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New Map of the Surficial Geology of the Lorain and Put-in-Bay 30 x 60 Minute Quadrangles, Ohio
ByEdwardM.Swinford,RichardR.Pavey,andGlennE.Larsen
OhioDepartmentofNaturalResourcesDivisionofGeologicalSurvey2045MorseRoadBldg.C-1
Columbus,OH43229Telephone:(614)265-6473
e-mail:[email protected]
ABSTRACT
A map depicting the surficial geology of the Lo-rainandPut-in-Bay30x60minute(1:100,000-scale)quadrangleshasbeenproducedbytheOhioDepartmentofNaturalResources,DivisionofGeologicalSurvey.Existing surficial maps at various scales document the uppermost surficial lithology of the area. The new map depictsunderlyinglithologiesfromthesurfacedowntobedrockforuseingeotechnicalstudies,land-useplan-ning,andmineralexploration.Toproducethenewmap,surficial deposits were mapped at 1:24,000 scale to create thirty-six7.5-minutequadrangles,whichwerecompileddigitallyusingG�Stechnologyandconvertedintoafull-color, print-on-demand, 1:100,000-scale, surficial-geologymap.ThemapincludesallorportionsofErie,Huron,Lorain,Lucas,Sandusky,andSenecaCountiesinnorth-central Ohio. Data sources include field mapping, countysoilsurveys,OhioDepartmentofTransportationandOhioEnvironmentalProtectionAgencyboringlogs,engineeringlogs,ODNRwater-welllogs,theses,andpublishedandunpublishedgeologicandhydrogeologicreports.Mappolygonswereattributedusingastack-unitdesignatorthatindicatesthethicknessandstratigraphicsequenceofmajormaterialunits(i.e.,till,gravel,sand,silt,andclay),fromthesurfacedowntoandincludingtheuppermostbedrockunit.Severalregionalmaterialtrendsareapparentonthemap,includinglargeareasoflacus-trineclayandsiltlandwardofLakeErie,theprominenceofshallowbedrockthatparallelstheLakeErieshore-line,adeltaicsequencedepositedduringhigherlevelsofwaterofancestralLakeErie,thelocallywidespreadandthickorganicandmarldeposits,andtheexpanseofWisconsinan-agetillthatmantlesthesurfaceinmostofthequadrangles.Thetextexplainshowtoreadthemap,provideslithologicdescriptionsofmappedglacialandbedrockunits,andoffersotherexplanatoryinformation.AG�Sgeodatabasecontainsspatialinformationoneachpolygonanddataattributesofthestackunits,allofwhich
canbequeriedonthebasisofmaterialtypesandthick-nessesforrapidgenerationofderivativemaps.Potentialqueriesforderivativemapsmightincludeisolatingclayand silt deposits for the identification of potential geohaz-ards,identifyingsandandgraveldepositsforaggregateexploration,ordepictingareasofthickglacialtillfortheidentification of potentially favorable solid-waste disposal sites.MappingwaspartiallyfundedbytheU.S.Geologi-calSurvey,NationalCooperativeGeologicalMappingProgram,STATEMAPcomponent.DigitalcompilationwasmadepossiblebyfundingfromtheCentralGreatLakesGeologicMappingCoalition.
INTRODUCTION
�n1997,theOhioDepartmentofNaturalResources(ODNR),DivisionofGeologicalSurvey(OGS)beganworkonalong-rangegoaltoproducereconnaissance-stylethree-dimensional surficial-geology maps for all of Ohio. The plan to attain this goal focuses on completing surficial mappingofmajorurbanareasandhighlypopulatedcor-ridors first in order that a majority of Ohio’s 11.4 million citizens (2003 Census estimate) can benefit from modern surficial-geologic maps for land-use planning, resource exploration,hydrogeologicinvestigations,andgeohazardidentification. Less populated glaciated portions of Ohio willthenbemappedfollowedbyallofunglaciatedOhio.Todate,thisefforthasresultedinthecompletionofthree-dimensional surficial geology maps for 45% of the state’s landarea(354of7887.5-minutequadrangles).
Existing Maps
Priortorecentmappingefforts,glacial-geologymapsofOhioweregeneralized,two-dimensional,geomorphi-callyorientedproductssuchasthe1:500,000-scaleQua-ternary geology of Ohio(Paveyandothers,1999)(Figure1) and other published/open-file glacial-geology maps (generallyat1:62,500-scale)for27countiesinnorth-
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eastern,central,andsouthwesternOhio(Figure2).Theseolder maps were constructed using a combination of field investigations,geomorphicanalysis,andexistingsoilsmaps. Describing the entire surficial lithologic interval fromsurfacedowntotopofbedrockwasnotattemptedin this map set, as only the topmost unit was defined. However,existingglacialmapswereusedasabasisforselectingboundariesoftheuppermostunitsduringtheremappingeffort.WhilesuchmapscanprovidegeneralinformationonthedistributionofmaterialsdepositedbyPleistoceneglacialandpostglacialevents,themapsarewhollyinadequateforthecharacterizationandassessmentof unconsolidated materials at depth. The new surficial mappingeffortaddsthethird-dimensioncomponentofvariablelithologiesatdepthandtheirthicknesses.
New Glacial Mapping Program
In 1996, OGS conducted a survey of surficial-geol-ogymapusersinOhiotodeterminethekindsofmapinformationtheyrequirefortheirneeds.Themajorityofrespondentstothesurveyquestionnaireindicatedastrongneedforcomprehensive,three-dimensional,surficial-geology maps that depict all deposits and their thicknessesdowntoandincludingtheuppermostbedrockunit.�nrecognitionofthisneedformorecomprehensivesurficial-geology data, OGS implemented a program to produce reconnaissance-style, three-dimensional, surfi-cial-geologymapsat1:100,000scalefortheentirestate.
Themappingeffortisbasedonathree-dimensionalmapping method first implemented by the Illinois State GeologicalSurvey(e.g.,BergandKempton,1988).TheIllinois surficial mapping model used established glacial stratigraphicnames(abbreviated)thatare“stacked”asstratigraphicunitswouldappearwithinthepolygontheyare defining. Ohio’s surficial mapping effort modified the stack-unit concept to reflect lithologies of materials rather thanglacialstratigraphicnamesandintroducedadditionalconstraintsonunitthickness,allowingeachareatobemappeddowntothebedrocksurface.
To date, reconnaissance-style, 1:100,000-scale surfi-cial-geology maps have been completed for fifteen of the thirty-four30x60minutequadrangleareasofthestate.Anestimated8.9millionOhiocitizensnowhavethree-dimensional surficial mapping for various societal needs, includingmineral-resourceexploration,land-useplan-ning, geohazard identification, and environmental protec-tion. A database that contains the surficial-unit lithology, thickness,anddistributioninformationonthousandsofpolygonsshownonthemapcanbequeriedtoproducederivativemapsthatidentifygeologyofsocietalinterestsuchasmineralresourcesorgeohazards.
ThenewmappingprogramislargelyfundedbyataxonthemineralindustriesofOhio,includingoilandgas,withadditionalfundingbytheU.S.GeologicalSurvey(USGS)STATEMAPprogram,theCentralGreatLakesGeologicMappingCoalition,andtheU.S.EnvironmentalProtectionAgencyNonpoint-SourcePollutionProgram.
Figure 1.MapshowingtheglacialdepositsofOhio.
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Figure 2.Mapshowingcountiesforwhichglacial-geol-ogy maps are available as published or open-file reports fromtheOhioDepartmentofNaturalResources,Divi-sionofGeologicalSurveyoraspartofDivisionofWaterbulletins.
Purpose and Justification
Three-dimensionalmappingofOhio’sglacialgeol-ogyinurbanizedorrapidlyurbanizingareas(Figure3)isahighpriorityforOGS.Todate,OGShascompleted1:100,000-scale three-dimensional surficial-geology maps fortheAkron,Canton,Cincinnati,Cleveland,Columbus,Dayton, Lancaster, Springfield, Toledo, and Youngstown metropolitanareas.Thesemapshavebeenusedby
1.privatesandandgravelexplorationists,2.theOhioEPAforwaste-facilitysitinganalysisand
contaminated-siteevaluations,3.regionalplanningcommissionsforland-useplan-
ning,4.collegesanduniversitiesasteachingtools, 5. private geotechnical firms for site evaluations, and6.theOhioDepartmentofTransportation(ODOT)
forshallowsubsurfaceevaluations.
Majormetropolitanareasandtheirsurroundinginter-statehighwaycorridors(especiallyinglaciatedareasofthestate)areexperiencingmajoreconomicdevelopmentandrelatedpopulationgrowth.Land-useplanningandin-dustrial development in these corridors will benefit greatly fromthethree-dimensionalmappingthisoveralleffortwill provide. OGS’s long-range plan for surficial mapping inOhioistocompletestatewidemappingofthedenselypopulatedmajormetropolitanareaswheremostOhioanslive and work; surficial mapping of densely populated areasinglaciatedOhioiscompleteorinprogress.When
thisphaseofmappingiscomplete,theOGSmappingeffortwillfocusonrapidlydevelopinginterstatehighwaycorridorsinglaciatedportionsofnorthernandwesternOhio,suchasthe�nterstate-71corridorinnorthernOhio,andthe�nterstate-75corridorinwesternOhio.AftercompletionofthemajorportionsofglaciatedOhio,map-pingeffortswillfocusonthelargelyunglaciatedterrainofsoutheasternOhio,wherethickdepositsofoutwashandlandslide-proneglacio-lacustrinesedimentsoccupylargeportionsofformerandpresent-dayrivervalleys.
METHODS
Construction of the Lorain/Put-in-Bay Map
OGShascompiledamapthatshowsthethree-di-mensional framework of the surficial geology, from the surfacedowntoandincludingtheuppermostbedrockunit,fortheLorain/Put-in-Bay30X60minutequad-rangles(Paveyandothers,2005)locatedinnorth-centralOhio(Figure4).GeologistsattheOGSdevelopedaneasy-to-readformat,describedbelow,thatdepicts1)thetypeofdeposit,2)thethicknessrangeofthedeposit,3)theverticalsequenceofdepositsinthemaparea,and4)thebedrocklyingbeneaththedeposit.
Map Format Guidelines
• Mapcolorsdepicttheuppermostcontinuousunitandareintendedtoassistusersinvisualizingthesurfacegeologyofthearea(e.g.,greens=till,redsandoranges=sandand/orgravel,bluesandpurples=siltandclay).
• Polygons or map-unit-areas define boundaries oftheverticalsequenceindicatedbystack-unitdescriptionsthatarecomposedofletters,numbers,and modifiers.
• Letters,numbers,andmodifiersarearrangedinstackstodepicttheverticalsequenceoflithologicunitsforapolygon.Simpleabbreviationsareusedforeaseofreading.
° Letterabbreviationsindicatelithology(e.g.,SG=sandandgravel,T=till,L=silt).
° Numbersindicateaveragethicknessintensoffeet(e.g.,2=20ftthick,+or-50%).
° Modifiersindicateaerialextent.Aminus{-}signfollowinganumberindicatesthemaxi-mumthicknessforthatunitinareaslikeburiedvalleysorridges.Parentheses()indicatethataunithasapatchyordiscontinuousdistributioninthatmap-unitarea.
Datausedtocreatethemapwerecollectedfromnumerous sources. The concentration of surficial data is greatestnearthesurfaceanddecreaseswithdepth.U.S.
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DepartmentofAgriculture,SoilConservationServicemaps, which describe the top 5 ft of surficial materials, providedaninitialguidetomap-unitareadelineation.These areas were modified through interpretation of localgeomorphicsettingsandotherdatathatindicatedachangeinthetypeofdepositatdepth,suchasODNRwater-welllogs,ODOTandOhioEPAtest-boringlogs,engineering-boringlogs,theses,andpublishedandunpub-lished geologic reports, maps, field notes, and seismic-refraction profiles. These data also provided the basis for lithologicunitdescriptions,whichsummarize,asaccu-ratelyaspossible,recognizedassociationsofgeneticallyrelated materials. The total thickness of surficial deposits wascalculatedbysubtractingfromland-surfaceelevationthe bedrock elevation found on OGS open-file bedrock-topographymaps,whichareavailableforeach7.5-minutequadrangleinthemaparea.Thebedrockunitsweresum-marizedfromOGSbedrock-geologymaps,whicharealsoavailableforeach7.5-minutequadrangle.Land-surfacetopographyshownonthebasemapwaspreparedlargelyfromdataderivedfromtheU.S.GeologicalSurvey’sNationalElevationDataset.
Thepolygonandstack-unitinformationwerehand-drawnatascaleof1:24,000onMylaroverlaysregistered
to1:24,000-scale7.5-minutequadrangles.TheseMylarmapswerescanned,thelineworkwascaptured,andpoly-gons were created. Stack-unit information that identifies the surficial geology from surface down to and including bedrockforeachpolygonwasinputintoageodatabase.Severaliterationsofqualitycontroltookplacetoensurethatlineworkbetweenquadranglesandstack-unitas-signmentswereedgematched.Thecolormapconsistingofpolygonsandstack-unitindicatorswasgeneratedandincludedbasemapinformationandshadedelevationforthe final map product. Other map elements include an ex-planationofhowtoreadthemapalongwithaschematiccross-section,detailedlithologicunitdescriptions,refer-encesofsourcesused,alocationmapofthequadrangle,anindexmapthatshowsmappingresponsibility,andamapcolorkey.
RESULTS
Several regional surficial-material and bedrock-geol-ogytrendsappearonthemap.LargeareasoflacustrineclayandsiltdepositedduringhigherlevelsofancestralLakeErieweremapped;theydominatethesurfacema-terialslandwardofLakeErieinthecentralandwestern
Figure 3.MapshowingthepopulationofOhiobycensustractandtheoutlinesofareaswith completed three-dimensional surficial mapping. Sources: the U.S. Bureau of the CensusandtheOhioDepartmentofDevelopment.
portionsofthemap.ShallowbedrockparallelsportionsoftheLakeErieshorelineandrangesfromeconomicdepositsoflimestoneinthewesttoshaleandeconomicdepositsofsandstoneintheeast.AdeltaicsequenceofsandandsiltdepositedduringhigherlevelsofwaterofancestralLakeEriecoversalargeareainthecentralpor-tionofthemap.Locallywidespreadandthickorganicandmarldeposits,formedfromtheprecipitationofcalciumcarbonatefromlocalsprings,weremappedinthenorth-westernportionofthemap.Wisconsinan-agetill,presentasridgeandgroundmorainedepositsupto120ftthick,mantlesmostofthesouthernportionofthemap.
Map Products
The final Lorain and Put-in-Bay 30 x 60 minute map willbereleasedtothepublicinthreeformats:1)afull-colorpaperformat,print-on-demand,1:100,000-scale,surficial-geology map; 2) a digital format on CD-ROM disk, which includes database files, base-map files, metadata files, and a PDF file of the original map; and 3)an�nternetMapSystemproductontheOGSwebsite(http://ohiodnr.com).
Derivitive Map Products
TheLorain/Put-in-Bay30X60minutemapisadigi-talproductthatcanbemanipulatedtoisolatevariousgeo-logiccomponents.Polygonsandstack-unitinformationare in ArcGIS geodatabase file format and can be sorted bylithologyandthicknesstocreatederivativemapsforavarietyofuses.Figure5isaderivativeproductshowingpolygonsthatcontainlayersofsand,sandandgravel,orgravelwithathicknessgreaterthan20ft.Mineralcompaniescouldusethisstyleofmaptodelineateareasthatcontaineconomicdepositsofnaturalaggregate(sandandgravel)forpotentialexploration.Water-welldrillerscouldusethismaptodelineateareasofthick,coarsesandandgraveldepositsthatmaycontainanabundantwatersupply.
Otherderivativemapproductscanbeextractedfromthedigitaldatatosuitmanypurposes.Examplesincludederivativemapsthatshowareasofthicktill,forpotentialplacementofasolid-wastedisposalfacility,orareasofsurfacesilt,clay,ororganicmaterialsthatcouldindicateconstructiongeohazardssuchaslandslidesandunstablenear-surfacematerials.
Figure 4. Surficial geology map of the Lorain and Put-in-Bay 30 x 60 minute quadrangles located innorthcentralOhiotobepublishedasafull-color,print-on-demandpapermapandreleasedonCD-ROMdiskandasaweb-basedinteractivemap.
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Figure 5.Digitallyderivedmap(extractedfromtheoriginalstack-unitinformation)showingareasthathavesand,sandandgravel,orgravelwithathicknessgreaterthan20ftintheLorainandPut-in-Bay30x60minutequadrangles.
REFERENCES
Berg,R.C.,andKempton,J.P.,1988,Stack-UnitMappingofGeologicMaterialsin�llinoistoaDepthof15Meters:�l-linoisStateGeologicalSurveyCircular542,23p.,4pl.
Pavey,R.R.,Goldthwait,R.P.,Brockman,C.S.,Hull,D.N.,Swinford,E.M.,andVanHornR.G.,1999,QuaternaryGeologyofOhio:OhioDivisionofGeologicalSurveyMapNo.2.
Pavey,R.R.,Larsen,G.E.,Swinford,E.M.,andVorbau,K.E.,2005, Surficial Geology of the Lorain and Put-in-Bay 30 X60-minuteQuadrangles:OhioDivisionofGeologicalSurveyMapSG-2Lorain/Put-in-Bay,scale1:100,000.
