Nilo Chagas de Azambuja Filho¹, Ciro Jorge Appi¹, Andre Adriano Bender¹, Henrique Luiz de B. Penteado¹
(1) PETROBRAS, Rio de Janeiro, Brazil

Abstract: Freshwater outflow as a triggering mechanism for slope failure and turbidites in the Campos Basin, Brazil

An integrated stratigraphic approach using bathymetric maps from sonar surveys and fluid flow modeling in the Campos Basin has allowed a suggestion for a high frequency triggering mechanism for slope failure and consequent gravity flows and turbidite processes. On the modern upper slope of the Campos basin, offshore Brazil, there are several canyons and mass waist slope features, some of them were linked in a recent past with the shelf and others were not. Why such features are distributed along the slope with different density and magnitude is always hard to explain. A possible explanation came from the observations of several realizations of numerical modeling of fresh water influx associated with the lowering in the sea level trying to explain biodegradation processes. The numerical modeling suggests an outflow of freshwater in the slope. This would create an instability of the slope favoring slumps in these outflows. The position of these intraslope freshwater springs would be controlled by ancient incised valleys and flooding surfaces. The former would favor preferential pathways with better permeabilities and the latter would confine the freshwater to specific horizons and consequently positions on the slope. Additional studies and geophysical surveys will be carried out to collect enough data for a proper characterization of such mechanism and to better evaluate its implications in ancient turbidites and associated gravity driven deposits.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana