Copyright © 1985 Acad. Sci. 0030-0950/85/0005-0218 $2.00/0

GEOLOGY OF THE PEEBLES QUADRANGLE, ADAMS COUNTY, OHIO1

E. MAC SWINFORD2, Department of Geology, Eastern University, Richmond, KY 40475

ABSTRACT. The rock sequence exposed in the Peebles quadrangle, Adams Co., Ohio, consists of over 240 m of through age rocks. These carbonate rocks, shales, and sandstones have been subdivided into 13 formations. Units which have been recently recognized in this area include the Bull Fork Formation (Upper Or- dovician), the Preachersville Member of the (Upper Ordovician), the Drowning Creek Formation (), and the Three Lick Tongue of the Chagrin Member of the (Upper ). These strata generally dip 6—8 m per km to the east, but the dip increases to 10—11 m per km in the southeast portion of the quadrangle. The increase in dip is due to the Adams Co. monocline. The monocline is thought to be the result of draping of Paleozoic rocks over a possible basement fault.

OHIOJ. SCI. 85 (5): 218-230, 1985

INTRODUCTION Peebles quadrangle will contribute to a A thorough understanding and docu- better understanding of Adams Co. geology. mentation of an area's geology is of prime Existing published bedrock investi- importance to the explorationist and ge- gations on Adams Co. are limited to por- ologist. The data can be effectively used in tions of the stratigraphic section, with only planning for recreational facilities, waste a few exceptions. John Locke studied disposal dumps, and industrial complexes. Adams Co. geology and produced the first Furthermore, these data are critical in de- county geologic map in the state of Ohio tecting water and mineral resources, as in 1838. More recent mapping projects well as engineering hazards. The combina- within Adams Co. include the geologic tion of a thorough literature search and a maps of the Maysville East quadrangle detailed field mapping program provides (Weiss et al. 1972) and the Serpent Mound this information most accurately. cryptoexplosion structure (Bucher 1936, Published information concerning the Reidel 1975). Unpublished geologic maps bedrock geology of Adams Co., Ohio, is include the Peebles quadrangle (Swinford surprisingly meager considering that the 1983) and the northwestern portion of county has abundant bedrock exposures Adams Co. (Kaufmann 1964). Other stud- and only minor glacial cover. Rocks within ies which address a substantial portion of this area are of diverse ages, lithologic the stratigraphic section of the area include types, and have significant regional and Bowman's (1956) study of the Niagaran local structural trends. The Peebles quad- rocks of Highland County, Rexroad et al. rangle located in northeast Adams Co. (1965) study of the Silurian of southern (fig. 1) has all of these characteristics Ohio and northern Kentucky, and Kallio's which allow for an exceptionally pro- (1976) study of the Silurian along Ohio ductive study of the area's geology. Docu- Brush Creek in Adams Co. The soil survey menting the geologic setting within the of Adams Co. (Taylor 1938) provides addi- tional information on the presence of bed- xManuscript received 3 July 1985 and in revised rock and its effect on soil and topography. form 30 September 1985 (#85-26). 2Present Address: Ohio Department of Natural METHODS AND MATERIALS Resources, Division of Geological Survey, Fountain Traditional techniques and instruments were uti- Square, Bldg. B, Columbus, OH 43224 lized in gathering data on the rocks of the Peebles 218 OhioJ. Sci. GEOLOGY OF THE PEEBLES QUADRANGLE 219

and majority of the Peebles quadrangle consists of the Interior Low Plateau region. This topography contains low rolling hills with some moderately steep-walled valleys which have 30—61 m of relief. The abrupt change of the rugged topography of the Appalachian Plateau to the landforms of the Interior Low Plateau creates a boundary called the Appalachian Escarpment. The escarpment is present in the southeast por- tion of the Peebles quadrangle as a north- east-trending lineament. Ohio Brush Creek and Scioto Brush Creek are the main drainage basins within the Peebles quadrangle. Ohio Brush Creek, centrally located within the quad- rangle, flows southward toward the Ohio PEEBLES River. Ohio Brush Creek and tributaries of QUADRANGLE this stream are responsible for a majority of ADAMS the topographic dissection of the study COUNTY area. Creeks flowing eastward in the south- eastern portion of the quadrangle drain into Scioto Brush Creek which lies 10 km east of the study area. FIGURE 1. Location of the Peebles quadrangle, STRATIGRAPHY. The entire rock strati- Adams Co., Ohio. graphic section within the Peebles quad- quadrangle. Instruments used in the field were a rangle consists of more than 244 m of Paulin Terra altimeter, hand level, Brunton com- Ordovician, Silurian, Devonian and pass, and base maps of the Peebles and surrounding Mississippian age rocks. Thirteen separate quadrangles. The elevation of 714 data points was formations and four unconformities were documented with an altimeter. Numerous strati- identified within the stratigraphic section graphic sections within the Peebles quadrangle were measured with a hand level or rule. Unusually thick (fig. 2). Rocks within the study area can sections (particularly in homogenous shales) were be separated into general lithologic groups also measured with an altimeter to confirm hand according to their age. Upper Ordovician level estimations. Elevation of data points and for- and Lower Silurian rocks are dominantly mation thicknesses of measured sections were used thin-bedded and shales. Middle to produce structure contour and isopach maps at a 1:24,000 scale. Aerial photographs were also used and Upper Silurian rocks are thick, unin- to delineate terrace and alluvial deposits along terrupted sequences of carbonates or clay streams. A geologic map was constructed from this shales. Devonian rocks are mainly dark, data and is on file at the Ohio Department of Natu- petroliferous shales with some greenish- ral Resources, Division of Geological Survey. gray shales. Lower Mississippian rocks are DISCUSSION silty shales and sandstones. Each of the Two physiographic regions occur within units will be described with other rock the Peebles quadrangle, the Appalachian units of similar geologic age. Plateau and the Interior Low Plateau. The ORDOVICIAN. The oldest rocks ex- Appalachian Plateau region occurs in the posed in the Peebles quadrangle are Upper southeast edge of the quadrangle. This to- Ordovician age carbonates and shales. Peck pography consists of high narrow ridges (1966), in conjunction with the Kentucky with steep-walled valleys having an aver- geologic mapping program, described and age relief of 61—122 m. The remainder defined rocks of Richmondian age in the 220 E. M. SWINFORD Vol. 85

FORMATION S MEMBER LITHOLOGY

ALLUVIUM

BEREA SANDSTONE

BEDFORD SHALE DEVONIA N

OLENTANGY SHALE LILLEY Fm. BISHER Fm. SILURIA N

DRAKES

BULL FORK Fm.

FIGURE 2. Generalized stratigraphic column of the rocks found within the Peebles quadrangle. OhioJ. Sci. GEOLOGY OF THE PEEBLES QUADRANGLE 221 vicinity of Maysville, Kentucky. These units were mapped in the Ohio portion of the Maysville East quadrangle (Weiss et al. 1972) in Adams and Brown counties. The use of Peck's nomenclature is accepted within the Peebles quadrangle and in- cludes the Bull Fork Formation and the overlying Preachersville Member of the Drakes Formation. The Bull Fork Formation consists of very fossiliferous interbedded limestones and shales. The limestones are light to blu- ish gray, medium to coarse grained, in beds 9—30 cm thick and are dolomitic. A particularly good exposure reveals thin limestones grouped into continuous bands 30—39 cm thick separated by shale beds approximately 9 cm thick. The Bull Fork is discontinuously ex- posed along Ohio Brush Creek and western 1km tributaries of this stream. The best expo- FIGURE 3. Location of best exposures for rocks sures of these rocks occur in the Little East found in the study area. Locality 1: Bull Fork Fm. Fork 0.4 km south of the intersection with (upper portion), Drakes Fm., and Drowning Creek State Route 32 where the uppermost Fm. (lower portion). Locality 2: Drakes Fm. 3.1 m are exposed (fig. 3, locality 1). (upper portion), and Drowning Creek Fm. Locality 3: Drowning Creek Fm. (Dayton The lack of exposure of the lower contact Mmbr.), Estill Shale, Bisher Fm., and Lilley Fm. of the Bull Fork Formation prohibits deter- Locality 4: Estill Shale (upper portion), Bisher mination of its thickness within the study Fm., Lilley Fm., and Peebles Dolomite (transitional area. The upper contact of the Bull Fork zone). Locality 5: Bisher Fm., Lilley Fm., Peebles Dolomite, Greenfield Dolomite, and Tymochtee with the overlying Preachersville Member Dolomite within Plum Run Quarry. Local- of the Drakes Formation is conformable ity 6: Greenfield-Tymochtee Dolomites, Olen- and gradational over a 0.3-m interval. The tangy Shale, Ohio Shale, , and Berea contact is placed at the top of the highest Sandstone. continuous fossiliferous layer of the Bull Fork Formation (Peck 1966). The Drakes Formation appears as dis- The Preachersville Member of the continuous exposures along Ohio Brush Drakes Formation, hereafter referred to as Creek and tributaries of the stream much the Drakes Formation, consists chiefly of the same as the Bull Fork Formation. It mudstone with thin discontinuous dolo- can easily be recognized by the distinctive mite beds less than 6 cm thick. The mud- dusky-red color which appears in the over- stone is greenish gray to dusky red, lying soil. The best total section within the calcareous to dolomitic, locally silty and study area is located within the Little East fissile to platy. The dolomite beds are light Fork just south of the intersection with gray, calcareous in places, sparsely - State Route 32 where an estimated 7.6 m iferous and argillaceous. The upper 45 cm are exposed (fig. 3, locality 1). of the formation consist of thin beds (less The Drakes Formation ranges from 3.4 than 3.0 cm thick) of interbedded lime- to 8.2 m in thickness within the study stone and shale. These limestones are area. The uppermost 46 cm of the Drakes medium gray, finely crystalline and dolo- Formation grade into a resistant argilla- mitic. The shales are light gray, fissile and ceous limestone of the Silurian Brassfield slightly dolomitic. Formation. This upper contact is thought 222 E. M. SWINFORD Vol. 85

to be unconformable, however the author which is medium to light gray, medium did not encounter any evidence of erosion to very coarse grained, argillaceous and along the Drakes-Brassfield contact. This crinoidal with bedding dominated by contact is unconformable at an exposure megaripples. The bead bed represents a 3.4 km northwest of West Union, Ohio consistent physical marker at the top (Grahn and Bergstrom 1985) which sug- of the (Rexroad gests it is also unconformable in the study et al. 1965). area. Therefore, despite the lack of physical The Brassfield Formation crops out evidence, the Drakes-Brassfield contact in within the study area along most of Ohio the Peebles quadrangle will be considered Brush Creek and the western tributaries of unconformable. this stream. The best exposure within the SILURIAN. The oldest Silurian age quadrangle is located on the west side of rocks in the area are the limestones, shales, State Route 41 immediately south of a and dolomites of the Brassfield Formation. bridge crossing Ohio Brush Creek approxi- The Brassfield ranges in thickness from mately 1.6 km south of Jacksonville 14.3 to 19.8 m and within this interval, (fig. 3, locality 2). five units are recognized (Kaufmann The Noland Formation (Rexroad et al. 1964). 1965) consists of two separate lithologies The basal unit, or Belfast Member, (Rex- within the Peebles quadrangle. The lower road et al. 1965) consists of 1.5-1.8 m of lithotype consists of limestone medium to massive limestone which is bluish gray, dark gray, medium to coarse grained and fine grained, silty and dolomitic. This moderately fossiliferous, interbedded with basal unit is gradationally overlain by a bluish-gray shale. The upper lithotype, or 1.5—2.7-m thick interbedded limestone Dayton Member (Rexroad et al. 1965), is and shale facies. The limestone is medium yellowish-gray to grayish-pink limestone, gray to bluish gray, thin bedded, medium fine to cryptocrystalline, with thin to mod- crystalline, and argillaceous. The shales are erately thick beds having irregular sur- greenish gray, 3—6 cm thick and silty. faces. The Dayton Member is distinct and These limestones and shales grade upward a useful mapping unit because of the re- over a 0.3 m interval into a chert-rich sistant ledge-forming nature. facies. The Noland Formation ranges in thick- The cherty facies consists of massive re- ness from 1.2 to 4.9 m within the study sistant cherty limestone, which is light to area. The formation thins to the north medium gray, medium to fine grained, mainly at the expense of the lower litho- thin to nodular bedded with zones of glau- type, which thins from 2.4 to 0.4 m in conite and fossil hash. The total unit is thickness. The Noland crops out along the 1.5—2.1 m thick and forms a distinct re- valley of Ohio Brush Creek and the western sistant ledge. The cherty facies grades up- tributaries of this stream. It is well exposed ward into an upper interbedded limestone at locality 2, but steepness of the section and shale facies. Also present within this precludes close examination of the Noland facies are limestone layers, which are Formation (fig. 3, locality 2). Better ex- 21-46 cm thick, brown to dark red, posures of the Noland, although less acces- coarse grained, friable, oolitic and which sible, can be found on the west-facing contain stem plates and abundant slope of Wheat Ridge along Ohio Brush glauconite. The upper interbedded lime- Creek. stone and shale facies ranges in thickness The upper contact with the Estill Shale from 9.5 m to an estimated 15.5 m. The is disconformable and generally sharp. The upper contact with the uppermost facies or disconformity is indicated by a glauconitic bead bed, is sharp and rarely exposed. The zone within the basal Estill Shale and by a bead bed consists of a single limestone bed biostratigraphic break between the Dayton OhioJ. Sci. GEOLOGY OF THE PEEBLES QUADRANGLE 223

Member and the Estill Shale (Rexroad The entire Estill Shale ranges in thick- et al. 1965, Rexroad 1967). ness from 30 to 45 m and averages Individually, the Noland is too thin to about 37 m within the study area. The be mapped at a 1:24,000 scale and there- best and most complete exposure of the fore was combined with the Brassfield to Estill Shale within the Peebles quadrangle form a single mapped unit. The Belfast is in a roadcut on the east side of State Member of the Brassfield Formation and Route 41, about 0.4 km south of Jackson- the Dayton Member of the Noland For- ville (fig. 3, locality 3). mation provide distinct lithologic bound- The contact of the Estill Shale with the aries for this mapped interval. Recently, overlying undulates lo- McDowell (1983) examined this same in- cally as much as 18 cm. The basal 15— terval in northern Kentucky and southern 21 cm of the Bisher Formation are very Ohio and found the Noland-Brassfield argillaceous dolomite indicating a con- contact marker, the bead bed, to be a fau- formable transition from shale to silty nal zone. This zone is repeated in the sec- dolomite deposition. This is the most con- tion and rises rapidly upsection northward sistently exposed contact within the study into Ohio. He concluded therefore that the area because of the prominent overhangs bead bed is too difficult to locate in the and significant breaks in slope created by field and is not useful or desirable as a the resistant Bisher Dolomite. Numerous formational boundary. The formation springs further accentuate this contact. names of Brassfield and Noland were The Bisher Formation (Foerste 1923) dropped and the combined interval was consists of dolomite that is light to me- renamed the Drowning Creek Formation, dium gray, fine grained, silty, argilla- consisting of, in ascending order: The ceous, calcitic, and locally contains chert Brassfield Member, a middle undiffer- nodules and rip-up clasts. The Bisher is entiated interval, and the Dayton Member thin bedded in the lower one-third of the north of Bath Co., Kentucky. This re- formation, very thickly bedded in the up- classification conforms with boundaries the per two-thirds, and weathers to a distinct author mapped in the Peebles quadrangle brownish-orange color. An additional and also with those mapped in northern lithofacies consist of a fine to coarse- Kentucky in the Kentucky mapping pro- grained, light-gray, irregularly bedded, gram. Detailed mapping proves the calcitic dolomite containing abundant fos- Drowning Creek Formation is a useful di- sils dominated by the brachiopod, Crypto- vision within the Silurian System locally thyrella cylindrica (Bowman 1956). and should be adopted for the Adams Co. This lithofacies lies between 0.76 and area. 2.6 m above the base of the Bisher and is Disconformably overlying the Noland consistently present as a single unit 30— or Drowning Creek Formation is the Estill 45 cm thick. It has also been observed as Shale (Rexroad et al. 1965). The Estill three separate layers within a 1.5-m inter- consists primarily of soft reddish-brown to val. The Cryptothyrella cylindrica lithofacies greenish-gray shale. Thin dolomite string- maintains the same stratigraphic rela- ers, which are dark yellow, discontinuous, tionship throughout Highland and Adams silty and argillaceous, become abundant in counties and may represent a time- the upper one half of the formation, yet stratigraphic marker (Bowman 1956). only constitute a small percentage of the In the study area, the thickness of the total lithology. A basal glauconitic zone is Bisher Formation ranges from 6 to 17 m present throughout the study area. It oc- and averages about 9 m. This fluctuation curs near the base as either pelloidal glau- in thickness is due to the undulatory na- conite stringers or as a 0.3—0.5-m thick ture of the top of the Bisher. shale layer with disseminated glauconite. The Bisher Formation crops out along 224 E. M. SWINFORD Vol. 85

Ohio Brush Creek and the major tribu- Lilley lithology sharply interfingering taries of this stream. It forms a caprock for with a light-gray, pure dolomitic Peebles many bluffs and is a resistant ledge-former. lithology. This zone may also contain a A complete exposure of Bisher is present fine-grained, silty, thick-bedded, vuggy along the Appalachian Highway 1.6 km dolomite, which appears to be a mixture west of the intersection of the highway of both Peebles and Lilley lithologies, with State Route 41 (fig. 3, locality 4). and may represent a distinct transition The contact with the overlying Lilley lithology. Formation is difficult to discern on a The Peebles Dolomite (Foerste 1923) is fresh outcrop but is easily recognized on a light gray to bluish gray, fine grained to weathered surface. The Bisher weathers to microcrystalline, with thick bedding that a smoother-surfaced rock, whereas the Lil- is poorly developed in the lower portion. ley Formation weathers to a rough, com- The formation has well-developed fossil monly vuggy surface. A series of thin molds and solution cavities giving the unit shales mark the top of the Bisher, but are a pock-marked appearance. not always present (Foerste 1935). The Peebles Dolomite crops out almost The (Foerste 1923) exclusively east of Ohio Brush Creek and consists of two main lithofacies in the the weathered surface creates broad rolling Peebles area, a crinoidal-carbonate and an plains. Plum Run Quarry, located approxi- argillaceous-carbonate lithology (Bowman mately 1.6 km east of the study area pro- 1956). The crinoidal-carbonate lithofacies vides the best exposure of the Peebles consists of light- to medium-gray, fine- (fig. 3, locality 5). The poorly developed grained dolomite which is thin to thick bedding of the Peebles Dolomite can be bedded, and contains abundant fossil frag- readily distinguished from the distinct ments dominated by crinoid stem plates. even bedded Greenfield Dolomite above. The argillaceous-carbonate lithofacies is On weathered or partially covered expo- not everywhere present within the study sures, the very light-gray, soft, equidi- area as seen 0.4 km southwest of the Steam mensional particles of the Peebles contrast Furnace Cemetery, but where present it with the darker, harder, more hackly- overlies the crinoidal-carbonate lithofacies. fractured Greenfield Dolomite. The Lilley Formation ranges in thick- The Peebles ranges between about ness from 5.5 m to possibly as much as 12—21 m in thickness. The exact deter- 19.8 m within the study area and averages mination of the Peebles' true thickness is about 9.1—10.7 m. The thickness of the not possible because of the nature of the Lilley Formation fluctuates rapidly. Obser- lower contact with the Lilley, and lack of vations suggest that as the Lilley thickens, exposure. An additional tongue of dense, the Bisher correspondingly thins (Bowman micritic Peebles lithology enters the quad- 1956). The Lilley Formation occurs as the rangle from the north and west (R. S. Bow- dominant rock on many bluffs above the man, pers. comm.). This upper tongue Ohio Brush Creek and tributaries of the possibly explains the unusually thick stream and is associated with karst topog- sequence of Peebles present in the east- raphy. An exposure of the entire Lilley For- central portion of the study area. The Pee- mation is present in a roadcut along the bles is unconformably overlain by the Appalachian Highway 1.6 km west of the Greenfield Dolomite. The unconformable intersection with State Route 41 (fig. 3, surface has only 0.91 m of relief within locality 4). Plum Run Quarry. The Peebles Dolomite intertongues The Greenfield Dolomite, first named with the Lilley Formation over an esti- "stone" (Orton 1871), is light bluish, mated 3-1—6.2-m thick transitional zone. brownish or olive gray, fine grained, lami- The transitional zone may consist of dis- nated, thin to thick bedded, hard, stylo- tinct beds of medium-gray, argillaceous litic, and contains thin, mesoporous vuggy OhioJ. Sci. GEOLOGY OF THE PEEBLES QUADRANGLE 225 layers. Also present are discontinuously The high degree of erosion on the bedded, medium-gray dolomite layers Silurian-Devonian erosion surface (up to with no visible porosity. The Greenfield is 21.4 m), removed the entire Tymochtee estimated to range in thickness from 1.5 to Dolomite and allowed Devonian age rocks 7.9 m within the study area. The large to directly overlie either the Greenfield or range in thickness is due to the removal of Tymochtee Dolomites. Regionally in a significant portion of the Greenfield and Ohio, the Silurian-Devonian unconformity all younger Upper Silurian rocks by the has a wide range of stratigraphic units at Silurian-Devonian erosional episode. the boundary. The underlying units may The Greenfield is conformably overlain be as old as Middle to Upper Silurian, by the Tymochtee Dolomite. This contact while overlying units may be Middle to is difficult to recognize due to similarities Upper Devonian in age (Summerson in lithology between the two units. In 1959). Plum Run Quarry, one of the best known Below this contact surface in the study exposures of the contact in southern Ohio, area, a zone of highly weathered dolomite the contact is arbitrarily placed at a thick up to 0.46 m thick is underlain by un- layer containing abundant primary struc- altered rock. The zone is a soft, silty, calci- tures (Schmidt et al. 1961, Butterman tic dolomite containing individual laminae 1961, Miller 1955). Owing to the lack of of glauconitic, carbonaceous material, and exposure and subtle nature of the contact, highly oxidized clay shales. The zone is as well as the irregularity of the contact well exposed in a ditch behind Turkey surface, the Greenfield and Tymochtee Creek Church in the southeast portion of were mapped as a single unit. the study area (fig. 3, locality 6). The The Tymochtee Dolomite (Winchell Hillsboro Sandstone (Orton 1871) has been 1873) contains two types of lithologies as identified within this same interval in exposed in the Plum Run Quarry. The Highland Co. but was not observed in the lower portion is medium-gray to light- study area (Carman and Schillhahn 1930, bluish-gray, fine-grained, hard dolomite Rogers 1936). which is thin to thick bedded with some DEVONIAN. The vuggy zones. The upper portion is a light- (Winchell 1874) is greenish gray to bluish gray, thin-bedded, argillaceous dolomite, gray, semi-lithified and contains black car- with shale partings having well-developed bonaceous shale stringers. It weathers to a mudcracks. crumbly greenish-gray shale that becomes The Tymochtee Dolomite ranges in mucky when wet. It is believed to be the thickness from 0 to 15.2 m within the "Upper" Olentangy Shale as defined by study area. The wide range in thickness is Tillman in 1970 (Gable 1973). due to erosion along the Silurian-Devonian The Olentangy Shale is consistently contact. The Tymochtee is rarely exposed 8.2—8.5 m thick in several measured sec- within the Peebles quadrangle and is lo- tions. The Olentangy is best exposed in cally missing beneath the Silurian- road ditches behind the Turkey Creek Devonian unconformity. The best exposure Church in the extreme southeast portion of of both the Greenfield and Tymochtee Do- the study area (fig. 3, locality 6). lomites is in Plum Run Quarry where The Olentangy Shale can discon- 23 m of combined section can be observed formably overlie the Tymochtee or Green- (fig. 3, locality 5). A graben structure field Dolomites within the study area. The within the quarry has allowed an unusually Ohio Shale appears to conformably overlie thick section of Upper Silurian rocks to the Olentangy Shale. The greenish-gray escape pre-Middle Devonian erosion. It is shale of the Olentangy abruptly grades up- probable that the thickness of Upper Silu- ward into the black-fissile Ohio Shale. rian rocks present in the quarry graben The Ohio Shale (Shaler 1877) consists of exceeds that found in the study area. black-carbonaceous shale with greenish- 226 E. M. SWINFORD Vol. 85 gray shale rich zones and can be separated Mississippian systemic boundary (Pepper into three distinct members in the study et al. 1954). In the study area, the contact area. In ascending order they are: the is sharp with the uppermost 12 cm of the Huron Member, the Three Lick Tongue of Ohio Shale becoming soft and claylike the Chagrin Member, and the Cleveland before abruptly changing to Bedford Member. lithology. The "Huron Shale" Member (Newberry MISSISSIPPIAN. The Bedford Shale 1870) is brownish-black to dark-gray, car- (Newberry 1870) represents the lowermost bonaceous shale with carbonate concretions Mississippian age rock present within the up to 0.6 m in diameter in the lowermost Peebles quadrangle. The lower two-thirds part. The Huron Member is estimated to of the unit consists of a soft, greenish-gray be more than 52 m thick within the Pee- shale which grades upward into a light- bles quadrangle. bluish-gray to medium-bluish-gray, hard, Above the Huron Member, is a 6.1-m sandy siltstone. Well-developed oscillation thick unit of brownish-black shale with ripple marks are abundant within the silt- greenish-gray shale interbeds. Provo et al. stone of the upper portion of the Bedford. (1977) named this unit the Three Lick Bed The Bedford Shale is estimated to be of the Ohio Shale in a measured section 24 m thick within the study area. It is best along the Appalachian Highway at Tener exposed behind Turkey Creek Church Mountain, 96 km east of the study area. (fig. 3, locality 6). The upper contact of The Three Lick Bed has been used in Ken- the Bedford Shale with the Berea Sand- tucky as a stratigraphic marker within the stone is gradational and arbitrarily placed Devonian age black shale. Broadhead et al. where the upward increasing sand content (1982) recognized the Three Lick Bed in begins to dominate the lithology (Hyde southern Ohio and Kentucky to be a distal 1953). equivalent or tongue of the Chagrin Mem- The (Newberry 1870) ber of the Ohio Shale. This unit is present is Lower Mississippian in age and is the throughout the study area and should youngest bedrock unit that occurs in the be recognized within the nomenclature. Peebles quadrangle. The Berea consists of Therefore, to better describe the lithology medium to light-gray or light olive-gray, of the unit and to emphasize usefulness of silty to shaly, medium-bedded sandstone the unit in correlating the black shale se- with ripple marks in the lower portion. quence in Ohio and Kentucky, the author Silt and shale content decrease upward and has chosen to rename the interval the Three the unit becomes a resistant sandstone in Lick Tongue of the Chagrin Member. the upper portion. The Cleveland Member (Newberry The thickness of the Berea Sandstone 1870) is a homogenous, very petroliferous, was not determined within the study area black shale which weathers to light-gray, due to poor exposure. However, 13.7 m fissile chips. It is estimated that this mem- were measured at Tener Mountain, 9.6 km ber is about 18.3 m thick within the study east of the study area (Provo et al. 1977). area. The Berea Sandstone forms distinctive flat The Ohio Shale was measured by altime- caps on hills just east of the study area. ter to be 76.5 m thick at a nearly complete QUATERNARY DEPOSITS. The Peebles section located behind the Turkey Creek quadrangle contains two levels of terraces Church along a road that ascends Peach above the present alluvial deposits which Mountain (fig. 3, locality 6). This section are associated with the Ohio Brush Creek represents the only reliable thickness taken and Little West Fork. A laterally extensive near the study area. terrace plain occurs no higher than ap- The upper contact between the Ohio proximately 18 m above the present creek Shale and the overlying greenish-gray level. A second minor terrace level lies ap- Bedford Shale represents the Devonian- proximately 21m above the present OhioJ. Sci. GEOLOGY OF THE PEEBLES QUADRANGLE 227

Anomalous Zone

Serpent . Mound

FIGURE 4. Map of regional structures and the geo- physical zone influencing rocks of the Peebles quad- rangle. stream level. These terraces consist of clayey to silty loam (Taylor 1938) with no significant sand and gravel content. STRUCTURE. The Cincinnati Arch rep- resents the dominant regional geologic structure in southern Ohio (fig. 4). The FIGURE 5. Structure contours of the Bisher-Estill arch is a broad, linear, structural high contact. Note steepening surface in the southeast which extends northward from corner and faults in the northeast corner. to southern Ohio where it bifurcates to form the north-trending Findlay Arch and increases from 10 or 11 m per km to 15 m the northwest-trending Kankakee Arch. per km (R. S. Bowman, pers. comm.). The The Peebles quadrangle lies on the east rather abrupt dip increases in the southeast flank of the Cincinnati Arch. The strata Peebles quadrangle and in the Plum Run dip eastward at a uniform rate of 6—8 m Quarry indicate the monocline may have per km, or 0.7 degrees, into the Appa- multiple hinges. lachian Basin (fig. 5). The Adams Co. monocline, where Strata in the southeast portion of projected southward, appears to join major the Peebles quadrangle increase in dip faults mapped in Upper Ordovician rocks and change slightly in structural strike in northern Kentucky (Galbraith et al. (fig. 5). Strata dip increases from 6 or 8 m 1975). This is the West Hickman Fault per km to 10 or llm per km. Structural zone of the Kentucky River fault system strike also deviates slightly from a north- (fig. 4). The soft Ordovician shales, found south direction to approximately N10 °E. in the subsurface northward in Ohio, may The increase in structural dip is believed to have absorbed the energy of the fault zone be western-most evidence of warping asso- causing it to evolve to a warp to the north. ciated with the Adams Co. monocline. The The Adams Co. monocline may be the sur- monocline represents a major deviation ficial expression of that warp (Reidel et al. from the seemingly constant structural na- 1982). Further regional studies of the pre- ture of the east flank of the Cincinnati Middle Devonian erosion on Upper Siluri- Arch in the Peebles area. The monocline an age carbonates in Adams Co. may show continues to influence rocks to the east as that this monocline underwent initial acti- evidenced in Plum Run Quarry where dip vation prior to Devonian sedimentation. 228 E. M. SWINFORD Vol. 85

The author was unable to confirm the tains rocks of four Paleozoic Systems position of the Adams Co. monocline axis measuring over 240 m in thickness. The in the proximity of the Ohio Brush Creek general structural trend of the rocks is re- valley as suggested by Galbraith (1968). gionally controlled by the Cincinnati Four separate structure contour surfaces Arch, whereas faults and folds are locally were drawn across his projected axis. They controlled. show that the strata dip eastward at a con- The bedrock in the Peebles quadrangle sistent rate of less than one degree with no consists of carbonates, shales and sand- anomalous dip increases. stones of Ordovician, Silurian, Devonian Nearby, another significant local struc- and Mississippian age. In ascending order, ture is the Serpent Mound cryptoexplosion the rock units are: the Bull Fork Formation structure. The cryptoexplosion structure is and the Preachersville Member of the an intensely disturbed circular feature ap- Drakes Formation (Upper Ordovician), the proximately 6.4 km in diameter located Drowning Creek, Estill, Bisher, Lilley about 3 • 2 km north of the Peebles quad- Formations and the Peebles, Greenfield rangle. Rock displacement on the order of and Tymochtee Dolomites (Silurian), the 107 m has occurred in the central portion Olentangy and Ohio Shales (Upper of the structure (Schmidt et al. 1961), Devonian), and the Bedford Shale and however, the deformation decreases rapidly Berea Sandstone (Lower Mississippian). A outward (Galbraith 1968). Four faults combined Brassfield-Noland Formation mapped in the northeast portion of the coincides with the author's mapped inter- Peebles quadrangle could be considered ex- val and should be distinguished as the tensions of Serpent Mound deformation Drowning Creek Formation in Adams Co. because these faults enter the quadrangle (McDowell 1983). from the north and appear to die out in a Rocks of the Peebles quadrangle dip southerly direction (fig. 5). eastward 6—8 m per km, or 0.7 degrees, The West Hickman Fault zone, the due to the east flank of the Cincinnati Adams Co. monocline, and the Serpent Arch. In the south-east corner of the study Mound cryptoexplosion structure are fea- area, rocks increase in dip from 10 to 11 m tures which lie within a band of gravity per km, or one degree, due to a local struc- and magnetic anomalies. This anomalous ture called the Adams Co. monocline. This geophysical zone, called the East Con- increase in dip may represent only the tinent gravity high, trends in a north- westernmost hinge or flexure related to the south direction from Tennessee through monocline which lies east of the study area. Kentucky, to southern Ohio (fig. 4). The Faults in the north-east corner of the quad- gravity high is believed to represent the rangle appear to be extensions of defor- failed arm of a Keweenawan age rift zone mation associated with the Serpent Mound (Keller et al. 1982). Reactivated move- cryptoexplosion structure located approxi- ment along basement faults, often associ- mately 3.2 km to the north. ated with rift structures, may explain the Detailed mapping of an area's geology presence of surficial faults, monoclines and generates data that can be immediately ap- even the cryptoexplosion structure in plied to industry's needs and provides the Adams Co. and the surrounding area. basis for further geologic investigations. The geologic map produced depicts areas CONCLUSION of potentially thick Peebles Dolomite for The complex geology of Adams Co., mineral exploration and in addition, de- Ohio, is well-expressed in rocks exposed in tails shale rich units which are engineering the Peebles quadrangle. Investigations for hazards such as the Estill and Olentangy production of a geologic map of the Pee- Shales and the Drakes Formation. For envi- bles quadrangle revealed diversity in the ronmental studies, the map pinpoints stratigraphy and structure of the rocks. zones of prominent water production for The exposed stratigraphic sequence con- hydrologic studies, and also identifies the OhioJ. Sci. GEOLOGY OF THE PEEBLES QUADRANGLE 229 position of karst prone formations like the northwestern Adams and northeastern Brown Lilley, which is vital to locating a waste Counties, Ohio. Unpubl. M.S. Thesis. Ohio State Univ., Columbus. 184 p. disposal site. Using the map as a basis, Keller, G. R., A. E. Bland and J. K. Greenberg further geologic studies could include a 1982 Evidence for a Late tectonic regional investigation as to the nature of event (rifting?) in the eastern midcontinent re- the Silurian-Devonian unconformity or the gion, . Tectonics. 1: 213-223. Adams Co. monocline. Kallio, T. A. 1976 The stratigraphy of the Low- er and Middle Silurian, Medina, Clinton, and ACKNOWLEDGMENTS. I wish to thank Dr. Roy C. Lockport Groups along Ohio Brush Creek, Ad- Kepferle of Eastern Kentucky University for his sug- ams County, Ohio. Unpubl. M.S. Thesis. Miami gestions and editorial comments on the manuscript. Univ., Oxford. 160 p. Dr. Richard Bowman of Davon, Inc. suggested this Locke, J. 1838 Report in the second annual re- project and kindly allowed the author access to Plum port on the geological survey of the State of Ohio. Run Quarry on numerous occasions. Ohio Geol. Surv. p. 203-274. McDowell, R. C. 1983 Stratigraphy of the Silu- LITERATURE CITED rian outcrop belt on the east side of the Cincinnati Bowman, R. S. 1956 Stratigraphy and paleon- arch in Kentucky, with revisions in the nomen- tology of the Niagaran Series in Highland clature. U.S. Geol. Surv. Prof. Pap. 1151-F, County, Ohio. Unpubl. Ph.D. Dissert., Ohio 27 p. State Univ., Columbus. 339 p- Miller, P. M. 1955 Stratigraphy and petro- Broadhead, R. R, R. C. Kepferle and P. E. Potter graphy of the Greenfield and Tymochtee forma- 1982 Stratigraphic and sedimentologic controls tions of southern Ohio. Unpubl. M.S. Thesis. of gas in shale—Example from the Upper De- Ohio State Univ., Columbus. 182 p. vonian of northern Ohio. Amer. Assoc. Petro- Newberry, J. S. 1870 Report on the progress of leum Geologists Bull. 66: 10-27. the geological survey of Ohio in 1869- Ohio Geol. Bucher, W. 1936 Cryptovolcanic structures in Surv. part 1, p. 3-53. the United States. 16th Inter. Geol. Cong. U.S. Orton, E. 1871 The geology of Highland Rep. 1933. 2: 1055-1084. County. Ohio Geol. Surv. Rept. Prog, in 1870. Butterman, W. C. 1961 Insoluble residues of part 3, p. 155-309. the Silurian section in western Ohio. Unpubl. Peck, J. H. 1966 Upper Ordovician formations M.S. Thesis, Ohio State Univ., Columbus. 161 p. in the Maysville area, Kentucky. U.S. Geol. Carman, J.E. and E. O. Schillhahn 1930 The Surv. Bull. 1244-B, p. B1-B30. Hillsboro Sandstone of Ohio. J. Geol. 38: Pepper, J. F., W. DeWitt, Jr. and D. F. Demarest 246-261. 1954 Geology of the Bedford Shale and the Foerste, A. F. 1923 Notes on the Medinan, Berea Sandstone in the Appalachian basin. U.S. Niagaran, and Chester . Denison Univ. Sci. Geol. Surv. Prof. Pap. 259, 109 p. Lab. J. 20: 37-120. Provo, L.E., R.C. Kepferle and P. E. Potter 1935 Correlation of Silurian formations 1977 Three Lick Bed: Useful stratigraphic in southwestern Ohio, southeastern , marker in Upper Devonian shale in eastern Kentucky, and western Tennessee. Denison Univ. Kentucky and adjacent areas of Ohio, West Sci. Lab. J. 30: 119-205. , and Tennessee. U.S. Energy Res. Dev. Gable, K. M. 1973 Conodonts and bio- Admin., Morgantown Energy Res. Ctr., Rep. stratigraphy of the Olentangy Shale (Middle- MERC/CR-77-2, 56 p. Upper Devonian), central and south-central Reidel, S. P. 1975 Bedrock geology of Serpent Ohio. Unpubl. M.S. Thesis, Ohio State Univ., Mound cryptoexplosion structure, Adams, High- Columbus. 90 p. land and Pike Counties, Ohio. Ohio Geol. Surv. Galbraith, R. M., IV 1968 Peripheral defor- Rept. Invest. 95. mation of the Serpent Mound cryptoexplosion , F. L. Koucky and J. R. Stryker 1982 structure in Adams County, Ohio. Unpubl. M.S. The Serpent Mound disturbance, southwestern Thesis, Univ. Cincinnati, Cincinnati. 47 p. Ohio. Amer. J. Sci. 282: 1343-1377. , F. Koucky and A. Jacobs 1975 Struc- Rexroad, C. B. 1967 Stratigraphy and conodont ture of Adams County, Ohio. In: 26th Annu. paleontology of the Brassfield (Silurian) in the Ohio Intercol. Field Conf., Serpent Mound cryp- Cincinnati arch area. Indiana Geol. Surv. Bull. toexplosion structure, p. 30-45. 36. 64 p. Grahn, Y. and S. M. Bergstrom 1985 Chitin- , E. R. Branson, M. O. Smith, C. Sum- ozoans from the Ordovician-Silurian boundary merson and A.J. Boucot 1965 The Silurian beds in the eastern Cincinnati region in Ohio and formations of east-central Kentucky and adjacent Kentucky. Ohio. J. Sci. 85: 175-183. Ohio. Kentucky Geol. Surv. Bull. 2, Ser. 10. 34 Hyde, J.E. 1953 Mississippian formations of P- central and southern Ohio. Ohio Div. Geol. Surv. Rogers, J. K. 1936 Geology of Highland Bull. 51. 355 p. County. Ohio Geol. Surv., part 2. 3: 161 p. Kaufmann, R. F. 1964 The stratigraphy of Schmidt, R. G., A. F. McFarlan, E. Nosow, R. S. 230 E. M. 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Bowman, and R. Alberts 1961 Examination County, Ohio. U.S. Dept. Agri., Series 1932, of the Ordovician through Devonian stratigraphy No. 29, 64 p. and the Serpent Mound chaotic structure area. In: Tillman, J. R. 1970 The age, stratigraphic Guidebooks for field trips, Cincinnati meetings. relationships and correlations of the lower part of Geol. Soc. Amer. p. 259-294. the Olentangy Shale of central Ohio. Ohio J. Sci. Shaler, N. S. 1877 Ohio black shale, Notes on 70: 202-217. the investigations of the Kentucky Geological Weiss, M. P., F. A. Schilling, K. L. Pierce, and Survey during the years 1873, 1874, and 1875. S. A. Ali 1972 Geologic map of the Maysville Kentucky Geol. Surv. Rept. Progress. 3: East Quadrangle, Ohio-Kentucky. U.S. Geol. 169-175. Surv. Geologic Quadrangle Map GQ-1006. Summerson, C. H. 1959 Evidence of weather- Winchell, M. H. 1873 Geology of Wyandot ing at the Silurian-Devonian contact in central County. Ohio Geol. Surv. part 1, 1: 633 p. Ohio. J. Sedimentary Petrology. 29: 425-429. 1874 Reports on the geology of Swinford, E. M. 1983 Geology of the Peebles Ottawa, Crawford, Morrow, , Van Quadrangle, Adams County, Ohio. Unpubl. Wert, Union, Paulding, Hardin, Hancock, M.S. Thesis. Eastern Kentucky Univ., Rich- Webb, Putnam, Allen, Auglaize, Henry, Mercer, mond. 104 p. and Defiance Counties. Ohio Geol. Surv. rept. 2, Taylor, A. E. 1938 Soil Survey of Adams part 1, p. 227-438.