Geophysics and the structure of the Lesser Antilles forearc.

Abstract

The Barbados Ridge complex lies E of the Lesser Antilles volcanic arc along the E margin of the Caribbean Plate. The complex dates in part from the Eocene, and elements of the arc system have been dated as Late Cretaceous and Late Jurassic, although most of the volcanic rocks date from the Tertiary, particularly the latter part. It is probable that the arc system was moved a considerable distance eastward with respect to N and S America during the Tertiary. The accretionary complex can be divided into zones running parallel to the arc. There are major longitudinal variations in the complex that are broadly related to the northward decrease in sediment thickness away from terrigenous sources in S America and that are locally controlled by ridges in the oceanic igneous crust passing beneath the complex. An important feature of the complex is the underthrusting of undeformed sedimentary horizons at least 80km westward beneath the accretionary wedge. The geology of Barbados and seismic stratigraphy show that the complex has had an episodic rather than a smoothly evolutionary or steady-state history. -from Authors