Laszlo Benkovics¹, James Helwig²

(1) PDVSA INTEVEP, N/A, Venezuela
(2) Subsurface Consultants, Houston, TX

ABSTRACT: Extension and Inversion of the Barúa-Motatán Area, Eastern Margin of Maracaibo Basin, Zulia Oriental, Northern Venezuelan Andes

The Barúa-Motatán area is located east of Lake Maracaibo and extends into the flank of the Serranía Trujillo, forming the present-day topographic and tectonic transition from the Maracaibo Basin to the Andean ranges. Maps of subsurface structure, made from analysis of 3D seismic and well data, are combined with surface geology and the regional tectono-stratigraphic setting to interpret the deformation geometry and sequence. Cretaceous-Paleocene platformal subsidence was disturbed by normal (and strike-slip?) basement faults. An Early to Middle Eocene foreland basin developed and accumulated a thick Misoa clastic wedge that dipped north, disturbed by minor normal faulting. During the late Middle Eocene, the foreland basin margin rotated northeastward, accommodating the Paují depositional wedge. The north-trending Motatán fault acted as a normal growth structure with up to 2000 feet of throw. Initial inversion then formed low-relief, southwest-vergent folds and faults that are preserved as interference folds in high-relief younger synclines. Finally, during late Paují time, the Motatán and Barua faults were inverted, forming large faulted anticlines. Noteworthy is the simultaneous and unusual imbricated style of inversion on the linked east-trending Tomoporo fault. A younger phase of inversion and erosion followed in the Oligocene-Early Miocene. Then the basin tilted south to accommodate the huge clastic wedge trapped in the new foreland of the Neogene Venezuelan Andes, producing the south plunge of the Barúa and Motatán structures. Neotectonic folding which strikes N-S is located east of the old structural trend, and is forming new traps on a backthrust system of the Motatán structure.

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