Boletín de la Sociedad Geológica Mexicana Volumen 69, núm. 3, 2017, p. 691 ‒ 709

Field guide to the Jurassic Otlaltepec and Tezoatlán Basins, southern Mexico: sedimentological and paleontological records of Puebla and Oaxaca

Michelangelo Martini^1,*, Patricia Velasco-de León², Mildred Zepeda-Martínez³, Diego E. Lozano-Carmona², Mónica Ramírez-Calderón³

¹ Instituto de Geología, Universidad Nacional Autónoma de México, CDMX, 04510, México.
² Facultad de Estudios Superiores Zaragoza, Universidad Nacional Autónoma de México, CDMX, 09230, México.
³ Posgrado en Ciencias de la Tierra, Universidad Nacional Autónoma de México, CDMX, 04510, México.

* This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

By early Mesozoic time, a major plate reorganiimages/epoca04/6903/zation produced the breakup of Pangea, which was the most recent supercontinent assembled on Earth. Due to its paleogeographic position along the emergent plate boundary between North and South America, the early Mesozoic tectonic history of Mexico was dominated by the development of major normal to strike-slip faults. These faults produced a complex crustal configuration characterized by subsiding basins bounded by exhuming basement highs. Voluminous, continental to marine sedimentary successions were accumulated into these basins during the Jurassic, representing a unique stratigraphic record related to the fragmentation of the western equatorial margin of this supercontinental mass.

This field trip will provide an overview of the Otlaltepec and Tezoatlán Jurassic Basins that are exposed in the states of Puebla and Oaxaca, southern Mexico. Observed outcrops are exposed along two amazing canyons and consist of alluvial-fluvial to marine clastic deposits. Major provenance changes are recorded in the Jurassic successions of the Otlaltepec and Tezoatlán Basins and are interpreted as the result of exhumation of different fault-bounded lithospheric blocks during Pangea breakup. The integration of petrological and paleontological data indicates that these major changes in provenance of clastic rocks match with changes in climatic conditions. Therefore, in this field trip, we will have the opportunity to explore the hypothesis that the progressive exhumation of lithospheric blocks during the fragmentation of Pangea could have produced major topographic changes that favored local variations in climatic conditions and consequently, the diversification of floral assemblages in Mexico.

Keywords: Pangea breakup, intra-continental rift basin, southern Mexico, Jurassic flora.