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Causes of Pennsylvanian Cyclicity in the Appalachian Basin

By
Alan C. Donaldson
Alan C. Donaldson
Geology and Geography Department, West Virginia University, Morgantown, WV 26506
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Published:
January 01, 1994

Abstract

Three types of cycles are recognized for the Pennsylvanian rocks of the Appalachian basin: 1) autocycles (river avulsion and shifts in supply); 2) sub-regional allocycles (tectonism within the basin or uplift of parts of the orogenic belt; and 3) regional and eustatic allocycles (regional tectonism or eustasy). Autocycles occur within minor allocycles and are interpreted as sediment-supply shifts accompanying river avulsions within relatively fixed-drainage basins. Minor allocycles of coal measures commonly are 18 to 30 meters in thickness and contain extensive paleosols, coal, marine and/or freshwater limestone beds. Current estimates of allocycle durations vary greatly depending on the time scale used. Minor allocycles probably are glacio-eustatic and shoreline T-R shifts range from 32 to >800 km. Intermediate allocycles consist of several minor allocycles either in progradational, aggradational or retrogradational sets with relatively more transgressed units serving as the boundary units and are 90 to 115 m thick. Major allocycles are bounded by extensive transgressive units, are about 300 m thick, and approximate the Lower, Middle, and Upper Series of Pennsylvanian. These major allocycles are subregional, reflect basin tectonism shown by shifts in the seaway during the Pennsylvanian, and do not correlate with worldwide sea level curves, suggesting the basin's response to thrust-sheet loading during the Alleghanian orogeny. Cycles in paleoclimate were significant in influencing the lithic response within the allocycles (Cecil, 1990).

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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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