SedimentaryGeology191(2006)89–113 www.elsevier.com/locate/sedgeo Incised valley fill interpretation for Mississippian Black Hand Sandstone, Appalachian Basin, USA: Implications for glacial eustasy – – at Kinderhookian Osagean (Tn2 Tn3) boundary ⁎ David L. Matchen a,b, , Thomas W. Kammer c a WestVirginiaGeologicalandEconomicSurvey,1MontChateauRoad,Morgantown,WV26508,USA b DepartmentofGeologyandGeography,WestVirginiaUniversity,Morgantown,WV26506-6300,USA cDepartmentofGeologyandGeography,WestVirginiaUniversity,Morgantown,WV26506-6300,USA Received9March2005;receivedinrevisedform28January2006;accepted1February2006 Abstract Lower Mississippian strata of east-central Ohio are predominantly fine-grained marine deposits of the Cuyahoga and Logan formations. Within these sediments is the Black Hand Sandstone of the Cuyahoga Formation. The Black Hand Sandstone is a multistory, crossbedded, coarse-grained conglomeratic sandstone. The contact between the Black Hand Sandstone and the subjacentCuyahogaFormationissharpandscoured,withintraclastsoftheCuyahogaFormationincorporatedintothebasalBlack Hand Sandstone. The Black Hand Sandstone was previously thought to represent a distributary channel deposit; however, the combination of lithofacies and architectural elements indicates deposition in a braided stream setting. The Cuyahoga Formation wasdepositedinashallowmarinesetting.TheerosionalbasalcontactoftheBlackHandSandstoneandthejuxtapositionoffluvial andmarinesedimentssuggestsasequenceboundary.ThegeographicdistributionoftheBlackHandSandstonecombinedwiththe evidencefor asequence boundarysuggests deposition inanincised valley. The age of the Black Hand Sandstone is key to inferring the causes of valley incision. The Black Hand Sandstone is nearly devoid of body fossils, necessitating a biostratigraphic analysis of the surrounding Cuyahoga and Logan formations. Analysis indicates the Logan Formation is early Osagean age. Data from the Cuyahoga Formation suggest a Kinderhookian age with a possibletransitiontotheOsageanintheuppermostCuyahogaFormation.ThisconstrainstheageoftheBlackHandSandstoneto the transition at the Kinderhookian–Osagean boundary. RecentreportsindicatelateKinderhookian(Tournaisian,Tn2)Gondwananglaciationbasedupontillitesandsharpexcursionsin stable-isotopecurves.Aglacio-eustaticfallinsealevelisinferredtohavecausedincisionoftheCuyahogaFormation,followedby depositionoftheBlackHandSandstoneandLoganFormationduringthesubsequentsealevelrise.Theassociatedunconformity correlates to the sequence boundary at the Kinderhookian–Osagean boundary in the stratotype area of North America, and the correlative Tn2–Tn3boundaryworldwide, supporting the hypothesisof aglobal eustatic eventatthis time. ©2006Elsevier B.V. All rightsreserved. Keywords:Fluvial;Incisedvalley;Appalachian;Mississippian;Glaciation;Eustasy ⁎ Correspondingauthor.Presentaddress:DivisionofNaturalSciences,ConcordUniversity,Athens,WV24712,USA. E-mailaddress:[email protected](D.L.Matchen). 0037-0738/$-seefrontmatter©2006ElsevierB.V.Allrightsreserved. doi:10.1016/j.sedgeo.2006.02.002 90 D.L.Matchen,T.W.Kammer/SedimentaryGeology191(2006)89–113 1. Introduction sediment from the eroding Acadian highlands (Etten- sohn et al., 2002). By latest Devonian time, the rate of Lower Mississippian strata of the central Appala- subsidence had decreased considerably in the foreland chian basin, which includes eastern Ohio and the basin, which then filled, producing a foreland ramp adjacent areas of western Pennsylvania, West Virginia, system (Castle, 2000). Sediment from the Acadian and eastern Kentucky, represent the final pulse of highlands filled any remaining accommodation space sedimentation from the eroding Acadian highlands and prograded to the west and south towards the (Ettensohnetal.,2002).Theserockscontaindominantly Cincinnati Arch (Matchen and Kammer, 1994). The coarse-grained terrestrial facies in the east and fine- high sediment flux combined with minimal accommo- grained marine facies in the west (Bjerstedt and dation space resulted in a relatively thin, widespread Kammer, 1988). The rocks are diachronous being sheet of interbedded sandstones, siltstones, and shales predominantly Kinderhookian in the east with the that eventually reached as far as the Illinois basin Osagean portion expanding towards thewest (Matchen (Kepferle, 1977). Upper Devonian sediments reached and Kammer, 1994). thicknesses of 1900–3300m in the deep Acadian Within the predominantly marine sediments of foreland basin of eastern Pennsylvania and eastern Ohio lies the anomalously thick conglomeratic Black West Virginia (Faill, 1985). By comparison, Lower Hand Sandstone, which is typically up to 60m thick Mississippian sediments rarely exceed 235m at any and is surrounded on all sides by finer-grained marine location in the study area or surrounding regions sediments. The Black Hand Sandstone lies within the (Dennison and Wheeler, 1975; Harper and Laughrey, Cuyahoga Formation, of which it is a member, and is 1987; Bjerstedt and Kammer, 1988; Brezinski, 1999). always overlain by the Logan Formation. The most recent previous study interpreted the Black Hand 2.2. Stratigraphy Sandstone as a distributary channel deposit within prograding marine deltaic deposits of the Cuyahoga The Mississippian–Devonian boundary is placed at Formation (Bork and Malcuit, 1979). In this paper, we thebaseoftheSunburyShale(Fig.2),aregionalmarker present evidence that the Black Hand Sandstone is throughout the central Appalachian basin (De Witt, younger than the rest of the Cuyahoga Formation and 1970). The top of the Lower Mississippian section is is an incised valley fill composed of braided stream placed at the base of the Meramecian/Chesterian deposits that formed at the end of Cuyahoga MaxvilleLimestone(Smosna,1996),oritsequivalents. deposition and before the overlying marine Logan Lower Mississippian rocks are subdivided into the Formation. Cuyahoga and Logan formations(Fig. 2).Stratigraphic This study has several goals: (1) examine the Black summaries can be found in Holden (1942), Fagadau HandSandstoneindetailandreconsideritsenvironment (1952),Hyde(1953),Szmuc(1957),Wolfeetal.(1962), of deposition; (2) use knowledge of its depositional and Bork andMalcuit (1979). environmenttoplaceitcorrectlywithinthestratigraphic framework of central Ohio; (3) analyze available 2.2.1. Cuyahoga Formation biostratigraphic data to determine the age of the Black The Cuyahoga Formation is a facies mosaic of Hand Sandstone within the context of the surrounding interbedded shale, siltstone, and sandstone 129–161m lithologic units; and (4) use all of this information to thick in east-central Ohio (Fig. 2). It thins southward, recognize changes in relative sea level associated with where along the Ohio River the majority of the Lower deposition of the Black Hand Sandstone and surround- Mississippian section is composed of the Logan ing Lower Mississippian strata of the central Appala- Formation (Holden, 1942; Bork and Malcuit, 1979). chian basin. Both marine invertebrate and trace fossils are common intheCuyahogaFormation, exceptfor theBlackHand 2. Setting SandstoneMember. The absence of regional marker beds and the lateral 2.1. Extent of study area variabilityofstratigraphicunitsmakeslithostratigraphic correlation difficult within the Lower Mississippian The study area includes both outcrops and well section. To deal with this difficulty, a series of logs of the Black Hand Sandstone in east-central Ohio geographic facies were defined by earlier workers (Fig. 1). The Lower Mississippian section in the including the Hocking Valley Facies (in the Hocking Appalachian basin represents the final pulse of Hills south of Lancaster), the Granville Facies, and the D.L.Matchen,T.W.Kammer/SedimentaryGeology191(2006)89–113 91 Fig.1.DistributionofLowerMississippianoutcropinOhio(dottedline)andtheBlackHandSandstone(shaded)inoutcropandinthesubsurface (modifiedfromWolfeetal.,1962).ThegeneralpositionofgeographicfaciesfortheCuyahogaFormationandtheBlackHandSandstonelobes definedbyHolden(1942)andHyde(1953)areindicatedbyarrows.Numberedsquaresrepresentstudylocalities:(1)PleasantHillDam(Szmuc, 1957;UTM17S387863E,4497687E),(2)BlackHandSandstoneGorge,typesection(Hyde,1953;BorkandMalcuit,1979;UTM17S395319E, 4434338N),(3)ChestnutRidgeMetropark(UTM17S349473E,4408011N),(4)Mt.Pleasant(UTM17S363329E,4398434N),(5)Rockbridge NaturePreserve(UTM17S370971E,4381772N),(6)CantwellCliffs(UTM17S364460E,4378300N),(7)ConklesHollow(UTM17S364526E, 438399N),(8)OldMan'sCave,LowerFallsandCedarFalls(UTM17S367004E,4365945N,(9)AshCave(UTM17S367009E,4362277N). Localities6–9arelocatedinHockingHillsStatePark. TobosoFacies(Holden,1942;Hyde,1953;Wolfeetal., Mississippian (Holden, 1942). Like the Cuyahoga 1962) (Figs. 1 and 2). This system is cumbersome and Formation, the Logan is a facies mosaic of shaly and outdated,butitisusefulforlinkingthisstudytoearlier sandy marine stratigraphic units. The most distinctive work.ThelobesoftheBlackHandSandstonearenamed unit,andmostimportantforcorrelationpurposesisthe for these facies (Fig. 1). Berne Member (Bork and Malcuit, 1979). The Berne Based on field evidence, the composition of the Member consists of reworked pebbles from the Black Black Hand Sandstone ranges from quartz arenite to Hand Sandstone, and contains marine invertebrate sub-litharenite. The majority of the pebbles within the fossils. Where the Black Hand Sandstone is absent, conglomeratic portions are quartz; less than 10% are the Cuyahoga and Logan formation contact is recog- feldspars. nized by the presence of the Berne (Bork and Malcuit, 1979).TheBernepinchesoutbeyondthedistributionof 2.2.2. Logan Formation theBlackHand Sandstone. TheLoganFormationisa79–85-m-thicksiliciclastic The Rushville Member is at the top of the Logan unit(Szmuc,1957)(Fig.2).InsouthernOhio,itisupto Formationandisashalymudstone,withathincrinoidal 150m and comprises the majority of the Lower limestone at its base (Thompson et al., 1971). 92 D.L.Matchen,T.W.Kammer/SedimentaryGeology191(2006)89–113 Fig.2.StratigraphicnomenclatureforLowerMississippianstratawithinthestudyarea(Holden,1942;Hyde,1953;Wolfeetal.,1962;Szmuc,1970). LocationsofgeographicfaciesandBlackHandSandstonelobesareshowninFig.1. Previously, it has been treated as a separate formation, 3. Methodology but the Rushville is considered to be a member of the Logan because of its similar lithology to the Vinton Depositional environments of the Black Hand Member,anditsverylimitedextentbothvertically(8m) Sandstone were evaluated via measured profiles con- and areally (one locality). The conodont study by structedforHanover,CantwellCliffs,OldMan'sCave, Thompson et al. (1971) provides a youngest possible and Chestnut Ridge. Supplementary sections included age for the Logan Formation. Ash Cave, Cedar Falls, Conkles Hollow, Mt. Pleasant and RockbridgeState Nature Preserve(Fig. 1). 2.3. Regional structure Theanalysiswascarriedoutthroughconstructionof lateralprofileswithconcentrationonboundingsurfaces Structure contour maps on the top of the latest and lithofacies. This process was developed by Allen Devonian Berea Sandstone show a broad structural (1983) and later modified (Miall, 1985; Luttrell, 1993; basin(Fig.3).EasternOhioliesonthewesternflankof Yu et al., 2002; Miall and Jones, 2003). The most thisbasinwithlowstructuraldip(<1°)totheeast.The commonmeansofanalysisisbyphotomosaic;however, current basin morphology is the result of Alleghenian- thelocationofthesesectionswithindeepnarrowgorges age tectonism that occurred following deposition of in the Hocking Hills precluded the construction of Lower Mississippian strata (Faill, 1998). Isopachs for suitable photomosaics. Instead, profiles were produced theLowerMississippianshowarangeofthicknessfrom by combining closely spaced vertical sections into lessthan60malongtheeasternflankofthebasintoits horizontal profiles. greatest thickness over 240m along the outcrops of Paleocurrentdataareparticularlydifficulttoacquire centralOhio (Fig.4). from the Black Hand Sandstone. The paucity of three- This distribution is the combined result of tectonic dimensional surfaces and the coarse-grained nature of activity and erosion. There was likely uplift to the east the sandstone obliterate bedding details. Estimates of of the study area, which was partly emergent during paleocurrent direction based upon bed orientation are theEarly Mississippian (Bjerstedt and Kammer, 1988). noted on the profiles. In some cases it was possible to This uplift may have contributed to the generally thin identify only a bi-directional orientation of flow from Lower Mississippian succession in West Virginia. The channel-fill deposits or planar crossbeds, these are study area was apparently unaffected by this activity displayed on the outcrop profiles as double-headed as the structure contour map shows no local evidence arrows. The goal of paleocurrent analysis was to for uplift (Fig. 3). The relatively thick Lower determine the flow orientation in relation to the trend Mississippian succession in central Ohio was likely ofthe Black Hand Sandstone (Fig.1). preserved in a region generally unaffected by tectonic Thereare few fossils, terrestrial ormarine, available uplift. for direct determination of the age of the Black Hand D.L.Matchen,T.W.Kammer/SedimentaryGeology191(2006)89–113 93 Fig.3.StructuremaponthetopoftheBereaSandstoneinsoutheasternOhio,westernPennsylvania,andWestVirginia.Contourintervalis100ft (30m);indexcontoursevery500(150m)ft.WelldatafromWestVirginiaandOhiogeologicalsurveys. Sandstone. The surrounding Cuyahoga and Logan their ranges from the Cuyahoga and Logan formations formations contain diverse suites of marine inverte- were evaluated in light of their currently known brates,allowingforanindirectagedeterminationforthe distributions outside of Ohio rather than simply Black Hand Sandstone. Reports of fossil species and accepting the biostratigraphic conclusions of previous 94 D.L.Matchen,T.W.Kammer/SedimentaryGeology191(2006)89–113 Fig.4.LowerMississippianisopachofthesameregioninFig.3.BaseofthesectionisplacedatthecontactoftheBereaSandstoneandSunbury Shale.TopofthesectionisplacedatthecontactoftheLowerMississippiansiliciclasticsandtheUpperMississippiancarbonates.Contourintervalis 50ft(15m);indexcontoursevery200ft(60m).MaximumextentofWestVirginiaDomeisshown,inlightgray,asarethetrendsfortheWarfieldand BurningSpringsanticlines.NotethatsomeofthethickestsectionsareinsoutheasternOhio.WelldatafromWestVirginiaandOhiogeological surveys. D.L.Matchen,T.W.Kammer/SedimentaryGeology191(2006)89–113 95 Ohio studies. No new primary data were collected for surfaces are common within this association. Many this study because there are several previous studies of scoursareconcave-up,andrestrictedtoasingleoutcrop, macroinvertebrates, and we were unable to find any are0.5mto5minwidthand0.1mto1mthick.Larger, faunas not previously described. Data from all previ- outcrop-wide scour surfaces are also common. These ouslypublishedstudiesofbothinvertebratesandspores surfaces display strong relief, are broadly concave were analyzed to create an updated synthesis based on upwards, and can be traced across entire outcrops, but the current biostratigraphic literature for the Lower cannot be traced from one outcrop to the next. These Mississippian of North America and Europe. surfaces are commonly overlain by lithofacies Gi/Gm and grade upwards into lithofacies Sp and St. Only 4. Lithostratigraphy fragmentary plant fossils were found within the association. Thelithofaciesassociations definedherein(Table1) The hummocky sandstone association is best correspond to stratigraphic units identified by previous expressed in the Fairfield Member. The primary workers. The crossbedded-conglomeratic lithofacies is componentoftheassociationishummockycrossbedded the Black Hand Sandstone, whereas the hummocky sandstone (lithofacies Shcs) with minor amounts of sandstone and the siltstone and shale associations lithofacies Sp and Sr. A few trace fossils, including representdifferentportionsoftheCuyahogaFormation. Scalarituba, arepresent. Planar and trough crossbedded (Sp and St) sand- The siltstone and shale association can be observed stones (Fig. 5A and E) and massive gravel (Gm) (Fig. in many places in the Hocking Hills, generally in the 5B)dominatethecrossbedded-conglomeraticsandstone deepest portions of the gorges below the crossbedded- association. Other lithofacies include massive gravel conglomeratic sandstone association. The primary withintraclasts(Gi),laminatedfines(Fl),ripplebedded lithofacies are Fl and Sh. Beds are thin and parallel, sandstone (Sr) and horizontally bedded sandstone (Sh) sandstones are finer-grained than in other associations. (Fig. 5D), which are rare. Conglomeratic sandstone is Abundant trace fossils include Teichichnus, Pelecypo- scattered throughout the association. Within lithofacies dichnus, Paleophycus, Scalarituba and Rusophycus. SpandSt,conglomeraticmaterialiscommonlyfoundat Marine body fossils have been reported (Hyde, 1953, the base of individual beds that fine-upwards. Scour p. 88; Franklin, 1961). Table1 LithofaciesoftheCuyahogaFormation,includingtheBlackHandSandstone Facies Lithofacies SedimentaryStructures Interpretation Shape Frequency Lithofacies ⁎ Code Association Gm MassiveGravel Primarilystructureless;poorly Channellags, Scoop-shaped Common CCS preservedtroughcrossbedding gravelbars israre Gi Gravelwithintraclasts Massiveconglomeratewith Lag/channel Scoop-shaped Commonatbase CCS largeintraclasts slump,scour ofBlackHand; rareelsewhere St Medium-coarsegrained Troughcrossbeds Dunes Sheet Common CCS sandstone Sp Medium-coarsegrained Planarcrossbeds Transverse Sheet Common CCS;HS sandstone bars Sh Fine-coarsegrainedsandstone Horizontallamination Floodplain, Sheet Rare CCS;SS waningflow? Shcs Medium-coarsegrained Hummockycrossbedding, Shallow Sheet OnlyatChestnut HS sandstone,locallypebbly, rarebasalscour marine, Ridge interbeddedshale shoreface Sr Medium-coarsegrained Thinbedded,rippled,horizontal Floodplain, Sheet Rare CCS;HS sandstone andverticalburrows,smallshale exposure intraclasts surface? Fl Fine-grainedsandstone, Raretracefossils,horizontal Waningflood Sheet VeryRare;common CCS;SS siltstone,mudstone laminations deposits inCuyahoga ⁎CCS–Crossbedded-conglomeraticsandstone;HS–HummockySandstone;SS–SiltstoneandShale;BOLD=primaryconstituent,NORMAL= minorconstituent. 96 D.L.Matchen,T.W.Kammer/SedimentaryGeology191(2006)89–113 Fig.5.(A)LithofaciesSt/SpfromCantwellCliffsunitofHockingHillsStatePark,Ohio.Photocorrespondstounit5inFig.12.Author(DLM)is 1.8mtall.(B)Gm/GifromConklesHollowStateNaturePreserve,Ohio.PhotoisatthebaseoftheBlackHandSandstone;markeris13cmlong.(C) Large-scaleSt:CedarFallsunitofHockingHillsStatePark,Ohio.Outcropisapproximately30mtall.(D)LithofaciesFlandShfromCantwellCliffs unitofHockingHillsStatePark,Ohio.Floccursintheerodedrecesses.Horizontalbedshavelimitednumbersofsmalltracefossils.Sp/Stunit overliesthehorizontalsection.Author(DLM)issittingonunit2ofFig.12.OverlyingSp/Stisinunit3ofFig.12.(E)ElementCH,largecomposite channelfill,AshCaveunit,HockingHillsStatePark,Ohio.ScoursurfaceisatbaseofoverhangwherethinlybeddedSp/Stisoverlainbythickly beddedGm,Sp,andSt.Personatleftis1.7mtall.(F)Large-scalelateralaccretiondeposits,lithofaciesSp,Logan,Ohio(UTM17S,376014E, 4378834N);actualdepositionaldipshownasregionaldipislessthan1°. 4.1. Contacts and stratigraphic relationships of continuous exposure. The outcrops in question are a series of individual, isolated exposures between Black The lateral contact between the Black Hand Sand- Hand Gorge (Wolfe et al., 1962) and Granville, Ohio stoneandtheCuyahogaFormationisnotexposedandis (Bork and Malcuit, 1979). Sandstones in these expo- subject to speculation and interpretation in the absence sures are either coarse-grained to conglomeratic (Black D.L.Matchen,T.W.Kammer/SedimentaryGeology191(2006)89–113 97 Hand Sandstone), or fine- to very fine-grained inter- throughtheunderlyingFairfieldMember.Theoverlying bedded with siltstone and shale containing marine lithofaciesisprimarilyGi,andtheunderlyingprimarily fossils (Cuyahoga Formation). In a few instances, thin Fl.Thesharp,steppedcontact,combinedwithabundant (0.5m), coarse-grained sandstones are reported 18m intraclasts of Fl incorporated into the overlying Gi, belowthetopoftheCuyahogaFormation(Hyde,1953; suggeststhatthebasalcontactbetweentheBlackHand pp. 70–71; Franklin, 1961). This relationship was Sandstone and the Fairfield Member of the Cuyahoga inferred to be gradational, with increasingly finer Formation is erosional rather than gradational where it grained sandstone encountered farther from the Black can be observed. Hand. Examination by the authors suggests that the change in grain-size is abrupt and immediate. Sand- 4.2. Outcrop descriptions and profiles stones are either coarse-grained or fine-grained, there does not appear to be a gradational transition. This 4.2.1. Cantwell Cliffs suggests that coarse-grained conglomeratic sediments The crossbedded-conglomerate assemblage domi- characteristic of the Black Hand Sandstone are segre- nates exposures at Cantwell Cliffs. The siltstone and gated from the fine-grained marine sediments of the sandstone assemblage (Fl and Sh) can be observed in CuyahogaFormation. the lowest parts of the gorge but the contact between Hyde (1953, pp. 88–89) suggested that the basal associations is concealed. The exposure is subdivided contact of the Black Hand Sandstone is a regional intosixstratigraphicunits(Fig.7).Units1,3and6are erosion surface. At Conkles Hollow and Old Man's dominatedbylithofaciesSpandSt.Unit2iscomposed Cave, where the contact is exposed, two features are of lithofacies Sh and Fl. Tool marks and a few evident. The first is the presence of locally abundant undifferentiated horizontal burrows can be seen on the large intraclasts at the base of the Black Hand base of some beds, and one bed within the section Sandstone (Fig. 5B). Intraclasts observed by the containsnumerousnarrowverticalburrowsidentifiedas authors are flat, angular, and coherent, with a a small version of Arenicolites. Also present is an maximum linear dimension of 1m, and are apparently unusualepichnialmoldwithannulationsthatresembles derived from lithofacies Fl. These intraclasts can only a mirror image of Arthrophycus. Unit 4 is composed be traced a few meters upwards into the Black Hand primarily of lithofacies Gm deposited within small where they disappear. channels, with minor amounts of lithofacies Sp and St. The second feature is the “stepped” nature of the Unit 5 comprises large-scale bedsets of lithofacies Sp contact(Fig.6).IntwoexposuresnearOldMan'sCave (Fig.5A). (Fig.1,locality8),thecontactisparalleltothebedding of the underlying Cuyahoga Formation. As the surface 4.2.2. Old Man's Cave and lower falls istracedalongtheoutcrop,thecontactsharplytruncates The gorges around Old Man's Cave provide several the underlying rock as deep as 0.5m, then parallels kilometersoflateralexposuresuitableforanalysisofthe bedding for 9.5m to 14.5m, and again cuts downward uppermost Black Hand Sandstone; unfortunately, Fig.6.ContactbetweenBlackHandSandstoneaboveandFairfieldMemberbelowatLowerFallsintheOldMan'sCaveunitofHockingHillsState Park,OhioshowingthreestepserodedintotheFairfieldMemberbedding.(A)Un-retouchedphoto.(B)Boundarymarkedbetweenthetwounitsto 98 D.L.Matchen,T.W.Kammer/SedimentaryGeology191(2006)89–113 Fig. 7. Fence diagram of the Black Hand Sandstone outcrop at Cantwell Cliffs unit of Hocking Hills State Park, Ohio (UTM 17S 364460E, 4378300N).Sectionwasmeasuredanddescribedfollowingalongthe“baseofoutcrop”.Smallarrowsindicateeitherpaleoflowdirection(single head)ororientation(doublehead).Paleoflowindicatorsarebaseduponindividualmeasurements.Darkgraycolorshighlightthesandybedform architecturalelement,whichareinterpretedtobebarcomplexes. Fig.8.CompositeverticalsectionsummarizingseveralprofilesoftheBlackHandSandstoneatOldMan'sCaveunitofHockingHillsStatePark, Ohio(UTM17S367004E,4365945N).Boundariesbetweenindividualprofilesaremarkedbyheavy,dashedlines.Sectionissubdividedintofour stratigraphicunits,threewithintheBlackHandSandstone.EachunitwithintheBlackHandSandstoneisboundbyabasalscoursurface.Thescour surfaceisoverlainbylithofaciesGi.Withineachunit,GigradesupwardsintolithofaciesSpandSt.Scoursurfacesarebroadlyconcaveupwardsand cannotbetracedbetweenoutcrops.Insomecases,thesesurfacesappeartobebasalchannelscour,inothers,theymayrepresentmorewidespread erosionwithbasalrelief.Nohorizontalscaleimplied.DarkgraycolorcorrespondstosiltstoneandshaleoftheCuyahogaFormation,lightergray colorcorrespondstotheconglomeraticsandstoneoftheBlackHandSandstone.