Late Cretaceous–Miocene depositional evolution of Chiapas, Mexico: A foreland controlled by collision of Greater Antilles arc and the subsequent relative migration of the Chortís Block

Abstract

New U–Pb and “double dating” (U–Pb and U–Th)/He) age determinations on detrital zircons from Upper Cretaceous–Miocene formations greatly improve our understanding of both evolutionary and clastic provenance models for southern Mexico and the western Caribbean. Samples from the Méndez, Ocozocoautla, Angostura, Tenejapa, Soyaló, El Bosque, San Juan, Nanchital Shale, Nanchital Conglomerate, Huamelula, and Ixtapa units in the western Sierra de Chiapas, Mexico, consistently indicate a south-to-north transport of clastic detritus from orogenic headlands into the Chiapas Foldbelt Basin and, presumably, the Sureste Basin (Gulf of Mexico). However, this interpretation is partly guided by 1) palinspastic reconstructions of the Chortís Block and fault slices of the North America–Caribbean plate boundary that restore to paleo-positions south of Oaxaca and Chiapas states and western Guatemala, and 2) published fission track data that indicate the Chiapas Massif was not a significant sediment source or barrier until the late middle Miocene. In addition, zircon data on volcanic breccias (magmatic?) from cores of supposed Cretaceous and Paleogene levels of the Salina Cruz wells indicate that today’s Gulf of Tehuantepec forearc is likely the “western tail” of the Chortís Block and represents a displaced segment of the Guerrero Arc of western Mexico. Analyses of key thin sections and one heavy mineral sample complete the data set. We find that Pacific-origin Caribbean models provide the necessary inferences for meaningful interpretation of our data, and, conversely, that our data on the various depositional units through time iteratively help to support Pacific-origin models. For example, our data from Chiapas supports 1) arc collision to the south in the Maastrichtian (Greater Antilles), and 2) the existence of Paleogene orogenic highlands south of the Chiapas Massif, interpreted here as the paleo-North America–Caribbean plate boundary zone.