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The AAPG/Datapages Combined Publications Database

GCAGS Transactions

Abstract


Gulf Coast Association of Geological Societies Transactions
Vol. 25 (1975), Pages 263-278

Upper Cretaceous Calcareous Nannoplankton Zonation and Stage Boundaries

Charles C. Smith (1)

ABSTRACT

In 1969, Pavel Cepek and W.W. Hay presented a calcareous nannoplankton zonal scheme for the Upper Cretaceous. The zonation was based on samples from two isolated sections, one in Russell County Kansas, and the other from exposures along the Alabama River in Dallas and Wilcox Counties, Alabama. Unfortunately, the 12 nannoplankton zones were not related to either the standard or the reference sections of European stages or to provincial stages in common use within the Gulf Coastal province. Additionally, no mention was made of their relation to foraminiferal or megafossil zones in common usage. Stefan Gartner reproduced the zonal succession proposed by Cepek and Hay and indicated probable correlations of the biostratigraphic zones with the Upper Cretaceous stages of Europe. Considerable disagreement exists between the stage assignments as proposed by Gartner and the ages suggested for these same sections by other paleontologic data.

The present report consists of a comprehensive evaluation of the Cepek and Hay nannoplankton zonation, including an integration of the nannofossil zones with those based on other fossil groups, and discusses their age assignments within the standard European framework. The zonal succession proposed by Cepek and Hay stratigraphically terminates in Russell County, Kansas, in strata of early middle Turonian Age; it is resumed in Dallas County, Alabama, in strata assignable to the middle early Campanian. In Texas, this missing interval (upper Turonian-lowermost Campanian) is represented by strata assignable to the upper part of the Eagle Ford Shale and almost the entire Austin Chalk. The assignment by Cepek and Hay of samples studied by both Stefan Gartner and David Bukry from the Eagle Ford and Austin Formations of Texas to their Upper Cretaceous nannoplankton zonal sequence must therefore be regarded with considerable uncertainty.


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