STEPHAN, JEAN-FRANCOIS, Institut de GEodynamique UniversitE de Nice-Sophia Antipolis, Valbonne, France

ABSTRACT: Paleogeodynamic Evolution of the Northern South America Margin Through 13 Maps from Maastrichtian to Present

The paleogeodynamic history of the Northern South America Margin (NSAM) for the last 75 Ma is depicted through 13 maps.

Five major episodes can be distinguished:

1. In Maastrichtian and Paleocene times, the NSAM is still a passive margin including, from west to east, the northeast-trending Tinaco-Caucagua Promontory (TCP) and the Coast Range Realm (CRR);

2. From Lower to Upper Eocene the Villa de Cura-Tobago Cretaceous Arc obliquely collides with the margin, generating a northeast-trending foreland flysch basin (i.e., Matatere, Guarico, and Rio Guache flysch). By the end of Eocene, the TCP and CRR have been imbricated under the arc and thrusted southeastward, together with the flysch nappes, onto the upper margin. The allochthon front is stabilized roughly along an Acarigua-Caracas line;

3. Oligocene and lowermost Miocene times correspond to a drastic geometric and kinematic reorganization probably related to a strong slow-down of the Caribbean plate movement. Subsidence and transtension are dominant;

4. From late Lower Miocene to early Upper Miocene, the remnant central and eastern passive margin is tectonized due to the

fast eastward transpressive shift of the Caribbean plate;

5. In late Upper Miocene times, a second geodynamic reorganization occurs which gives rise to the present-day pattern where transpression is mostly active in Trinidad, Falcon, and the MErida Andes.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.