Mexico: Basement framework and pre-Cretaceous stratigraphy

Provenance determinations of sediment deposited in circum–Gulf of Mexico basins rely on understanding the geologic elements present in the basement provinces located from northeast Mexico to Honduras. Relevant geologic features of these provinces are herein summarized in text and pictorial form, and they include the Huizachal-Peregrina uplift, western Gulf of Mexico, Huayacocotla, Zapoteco, Mixteca, Xolapa, Juchatengo, Cuicateco, Mixtequita, south-central Chiapas, southeast Chiapas, western Guatemala, central Guatemala, Maya Mountains, and the Chortis block. We recognized basement elements of local character that serve as fingerprints for specific source areas. However, many elements are ubiquitous, such as 1.4–0.9 Ga, high-grade metamorphic rocks that occur both as broad exposures and as inliers in otherwise reworked crust. Xenocrystic and detrital zircon of Mesoproterozoic age is very common and hence not diagnostic of provenance. Neoproterozoic rocks are very scarce in Mexican basement provinces. However, Ediacaran–Cambrian detrital zircon grains are found in Mexican Paleozoic strata; these were possibly derived from distant sources in Gondwana and Pangea. Ordovician–Silurian magmatism is present in approximately half the provinces; magmatic detrital zircon of such age is somewhat informative in terms of provenance. More useful populations are detrital zircon grains with Ordovician–Silurian metamorphic overgrowth, which seem to be mainly sourced from the Mixteca region or the southern Chiapas Massif. Devonian basement has only been discovered in the Maya Mountains of Belize, and detrital zir-on of such age seems to be characteristic of that source. A similar case can be made about Carboniferous zircon and the Acatlán Complex, Middle Pennsylvanian zircon and Juchatengo plutons, and Late Triassic zircon and the basement exposed in central Guatemala. In all these cases, the age and geographic extent of the zircon source are restricted and serve as a distinct fingerprint. Plutons of Permian–Early Triassic age are widespread, and detrital zircon grains from them are rather nonspecific indicators of source area. Future dating of detrital white mica using 40Ar-39Ar could help in recognizing Carboniferous–Triassic schist from more restricted schist occurrences such as west Cuicateco (Early Cretaceous) and central Guatemala (Late Cretaceous).