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Climate Controls on Cyclic Sedimentation: Climatostratigraphy

By
C. Blaine Cecil
C. Blaine Cecil
United States Geological Survey, Reston, VA 22092
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N. Terence Edgar
N. Terence Edgar
United States Geological Survey, Reston, VA 22092
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Thomas S. Ahlbrandt
Thomas S. Ahlbrandt
United States Geological Survey, Reston, VA 22092
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Published:
January 01, 1994

Abstract

Cyclic sedimentation is generally attributed to tectonic and (or) eustatic controls. The stratigraphy of chemical and siliciclastic sedimentary rocks cannot, however, be explained on the basis of these physical processes alone. As an example, the Pennsylvanian System of the United States contains transgressive-regressive cycles (cyclothems) that appear to be eustatically driven; also, basins were tectonically active as subsidence was necessary to provide accommodation space. On a basin scale, however, stratigraphic repetition of chemical rocks (coal beds, paleosols, and marine and nonmarine limestone) and siliciclastic rocks is indicative of paleoclimatic cycles as well as baselevel change induced by tectonics and (or) eustasy. Such climate cycles (changes in rainfall patterns) are recorded in stratigraphic sequences by 1) changes in paleosediment flux, 2) laterally extensive paleosols, whose characteristics range from modern aridisols (arid-climate soils) to vertisols (seasonal-climate soils) to oxisols (everwet climate soils), and 3) paleobotanical changes that have long been attributed to changes in paleoclimate. On a continental scale, zonalcirculation paleoclimates are also recorded in addition to paleoclimate cycles.

The paleogeography of North America during the Pennsylvanian was such that the Appalachian basin was equatorial relative to the midcontinent and western United States. The resulting paleoclimate gradient from the Appalachian basin to the western United States (wetter to drier, respectively) is indicated by the development of coal beds in the Appalachian basin while evaporites were being deposited in the Paradox basin contemporaneously with alluvial fans and eolianites in the Rocky Mountain region. Paleoclimate, therefore, appears to be on a par with tectonic and eustatic changes as a primary control on sedimentation and stratigraphy. Thus, sedimentary sequences that exhibit the effects of climate as a primary control on sedimentation may be appropriately classified as climatostratigraphic units.

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Contents

SEPM Concepts in Sedimentology and Paleontology

Tectonic and Eustatic Controls on Sedimentary Cycles

John M. Dennison
John M. Dennison
University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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Frank R. Ettensohn
Frank R. Ettensohn
University of Kentucky, Lexington, Kentucky
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SEPM Society for Sedimentary Geology
Volume
4
ISBN electronic:
9781565762275
Publication date:
January 01, 1994

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