Abstract
A brief summary of the petrotectonic assemblages involved in the Cretaceous to early Tertiary orogeny of the Caribbean Mountain System is presented in order to delineate those geological constraints pertinent to a plate tectonic interpretation of the area. In particular, it is concluded that the Mesozoic sediments caught up in the orogeny were originally deposited along a quiescent Atlantic-type continental margin or “tensile open series geosyncline” (Wang, 1972) and not in association with an active subduction zone. Moreover, paired metamorphic belts are not found, and all metamorphic rocks, whose grade increases from south to north across the orogenic belt, are of medium- to high-pressure type. Thus a collision-type model appears to be more appropriate as the major mountain-building mechanism than the cordilleran-type mechanism proposed for the Caribbean Mountain System by various authors. An alternate tectonic model which incorporates the following main stages in tectonic development is suggested: (1) formation of an Atlantic-type continental margin along northern South America by continental rifting in middle Mesozoic time or earlier; (2) movement of an oceanic plate with a leading edge characterized by a subduction-zone–island-arc complex toward this continental margin; (3) collision in Late Cretaceous time; (4) overriding of the island arc over the continental margin, resulting in widespread gravity sliding and thrusting, and high p/T metamorphism of the shelf and rise sediments; and (5) isostatic readjustment due to reorganized plate movement in the early Tertiary. Ephemeral subduction zones active during this sequence of events explain the singular pattern of sporadic volcanism observed during this time span. The direct applicability of this model to areas outside of the region of interest is limited. Necessary restrictions on timing and plate movement in the Caribbean area, however, suggest that a probable feature of the most likely model for the tectonic evolution of this area will be the insertion of an oceanic plate from the Pacific between North and South America in late Mesozoic time.
