Print this pageUppermost Jurassic and Cretaceous 2nd Order Sequence Boundaries in Brazilian Marginal Basins: Correlations with some Andean Basins and Implications
PEREIRA, MARCIO J.
Based on seismic and wells data throughout the uppermost Jurassic and Cretaceous sections of the Brazilian marginal basins and three Andean basins (Neuquen, Western/Eastern Peru and Ecuador), twelve major 2nd order depositional sequence boundaries were identified in either siliciclastic and carbonate sections. Biostratigraphic data, few radiometric dating in volcanic flows, and the conspicuous recurrence of the sequence boundaries and maximum transgressions suggest a quasi-synchronism among the boundaries, been them either in rift or post rift stages, or either in continental or marine sections.
Based on this regional study in the South American Plate, the important question "tectonics versus eustasy" comes up for discussion again. The sequence boundaries seem to have age and time span controlled by major global eustatic falls, but in phase with relatively short episodes of increasing compression (e.g., ending of a widespread rifting phase, subduction blocking or collision) in several areas of the world. The enhanced intraplate stresses resulting from these episodes had remarkable effects in the origin of the studied sequence boundaries. Renewed deformations in major crustal discontinuities and arches in the South American Plate took place strongly affecting the source areas, borders and depocenters of its marginal and interior basins. In Brazilian marginal basins, predictive regional trends of systems tract and lithofacies (type and volume) are remarkable when we consider the tectonics as the main control on erosion and resedimentation processes.