40 The western equatorial Pangea: Geological, geophysical, geochronological, and paleoecological insights on the youngest supercontinent assembly and breakup on Earth (Part 2)
This session welcomes studies in Mexico, southwestern North America, and northwestern South America investigating the Pangea’s supercontinent cycle from tectonic, stratigraphic, paleoecologic, geophysical, geochronologic, and paleogeographic perspectives to offer insights into its assembly and breakup.
Friday, 24 April 2026
1:30 PM - 5:30 PM
LMH, Isla Carmen
Climatic Reorganization of Western Equatorial Pangea During Early–Middle Jurassic Continental Rifting in Mexico
Paper number: 40-9
Program: Technical Sessions
Time: 4:05 PM – 4:25 PM
Authors
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Jorge Ruiz Urueña Presenting AuthorUniv Nacional Autonoma de México, México Distrito Federal, México
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Michelangelo MartiniUNIVERSIDAD NACIONAL AUTONOMA DE MEXICO, INSTITUTO DE GEOLOGIA, Ciudad de Mexico, CDMX
Abstract
An integrated sedimentological, mineralogical, and geochemical analysis of the La Boca, Huayacocotla, and Cahuasas formations (Early–Middle Jurassic) provides new constraints on the tectonic, climatic, and sedimentary evolution of western equatorial Pangea during the initial stages of supercontinent breakup. These continental fluvial successions, deposited within the Nazas continental rift province along the western margin of Mexico, record pronounced spatial and temporal variability in depositional systems, provenance, and weathering intensity that reflect dynamic feedbacks between extensional tectonics, topography, and atmospheric circulation.
The La Boca and Cahuasas formations record fluvial systems developed predominantly under arid to semi-arid. The Toarcian to Callovian La Boca Formation is characterized by distributive fluvial systems with extensive floodplains, pedogenic carbonate development, low chemical weathering indices, and the preservation of labile volcanic minerals, indicating limited leaching under dry conditions. Similarly, the Aalenian–Callovian Cahuasas Formation reflects anastomosed fluvial systems with moderate weathering, semi-arid, recycled detritus from older successions, and episodic volcanic input. In contrast, the upper member of the Huayacocotla Formation documents braided fluvial systems deposited under persistently humid to per-humid tropical climatesas, as indicated by strong feldspar depletion in some petrofacies, coal layers, carbonaceous facies, and abundant plant remains during the Sinemurian–Pliensbachian.
Together, these records reveal a major Early–Middle Jurassic climatic transition across western equatorial Pangea, from humid tropical to semi-arid–arid regimes. This shift is not explained by paleolatitudinal drift, but instead corresponds to tectonic reorganization and uplift along the North Oaxacan Transfer system and associated faults. The resulting orographic barriers likely imposed a rain-shadow effect, enhancing precipitation to the southwest while promoting aridity in interior rift basins.
These results highlight the first-order role of extensional tectonics and topographic growth in shaping regional climate patterns during the breakup of Pangea, providing a framework for understanding climate heterogeneity along the western equatorial margin of the youngest supercontinent.
Geological Society of America Abstracts with Programs. Vol. 58, No. 3
doi: 10.1130/abs/2026CD-410901
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