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Abstract: Chemostratigraphic Transect (Lagoon to Slope) Across a mid-Cretaceous Carbonate Platform, South-central Pyrenees, Spain: The Stratigraphic, Sedimentologic, and Paleoenvironmental Interpretation of a Platform Drowning Event.

DRZEWIECKI, PETER A., Exxon Exploration Company; J. ANTONIO SIMO, University of Wisconsin-Madison

Summary

The mid-Cretaceous carbonate strata of the south-central Pyrenees, Spain, record a drowning event at the Cenomanian Turonian (C/T) boundary, in which shallow, benthic sediments are abruptly overlain by pelagic sediments. This drowning event is associated with a positive d13C excursion, which has been used in this investigation to: (1) determine the timing of the, drowning event, (2) determine the cause of the drowning event, (3) estimate sedimentation rates during the event, (4) determine periods of condensed sedimentation, and (5) infer sedimentary processes.

Carbon isotope analysis of these strata have provided a direct temporal correlation between the drowning of the carbonate platform and a globally recognized oceanic anoxic event. Trace clement investigations of the same samples suggest that increased nutrient levels associated with the oceanic anoxic event resulted in the shift from benthic to pelagic deposition on the shelf and slope. The thickness of sediment affected by the carbon isotope excursion reveals that sedimentation rates were probably highest on the inner shelf and slope, and that the margin was swept clean of sediment during the platform drowning event. Furthermore, an analysis of the shape of the carbon excursion suggests a period of condensed sedimentation across the shelf immediately following the drowning event.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah