Procedencia de la Formación La Casita y la Arcosa Patula: implicaciones para la evolución tectono-magmática del NE de México entre el Carbonífero y el Jurásico
During Valanginian-Hauterivian time, La Casita Formation (Monterrey trough) and the Patula Arkose (Sabinas basin) formed sedimentary units distributed in the southeast and northeast edge of the Coahuila block. The present article discriminates the character of the different geotectonic elements that form northeastern Mexico and integrates petrographic studies of sandstone and geochronology of detrital zircons. La Casita Formation consists of volcano-plutonoclastic petrofacies with quartz-feldspathic trends, showing volcanic lithic influence with felsitic, microlitic, lathwork, and plutonic lithic fragments with myrmekitic textures, as well as metafelsitic/psammitic3y4 lithics; in contrast, the Patula Arkose is characterized by sedimentary- plutonoclastic petrofacies, with a high content of plutonic lithics with myrmekitic, metapelitic2, and metapsammitic2 textures, and a subordinate content of volcanic lithics with felsitic and lathwork textures.
The detrital zircon ages vary from 2885 to 164 Ma with a high percentage of grains (57%) located in the range of 275 to 240 Ma. Four age populations, A-D, and two subpopulations were defined considering probability peaks and lows of all ages obtained: Zircon population A (>700 Ma; Paleoproterozoic-Neoproterozoic); population B (700–500 Ma; Neoproterozoic - middle Cambrian); population C (500–450 Ma; middle Cambrian - Middle Ordovician); population D (350–160 Ma; early Carboniferous - Middle Jurassic). In La Casita Formation, the Carboniferous to Jurassic zircons show multiple magmatic-arc sources in the north and east of Mexico, prominent among them are the Carboniferous- Permian arc, the Permo-Triassic magmatic arc, and volcanic rocks of the Upper Triassic - Middle Jurassic Nazas Formation. On the other hand, Mesoproterozoic and Neoproterozoic to Devonian zircons indicate the age of the basement of the region, which is comparable with the Novillo Complex, and the overlying Paleozoic sedimentary rocks.
The youngest detrital zircons of the Patula sandstones were probably derived from the Permo-Triassic magmatic arc, whereas the 298– 259 Ma zircons are correlated with the Las Delicias arc of Carboniferousearly Permian, and the low-grade metamorphic rocks of the CoahuilaTexas craton.
Both formations were deposited within a strike-slip basin system; however, the La Casita Formation displays provenance characteristics of continental magmatic arcs and recycled orogens (~Q56F35L9; ~Qp24Lv61Ls15), whereas Patula sandstones have characteristics of stable continental block provenance, and subordinate suture belt provenance (~Q58F33L9; ~Qp59Lv1Ls40).