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Book Chapter

Biostratigraphy and Paleoecology of Calcareous Nannofossils in the Greenhorn Marine Cycle

By
David K. Watkins
David K. Watkins
Department of Geology
University of Nebraska
Lincoln, NE
68588
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Published:
January 01, 1985

Abstract

Preliminary biostratigraphic investigation of the Greenhorn Limestone at Pueblo, Colorado indicates that the Lincoln, Hartland, and lower Bridge Creek members are part of the Lithraphidites acutum calcareous nannofossil Zone. The middle and upper part of the Bridge Creek Member is assigned to the Quadrum gartneri Zone. Subdivision of these zones is difficult due to the scarcity of several biostratigraphically important taxa. Biohorizons based on secondary taxa do, however, offer promise for intrabasinal and intercontinental correlation.

Paleobiogeographic analysis using three time-slices across the basin suggests that fresh-water influx from the basin margins was an important factor in restricting nannofossil occurrence and diversity during the initial stages of the invasion of oceanic surface water masses into the basin (middle Cenomanian). By maximum transgression, however, the effects of fresh-water influx appear to be minimal in the eastern and central portions of the basin.

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SEPM Field Trip Guide

Fine-Grained Deposits and Biofacies of the Cretaceous Western Interior Seaway: Evidence of Cyclic Sedimentary Processes

Lisa M. Pratt
Lisa M. Pratt
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Erle G. Kauffman
Erle G. Kauffman
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Frederick B. Zelt
Frederick B. Zelt
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SEPM Society for Sedimentary Geology
Volume
4
ISBN electronic:
9781565762794
Publication date:
January 01, 1985

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