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