INTEGRATING ISOSTASY INTO TRANSPRESSION: A PRELIMINARY APPLICATION TO THE CENTRAL RANGE FAULT SYSTEM, TRINIDAD

The application of transpressional models to modern plate boundaries has advanced our understanding of the processes active at obliquely convergent zones throughout the world. Successful application of customized refinements of the original Sanderson & Marchini model (i.e. inclined transpression, partitioned transpression, distributed transpression, etc.) provide even more useful insights to particular plate boundaries. Regardless of the specifics of individual models, all transpressional models result in the convergence between two bodies and the uplift/exhumation of the material in the deforming zone (i.e. the formation of relief). The original, and most of these more complex models of transpression, do not take the effects of isostatic compensation into account. We present a two dimensional model of the convergent component of transpression (i.e. pure shear) that integrates the effects of airy isostasy into material flow in transpression. In an isostatically compensated transpressional model flow of material within the deforming zone relates upward flow (i.e. the development of relief) to downward flow (i.e. the formation of a crustal root). Addition of a forward gravity model component to the kinematic model allows for the downward flow component of deformation to be related to an expected gravity anomaly. Using the rates of convergence across a relatively young transpressional boundary (<3 Ma), the Central Range fault system in Trinidad, our model makes specific predictions concerning the relief across the Central Range Mountains and gravity anomaly associated with their underlying root. While the model is in its preliminary stage of development (it does not account for erosion), the results indicate most of the flow in the vertical dimension is downward. This suggests it may be critical to incorporate isostasy into transpressional models applied at the plate boundary scale.