uAbstract

uIntroduction

uMarcellus-Stafford  interval

uSkaneateles-Tichenor interval

uMoscow-Tully interval

uGeneseo-West River interval

uMiddlesex-Rhinestreet interval

uConclusions

uReferences

uAbstract

uIntroduction

uMarcellus-Stafford  interval

uSkaneateles-Tichenor interval

uMoscow-Tully interval

uGeneseo-West River interval

uMiddlesex-Rhinestreet interval

uConclusions

uReferences

uAbstract

uIntroduction

uMarcellus-Stafford  interval

uSkaneateles-Tichenor interval

uMoscow-Tully interval

uGeneseo-West River interval

uMiddlesex-Rhinestreet interval

uConclusions

uReferences

uAbstract

uIntroduction

uMarcellus-Stafford  interval

uSkaneateles-Tichenor interval

uMoscow-Tully interval

uGeneseo-West River interval

uMiddlesex-Rhinestreet interval

uConclusions

uReferences

uAbstract

uIntroduction

uMarcellus-Stafford  interval

uSkaneateles-Tichenor interval

uMoscow-Tully interval

uGeneseo-West River interval

uMiddlesex-Rhinestreet interval

uConclusions

uReferences

uAbstract

uIntroduction

uMarcellus-Stafford  interval

uSkaneateles-Tichenor interval

uMoscow-Tully interval

uGeneseo-West River interval

uMiddlesex-Rhinestreet interval

uConclusions

uReferences

uAbstract

uIntroduction

uMarcellus-Stafford  interval

uSkaneateles-Tichenor interval

uMoscow-Tully interval

uGeneseo-West River interval

uMiddlesex-Rhinestreet interval

uConclusions

uReferences

uAbstract

uIntroduction

uMarcellus-Stafford  interval

uSkaneateles-Tichenor interval

uMoscow-Tully interval

uGeneseo-West River interval

uMiddlesex-Rhinestreet interval

uConclusions

uReferences

uAbstract

uIntroduction

uMarcellus-Stafford  interval

uSkaneateles-Tichenor interval

uMoscow-Tully interval

uGeneseo-West River interval

uMiddlesex-Rhinestreet interval

uConclusions

uReferences

Introduction

(Figures 1-1 – 1-3)

Ettensohn (1985, 1994) has demonstrated that major stratigraphic patterns of Middle and Upper Devonian black shale units, specifically their westward transgression over time, can be described in terms of four tectophases, each one defined by four stages, including (1) the inception of tectonism and consequent rapid subsidence of a peripheral basin and consequent accumulation of black shale; (2) impending collision and associated regression and accumulation of gray shale and siltstone; (3) collision accompanied by widespread uplift and development of regional disconformities; and (4) tectonic quiescence and widespread accumulation of limestone in slowly transgressing seas. 

However, local basin dynamics (i.e., development of forebulges inheretid from earlier events) appear to have played an important role in the accumulation of Middle and Upper Devonian black shale in the western New York, northwest Pennsylvania, and eastern Ohio region of the Appalachian Basin.

Marcellus Shale - Stafford Limestone Interval

(Figures 1-4 – 2-7)

	Figure 1-4. Stratigraphic column, showing positions and lithologies of Tully Limestone;  Hamilton Group (including Stafford Limestone, Oatka Creek Shale, Cherry Valley Limestone, and Union Springs Shale); and Onondaga Limestone.
	Figure 2-1. Isopach map of the Union Springs Shale (thickness in feet). The red circle shows the location of well 22963.
	Figure 2-2. Isopach map of the Oatka Creek Shale (thickness in feet); white dashed line denotes the axis of minimum thickness of the Oatka Creek Shale.
	Figure 2-3. The thickening of the Oatka Creek Shale to the west reflects the thickening of the gray shale facies that overlies the organic-rich basal black shale facies. Well locations are shown on the Oatka Creek facies map (Figure 2-5).
	Figure 2-4. Gamma-ray log showing the Marcellus Shale-Stafford Limestone interval (see Union Springs Shale isopach [Figure 2-1] for location).
	Figure 2-5. Facies map showing the percentage of black shale facies of the Oatka Creek Shale (contours in 10% increments). Note the locations of the well logs used to display the westward increase in thickness of the Oatka Creek (Figure 2-3).
	Figure 2-6. Isopach map (thickness in feet) of the basal organic-rich black shale facies of the Oatka Creek Shale showing (1) relatively constant thickness westward from the axis of minimum thickness and (2) rapid thickening of the organic-rich facies to the east, in the direction of deepening of the basin.
	Figure 2-7. Isopach map (thickness in feet) of the Stafford Limestone (red circle shows location of the field photograph on right).  Click to view in sequence maps of Union Springs, Oatka Creek (3 maps), and Stafford.

The transition from the Onondaga Limestone to the Union Springs Shale marks the start of Ettensohn’s (1985) second tectophase as the stable platform started to subside as a consequence of thrust loading in the hinterland. The local disappearance of units of the Onondaga Limestone suggests that the contact is erosional (e.g., Rickard, 1984). The Union Springs black shale onlaps the eroded surface to the WNW. However, appears to have further eroded the Onondaga to the west. A brief period of stabilization, perhaps partly as a consequence of a eustatic rise in sea level, is marked by accumulation of the Cherry Valley Limestone, which overlies the Onondaga Limestone in the absence of the Union Springs Shale. 

The widespread accumulation of the Oatka Creek Shale over much of the Appalachian Basin reflects regional, rapid subsidence of the basin at the onset of Ettensohn’s (1985) second tectophase (Hamilton-Smith, 1993). However, variations in the thickness of the Oatka Creek Shale suggest a somewhat more complex behavior. 

Unlike an other Devonian shale units in this region of the Appalachian Basin, the Oatka Creek Shale thicknens gradually to the west from a NNE-SSW axis trending through Wyoming, Cattaraugus, and Chautauqua counties New York, into Warren and McKean counties, Pennsylvania. The Oatka Creek Shale thickens more rapidly to the east of this line. 

Accumulation of the Stafford Limestone marks another period of tectonic quiescence and relatively clear water. The Stafford is thickest a bit to the west of the area of minimum thickness of the Oatka Creek Shale suggesting that this region of the basin was elevated. The thinning and eventual loss of the Stafford to the west and east probably reflects a transition into deeper water and passage into more shaley (deeper) facies.

Skaneateles Shale - Centerfield Limestone - Ludlowville Shale - Tichenor Limestone Interval

(Figures 2-8 – 2-13)

	Figure 2-8. Stratigraphic column, showing position and lithology of Tully Limestone, Hamilton Group, and Onodaga Limestone.
	Figure 2-9. Isopach map of the Skaneateles Shale (thickness in feet) showing locations of wells shown on the Skaneateles (Levanna Shale) correlation diagram.
	Figure 2-10. Isopach map of the Centerfield Limestone (thickness in feet).
	Figure 2-11. Details of the Levanna Shale at the base of the Skaneateles Shale. Note its disappearance to the west.
	Figure 2-12. Isopach map of the Ludlowville Shale (thickness in feet). Note the reduced thickness in the northern region of the study area where the Centerfield Limestone was thickest.
	Figure 2-13. Isopach map of the Tichenor Limestone shale (thickness in feet). The anomalously high thickness (> 20 feet) of the Tichenor in Chautauqua County, NY, extending south into eastern Warren County, PA, remains unresolved. It may reflect carbonate sedimentation on a topographic high in this region of the basin. Variable thickness in the area denoted by the white circle reflects erosion at the end of Moscow shale sedimentation.  Click to view in sequence isopach maps of Skaneateles, Centerfield, Ludlowville, and Tichenor.

The change from the Stafford Limestone to the Skaneateles Shale reflects the tectonic reactivation of the basin. The bottom part of the Skaneatele in the eastern portion of the study area is composed of black shale that can be difficult to differentiate from the underlying Oatka Creek Shale. These deposits, the Levanna Shale, tell of rapid subsidence and onlap to the west as the organic-rich deposits gave way to organic-lean gray shale. The Centerfield Limestone marks a brief period of tectonic stabilization and relatively clear water. However, basin subsidence and further progradation of clastic deposits is marked by accumulation of the Ludlowville Shale, which further onlapped the Oatka Creek Shale where the Stafford Limestone is absent. This event was not accompanied by deposition of organic-rich shale. An interlude in tectonic activity is marked by deposition of the Tichenor Limestone.

Moscow Shale - Tully Limestone Interval

(Figure 2-14 - 2-19)

	Figure 2-14. Stratigraphic column, showing positions and lithologies of Tully Limestone, Moscow Shale (and of other units of the Hamilton Group), and Onondaga Limestone.
	Figure 2-15. Isopach map of the Moscow Shale (thickness in feet) showing location of the cross-section (Figure 2-16). Dashed white line shows the approximate depositional strike of the Moscow Shale.
	Figure 2-16. Stratigraphic cross-section, showing Tully Limestone above eroded Moscow Shale.
	Figure 2-17. Isopach map (thickness in feet) of the Tully Limestone showing the location of the cross-section in Figure 2-19. Note the change in the area of coverage of the map from previous isopach maps. Dashed while line defines the trace of the Clarendon-Linden Fault (CLF).
	Figure 2-18. Isopach map (thickness in feet) of the Tully Limestone with isopachs of the Moscow Shale (heavy blue lines). Note the coincidence of the region of greatest erosion of the Moscow Shale with that of the Tully Limestone.
	Figure 2-19. Cross-section, showing position of Tully Limestone and that of Tichenor Limestone, which have been confused in the subsurface.

The abrupt change from the Tichenor Limestone to the Moscow Shale reflects subsidence of the basin and onlap of the Moscow Shale to the northwest. However, the isopach pattern of the Moscow Shale, specifically the saddle in the depositional strike in Cattaraugus County, NY, south into northern McKean County, PA, suggests that as much as 100 feet of the Moscow Shale was eroded in this area of the basin. Cross-sections (Figures 2-16, 2-19) reveal that the Tully Limestone locally rests on the Tichenor Limestone, the intervening Moscow Shale having been completely eroded in these areas (northern and western Chautauqua County, NY). 

Accumulation of the Tully Limestone over the eroded Moscow Shale marks the end of Ettensohn’s (1985) second tectophase (Figure 2-16). Carbonate sediment was deposited under conditions of tectonic inactivity following uplift of the Moscow Shale and slow transgression in clastic-deficient water (Ettensohn, 1985). However, tectonic quiescence was terminated by localized uplift and erosion of the Tully Limestone, especially along a north-south-trending axis coincident with that region of greatest erosion of the Moscow Shale. 

There has been a good amount of confusion regarding the Tully Limestone in the subsurface of western NY and northwest PA. Indeed, some have confused the Tully with the Tichenor Limestone, especially where the Tully rests unconformably on the Tichenor. Wright (1973), for example, followed this convention maintaining that the Tully Limestone is not present in the subsurface of Chautauqua County, NY, and northwest PA. This interpretation was accepted by de Witt et al. (1993). However, Rickard (1989) offered the dissenting view that the Tully can be recognized in western NY, an interpretation fully supported by the present study (e.g., Figure 2-19). The problem as recounted by Rickard (1989) was that Wright (1973) and many drillers (as revealed by review of drilling records) confused the Tully Limestone with the Tichenor Limestone and vice versa.

Geneseo - Penn Yan - West River Shale Interval

(Figures 3-1 – 3-4)

	Figure 3-1. Stratigraphic column showing positions of West River, Penn Van, and Geneseo shales.
	Figure 3-2. Stratigraphic cross-section of Pen Yan – West River succession, Geneseo Shale, Tully Limestone, Moscow Shale, and Tichenor Limestone.
	Figure 3-3. Isopach map of the Geneseo Shale (thickness in feet).
	Figure 3-4. Isopach map of the Penn Yan - West River Shale interval (thickness in feet) showing the location of the cross-section (Figure 3-2).  Click to view in sequence isopach maps of the Geneseo and Penn Yan – West River.

Deposition of the Geneseo Shale reflects rapid subsidence to a depth of perhaps 200 m (Ettensohn, 1985) induced by crustal loading in response to Acadian plate convergence in tandem with major global transgression (Dennison and Head, 1975). The organic-rich deposits, which mark the start of Ettensohn’s (1985) third tectophase, onlapped the eroded Tully Limestone and Moscow Shale (the Tagahanic unconformity; Johnson, 1970) extending over the topographically positive area responsible for erosion of the Moscow Shale and, subsequently, the Tully Limestone. The Geneseo was onlapped by the Penn Yan - West River Shale interval, which appears to have entered the basin from the southeast as the rate of subsidence diminshed. These units can be differentiated in the field, the Penn Yan comprising laminated dark gray shale and the West River being dominated by gray organic-lean shale. However, no attempt was made to make this distinction in the subsurface. Still, correlation of thin calcareous intervals in the Penn Yan - West River succession demonstrate onlapping of these deposits over the Geneseo Shale and older strata.

Middlesex Shale - Cashaqua Shale - Rhinestreet Shale Interval

(Figures 3-5 – 3-7)

	Figure 3-5. Stratigraphic column showing positions of Rhinestreet, Cashaqua, and Middlesex shales.
	Figure 3-6. Isopach map of the Middlesex Shale (thickness in feet), with stratigraphic column of Rhinestreet, Cashaqua, and Middlesex shales.
	Figure 3-7. Isopach map of the Cashaqua Shale (thickness in feet).
	Figure 3-8. Isopach map of the Rhinestreet Shale.  Click to view in sequence isopach maps of Middlesex, Cashaqua, and Rhinestreet.

The Middlesex Shale accumulated over the West River Shale extending farther to the northwest than the Geneseo black shale. TheMiddlesex organic-rich shale reflects renewed tectonic activity in the Acadian thrust belt and/or a eustatic rise in sea level (T-R Cycle IIc; Johnson et al., 1985). The topographic welt that resulted in erosion of the Tully Limestone had subsided by Middlesex time leaving no imprint on these and subsequent deposits.

Conclusions 

The record of Acadian thrust tectonics in the Middle Devonian clastic succession of the Appalachian Basin begins with the Marcellus black shale, specifically the Union Springs and Oatka Creek shales. The former records initial subsidence of the basin following accumulation of the Onondaga Limestone during a period of tectonic quiescence at the end of tectophase one (Ettensohn, 1985; Ver Straeten and Brett, 2000). The organic-rich deposits may have onlapped a forebulge generated by the same tectonic activity that had initiated subsidence. Accumulation of the Oatka Creek Shale and equivalents from New York well into Ohio and Pennsylvania tells of widespread subsidence during tectophase two. However, deposition of the Oatka Creek Shale appears to have been coeval with development of a positive element or welt in western New York that reduced accommodation space thereby favoring only a thin Oatka Creek sequence here. The inferred position of the Oatka Creek topographic high west of the final position of the Onondaga forebulge suggests that the onset of tectophase twowas accompanied by westward migration of the forebulge and basin axis. Accumulation of the balance of the Hamilton Group records further forward migration of the basin axis punctuated by periods of tectonic stability and deposition of carbonate. The basin underwent uplift and erosion at the end of Hamilton time resulting in the removal of ~ 100 feet or more of the Moscow Shale, locally cutting into the underlying Tichenor Limestone. A lull in tectonic activity and a eustatic rise in sea level is marked by deposition of the Tully Limestone over the eroded Moscow Shale on what may have been a broad forebulge. This brief interlude of tectonic inactivity was terminated by uplift and erosion of the Tully Limestone. The “two-sided” nature of truncation of the Tully in western New York extending into Pennsylvania demonstrates the local nature of maximum Tully erosion (e.g., Brett et al., 1990) placing it a bit to the east of the locus of maximum pre-Tully erosion of the Moscow Shale. This may reflect a small amount of retrograde movement of the welt that occurred during the brief period of thrust relaxation recorded by the Tully Limestone. Renewed tectonc activity in the Acadian thrust belt (third tectophase) and consequent rapid subsidence of the basin in tandem with a eustatic rise in sea level, resulted in deposition of the Geneseo black shale. The subsequent Middlesex and Rhinestreet black shales reflect further westward migration of the basin axis unaffected by those positive elements that had shaped the stratigraphic architecture of the Middle and Upper Devonian succession of western New York and northwest Pennsylvania.

References 

Brett, C.E., Goodman, W.M., and LoDuca, S.T., 1990, Sequences, cycles, and basin dynamica in the Silurian of the Appalachian Foreland Basin: Sedimentary Geology, v. 69, p. 191-244.

de Witt, W., Jr., and Colton, G.W., 1978, Physical stratigraphy of the Genesee Formation (Devonian) in western and central New York: U.S. Geological Survey Professional Paper 1032-A, p. A1-A22.

Dennison, J.M., and Head, J.W., 1975, Sea-level variations interpreted from the Appalachian Basin Silurian and Devonian: American Journal of Science, v. 275, p. 1089-1120.

Ettensohn, F.R., 1985, The Catskill Delta Complex and the Acadian Orogeny: A model, in Woodrow, D.L., and Sevon, W.D., eds., The Catskill Delta: GSA Special Paper 201, p. 39-49.

Ettensohn, F.R., 1994, Tectonic controls on formation and cyclicity of major Appalachian unconformities and associated stratigraphic sequences: SEPM Concepts in Sedimentology and Paleontology #4, Tectonic and Eustatic Controls on Sedimentary Cycles, p. 217-242.

Hamilton-Smith, T., 1993, Stratigraphic effects of the Acadian orogeny in the authochthonous Appalachian basin, in Roy, D.C., and Skehan, J.W., eds., The Acadian orogeny: recent studies in New England, Maritime Canada, and the autochthonous foreland: GSA Special Paper 275, p. 153-164.

Johnson, J. G., 1970, Taghanic onlap and the end of North American provinciality: GSA Bulletin, v. 81, p. 2077-2106.

Johnson, J. G., G. Klapper, and C. A. Sandberg, 1985, Devonian eustatic fluctuations in Euramerica: GSA Bulletin, v. 96, p. 567-587.

Rickard, L.V., 1984, Correlation of the subsurface Lower and Middle Devonian of the Lake Erie region: GSA Bulletin, v. 95, p. 814-828.

Rickard, L.V., 1989, Stratification of the subsurface low and mid-Devonian of New York, Pennsylvania, Ohio, and Ontario: New York State Museum and Science Map and Chart Series 39, 59 p.

Ver Straeten, C.A., and Brett, C.E., 2000, Bulge migration and pinnacle reef development, Devonian Appalachian Foreland Basin: Journal of Geology, vol. 108, p. 339-352.

Wright, N.A., 1973, Subsurface Tully Limestone New York and northern Pennsylvania: New York State Museum and Science Service, Map and Chart Series Number 14, 15 p.

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