--> ABSTRACT: Recognition of High-Frequency Sequences Related to a Miocene Forebulge Development, Eastern Maracaibo Composite Foreland Basin, Western Venezuela, by Manuel Toro Milano and Ronald J. Steel; #90906(2001)

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Manuel Toro Milano1, Ronald J. Steel2

(1) PDVSA Intevep, Caracas, Venezuela
(2) University of Wyoming, Laramie, WY

ABSTRACT: Recognition of high-frequency sequences related to a Miocene forebulge development, Eastern Maracaibo composite foreland basin, Western Venezuela

ABSTRACT

The Maracaibo Basin in northwestern Venezuela is a composite foreland basin characterized by foredeeps both in the south and west, as well as piggy-back basins and half grabens in the east. The western foredeep is part of a retro-foreland basin tectonically associated with the Sierra de Perijá uplift that occurred in Oligocene-Miocene times. The La Rosa Formation and the lower part of the Lagunillas Formation (lower-middle Miocene) show evidence of having been deposited in the distal portion of this retro-foreland basin. A range of regressive deltaic/strandplain, and transgressive barrier bar/estuarine environments were identified in the La Rosa and Lagunillas cores. Core-log calibrations and the identification of stacking patterns and key stratigraphic surfaces allowed two types of high-frequency stratigraphic sequences to be recognized. Most sequences were of a simple transgressive-regressive type, whereas some additionally had a lowstand segment, implying a relative sea level fall. The high-frequency sequences, each one of duration less than 0.5 my are believed to have been controlled by high subsidence rates. The basinward and landward stepping of high-frequency sequences are interpreted in terms of milder and strong advance of the western thrust-belt wedge that caused the variable migration of a forebulge to the east.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado