Published 1995 as part of Memoir 62
Copyright © 1995 The American Association of Petroleum Geologists.   All Rights Reserved.

Three main phases occurred in the Jurassic-Eocene geologic history of Lake Maracaibo: (1) Jurassic rifting related to separation of the North and South American continents; (2) Early-Late Cretaceous passive margin subsidence following rifting and creation of oceanic crust between North and South America; and (3) Paleocene-Eocene foreland basin subsidence following the oblique collision of a Pacific-derived Caribbean plate with the South American passive margin. The distribution of Jurassic red beds and volcanic rocks in deep wells beneath the Maracaibo basin suggest that they were deposited in north-northeast trending rift basins separated by horst blocks of Paleozoic metasedimentary rocks. This structural grain was subsequently reactivated during Cenozoic collisional and strike-slip deformation. Lithology and isopach patterns suggest that Barremian-Santonian shallow marine carbonates in the Maracaibo basin formed in a passive margin setting above Precambrian and Paleozoic crust thinned during the Jurassic rifting event. Isopach patterns show that the northwest-trending Mérida arch was a positive feature in Barremian-Santonian time. The tectonic origin of the Mérida arch and similar arches in Colombia and Ecuador is unclear, but they may be related to reactivation of underlying Precambrian or Paleozoic structural grains during passive margin subsidence.

Isopach maps show that the Paleocene-Eocene depocenter of the Maracaibo basin was an asymmetric, elongate trough containing up to 7 km of Paleocene-Eocene clastic rocks. The main Paleocene-Eocene depocenter is flanked on its north and northeast margin by a partially exposed south-southwest verging fold and thrust belt. Isopach mapping suggests a northwest-southeast migration of the depocenter from Paleocene to middle Eocene time. Previous work on sandstone composition, paleocurrent measurements, and seismic reflections of prograding clinoforms all support the idea that the basin formed as a foreland depression in front of a west-southwest verging fold and thrust belt along the eastern side of the basin. This model contrasts with a previous interpretation that deltaic systems in a passive margin setting south and southwest of the basin were the main source areas. A similar style of younger foreland basin has been previously identified over a distance of 1000 km in central and eastern Venezuela and Trinidad. Eocene-Recent ages of foreland basin sedimentation in these areas suggest time-transgressive oblique collision of an exotic Pacific-derived Caribbean plate along the northern passive margin of continental South America.