Jurassic palaeomagnetic results constraining sotherly motions of the Mixteca terrane, southern Mexico

Abstract

Geologic and palaeomagnetic studies of the Jurassic continental sedimentary units of the northern Mixteca terrane, southern Mexico were undertaken to investigate the palaeogeographic and tectonic evolution of the area. Recent results for two previously unidentified redbed units show contrasting structural characteristics which permit a critical revision of the Mesozoic palaeomagnetic record and the tectonic interpretations for the terrane. The overall mean directions for the two units after single and two-stage tilt corrections are: Otlatlepec, Dec= 347°, Inc= 25°, k=80, α95=14°.: and Piedra Hueca, Dec= 354°, Inc =4°, k=30, α95= 11°. The corresponding palaeolatitudes for the Early and Middle Jurassic are 2.2°±5.6° and 12.8o±7.9°, constraining motions for northerly positions of Mixteca terrane to smaller levels (around 10 degrees) than previously suggested. Major latitudinal displacements of the Mixteca terrane with respect to North America were completed before late Early Cretaceous (Albian) and may have taken place in conjunction with active rifting in the Gulf of Mexico and left-lateral movements along the Mojave-Sonora megashear during middle Jurassic times.