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

Abstract

By early Mesozoic time, a major plate reorganization 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.

Bajocian transgressive-regressive sequences of the Tecocoyunca Group, southern Mexico, with maximum flooding surfaces marked by Thalassinoides

“…1B, D). We se lected this sec tion be cause it is the best ex posure in the area, rep re sen ta tive of the Mid dle Ju ras sic ma rine trans gres sion rep re sented in the Tecocoyunca Group , that has been vis ited by many in ter na tional re searchers dur ing dif fer ent field trips or ga nized in the last 60 years (e.g., Erben, 1956b;Mar tini et al, 2017). Most of the pre vi ous stud ies were mostly fo cused on palaeontological finds.…”