--> --> Abstract: Origin and Distribution of Organic Matter in Mudstones of the Lower Cretaceous Cloverly Formation of Wyoming, by W. S. Elliott, Jr.; #90925 (1999)

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ELLIOTT, WILLIAM S., JR., Indiana University, Department of Geological Sciences, Bloomington, IN

Abstract: Origin and Distribution of Organic Matter in Mudstones of the Lower Cretaceous Cloverly Formation of Wyoming

The Cloverly Formation consists of ~60 m of coarse and fine-grained siliciclastic rocks with subordinate amounts of limestone, which were deposited in fluvio-lacustrine environments during the incipient development of the Western Interior foreland basin in the Early Cretaceous. Preliminary results of total organic carbon analysis of mudstones collected along a transect perpendicular to the axis of the foreland basin reveal an increase in organic content away from the fold-thrust belt. A number of factors could have contributed to this including, but not limited to, regional changes in climate associated with an orographic effect and diminishing influence of a tectonic control on sedimentation away from the basin margin. The purpose of this research is to investigate the vertical and lateral distribution of organic matter in the mudstones in order to verify the trend observed in a reconnaissance study across the foreland basin and to evaluate the factors which may have contributed to this trend.

Samples of mudstone will be collected from several localities in central Wyoming for geochemical analysis, and stratigraphic sections will be measured in the field using accepted techniques. Field and petrographic study of paleosols in the sequence will supplement geochemical analysis in order to provide insight into sedimentological and diagenetic controls of organic matter distribution in mudstones. In addition, carbon isotopes and biomarker analysis will be used to constrain the origin of the organic matter.

This study will be the first of its kind to examine the regional distribution of terrestrial organic matter in a foreland basin. 

AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid