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Despite the large number of models involving the genesis and sedimentary facies of deep-water sandstones, none of these models adequately explain the origin and evolution of the extremely clean, widespread (over 6000 km2), predominantly massive, thick (over 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 a 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 the subaqueous exposure of the shelf sediments to 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 commonly are scoured during al 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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