Geologic Constrains on the Timing and Magnitude of Neotectonic Transpressional Deformation in the Central Range Fault Zone, Trinidad

GPS data demonstrate the Central Range fault zone in Trinidad accommodates most of the motion between the Caribbean and South American plates. The Caribbean plate is presently moving ~20 mm/yr east relative to a fixed South American plate. Striking at 071, the Central Range fault zone has dextral transpression kinematics with an angle of oblique convergence of approximately 20 degrees. While the recent, active nature of this fault zone is well documented by previous GPS studies, the total plate motion accommodated is uncertain. We attempt to constrain this value with topography, fold geometries, and paleomagnetism. Using an isostatically compensated transpressional model that incorporates erosion, the topography (300 m max.) of the Central Range fault zone suggests 5-11% shortening (2-5 km shortening). Assuming that this shortening occurred under present kinematic conditions, these values suggest the Central Range fault zone accommodated 6-15 km of eastward movement of the Caribbean plate. Paleomagnetic analysis suggests the Tamana formation has experienced <9 degrees of vertical axis rotation. Under moern kinematic conditions this suggests <5 km of shortening and <15 km of total plate motion, The strain recorded in the fold belts within the Central Range fault zone suggest slightly higher values: >6.4 km of shortening and >19 km of Caribbean plate motion. These values are minimum estimates because the analysis does not taken into account shortening due to faulting. The rocks in the Central Range record the effects of both Miocene shortening and more recent deformation. However, the shortening calculated using the topography method are most likely due more recent rather than Miocene deformation. Additionally, remagnetization of the Tamana formation occurred after the Miocene, therefore the paleomagnetic data provides post-Miocene information. The higher plate motions suggested by the fold-based analysis is most likely due to the folds recording both neotectonic and Miocene contraction.