THE INFLUENCE OF PANGEA BREAKUP ON CLIMATE: THE CASE STUDY OF JURASSIC CONTINENTAL SUCCESSIONS IN NORTH-EASTERN MEXICO

The breakup of Pangea is a regional-scale tectonic event, which influenced the distribution of land and oceanic masses, produced rearrangements of the hydrographic pattern and atmospheric circulation, and fundamentally controlled the climatic setting of the planet. Jurassic continental successions associated with the initial stage of Pangea breakup are superbly exposed in Mexico, representing a natural laboratory to understand the control of tectonics over climate. In this contribution, we present preliminary results from the Lower-Middle Jurassic successions in NE Mexico. In particular, we compare the climatic conditions of two areas located at the same paleolatitude during Jurassic times: the Huizachal area in Tamaulipas and the Real de Catorce area in San Luis Potosí. In the Huizachal area, the Lower-Middle Jurassic La Boca Formation comprises alluvial fan, floodplain, and crevasse-splay deposits interbedded with volcanic rocks. The main source rocks that fed these fluvial deposits are: 1) Jurassic volcanic rocks of the Nazas Igneous Province, 2) Proterozoic high-grade metamorphic rocks of the Novillo Complex, and 3) Paleozoic low-grade metamorphic rocks of the Granjeno Complex. The mineralogical and geochemical composition of sandstone and siltstone indicates that deposits of the La Boca Formation preserve the composition of source rocks, and contain labile minerals that are largely subjected to weathering, like feldspar, apatite, pyroxene, amphibole, epidote, titanite, and garnet. These data preliminarily suggest that the La Boca Formation was deposited in a dry and alkaline environment. These conditions are also supported by the occurrence of calcite nodules in interlayered paleosols. At the same paleolatitude, ~200 km to the west of the Huizachal area, Lower Jurassic fluvial deposits of the Cerro El Mazo Formation are exposed in the Sierra de Catorce area. These deposits contain a well-preserved fossil flora indicating deposition in a humid and warm environment, which is reasonable given the near-equatorial position of Mexico during the Jurassic. Based on our data, we discuss the possibility that differences in climate along the same latitude are the manifestation of the rain-shadow effect triggered by a large topographic high, which was formed by extensional tectonics during the breakup of Pangea. This project is funded by PAPIIT grant IN105421.