Abstract: Sea Level History Across the Northern South American Passive Margin: Eustatic vs. Tectonic Regulation

Erle G. Kauffman, Tomas Villamil

The northern South American passive margin (Colombia, Venezuela) was tectonically inactive during the Cretaceous, and comprises a natural laboratory for differentiating allocyclic (regional-global) from local autocyclic controls on sequence stratigraphy. This is only possible, however, by integrating high-resolution stratigraphic analysis with a refined system of chronology, allowing regional to global correlation within narrow time intervals. Attempts to test the effects of global sea level change in this region without this chronology are indefensible. High-resolution stratigraphic sections spanning the Albian-Campanian-Maastrichtian have been measured throughout the marine basins of Colombia and northeastern Venezuela, and calibrated to refined molluscan and planktonic foraminifer iozones, second- through fourth-order sequences/parasequences with well-dated transgressive and maximum flooding surfaces, and with regional event/cycle chronostratigraphy. Resolution of correlation averages <500,000 yr for the Cretaceous. Using graphic correlation, all second- and many third-order depositional sequences show similar sea level histories across the entire passive margin. Extending these correlations to the North American Interior basin and Gulf coastal plain, and to the Haq et al. global cycle chart, demonstrates eustatic control for numerous sequences, and allows identification of those influenced by regional/local tectonics. These observations, coupled with geochemical profiling which shows strong correlation to Corg accumulation to transgressive systems tracts, and otential reservoirs to lowstand systems tracts, enhances exploration modeling.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994