Late Pennsylvanian Paleoclimate Cycles, Sediment Flux, and Organic Productivity in the Appalachian Basin

CECIL, C. BLAINE, and FRANK T. DULONG, U.S. Geological Survey, Reston, VA, and NICK FEDORKO, West Virginia Geologic and Economic Survey, Morgantown, WV

Late Pennsylvanian paleoclimate cycles were a major factor in controlling sedimentary cycles in the Appalachian basin. Allocyclic effects of climate change, in addition to tectonic and (or) eustatic processes, had a pronounced effect on chemical (including organic) and siliciclastic-sediment flux.

The effects of climate cycles are recorded stratigraphically by geochemical signatures such as paleosols, coal beds, and nonmarine limestones. Laterally extensive coal beds derived from topogenous peat indicate periods of high terrestrial organic productivity. The structure, chemistry, and mineralogy of coeval upland paleosols appear to be the result of leaching through chemical weathering. Topogenous paleopeat formation and the characteristics of coeval upland paleosols are consistent with a relatively wet paleoclimatic regime.

The driest parts of climate cycles are recorded by nonmarine limestone beds that can be traced laterally into highly calcareous paleosols that approach aridosols in their structure, chemistry, and mineralogy. Brecciation and subareal-exposure crusts within limestone beds suggest a fluctuating water table. The paucity of terrestrial organic matter, nonmarine limestone with multiple subareal-exposure features, and the nature of upland paleosols indicate relatively dry climatic conditions.

Paleoclimate change, therefore, appears to have been a significant control on sediment flux and organic productivity during the Late Pennsylvanian in the Appalachian basin. Cyclic stratigraphy appears to be the result of climate cycles as well as of changes in base level.

AAPG Search and Discovery Article #91005 © 1991 Eastern Section Meeting, Pittsburgh, Pennsylvania, September 8-10, 1991 (2009)