CONSTRAINTS ON THE TIMING OF DEFORMATION IN THE CENTRAL RANGE FAULT ZONE, TRINIDAD, FROM TOPOGRAPHY AND APATITE FISSION TRACK DATA

A well documented relationship exists between the topographic relief and rate of erosion in a mountain range. It is also well established that isostatic rebound in response to erosion increases the longevity of mountain ranges as positive topographic features long after the tectonic forces that originally created them have ceased. The effects of topographic relief, erosion rate, and isostatic rebound can be linked to uplift and exhumation rates. With an assumption of a geothermal gradient, cooling rates can also be calculated. We present a simple, one-dimensional numerical model that examines the topographic evolution, uplift, exhumation, and cooling of a mountain range in response to isostatic rebound and erosion. Model results are applied to the active portion of the Caribbean-South American plate boundary in central Trinidad. The Central Range Mountains are a low relief topographic feature (approx. 150 m along the divide) that follows the modern plate boundary. It is uncertain if the current topographic relief and/or faulting and folding in the Central Range fault zone is the result of modern deformation or the remains of Late Miocene contraction. Model results suggest the Central Range could have been a moderate relief feature (e.g. 600 ± 300 meters) in the Late Miocene. This suggests that only a moderate amount of exhumation has occurred since the Late Miocene, which is consistent with the approximately 12 Ma. Apatite fission track ages found throughout the Central Range. Additionally, fission track length modeling using the HeFTy software package yields cooling rates that are broadly consistent with the rates suggested by the numerical model. The topography, apatite fission track ages, and track lengths are all consistent with a Late Miocene tectonic event. If this is the case, then it implies that much of the deformation in the Central Range fault zone is also Late Miocene in origin rather than the result of modern, active deformation.