Catskill Delta Research Articles

Book reviews

Book review in this articleGeochemistry of Organic Matter in the Ocean, by Eugenii A. RomankevichGeomorphology and Soils, ed. by K.S. Richards, R. R. Arnett and S. Ellis.Carbonate Cements, ed. by N. Schneidermann and P. M. Harris.Aspects of a Stratigraphic System. The Devonian, by D. L. DineleyModels in Geomorphology, ed. by Michael J. WoldenbergThe Catskill Delta, ed. by D. L. Woodrow and W. D. Sevon.Biogenic Structures: their Use in Interpreting Depositional Environments, ed. by H. Allen Curran.

Correlation between abnormal pore pressure and tectonic jointing in the Devonian Catskill Delta

Using the preferred orientation of chlorite, we measured vertical compaction in 53 samples from the Devonian Catskill Delta in central New York State. The marine part of this delta contains three levels based on different amounts of vertical compaction. These levels correspond roughly to (1) black shales at the base, (2) prodelta turbidites, and (3) a cap of shallow-water sediments including abundant storm-washed shell hashes deposited within the wave base. The cap is normally compacted, whereas the lower two levels are undercompacted. Tectonic (cross-fold) joints that propagated during the late Paleozoic Alleghanian orogeny are restricted to the deeper, undercompacted levels of the Catskill Delta, whereas unloading (cross-fold) joints pervade the cap. The correlation between undercompaction and the distribution of tectonic joints indicates that abnormal fluid pressure was a key mechanism during the propagation of these joints.

Detailed Deposystem Analysis of Reservoir Sandstones of Catskill Delta, North-Central West Virginia: ABSTRACT

Upper Devonian Hampshire and Lower Mississippian Pocono sandstones were correlated over a 370-mi2 area in north-central West Virginia using 400 gamma-ray logs. Isolith maps show the geometry, position, trend, and distribution pattern of the sandstones. Sandstone belts occur in north-south (strike) trends particularly in the western part (Lewis County), whereas east-west (dip) trending sandstone belts and dendroids generally occur in the eastern part (Upshur County) of the study area. The north-south-trending sandstone belts are interpreted as barrier islands, and their adjacent eastward facies consisting of some plant-rich black shales and thin sandstones are interpreted as lagoonal. Tidal inlets are associated with barrier islands along the strike trend. Sands probably were supplied to the ancient barrier islands by east-trending distributary channels that were affected by both tidal and fluvial processes. East-west cyclic shifting of the barrier islands and the north-south shifting of the were strongly influenced by the paleotopography of the next lower sandstone unit. The nearly 5-mi (8-km) shoreline shift east-west within sand intervals (Fourth, Thirty-foot, Fifty-foot) of these shoreline sandstones probably resulted from combinations of changes in sea level, sediment supply, and differential compaction. The interpreted feeder systems of tidal and fluvial channels trending east-west indicate a history of distributaries shifting with time also. The Hampshire Formation and Pocono Group of north-central West Virginia are inter reted facies of coastal plain-nearshore environments in which marine-dominant deltas characterize the shoreline. End_of_Article - Last_Page 1443------------

Carbonate to Siliciclastic Transitional Facies in Tectonic Delta Complex--Basal Upper Devonian of East-Central New York State: ABSTRACT

In an early stage of building of the Devonian Catskill delta complex of New York state, a submarine topographic high developed 100 km offshore. On the landward side of the high, in an intermittently subsiding trough, sediment from an eastern source terrane accumulated as a landward-thickening and coarsening lithosome (Gilboa Formation) of interlensing gray siltstone and shale and very fine-grained sandstone with subordinate coquinite lenses. Locally abundant in the lithosome are ball-and-pillow structures, thin conglomerates, trace fossils, fossil seed ferns, sole markings, shallow cross-bedding, laminations, and ripple marks. The high was a barrier to clastic influx. On its seaward side, a carbonate lithosome (Tully Formation) formed. This formation has been subdivided i to facies including: abraded calcarenite, chamoside oolite, skeletal calcilutite, barren shaly calcilutite, mound calcilutite, back-mound calcilutite, and encrinite. The effect of combined intermittent subsidence in the basin-margin trough and variation in rate of terrigenous influx is well expressed in the seaward part of the siliciclastic lithosome. Rapid subsidence and low terrigenous influx finally resulted in a short-lived carbonate transgression across the barrier prior to overwhelming of the shelf by terrigenous influx. End_of_Article - Last_Page 270------------

Loading paths to joint propagation during a tectonic cycle: an example from the Appalachian Plateau, U.S.A.

Based on the timing of joint propagation during the history of burial, lithification, deformation and denudation of clastic rocks within sedimentary basins, four types of joints may be distinguished: tectonic, hydraulic, unloading and release. Tectonic and hydraulic joints form at depth prior to uplift in response to abnormal fluid pressures, whereas unloading and release joints form near the surface in response to thermal-elastic contraction accompanying erosion and uplift. Tectonic joints are distinguished from hydraulic joints in that tectonic compaction is a mechanism for achieving abnormal pore pressures leading to the propagation of the former whereas compaction by overburden loading leads to the abnormal pore pressures in the latter case. The orientation of unloading joints is controlled by either a residual or contemporary tectonic stress whereas the orientation of release joints is controlled by a rock fabric. Examples of some of these joints are found within the Devonian Catskill Delta of the Appalachian Plateau, New York. During the Alleghanian Orogeny tectonic joints (cross-fold joints) formed under abnormal pore pressure as indicated by the observation that joints propagated in the siltstones before they developed in shales and by the cross-cutting relationships of folds, cleavage and joints. This sequence is compatible with oil company hydraulic fracture data which show that the least principal stress within sandstone layers is less than that in the intercalated shale layers. Plumose structures indicate that the joints within siltstones propagated as discontinuous rupture events each of which affected less than a meter of bed length. The discontinuous rupturing is compatible with models for natural hydraulic fracturing. Release joints (strike joints) post-date the Alleghanian Orogeny as indicated by abutting relationships within the deeper parts of the Devonian clastic section. Unloading joints are orthogonal to the contemporary tectonic stress field.

Upper Devonian Catskill Delta of West Virginia: ABSTRACT

Oil and gas reservoir rocks of the Upper Devonian of West Virginia were deposited as shoreline sands along a coastal plain characterized by marine-dominant deltas (Catskill delta complex). These sandstones exhibit facies relationships between red beds and interbedded sandstones and shales that shift westward and eastward with offlap and onlap. Outcrop equivalents at Elkins, West Virginia, are correlated with the interval of Balltown to Fourth sands. Subsurface correlation indicates that maximum westward progradation occurred during deposition of the Gordon and Gordon Stray sands, and that transgression mainly characterized the younger Devonian sands of the Thirty-foot, Fifty-foot and Gantz. End_Page 1918------------------------------ Regional correlations suggest that the Bradford-Balltown and Speechly (B sands of Pennsylvania Geological Survey) sands are better developed in northwestern Pennsylvania, whereas the Bayard through Gantz (D sands of Pennsylvania Geological Survey) sands are better developed in northern and central West Virginia, decreasing also in buildup toward southeastern West Virginia. The oil-bearing sandstones occur in strike trend (north-south) in north-central West Virginia connected by feeder channel sandstones with dip trends (east-west). The interpreted fluvial and tidal channels combine to represent distributary channels that supplied the sands to the barrier islands and delta front. Shoreline shifts, with regression and transgression of the ancient sea, caused corresponding changes in dis al-fan accumulations with time. End_of_Article - Last_Page 1919------------

Upper Devonian Deposystems of Catskill Delta, West Virginia: ABSTRACT

The oil and gas reservoir rocks of the Upper Devonian of West Virginia were deposited as shoreline sands along a coastal plain characterized by marine-dominant deltas (Catskill delta complex). The oil-bearing sandstones occur in strike trend (north-south) in north-central West Virginia connected by feeder channel sandstones with dip trends (east-west). In outcrop, the strike-trending sandstones contain occasional marine fossils, are well sorted, and exhibit sedimentary structures that suggest depositional environments ranging from shoreface to tidal delta and back barrier. Channel sandstones with herringbone bedding suggest tidal influence. These beds change to cross-bedding of unidirectional paleoflow origin in upstream fluvial counterparts of red-bed facies. The interpr ted fluvial and tidal channels combine to represent distributary channels that supplied the sands to the barrier islands and delta front. Isolith maps show anastomosing belts trending east-west with both vertical and offset stacking. Stream avulsion and stream piracy probably account for lateral shifting of tidally influenced river distributaries. Gridlike patterns of sandstone belts result from the dynamic interference of tidal-fluvial channels with wave-constructed shoreline barrier islands and bars, complicated by onlap and offlap cycles. Subsurface informally named oil and gas sands generally are multiple sandstones. Detailed correlation of individual sand units is difficult, but it supports the interpretation of a combined influence of wave and tidal-fluvial processes. End_of_Article - Last_Page 1919------------

Flexural Modeling of Devonian Catskill Delta in Eastern United States and Formation of Taghanic Unconformity: ABSTRACT

The Devonian Catskill delta is an exogeosynclinal clastic wedge in the Appalachian basin. Subsidence caused by this load is modeled as flexure of a perfectly elastic crust. Subsidence can be measured accurately in eastern New York and Pennsylvania because of excellent well and outcrop control and the ability to recognize shoreline position. Calculated flexural response to the load of the Erian Series sediments predicts subsidence smaller than observed values, especially in the eastern portion of the delta. It is necessary to postulate an additional tectonic component of subsidence. Additional subsidence is modeled as a cosine curve decaying exponentially with distance from a point deflection of the crust. This model, plus the flexure caused by sediment load, produces subsidence consistent with observations. The flexural response of the crust offers an explanation for an unconformity in black shales that developed during the Taghanic age on the west side of the Appalachian basin, with at least 50 m (165 ft) of expected strata missing. This unconformity expands westward and southwestward End_Page 522------------------------------ from the maximum sediment load. The unconformity is unusual because it formed during a sea level rise (Taghanic onlap) which apparently affected all of North America. Flexural modeling predicts upwarp in central and western New York, western Pennsylvania, and eastern Ohio, and offers a plausible explanation for this unconformity. The tectonic component of the subsidence curve, coupled with the geologic constraints, offers an opportunity to model the location of the Acadian Mountains to the east, which have since been eroded to their roots. End_of_Article - Last_Page 523------------

Depositional Environment and Reservoir Characteristics of Upper Devonian Kane Sandstone in Central Western Pennsylvania: ABSTRACT

Interpretative mapping techniques provide the basis for an environmental analysis of the Upper Devonian Kane sandstone in part of central western Pennsylvania. Stratigraphically, the Kane sandstone is defined as the basal marine sandstone unit of the Upper Devonian Bradford Group. It represents the initial stages of clastic influx accommodated by the prograding Catskill delta complex. In eastern parts of the Appalachian Plateau, it most commonly exhibits an elongate lenticular geometry with long axes oriented normal to subnormal to regional strike. The study area spans the three-county junction of Cambria, Clearfield, and Indiana Counties, where the Kane sandstone has been the target of intense drilling activity. Kane completions in this area are characterized by high initial potentials (up to 20 MMCFGD) and correspondingly high recoverable gas reserves. Gross interval isopachs (G.S.S. and G.I.S.), net sand isopachs, sand percentage, and structure contour maps show that Kane sediments were emplaced as part of a small-scale submarine-fan environment, with a long axis trending west-northwest. A complex suite of subenvironments ranges from submarine channel (proximal) to a radiating complex of small channels at the fan apex, which become broad flat channels and sheetlike sands in a downfan direction. These environments ultimately give way to distal mud facies away from the fan area. Gross interval isopachs of the lower third of the Bradford Group interval show that increased thicknesses of sediment were emplaced along an inferred structural boundary trending west-northwest. This boundary very nearly coincides with a zone of cross strike structural discontinuity observed in the Valley and Ridge province. The interpretations used in this analysis provide useful methods for evaluating future Devonian reservoirs. End_of_Article - Last_Page 1921------------

Stratigraphy and Depositional Environments of Catskill Deltaic Sequence, Northern West Virginia: ABSTRACT

The deltaic sequence (Upper Devonian-Lower Mississippian) is inadequately mapped and subdivided in the subsurface of northern West Virginia (central Appalachian basin). Stratigraphic interpretations are often hindered by the liberal use of drillers' names for noncontemporaneous gas-bearing sandstones. Base-line analysis of 275 gamma-ray logs permits the resolution of lithostratigraphic units in this sequence. Five regionally mappable units are recognized, within which the position, geometry, trend, and distribution of reservoir sandstones are interpreted. Three units are within the Upper Devonian Chemung Formation, and two are considered equivalents of the Hampshire (Upper Devonian) and Pocono (Lower Mississippian) Formations. Stratigraphic cross sections graphically display relative thickness variations of reservoir sandstones and document the inter-tonguing facies of the deltaic sequence that are attributable to cyclic marine transgression and regression, and/or to changing sedimentation or subsidence rates in the basin. Five lithofacies (A-E) are identified by the study of equivalent strata on outcrop. Facies A consists of gray shales and thin-bedded siltstones, interpreted as interbedded hemipelagic shales and turbidites. Facies B is comprised of thick-bedded and amalgamated siltstones and sandstones containing hummocky cross-stratification, representing composite storm deposits of the shelf and slope. Facies C consists of thick-bedded to massive clean sandstones and interbedded red and gray shales, interpreted as barrier-beach and back-barrier deposits. Facies D is dominated by red beds (silty mudstones and siltstones) with some interbedded sandstones, representing vertical accretion and channel deposits of an alluvial plain. Facies E consists of gray sandstones containing marine fossils and greeni h-gray shales (Pocono Formation), interpreted as marine and marginal marine deposits developed during net transgression of the sub-aerial Catskill delta. Contrary to some previous studies, this study indicates these strata are best interpreted within the context of deltaic sedimentation. More specifically, stratigraphic and sedimentologic evidence suggests deposition in a wave- and storm-dominated deltaic complex. End_of_Article - Last_Page 1923------------

Plants of Devonian-Mississippian Black Shales, Eastern Interior, U.S.A.: ABSTRACT

Macrofossils of the New Albany shale and equivalents of Late Devonian of Early Mississippian age in the east-central United States are known from three main floras or assemblages. One is almost entirely composed of Callixylon logs, slabs, End_Page 444------------------------------ and slivers, presumed to be driftwood permineralized after burial. Callixylon fossils are most abundant in the upper part of the Clegg Creek Member of the New Albany shale ()Famennian) and equivalent strata in western New York, Ohio, and contiguous areas, perhaps because these Progymnosperms reached the zenith of their development at that time. They also occur sporadically throughout the New Albany shale and equivalent strata. The principal geographic concentration of Callixylon is in western New York, principally in marine sediments, and on the west side of the Cincinnati arch. Callixylon is also sparsely and sporadically distributed in nearly all areas of outcrop of the Devonian black shales including the New Albany, Antrim, Kettle Point, and Ohio shales, and is found in Kinderhooki n age shales from Illinois and Tennessee. A second, and later, flora consists principally of permineralized wood pieces (phosphatized free-wood or concretions) of stems, rachises, petioles, and possibly even mid-veins of pinnules of diverse members of the Lycopsida, Sphenopsida, Cladoxylales, Coenopteridales, Progymnospermae, and Pteridospermae. A few of these disjunct pieces have been reconstructed into more complete plants known from the Catskill delta in western New York, Pennsylvania, and West Virginia. The principal concentration of these stem and petiolar segments is in the Falling Run Member of Sanderson Formation of the New Albany shale on the west side of the Cincinnati arch in southern Indiana and Kentucky, and in central Kentucky in the low saddle between the Cincinnati arch proper and its southward extension as th Nashville dome. This abundant distribution of minute stem axes and other such small plat fragments strongly suggests the source of these palnts to be a nearby island (Cincinnatia?). Alternatively, it is proposed that they have been concentrated by currents on a very shallow choal on or near a structurally positive submarine rise of the Cincinnati arch, or by floating algal mats in which the waterworn wood and leaf fragments became enmeshed as flotsam near some shore and were transported by these mats to more distant sites before the disintegration of the mats. The third type of macrofossil palnt assemblage is constituted of Foerstia. These plants are considered to be algal in origin and indicate no clear relationship either to distance from shore or depth of water. The main concentration is in middle and lower New Albany shale and equivalents. It is also found sparingly in West Virginia and Michigan and much farther west (one specimen from the Exshaw shale of Montana). End_of_Article - Last_Page 445------------

Fades, topography, and sedimentary processes in the Catskill Sea (Devonian), New York and Pennsylvania

Topography of the floor of the sea bordering the Catskill Delta (referred to here as the Catskill Sea) differed markedly from modern continental-margin configurations. Data from exposures in New York and Pennsylvania indicate that the Catskill Sea floor was a subdued surface with three topographic subdivisions. Nearest the shore was the basin margin , a low-gradient, shelf-like surface. Seaward, this gave way to the clinoform , the gradient of which was not much greater. The clinoform merged seaward into the basin floor. A sandstone and shale sequence with abundant fauna developed on the basin margin; thin turbidites and gray, silty shales with both transported and pelagic fauna were deposited on the clinoform and silt-stones and black shales with pelagic fauna formed on the basin floor. Boundaries between facies and between the inferred topographic subdivisions on which they formed reflect the different sedimentary processes active on the sea floor and not geophysical discontinuities. The basin margin was affected mainly by deltaic processes, waves, tides, and, perhaps, internal waves. Turbidity currents deposited the majority of clinoform sediments with a lesser contribution from pelagic sedimentation. Pelagic deposits dominate on the basin floor.

Stratigraphic and Sedimentologic Controls of Gas in Shale--Example from Upper Devonian of Northern Ohio

The gas-bearing Devonian Ohio and Chagrin Shales along Lake Erie have produced marginally commercial volumes of gas for over 100 years. These shales thin depositionally westward from a maximum of 2,000 ft (600 m) at the Pennsylvania-Ohio border to less than 500 ft (180 m) near Sandusky, Ohio. West of Sandusky, they have been truncated by Holocene and preglacial erosion on the Findlay arch. Westward thinning is accompanied by a facies change from gray shale and siltstone in the east to black shale in the west. The Ohio and Chagrin Shales were deposited on a turbidite slope and basin plain and all were derived from the Catskill delta on the east. The Late Devonian epeiric sea was at least 700 ft (215 m) deep and was poorly oxygenated. There are three major lithologies--black bituminous shale, greenish-gray shale, and siltstone. Black bituminous shale is most abundant in the west, whereas gray to greenish-gray shale and siltstone are most abundant in the east, where they constitute 75% of the section. Zones productive of natural gas occur most commonly in the greenish-gray shale and siltstone. These rocks contain abundant thin silt laminae which probably act as permeable conduits and reservoirs for gas. This gas appears to have had its origin in underlying black shales. Sedimentologic study helps explain the origin of both small- and large-scale interbedding of the greenish-gray and black bituminous shale and provides guides for improved gas exploration in the Appalachian basin.

Minnehaha Member of Upper Devonian Brallier and Scherr Formations of Central Appalachians: ABSTRACT

The Minnehaha member of the Upper Devonian Brallier and Scherr formations has been informally named, and its use as a time band within the marine strata of the Devonian Catskill delta complex of the central Appalachians is suggested. The coarse clastic bundle of the Minnehaha member can be identified in both outcrop and subsurface for approximately 150 mi (235 km) along the Allegheney Front from Bedford County, Pennsylvania, to Greenbrier County, West Virginia. The Minnehaha member is 20.9 to 98.4 ft (6.37 to 30.0 m) thick, consisting of interbedded very thinly to thickly bedded medium-gray siltstones and olive gray shales, with some grayish-red siltstones and shales. The Minnehaha member was deposited by turbidity currents in generally unchanneled suprafan environments during the earliest Cohocton Stage. Three major, time persistent, depositional systems are recognized as having contributed to the Minnehaha member. End_Page 1171------------------------------ They are in order, from northeast to southwest, the Fulton, Mouth of Seneca, and Augusta depositional systems. The relatively brief time interval of Minnehaha deposition by three separate depositional systems strongly suggests a sea-level drop in the Appalachian basin as a causal factor. The overlapping of submarine fan deposits from three depositional systems could enhance the hydrocarbon reservoir potential of the Minnehaha member. The Minnehaha member may be the shoreward correlative of the gas productive Sycamore siltstone of north-central West Virginia. End_of_Article - Last_Page 1172------------

Tectono-Climatic Model for Origin of Devonian-Mississippian Black Gas Shales of East-Central United States: ABSTRACT

Devonian-Mississippian black gas shales in east-central United States form a distinctive stratigraphic interval reflecting low clastic input, high organic productivity, and anaerobic conditions in a stratified inland equatorial sea. These conditions apparently originated because of interactions between tectonic and climatic factors unique to North America at this time. The Black-Shale Sea developed over an expanse of slowly subsiding craton west of the Acadian mountains. These mountains provided the major source of clastics to the sea and periodically formed high orographic barriers crossing the paleoequator. Subsidence on the adjacent craton, particularly in the marginal foredeep (Appalachian foreland basin), accompanied uplift in the Acadian range. When uplifted, these mountains created barriers to moisture-laden, easterly trade winds, forming a rain shadow west of the mountains and reducing clastic input to the Black-Shale Sea. Clastic input reduced, deposition of organic-rich muds dominated. Concomitant subsidence caused this sediment-starved sea to transgress over the Catskill delta and other parts of the craton. During tectonic quiescence, subsidence slowed and the mountains were erosionally lowered sufficiently that the trade winds crossed and delivered precipitation to the mountains causing increased clastic influx and westward deltaic progradation into the Black-Shale Sea. Seven major cycles of alternating black shale and deltaic clastics occur in the Catskill delta. Few of the progradations migrated beyond the foredeep, hence, sediment-starved conditions persisted in western parts of the sea. The equatorial nature of the sea and progressive deepening within it created a stratified water column (pycnocline) that prevented oxygenation of deeper bottom waters. Organic-rich muds deposited there were preserved in the anaerobic conditions that resulted. Eventually, the sea deepened sufficiently that upwelling phosphate-rich, oxygen-poor, oceanic waters entered locally from the continental margin. End_of_Article - Last_Page 923------------

Paleoenvironmental distribution of trace fossils in the catskill deltaic complex, New York State

The Devonian Tully clastic equivalents and associated rocks of east-central New York State were deposited in fluvial to offshore environments associated with the Catskill delta. These depositional environments have been well defined by Johnson and Johnson and Friedman. The compositional and textural immaturity of the sandstones (immature to submature graywacke) and nearly ubiquitous micro-cross-lamination indicate that rate of sediment supply exceeded rate of reworking. Four of the ichnofossils, including Arenicolites (“small form”), ? Teichichnus, Spirophyton, and large vertically oriented burrow-like structures of probable biological origin are found in narrow paleoenvironmental ranges, within alluvial, tidal, and nearshore facies. However, the other eleven trace fossils, including the most abundant types [ Arenicolites (“large form”), arthropod traces ( Diplichnites, Cruziana, ?Isopodichnus, Rusophycus), Bifungites, ?Chondrites, Skolithos (2 types), Zoophycos, large primarily intrastratally-produced burrows, and simple surficial trails ] occur in rocks deposited under diverse environmental conditions. Their distribution is not clearly related to environment or substrate texture. Factors contributing to the broad lateral distribution of most of the biogenic structures include: (1) the continual influx of sediment from the east, which may have excluded some forms and inhibited the development of stable, environmentally distinct ichnocoenoses, and (2) gradual changes in optimal behavioral patterns resulting from environmental transitions occurring over large geographic distances. The gradational nature of these changes may have exaggerated the broad environmental ranges of the trace-producing animals.

Silurian-Devonian Embayment into Appalachia: ABSTRACT

Several Silurian and Devonian formations, traced along central Appalachian outcrop belts, undergo anomalous changes in lithology, thickness, and faunal content in the area of Pendleton County, West Virginia. Hematitic sandstones are replaced by nonred sandstones, other sandstones change to shales, shale formations thin and pinch out, and Catskill red beds are replaced by nonred clastics. These changes represent a move from nearshore to more offshore deposition within an embayment along the western shoreline of Appalachia. The principal Silurian sandstones, the Tuscarora, Keefer, and Williamsport, all undergo facies changes in this area, becoming finer grained, argillaceous, and/or calcareous. Hematitic nearshore sandstones of the Rose Hill are replaced by nonred sandstones in the embayment. The Rochester and Rose Hill shales are thickest in, and largely confined to, the embayment; younger shales, the Big Mountain and Mandata, are replaced by sandstones south of the embayment. McKenzie shales contain more interbedded limestones in the embayment, and the fossiliferous middle Tonoloway Limestone contains a different fauna there than in adjacent areas. During Middle Devonian time, thicker, deeper water Needmore Shale beds in the area were flanked by shallower water facies of the Onesquethaw. The Mahantango Formation also is thickest in this area and thins abruptly to the south. Throughout this time two provenances supplied detritus, one east of West Virginia's eastern panhandle and the second in central Virginia. The Pendleton embayment was situated between these two regions that occasionally prograded westward, accentuating the embayment. For the final Devonian regression these areas are End_Page 846------------------------------ referred to as the Fulton and Augusta lobes of the Catskill delta, separated by Grant bay. End_of_Article - Last_Page 847------------

Late devonian facies inter-relationships in bordering areas of the North Atlantic and their palaeogeographic implications

Late Devonian faunal and facies relationships are examined in seven around the North Atlantic — in eastern North America, Greenland, western Europe and northwest Africa. A shallow marine (“littoral”) environment, characterized by the genus Cyrtospirifer, is distinguished from a deeper water (“bathyal”) goniatite-conodont milieu on the one hand, and from the “Old Red Sandstone” terrestial facies bearing plant an d fresh-water fish remains on the other. Current or source directions indicate that an “Acadian Divide” existed, separating west-flowing drainage systems in North America from those flowing to the east on the Afro-European side. All species of the osteolepid Latvius, and the majority of species of Glyptopomus are found on the eastern flank. Conversely, the earliest amphibian, Ichthyostega, may have been confined to the western side of the divide. Palaeogeographic reconstruction places northwest Africa fairly close to the Catskill Delta in the Late Devonian, thus accounting for the presence of an “American fauna” in the former. North—south migration of littoral faunas along the Afro-European shores was, however, apparently inhibited.

Gas-Producing Submarine-Fan Deposits of Catskill Delta Complex in North-Central West Virginia: ABSTRACT

Gas-Producing Submarine-Fan Deposits of Catskill Delta Complex in North-Central West Virginia: ABSTRACT

Association of Lithologies and Sedimentary Structures in Marine Deltaic Paleoenvironments

ABSTRACT Rock types and sedimentary structures in the New York Devonian nearshore marine Catskill Delta provide inter-relationships that can be used to identify other deltaic paleoenvironments. Triangular prisms with four rock types as end members were constructed in order to display the range in lithology existing in outcrops where a given sedimentary structure was identified. The structural prisms were then arranged according to the similarities and differences of their patterns. This arrangement resulted in a structural ranking: low rank-flute casts to high rank-oscillation ripples. A low rank signifies an environment of low energy and hydrodynamic unsteadiness (variability) whereas high rank indicates higher energy and a more hydrodynamically steady state. Siltstones, shales and mudstones end to be associated with the former, sandstones and rudites with the latter. Lithologic and structural data have been reorganized according to an earlier field-based paleoenvironmental classification. Higher ranked structures and coarser sediments were significantly abundant in the delta front and distributary bar environments but significantly rare in the open shelf and prodelta environments. Just the opposite is true for the finer-grained sediments and low-ranked structures. The platform, estuarine and lagoonal paleoenvironments provide less well-defined patterns attributable to the greater range of energy levels operating there. These associations provide criteria that can help to distinguish the paleoenvironments in other marine deltaic settings.