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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 55 (1971)

Issue: 8. (August)

First Page: 1336

Last Page: 1344

Title: Late Cenozoic Imbricate Thrusting in Venezuelan Andes: GEOLOGICAL NOTES

Author(s): Gregor N. Deratmiroff (2)


Analysis of reconnaissance and detailed maps in western Venezuela indicates that the present Venezuelan Andes underwent shear deformation throughout most of the Tertiary. This deformation is exemplified by dextral wrenching along the Bocono fault zone, the structural setting for which was probably established at the close of the Paleozoic. Major compressional uplift began throughout the Andes during late Miocene time. The uplift is characterized by ubiquitous marginal imbricate thrust faults.

A stress direction of approximately 80-90° probably was responsible for the Bocono wrench fault and associated merging thrusts on the southeastern side of the fault. It is possible that the wrench character of the Bocono was responsible for the mergent lineaments on the northwestern side. A reorientation of the stress field must have taken place at the close of the Miocene and possibly during the Pliocene so that a compressive stress of approximately 120° became operative as is suggested by the general strike of the fault lines of individual imbricate sheets, ranging between 30 and 40°. The compressive stresses resulted in a mushroomlike deformation with marginal imbricate thrusting. There appears to be a close correlation with the El Pilar fault zone's dextral (80-90 76;) movement and the resulting Andean deformational stresses.

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