Neotectonics in the Trinidad and Tobago, West Indies segment of the Caribbean-South American plate boundary

摘要

Despite being set in an apparently simple dextral transform plate boundary, e.g. as shown by the plate-wide GPS results of Weber et al. (2001a), the active tectonics in Trinidad and Tobago is quite complex. The principal active strike-slip fault in Trinidad, the Central Range Fault, is highly oblique to plate motion, and owing to the obliquity, a transpres-sional belt is developing in central Trinidad. Based on geometric estimates for the age of the Gulf of Paria pull-apart, which links the Central Range Fault to the active El Pilar transform fault in Venezuela, the inferred age of the transpres-sional belt is just a ～few Ma. Some contractile structures in the foreland fold-thrust strike-slip belt are probably fossil structures related to the pre-mid-Miocene oblique convergent phase of plate motion. An inferred fossil crustal root developed during earlier oblique convergence probably holds up the coastal mountains of the hinterland belt, but, the geo-morphology of northwestern Trinidad also records a km or so of total vertical subsidence into the Gulf of Paria pull-apart basin, indicating that significant parts of the coastal mountain belt are actively sinking. The dense oceanic arc-forearc terrane exposed in Tobago was obducted over. South America during oblique convergence; the Tobago terrane boundary has been reactivated and inverted, and today Tobago sinks along it, The techniques discussed here that exploit neotec-tonic signals accumulated over long times may be applicable to studying the slower, but possibly significant, intraplate neotectonics of Hungary.