Punctuated Equilibria Plate Tectonics and Exploration Strategies: Examples from Australia and South America

Malcolm I. Ross, Vitor Abreu, and Peter R. Vail

Understanding the interplay between plate tectonic events, subsidence, flexure, and depositional systems is critical to successful exploration, play concept development, and maturation modelling in frontier exploration. Conventional exploration techniques (seismic/well log mapping, geohistory, geophysical, and forward modelling) are used to quantitatively describe the stratigraphic packages observed in basins, but the driving force creating and destroying the packages has typically been qualitatively described as subsidence/uplift events. In order to predict depositional systems patterns, the driving force of these events must be more quantitatively understood.

We observe that the tectonic history of plates is characterized by long periods of fairly constant motion interrupted by short events of reorganization ("punctuated equilibria"). We also observe that these events are usually regional in nature and cause changes in regional subsidence patterns. Furthermore, these changes cause changes in major depositional system locations and characteristics. Analysis of the plate tectonic history of motion predicts times of quiescence and times of rapid change in basin stratigraphy and therefore produce more effective exploration strategies.

We have performed integrated sequence stratigraphic analysis in three basins (Barrow/Dampier, Otway, Santos-Pelotas), on two widely displaced continents (Australia and South America), spanning the Cretaceous Period. Although the tectonic histories are different, each basin responds to its tectonic history in a similar fashion: slow (or negative) subsidence diminishes volume and recognizability of transgressive and highstand systems tract and increases the volume and recognizability of lowstand systems tracts. The alternate case (rapid subsidence) produces the alternate result.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California