A preliminary paleomagnetic pole for mid-Cretaceous rocks from Tobago: further evidence for large clockwise rotations in the Caribbean-South American plate boundary zone

The island of Tobago occupies the eastern end of the central (igneous) belt of the Caribbean-South American plate boundary zone. Volcaniclastic sediment of the Albian (∼ 100 Ma) Tobago Volcanic Group and dikes of similar age within it were sampled in two homoclinal sections with different attitudes. The mean of virtual geomagnetic poles for 12 sites (25.4°N, 24.1°E, A95 = 4.2°) is well defined, pre-tilting and apparently reliable, yet is far removed from a similar age reference pole for South America. Five other paleomagnetic studies of Cretaceous rocks from widely separated localities farther west in the plate boundary zone yield pole positions that are remarkably similar to the Tobago pole. Poles obtained from the Guajira Peninsula of Colombia, the islands of Aruba and Bonaire, and the Caribbean Mountains of Venezuela are among those that agree with the Tobago result. The paleolatitudes for study areas within the plate boundary zone are consistent with an origin on or near South America, yet the poles throughout the zone are rotated roughly 90°. Dextral relative motion between the Caribbean and South American plates was probably responsible for the rotation.