E.H. Gierlowski-Kordesch¹
(1) Ohio University, Athens, OH

Abstract: Lack of extensive coals in the Upper Conemaugh: Dry climate or increase in sediment supply?

The Upper Conemaugh (Lower Stephanian) contains the lowest abundance of bituminous coal resources than any time previous in the Pennsylvanian of the Interior Coal Province and the Appalachian basin. This has been attributed to the driest climatic interval of the Pennsylvanian (until the onset of the uppermost Pennsylvanian/Permian time). Paleobotanical and stratigraphic/sedimentologic evidence for this are ambiguous.

Regional controlling parameters of stratigraphic sequences are tectonics (sediment supply, subsidence/accomodation), climate (sediment supply), and eustacy. Basinal to local controls on the accumulation and preservation of continental plant matter for coal production are primary organic productivity, location of groundwater table, dilution by mineral matter, and subsidence/accomodation. Some of the effects of these parameters or their combination may resemble “climate change” in the fossil record.

A test of the dry climate hypothesis can be performed through careful petrologic analysis of palustrine/lacustrine limestones because they can exhibit a set of characteristic sedimentary features for any climatic condition from dry to humid. Nonmarine carbonates from the uppermost Conemaugh and lowermost Monongahela of the northern Appalachian basin were compared using sedimentologic parameters; initial results show no difference in depositional regime between them. Deposition appears to have been under humid conditions punctuated by drier times. If a “dry” climate was not a factor, perhaps a reduction in subsidence rate with a concomitant increase in sediment supply is responsible.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana