Print this pageTurbidite Systems in Brazil — Stratigraphy and Depositional Architecture
Clastic deposits produced by turbidity currents and related gravity flows are responsible for almost 90% of petroleum produced in Brazil. The study of Turbidite Systems from Itajaí, Paraná, Santos and Campos Basins, from outcrops and subsurface, early cambrian to recent deposits, formed in different tectonic settings and systems tracts, allowed a comprehensive characterization of these systems, depicting the main contrasts in terms of their depositional architecture, facies association, and petrophysics, a major goal of petroleum industry. In Brazilian basins these turbidites are commonly characterized by sandy deposits, originated from extremely catastrophic flows, able to transport huge volumes of pebbles, sand and mud, forming turbidite systems in oceans, lakes, either in shallow or deep waters. These currents are essentially linked to very dense hyperpycnal flows, triggered by fluvio-deltaic influx. In prolific Campos and Santos basins the late cretaceous and tertiary deep marine siliciclastic depositional systems are characterized by a direct connection of river channels to canyons, delivering their sedimentary load to the slope and basin regions, whose physiography is strongly controlled by salt and associated fault activities. Only Paraná Basin presents a clear glacio-eustatic control for turbidites. Two main zones with characteristic geometries and facies associations are commonly identified in these different turbidite systems: the transference zone and the depositional zone. Erosion and bypass dominate in the transference zone, usually characterized by submarine canyons and channels. The depositional area comprises lobes that constitute a major exploratory target because of the great volume of sand and the concentration of clean reservoirs. Turbidite lobes can be tabular or lenticular deposits, frequently associated with amalgamated channelized bodies. Other gravity-flow deposits originated from sediment instability, such as slides, slumping and debris flows are commonly associated with turbidites in the slope setting. In such regions, downslope resedimentation is common, and, as a consequence, previously continuous beds can be segmented, harming lateral continuity of porous layers. Tertiary and recent deep water turbidites from Campos Basin are commonly associated with bottom current deposits. These “contourites” are petroleum bearing reservoirs, commonly mistaken as turbidites.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil