Sandstone Provenance of the Arperos Basin (Sierra de Guanajuato, Central Mexico): Late Jurassic-Early Cretaceous Back-Arc Spreading as the Foundation of the Guerrero Terrane

Three paleogeographic scenarios have been proposed for the Mesozoic volcano-sedimentary successions that compose the Guerrero terrane, western Mexico. In the type 1 scenario, the Guerrero terrane is an exotic Pacific arc accreted to nuclear Mexico by the consumption of a pre-Cretaceous oceanic basin, named Arperos Basin. The type 2 scenario considers the Guerrero terrane as a fringing multiarc system, accreted by the closure of pre-Cretaceous oceanic basin substrates at multiple subduction zones with varying polarities. In the type 3 scenario, the Guerrero terrane is interpreted as a North American west-facing para-autochthonous arc, which was drifted in the paleo-Pacific domain by the opening of the Cretaceous back-arc oceanic Arperos Basin. To test these reconstructions, we present here a combined study that includes geologic mapping, stratigraphy, U-Pb geochronology, and sandstone provenance data from the Arperos Basin in the Sierra de Guanajuato, central Mexico. Our data document that the Arperos Basin developed in a back-arc setting and evolved from continental to open oceanic conditions from the Late Jurassic to the Early Cretaceous. Sandstone provenance analysis shows an asymmetric distribution of the infill sources for the Arperos Basin: continent-recycled sedimentary rocks were deposited along its northeastern side, whereas magmatic arc-recycled clastic rocks developed at its southwestern side. Such asymmetric distribution closely fits with sedimentological models proposed for present-day continent-influenced back-arc basins. On the basis of this evidence, we favor a type 3 scenario for the Guerrero terrane, which is then considered to represent a detached slice of the Mexican leading edge that drifted in the paleo-Pacific domain during back-arc extension and subsequently accreted back to the Mexican craton.