Tectonic Influence on Depositional Sequence Development, Columbus Basin, Eastern Offshore Trinidad and Tobago

L. J. Wood

The Columbus basin is located off the eastern coast of Trinidad and the northeastern coast of Venezuela, along the margins of the converging Caribbean and Atlantic plates. Post-Miocene tectonics have resulted in transpressional structures oriented NE-SW and tensional faults oriented NW-SE Sea level has undergone high frequency fluctuations throughout the Plio-Pleistocene. The Orinoco River, which drains the Andean Highlands, has fed enormous quantities of sediment into the basin since the late Miocene (>30,000^prime).

Several observations from an Integrated Depositional Sequence Analysis of the Columbus Basin are applicable to basins in similar settings, such as the Nile and Niger deltas. These include the following:

1. Limited shelf development, associated with limited shelf subsidence, may be an indicator of shelf bypass and slope canyon development.

2. Limited basin-floor and slope fan development may be an indicator of shelf aggradation, associated with subsidence at the shelf-break.

3. Extensional and compressional structures focus feeder systems and localize accommodation space.

4. Drill deeper; the basal deepening of a regressive package may be in response to localized tectonics and indicate only temporary loss of good reservoir.

5. Limited transgressive systems tract development is associated with limited transgressive-time accommodation space, and creates better reservoir-seal relationships.

6. Interactively, integrating data sets provides the best chance for descerning: sequence relationships across the basin, local versus basinwide chronologic events, sediment bypass versus aggradation zones, reservoir trends and TRUE age of the section.

7. Interpreting the rock record in terms of accommodation space and sediment supply provides a much more practical methodology in tectonically active areas than traditional sequence stratigraphic techniques using the classic eustatic-driven model.

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