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Stratigraphic Architecture of a Prograding Shelf-Margin Delta System in Outcrop: Sobrarbe FM., Ainsa Basin, Spain

Amy C. Moss
Chevron Center of Research Excellence Department of Geology and Geologic Engineering Colorado School of Mines Golden CO 80401; [email protected]

The Sobrarbe Formation, Ainsa Basin, Spain is continuously exposed from fluvial-deltaic to deepwater outcrops in multiple, prograding, condensed section bound cycles. Because of the extent of exposure, the physiographic profile is observable and the position of the delta apparent at the physiographic break of shelf. In the best exposed condensed section bound cycle, highly continuous bypass surfaces in the delta appear to correlate to the upper slope and contribute to deepwater channels. This outcrop allows the testing of multiple hypothesis including deltaic controls on deepwater sedimentation and criteria for the identification of shelf-margin deltas when the physiographic profile is not discernable.

Initial fieldwork focused on regional mapping of condensed section bound depositional cycles and detailed measured sections in order to correlate in the depositional dip direction from the shelf to upper slope, strike direction through the shelf-margin delta, and strike direction through the fluvial system. Initial results support the hypothesis of progradational architecture within the condensed section bound cycles and the continuity of bypass surfaces to deepwater channels.

Final fieldwork will address detailed sedimentologic and stratigraphic description of depositional elements: deltaic mouth bars, deepwater channels, and fluvial channel belts. Identifying the lateral and vertical association of these elements will constrain process controls on bypass surfaces within the shelf-margin delta and, therefore, controls on the formation of deepwater channels.

AAPG Search and Discovery Article #90083 © 2008 AAPG Foundation Grants in Aid