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Lithostratigraphy and Depositional Environments of the Ancell Group in Central Illinois: A Middle Ordovician Carbonate-Siliciclastic Transition

By
T. H. Shaw
T. H. Shaw
1
Department of Geology, Queens College, CUNY, Flushing, NY 11367
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B. C. Schreiber
B. C. Schreiber
2
Lamont-Doherty Geological Observatory, Columbia University, New York, NY 10964
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Published:
January 01, 1991

Abstract

The Middle Ordovician Ancell Group is the basal transgressive deposit of the Tippecanoe sequence in the Illinois Basin region. The mixed carbonate and siliciclastic composition of its constituent lithologies is a reflection of depositional conditions related to regional tectonism, the lithic character and nature of erosional processes in adjacent source areas, and changes in relative sea level and paleoclimate. Differentiation of lithofacies, their inferred depositional environments, and their vertical and lateral relationships provide a basis for identification of three major depositional cycles. Each cycle is made up of small-scale, shallowing-upward sequences that tend to reflect increasingly subtidal conditions upsection. The cycles are regionally correlative; consequently, they provide a basis for subdividing the Ancell Group into genetic units and for interpreting regional sedimentological, paleoclimatic, and tectonic processes during early-Middle Ordovician time in the Illinois Basin region.

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Contents

SEPM Core Workshop Notes

Mixed Carbonate-Siliciclastic Sequences

Anthony J. Lomando
Anthony J. Lomando
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Paul M. Harris
Paul M. Harris
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SEPM Society for Sedimentary Geology
Volume
15
ISBN electronic:
9781565762695
Publication date:
January 01, 1991

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