No description available.

No description available.

Early Pennsylvanian, coal-bearing, siliciclastic strata of the Breathitt Group within the Pocahontas Basin, southwestern Virginia, define a southeasterly thickening clastic wedge deposited in continental to marginal marine environments influenced by recurring, high-magnitude relative sea-level fluctuations and low-frequency changes in tectonic loading. A robust dataset of >1200 well logs, cores and numerous outcrops allowed a unique review of the Central Appalachian lithologic record during both the Late Paleozoic Ice Age and onset of the Alleghanian Orogeny. The tropical depositional landscape produced stacked deposits of braided-fluvial channels, broad alluvial plains, tidally-influenced estuaries and small deltas. Trends in facies associations allowed development of a high-resolution sequence stratigraphic architecture based on regional flooding surfaces and bounding discontinuities. Analysis of vertical stacking patterns of lithofacies on regional cross-sections identified 15 widespread, unconformity-bounded depositional sequences with an average duration of ~80 kyr based on available geochronology. Glacioeustatic control on stratigraphic architecture is supported by corresponding sequence duration within the short-eccentricity periodicity of the Milankovitch band, as well as the magnitude and extent of rapid facies shifts, suggesting that far-a-field variations in overall Gondwanan ice-sheet size and volume impacted base-level changes in the tropical basin. The progressive increase in magnitude of transgressions, as indicated by brackish-marine ichnofacies and other faunal indicators within regional high-frequency transgressive system tracts, indicate extrabasinal trends in ice-volume and eustasy. High-frequency eustatic sequences are nested within four asymmetric composite-sequences, attributed to low-frequency variations in tectonic accommodation. Evidence for tectonic forcing on foreland-basin accommodation is based on abrupt facies shifts, angular stratal terminations and wedge-shaped composite-sequence geometries. Spatial and temporal trends in facies associations within composite-sequences reveal episodic variation in tectonic loading overprinted by recurring high-frequency eustatic events. Petrology and detrital-zircon geochronology indicates that sediment was derived from low-grade metamorphic Grenvillian-Avalonian terranes and recycling of older Paleozoic sedimentary rocks uplifted as part of the Alleghanian orogen towards the southeast and, in part, from the Archean Superior Province to the north. Applications of the observed facies distribution and petrophysics of these coal-bearing sedimentary rocks indicate numerous confining intervals within regional mudstones overlying coalbeds, suggesting the potential for beneficial geological storage of CO2 through enhanced-coal-bed-methane recovery. / Ph. D.

Late Mississippian, Mauch Chunk Group strata constitute a westward-thinning clastic wedge of strata up to 1000m thick that developed in the Central Appalachian Basin over a ~ 7 million year time interval. Included within the Mauch Chunk Group are multiple incised-valley fills and a distinctive prodeltaic succession of laminated sandstones and mudstones. Calculated estimates of drainage basin areas for incised-valley fills in the Mauch Chunk Group range from > 1,000,000 km2 for the Stony Gap Sandstone to < 100,000 km2 for the Princeton Formation. Drainage area estimates are consistent with detrital zircon geochronology and petrographic data and suggest that the Stony Gap and Ravencliff incised-valley fills were derived from distal, northern and northwestern cratonic sources that dispersed sediment into NE-SW-oriented, longitudinal incised-valley drainages and that the Princeton Formation was derived from proximal tectonic highland sources along the eastern margin of the Appalachian Basin which dispersed sediment into a transverse incised-valley. The Pride Shale overlies the Princeton incised valley fill and records a hierarchy of tidal periodicities is preserved in the Pride Shale. Microlaminated, semi-diurnal sandstone-siltstone/shale couplets record the dominant ebb tide of the day. Up to 17 semi-diurnal couplets are stacked into neap-spring (fortnightly) tidal cycles. Neap-spring cycles are arranged in thickening and thinning that record seasonal cycles driven by the annual monsoon. Total organic carbon (TOC) values are a proxy for annual climatic cycles. TOC contents are higher within intermonsoonal and lower within monsoonal components of annual cycles reflecting, respectively, lesser and greater dilution by terrestrial flux. / Master of Science

Late Ordovician (Cincinnatian) strata of the central Appalachians provide an opportunity to study the effects of both tectonics and eustasy within a foreland-basin setting. The Juniata Formation consists of red sandstones, siltstones, and shales that were deposited as part of an extensive siliciclastic basin-fill that resulted from the Taconic Orogeny. This study attempts to resolve some of the questions regarding tectonic and eustatic influences on sedimentation by (1) reconstructing the paleogeographic environment of the Juniata Formation and (2) examining the stratigraphic architecture of the Juniata Formation. A combination of both outcrop and subsurface data was analyzed. Seven facies were identified in this study, including: (1) "proto-vertisols", (2) red shale/mudstone, (3) siltstone/silty mudstone with interbedded sandstones, (4) quartz arenite and sublithic arenite, (5) argillaceous sandstone, (6) hummocky-bedded sandstones and siltstones, and (7) lithic sandstones and conglomerates. These facies are grouped into four facies associations (A–D), which are interpreted to be deposited from the inner shelf to the upper shoreface. Isopach and paleocurrent data suggest the shoreline was oriented NE–SW and detrital sediment was dispersed west and southwest across the basin. Tectonics controlled the 2nd-Order basin-fill pattern, and these patterns vary along the strike of the basin. Eustatic changes are expressed in two 3rd-Order sequences that were identified in the formation, and possibly in the 4th-Order (?) cycles of Facies Association A. The Ordovician–Silurian boundary is expressed as an unconformity throughout the study area, and along-strike variations in the structural setting of the basin were important in its development. / Master of Science

No description available.

No description available.

No description available.

No description available.

No description available.