Print this pageAbstract: Late Precambrian Sedimentation in Belt and Uinta Aulacogens--Initial Deposits of Cordilleran Geosyncline
The Belt and Uinta embayments are two of at least four epicratonic reentrants in the main north-south trend of the late Proterozoic Belt miogeocline. The other two reentrants are the Apache embayment in northern Arizona and the Kimberley embayment in southern British Columbia.
Both the Belt and Uinta embayments are graben-like basins. Sedimentary facies relations suggest that the basins were asymmetrical and dipped westward. Both basins have thick nonmarine clastic wedges on one side indicating large-scale vertical movement on the boundary faults. Deltaic sequences also filled the basins by progradation along the length of the trough toward the west.
Stratigraphic sequence, tectonic features, and descriptive morphology indicate that both the Belt and Uinta embayments are aulacogens. Many characteristics common to documented aulacogens are present in the Belt and Uinta basins; however, these basins lack associated alkaline volcanic rocks common in some aulacogens.
Deposits of aulacogens form the oldest assemblage of sedimentary formations of the platform and coincide with the initial phase of platform development. The Belt miogeocline cuts across earlier Precambrian trends. Analysis of data in this study indicates that rifting occurred prior to deposition of Belt rocks and may have resulted from the linking of rift arms from as many as four thermal domes or hot spots. The rocks of the Belt and Uinta aulacogens are thus among the initial deposits of the Cordilleran geosyncline.
AAPG Search and Discovery Article #90972©1976 AAPG-SEPM Annual Convention and Exhibition, New Orleans, LA