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Abstract: Eocene Sequence Stratigraphy and Paleoenvironments, Maracaibo Basin, Venezuela

Elias Zambrano, Luis Melendiiez, Santosh Ghosh, Pieter J. Pestman, Maria A. Lorente

A regional study based on seismic and well data from the Maracaibo Basin permitted the subdivision of the Eocene into six tectonically enhanced sequences, bounded by SB54, SB51 .5, SB49.5, SB44, SB42.5, SB39.5 and SB36. In each sequence, transgressive and highstand deposits have been distinguished. Lowstand deposits (prograding wedge, turbidites) have been recognized mainly in the foredeep in the northeastern part of the basin. Transgressive deposits are developed best in the southwest and center of the basin, where fluvial, estuarine and alluvial-coastal plain environments dominated. Highstand deposits, formed in fluviodeltaic to shallow marine settings, dominate the sequences in the north and east of the basin.

Most Eocene sediments in the basin come from the south and southwest, with secondary influx from the northwest and the nappes in the northeast.

Overall, a second-order transgression occurred from 54 Ma to approximately 49.5 Ma, followed by a regression related to SB44 (= base "B-6"). The remainder of the Eocene is transgressive, with marked marine flooding around 42.5-41.5 Ma. This resulted in the replacement of the sand-dominated Misoa Formation by shales of the Pauji Formation, which is time-transgressive.

Tectonics clearly controlled the distribution of positive and low areas. The Eocene depocenter, a product of the Lara nappes, was located in eastern Zulia where a marked thickening of sequence occurs. Onlaps indicate the persistence of highs (Merida and Palmar), whereas truncations indicate erosion (SB44, Post-Eocene Unconformity, etc.). This study helps focus exploration effort by a better understanding of a mature basin.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela