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|Title:||Sedimentation in Karst Drainage Basins Along the Allegheny Escarpment in Southeastern West Virginia, U.S.A.|
|Authors:||Wolfe, Thomas E.|
|Advisor:||Ford, D. C.|
|Abstract:||<p>A review of the literature shows a lack of information on stream transported and deposited cave sediments. Where such studies have been made, sedimentary structures have been overlooked or misinterpreted. A study of sedimentary deposits in Appalachian caves by the author indicates that a large quantity (over 75%) of the deposits found in caves of that area is derived from overlying or adjacent clastic rock and is deposited by streams at a time not contemporaneous with the origin of the cave passages. This contradicts the views of some geomorphologists. Additional evidence from scallop measurements on the floor, ceiling and walls of passages indicates velocities of different magnitude and directions from those which are responsible for the transport of a coarse bedload common to most passages. Scallops and passage profiles also indicate that fills may shield the cave floor from further solutional activity once a thick deposit of clastic material accumulates. Such deposits protect and preserve former large-scale scallops produced during passage solution. This allows for comparisons between scallop velocities and velocities which transported the sediments. Ancient deposits at higher levels in the caves indicate that the conditions of passage solution and deposition of fills have remained relatively constant during approximately the last 200,000 years. However, some caves show evidence for massive, single depositional events with little sorting or rounding. This suggests periglacial activity on the Greenbrier karst at elevations around 2,500 feet; an elevation considerably lower than previously described sites in the area.</p> <p>A model for the development of surface and subsurface drainage and sediments across the Greenbrier limestone is developed. This is based upon the changes in the tributary karst basins progressing in a downstream direction along the Greenbrier River. Karst "sieve-type" deposition, the accumulation of bedload at the upper clastic/carbonate contact, is an important feature of this model. Periglacial debris, now inactive, which accumulated during colder periods along the escarpment face is reworked by surface streams. This provides a source of coarse bedload for the sieve deposits. Fines are winnowed out and carried into the caves or accumulate in terraces below the karst risings in the lower basins.</p> <p>The use of kaolinite 3.58Å/illite 10.0Å ratios from clay mineral samples shows weathering variations which are useful in provenance determination if considered along with data on milky quartz pebbles and identifiable lithologies. Dating by Thompson (1973) from travertine deposits directly on top of, or interbedded with, fluvial sediments helped to establish relative and absolute dating of the deposits. In appears that travertine deposition is most active during the warmer inter-glacial periods. Although sediment deposition occurs throughout the warm and colder periods, it appears that massive single depositional events occurred during periglacial periods when travertine deposition was minimal.</p>|
|Appears in Collections:||Open Access Dissertations and Theses|
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