Palaeomagnetism and tectonics of Mexico

Abstract

Palaeomagnetic results for Mexico which cover the interval from the Cambro-Ordovician to Neogene are reviewed and briefly discussed in terms of regional tectonic models proposed for the evolution of Mexico. Following plate tectonic reconstructions of Atlantic bordering continents and the diversity of blocks or terranes shaping Mexico with distinct tectono-stratigraphic histories, one may expect a palaeomagnetic record for Mexico in which directions and poles show an increasing angular divergence going back in time with respect to those of stable North America. This would imply that the palaeomagnetic discordances should be similar to those documented for the Cordilleran Orogenic Belt. This 'expected' record. is however not observed. Instead, many Palaeozoic poles for Mexico lay close to the corresponding North American poles, whereas most Cenozoic poles diverge from the corresponding North American poles. Several alternatives, including both tectonic and non-tectonic explanations, are considered. The Mesozoic and Cenozoic palaeomagnetic results from Mexico are different from those observed to the north within the Cordilleran Orogenic Belt, suggesting a distinct tectonic evolution for the southern portion of the orogenic belt. Palaeomagnetic data are in general consistent with models implying regional left-lateral motion of parts of Mexico. The tectonic evolution of Mexico however seems more complex than previously predicted.