thickness trends and sequence authors stratigraphy of …jte2/references/link158.pdf · devonian...

AUTHORS

Gary G Lash Department of GeosciencesState University of New York Fredonia FredoniaNew York 14063 Lashfredoniaedu

Gary Lash received his BS degree from KutztownState University (1976) and his MS degreeand PhD from Lehigh University (1978 and 1980respectively) He has worked on various as-pects of the Middle and Upper Devonian shalesuccessions on western New York Prior tothis work Lash was involved in stratigraphic andstructural investigations of thrusted CambrianndashOrdovician deposits of the central Appalachians

Thickness trends and sequencestratigraphy of the MiddleDevonian Marcellus FormationAppalachian BasinImplications for Acadianforeland basin evolutionGary G Lash and Terry Engelder

Terry Engelder Department of Geosci-ences Pennsylvania State University UniversityPark Pennsylvania 16802 jte2psuedu

Terry Engelder a leading authority on the Mar-cellus gas shale play received his BS degreefrom the Pennsylvania State University his MSdegree from Yale University and his PhD fromTexas AampMUniversity He is currently a professorof geosciences at Penn State and has previ-ously served on the staff of the US GeologicalSurvey Texaco and Lamont-Doherty EarthObservatory He has written 150 research ar-ticles many focused on Appalachia and a bookStress Regimes in the Lithosphere

ACKNOWLEDGEMENTS

We thank AAPG reviewers Ashton EmbryBerry Tew Charles Boyer II Ursula Hammesand Karen Glaser for their efforts to improvethis paper Chief Oil and Gas LLC the New YorkState Energy Research and Development Au-thority the Reservoir Characterization GroupNew York State Museum the Ohio State Geo-logical Survey the Pennsylvania Geological Sur-vey and Appalachian Fracture Systems sup-ported various aspects of this study Randy Bloodis acknowledged for the many field discussionsrelated to the lithostratigraphy and sequencestratigraphy of the Middle and Upper Devonian

ABSTRACT

Analysis of more than 900 wireline logs indicates that theMiddle DevonianMarcellus Formation encompasses two third-order transgressive-regressive (T-R) sequencesMSS1 andMSS2in ascending order Compositional elements of the MarcellusFormation crucial to the successful development of this emerg-ing shale gas play including quartz clay carbonate pyrite andorganic carbon vary predictablywithin the proposed sequence-stratigraphic framework Thickness trends of Marcellus T-Rsequences and lithostratigraphic units reflect the interplay ofAcadian thrust-load-induced subsidence short-term base-levelfluctuations and recurrent basement structures Rapid thick-ening of both T-R sequences especially MSS2 toward thenortheastern region of the basin preserves a record of greateraccommodation space and proximity to clastic sources earlyin the Acadian orogeny However local variations in T-R se-quence thickness in the western more distal area of the basinmay reflect the reactivation of inherited Eocambrian basementstructures including the Rome trough and northwest-strikingcross-structural discontinuities induced by Acadian plate con-vergence Episodes of block displacement locally warped thebasin into northeast-southwestndashtrending regions of starved sedi-mentation andor erosion adjacent to depocenters in which re-gressive systems tract deposits were ponded Block movement

shale succession of the Appalachian Basinincluding the Marcellus FormationThe AAPG Editor thanks the following reviewersfor their work on this paper Charles M Boyer IIAshton F Embry Karen S Glaser UrsulaHammes and Berry H Tew JrCopyright copy2011 The American Association of Petroleum Geologists All rights reserved

Manuscript received September 4 2009 provisional acceptance December 7 2009 revised manuscriptreceived March 22 2010 final acceptance June 30 2010DOI10130606301009150

AAPG Bulletin v 95 no 1 (January 2011) pp 61ndash 103 61

appears to have initiated in late Early Devoniantime resulting first in thinning and local erosion ofthe Oriskany sandstone in northwest PennsylvaniaThis study in addition to providing the basis for apredictive sequence-stratigraphic model that canbe used to furtherMarcellus exploration tells of aforeland basin more tectonically complex than ac-counted for by simple flexural models

INTRODUCTION

The much studied Hamilton Group of the Appala-chian Basin is an eastward and southeastward thick-ening wedge of marine and nonmarine shale silt-stone and sandstone (Cooper 1933 1934Rickard1989) To the west of the Hudson Valley the Ham-ilton succession is defined by an increasing abun-dance of fossiliferous black and gray marine shaleinterbedded with several thin laterally extensivelimestones (Cooper 1930 1933 de Witt et al1993) Hamilton Group deposits part of the Cats-kill delta succession accumulated in an elongateforeland basin that formed in response to the Aca-dian oblique collision of theAvaloniamicroplate andLaurentia (Figure 1 Ettensohn 1985 1987 Faill1985 Ferrill and Thomas 1988 Rast and Skehan1993) Throughout much of the basin the MiddleDevonian Marcellus Formation (Hall 1839) thebasal unit of the Hamilton Group comprises twoblack shale intervals separated by a sequence oflimestone shale and lesser sandstone of variablethickness (Clarke 1903 Cate 1963 deWitt et al1993) Recent advances in well stimulation of andproduction from DevonianndashMississippian blackshale gas deposits of the eastern and southernUnited States including the Barnett Fayettevilleand Woodford shales have yielded similarly prom-ising results in the Marcellus Formation (Engelderet al 2009) Continued successful exploration andexploitation of the Marcellus necessitates an en-hanced understanding of its stratigraphy includingthickness trends and compositional attributes ofthe component units throughout the core regionof Marcellus production beneath the AppalachianPlateau

62 Stratigraphy of the Middle Devonian Marcellus Formation A

Results reported on in this article are based onour analysis of more than 900 wireline logs fromtheAppalachian Basin of Pennsylvania NewYorknorthernWestVirginia easternOhio andwesternMaryland (Figure 2)We focus on the AppalachianPlateau region of the basin for three reasons itsgreater density of available wireline logs fewerstructural complications and greater economic via-bility Specific points addressed in this study include(1) the distribution and thickness trends of the twoblack shale members of the Marcellus Formation(2) the distribution and thickness of the interveninglimestone an interval that could be critical to stim-ulation and production considerations and (3) thestratigraphy and distribution of the organic-richLevanna Shale Member of the Skaneateles Forma-tion a unit that has been confused with the Mar-cellus Formation

As important as the previous points are how-ever the more significant contribution of this ar-ticle is a sequence-stratigraphic framework of theMarcellus Formation as deduced from publiclyavailable wireline logs Partington et al (1993) andEmery and Myers (1996) among others havedemonstrated the use of some of the more com-mon wireline log suites to the interpretation ofsedimentary successions in terms of such sequence-stratigraphic elements as sequence boundaries sys-tems tracts condensed sections and maximumflooding surfaces Such an approach serves as ameans by which basin fill can be organized intounconformity (or equivalent conformable surface)bounded packages of strata that provide a frame-work for predictive reservoir assessment and cor-relation into regions of minimal or poor data con-trol Thickness trends of lithostratigraphic units andthe sequence stratigraphy of the Marcellus Forma-tion reveal a basin that was more tectonically activethan heretofore realized Reactivated extensionalbasement structures including Eocambrian faultsassociated with the Rome trough and northwest-striking wrench faults (ie cross-strike structuraldiscontinuities of Wheeler 1980) appear to havecontrolled sedimentation patterns of at least theupper Lower through lower Middle Devonian suc-cession including the Marcellus Formation in west-ern New York and northwest Pennsylvania

ppalachian Basin

Figure 1 (A) General tectonic reconstruction of the Appalachian orogenic belt during the Acadian orogeny showing approximatelocations of synorogenic deposits Modified from Ettensohn (1992) and Ferrill and Thomas (1988) (B) Diagram illustrating the inferredrelationship among thrust loading foreland basin subsidence black shale sedimentation and forebulge development Modified fromEttensohn 1994

Lash and Engelder 63

Figure 2 Base map of the core region of the Marcellus Formation basin in New York Pennsylvania eastern Ohio western Marylandand northern West Virginia Symbols indicate the locations of wireline logs that were used in this study numbered and lettered wells andcross-sections refer to text figure numbers WC = Wayne County Pennsylvania SUC = Susquehanna County Pennsylvania WYC =Wyoming County Pennsylvania WAC = Washington County Pennsylvania GC = Greene County Pennsylvania SC = Sullivan CountyNew York CC = Cayuga County New York BC = Broome County New York

Figure 3 Comparison of the Marcellus Formation stratigraphy used in this study with the recently revised Marcellus stratigraphicnomenclature of Ver Straeten and Brett (2006)

64 Stratigraphy of the Middle Devonian Marcellus Formation Appalachian Basin

Figure 4 Wireline log of the Rodolfy well in Wayne County Pennsylvania illustrating (1) the Marcellus stratigraphy of Ver Straeten andBrett (2006) (2) the lithostratigraphy used in this study and (3) the sequence stratigraphic interpretation of the log (refer to text fordiscussion) See Figure 2 for location of the Rodolfy well RST = regressive systems tract MFS = maximum flooding surface TST =transgressive systems tract MRS = maximum regressive surface


STRATIGRAPHIC FRAMEWORK

James Hall (1839) was the first to apply the nameldquoMarcellus shalerdquo to organic-rich black and gray


shale exposed near the village of Marcellus Onon-daga County New York Henry Darwin Rogers acontemporary of Hall referred to Marcellus equiv-alents exposed in Pennsylvania as the ldquoCadentLower

Figure 5 Isochore map of the Union Springs Member The dashed isochore represents the mapped zero line of the Union SpringsMember elsewhere contouring is limited by a lack of data Isochore lines were not traced into the valley and ridge because of sparsedata and structural complexities

Figure 6 Wireline log sig-nature of a very thin UnionSprings Member as exhibited inthe StowellndashKolb well Chautau-qua County New York M =Levanna Member of the Skan-eateles Formation S = StaffordMember of the SkaneatelesFormation

ppalachian Basin

Black and Ash-Colored Slaterdquo in his report of theFirst Pennsylvania Geological Survey started in1836 (Millbrooke 1981) Eighty years lapsed be-fore Cooper (1930) subdivided the Marcellus For-mation into the Union Springs Member and over-lyingOatkaCreekMember This nomenclature orsome modification of it largely stemming from out-crop investigations in NewYork has been adoptedby most workers who have studied the lower Ham-ilton Group in the subsurface of New York Penn-sylvania and Ohio (eg Oliver et al 1969 VanTyne 1983 Rickard 1984 1989)

In a series of articles spanning nearly 15 yearsVer Straeten et al (1994) Ver Straeten and Brett(1995 2006) andVer Straeten (2007) proposed aMarcellus stratigraphy that seeks to reduce the ac-cumulated sometimes confusing stratigraphic ver-biage of more than 150 yr of study The revisedstratigraphy links the generally fine-grained Mar-cellus succession of the more distal western regionof the basin with that of the proximal eastern basin

where the Marcellus Formation is part of a gen-erally shallowing-upward trend from basinal blackshale to nearshore sandstone and fluvial depositsSpecificallyVer Straeten andBrett (2006) raised theMarcellus Formation to the subgroup level and theUnion Springs and overlyingOatkaCreekmembersto the formation level (Figure 3) Such a modifica-tion is consistent with the nomenclature of theoverlying units of the Hamilton Group includingthe Skaneateles Formation Ludlowville Formationand Moscow Formation in ascending order

The newly defined Union Springs Formationis principally composed of black shale of the Ba-kovenMember (Ver Straeten andBrett 2006) Theorganic-richBakovenMember of easternNewYorkis overlain by the Stony Hollow Member of theUnion Springs Formation (Figure 3) a succession ofcalcareous shale siltstone and fine-grained sand-stone In westernNewYork fossiliferous limestoneand dark shale of the Hurley Member of the OatkaCreek Formation overlies the Bakoven Member

Figure 7 Cross-section illustrating lateral variations in the thickness of the Union Springs Member and overlying Cherry Valley MemberOL = Onondaga Limestone US = Union Springs Member CV = Cherry Valley Member OC = Oatka Creek Member Depth = drillingdepth


(Figure 3) (Ver Straeten and Brett 2006) To theeast the Hurley Member of the Oatka Creekndashequivalent Mount Marion Formation overlies theStony Hollow Member (Figure 3) The HurleyMember is overlain by bedded and nodular fine-grained limestone of the Cherry Valley Member(Ver Straeten et al 1994 Ver Straeten and Brett1995 2006) The latter thickens to the east andsouth to as much as 32 ft (10 m) south of AlbanyNew York where it is composed of interbeddedshale and bioturbated sandstone (Ver Straeten andBrett 1995) The Purcell Member of Pennsylvaniais equivalent to the Cherry Valley Member (Brett


and Ver Straeten 1995) (Figure 3) The CherryValley is sharply overlain by black and gray shale ofthe Berne Member of the Oatka Creek and MountMarion formations (Figure 3) The Berne Memberof the more proximal eastern region of the basinpasses upward into organic-lean strata of the OtsegoSolsville and Pecksport members in ascending order(Ver Straeten and Brett 1995) The top of the Mar-cellus subgroup is defined by the base of the calcar-eous Stafford Member of the Skaneateles Formationin western New York and northwestern Pennsylva-nia and the laterally equivalent Mottville Memberof central New York (Ver Straeten and Brett 1995)

Figure 8Wireline logs illustrating the gamma-ray signatures of the Union Springs and overlying Oatka Creek members of the MarcellusFormation (A) Gradational contact of the Cherry Valley and overlying Oatka Creek Member (B) Union SpringsndashOatka Creek contact(Cherry Valley Member is absent)

ppalachian Basin

The revisedMarcellus stratigraphy is awelcomecontribution to our understanding of AppalachianBasin stratigraphy However such a detailed levelof subdivision especially its differentiation of grosslysimilar units such as the Hurley and Cherry Valleymembers is not readily applicable to basinwidestratigraphic interpretation of publicly availablewireline logs of varying quality Indeed only one logavailable to us permits a tentative identification oftheMarcellus stratigraphy espoused byVer Straetenand Brett (2006) The Marcellus Formation dis-played by the Columbia 1 Rodolfy well of WayneCounty Pennsylvania includes upper and lowerblack shale intervals separated bymore than 110 ft(34m) of calcareous and arenaceous rock (Figure 4)Gamma-ray and neutron porosity signatures per-mit the subdivision of the middle horizon intoupper and lower intervals (Figure 4) The latter iscomposed of approximately 65 ft (20 m) of whatappears to be sandy limestone the likely equiv-alent of Ver Straeten and Brettrsquos (2006) StonyHollowMember of their Union Springs Formation(Figures 3 4) These deposits are overlain by ap-proximately 45 ft (14m) of poorly radioactive low-porosity strata that include the Hurley and over-lying Cherry Valley members of Ver Straeten andBrettrsquos (2006)MountMarion Formation (Figures 3

4) Unfortunately the paucity of wireline logs fromthis area of the basin precludes the more wide-spread application of this stratigraphy

In this article we adopt a lithostratigraphymorein line with that used by Rickard (1984 1989) andone that lends itself to subsurface correlation ofwireline log signatures Specifically we define ourbasal unit of theMarcellus Formation as the UnionSprings Member a term recognized by the USGeological SurveyGeologicNamesLexicon (USGS2008) The Union Springs Member of this studywhich encompasses the Bakoven Member of VerStraeten and Brett (2006) is overlain by the CherryValley Member (Figure 3) Our Cherry ValleyMember which is composed of variable amountsof interlayered carbonate shale and sandstonecorrelates with the Stony Hollow Member of theUnion Springs Formation and the Hurley andCherry Valley members of the Oatka Creek andMount Marion formations of Ver Straeten andBrett (2006) (Figure 3) Finally we use the nameOatka Creek Member also recognized by the Geo-logic Names Lexicon for the succession of blackand gray shale and lesser siltstone and limestonethat underlies the Stafford and Mottville membersof the Skaneateles Formation (Figure 3)

MARCELLUS FORMATION SUBSURFACELITHOSTRATIGRAPHYAND THICKNESS TRENDS

The subsurface stratigraphy of the Marcellus For-mation has been addressed by a number ofworkersHarper andPiotrowski (1978 1979) andPiotrowskiand Harper (1979) published isopach maps of De-vonian units in Pennsylvania including the Mar-cellus Formation Their maps present the net thick-ness of the radioactive facies of theHamiltonGroupprincipally theMarcellus Formation Rickard (19841989) mapped the Marcellus in the subsurface ofNewYork northeasternOhio and the northern twothirds of Pennsylvania He presented isopach mapsfor what he termed the lower Marcellus Formation(Union Springs MemberndashCherry Valley Memberinterval) the upper Marcellus Formation (OatkaCreekMember and equivalent units) and the total

Figure 9 Interbedded black shale and limestone defining thegradational contact of the Onondaga Formation and overlyingUnion Springs Member of the Marcellus Formation exposedalong the Norfolk Southern mainline Hamilton-Newton Penn-sylvania Hammer = 30 cm (118 in) long


Marcellus Formation Last a series of stratigraphiccross-sections and isopach maps of the Devonianclastic succession of the Appalachian Basin includ-ing the Marcellus Formation were published aspart of the Eastern Gas Shales Project of the late1970s and early 1980s (eg de Witt et al 1975West 1978 Roen et al 1978 Kamakaris and VanTyne 1980)


Union Springs Member

TheUnion SpringsMember of this report thickensto the east and southeast from western New Yorkit is especially thick in northeastern Pennsylvaniawhere it exceeds 160 ft (49 m) (Figure 5) Particu-larly intriguing though is the local absence of theUnion Springs along a northeast-southwestndashtrending

Figure 10 Variations in the Onondaga LimestonendashMarcellus Formation contact across the Appalachian Basin (AndashC) gradationalOnondagandashUnion Springs contact (D) sharp Onondaga-Union Springs contact (EndashG) = sharp Onondaga-Oatka Creek contact Note thatthe wireline log D is a gamma-ray log only

ppalachian Basin

Figure 10 Continued

axis in western New York into northwestern Penn-sylvania (Figure 5) Examination of close-spacedwireline logs from this area of this basin reveals theoccasional presence of the Union Springs Memberas a thin radioactive low-density interval imme-diately above the Onondaga Formation and belowthe Cherry Valley Member (eg Rickard 1984)(Figures 6 7) Although the Tioga Ash Bed is rec-ognized by sharp increases in gamma-ray responsebulk density signatures of these deposits whichremain close to the gray shale level enable one todifferentiate ash layers from thin organic-rich in-tervals of the Union Springs Member

The basal 20 to 30 ft (6ndash9 m) of the UnionSprings Member is especially radioactive (locallygt600 American Petroleum Institute [API] units)and low density (lt235 gmL) Proprietary data dis-cussed below reveal this interval to be characterizedby reduced clay andmarkedly higher quartz pyrite

and total organic carbon (TOC) content Thincarbonate (concretionary) intervals and pyrite-richlayers can be recognized on gamma-ray bulk den-sity and photoelectric index wireline logs The up-per three quarters or so of the Union Springs isdefined by a generally diminished gamma-ray re-sponse (Figure 8) and increased bulk density

The contact of the Onondaga Formation andoverlying Union Springs Member has been inter-preted to be a regional unconformity (Potter et al1982 Rickard 1984 1989)HoweverVer Straeten(2007) maintains that with the exception of centralNew York through eastern Pennsylvania the con-tact is relatively conformable across much of Penn-sylvania western New York Ohio Maryland andWestVirginia (Figure 9) The absence of the UnionSprings Member from western New York and north-western Pennsylvania complicates this questionClearly in those regions of the basin lacking the


Union Springs Member (Figure 4) theOnondagandashMarcellus contact is unconformable TheOnondagandashUnion Springs contact appears to cut progressivelydeeper into the Onondaga Limestone from centralNewYork eastward to theHudsonValley (Rickard1989) Oliver (1954 1956) however describedthe exposed contact in Cayuga County NewYorkas an approximately 7-ft (21 m)-thick interval ofinterbedded shale and limestone suggestive of amore gradational contact Moreover gamma-rayand bulk density logs reveal a seemingly gradationalcontact extending across central and eastern NewYork and south through Pennsylvania into north-ern West Virginia (Figure 10A B C) Howeverthe OnondagandashUnion Springs contact of the WestVirginia northern panhandle and eastern Ohio isvery sharp although not necessarily unconform-able (Figure 10D)


Cherry Valley Member

The Union Springs Member of western New Yorkis overlain by the Cherry Valley Member the cor-relative of the Purcell Limestone of Pennsylvaniaand West Virginia an interval of bedded and nod-ular limestone shale and siltstone (Cate 1963Dennison andHasson 1976) As noted previouslythe Cherry Valley Member of this report includesthe interval encompassing the Stony Hollow Mem-ber of the Union Springs Formation of Ver Straetenand Brett (2006) and the Hurley and Cherry Valleymembers of Ver Straeten and Brettrsquos (2006)MountMarion Formation (Oatka Creek Formation equiv-alent) of the more proximal eastern region of thebasin (Figure 2)

TheCherryValleyMember increases from lessthan 10 ft (3 m) thick in western New York and

Figure 11 Isochore map of the Cherry Valley Member The dashed isochore represents the mapped zero line of the Cherry ValleyMember elsewhere contouring is limited by a lack of data Isochore lines were not traced into the valley and ridge because of sparsedata and structural complexities

ppalachian Basin

northwestern Pennsylvania to more than 140 ft(43 m) thick in Wayne County northeastern Penn-sylvania and Sullivan County southeastern NewYork aswell asnortheasternWestVirginia (Figure 11)The rate of change of thickness is especially rapidin southeastern New York a likely reflection of thepresence of Ver Straeten and Brettrsquos (2006) StonyHollow Member (Figures 4 11) Indeed gamma-ray and bulk density log signatures indicate thatthe Cherry Valley interval becomes more arena-ceous to the east (see Figure 4) an observationconsistent with field relationships documented fromsoutheastern NewYork (Ver Straeten et al 1994)Moreover an ongoing coring program to samplethe Marcellus Formation in the Pennsylvania Val-ley and Ridge confirms the presence of an arena-ceous Purcell Limestone in this region of the basin

Although present throughout much of the ba-sin the Cherry Valley Member displays rather ir-regular thickness trends (Figure 11) similar to whatcan be observed at the outcrop scale (eg VerStraeten et al 1994) Note that the Cherry Valleyis absent along a northeast-southwestndashtrending re-gion of western New York and northwestern Penn-sylvania coincident with that area of the basin fromwhich the Union Springs Member is thin or absent(compare Figures 5 11) Locally the Cherry Val-leyMember overlies the Onondaga Limestone theintervening Union Springs Member absent becauseof erosion or nondeposition (Figure 7) In this casethe Cherry Valley is recognized as a plateau on thegamma-ray signature immediately beneath the ra-dioactive basal interval of the overlyingOatka CreekMember (Figure 7)

Figure 12 Isochore map of the Oatka Creek Member The dashed isochore represents the mapped zero line of the Oatka CreekMember elsewhere contouring is limited by a lack of data Isochore lines were not traced into the valley and ridge because of sparsedata and structural complexities


Figu

re13

Cross-sectionillu

stratingeastw

ardthickeningof

theOatka

CreekMem

berTheOatka

Creekissubdividedinto

anorganic-rich(radioactive)

basalintervaloverlainby

organic-lean

shale(lowradioactivity)Thecross-sectionishung

onthetopof

theOatka

CreekMem

ber


Oatka Creek Member

TheCherryValleyMember is overlain by theOatkaCreek Member recognized by a radioactive basalinterval that passes upward into a higher densityless radioactive (lower TOC) shale succession con-taining occasional carbonate layers (Figure 8A) Theorganic-rich basal interval of the Oatka Creek isgenerally less radioactive than the basal interval ofthe Union Springs Member (Figure 8A B) Thecontact of the Oatka Creek and underlying CherryValley is readily defined in wireline logs locallythe contact appears to be gradational (Figure 8A)However in the absence of the Cherry Valley (orperhaps a limestone interval thinner than tool reso-lution) the contact is placed a short distance belowthe gamma-ray peak in the radioactive basal inter-val of the Oatka Creek Member (Figure 8B) TheOatka Creek rests disconformably on theOnondagaLimestone in those areas of the basin absent in theUnion Springs andCherryValleymembers Indeedin almost every example studied well-log signaturesindicate a very sharp contact (Figure 10E F G)quite unlike the seemingly gradational OnondagaLimestonendashUnion SpringsMember contact describedfrom much of the basin

The Oatka Creek Member present through-out the core region of the basin thickens to the eastmost rapidly along a north-south line east of themeridian that defines the western edge of BroomeCounty New York and the western boundaries ofSusquehanna andWyoming counties Pennsylvania(Figure 12) It exceeds 550 ft (168 m) thick ineasternWayne County Pennsylvania into SullivanCounty New York (Figure 12) However thick-ening of the Oatka Creek Member is manifestedprincipally by a marked increase in the thickness ofthe organic-lean upper part of the unit (Figure 13)That is the basal radioactive interval displays aneastward increase in thickness but at a rate far lessthan that of the overlying higher density (organic-lean) shale

The Oatka Creek Member thins to less than30 ft (9 m) along a northeast-southwestndashorientedaxis in western New York extending into Pennsyl-vania (Figure 12) This area is displaced to the eastof the similarly oriented region of the basin over

ppalachian Basin

which the Union Springs and Cherry Valley mem-bers are absent (compare Figures 5 and 11 with 12)Thinning of the Oatka Creek Member is confinedto the organic-lean shale interval that is there isno concomitant thinning of the radioactive low-density basal interval of the Oatka Creek acrossthis structure (Figure 14) Indeed the organic-richfacies of the Oatka Creek Member thickens acrossthe region over which the unit thins (Figure 15)

Stafford and Levanna MembersSkaneateles Formation

The upper contact of the Oatka Creek Memberis defined by the base of the Stafford (Mottville)Member an easily recognized marker in the sub-surface at the base of the Skaneateles Formation(Oliver et al 1969deWitt et al 1993) (Figure 16A)The bulk of the Stafford is present in a northeast-southwestndashoriented region of western New Yorkand northwestern Pennsylvania however outliersof the Stafford are present in southwestern Penn-sylvania and western Maryland (Figure 17) Thelimestone appears to pass laterally into shale

The Stafford Member is overlain by the Le-vanna Member of the Skaneateles Formation arelatively geographically restricted little-described

carbonaceous shale (Figure 18) The subsurfaceLevanna Member unlike the Union Springs andOatka Creekmembers of theMarcellus Formationis recognized by increasing gamma-ray responseupsection (Figure 19A) We arbitrarily place thetop of the Levanna at the stratigraphically highestgamma-ray peak equal to or greater than 20 APIunits in excess of a gray shale baseline establishedin the overlying nonsource succession of the Skan-eateles Formation (Figure 19A) an approach similarto that adopted for use by the Eastern Gas ShalesProject (deWitt et al 1993) Themost organic-richfacies of the Levanna Member passes laterally intoundifferentiated organic-lean shale of the SkaneatelesFormation (Figure 19B) Thus although Levannaoutcrops can be observed outside our isochore re-gion it is likely that these deposits represent theorganic-lean lateral equivalent of the Levanna Mem-ber mapped in the subsurface The bulk of theLevanna occupies a generally rectangular regionof the basin extending from western New York tosouthwestern Pennsylvania thinning rapidly to theeast and southeast and more gradually to the westand southwest (Figure 18)

Although not part of theMarcellus Formationthe Levanna Member supplements the Middle De-vonian source rock inventory where it is present

Figure 14 Contact of the OatkaCreek Member Marcellus For-mation and the overlying StaffordMember of the Skaneateles For-mation exposed on Oatka Creekvillage of LeRoy New York TOC ofthe Oatka Creek Member im-mediately beneath the contactis 4 Note heavily jointed na-ture of the organic-rich shale


Figure 15 Interpretive fill cross-section of gamma-ray values Note onlapping of organic-lean deposits on both sides of the central region of thinning

76Stratigraphy

oftheMiddle

DevonianMarcellus

FormationAppalachian

Basin

Indeed in those regions of the basin lacking theStaffordMember the Levanna can bemistaken fortheMarcellus Formation (deWitt et al 1993) Theorganic-rich facies of the LevannaMember appearsto pass rapidly eastward into organic-lean low-radioactivity shale (Rickard 1989) the Levannathins westward into Ohio where it aids in the rec-ognition of the top of the Oatka Creek In the ab-sence of the Stafford Member the Oatka CreekMemberndashSkaneateles Formation contact is placedat a densitymaximumandor gamma-rayminimum(Figure 16B) or a subtle reduction (sim10ndash15 APIunits) in gamma-ray signature (Figure 16C) thatcan be traced laterally into the Stafford Member

SEQUENCE-STRATIGRAPHIC FRAMEWORKOF THE MARCELLUS FORMATION

Mapping of lithostratigraphic units in the subsur-face is necessary to basin analysis and explorationconsiderations However it is the application ofthe sequence-stratigraphic approach that enablesone to subdivide basin fill into a framework ofsystems tracts and bounding and internal surfacesbased on depositional models and asymmetric (ac-tualistic) base level curves The resulting frameworkof reservoir properties including compositional at-tributes can be used to reduce risk in frontier re-gions of the basin or areas of poor data control Theuse of wireline logs to sequence-stratigraphic anal-ysis has been demonstrated by a number of authorsincluding Van Wagoner et al (1990) Embry andJohannessen (1992)Embry (19932002) Partingtonet al (1993) Emery andMyers (1996) Brown et al(2005) and Singh et al (2008) Moreover combi-nations of wireline logs can be used to interpret rockproperties including organic richness in terms of asequence-stratigraphic framework (eg Passey et al1990 Creaney and Passey 1993)

T-R Sequences Background

Sequence stratigraphy seeks to define and corre-late changes in depositional dynamics that reflect asingle base level cycle This article adopts the T-Rsequence described by Johnson et al (1985) and

Embry and Johannessen (1992) and further refinedbyEmbry (1993 1995 2002) Indeed Johnson et al(1985) first applied the T-R sequence concept totheDevonian succession of theAppalachian Basin aquarter of a century ago A single T-R sequencecomprises a transgressive systems tract a deepening-up succession that records rising base level overlainby regressive systems tract deposits that accumu-lated during falling base level and consequent re-duced accommodation space (Embry and Johan-nessen 1992 Embry 1993 2002) Delimiting T-Rsequences requires the identification of minimallydiachronous sequence-boundary surfaces (Embry2002 Mancini and Puckett 2002) Embry (2002)demonstrated that those surfaces most conducive todefining T-R sequences include the subaerial un-conformity the unconformable shoreline ravine-ment and the maximum regressive surface

The previously mentioned surfaces are bestthought of in terms of a single asymmetric base-levelcycle initiated by a rapid rise in base level (Embryet al 2007) Early in this base-level cycle the sedi-ment flux to the shoreline may be high enough sothat the shoreline continues to advance toward thebasin Soon however the rate of base level rise atthe shoreline exceeds the rate of sediment supplyresulting in a landward or transgressivemovementof the shoreline The maximum regressive surfacemarks this change in depositional regime from re-gression to transgression (Embry 2002 Embryet al 2007) Consideration of asymmetric base levelcurves defined by a rapid initial rise in base levelsuggests a coincidence of the maximum regressivesurface and the onset of the rise in base level (Embryet al 2007)

Rapid trangresssion is accompanied by wave-induced erosion much of the sediment being trans-ported seaward The resulting scoured surface ashoreline ravinement may ormay not have incisedthrough an underlying subaerial unconformity pro-duced during the preceding regression In the for-mer case the shoreline ravinement is termed anunconformable shoreline ravinement and is overlainby a deepening-upward marine succession thetransgressive systems tract which reflects a reducedsupply of sediment to the marine environment asthe shoreline migrates landward The presence of


deepening-upward marine deposits immediatelyabove both the unconformable shoreline ravine-ment and the maximum regressive surface suggeststhat these surfaces are minimally diachronous lat-eral equivalents the former along the flanks of thebasin and the latter in the more basinal conform-able succession (Embry 2002 Embry et al 2007)


As the rate of base level rise slows to such apoint that the sediment flux at the shoreline ex-ceeds the rate of sediment removal bywave actionravinement development stops and the shorelinebegins a regressive seaward migration Increasedsediment supply results in progradation of coarsersediments across the shelf thereby replacing the

Figure 16 Wireline logs illus-trating the nature of the topof the Oatka Creek MemberndashSkaneateles Formation contactin the presence (A) and absence(B) of the Stafford MemberPanel (C) illustrates the approachtaken in this study to define thecontact in more proximal regionsof the basin

ppalachian Basin

Figure 16 Continued

deepening-upward trend with a shallowing-upwardsuccession that comprises the regressive systemstract The surface defining the change from deep-ening-upward strata the transgressive systems tractto shallowing-upward deposits of the regressive sys-tems tract is themaximum flooding surface (Embry2002 Embry et al 2007) The maximum flood-ing surface does not necessarily record the baselevel maximum Indeed regression can be initiatedduring a base level rise if the rate of rise is less thanthe rate of sediment supply as might be expected oftectonically driven base level change (Embry et al2007)

Increased accommodation space and the re-duced clastic sediment flux that attends transgres-sion during rising base level culminates in the maxi-mum flooding surfacewhichmay correspondwith

or pass distally into a condensed section (EmeryandMyers 1996 Jervey 1988VanWagoner et al1988 1990 Partington et al 1993) Condensedsections are aerially extensive and can be composedof abundant organic matter (high TOC) and au-thigenicdiagenetic minerals (Loutit et al 1988Posamentier et al 1988 Sarg 1988 Liro et al1994 Emery and Myers 1996) Abundant plank-tonic fossils common to condensed sections (Loutitet al 1988 Posamentier et al 1988) reflect themarkedly reduced supply of clastic detritus tomorebasinal environments (Partington et al 1993)

Some have argued that transgressive systemstract deposits especially the condensed section havethe greatest source rock potential (eg Vail 1987Emery and Myers 1996) Indeed the reducedclastic flux that attends a base level high favors the


concentration of oil-prone marine organic matter(Creaney and Passey 1993) Moreover the land-ward shift of environments accompanying a risein base level induces the shoreward translation oforganic-rich facies resulting in accumulation of thecondensed section close to or at the top of thetransgressive systems tract The described faciesshift is manifested by a general increase in TOCupward from the base of the transgressive systemstract (Creaney and Passey 1993) Still organic-richsource rocks may continue to accumulate as partof the regressive systems tract as relative base levelbegins to drop Further reduction of base level andaccommodation space however is normally ac-companied by an increase in clastic sediment fluxand consequent dilution of TOC (Creaney andPassey 1993)


The general relationship of condensed sectiondeposits and source rock potential although con-firmedby a number of studies (eg Lambert 1993)is somewhat more complex than described (egMancini et al 1993) Palsey et al (1991) dem-onstrated that the greatest source potential intervalin the Upper Cretaceous Tocito Sandstone andassociated Mancos Shale of the San Juan BasinNewMexico is not found in the condensed sectionwithin the shale but rather 82 ft (25 m) below intheTocitoSandstone Similarly Leckie et al (1990)demonstrated that the highest source rock poten-tial in a succession of shallow water Cretaceousdeposits in western Canada exists within the trans-gressive systems tract but below the condensedsection However Curiale et al (1991) observedthat the most promising source rock interval in the

Figure 17 Isochore map of the Stafford Member of the Skaneateles Formation The dashed isochore represents the mapped zero lineof the Stafford Member elsewhere contouring is limited by a lack of data Isochore lines were not traced into the valley and ridgebecause of sparse data and structural complexities

ppalachian Basin

CenomanianndashTuronian succession of NewMexicolies above the condensed interval Palsey et al(1991) suggested that in some cases sedimenta-tion rates within those environments favorable toaccumulation of condensed section deposits aretoo low to preserve abundant hydrogen-rich or-ganic matter

Discussion

Our sequence-stratigraphic analysis of the Mar-cellus Formation begins with the generation of acomposite wireline log as described by Brown et al(2005) (Figure 20) Referred to as a site-specificsequence-stratigraphic section (S5) benchmark chart(Brown et al 2005) the composite log places theMarcellus into a sequence-stratigraphic framework

that can be used for basinwide correlation Indeedour composite wireline log serves as a type sectionof the Marcellus Formation in the subsurface TheMarcellus encompasses the bulk of two T-R se-quences herein referred to as MSS1 and MSS2 inascending order (Figure 20) These sequences ap-proximate equivalents of Johnson et alrsquos (1985) T-Rcycles Id and Ie and Ver Straetenrsquos (2007) Eif-2 andEif-3 sequences span approximately 18 my ex-tending from the upper ldquocostatusrdquo conodont zonethrough the ldquohemiansatrdquo zone (Kaufmann 2006Ver Straeten 2007) The relatively short durationof MSS1 and MSS2 is consistent with their reflect-ing third-order base level cycles (Mitchum andVanWagoner 1991) that occurred within a second-order cycle encompassing much of the Middle andUpper Devonian succession (Johnson et al 1985)Embry (1995) advocated a hierarchical system of

Figure 18 Isochore map of the Levanna Member of the Skaneateles Formation The dashed isochore represents the mapped zero lineof the Levanna Member elsewhere contouring is limited by a lack of data Isochore lines were not traced into the valley and ridgebecause of sparse data and structural complexities


Figure 19 Example of theapproach used in this studyto determine the thicknessof the Levanna Member(A) gamma-ray log dis-playing the Levanna Mem-ber and (B) gamma-raylog from a well lacking theorganic-rich LevannaMember Refer to textfor discussion


T-R sequences based on sequence boundary charac-teristics rather than duration The generally basin-wide extent of Marcellus T-R sequence boundariesmanifestly transgressive deposits overlying sequenceboundaries and the presence of unconformities (un-conformable shoreline ravinement) only on basin

flanks are consistent with third-order T-R sequences(Embry 1995)

The maximum regressive surface that definesthebaseofT-R sequenceMSS1 is placed at a gamma-rayminimumandor bulk densitymaximumclose toor at the topof theOnondagaLimestone (Figure 20)

Figure 20 Sequence-stratigraphic type section of the Marcellus Formation that encompasses the upper part of the underlyingOnondaga Formation and the lower interval of the Skaneateles Formation TST = transgressive systems tract RST = regressive systemstract MFS = maximum flooding surface MRS = maximum regressive surface Refer to text for discussion


Overlying MSS1 transgressive systems tract depos-its display upward-increasing (ldquodirtyingrdquo) gamma-ray and upward-decreasing bulk density log signa-tures (Figure 20) principally reflective of decreasinggrain size and increasing TOC (eg Singh et al2008) related to increasing base level In the moredistal northwestern region of the basin howevertransgressive systems tract deposits appear to bevery thin or absent the contact of the OnondagaLimestone and overlying Union Springs Memberbeing sharp (see Figure 10D) These relations sug-gest that the rate of base level rise in this region ofthe basin far exceeded clastic sediment flux

The top of the MSS1 transgressive systemstract the maximum flooding surface is placed at agamma-ray peak a short distance above the maxi-mum regressive surface (Figure 20) The maxi-


mum flooding surface is roughly coincident with acondensed section defined by abundant pyrite andthin carbonate layers both evident in bulk densityand photoelectric index wireline logs as well as incore Mineralogic analysis of a suite of sidewall coresamples recovered from MSS1 transgressive sys-tems tract deposits reveals an abundance of quartzwell in excess of that observed in overlying regres-sive systems tract deposits (Figure 21) Note thatthe clay content of the quartz-rich interval is rela-tively low (Figure 21) likely a reflection of the rapidlandward shift of marine environments at this time(eg Liro et al 1994) Thin section and scanningelectron microscopic examinations reveal that thebulk of the quartz in the MSS1 transgressive sys-tems tract (condensed section) is microcrystallinelikely derived from the dissolution of silica tests

Figure 21 Mineralogy and total organic carbon (TOC) trends through the MSS1 depositional sequence Data based on a suite ofsidewall core samples recovered from a Marcellus Formation well the location is proprietary MRS = maximum regressive surface MFS =maximum flooding surface RST = regressive systems tract TST = transgressive systems tract

ppalachian Basin

Much of the quartz lines pore throats or forms ir-regular microcrystalline aggregates that coat de-trital clay grains Occasional angular detrital quartzand feldspar grains are probably windblown detri-tus Calcite is as much as three times as abundantin transgressive systems tract deposits as in the over-lying regressive systems tract (Figure 21) Most cal-cite occurs as single crystals or patches of microsparand microcrystalline aggregates that originated fromstyliolinid fragments Last peaks in pyrite and TOCare coincident with the inferred maximum floodingsurface (Figure 21) At this time conditions con-ducive to the preservation of organic matter per-haps fully euxinic bottom conditions related to sa-linity and density stratification of the water column(eg Ettensohn and Elam 1985Werne et al 2002)were established Alternatively the relatively rapidrate of sedimentation during the time of Marcellusdeposition perhaps enhanced by a basin shallowerthan generally presumed may have combined todiminish the rate of oxidation of organic matter inthe water column

The MSS1 maximum flooding surface definesthe top of the transgressive systems tract Immedi-ately overlying regressive systems tract deposits re-cord the slow reduction of base level andor increasedsediment flux relative to base level rise (Figure 20)Overlying strata display a gradual increase in bulkdensity and reduced gamma-ray response (Figure 20)reflecting reduced organic carbon and increasingclay content Diminished total quartz (Figure 21)probably records dilution of the biogenic con-tribution by increasing amounts of clastic detritusprincipally clay as nearshore environments weredisplaced seaward and accommodation space di-minished The reduction in base level reflected inthe MSS1 regressive systems tract culminated in ac-cumulation of carbonate deposits of the Cherry Val-ley Member across much of the basin (Figure 11)Werne et al (2002) maintain that bioclastic debrisand detrital carbonate mud that comprise theCherry Valley was derived in part from exposedcarbonate platform areas bordering the basin tothe west including the Cincinnati and Algonquin

Figure 22 Gamma-ray log(left) showing the gradationalcontact (shaded interval) of theCherry Valley Member andoverlying Oatka Creek Member


Figure 23 Map (A) showing basementstructural elements (modified fromAlexander et al 2005) and location ofsequence stratigraphic cross-sections(B-G) across the core region of the Mar-cellus Formation basin RT = Rometrough L-A = Lawrenceville-Attica cross-structural discontinuity T-MU = Tyrone-Mount Union cross-structural discontinuityP-W = Pittsburgh-Washington cross-structural discontinuity Cross-sectionsare hung on the top of the MSS2 T-Rsequence Shaded ovals on the map de-note cross-section segments (with shadedlabels) that display evidence of synde-positional faulting Logs are gamma-raylogs maximum American PetroleumInstitute (API) count = 700 Refer to textfor discussion

86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued

arches Similarly Brett and Baird (1996) have inter-preted bioclastic carbonates higher in the HamiltonGroup to be lowstand deposits The maximum re-gressive surface that defines the top of MSS1 thenis placed at a gamma-ray minimum andor bulkdensity maximum within the Cherry Valley Mem-ber (Figure 20)

Note that the Columbia 1 Rodolfy well inWayne County Pennsylvania penetrated ap-proximately 65 ft (20 m) of what appears to bearenaceous limestone at the top of the regressivesystems tract interval (see Figure 4) These depos-its included in the Cherry Valley Member of thisstudy (Figures 3 4) are interpreted to comprise aparalic succession (eg Emery and Myers 1996)that had prograded in response to reduced baselevel This arenaceous facies of the Cherry ValleyMember in the subsurface of northeastern andcentral Pennsylvania and probably northern WestVirginia as well as in exposure near Kingston NewYork (Ver Straeten and Brett 2006) approxi-mately 50 mi (80 km) east of the Columbia 1Rodolfy well reflects the effects of reduced baselevel at the end of MSS1 time

Well-log signatures suggest a normally rapidtransition from theCherryValleyMember into theoverlying Oatka Creek Member (Figure 22) Theupper part of the Cherry Valley represents trans-gressive carbonate deposits recording the initiationof the MSS2 base level rise Ver Straeten et al(1994) interpret a prominent bone bed described


from the top of the Cherry Valley Member incentral western New York as a lag deposit formedduring maximum transgression consistent withasymmetric base level curves typified by a rapidinitial rise in base level (eg Embry et al 2007)The wave-worked carbonate deposits are overlainby the increasingly organic-rich (increasing gamma-ray and deceasing bulk density) basal interval of theOatka Creek Member These deposits comprisethe bulk of the MSS2 transgressive systems tract(Figure 20)

A condensed section associatedwith theMSS2maximum flooding surface which is placed at agamma-ray maximum and bulk density minimum(Figure 20) includes carbonate and pyritiferouslayers evident on bulk density and photoelectricindex logs Werne et al (2002) and Sageman et al(2003) as part of a geochemical investigation ofOatka Creek samples recovered from two coresdrilled in western New York observed a strongcorrelation between TOCmaxima and intervals ofsediment starvation However sidewall core dataof the present study and gamma-ray and bulk den-sity log signatures (see Figure 8) suggest that MSS2transgressive systems tract (condensed section)deposits are not as organic rich as equivalent de-posits of the MSS1 T-R sequence The seeminglyless organic nature of the MSS2 transgressive sys-tems tract (condensed section) may reflect theexistence of a better established terrestrial drain-age network capable of diluting the organic flux by

ppalachian Basin

Figure 23 Continued

this time Alternatively the magnitude of the baselevel rise recorded by MSS2 transgressive systemstract deposits may not have been great enough toshift facies belts far enough landward to effectivelyisolate the basin from clastic detritus

Regressive systems tract deposits immediatelyabove the MSS2 maximum flooding surface re-cord the slowing of base level rise and increasingsediment supply and consequent seaward shift ofthe shoreline The increasing supply of clastic de-

tritus to the basin and consequent dilution of or-ganic material raining out of the water column isreflected in diminishingTOCupsection recorded bya progressive increase in bulk density and reducedgamma-ray count (Figure 20) Furthermore somegamma-ray logs display a facies change upward fromrelatively carbonaceous lower regressive systemstract deposits into an overlying organic-lean regres-sive systems tract interval (Figure 20) In placeshowever this facies distinction is better made on


Figu

re23

Continued

bulk density logs (Figure 20) the response of whichappears to provide a truer indication of organiccarbon content (eg Schmoker 1979 1980 1981)

The MSS2 base level cycle culminated withaccumulation of carbonate deposits of the StaffordMember of the Skaneateles Formation a likelylowstand carbonate (eg Brett andBaird 1996) Inthe absence of limestone the maximum regressivesurface delimiting the top of MSS2 is placed at agamma-ray minimum andor bulk density maxi-mum (see Figure 16B) Such a contact separating aldquocleaning-up trendrdquo from an overlying ldquodirtying-uptrendrdquo has been described from several modernbasins including the Upper Jurassic Ute Fieldoffshore Norway (Emery and Myers 1996)

A series of sequence-stratigraphic cross sectionsthrough the core region of the basin (Figure 23A)reveals several significant aspects of the stratigraphicarchitecture of the Marcellus Formation MSS1 isthickest in northeastern Pennsylvania and southeast-ern New York where a thick regressive systems tractinterval includes arenaceous limestone (Figure 23BC) Similarly depositional sequence MSS2 thick-ens toward the northeastern region of the basin thebulk of the thickening restricted to the regressivesystems tract (Figure 23BndashD) Moreover gamma-ray log responses suggest that MSS2 transgressivesystems tract deposits are less organic rich in this re-gion of the basin (Figure 23B C) a likely reflectionof the dilution of these deposits by a high clastic fluxderived from the Acadian highland source regionThis interpretation is buttressed by the increasingthickness of MSS2 transgressive systems tract de-posits to the northeast (Figure 23B C) Impressedupon the northeastward thickening trends of bothMSS1 and MSS2 are local variations in thicknessthat may reflect the effects of basement tectonics(eg Harper 1989) Indeed the imprint of Rometroughndashrelated extensional tectonics in southwesternPennsylvania appears to be manifested by varia-tions in the thickness of MSS1 betweenWashingtonand Fayette counties (Figure 23F) Furthermorevariations in the thickness of Marcellus FormationT-R sequences are found in the western region ofPennsylvania (Figure 23D E especially F) proxi-mal to the projected region of Rome troughndashrelatedfaulting (Figure 23A)


Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued


Variations in the thickness of MSS1 regressivesystems tract deposits are suggestive of local ero-sion Notably the base of MSS2 cuts progressivelydeeper into MSS1 westward from eastern NewYork (Figure 23B C) Moreover the absence ofMSS1 in some regions of the basin indicates thaterosion has occurred In this case the base ofMSS2 is interpreted to be an unconformable shore-line ravinement that passes laterally into a maxi-mum regressive surface in the conformable suc-cession (Figure 23BndashD G) Elsewhere the MSS2maximum flooding surface is no more than a fewmeters or so above the MSS1 maximum floodingsurface (Figure 23BndashG) again indicative of ero-sion The thinning andor local absence ofMSS1 inwestern New York and Pennsylvania may reflectthe effects of both local uplift and concomitantlowering of base level In this scenario uplift begansoon after MSS1 regressive systems tract depositsstarted to accumulate This in tandem with thedrop in base level that followed MSS1 maximumflooding resulted in the accumulation of a thinperhaps starved regressive systems tract across theuplifted region of the basin However the localabsence of Cherry Valley lowstand carbonates (egFigure 8B) indicates that T-R sequence MSS1 waseroded

Regressive systems tract deposits ofMSS2 liketheir counterparts of T-R sequence MSS1 exhibitlocal variations in thickness (Figure 23DndashF) More-over the upper boundary of MSS2 cuts well downinto the sequence inwesternNewYork (Figure 23BC G) Locally the maximum regressive surface atthe top of MSS2 lies within several meters of themaximum flooding surface (Figure 23C G) How-ever MSS2 regressive systems tract deposits thickeninto northeasternOhio before thinning to the west(Figure 23C) The marked thinning of MSS2 inwestern New York locally evident in the subsur-face of western Pennsylvania (Figure 23E) appearsto be a consequence of uplift and related sedimentstarvation across this region of the basin rather thanlocal erosion The presence of the complete MSS2T-R sequence including lowstand carbonate rocksof the Stafford Member indicates that erosion isnot responsible for the marked thinning of MSS2in this region of the basin Instead thinning is likely

ppalachian Basin

a consequence of reduced sedimentation rate per-haps related to local uplift Note that the gamma-raysignature of MSS2 regressive systems tract depositsacross the area of thinning in western New York isindicative of higher TOC relative to correlative de-posits to the east andwest (compare Figures 15 23B)

TheStafford andoverlyingLevannamembers ofthe Skaneateles Formation comprise the transgres-sive systems tract of T-R sequence SKS (Figure 20)Rising base level is manifested by an upward-increasing gamma-ray response and decreasing bulkdensity the SKSmaximum flooding surface is placedat the gamma-ray peakbulk densityminimumwithinthe organic-rich Levanna Member (Figure 20)Note that the SKS maximum flooding surface incentral western New York is only approximately20 ft (6 m) above the upper maximum regressivesurface of T-R sequence MSS2 whereas farther tothe west the SKS maximum flooding surface isapproximately 60 ft (18m) above the base of SKSSimilarly the SKS maximum flooding surface innorthwestern Pennsylvania is only approximately8 ft (25 m) above the top of MSS2 However inwestern New York the same surfaces are separatedby approximately 35 ft (11 m) (Figure 23G) Theserelationships reflect the onlapping of SKS trans-gressive systems tract deposits to thewest and north

BASIN DYNAMICS THE ROLE OFBASEMENT STRUCTURES ON MARCELLUSFORMATION SEDIMENTATION PATTERNS

TheMiddle andUpperDevonian succession of theAppalachian Basin records the cratonward advanceof the Catskill Delta complex in response to theAcadian oblique collision of the Avalonia micro-plate and Laurentia (Ettensohn 1987) Rapid east-ward thickening of MSS1 and MSS2 (Figure 23CD) toward the Acadian highlands the remnant ofwhich is found in New England is characteristic offoreland basin deposits (DeCelles and Giles 1996)Superimposed on this protracted shallowing trendis a hierarchy of black shalendashbased depositional se-quences that reflect shorter term base level oscil-lations (eg Johnson et al 1985 Brett and Baird1986 1996VanTassell 1994 Ver Straeten 2007)

Ettensohn (1985 1987 1994) proposed a tectono-stratigraphic model for the Acadian orogeny thatentails four tectophases Within this frameworkblack shale accumulated as a consequence ofthrust-loadndashinduced subsidence and rapid deep-ening of the foreland basin Still the conodont-based correlation of some black shale intervals of theAppalachian Basin with depositional sequences inEuropeMorocco and the Cordilleran region of theUnited States suggests a eustatic signature (Johnsonet al 1985 Johnson and Sandberg 1989) Bothmechanismsmdasheustasy and thrust-induced sub-sidencemdashlikely shaped the Middle and Upper De-vonian stratigraphic architecture of the core regionof Marcellus exploration in the Appalachian Basin(Werne et al 2002) However it is difficult atbest to assess the relative contributions of eachdriving factormdashtectonism and eustasymdashseparately(Burton et al 1987)

Lithospheric-flexure models predict that theonset of a foreland thrust-load event and conse-quent elastic basin subsidence is accompanied bydevelopment of a forebulge on the cratonward mar-gin of the foreland basin (Quinlan and Beaumont1984Tankard 1986a bCrampton andAllen 1995DeCelles and Giles 1996) Viscoelastic (Quinlanand Beaumont 1984 Beaumont et al 1987) andelastic flexure (Flemings and Jordan 1990 Jordan andFlemings 1991) models envisage both cratonwardand hinterlandward migration of foredeeps andbulges that reflect different loading and subsequentrelaxation histories (eg Ettensohn and Chesnut1989 Ettensohn 1992 1994 Giles and Dickinson1995) However the Appalachian foreland basinat the onset of the Acadian orogeny hosted a net-work of intermittently active basement structuresinherited from the breakup of Rodinia the Pre-cambrian supercontinent Chief among these struc-tures is the Rome trough which enters Pennsylvanianear its southwest corner (Scanlin and Engelder2003) although its location throughout much ofthe state remains elusive (Harper 1989) Further-more the core region of Marcellus exploration in-cludes several northwest-striking basement wrenchfaults (Figure 23A) (Parrish andLavin 1982 Rodgersand Anderson 1984 Harper 1989) These faultsreferred to as cross-strike structural discontinuities


Figure 24 Maps showing cross-structural dis-continuities and (A) the location of the Oriskanyno-sand area Kane gravity high and the areaof the basin absent in the Union Springs Memberof the Marcellus Formation (B) the area of thebasin absent in the Cherry Valley Member of theMarcellus Formation (C) the region of the basinover which the Oatka Creek Member of theMarcellus Formation thins (D) the distribution ofthe Stafford Member of the Skaneateles Forma-tion (E) the distribution of the Levanna Memberof the Skaneateles Formation illustrating 0 ft 5 ft(15 m) and 20 ft (61 m) isochores Cross-structural discontinuities L-A = Lawrenceville-Attica B-B = Blairsville-Broadtop H-G = Home-Gallitzin T-MU = Tyrone-Mount Union P-W =Pittsburgh-Washington (modified from Parrishand Lavin 1982)


Figure 24 Continued


Figure 24 Continued

([CSD] Wheeler 1980) likely originated as strike-slip faults related to the Late Precambrian forma-tion of the protondashAtlantic Ocean (Thomas 1977)Some authors relate the apparent segmentationof the Rome trough to slip on CSD (Lavin et al1982 Harper 1989) however it appears thatstrike-slip displacement was replaced by dip-slip dis-placement by early Paleozoic time (Wagner 1976)Although the regional architecture of the Acadianforeland basin was a consequence of load-inducedsubsidence it is difficult to imagine that inheritedbasement structures including those previously de-scribed did not in some way affect foreland basinevolution and sedimentation patterns during theAcadian orogeny Reactivation of preexisting faultsduring foreland flexure can partition the basin intoregions of fault-controlled uplift and depocenters(eg Tankard 1986a DeCelles and Giles 1996)

An early indicator of forebulge-like dynamicsinduced by Acadian convergence in the Appala-chian Basin is the thinning and local absence of thelate Early Devonian Oriskany Sandstone along anortheast-southwestndashtrending region of north cen-tral and northwestern Pennsylvania (Figure 24A)


(Fettke 1938) Williams and Bragonier (1974)commenting on the coincidence of the so-calledldquoOriskany no-sand areardquowith the Kane gravity high(Parrish and Lavin 1982) (Figure 24A) specu-lated that the local absence of the Oriskany was aconsequence of Early Devonian basement upliftEttensohn (1985) subsequently attributed the lateEmsian (late Early Devonian) unconformity at thebase of the Onondaga Limestone to basinward mi-gration of a forebulge caused by tectophase I thrustloading Similarly Ver Straeten and Brett (2000)related northeastward time transgressive pinnaclereef development described from the upper part ofthe Onondaga Limestone to retrogradational (east-ward) migration of a flexural welt at the end oftectophase I of the Acadian orogeny Howeverthe subparallel orientation of theOriskany no-sandarea which is roughly mimicked by Onondaga pin-nacle reef formation (Figure 24A) and the obliqueAcadian plate convergence direction (Ettensohn1987 Ferrill and Thomas 1988) is inconsistentwith erosion of the Oriskany as a straightforwardflexural response to thrust loading in the hinter-land (ie Turcotte and Schubert 1982) Ver Straeten

ppalachian Basin

and Brett (2000) suggested that the inferred pos-itive feature on which Onondaga pinnacle reefsformed does not comport with regional forebulgemodels

Note that the elongate Oriskany no-sand areaand Kane gravity high are roughly centered be-tween the Lawrenceville-Attica and Home-Gal-litzin CSD (Figure 24A) Furthermore Onondagapinnacle reef development appears to have termi-nated close to the trace of the Lawrenceville-AtticaCSD (Figure 24A) It is an intriguing possibility thatthickness trends of the Lower Devonian OriskanySandstone andOnondaga reef development in thisregion of the basin reflect episodes of vertical dis-placement of crustal blocks bounded by the Home-Gallitzin Tyrone-Mount Union and Lawrenceville-Attica CSD (Figure 24A) Such block displacementwhich would have overprinted smooth elastic fore-bulge dynamics partitioned the foredeep basin intosubtle ridges and depocenters (DeCelles and Giles1996) We have no data to suggest that the faultswere anything but blind (ie did not intersect theEarthrsquos surface) during the time of Marcellus depo-sitions Still enough displacement may have oc-curred such that related base level changes producedlocal sites of wave base sediment reworking (ieunconformable shoreline ravinement) adjacent todepocenters Some authors have suggested that theMarcellus Formation accumulated in deep oxygen-deficient waters (Potter et al 1981) yet a rela-tively shallow water depth perhaps only 100 to130 ft (30ndash40 m) would have reduced the verticaldisplacement necessary to bring base level to sucha position that local sediment starvation or evenerosion could have occurred within the limited timeframework over which the Marcellus accumulatedIndeed Harper (1999) has suggested that the sub-tropical Marcellus Basin could have been less than165 ft (50 m) deep if the water column had beensufficiently stratified to preclude mixing of warmoxygenated surface water with anoxic or as sug-gested byWerne et al (2002) euxinic bottomwater

The organic-rich Union Springs Member re-flects a sharp increase in base level that resultedin accumulation of a transgressive systems tract atthe onset of tectophase II of the Acadian orogeny(Ettensohn 1985 1994) In more distal regions of

the basin however farther removed from clasticsources rising base level was not accompanied bydeposition of an obvious transgressive systems tractInstead the rise in base level is manifested only bya sharp contact of the Onondaga Formation andoverlyingUnion SpringsMember (see Figure 10D)Reactivated basement structures including Rometroughndashlike extensional structures appear to haveinfluenced the thickness of MSS1 and MSS2 fromsouthwestern into central Pennsylvania (Figure 23Dndash

F) The Union Springs Member which comprisesthe bulk of MSS1 transgressive and regressive sys-tems tract deposits as well as the Cherry ValleyMember much of which encompasses the upperpart of the MSS1 regressive systems tract are ab-sent along a northeast-southwestndashoriented regionof western New York and northwest Pennsylvania(Figures 5 11 24B) that parallels the Oriskany no-sand area to the south (Figure 23A B) As with theOriskany no-sand area the western and eastern limitsof the region absent in the Union Springs andCherry Valley (MSS1) deposits are roughly coin-cident with the Home-Gallitzin and Lawrenceville-Attica CSD respectively (Figure 24A B) The thin-ning and local absence of MSS1 deposits likelyreflects the effects of local warping or flexing of thebasin induced by displacement on the Lawrenceville-Attica and Home-Gallitzin CSD soon after theMSS1 base level maximum The result was a localreduction of base level of such amagnitude to causeerosion of MSS1

Transgressive systems tract deposits of MSS2the upper reworked horizon of the Cherry ValleyMember and radioactive basal interval of the over-lying Oatka Creek Member record a rapid baselevel rise Overlying regressive systems tract strata(upperOatka CreekMember and lower interval ofthe StaffordMember of the Skaneateles Formation)thickenmarkedly toward the northeastern region ofthe basin (Figure 23B C) a likely consequence ofincreasing proximity to the thrust load and clasticsources (eg DeCelles and Giles 1996) Accom-modation space at this time would have been cre-ated by relaxation of the tectonic load (Ettensohn1994) However like MSS1 the MSS2 sequencethins along a northeast-southwestndashtrending regionof western New York and Pennsylvania (Figures 12


23B) Note also that the region of thin MSS2 de-posits notably the Oatka Creek Member parallelsthe Oriskany no-sand area and is roughly boundedon the west by the Tyrone-Mount Union CSD(Figure 24C) The northern and eastern limit of theregion of Oatka Creek thinning appears to havebeen lost to erosion (Figure 24C) The presence ofthe complete MSS2 T-R sequence in the areas ofthinning in western New York (Figure 23B C G)indicates that thinning was a consequence of re-duced sediment flux rather than erosion Moreoverthe thin MSS2 sequence especially the regressivesystems tract deposits is more organic rich thanlaterally adjacent thicker MSS2 deposits (compareFigures 15 23B) We attribute local thinning ofMSS2 to accumulation of a starved or condensedT-Rsequence across a northeast-southwestndashtrending to-pographic high In this scenario organic-rich se-diment raining out of the water column was con-centrated on the high even as base level droppedwhereas organic-lean sediment perhaps depositedfrom hyperpycnal flows ponded in adjacent bathy-metric lows

The story that emerges from the describedthickness trends is one of local basement control onMarcellus sedimentation patterns that began at theend of Early Devonian time in the northwesternPennsylvania region of the basin with erosion of theOriskany Sandstone Syndepositional movementon what were likely blind faults resulted in thecreation of local depocenters and subtle ridges thatinfluenced sedimentation and erosion patterns inthis region of the greater Acadian foreland basinthat had formed as a consequence of thrust load-ing The block delimited by the Home-Gallitzinand Lawrenceville-Attica CSD experienced epi-sodes of uplift resulting in localized erosion andorsediment starvation across a topographic high fol-lowed by subsidence the creation of accommoda-tion space and consequent sediment accumula-tion Block activation appears to have shifted to thenorthwest and then to the east during the time ofMarcellus deposition Furthermore the history ofcrustal block movement apparently linked to ob-lique plate convergence continued beyond accumu-lation of the Marcellus Formation The StaffordMember the basal unit of the Skaneateles Forma-


tion records the base level minimum at the top ofthe MSS2 T-R sequence The isochore pattern ofthe Stafford toomay reflect the influence of fault-induced warping of the basin (Figure 17) That isthe southwestern edge of the Stafford Member ze-roes close to the inferred trace of the Tyrone-MountUnion CSD to the east the Lawrenceville-AtticaCSD appears to have exerted little if any controlon accumulation of the carbonate lowstand de-posits (Figure 24D) However the Stafford isthickest in the center of the block bounded by theTyrone-Mount Union and Lawrenceville-Attica CSD(Figures 17 24D) perhaps revealing the shallowestregion of the block at this time Last the south-western extent of the Stafford may reflect the influ-ence of the BlairsvillendashBroadtop CSD (Figure 24D)Conceivably a complex displacement history onboth the Tyrone-Mount Union and Blairsville-Broadtop CSD influenced sedimentation patternsat the western edge of the Stafford depocenter

The base level rise after accumulation ofMSS2regressive systems tract deposits is reflected in theLevanna Member of the Skaneateles Formationtransgressive systems tract deposits of the SKS T-Rsequence (Figure 20) The especially intriguingaspect of the Levanna isochore pattern is its sharpeastern termination close to the inferred trace of theLawrenceville-Attica CSD (Figure 24E) Relativelyrapid thinning of the organic-rich Levanna to theeast (Figure 18) is suggestive of down-to-west dis-placement along the Lawrenceville-Attica faultcreating a black shale depocenter The western limitof the Levanna is more gradual (Figures 18 24E)The thicker region of the Levanna (20-ft [61 m]isochore) terminates close to the Tyrone-MountUnion CSD (Figure 24E) However the effects ofthis fault on basin morphology appear not to havebeen great enough to preclude accumulation ofcarbonaceous sediment well to the southwest ofthe Tyrone-Mount Union CSD The southwesternlimit of Levanna sedimentation may have beeninfluenced by down-to-east displacement on thePittsburgh-Washington CSD (Figure 24E) Pro-gressive subsidence of the crustal block definedby the Lawrenceville-Attica and Tyrone-MountUnion CSD in tandem with rising base level is in-dicated by westward and northward onlapping of

ppalachian Basin

the most organic-rich facies of the Levanna Mem-ber (Figure 23G)

The generally limited distribution of the organic-rich Levanna Member relative to the more wide-spread Union Springs and Oatka Creek membersof the Marcellus Formation appears to have been aconsequence of reactivated blind basement struc-tures and consequentwarping of the foreland basinSpecifically displacement along the Lawrenceville-Attica Tyrone-Mount Union and Pittsburgh-Washington basement wrench faults created the ac-commodation space necessary for accumulation ofcarbonaceous sediment in a relatively restricted re-gion of the greater Acadian foreland basin which atthis time was receiving otherwise organic-lean sedi-ment of the Skaneateles Formation and equivalents

CONCLUSIONS

The stratigraphy and thickness trends of the Mid-dle Devonian Marcellus Formation of the Appala-chian Basin reflect the interplay of Acadian thrustloading of the Laurentian craton and short-termbase level fluctuations These events shaped thestratigraphic architecture of the Marcellus in waysthat can impact exploration and production strat-egies of this emerging shale gas play Analysis ofmore than 900 wireline logs indicates that theMarcellus Formation encompasses two third-order T-R sequencesMSS1 andMSS2 in ascendingorder These deposits are overlain by T-R sequenceSKS which comprises at least the lower part of theSkaneateles Formation The Marcellus sequencestratigraphy offers a predictive framework for res-ervoir assessment that can be extrapolated into areasof poor data control Compositional attributes thatinfluence such critical reservoir properties as po-rosity and brittleness including quartz carbonateclay and pyrite vary predictably as a consequenceof base level oscillations The sequence-stratigraphicframework of the Marcellus Formation presentedin this study demonstrates that transgressive systemstract and early regressive systems tract deposits con-tain the greatest abundance of malleable organicmatter However these same deposits are enrichedin those components that enhance reservoir brittle-

ness including quartz calcite and pyrite Assessingthe relative importance of these compositional ele-ments to production and stimulation strategies be-comes a reservoir engineering issue

Variations in the thickness of lithostratigraphicunits of the Marcellus Formation and immediatelyoverlying deposits of the Skaneateles Formation aswell as the MSS1 and MSS2 T-R sequences acrossthe core region of the basin reflect the complexrelationship among Acadian thrust loading fluc-tuations in base level recurrent basement struc-tures and proximity to clastic sources Acadianthrust loading of Laurentia played a first-order rolein creating the accommodation space necessary foraccumulation of both Marcellus T-R sequencesIndeed accommodation space was greatest in thenortheast region of the basin proximal to the Aca-dian thrust load and clastic sources Howevermarked local variations in the thickness of bothT-R sequences especially regressive systems tractdeposits are likely a consequence of displacementalong reactivated blind basement faults includ-ing those associated with the Rome trough whichwarped the foreland basin into low relief ridges anddepocenters

The possible influence of structural control onthe thickness of the Marcellus Formation is not anew concept Piotrowski and Harper (1979) pre-sented evidence that the Laurel Hill Negro Moun-tain and Chestnut Ridge anticlines of southwestPennsylvania were active during accumulation ofthe Marcellus Formation More recently Scanlinand Engelder (2003) demonstrated that the thick-ening of Marcellus black shale in the hinges of anti-clines in southwest Pennsylvania was a consequenceof Alleghanian folding The present study extendsthe concept of basement control on sedimentationand erosion patterns over a greater expanse of thebasin The northwest-striking TyroneMount UnionLawrenceville-Attica and Home-Gallitzin wrenchfaults most likely blind appear to have been es-pecially active in the central to western New Yorkand western Pennsylvania region of the Appala-chian Basin during the time ofMarcellus depositionproducing subtle ridges and depocentersmanifestedby local erosion and increases in thickness of theMSS1 and MSS2 sequences


REFERENCES CITED

Alexander S S R Cakir A G Doden D P Gold and S IRoot compilers 2005 Basement depth and relatedgeospatial database for Pennsylvania Pennsylvania Geo-logical Survey 4th series Open-File General GeologyReport 05-010 wwwdcnrstatepaustopogeoopenfile(accessed January 29 2010)

Beaumont C G M Quinlan and J Hamilton 1987 TheAlleghanian orogeny and its relationship to the evolutionof the eastern interior North America in C Beaumontand A J Tankard eds Sedimentary basins and basin-forming mechanisms Canadian Society of PetroleumGeologists Memoir 12 p 425ndash446

Brett C E and G C Baird 1986 Symmetrical and upwardshoaling cycles in the Middle Devonian of New YorkState and their implications for the punctuated aggrada-tional cycle hypothesis Paleooceanography v 1 p 431ndash445 doi101029PA001i004p00431

Brett C E and G C Baird 1996 Middle Devonian sedi-mentary cycles and sequences in the northern Appala-chian Basin in B J Witzke G A Ludvigson and JDay eds Paleozoic sequence stratigraphy Views fromthe North American craton Geological Society of Amer-ica Special Paper 306 p 213ndash241

Brett C E and C A Ver Straeten 1995 Middle Devonian(Eifelian) carbonates northern and central AppalachianBasin Sequence stratigraphic framework AAPGBulletinv 79 p 1410ndash1411

Brown Jr L F R G Loucks and R H Trevino 2005 Site-specific sequence-stratigraphic section benchmark chartsare key to regional chronostratigraphic systems tract anal-ysis in growth-fault basins AAPG Bulletin v 89 p 715ndash724 doi10130601270504066

Burton R C Kendall and I Lerche 1987Out of our depthOn the impossibility of fathoming eustasy from the strati-graphic record Earth Science Reviews v 24 p 237ndash277 doi1010160012-8252(87)90062-6

Cate A S 1963 Lithostratigraphy of some Middle andUpper Devonian rocks in the subsurface of southwesternPennsylvania Pennsylvania Topographic and GeologicalSurveyGeneral GeologyReport Fourth Series NoG39p 229ndash440

Clarke J M 1903 Classification of New York series of geo-logic formations New York State Museum HandbookNo 19 table 2 28 p

Cooper G A 1930 Stratigraphy of the Hamilton Groupof New York American Journal of Science 5th seriesv 19 p 116ndash134 214-236

Cooper G A 1933 Stratigraphy of the Hamilton Group ofeastern New York part 1 American Journal of Sciencev 26 p 537ndash551


Crampton S L and P A Allen 1995 Recognition of fore-bulge unconformities associatedwith early stage forelandbasin development Example from the North Alpineforeland basin AAPG Bulletin v 79 p 1495ndash1514

100 Stratigraphy of the Middle Devonian Marcellus Formation

Creaney S and Q R Passey 1993 Recurring patterns oftotal organic carbon and source rock quality within a se-quence stratigraphic framework AAPG Bulletin v 77p 386ndash401

Curiale J A R D Cole and R J Witmer 1991 Applica-tion of organic geochemistry to sequence stratigraphicanalysis FourCorners areaNewMexicoUSAOrganicGeochemistry v 19 p 53ndash75 doi1010160146-6380(92)90027-U

DeCelles P G and K A Giles 1996 Foreland basins BasinResearch v 8 p 105ndash123 doi101046j1365-2117199601491x

Dennison J M and K O Hasson 1976 Stratigraphic crosssection ofHamiltonGroup (Devonian) and adjacent strataalong south border of Pennsylvania AAPGBulletin v 60p 278ndash287

de Witt Jr W W J Perry Jr and L G Wallace 1975 Oiland gas data fromDevonian and Silurian rocks in the Ap-palachian Basin US Geological Survey MiscellaneousInvestigations Series Map I-917 B

deWitt JrW J B Roen and L GWallace 1993 Stratigra-phy of Devonian black shales and associated rocks in theAppalachian Basin USGeological Survey Bulletin 1909p B1ndashB47

Embry A 1993 Trangressive-regressive (T-R) sequenceanalysis of the Jurassic succession of the Sverdrup BasinCanadian Arctic Archipelago Canadian Journal of EarthScience v 30 p 301ndash320

Embry A 1995 Sequence boundaries and sequence hierar-chies Problems and proposals in R J Steel V L Felt EP Johannesson and C Mathieu eds Sequence stratigra-phy on the northwest European margin Norwegian Pe-troleum Society Special Publication 5 p 1ndash11

Embry A 2002 Transgressive-regressive (T-R) sequencestratigraphy in J Armentrout and N Rosen eds GulfCoast SEPM Conference Proceedings Houston Texasp 151ndash172

Embry A and E Johannessen 1992 T-R sequence stratigra-phy facies analysis and reservoir distribution in the upper-most Triassic-Lower Jurassic succession western SverdrupBasin Arctic Canada in T O Vorren E Bergsager Oslash ADahl-Stamnes E Holter B Johansen E Lie and T BLund eds Arctic geology and petroleum potential Nor-wegian Petroleum Society Special Publication 2 p 121ndash146

Embry A E Johannessen D Owen B Beauchamp and PGianolla 2007 Sequence stratigraphy as a ldquoconcreterdquostratigraphic discipline Report of the ISSC Task Groupon Sequence Stratigraphy 104 p httpsepmstrataorgPDF-FilesSeqStrat-RefsISSC_Report_on_Sequence_Stratigraphypdf (accessed February 16 2010)

Emery D and K J Myers 1996 Sequence stratigraphyBlackwell Science Oxford United Kingdom 297 p

Engelder T G G Lash and R S Uzcaacutetegui 2009 Joint setsthat enhance production from Middle and Upper Devo-nian gas shales of theAppalachian Basin AAPGBulletinv 93 p 857ndash889 doi10130603230908032

Ettensohn F R 1985 The Catskill delta complex and theAcadian orogeny A model in D L Woodrow and W D

Appalachian Basin

Sevon eds The Catskill delta Geological Society ofAmerica Special Paper 201 p 39ndash49

Ettensohn F R 1987 Rates of relative plate motion duringthe Acadian orogeny based on the spatial distribution ofblack shales Journal of Geology v 95 p 572ndash582doi101086629150

Ettensohn F R 1992 Controls on the origin of theDevonianndashMississippian oil and gas shales east-central United StatesFuel v 71 p 1487ndash1492 doi1010160016-2361(92)90223-B

Ettensohn F R 1994 Tectonic controls on formation andcyclicity of major Appalachian unconformities and asso-ciated stratigraphic sequences SEPM Concepts in Sedi-mentology and Paleontology No 4 Tectonic and Eu-static Controls on Sedimentary Cycles p 217ndash242

Ettensohn F R and D R Chestnut Jr 1989 Nature andprobable origin of the MississippianndashPennsylvania un-conformity in the eastern United States InternationaleCongres de Stratigraphic et Geologie du CarbonifereBeijing 11th Compte Rendu 4 p 145ndash159

Ettensohn F R and T D Elam 1985 Defining the natureand location of a LateDevonianndashEarlyMississippian pycno-cline in eastern Kentucky Geological Society of AmericaBulletin v 96 p 1313ndash1321 doi1011300016-7606(1985)96lt1313DTNALOgt20CO2

Faill R T 1985 The Acadian orogeny and the Catskill Delta inD L Woodrow andW D Sevon eds The Catskill DeltaGeological Society of America Special Paper 201 p 15ndash38

Ferrill B A andW A Thomas 1988 Acadian dextral trans-pression and synorogenic sedimentary successions in theAppalachians Geology v 16 p 604ndash608 doi1011300091-7613(1988)016lt0604ADTASSgt23CO2

Fettke C R 1938 Oriskany as a source of gas and oil inPennsylvania and adjacent areas AAPG Bulletin v 22p 241ndash266

Flemings P B and T E Jordan 1990 A synthetic strati-graphic model of foreland basin development Journal ofGeophysical Research v 94 p 3851ndash3866 doi101029JB094iB04p03851

Giles K A and W R Dickinson 1995 The interplay ofeustasy and lithospheric flexure in forming stratigraphicsequences in foreland settings An example from theAntler foreland Nevada and Utah in S L Dorobekand G M Ross eds Stratigraphic evolution of forelandbasins SEPM Special Publication 52 p 187ndash209

Hall J 1839 Third annual report of the Fourth GeologicalDistrict of the State of New York Geological Survey ofNew York Annual Report v 3 p 287ndash339

Harper J A 1989 Effects of recurrent tectonic patterns onthe occurrence and development of oil and gas resourcesin western Pennsylvania Northeastern Geology v 11p 225ndash245

Harper J A 1999 Devonian inG H Shultz ed The geol-ogy of Pennsylvania Pennsylvania Geological SurveySpecial Publication 1 p 109ndash127

Harper J A and R G Piotrowski 1978 Stratigraphy ex-tent gas production and future gas potential of the De-vonian organic-rich shales in Pennsylvania Preprints 2dEastern Gas Shales Symposium METCSP-786 v Ip 310ndash329

Harper J A and R G Piotrowski 1979 Stratigraphic cor-relation of surface and subsurface Middle and Upper De-vonian southwestern Pennsylvania in J M DennisonK O Hasson D M Hoskins R M Jolley and W DSevon eds Devonian shales in south-central Pennsylva-nia and Maryland 44th Annual Field Conference ofPennsylvania Geologists Guidebook Bedford Pennsyl-vania p 18ndash37

Jervey M T 1988 Quantitative geological modeling ofsiliciclastic rock sequences and their seismic expressionin C K Wilgus B S Hastings C G St C Kendall HPosamentier C A Ross and J Van Wagoner eds Sea-level changes An integrated approach SEPM SpecialPublication 42 p 47ndash69

Johnson J G and C A Sandberg 1989 Devonian eustaticevents in the western United States and their biostrati-graphic responses in N J McMillan A F Embry andD J Glass eds Devonian of the world Canadian Soci-ety of Petroleum Geologists Memoir 14 v 3 p 171ndash178

Johnson J G G Klapper and C A Sandberg 1985 Devo-nian eustatic fluctuations in Euramerica Geological So-ciety of America Bulletin v 96 p 567ndash587 doi1011300016-7606(1985)96lt567DEFIEgt20CO2

Jordan T E and P B Flemings 1991 Large scale strati-graphic architecture eustatic variation and unsteady tec-tonism A theoretical evaluation Journal of GeophysicalResearch v 96 p 6681ndash6699 doi10102990JB01399

Kamakaris D G and AM Van Tyne 1980 Isopachmap ofblack shale in theHamiltonGroup (fromwell sample stud-ies) Morgantown Energy Technology Center Morgan-town Energy Tech ControlEastern Shale Gas Project(METCESGP) Series 110

Kaufmann B 2006 Calibrating the Devonian time scale Asynthesis of U-Pb ID-TIMS ages and conodont stratigra-phy Earth Science Reviews v 75 p 175ndash190 doi101016jearscirev200601001

Lambert M W 1993 Internal stratigraphy and organic fa-cies of the Devonian-Mississippian Chattanooga (Wood-ford) shale in Oklahoma and Kansas in B J Katz andL M Pratt eds Source rocks in a sequence stratigraphicframework AAPG Studies in Geology 37 p 163ndash176

Lavin P M D L Chaffin and W Davis 1982 Major linea-ments and the Lake Erie-Maryland crustal block Tec-tonics v 1 p 431ndash440 doi101029TC001i005p00431

Leckie D A C Singh F Goodarzi and J H Wall 1990Organic-rich radioactive marine shale A case study of ashallow-water condensed section Cretaceous ShaftsburyFormation Alberta Canada Journal of Sedimentary Pe-trology v 60 p 101ndash117

Liro L M W C Dawson B J Katz and V D Robison1994 Sequence stratigraphic elements and geochemicalvariability within a ldquocondensed sectionrdquo Eagle FordGroup east-central Texas Transactions of theGulf CoastAssociation of Geological Societies v 44 p 393ndash402

Loutit T S J Hardenbol P R Vail and G R Baum 1988Condensed sectionsThe key to age determination and cor-relation of continentalmargin sequences inC KWilgusB S Hastings C G St C Kendall H W PosamentierC A Ross and J C Van Wagoner eds Sea-level


changes An integrated approach SEPM Special Publica-tion 42 p 183ndash213

Mancini E A and T M Puckett 2002 Transgressive-regressive cycles in lower Cretaceous strata MississippiInterior Salt Basin area of the northeastern Gulf of Mex-ico USA Cretaceous Research v 23 p 409ndash438doi101006cres20021012

Mancini E A B W Tew and R M Mink 1993 Petroleumsource rock potential of Mesozoic condensed section de-posits of southwest Alabama in B J Katz and L MPratt eds Source rocks in a sequence stratigraphic frame-work AAPG Studies in Geology 37 p 147ndash162

Millbrooke A 1981 HenryDarwin Rogers and the first stategeological survey of Pennsylvania Northeastern Geol-ogy v 3 p 71ndash74

Mitchum R M J and J C Van Wagoner 1991 High-frequency sequences and their stacking patterns Se-quence stratigraphic evidence of high-frequency eustaticcycles Sedimentary Geology v 70 p 131ndash160 doi1010160037-0738(91)90139-5

Oliver Jr W A 1954 Stratigraphy of the Onondaga Lime-stone (Devonian) in central New York Geological Soci-ety of America Bulletin v 65 p 621ndash652 doi1011300016-7606(1954)65[621SOTOLD]20CO2

Oliver Jr W A 1956 Stratigraphy of the Onondaga Lime-stone in eastern New York Geological Society of Amer-ica v 67 p 1441ndash1474 doi1011300016-7606(1956)67[1441SOTOLI]20CO2

Oliver JrWAWdeWitt Jr JMDennisonDMHoskinsand J W Huddle 1969 Correlation of Devonian rockunits in the Appalachian Basin US Geological SurveyOil and Gas Investigation Chart OC-64

Palsey M A W A Gregory and G F Hart 1991 Organicmatter variations in transgressive and regressive shalesOrganic Geochemistry v 17 p 483ndash501 doi1010160146-6380(91)90114-Y

Parrish J B and P M Lavin 1982 Tectonic model for kim-berlite emplacement in theAppalachian Plateau of Penn-sylvania Geology v 10 p 344ndash347 doi1011300091-7613(1982)10lt344TMFKEIgt20CO2

Partington M A B C Mitchener N J Milton and A JFraser 1993 Genetic sequence stratigraphy for theNorth Sea Late Jurassic and Early Cretaceous Distribu-tion and prediction of Kimmeridgianmdashlate Ryazanian re-servoirs in theNorth Sea and adjacent areas in J R Park-er ed Petroleum geology of northwest EuropeProceedings of the 4th Conference Geological Society(London) p 347ndash370

Passey Q R S Creaney J B Kulla F J Moretti and J DStroud 1990 A practical model for organic richnessfrom porosity and resistivity logs AAPG Bulletin v 74p 1777ndash1794

Piotrowski R G and J A Harper 1979 Black shale andsandstone facies of the Devonian ldquoCatskillrdquo clastic wedgein the subsurface ofwestern PennsylvaniaUSDepartmentof Energy Eastern Gas Shales Project EGSP Series 1340 p

Posamentier HW M T Jervey and P R Vail P R 1988Eustatic controls on clastic deposition IConceptual frame-work inC KWilgus B S Hastings C G St C Kendall


H W Posamentier C A Ross and J C Van Wagonereds Sea-level changes An integrated approach SEPMSpecial Publication 42 p 110ndash124

Potter P E J B Maynard andW A Pryor 1981 Sedimen-tology of gas-bearingDevonian shales of theAppalachianBasin US Department of Energy USDOEMETC-114Morgantown West Virginia 43 p

Potter P E J B Maynard and W A Pryor 1982 Appala-chian gas bearing Devonian shales Statements and dis-cussions Oil and Gas Journal v 80 (January 25) p 290ndash318

Quinlan G M and C Beaumont 1984 Appalachian thrust-ing lithospheric flexure and the Paleozoic stratigraphy ofthe eastern interior of North America Canadian Journal ofEarth Sciences v 31 p 973ndash996 doi101139e84-103

Rast N and J W Skehan 1993 Mid-Paleozoic orogenesisin the North Atlantic The Acadian orogeny in D CRoy and S J Skehan eds The Acadian orogeny Geo-logical Society of America Special Paper 275 p 1ndash25

Rickard L V 1984 Correlation of the subsurface Lower andMiddle Devonian of the Lake Erie region Geological So-ciety of America Bulletin v 95 p 814ndash828 doi1011300016-7606(1984)95lt814COTSLAgt20CO2

Rickard L V 1989 Stratification of the subsurface low andmid-Devonian of New York Pennsylvania Ohio andOntario New York State Museum and Science Mapand Chart Series 39 59 p

RodgersM R and T H Anderson 1984 Tyrone-Mt Unioncross-strike lineament of Pennsylvania Amajor Paleozoicbasement fracture and uplift boundary AAPG Bulletinv 68 p 92ndash105

Roen J B L GWallace and J deWitt Jr 1978 Preliminarystratigraphic cross section sowing radioactive zones in theDevonian black shales in the central part of the AppalachianBasin US Geological Survey Oil and Gas InvestigationsChart OC-87

Sageman B B A EMurphy J PWerneCAVer StraetenD J Hollander and T W Lyons 2003 A tale of shalesThe relative roles of production decomposition and dilu-tion in the accumulation of organic-rich strata Middle-Upper Devonian Appalachian Basin Chemical Geologyv 195 p 229ndash273 doi101016S0009-2541(02)00397-2

Sarg J F 1988 Carbonate sequence stratigraphy in C KWilgusB SHastingsCGStCKendallH PosamentierC A Ross and J Van Wagoner eds Sea-level changesAn integrated approach SEPM Special Publication 42p 155ndash181

Scanlin M A and T Engelder 2003 The basement versusthe no-basement hypotheses for folding within the Ap-palachian Plateau detachment sheet American Journalof Science v 303 p 519ndash563 doi102475ajs3036519

Schmoker J W 1979 Determination of organic content ofAppalachian Devonian shales from formation-densitylogs AAPG Bulletin v 63 p 1504ndash1509

Schmoker J W 1980 Organic content of Devonian shalein western Appalachian Basin AAPG Bulletin v 64p 2156ndash2165

Schmoker JW 1981Determination of organic-matter con-tent of Appalachian Devonian shales from gamma-raylogs AAPG Bulletin v 65 p 1285ndash1298

Appalachian Basin

Singh P R Slatt and W Coffey 2008 Barnett Shalemdashunfolded Sedimentology sequence stratigraphy and re-gional mapping Gulf Coast Association of GeologicalSocieties Transactions v 58 p 777ndash795

Tankard A J 1986a On the depositional response tothrusting and lithospheric flexure Examples from theAppalachian and Rocky Mountain basins in P A Allenand PHomewood eds Foreland basins Special Publica-tions of the International Society of Sedimentologists v 8p 369ndash392

Tankard A J 1986b Depositional response to foreland de-formation in the Carboniferous of eastern KentuckyAAPG Bulletin v 70 p 853ndash868

ThomasWA 1977 Evolution of theAppalachian-Oauchitasalients and recesses from reentrants and promontoriesin the continental margin American Journal of Sciencev 277 p 1233ndash1278

Turcotte D L and G Schubert 1982 Geodynamics Ap-plications of continuum physics to geological problemsNew York John Wiley 450 p

USGS (US Geological Survey) National Geologic MapDatabase Geologic Names Lexicon 2008 httpngmdbusgsgovGeolexgeolex_homehtml (accessed August2010)

Vail P R 1987 Seismic stratigraphy interpretation proce-dure in AW Bally ed Atlas of seismic stratigraphyvol 1 AAPG Studies in Geology 27 p 1ndash10

Van Tassell J 1994 Evidence for orbitally-driven sedimen-tary cycles in the Devonian Catskill delta complex in JM Dennison and F R Ettensohn eds Tectonic andeustatic controls on sedimentary cycles Society for Sedi-mentary Geology Concepts in Sedimentology and Pa-leontology v 4 p 121ndash131

Van Tyne A 1983 Natural gas potential of the Devonianblack shales of New York Northeastern Geology andEnvironmental Sciences v 5 p 209ndash216

VanWagoner J CHW Posamentier RMMitchum P RVail J F Sarg T S Loutit and J Hardenbol 1988 Anoverview of the fundamentals of sequence stratigraphyand key definitions in C K Wilgus B S HastingsC G St C Kendall H Posamentier C A Ross andJ Van Wagoner eds Sea-level changes An integratedapproach SEPM Special Publication 42 p 39ndash45

Van Wagoner J C R M Mitchum K M Campion andV D Rahmanian 1990 Siliciclastic sequence stratigra-phy in well logs cores and outcrops Concepts for high-

resolution correlation of time and facies AAPGMethodsin Exploration Series 7 55 p

Ver Straeten C A 2007 Basinwide stratigraphic synthesisand sequence stratigraphy upper Pragian Emsian andEifelian stages (Lower to Middle Devonian) Appala-chian Basin in R T Becker and W T Kirchgasser edsDevonian events and correlations Geological Society(London) Special Publication 278 p 39ndash81

Ver Straeten C A and C E Brett 1995 Lower andMiddleDevonian foreland basin fill in the Catskill front Strati-graphic synthesis sequence stratigraphy and the Aca-dian Orogeny New York State Geological Association67th Annual Meeting Guidebook p 313ndash356

Ver Straeten C A and C E Brett 2000 Bulge migrationand pinnacle reef development Devonian Appalachianforeland basin Journal of Geology v 108 p 339ndash352doi101086314402

Ver Straeten C A and C E Brett 2006 Pragian to Eifelianstrata (middle Lower to lower Middle Devonian) north-ern Appalachian Basin Stratigraphic nomenclaturalchanges Northeastern Geology and EnvironmentalSciences v 28 p 80ndash95

Ver Straeten C A D H Griffing and C E Brett 1994The lower part of the Middle Devonian MarcellusldquoShalerdquo central to western New York state Stratigraphyand depositional history New York State Geological As-sociation 66th Annual Meeting Guidebook p 271ndash321

Wagner W R 1976 Growth faults in Cambrian and LowerOrdovician rocks of western Pennsylvania AAPG Bul-letin v 60 p 414ndash427

Werne J P B B Sageman TW Lyons andD J Hollander2002 An integrated assessment of a ldquotype euxinicrdquo de-posit Evidence for multiple controls on black shale de-position in themiddle DevonianOatka Creek formationAmerican Journal of Science v 302 p 110ndash143 doi102475ajs3022110

West M 1978 Preliminary stratigraphic cross section show-ing radioactive zones in the Devonian black shales in theeastern part of the Appalachian Basin US GeologicalSurvey Oil and Gas Investigations Chart OC-86

Wheeler R L 1980 Cross-strike structural discontinuitiesPossible exploration tool for natural gas in Appalachianoverthrusting belt AAPG Bulletin v 64 p 2166ndash2178

Williams E andW Bragonier 1974 Controls of early Penn-sylvanian sedimentation in western Pennsylvania Geo-logical Society of America Special Paper 148 p 135ndash152


appears to have initiated in late Early Devoniantime resulting first in thinning and local erosion ofthe Oriskany sandstone in northwest PennsylvaniaThis study in addition to providing the basis for apredictive sequence-stratigraphic model that canbe used to furtherMarcellus exploration tells of aforeland basin more tectonically complex than ac-counted for by simple flexural models

INTRODUCTION

The much studied Hamilton Group of the Appala-chian Basin is an eastward and southeastward thick-ening wedge of marine and nonmarine shale silt-stone and sandstone (Cooper 1933 1934Rickard1989) To the west of the Hudson Valley the Ham-ilton succession is defined by an increasing abun-dance of fossiliferous black and gray marine shaleinterbedded with several thin laterally extensivelimestones (Cooper 1930 1933 de Witt et al1993) Hamilton Group deposits part of the Cats-kill delta succession accumulated in an elongateforeland basin that formed in response to the Aca-dian oblique collision of theAvaloniamicroplate andLaurentia (Figure 1 Ettensohn 1985 1987 Faill1985 Ferrill and Thomas 1988 Rast and Skehan1993) Throughout much of the basin the MiddleDevonian Marcellus Formation (Hall 1839) thebasal unit of the Hamilton Group comprises twoblack shale intervals separated by a sequence oflimestone shale and lesser sandstone of variablethickness (Clarke 1903 Cate 1963 deWitt et al1993) Recent advances in well stimulation of andproduction from DevonianndashMississippian blackshale gas deposits of the eastern and southernUnited States including the Barnett Fayettevilleand Woodford shales have yielded similarly prom-ising results in the Marcellus Formation (Engelderet al 2009) Continued successful exploration andexploitation of the Marcellus necessitates an en-hanced understanding of its stratigraphy includingthickness trends and compositional attributes ofthe component units throughout the core regionof Marcellus production beneath the AppalachianPlateau


Results reported on in this article are based onour analysis of more than 900 wireline logs fromtheAppalachian Basin of Pennsylvania NewYorknorthernWestVirginia easternOhio andwesternMaryland (Figure 2)We focus on the AppalachianPlateau region of the basin for three reasons itsgreater density of available wireline logs fewerstructural complications and greater economic via-bility Specific points addressed in this study include(1) the distribution and thickness trends of the twoblack shale members of the Marcellus Formation(2) the distribution and thickness of the interveninglimestone an interval that could be critical to stim-ulation and production considerations and (3) thestratigraphy and distribution of the organic-richLevanna Shale Member of the Skaneateles Forma-tion a unit that has been confused with the Mar-cellus Formation

As important as the previous points are how-ever the more significant contribution of this ar-ticle is a sequence-stratigraphic framework of theMarcellus Formation as deduced from publiclyavailable wireline logs Partington et al (1993) andEmery and Myers (1996) among others havedemonstrated the use of some of the more com-mon wireline log suites to the interpretation ofsedimentary successions in terms of such sequence-stratigraphic elements as sequence boundaries sys-tems tracts condensed sections and maximumflooding surfaces Such an approach serves as ameans by which basin fill can be organized intounconformity (or equivalent conformable surface)bounded packages of strata that provide a frame-work for predictive reservoir assessment and cor-relation into regions of minimal or poor data con-trol Thickness trends of lithostratigraphic units andthe sequence stratigraphy of the Marcellus Forma-tion reveal a basin that was more tectonically activethan heretofore realized Reactivated extensionalbasement structures including Eocambrian faultsassociated with the Rome trough and northwest-striking wrench faults (ie cross-strike structuraldiscontinuities of Wheeler 1980) appear to havecontrolled sedimentation patterns of at least theupper Lower through lower Middle Devonian suc-cession including the Marcellus Formation in west-ern New York and northwest Pennsylvania

ppalachian Basin














ppalachian Basin











ppalachian Basin













ppalachian Basin

Figure 10 Continued












ppalachian Basin





Figu

re13

Cross-sectionillu

stratingeastw

ardthickeningof

theOatka

CreekMem

berTheOatka




organic-lean


onthetopof

theOatka

CreekMem

ber


Oatka Creek Member




ppalachian Basin










76Stratigraphy

oftheMiddle

DevonianMarcellus


Basin














ppalachian Basin

Figure 16 Continued










ppalachian Basin


Discussion

















ppalachian Basin






86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin





































ppalachian Basin











ppalachian Basin













ppalachian Basin

Figure 10 Continued












ppalachian Basin





Figu

re13

Cross-sectionillu

stratingeastw

ardthickeningof

theOatka

CreekMem

berTheOatka




organic-lean


onthetopof

theOatka

CreekMem

ber


Oatka Creek Member




ppalachian Basin










76Stratigraphy

oftheMiddle

DevonianMarcellus


Basin














ppalachian Basin

Figure 16 Continued










ppalachian Basin


Discussion

















ppalachian Basin






86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin


































ppalachian Basin













ppalachian Basin

Figure 10 Continued












ppalachian Basin





Figu

re13

Cross-sectionillu

stratingeastw

ardthickeningof

theOatka

CreekMem

berTheOatka




organic-lean


onthetopof

theOatka

CreekMem

ber


Oatka Creek Member




ppalachian Basin










76Stratigraphy

oftheMiddle

DevonianMarcellus


Basin














ppalachian Basin

Figure 16 Continued










ppalachian Basin


Discussion

















ppalachian Basin






86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin




































ppalachian Basin

Figure 10 Continued












ppalachian Basin





Figu

re13

Cross-sectionillu

stratingeastw

ardthickeningof

theOatka

CreekMem

berTheOatka




organic-lean


onthetopof

theOatka

CreekMem

ber


Oatka Creek Member




ppalachian Basin










76Stratigraphy

oftheMiddle

DevonianMarcellus


Basin














ppalachian Basin

Figure 16 Continued










ppalachian Basin


Discussion

















ppalachian Basin






86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin
























Figure 10 Continued












ppalachian Basin





Figu

re13

Cross-sectionillu

stratingeastw

ardthickeningof

theOatka

CreekMem

berTheOatka




organic-lean


onthetopof

theOatka

CreekMem

ber


Oatka Creek Member




ppalachian Basin










76Stratigraphy

oftheMiddle

DevonianMarcellus


Basin














ppalachian Basin

Figure 16 Continued










ppalachian Basin


Discussion

















ppalachian Basin






86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin






























ppalachian Basin





Figu

re13

Cross-sectionillu

stratingeastw

ardthickeningof

theOatka

CreekMem

berTheOatka




organic-lean


onthetopof

theOatka

CreekMem

ber


Oatka Creek Member




ppalachian Basin










76Stratigraphy

oftheMiddle

DevonianMarcellus


Basin














ppalachian Basin

Figure 16 Continued










ppalachian Basin


Discussion

















ppalachian Basin






86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin




























Figu

re13

Cross-sectionillu

stratingeastw

ardthickeningof

theOatka

CreekMem

berTheOatka




organic-lean


onthetopof

theOatka

CreekMem

ber


Oatka Creek Member




ppalachian Basin










76Stratigraphy

oftheMiddle

DevonianMarcellus


Basin














ppalachian Basin

Figure 16 Continued










ppalachian Basin


Discussion

















ppalachian Basin






86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin

































76Stratigraphy

oftheMiddle

DevonianMarcellus


Basin














ppalachian Basin

Figure 16 Continued










ppalachian Basin


Discussion

















ppalachian Basin






86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin





































ppalachian Basin

Figure 16 Continued










ppalachian Basin


Discussion

















ppalachian Basin






86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin
























Figure 16 Continued










ppalachian Basin


Discussion

















ppalachian Basin






86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin




























ppalachian Basin


Discussion

















ppalachian Basin






86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin

























Discussion

















ppalachian Basin






86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin




































ppalachian Basin






86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin





























86Stratigraphy

oftheMiddle

DevonianMarcellus


Basin

Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin
























Figure 23 Continued

Lashand

Engelder87

Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin
























Figure 23 Continued







ppalachian Basin

Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin
























Figure 23 Continued





Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin
























Figu

re23

Continued





Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin
























Figure 23 Continued

Lashand

Engelder91

Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin
























Figu

re23

Continued




ppalachian Basin










Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin

































Figure 24 Continued


Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin
























Figure 24 Continued





ppalachian Basin













ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin




































ppalachian Basin



CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin


























CONCLUSIONS






REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin
























REFERENCES CITED





























Appalachian Basin



























































Appalachian Basin


















































































Appalachian Basin
























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