Abstract

The Lower Cretaceous Cupido and Coahuila platforms of northeastern Mexico form part of the extensive carbonate platform system that surrounded the ancestral Gulf of Mexico. A sequence-stratigraphic model for these Barremian to Albian platforms was constructed from regional correlations of vertical cycle stacking patterns constrained by newly acquired biostratigraphic data and C and Sr isotope stratigraphy. The Cupido shelf lagoon (Barremian-Aptian) is composed of up to 150 peritidal cycles, which stack into high-frequency sequences that are correlated across the shelf. Cupido high-frequency sequences build into a lower partial composite sequence (Cu1), an overlying full composite sequence (Cu2), and the transgressive base of a third composite sequence (Cu-Co3) related to backstepping of the Cupido platform. The highstand part of Cu-Co3 is recorded in evaporite and carbonate facies of the Coahuila platform (Aptian-Albian). More than 80 meter-scale evaporite-to-carbonate cycles characterize the restricted interior of the Coahuila platform and stack into two full composite sequences (Co4, Co5). The Coahuila platform was drowned in the latest Albian or earliest Cenomanian, terminating shallow-water carbonate sedimentation in the region.

Regional correlations of the depositional sequences in northeast Mexico with coeval platforms in Texas and the northern Gulf coast indicate that the lower two composite sequences of the Cupido shelf correlate with the lower part of the Sligo-Hosston platform in Texas. The transgressive systems tract of the third composite sequence of the Cupido-La Peña is recorded in Texas by the upper Sligo and Pearsall formations. The highstand systems tract and the disconformable top of the third composite sequence (Coahuila platform) is likely coeval with the upper Glen Rose platform in Texas. The fourth and fifth composite sequences are correlative with the Fredericksburg platform and the Washita-Devils River platforms of Texas, respectively. We conservatively correlated our sequence-stratigraphic framework with composite "global" sequences and "eustatic" curves derived from several other basins. Given the available time resolution, results are variable, but sequence boundaries at the top of Cu-Co3 and Co5 appear to have clear interbasinal equivalents.

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