Mapping and Un-Subducting the Cocos Slab: Implications for the Tectonic History of Mexico and Central America
Jason Wan, Department of Geology, Carleton College, Northfield, Minnesota
Jonny Wu, Department of Geosciences, University of Arizona, Tucson, Arizona
Will McCraine, Department of Geosciences, University of Arizona, Tucson, Arizona
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Abstract
The Cocos subduction zone is among the most tectonically complex convergent margins on Earth, yet the geometry of its subducted slab remains not well-constrained. Characterizing the geometry of the subducted Cocos slab and reconstructing its tectonic evolution are essential for understanding the tectonic history, regional geodynamics, and mantle flow beneath Central America. Here we map the Cocos slabs and general mantle structure beneath present-day Mexico and Central America using Benioff seismicity together with the recent SATONA P- and S-wave full-waveform tomography model (Hua et al., 2025). For comparison, we also map the slab using the UUP07 global P-wave tomography model (Amaru, 2007).
In the upper 400 km, SATONA shows the Cocos slab is segmented into four along-strike domains (A-D) characterized by distinct slab dips and geometries. From northwest to southeast, the Cocos slab dip changes from ~60° in Domain A to shallower-dipping ~35° in Domain B, then steepens to ~65° in Domains C and D, with Domain D distinguished by more extensive fragmentation. The four domains appear to be segmented by slab tears that occur beneath approximately 97°W, 94°W, and 84°W longitudes. These slab tears coincide with major changes in Benioff seismicity and Holocene volcanism along the Cocos subduction zone in southern Mexico and southern Costa Rica. The boundary between Domains B and C may correspond to a slab window associated with southwest Mexico flat-slab subduction, while the tear between Domains C and D may be associated with the recent (<3 Ma) subduction of the Cocos Ridge. Below ~400 km depth, the Cocos slab appears vertically segmented and relatively fragmented in SATONA. In general, the Cocos slab appears more fragmented than previously recognized in global tomography, such as UUP07.
Paleogeographic reconstructions indicate that ~1800 km of Cocos slab has been subducted since the inception of Cocos subduction ~23 Ma. Our mapped slabs account for ~1500 km of subducted lithosphere, equivalent to ~19 Myr of Cocos subduction, assuming minimal post-subduction deformation (e.g., no slab buckling or pure shear thickening). We aim to un-subduct our mapped Cocos slab to further reconstruct the tectonic history of Central America during the Cenozoic.
Session
Large-scale tectonics