault is thick-bedded, light gray, fine- grained quartzose sandstone of the basal Pennsylvanian Caseyville Formation. South of the fault is shale, a thin coal bed, and brown, micaceous argillaceous sandstone characteristic of the younger Tradewater Formation. Hence, the stratigraphic displacement is down to the south, although the tight drag fold in the shale and coal south of the fault indicates downward movement of the northern block. The syncline suggests uplift of the northern block, with the drag fold being a product of the second movement. Near the southern end of the roadcut, another poorly exposed large north-dipping fault displaces Tradewater Formation sandstones (fig. 6). It is interpreted as a high- angle normal fault. Striations on fractures on the steeply dipping sandstone immediately south of this fault indi- cate predominantly dip-slip displacement. Numerous small high-angle normal faults offset Caseyville sandstone north of the main fault. Some of these faults bear vertical (dip-slip) slickensides. Near the northern end of the roadcut, folds associated with two faults suggest that these faults have undergone reversals of displacement. main fault dip-slip slickensides slickensides ^ slickensides 50 ft _l 10 m Horizontally striated fractures occur on both sides of the road north and south of the main fault. The fracture surfaces are vertical and strike from due north to N 40° W, which is nearly perpendicular to the main fault and to the regional strike of the Rough Creek fault zone. The strike-slip displacement along these fractures probably is small. The main fault appears to be offset several feet in a left-lateral sense across the highway. The horizontal striations are considered to reflect minor adjustments within a fault zone dominated by dip-slip motion. STOP 3 Sebree Interchange of Pennyrile Parkway, lat 37° 36'30"N, long 87°30'00"W / border of Beech Grove and Sebree quadrangles, Webster County, Kentucky (figs. 1 and 7). The focus at this site is a paleoslump in clastic rocks assigned to the middle part of the Tradewater Formation (Pennsylvanian). The site is approximately 1,300 feet (400 m) south of the master fault of the Rough Creek fault zone (Hansen, 1975). This site is an excellent example of a rotational slump block. A sequence of shale, siltstone, and sandstone is displaced downward along a listric normal fault that dips west (fig. 7). Within view to the west, this fault merges with bedding at or just above a thin coal bed 10 to 15 feet (3 to 4.5 m) above the base of the exposure. The curved glide plane controlled the eastward rotation of the heel of the slump block. After the slump event, the upturned beds were truncated and subsequently overlain unconformably by horizontally bedded, cross- Figure 7 Illustration of paleo- slump at Sebree interchange, Stop 3. View is oblique to exposure, looking southwest. Traced from a photo- graph by April Cowan. bedded sandstone. This structure clearly formed during Tradewater deposition, before the sediments were lithi- fied. Slumps of this type commonly form in modern del- tas, for example, the Mississippi Delta (Coleman, 1981). A tectonic mechanism is not required to produce them. Large earthquakes such as the 1811-1812 New Madrid tremors, however, can trigger unusually large numbers of rotational slumps (Jibson and Keefer, 1988). The den- sity of documented Pennsylvanian paleoslumps is markedly greater along the Rough Creek-Shawneetown fault system than elsewhere in the Illinois basin. Coal mining and coal-test drilling have revealed numerous examples of paleoslumps along the fault zone in both Illinois and Kentucky (Nelson and Lumm, 1987). In one such area in Gallatin County, Illinois, dozens of paleo- slumps severely hindered a strip-mining operation and contributed to the premature closing of the mine. We propose that the Sebree paleoslump may have been triggered by earthquake activity along the adjacent Rough Creek fault zone. STOP 4 Horseshoe Quarry, lat37°42'05"N, long 88°22'55"W (SW NW NE, Sec 36, T9S, R7E), Rudement quadrangle, Saline County, Illinois (figs. 1, 8, and 9). This site, commonly called the Horseshoe upheaval, reveals the most extreme example of a "perched" fault slice in the Rough Creek-Shawneetown fault system. Steeply dipping beds of the Fort Payne Formation (Osagean-lower Valmeyeran) and New Albany Shale 10 (Devonian-Mississippian) are exposed in the aban- doned quarry (fig. 8). Relative to adjacent Pennsylva- nian strata, these rocks are displaced upward as much as 3,500 feet (1,070 m). Butts (1925) was the first to identify Chattanooga shale and Osage limestone from outcrops at the Horse- shoe Quarry. Nelson and Lumm (1986) confirmed the identity of these rocks as the New Albany Shale and Fort Payne Formation of current terminology. Outcrops of vertically dipping black, fissile, phosphatic New Albany Shale are confined to the northwest edge of the quarry and are situated on private property. The rock in the quarry is dark gray, fine-grained, highly siliceous lime- stone of the Fort Payne Formation. These beds strike east-west and dip steeply southward. A north-south cross section (fig. 9) shows the struc- tural features of the Horseshoe Quarry within the fault zone. The fault slice is approximately 1,000 feet (300 m) south of the master fault. North of the master fault, coal-bearing Middle Pennsylvanian strata dip gently northward. The Springfield Coal Member (Carbondale Formation) has been contour strip-mined in the hills located about 2 miles (3.2 km) north of the quarry. South of the quarry, the escarpment of Cave Hill is composed of resistant sandstone of the Caseyville Formation (Lower Pennsylvanian). This unit dips approximately 20° southward into the Eagle Valley syncline. The Car- bondale Formation crops out near the axis of the syn- cline about 2 miles (3.2 km) south of the Horseshoe Quarry Hence, displacements within the fault zone are great, but the net stratigraphic displacement across the entire fault zone is minor. We have explained the Horseshoe upheaval as the product of two episodes of dip-slip movement (Nelson and Lumm, 1987). First, the southern crustal block (hanging wall) of the master fault was uplifted at least 3,500 feet (1,070 m) under compression. Second, under extension, the hanging wall was lowered back to nearly its original position. The Horseshoe slice is a remnant of the hanging wall that was severed during the second episode of (normal) faulting. Steep southward dips of bedding reflect this second episode of normal faulting. Fischer (1987) measured the attitudes of folds, kink bands, and fractures at Horseshoe Quarry. He con- cluded that the rocks were subjected to northeast-south- west compression, which induced oblique left-lateral reverse slip. Fischer's conclusion is not compatible with our tectonic model. We postulate that the Horseshoe fault slice was rotated within the fault zone, perhaps during a reversal in the direction of displacement. Figure 8 Photograph of Horseshoe Quarry, looking east. Steeply dipping beds are siliceous limestone of Fort Payne Formation. This photo was taken in 1960 when the quarry was much less overgrown by vegetation. Photo by D. L. Reinertsen. 11 2000 1000 -0 1000 2000 Pcb Carbondale Formation Pt Tradewater Formation Pcv Caseyville Formation M Mississippian D Devonian 1 km Figure 9 Interpretive cross section at Horseshoe Quarry (Stop 4) and Horseshoe Gap (Stop 4A) (fig. 3 of Nelson and Marshak, 1990). Rotated minor structures in the fault slice would not represent original regional stress orientation. OPTIONAL STOP 4A Horseshoe Gap roadcut, lat 37°41'25"N, long 88°22'31"W (NE SE SE, Sec. 36, T9S, R7E), Rudement quadrangle, Saline County, Illinois (fig. 9). This small roadcut is located near the southern edge of the Rough Creek-Shawneetown fault system (fig. 9). At this site, faulted and folded sandstone and shale of the Tradewater or Carbondale Formations (Middle Pennsylvanian) are present. All of the faults in the road- cut appear to be normal faults. Drag folds have subhori- zontal axes and are consistent with normal faulting. Slickensides (rare) indicate predominantly dip-slip mo- tion. South-dipping faults near the middle of the expo- sure dip at low angles, but offset the bedding at steep angles. These faults may have formed during an early stage of deformation and later were rotated to their present attitudes. These structures signify north-south extension. They may have developed either under a regional extensional stress field, or under a local extensional stress field developed along the crest of an anticlinal drag fold formed under regional compression. Their relationship to larger structures is shown in figure 9. STOP 5 Clay Diggings, lat 37°27'50"N, long 88°32'48 M W, (NW NE SE, Sec. 16, T12S, R6E), Waltersburg quadrangle, Pope County, Illinois (figs. 1 and 10). Abandoned prospect pits and a quarry in the Lusk Creek fault zone reveal a narrow upthrown fault slice analogous to the Horseshoe upheaval. The slice is inter- preted as a product of an early episode of reverse fault- ing followed by later, larger normal displacements along the same faults. The name "Clay Diggings" refers to halloysite clay that was mined prior to 1866 along the northwest side of the fault slice (Lamar, 1942). Fluorspar, galena, and sphalerite have also been mined from shallow shafts at this site (Bain, 1905; Weller et al., 1952), and limestone was quarried during the 1930s by the Civilian Conser- vation Corps. The land is presently managed by the U.S. Forest Service. The light gray bioclastic and oolitic limestone that forms the quarry face is the upper Valmeyeran (Missis- sippian) Ste. Genevieve Limestone. Micritic limestone with abundant chert nodules may belong to the under- lying St. Louis Limestone (Valmeyeran). Although the bedding is obscure, these rocks dip steeply southeast and are intensively fractured (fig. 10). Calcite is the primary vein mineral, but small amounts of fluorite and metallic sulfides are present. Some fractures bear slick- ensides that have a variety of orientations. Geologic mapping by Weibel et al. (1991) and inter- pretation of core drilling by Robert Diffenbach (personal communication, 1985) indicate that the Ste. Genevieve- St. Louis (?) Limestones form a narrow horst block be- tween two faults that strike northeast and dip steeply southeast (fig. 10). The northwestern fault is a reverse fault, with upper Chesterian and Caseyville Formation strata in the footwall. The southeastern fault is a normal fault that juxtaposes Middle Pennsylvanian Tradewater Formation in the hanging wall with Ste. Genevieve and St. Louis in the footwall. Steeply dipping beds of Trade- water sandstone are present in the wooded area just 12 beyond the southeastern part of the quarry. In the central horst, the Ste. Genevieve Limestone is upthrown about 800 feet (245 m) relative to the Chesterian rocks and 1 ,500 feet (455 m) relative to the Tradewater Formation. We postulate that an initial episode of reverse faulting took place along the fault that borders the northwest side of the limestone quarry. This fault is marked by a zone of nearly vertically dipping, brightly colored, hy- drothermally altered rock (gossan). A later event of nor- mal displacement, greater in magnitude than the reverse displacement, occurred on the fault southeast of the quarry. This fault is marked by shattered silicified sand- stone in a prospect pit at the eastern edge of the quarry. The strata were sheared into a drag fold and were later rotated along the late-stage normal fault. STOP 6 Dixon Springs west roadcut, Illinois Rte. 146, lat 37°23'02"N, long 88°40'55"W (SW NW SE, Sec. 17, T13S, R5E), Glendale quadrangle, Pope County, Illinois (fig- 1). The roadcut exposes small faults in the northwestern part of the Lusk Creek fault zone. The faults include two low-angle thrust faults and an apparent scissors fault.The sandstone and shale in this roadcut have been mapped as the middle Chesterian Tar Springs Forma- tion (Devera, 1991). The site is about 0.3 mile (0.5 km) northwest of the main fault, which juxtaposes the Lower Pennsylvanian Caseyville Formation with the Tar Sp- rings. On both sides of the roadcut are two low-angle thrust faults that dip west and have about 2 and 5 feet (0.6 and 1.5 m) of apparent net slip, respectively. To the east is a high-angle fault that strikes N 40° E. The dip and direction of throw of this fault appear to change from one side of the highway to the other. Thus, this feature could be categorized as a scissors fault. The thrust faults signify horizontal compression. The scissors fault may reflect (1) strike-slip displacement, (2) reversals of displacement, (3) oblique rotation of a fault block, or (4) a combination of the above. OPTIONAL STOP 6A Dixon Springs east roadcut, Illinois Rte. 146, lat 37°23' 00"N, long 88°40'27"W, (SW NW SW, Sec. 16, T13S, R5E), Glendale quadrangle, Pope County, Illinois. Steeply dipping sandstone beds of the Caseyville Formation (Lower Pennsylvanian) are exposed in a fault block on the downthrown side of the major fault in the Lusk Creek fault zone. The Caseyville strata are horizon- tal 500 feet (150 m) southeast of the roadcut in Dixon Springs State Park. Just west of the roadcut (near the junction of Illinois Rtes. 145 and 146), small outcrops of fractured Tar Springs Sandstone are on the upthrown side of the major fault. The stratigraphic displacement is approximately 500 feet (150 m) down to the southeast. Features to observe in this roadcut include slicken- sided bedding planes that may be products of flexural slip. Other faults offset the bedding at low angles. Frac- tures are also present that are perpendicular to bedding and bear striations parallel to bedding. The fractures are reminiscent of the horizontally striated fractures at the Hoover Hill roadcut (Stop 2). Such fractures comply with Beckwith's (1941) definition of trace-slip faults. STOP 7 CSX Railroad cut 1 mile (1.6 km) north of Crofton, Ken- tucky, lat 37°04'00"N, long 87°29T5"W, Crofton quad- rangle, Christian County, Kentucky (figs. 1 and 11). NW quarry SE Caseyville , gossan Figure 10 Cross section of Lusk Creek fault zone at Clay Diggings (Stop 5). 13 N % \ (Pt Pennsylvanian Tradewater Formation Pcv Pennsylvanian Caseyville Formation Mk Mississippian Kinkaid Limestone Md Mississippian Degonia Formation Mm Mississippian Menard Limestone A-G Features discussed in text Figure 11 Illustrated profile of the east side of the CSX Railroad cut north of Crofton, Kentucky (Stop 7). Extensively modified from a scale drawing by Jillson (1958). This railroad cut contains possibly the finest single exposure of faults in the Illinois basin. More than 400 feet (120 m) of Pennsylvanian strata, 150 feet (45 m) of Mis- sissippian rocks and nearly the entire width of the Pen- nyrile fault system are exposed in a continuous cut more than 1 mile (1.6 km) long. The structurally complex southern margin of the fault zone will be examined at this stop. Farther north, a narrow zone of south-dipping normal faults displaces gently dipping Pennsylvanian strata. Hence, the south-dipping faults and the north- dipping southern boundary faults outline an asymmet- rical graben. The geology of the Crofton 7.5-minute quadrangle was mapped by Kehn (1977), and a geologic description and interpretation of the railroad cut was published by Jillson (1958). Figure 11 was modified from a profile that Jillson made when the cut was fresher than at the pres- ent. Our interpretations of the structure and stratigra- phy differ from those of Jillson (1958) and Kehn (1977). The Pennyrile fault system north of Crofton is about 1.5 miles (2.4 km) wide and is composed mostly of normal faults that outline horsts and grabens. The great- est displacements are at the southern margin of the zone. The overall offset is down to the north (Kehn, 1977). The southern boundary fault, labelled master fault in figure 11, juxtaposes the middle Pope Group (Chesterian) Menard Limestone on the south with the upper Pope Group (Chesterian) Degonia Formation, which dips steeply north. North of the master fault across a distance of more than 1,000 feet (300 m), the dips gradually decrease from nearly vertical to less than 10° north. Numerous faults, which strike subparallel to the master fault and dip at a variety of attitudes, offset the tilted Mississippian and Pennsylvanian rocks into a series of narrow horsts and grabens. Adjacent to and north of the master fault is a fault slice (A in fig. 11) that contains Degonia Formation and Kinkaid Limestone, disconformably overlain by the Lower Pennsylvanian Caseyville Formation. A poorly exposed nearly vertical fault separates slice A from slice B, which contains nearly vertical Kinkaid Limestone. Slice B in turn is separated by a north-dipping fault from another block of Caseyville farther to the north. The faults that bound and subdivide slices A and B are parallel to bedding or offset the bedding at low angles. North of slice B, quartzose sandstone of the Casey- ville Formation is overlain by thick shale of the Trade- water Formation on the east side of the railroad cut. A lozenge-shaped block of sandstone (C in fig. 11) is pres- ent within the shale near the top of the cut. A low-angle north-dipping fault underlies the sandstone block and offsets the shale. The direction of displacement on this fault is unclear, although small-scale drag folds suggest that the hanging wall moved upward, making this geo- metrically a reverse fault. Jillson (1958) described the fault as a thrust fault and interpreted it as a product of compression. Numerous small-scale normal faults asso- ciated with the thrust imply extension, however, not compression. In Lumm et al. (1991), we suggested that this fault may have formed as a low-angle listric normal 14 MASTER FAULT * / Pcv ° 4 * i 100 20 — r~ 40 no vertical exaggeration 200 ft 60 m fault, and the sandstone lens above it may be part of a rotational slump block similar to the one viewed at the Sebree Interchange (Stop 3). The paleoslump — possibly triggered by tectonic movements along the Pennyrile fault zone — may have formed while the sediments were horizontal and unlithified. Subsequent rotation of the strata to their present attitude gives the geometric ori- entation of a thrust fault. Another listric fault (D in fig. 11) is directly below the C block. This fault, presently horizontal, would have had a dip of about 45° S before the strata were tilted. Sandstone of the Caseyville Formation is displaced about 25 feet (8 m), the upper block having moved southward. A normal fault (E in fig. 11) dips 40° Sand has at least 85 feet (26 m) of throw. The fault may have been a high-angle fault that has subsequently been rotated. A reverse fault (F in fig. 11) has a tight drag fold in the footwall. Again, this may be a rotated, high-angle nor- mal fault. Several small faults are subparallel to bedding near fault F, and one of the faults offsets fault F. The northernmost feature we will examine is a south- dipping normal fault (G in fig. 11) that has about 60 feet (18 m) of throw. In the west side of the railroad cut, two small angular unconformities are present (digging may be necessary) in the footwall of fault G. The uppermost unconformity is within a dark gray shale and is charac- terized by a layer of prolate siderite cobbles. The lower unconformity is at the base of a thin coal. Although a nontectonic origin is possible, we postulated (Lumm et al., 1991) that these unconformities reflect small dis- placements of the Pennyrile fault system during Trade- water sedimentation. In summary, the Crofton railroad cut exhibits a large faulted fold in the footwall of the high-angle normal master fault. The cross-sectional profile is very similar to that simulated in laboratory experiments by Withjack et al. (1990). Those experiments involved horizontal clay layers (representing sedimentary strata) placed over a basement of wooden blocks having pre-cut normal faults. Incremental displacements along the pre-cut faults produced monoclinal folds in the clay as the faults propagated upward. Such folds can be called drape folds, forced folds, or fault-propagation folds. In the railroad cut, as in the clay models, folding and faulting is largely confined to the footwall of the master fault. As discussed in Lumm et al. (1991), the Pennyrile faults probably evolved during late Precambrian to Cambrian rifting and were reactivated during Early and Middle Pennsylvanian time. Early to Middle Pennsylvanian displacements at depth gently folded the surface or near-surface strata, perhaps inducing paleoslumps and minor unconformities. With continued displacement af- ter Pennsylvanian rocks were lithified, the limb of the fold became steeper and normal faults propagated toward the surface. Faults that formed during the early stages of deformation were subsequently rotated as the fold steepened. Finally, the upper limb of the fold be- came nearly vertical, and widespread shearing took place parallel to the strata adjacent to the master fault. 15 N Antithetic normal faults IPcv Thrust fault L L - ^~-~-^- r ~-^ coa - Pt Pennsylvanian Tradewater Formation IPcv Pennsylvanian Caseyville Formation Mp Mississippian Palestine Sandstone Mm Mississippian Menard Limestone * Figure 12 Illustrated profile of the roadcuts on the east side of the Pennyrile Parkway north of Crofton, Kentucky. Projected down- ward, the antithetic normal faults would intersect the main fault about 1,350 feet (410 m) below the roadway in Mississippian strata. STOP 8 Pennyrile Parkway, milepost 24, lat 37°04'00" N, long 87°28'00" W, Crofton quadrangle, Christian County, Kentucky (figs. 1 and 12). The tandem of roadcuts on the Pennyrile Parkway are located about 1.2 miles (1.9 km) east of the CSX Railroad cut. Similar to the railroad cut, the Parkway roadcuts expose the southern part of the Pennyrile fault system. As shown in the profile (fig. 12), the structure is consid- erably simpler than that in the railroad cut. The master fault is poorly exposed and is located near the south end of the southern roadcut. This fault is a normal fault and dips about 60° N. Shale and sandstone correlated with the Pennsylvanian Tradewater Forma- tion on the north are juxtaposed with the Mississippian Menard Limestone and Palestine Sandstone on the south. North of the master fault the Tradewater strata are folded, but less tightly than in the railroad cut. The bedding is nearly horizontal 600 feet (185 m) north of the master fault. Two parallel faults that dip south are near the north end of the northern roadcut (north of milepost 24). These antithetic faults and the master fault outline a graben. Sandstone of the Caseyville Formation is exposed north of the graben and in the narrow slice between the par- allel faults. Two small compressional structures are exposed in the roadcuts. Just south of milepost 24 is an asymmetric anticline that is offset by a thrust fault. The fault plane dips about 25° N. The shale and thin coal bed in the footwall have been overturned. The other compres- sional structure is a high-angle fault about 900 feet (270 m) south of the thrust fault. Stratigraphic evidence indi- cates that the hanging wall is downthrown (normal faulting); however, reverse drag folds on both sides of the fault indicate that the hanging wall moved upward 16 Fault with reversed displacement MASTER FAULT 150 _L 1 50 no vertical exaggeration 300 ft _l 100 m \ / \ / \ / \ / / (reverse faulting). We propose that this structure origi- nated as a normal fault, and later underwent a lesser amount of reverse displacement, which folded the duc- tile shales and siltstones. An episode of regional compression in the history of the Pennyrile fault system might be hypothesized. This interpretation is problematic to us because the compres- sive structures here apparently were a late event, whereas the faults on the north side of the Rough Creek graben probably experienced early compression, fol- lowed by late extension. Moreover, the compressional structures in the Pennyrile roadcut are one to two orders of magnitude smaller than the major extensional fea- tures (normal faults). No other large compressional structures have been documented in the Pennyrile fault system. The thrust and reverse faults noted in the Pen- nyrile roadcuts may be isolated structures that evolved from movement along irregular fault surfaces or from the internal adjustments of fault blocks during incre- mental movement. Similar small reverse faults have been documented in the hanging walls of large normal faults in parts of the Colorado Plateau and are attributed to localized compression (Brumbaugh, 1984). ACKNOWLEDGMENTS We thank Michael L. Sargent and Janis D. Treworgy (ISGS) and David A. Williamson (Kentucky Geological Survey) who critically reviewed and offered sugges- tions for improving early drafts of the manuscript. Robert W. Wathen (ISGS) and Merrianne Hackathorn (Ohio Geological Survey) edited the manuscript. 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Palmer, J.E., 1969, Fault scarp exposures in the Saint Charles and Nortonville Quadrangles, western Ken- tucky: U.S. Geological Survey Professional Paper 650- C, p. C75-C78. Potter, RE., 1957, Breccia and small-scale Lower Pennsyl- vanian over-thrusting in southern Illinois: American Association of Petroleum Geologists Bulletin, v. 41, no. 12, p. 2695-2709. Rhoades, R.F, and Mistier, A.J., 1941, Post-Appalachian faulting in western Kentucky: American Association of Petroleum Geologists Bulletin, vol. 25, no. 11, p. 2046- 2056. Rose, W.D., 1963, Oil and gas geology of Muhlenberg County, Kentucky: Kentucky Geological Survey Series X, Bulletin 1,118 p. Schwalb, H.R., 1982, Paleozoic geology of the New Ma- drid area: U.S. Nuclear Regulatory Commission, NUREG CR-2909, 61 p. Schwalb, H.R., and Potter, RE., 1978, Structure and isopach map of the New Albany-Chattanooga-Ohio Shale (Devonian and Mississippian) in Kentucky west- ern sheet: Kentucky Geological Survey, Series X, map scale 1:250,000. Smith, A.E., and Palmer, J.E., 1974, More testing needed in thrust faults of western Kentucky's Rough Creek fault system: The Oil and Gas Journal, v. 72, no. 27, p. 133-138. Smith, A.E., and Palmer, J.E., 1981, Geology and petro- leum occurrences in the Rough Creek Fault Zone: some new ideas: in Luther, M.K., ed., Proceedings of the Technical Sessions, Kentucky Oil and Gas Association, 38th Annual Meeting, June 6-7, 1974: Kentucky Geo- logical Survey, Series XI, Special Publication 4, p. 45-59. Soderberg, R.K., and Keller, G.R., 1981, Geophysical evi- dence for deep basin in western Kentucky: American Association of Petroleum Geologists Bulletin, v. 65, no. 2, p. 226-234. Treworgy, J.D., Sargent, M.L., and Kolata, D.R., 1991, Tectonic subsidence history of the Illinois basin, in Louis Unfer, Jr. Conference on the Geology of the Mid- Mississippi Valley, Program with Abstracts: Southeast Missouri State University, Cape Girardeau, 6 p. Viele, G.W., 1983, Collision effects on the craton caused by Ouachita orogeny: Geological Society of America Abstracts with Programs, 96th Annual Meeting, Indi- anapolis, Indiana, p. 712. Weibel, C.R, Nelson, W.J., and Devera, J.A., 1991, Geo- logic map of the Waltersburg Quadrangle, Pope County, Illinois: Illinois State Geological Survey, Illi- nois Geologic Quadrangle 8, map scale 1:24,000. Weller, J.M., 1940, Geology and oil possibilities of ex- treme southern Illinois, Union, Johnson, Pope, Hardin, Alexander, Pulaski, and Massac Counties: Illinois State Geological Survey, Report of Investigations 71, 71 p. Weller, J.M., Grogan, R.M., and Tippie, RE., 1952, Geol- ogy of the fluorspar deposits of Illinois: Illinois State Geological Survey, Bulletin 76, 147 p. Weller, Stuart, and Sutton, A.H., 1951, Geologic map of the western Kentucky fluorspar district: U.S. Geologi- cal Survey Mineral Investigation Map MF-2, scale 1:62,500. Withjack, M.O., Olson, J., and Peterson, E., 1990, Experi- mental models of extensional forced folds: American Association of Petroleum Geologists Bulletin, v. 74, no. 7, p. 1038-1054. Zartman, R. E., Brock, M.R., Heyl, A.V., and Thomas, H.H., 1967, K-Ar and Rb-Sr ages of some alkalic intru- sive rocks from central and eastern United States: American Journal of Science, v. 265, no. 10, p. 848-870. 19 ROAD LOG DAY 1 The road log begins at the parking lot of the Executive Inn, on the waterfront in down- town Owensboro, Daviess County, Kentucky. Parts of the road log are from Whaley et al. (1980). Miles Miles to next from point start 0.0 0.0 0.2 0.2 1.9 2.1 2.9 5.0 1.4 6.4 9.8 16.2 1.0 17.2 0.7 17.9 From the parking lot of the Executive Inn, PROCEED SOUTH on Cedar St. TURN LEFT (east) on 4th St. (U.S. Rte. 60) through Owensboro business district. TURN RIGHT (south) on Wendell H. Ford Expressway (U.S. Rte. 60 Bypass). EXIT RIGHT to the Green River Parkway southbound. The Davis (No. 6) Coal bed (Desmoinesian; Middle Pennsylvanian) is exposed in the roadcut on the east side of the parkway. Contact of Tradewater Formation (below) and Carbondale For- mation is mapped at the base of the Davis coal. Enter Ohio County. Coal and underclay in Tradewater Formation are exposed on the west side of the parkway. Tradewater Formation strata are exposed in the boxcut. From the base upward, there is under- clay, coal, and shale that contains siderite nodules, and siltstone. 2.6 20.5 Tradewater Formation strata are exposed on the east side of the parkway. A coal bed is over- lain by dark gray shale that contains plant fossils and siderite nodules. 1.3 21.8 Cross master fault of Rough Creek fault system. The steeply dipping Chesterian limestone, in the roadcut west of the parkway, is juxtaposed with Tradewater Formation strata to the north. The fault (unexposed) is interpreted as a high-angle reverse fault. 0.5 22.3 Roadcut on frontage road just west of the parkway reveals south-dipping, faulted Tradewater Formation strata. 0.4 22.7 STOP 1 - Green River Parkway, milepost 53, Rough Creek fault system. CONTINUE SOUTH on Green River Parkway. 1.0 23.7 Box cut exposes Tradewater Formation strata, including two coal beds, dipping gently south- ward on the north limb of Moorman syncline. 1.0 24.7 Reclaimed surface mines can be seen west of the parkway. The Mining City and Dunbar coal beds in the middle to mid-upper part of the Tradewater Formation were mined. (David A. Wil- liams, personal communication, 1991). 1.6 26.3 Bridge across Rough River. 1.6 27.9 EXIT Green River Parkway at Exit 48. 21 0.2 28.1 1.2 29.3 0.7 30.0 0.5 30.5 1.5 32.0 5.2 37.2 5.2 42.4 9.5 51.9 3.2 55.1 Stop sign; TURN LEFT (west) on Kentucky Rte. 69. Stop sign; TURN RIGHT (north) on U.S. Rte. 231. Enter Hartford, Kentucky. Continue on U.S. Rte. 231. Bridge across Rough River. Junction with Kentucky Rte. 136; continue north on U.S. Rte. 231. STOP 2 - Hoover Hill roadcut, Rough Creek fault system. NOTE: The shoulder is narrow and the highway is busy. Large vehicles should park along the side road at the bottom of the hill north of the roadcut. Reverse direction and return SOUTH on U.S. Rte. 231. TURN RIGHT (west) on Kentucky Rte. 136. Enter McLean County. Livermore, Kentucky. Proceed west on Kentucky Rte. 136. 4.8 59.9 Buel oil field. Production is from several Chesterian sandstones at depths of 1,280 to 2,030 feet (390 to 620 m) near southern margin of Rough Creek fault system (Johnson and Smith, 1972). Enter Calhoun, Kentucky. Proceed west on Kentucky Rte. 136. Notice the alluvial and lacustrine deposits of Wisconsinan age. Cross approximate concealed trace of master fault of Rough Creek fault system. The fault strikes west-northwest, following the base of range of hills southwest of road. The fault is a high-angle reverse fault that here exposes Caseyville Formation (Lower Pennsylvanian) on the south against McLeansboro Group (Middle and Upper Pennsylvanian) on the north, for a dis- placement of approximately 1,400 feet (430 m) (Johnson and Smith, 1975). 3.2 73.9 Enter Beech Grove, Kentucky. Kentucky Rte. 136 parallels the master fault for the next several miles. 3.5 77.4 Road junction; proceed west on Kentucky Rte. 56. 1 .6 79.0 Small roadcut exposes strata near the contact of Carbondale Formation and McLeansboro Group (Middle Pennsylvanian) about 800 feet (240 m) north of the master fault (Fairer et al., 1975). 1 .0 80.0 Cross Green River; enter Webster County. Cross to south side of concealed trace of master fault. 0.7 80.7 STOP 3. Sebree Interchange on Pennyrile Parkway. Park on shoulder west of the interchange and walk to the boxcut on the southwest corner of cloverleaf. CONTINUE WEST on Kentucky Rte. 56. 4.8 64.7 2.7 67.4 3.3 70.7 22 1.2 81.9 Sebree oil field. Production is mostly from Chesterian Tar Springs Formation at a depth of 1,750 feet (534 m). The field is immediately north of the master fault (Hansen, 1975). 0.4 82.3 TURN LEFT (south) on U.S. Rte. 41 . Sebree, Kentucky 0.2 82.5 Traffic light; TURN RIGHT (west) on Kentucky Rte. 56 through downtown Sebree. One of the deepest test holes in the Illinois basin, the Exxon No. 1 Jimmy Bell, was drilled about 1.5 miles (2.4 km) southwest of Sebree. The well was spudded in the hanging wall of the Rough Creek master fault and penetrated the fault at a depth of 9,400 feet (2,750 m) in the Knox Group, encountering approximately 2,100 feet (640 m) of repeated section. Total depth was reached at 14,280 feet (4,355 m) in Precambrian (?) andesite in the footwall of the front fault. 1.1 83.6 Pratt oil field, north of Rough Creek fault system. Oil is produced from the Tar Springs Forma- tion; gas formerly was produced from Pennsylvanian sandstone (Hansen, 1975). 6.0 89.6 Enter Poole, Kentucky. PROCEED STRAIGHT (west) onto Kentucky Rte. 145 at stop sign. 3.0 92.6 Dixie oil field. Production is from several Chesterian sandstones. The Pennsylvanian sand- stone gas reservoir was converted to gas storage in 1951 in the northern part of field (Fairer, 1973). This area is underlain by Middle to Upper Pennsylvanian bedrock thickly mantled with loess (Fairer, 1973). 3.0 95.6 Corydon South oil field. Production is from lower Chesterian Cypress Sandstone at 2,190 feet (668 m) (Fairer, 1973). Corydon, Kentucky. At traffic light, TURN LEFT (west) on U.S. Rte. 60. Enter Union County. Large buildings located south of highway are part of the Peabody Coal Company's Camp Breckinridge No. 1 Mine, an underground mine in the Springfield (W. Kentucky No. 9) coal bed. Enter Waverly, Kentucky. U.S. Rte. 60 crosses beneath conveyor that carries coal from Peabody Coal Company mines to barge-loading terminal on Ohio River. Enter Morganfield, Kentucky. Traffic light at courthouse square; TURN RIGHT (west) on Kentucky Rte. 56. Morganfield South oil field is located 1.5 miles (2.4 km) southwest of the courthouse. The field is partly north of and partly within the Rough Creek fault system. Production is achieved from numerous pay zones of Meramecian through Middle Pennsylvanian age. Smith and Palmer (1974, 1981) used well data to document an upthrown slice of Fort Payne Formation in the hanging wall of the master fault, and they postulated two episodes of movement: thrust- ing followed by normal faulting. 23 2.5 98.1 2.9 101.0 2.1 103.1 1.3 104.4 2.0 106.4 3.5 109.9 0.8 110.7 4.2 114.9 Coal-storage silos on the northwest are part of Island Creek Coal Company mines that operate underground in the Springfield (W. Kentucky No. 9) coal bed north of the Rough Creek fault system. 1.9 116.8 Junction with Kentucky Rte. 360; continue west on Kentucky Rte. 56. Spring Grove oil field, mostly north of highway, is north of Rough Creek fault system. Production is from several Pennsylvanian sandstones and the Chesterian Cypress Sandstone (Palmer, 1976). 3.1 119.9 Cross concealed trace of the front fault. Small roadcut exposes sandstone of Casey ville Forma- tion on the upthrown side of fault. Stratigraphic displacement here is approximately 1,400 feet (430 m). 1.0 120.9 Junction with Kentucky Rte. 109; continue west on Kentucky Rte. 56. The ridge north of the highway is composed of south-dipping Caseyville and Tradewater Formations in the hanging wall of the front fault. Bedrock exposures in this area are few because of thick deposits of loess, wind-blown silt is largely derived from the Ohio River Valley during Pleistocene inter- glacial stages. 2.3 123.2 Cross bridge over Ohio River; enter Gallatin County, Illinois, on Illinois Rte. 13. Before the construction of the lock and dam downstream, deformed rocks in the fault zone could be viewed on the riverbank directly below the bridge at low water. 0.6 123.8 Old Shawneetown, Illinois, one of the first settlements in the state and an early center of com- merce. According to lore, the Shawneetown bank declined to make a loan to the infant commu- nity of Chicago on the grounds that Chicago was too far from Shawneetown to amount to any- thing. The brick building with four chimneys just north of the highway west of the levee is the First Bank of Shawneetown; the large Greek Revival structure farther north is the Second Bank. The name Shawneetown fault zone commonly is used for the portion of the Rough Creek fault system in Illinois. The dual nomenclature developed from earlier workers who mapped inde- pendently in different areas. Butts (1925) established that the two fault systems were a single entity. 2.7 126.5 Enter New Shawneetown. This town developed after the great Ohio River flood of 1937 that submerged Old Shawneetown up to the second story of the Second Bank building. The prominent ridge south of Shawneetown is Gold Hill (the origin of the name is uncertain). The hill is composed largely of Caseyville Formation (Morrowan; Lower Pennsylvanian) upthrown south of the front fault, juxtaposed with Carbondale Formation (Desmoinesian; Middle Pennsylvanian) north of the fault. 2.4 128.9 Peabody Coal Company's Eagle No. 2 Mine, north of highway, operates underground in the Springfield (No. 5) Coal Member. (For Illinois stratigraphic nomenclature, the named coals are classified as members, and their numbers are different from their correlative counterparts in Kentucky). 3.8 132.7 Junction with Illinois Rte. 1. Stop sign; continue west on Illinois Rte. 13. The "Old Slave House," located 0.5 mile (0.8 km) south, was built in 1834 by John Crenshaw. The present own- ers operate the house as a tourist attraction and allege that slaves were quartered in its attic. Local residents dispute this claim; nevertheless, the fact that slavery once existed in the land of Lincoln is indisputable. Slaves were imported in pioneer days to work in saltmaking opera- tions at brine springs located along the Shawneetown master fault about 2 miles (3.2 km) south of Illinois Rte. 13. 24 2.8 135.5 TURN LEFT (south) onto Equality Road. Enter Equality, Illinois. 0.7 136.2 BEAR RIGHT around water tower. 0.2 136.4 Stop sign; TURN RIGHT (west) on Lane Street. 0.3 136.7 TURN LEFT (south) on Walnut Street (sign for Saline County Conservation Area). 0.4 137.1 Cross Middle Fork of Saline River. 1 .9 139.0 BEAR RIGHT (west) on unnamed blacktop road at base of Wildcat Hills. For the next 2 miles, the road follows the concealed trace of the master fault, which juxtaposes the lower part of the Caseyville Formation (to the south) with the upper part of the Tradewater Formation (to the north). 0.7 139.7 Unreclaimed contour-strip mines are located about 1.5 miles (2.4 km) to the north and oper- ated in the Springfield Coal Member, Carbondale Formation. 1.3 141.0 Cross concrete bridge, then TURN RIGHT (west) immediately onto gravel road. Enter Saline County, Illinois. 0.3 141.3 STOP 4 - Horseshoe upheaval. Pull into the parking area on the right. The site is maintained as a Saline County State Fish and Wildlife Area. LEAVE STOP 4 - RETURN EAST (left) to the unnamed blacktop road. 0.3 141.6 TURN RIGHT (south) on unnamed blacktop road. Pass through Horseshoe Gap, a water gap that separates the Wildcat Hills (east) from Cave Hill (west). Hills are composed of Caseyville and Tradewater Formations that dip about 20° south in hanging wall of master fault. 0.5 142.1 TURN RIGHT (west) at the entrance to Glen O. Jones Lake. LUNCH STOP. Follow blacktop road to right and up hill to picnic area. Return to park entrance. TURN RIGHT for optional stop (below) or LEFT to continue to Stop 5. OPTIONAL STOP 4A - Horseshoe Gap roadcut, 0.1 mile south of the entrance to Glen O. Jones Lake. 0.4 142.5 TURN LEFT (west) on unmarked gravel road, passing Stop 4 again. The road parallels fault zone. 0.9 143.4 Wellsite of John Dunnill No. 1 Karsch is in the clearing near the grain bin south of the road. The well spudded in Mississippian rocks in the hanging wall of the master fault and drilled through a dipping section of Mississippian to Lower Devonian strata. At 2,380 feet (726 m), the drill passed through the fault into a downfaulted sliver of Pennsylvanian shale, coal, and quartz-pebble conglomerate. The net stratigraphic displacement is about 3,500 feet (1,070 m) and the average dip of the fault is about 70°. 1.7 145.1 Unmarked gravel road curves to southwest, still paralleling the fault zone, which changes heading from due west to south-southwest at the "big bend." This change in strike can be considered the junction of the Reelfoot rift and the Rough Creek graben. 25 0.5 145.6 TURN RIGHT (west) at the unmarked gravel road junction. The fault zone now trends south- southwest. The Davis and Dekoven Coal Members in the basal Carbondale Formation were ex- tracted in the reclaimed strip mines south of the road. These coals are in fault contact with lower Chesterian strata near the edge of the woods east of the mined area. Stratigraphic offset is roughly 2,000 feet (610 m). 2.3 147.9 Cross concrete bridge; TURN RIGHT (north) at road junction. Notice more abandoned strip mines in Davis and Dekoven Coals. 0.8 148.7 BEAR LEFT, following the wide unmarked gravel road; continue due west. 3.3 152.0 Stop; TURN LEFT (south) on Illinois Rte. 145 (blacktop). 1.6 153.6 Reclaimed strip mines are on both sides of the road; Davis and Dekoven Coals were mined. Strata dip gently northward and older strata are encountered southward down-section. 3.2 156.8 Roadcuts in north-dipping sandstone of Tradewater Formation encountered on the north limb of New Burnside anticline. Interpretation of seismic profiles suggests the anticline is underlain by south-dipping thrust faults that are detached within the sedimentary column. The anticline is a compressional structure that probably formed concurrently with reverse faulting in the Rough Creek-Shawneetown and Lusk Creek fault zones. 0.3 157.1 Roadcut: notice horizontal sandstone at crest of New Burnside anticline. 1.5 158.6 Enter Pope County. 1.1 159.7 Cedar Bluff Social Brethren Church (west of highway). Cross crest of McCormick anticline, topo- graphically expressed as a ridge. McCormick anticline is parallel to the New Burnside anti- cline and similar in structure and origin. 0.5 160.2 Enter Delwood, Illinois. 3.6 163.8 Roadcuts next 0.8 mile (1.3 km) expose sandstone of lower Tradewater Formation that dip 2-3° north. 2.5 166.3 TURN LEFT (southeast) on Eddyville Road (blacktop). 1.0 167.3 Roadcut at hillcrest exposes thin-bedded sandstone of Caseyville Formation. 1.7 169.0 STOP 5 - Clay Diggings. Abandoned quarry. Park at the entrance of private blacktop drive- way just east of small roadcut of Menard Limestone (Chesterian) and walk about 600 feet (180 m) northeast on path to quarry. The trailhead is opposite of the driveway. Additional parking is located about 500 feet (150 m) southeast, just beyond bridge over Lusk Creek. REVERSE DIRECTION, return LEFT (northwest) on Eddyville Road. 2.7 171.7 Stop; TURN LEFT (south) on Illinois Rte. 145 at Eddyville. 0.1 171.8 Notice roadcut in Pounds Sandstone Member, Caseyville Formation. 2.4 174.2 Roadcuts on downgrade for the next 0.6 mile (1 km) expose sandstone and shale of Caseyville Formation; underlying Kinkaid Limestone (Chesterian) is near the bottom of the hill. 26 3.6 177.8 Enter Glendale, Illinois. 1.9 179.7 Roadcut on left (east) exposes Palestine Sandstone (Chesterian). 2.3 182.0 Roadcut on left (east) exposes sandstone and shale of Tar Springs Formation (Chesterian), dip- ping steeply northwest in Lusk Creek fault zone. 0.9 182.9 TURN LEFT (east) to Illinois Rte. 146. Fractured sandstone of Tar Springs Formation exposed along the ramp that connects Illinois Rtes. 145 and 146. 0.2 183.1 TURN LEFT (west) on Illinois Rte. 146. 0.4 183.5 STOP 6 - Dixon Springs west roadcut. Park on the shoulder, or in U-shaped driveway at the cleared area 0.3 mile (0.5 km) west. 0.4 183.9 Junction with Illinois Rte. 145. Continue straight (east) 0.1 mile and park for OPTIONAL STOP 6A, or TURN RIGHT (south) to continue to next stop. 0.2 184.1 TURN LEFT (south) on Illinois Rte. 145. 0.1 184.2 Cross front fault of Lusk Creek fault zone. Fault strikes N 45° E. The Tar Springs Formation, ex- posed in the ditch and roadcut along the east side of the highway, is faulted and juxtaposed with Caseyville Formation about 50 feet (15 m) east in the wooded area. 2.1 186.3 Cross Bay Creek. South-facing bluffs expose Chesterian strata southeast of Lusk Creek fault zone. The 2-mile (3-km) wide flat area ahead is Bay Bottoms, a late Wisconsinan channel of the Ohio River. The Ohio formerly joined the Mississippi River about 10 miles (16 km) north of the present junction at Cairo, Illinois. 3.0 189.3 Enter Massac County. 2.0 191.3 Approximate northern edge of Mississippi embayment. Late Cretaceous and younger rocks overlie Paleozoic bedrock. 0.9 192.2 Gravel pits on the left (east) of the highway expose Mounds Gravel, a late Pliocene to early Pleistocene deposit of alluvial gravel. The Mounds Gravel unconformably overlies the Upper Cretaceous McNairy Formation in the quarry floor. 7.3 199.5 TURN RIGHT (west) on U.S. Rte. 45. 0.4 199.9 TURN LEFT; entrance ramp to 1-24 south. 1.4 201.3 Cross Ohio River; enter McCracken County, Kentucky. 2.6 203.9 Paducah, Kentucky This part of the Mississippi embayment is characterized by gently rolling topography. In the Paducah area, the Paleocene Porters Creek Clay and Eocene Wilcox Sand are thickly mantled by Quaternary continental deposits and loess. Enter Marshall County. Cretaceous McNairy Formation is mantled by Quaternary deposits. Junction with Purchase Parkway; continue (east) on 1-24. Cross Tennessee River; enter Livingston County. 27 4.8 218.7 7.2 225.9 4.6 230.5 1.9 232.4 Large quarry to the right (south) in Fort Payne and "Warsaw" Formations (upper Meramecian) is overlain by Cretaceous Tuscaloosa Gravel near the edge of the Mississippi embayment. 2.6 235.0 Cross Cumberland River; enter Lyon County. 6.4 241.4 Milepost 40; roadcut exposes Ste. Genevieve Limestone (Meramecian) just east of Eddyville- Kuttawa exit. 1.1 242.5 EXIT 1-24 to Western Kentucky Parkway (eastbound), Exit 42. St. Louis and Ste. Genevieve Limestones (Meramecian) constitute the poorly exposed bedrock. 6.1 248.6 Enter Caldwell County. 2.6 251.2 Karst topography is present on both sides of highway developed in Ste. Genevieve Limestone. 0.3 251.5 Roadcut on the left (north) exposes Ste. Genevieve Limestone. 2.4 253.9 Roadcut on the left (north) exposes Ste. Genevieve Limestone. 0.6 254.5 Princeton exit. Continue (east) on Western Kentucky Parkway. 3.8 258.3 Stevens Hill roadcut (milepost 15.3) exposes Chesterian strata from Cypress Sandstone at the base (west) through Glen Dean Limestone (east). One of the larger Chesterian exposures in western Kentucky, this roadcut is fully detailed in Trace (1981). The roadcut is on the eastern, downthrown side of the Tabb fault system. 1.0 259.3 Roadcut on the right (south) exposes Tar Springs Sandstone (Trace and Kehn, 1968). 0.7 260.0 Roadcut on the left (north) exposes shale of upper Tar Springs. 1.2 261.2 Boxcut exposes Menard Limestone (Trace and Kehn, 1968). 0.5 261.7 Boxcut at hillcrest and below overpass exposes Palestine Sandstone (Trace and Kehn, 1968). 0.4 262.1 Roadcut exposes northeast-dipping upper Chesterian shale and limestone in fault zone. This unnamed fault zone is north of and subparallel with the Pennyrile fault system. 0.4 262.5 Roadcut on the right (south) exposes a fault that displaces sandstone of the Caseyville Forma- tion on the south against shale and coal of the Tradewater Formation in the downthrown northern block. This is the northern edge of an unnamed fault zone. Vertical offset across the fault zone is about 700 feet (213 m) down to the north (Trace and Kehn, 1968). Roadcut (milepost 20) exposes shale and sandstone of Tradewater Formation. Roadcuts next 1.2 miles (1.9 km) expose sandstone of Tradewater Formation. Cross Tradewater River; enter Hopkins County. EXIT Western Kentucky Parkway at Dawson Springs, Exit 24. TURN LEFT (south) on Kentucky Rte. 109. Stop; TURN RIGHT (west) on U.S. Rte. 62 and Rte. 109. Enter Dawson Springs, Kentucky. 28 0.5 263.0 0.4 263.4 1.5 264.9 2.7 267.6 0.1 267.7 1.7 269.4 0.9 270.3 0.4 270.7 1.4 272.1 0.3 272.4 4.6 277.0 1.8 278.8 TURN LEFT (south) on Kentucky Rte. 109. Right-angle turn; continue on Kentucky Rte. 109. Cross Tradewater River. Enter Christian County. Roadcut exposes sandstone of lower Tradewater Formation. TURN RIGHT (west) on Kentucky Rte. 398. TURN RIGHT (west) at entrance to Pennyrile State Park. Road junction is just above the base of Tradewater Formation (Hansen, 1973). 0.5 279.3 Pennyrile State Park Lodge. END OF DAY 1. DAY 2 Leave lodge. Casey ville Formation underlies the steep hill north of lodge and is less than 0.5 mile (0.8 km) north of Pennyrile Fault system. 0.5 279.8 TURN RIGHT (south) on Kentucky Rte. 398. 1.1 280.9 Cross concealed trace of Pennyrile fault system. Casey ville Formation on the north is faulted against Golconda Formation (Chesterian) on the south, for a net displacement of about 800 feet (240 m) (Hansen, 1973). 0.2 281.1 TURN LEFT (east) on Kentucky Rte. 1348. 2.4 283.5 TURN LEFT (north) on Kentucky Rte. 109. 0.1 283.6 TURN RIGHT (east) on Kentucky Rte. 1348. 0.8 284.4 Roadcut on left (north) exposes sandstone of Caseyville Formation north of Pennyrile fault sys- tem. 7.0 291.4 Enter Crofton, Kentucky. TURN LEFT (east) on Kentucky Rte. 800. 0.2 291.6 Stop. Continue straight (east) across U.S. Rte. 41 and railroad. After crossing tracks, continue straight (east) on Pyke Street. 0.1 291.7 TURN LEFT (north) on Anderson Street. 0.2 291.9 TURN LEFT (north) on Old Madisonville Highway (narrow blacktop). 0.7 292.6 STOP 7 - CSX Railroad cut. Park in the Foster Field Cemetery. Walk west to the railroad tracks, then 0.2 mile (0.3 km) north to the railroad cut. Turn around and proceed south on Old Madisonville Highway. 0.9 293.5 TURN LEFT (east) on Princeton Street; Kentucky Rte. 800. 1.3 294.8 TURN LEFT (north) onto Pennyrile Parkway northbound. 1.1 295.9 STOP 8 - Pennyrile Parkway roadcuts. END OF ROAD LOG 29 REFERENCES CITED Butts, Charles, 1925, Geology and mineral resources of the Equality-Shawneetown Area (parts of Gallatin and Sa- line Counties), Illinois State Geological Survey, Bulletin 47, 76 p. Fairer, G.M., 1973, Geologic map of the Poole quadrangle, western Kentucky: U.S. Geological Survey Map GQ- 1088, scale 1:24,000. Fairer, G.M., Norris, R.L., and Johnson, W.D., Jr., 1975, Geologic map of the Beech Grove quadrangle, western Ken- tucky: U.S. Geological Survey Map GQ-1230, scale 1:24,000. Hansen, D.E., 1973, Geologic map of the Dawson Springs Southwest quadrangle, western Kentucky: U.S. Geologi- cal Survey Map GQ-1061, scale 1:24,000. Hansen, D.E., 1975, Geologic map of the Sebree quadrangle, Webster County, Kentucky: U.S. Geological Survey Map GQ-1238, scale 1:24,000. Johnson, W.D., Jr., and Smith, A.E., 1972, Geologic map of the Glenville quadrangle, McLean and Daviess Coun- ties, Kentucky: U.S. Geological Survey Map GA-1046, scale 1:24,000. Johnson, W.D., and Smith, A.E., 1975, Geologic map of the Calhoun quadrangle, western Kentucky: U.S. Geologi- cal Survey Map GQ-1239, scale 1:24,000. Palmer, J.E., 1976, Geologic map of the Grove Center quadrangle, Kentucky-Illinois, and part of the Shawneetown Quadrangle, Kentucky: U.S. Geological Survey Map GQ-1314. Smith, A.E., and Palmer, J.E., 1974, More testing needed in thrust faults of western Kentucky's Rough Creek fault system: The Oil and Gas Journal, v. 72, no. 27, p. 133-138. Smith, A.E., and Palmer, J.E., 1981, Geology and petroleum occurrences in the Rough Creek Fault Zone: some new ideas: in Luther, M.K., ed., Proceedings of the Technical Sessions, Kentucky Oil and Gas Association, 38th An- nual Meeting, June 6-7, 1974: Kentucky Geological Survey, Series XI, Special Publication 4, p. 45-59. Trace, R.D., 1981, Middle Chesterian rocks in the Stevens Hill cut, Caldwell County, Kentucky: Kentucky Geologi- cal Survey, Series XI. Trace, R.D., and Kehn, T.M., 1968. Geologic map of the Olney quadrangle, Caldwell and Hopkins Counties, Ken- tucky: U.S. Geological Survey Map GQ-742, scale 1:24,000. Whaley, P.W., Beard, J.G., Duffy, J.E., and Nelson, W.J., 1980, Structure and depositional environments of some Car- boniferous rocks of western Kentucky: American Association of Petroleum Geologists, Eastern Section Field Trip Guidebook, Murray State University, 38 p. 30 o § -. ^ w CD BF*5 » S . JfliSS •%