Petrographic and multivariate statistical analysis to discriminate the source of the Early Cretaceous-Late Jurassic La Casita Formation and the Early Cretaceous Patula Arcosa areas in Northeast Mexico [Análisis petrográfico y estadístico multivariado para discriminar las áreas fuente de la Formación La Casita del Jurásico Tardío-Cretácico Temprano y la Arcosa Patula del Cretácico Temprano en el Noreste de México]
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abstract
During the Late Jurassic to Early Cretaceous, two large sedimentary basins in northeastern Mexico, the Sabinas basin and the Monterrey trough, accumulated thick clastic sequences. Two examples of these clastic sequences are the Patula Arkose (Early Cretaceous) and La Casita Formation (Late Jurassic - Early Cretaceous), which were petrographically and statistically analyzed in this study. The Patula Arkose, a feldsphatic arenite (Q54F38L8,-with a confidence level of the 99 %25), was deposited into continental blocks with trends to continental transition (Qm54F41L5, 99 %25 of the confidence level).The petrographic characteristics and the mineralogical relationships suggest that the source rocks of the Patula Arkose were mainly low-grade metamorphic rocks (pelitic or psammitic schists),granite or granodiorite, limestone and sandstone. La Casita Fomation is composed of lithic arenite and feldesphatic arenite (Q52F27L21, with a confidence level of the 99 %25) deposited in a dissected arc or a continental transition area (Qm52F64L14, with a confidence level of the 99 %25). The sandstone petrography of La Casita Formation in the Monterrey trough shows a very complex provenance that implicates medium to high grade metamorphic rocks, andesite, rhyolite, limestone, sandstone, and shale sources. A multivariate statistical analysis of the main components, and the application of binary diagrams of petrographic index with additive and centered logratio transformation (alr and clr) confirmed the source rocks composition, suggesting that: i) the Patula Arkose is richer in low-grade metamorphic fragments, which are probably related with the Ouachita Mountains with 99 %25 of confidence level, and with granitic or granodioritic rocks of Permian-Triassic age; ii) La Casita Formation has affinity with the Paleozoic Las Delicias volcanic arc, Permian-Triassic and Early Jurassic arcs, and with medium to high grade metamorphic rocks that were possibly part of the Novillo Complex.
