Abstract: The Passive Margin of Northeastern Venezuela and Implications for Cretaceous Eustasy

Johan P. Erikson

Northeastern Venezuelans Serrania del Interior (SdI) exposes a Valanginian-middle Eocene passive-margin sedimentary section that provides a relatively stable framework for assessing relative sea level change during a non-glacial era. The exposed Valanginian-Aptian strata are comprised of dominantly siliciclastic shelf facies. A retrograding platform of mixed carbonate-siliciclastic facies was developed in Aptian-Albian time. Albian through Eocene deposits generally are deep-shelf pelagic (source rock) or submarine fan accumulations.

Interpretation of the relative sea level history of this region and its possible eustatic component required identification and distinction of regional versus strictly local intervals and surfaces. Most sequences boundaries occupy intervals of strata up to several meters thick rather than being single surfaces. Paleogeographic reconstructions based on many measured sections from a 80 × 150 km region of the SdI reveal that depositional systems generally were highly variable on the scale of tens of kilometers. Many localized sequences were the consequence of autocyclic processes and carbonate productivity changes. Sediment-supply variations induced by Hauterivian, Aptian-Albian, and Eocene tectonism in/near the SdI probably are reflected in the stratigraphy, but deposition during o her time periods probably was controlled primarily by eustasy. Nevertheless, fewer than 10 regionally extensive sequence boundaries form a subset of all sequence boundaries identified in numerous sections. The sequence boundaries are distributed through about 90 My of exposed strata and are more widely spaced temporally than is usually concluded from more tectonically active locations.

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