Boletín de la Sociedad Geológica Mexicana
versão On-line ISSN 1405-3322
RUBIO CISNEROS, Igor Ishi; RAMIREZ FERNANDEZ, Juan Alonso e GARCIA OBREGON, Raúl. Source analysis of jurassic clastic rocks in the Huizachal Valley, Sierra Madre Oriental: influence from synsedimentary volcanism and the crystalline basement. Bol. Soc. Geol. Mex [online]. 2011, vol.63, n.2, pp.137-156. ISSN 1405-3322.
The Huizachal valley is the southernmost canyon that cuts the Huizachal-Peregrina Anticlinorium of the Sierra Madre Oriental (Ciudad Victoria, Tamaulipas). In this work, a preliminary petrological study of the volcanic and clastic (red beds: shales, siltstones, sandstones, and conglomerates) units of the Jurassic La Boca and La Joya Formations was carried out. The La Boca Formation was divided into two members: the older member has a near-vertical dip, while the upper member is sub-horizontal. These members are overlain by red beds of the La Joya Formation. The sedimentary fill consists of alluvial and fluvial deposits distributed irregularly, with a high influence of volcanic detritus derived from igneous rocks emplaced at the base and in the middle parts of the measured geological profile. The volcanic rocks consist of basaltic-andesitic lava flows and pyroclastic deposits at the base and rhyolitic domes and complex pyroclastic deposits (lahars, ignimbrites, and other types of tuffs) in the upper part of the sequence. Petrographic analysis of the main constituents of the sandstones from both formations reveals the presence of two petrofacies. The first one corresponds to the La Boca Formation lower member, and the second to the La Boca Formation upper member and the La Joya Formation. The first petrofacies corresponds to feldespathic to lithic arenites deposited in a transitional arc zone with a tendency to dissected arc. The second petrofacies comprises lithic arenites deposited in a recycled orogen setting. The petrofacies reflect a provenance by means of the quartz content in low to mid-grade metamorphic rocks (schists, sepentinites, and gneisses), and igneous rocks (rhyolites). Moreover, the recognition of metamorphic lithics validates the provenance of detritus from the NE Mexico basement. The differentiation of the volcanic lithic content based on its textural characterization has confirmed the normal position of the sequence, and also demonstrated the influence of recycling and/or exhumation of the volcanic, sedimentary and crystalline basement sequence. The composition of the Huizachal valley sandstones varies from base to top due the complex regional tectonic history that involves the presence of a heterogeneous crystalline Precambrian to Paleozoic basement, the extensional regime related to the opening of the Gulf of Mexico, and the emplacement of a Jurassic volcanic arc.
Palavras-chave : Provenance; La Boca Formation; La Joya Formation; red beds; Huizachal valley.