Characteristics
of Laterally Confined Sheet Sands. Quebrada Las Lajas,
Kertznus, Vanessa1, Ben
Kneller1, Mason Dykstra2 (1) University of Aberdeen,
Aberdeen, United Kingdom (2) University of California, Santa Barbara, CA
Deepwater submarine environments are
commonly characterized by a complex seafloor morphology comprising a mosaic of
small depositional basins (minibasins) several kilometers across. Turbidity
currents that run into these areas can be sufficiently large to spread across
the entire basin floor. The degree of confinement experienced by flows depends
on the height and volume of the flow compared to the confining seafloor
topography, which my completely trap flows or only partially confine them.
Variability in petroleum reservoirs is
typically not sufficiently described in fine scale. Seismic data provides
information over a large area, but with limited resolution, whereas log and
core data provide detailed measurements, but only over a limited area. Given
these limitations the objectives of this study are to 1) document the influence
of lateral confining slopes on the sedimentary characteristics of individual
turbidite beds, and 2) establish whether turbidite sheet sands present lateral
and longitudinal changes in bed thickness, sedimentary structures, and
grain-size, related to the depositional processes involved in their
emplacement, and the interaction of turbidity currents with the confining
topography.
The Quebrada Las Lajas outcrops provide a
degree of three-dimensionality, which allows the spatial characterization of
layered and amalgamated sheet-like turbidite deposits confined laterally within
a paleofjord. The spatial variations of this ponded fill succession can be used
as partial analogs to intraslope basins formed by growth faulting, shale-based
detachment faults, salt-withdrawal mini-basins, or salt-based detachment
faults, such as those in the Gulf of Mexico, Nigeria, Angola, and others.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California