Neotectonic evolution of the Isthmus of Tehuantepec (southeastern Mexico)

• Published in: Tectonophysics 1998-03, Vol.287 (1), p.77-96
• Main Authors: Barrier, Eric, Velasquillo, Luis, Chavez, Mario, Gaulon, Roland
• Format: Article
• Language: English
• Subjects: fault analysis; North-Central America; seismotectonics; Tehuantepec; triple junction
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/S0040-1951(98)80062-0

The Isthmus of Tehuantepec of southeastern Mexico is located near the triple junction of the North American, Cocos and Caribbean plates. A neotectonic study, including fault tectonic analysis and study of sub-surface data, was performed in order to understand the tectonic evolution of this complex zone. The Plio—Quaternary fault pattern is described and the brittle structures are interpreted in terms of palaeostress orientations. We propose a model of tectonic evolution of the Isthmus of Tehuantepec since the Late Miocene (∼6 Ma) characterized by extensional tectonics. The present structure of the isthmus results from the superimposition of three distinct types of tectonism: (1) a tilting of the eastern Isthmus during the Late Miocene—Early Pliocene, along a major N—S-trending normal fault zone (the Isthmus Fault Zone), as a consequence of the deformation of the subducting slab of the Cocos plate along the subducted part of the Tehuantepec Fracture Zone; (2) the subsidence of the southern isthmus in relation to N—S extension, associated with the eastward displacement of the western Caribbean plate with respect to the southern North-American plate along the Polochic—Motagua fault system; and (3) extensions that develop in the northern half of the Isthmus related to the evolution of the passive margin of the Gulf of Mexico.