Tectonic significance of paleomagnetic data from northern Venezuela

Abstract

A paleomagnetic study, mostly of basic intrusive rocks of Cretaceous and Tertiary age from northern Venezuela, includes 153 samples from 31 sites, of which only 6 sites failed to give consistent results. Fifteen sites within the Caribbean Mountains have easterly declinations with shallow, mixed positive and negative inclinations. These anomalous vectors are interpreted to be the result of tectonic rotation about vertical axes rather than to reflect anomalous magnetic field orientations associated with a polarity transition. Although these sample sites are within igneous intrusive bodies with no control on the original attitude during acquisition of the natural remanent magnetization, the relative conformity of data from numerous separate intrusions requires an average 90° megatectonic rotation of both the Villa de Cura and Tinaco tectonic belts of the Caribbean Mountains. On the other hand, seven sites from the Paraguana Peninsula (and two sites from the younger Tertiary Falcon basin) have southerly declination and positive inclination. These vectors can be explained by rotation about horizontal east‐west axes during Cenozoic folding. A compilation of available paleomagnetic data from rocks of Cretaceous age in the Caribbean indicates that anomalous declinations are widespread in both the Greater Antilles and Caribbean Mountains. We interpret these data to support previous suggestions of megatectonic rotations of a more linear, north‐south trending Mesozoic island arc system that included portions of the Greater Antilles and Caribbean Mountains of Venezuela.