Southwest migration of the instantaneous Rivera-Pacific Euler pole since 0.78 Ma

Abstract

Establishing an Euler pole/vector which accurately describes the present-day motion between the Rivera and Pacific plates has proved difficult. This is likely due to systematic errors in the plate motion data; errors arising from a SW migration of the Rivera-Pacific Euler pole during the past several million years. A new estimate of the present-day instantaneous Rivera- Pacific Euler pole is derived herein using only the most recently formed bathymetric features along the Rivera-Pacific boundaries. This Euler pole (24.62°N, 105.89°W) lies significantly SW of all the previous pole determinations, indicating a continued (2° or more) SW migration of the Rivera-Pacific Euler pole during the last 0.78 Ma. Although many uncertainties remain to be resolved, this migration provides a simple explanation for the discrepancies between predicted plate motions and (1) the observed azimuths of the eastern end of the Rivera transform, (2) the extensional morphology of the Rivera-Cocos boundary, and (3) the rates of RIV-NA and Cocos-North America motion across the Rivera-Cocos boundary as indicated from seismotectonic relationships.