Jurassic-Cretaceous paleogeographic evolution of the northern Mixteca terrane, southern Mexico

Abstract

A model of Jurassic-Cretaceous paleogeographic evolution for the northern portion of the Mixteca terrane is presented. The oldest beds of the Mesozoic sequence (Toarcian(?)-Aalenian) are exposed in the Tezoatlan-El Rosario area. These beds accumulated after a change from an uplift tectonic regime, active since Early Triassic, to an extensional tectonics with subsidence. From Callovian to Hauterivian times, shallow marine conditions dominated and calcareous and detrital deposits accumulated in the southern part of the studied region, which had been occupied by the fluvial system. The Late Jurassic paleogeography featured a shallow bay (Tlaxiaco Bay) connected to the south with the Pacific Ocean. There are no indications of Barremian-Aptian marine sedimentation in most of the Mixteca terrane. Only to the north, in the San Juan Raya area, a continuous marine Valanginian-Aptian sequence has been reported. During this time, subaerial monogenetic volcanism locally occurred near Santo Domingo Tonala. From Albian until probably Turonian, a broad calcareous platform evolved over the Mixteca and Oaxaca terranes. In post-Turonian time, general uplift contemporaneous with folding affected the studied region. -from Authors