Lower Cretaceous stratigraphy and depositional systems in northwestern Coahuila, Mexico

The stratigraphic relationship of Lower Cretaceous rocks in northern Mexico is poorly understood because they have not been studied in detail. One of the main objectives of this study is to analyze the Lower Cretaceous stratigraphy in northwestern Coahuila and to establish the relationships of the rocks with those of Trans-Pecos Texas. The present study comprises the lithostratigraphy and biostratigraphy of the seventeen formational units that constitute the Lower Cretaceous in northwestern Coahuila. Based on this information, paleogeographic reconstructions show the major stages of these events. The Lower Cretaceous rocks in northwestern Coahuila represent two major depositional cycles. The first extended from Neocomian to Late Aptian and was the result of a continuous transgression over the Late Jurassic El Burro-Peyotes Peninsula. The second cycle represents a shelfal progradation throughout all the Albian. This last cycle can be divided into two stages. The first stage consisted of a carbonate ramp between the Comanche Shelf to the north and the Sabinas Basin to the south. During the Middle and Late Albian the Maverick Basin was formed towards the northeast, and represents the second stage of the progradational cycle. Here, the carbonate ramp between the Comanche Shelf and the Sabinas Basin was maintained, although a carbonate platform was developed between the Comanche Shelf to the northwest and the Maverick Basin to the northeast. The edge of this platform was marked by the reefal Devils River Trend.