Alan C. Donaldson

Outcrop Expression of Late Devonian Transgressive-Regressive Cycles along Catskill Delta Complex Basin Margin of Central West Virginia: ABSTRACT

The Upper Devonian Catskill delta complex prograded westward across the central Appalachian basin in response to eustatic fluctuations in sea level and high rates of sediment supply associated with the Acadian orogeny. Excellent outcrops of Catskill delta complex basin-margin facies, located near Elkins, West Virginia, record a hierarchy of transgressive-regressive (T-R) cycles that formed as the Catskill shoreline regressed across east-central West Virginia during the middle Famennian. Subsurface mapping of intervals studied in outcrop indicates three distinct scales of T-R cycles based on the magnitude and lateral continuity of shoreline shift and the thickness of enclosed strata. Major cycles represent regional shifts of 30-50 mi (48-80 km), and are roughly 350 ft (100 m) thick. Intermediate cycles indicate more localized shoreline shifts of 15-25 mi (25-40 km), and are approximately 100-150 ft (30-50 m) thick. Minor cycles are expressed as local and minor shifts of less than 5 mi (8 km), and are from 10 to 30 ft (3-10 m) thick.

Lithostratigraphic Analysis of Huntersville Chert of Central Appalachians: ABSTRACT

The Huntersville Chert (Onesquethawan Stage) of the central Appalachians was deposited in a detrital sediment-starved basin where a restricted sea hosted mainly silicisponges of probable Demospongid fauna. The Huntersville Chert grades into the Onondaga Limestone to the west and the Needmore Shale to the east. These Onesquethawan rocks record an initial transgression followed by regression, maximum transgression, and a final regression. Basement sub-blocks as growing structures influenced sedimentation. Differential subsidence of basement sub-blocks and eustatic changes in sea level periodically exposed the basin margins or allowed reworking of low-energy shoreline and shoal sediments. Five mappable stratigraphic units are recognized in the Onesquethawan Stage in the cher -filled basin covering the Rome trough in northern West Virginia, southwestern Pennsylvania, and northeastern Ohio. Shale tongues extending from the east interbed with the chert where the eastern West Virginia arch was low in northern West Virginia and western Maryland, but do not to reach the basin center. Carbonates accumulated over the shelf to the west of the chert basin and periodically over parts of the southern, eastern, and central arches. A moderately steep ramp is interpreted for the facies change from chert to limestone in proximity to the western margin of Rome trough. Are ancient reefs located at this shelf margin? The upper chert lithofacies is the most productive reservoir within the Huntersville. End_of_Article - Last_Page 1435------------

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 sanstones 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 interpreted 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.

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------------

Tectonic Controls on Late Paleozoic Sedimentation in Western West Virginia: ABSTRACT

Tectonic patterns had a significant influence on the late Paleozoic Berea, Loyalhanna, and Pittsburgh-Sewickley sandstone units in western West Virginia. The depocenter was in the southwest during Early Devonian Berea deposition, southeast when the Mississippian Loyalhanna (Big Injun) sands filled submarine valleys, and northwest during Late Pennsylvanian when the Pittsburgh and Sewickley (Monongahela Group) deltaic sandstones were deposited. Western West Virginia tectonically was on a relatively stable platform west of the Appalachian trough. Relative rates of supply and subsidence in the trough influenced the major changes in regional paleoslopes. Shallow downwarped axes on the platform oriented perpendicular to the trough also exerted a subordinate but important tectonic control on sedimentation. Characteristics of shallow-water deposition are shared by the Berea, Loyalhanna (Big Injun), and Monongahela sandstone units. However, the interpreted submarine valley-fill depositional environment of the Loyalhanna (Big Injun) is considerably different from the deltaic environment suggested for the Berea and Monongahela sandstones. End_of_Article - Last_Page 844------------