CONSTRAINING THE TIMING OF TECTONIC ACTIVITY ALONG THE CARIBBEAN-SOUTH AMERICAN PLATE BOUNDARY BASED ON TOPOGRAPHIC RELIEF, NORTHERN AND CENTRAL RANGES, TRINIDAD

It is 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 up have ceased, and can in principal, even cause an increase in peak elevation (but always decreases mean elevation). Additionally, a plausible relationship between the topographic relief and rate of erosion in a mountain range has been published. The effects of topographic relief, erosion rate, and isostatic rebound can be combined to develop order of magnitude scale estimate of rates of uplift (e.g. Ahnert, 1970). We integrate more recent estimates of the relief vs. erosion rate relationship (Montgomery and Brandon, 2002) into a simple numerical model that examines the topographic evolution of a mountain range in response to isostatic rebound and erosion. This model is applied to the Northern Range and the Central Range in Trinidad. The Northern Range is a rugged mountain chain with approximately 900 m of relief, but is not immediately adjacent to an active fault. The Central Range mountains follow the active Central Range fault and consist of low rolling hills with a maximum relief of approximately 300 m. In the recent geologic past (<2-3 Ma ?) movement on the Caribbean-South American plate boundary stepped south to the Central Range fault zone. Preliminary model results place constraints on the rate of uplift and crustal root geometry needed to maintain the current relief in the Northern Range. Similarly, our tentative model results for the Central Range mountains have the potential to place broad constraints on the duration of modern deformation and the rates of uplift characterizing this low relief range.