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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Shelf-Fed Turbidite System
Model
and its Application to the Oligocene Deposits
of the Campos Basin, Brazil


By
PETROBRAS AMERICA, Inc.
Despite the large number of models involving
the genesis and sedimentary facies of
deep-water sandstones, none of these models
adequately explains the origin and evolution
of the extremely clean, widespread
(more than 6000 km2), predominantly massive,
thick (more than 150 m), blanket-like
sandstones deposited in the deep-water
environment of the Campos Basin during
the Oligocene. Consequently, to explain
this sandstone, I propose a shelf-fed turbidite
system model
, which is strongly
based on the Campos Basin data set.
The basic framework necessary for the development of a shelf-fed turbidite system includes: (1) deposition of a large volume of clastics during the buildup of the shelf-sand-rich unit, which later constitutes the main source of sediment for the system, (2) localized tectonic pulses that modify the outer-shelf declivity and trigger mass-flows, and (3) a relative fall of sea level, which causes exposure of the shelf sediments and reworking in a shallow, high-energy marine environment. These three basic elements are equally important for shelf-fed turbidite system development, but relative sea-level position controls the development of the progradational, aggradational, and retrogradational depositional phases within the system. Submarine canyons are commonly scoured during all three phases on the outer shelf and lower slope environments.
The shelf-fed turbidite system model
may
apply to other sedimentary basins, principally
to those of the Atlantic-continental
margins that have a thick evaporite sublayer.
Halokinesis can provide the necessary
room for the shelf sedimentary-unit
buildup, the tectonic pulses that trigger the
flows, and even localized relative sea-level
oscillations that can accelerate or abort
any one of the depositional phases of the
system.
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