CONCORDANT PALEOMAGNETIC DIRECTIONS FROM THE TEHUANTEPEC ISTHMUS - CONSTRAINTS ON THE NEOGENE EVOLUTION OF THE NORTH-AMERICAN CARIBBEAN PLATE BOUNDARY

We report paleomagnetic data for Miocene igneous rocks of the southeas tern Tehuantepec Isthmus region, Mexico. Thermal and alternating field demagnetization reveal predominantly normal polarity magnetization, i nterpreted as primary TRM. The overall mean direction (Dec = 355.6-deg rees, Inc = 36.5-degrees, k = 36.4, a95 = 9.3-degrees, N = 8 sites) is statistically indistinguishable from the expected direction, calculat ed using the North American reference pole. This result indicates that significant rotation or displacement of the Tehuantepec region relati ve to the craton has not occurred since 13 Ma.