Abstract

Thermochronometry is used to better understand the processes responsible for Cenozoic magmatism and exhumation of the Chiapas Massif Complex that spans a diffuse triple junction between the Caribbean, North American and Cocos plates. A combination of zircon U-Pb, apatite fission tracks, (U-Th)/He as well as numerical modeling show contrasting histories. Exhumation started earlier in the south (~16 Ma) relative to the north (~9 Ma). Northern exhumation is related to activity on the Tonalá fault system, while to the south it may be correlated with transpressive deformation in Chiapas fold-and-thrust belt. The southern block also experienced significant topographic growth from ~5 Ma to ~1 Ma followed by intense erosion. Overall, the pattern of uplift is in agreement with the ‘closing zipper’ model in which a forearc sliver is progressively incorporated to the North American plate. Thermal models also support a Pleistocene decrease in topography consistent with independent paleoenvironmental and geomorphologic evidences.

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