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Upper Devonian turbidite sequence, central and southern Appalachian basin: Contrasts with submarine fan deposits

By
Paul D. Lundegard
Paul D. Lundegard
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Neil D. Samuels
Neil D. Samuels
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Wayne A. Pryor
Wayne A. Pryor
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Published:
January 01, 1985

The Upper Devonian turbidite sequence in the central and southern Appalachian basin reaches 1400 m in thickness and consists of siltstone turbidites interbedded with mudstone, claystone, and shale. Facies and paleocurrent analyses, based on approximately 6100 m of detailed measured section at 35 localities and 700 measurements of directional structures, indicate major differences between the Upper Devonian sequence and submarine fan and ancient flysch deposits.

Compared to flysch and submarine fan deposits, the Upper Devonian turbidites are finer grained and thinner bedded, reflecting the smaller size and lower maximum velocity of the turbidity currents. The stratigraphic transition from turbidites to overlying deltaic rocks shows a different succession from that expected for proximal deposits of submarine fans associated with fan channels and canyons. This transition in the Upper Devonian deposits is gradual and marked by upward-thickening and -coarsening sequences of evenly-bedded turbidites and lenticular beds of crossbedded sandstone. Higher energy mass flow deposits such as debris flows, massive and pebbly sandstone, and conglomerates are notably absent.

Paleocurrent data are remarkably uniform, both areally and vertically through the stratigraphic section. They indicate a uniform dispersal pattern, transverse to the basin axis, for nearly 600 km along depositional strike. This suggests turbidity currents had multiple point sources along the basin margin and that the paleoslope had little topographic relief on it. Dip-oriented, short-lived turbidite lobes were built and abandoned as the source of turbidity currents shifted. Migrating delta distributaries, instead of fixed feeder channels, probably supplied sediment to the slope.

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GSA Special Papers

The Catskill Delta

Donald L. Woodrow
Donald L. Woodrow
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William D. Sevon
William D. Sevon
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Geological Society of America
Volume
201
ISBN print:
9780813722016
Publication date:
January 01, 1985

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