Terrenos De Mexico

International Geology Review, Vol. 46, 2004, p. 765–794. Copyright © 2004 by V. H. Winston & Son, Inc. All rights reserved.

Terranes of Mexico Revisited: A 1.3 Billion Year Odyssey
J. DUNCAN KEPPIE1
Instituto de Geología, Universidad Nacional Autónoma de México, 04510 México D.F., México

Abstract
During the Precambrian and Paleozoic, Mexican terranes were either part of or proximal toLaurentia and Middle America (basements of Mesozoic Maya, Oaxaquia, and Chortis terranes that bordered Amazonia). Obduction of the Sierra Madre proximal terrane in the Late Ordovician was followed by Permo-Carboniferous amalgamation of all proximal terranes into Pangea. Middle Jurassic breakup of Pangea resulted in two continental terranes, Maya and Chortis, which were surrounded by smallocean-basin/arc terranes: Gulf of México, Caribbean Sea, Juarez, Motagua terranes, and the Guerrero composite terrane. All of these terranes were obducted onto North America during the Late Cretaceous–Early Cenozoic, Laramide orogeny. Neogene propagation of the East Pacific Rise into the North American margin has led to separation and northwest translation of the Baja California terrane.

IntroductionTERRANE MAPPING was first applied to Mexico by Campa and Coney (1983) and Coney and Campa (1984) as part of projects in the North American Cordillera (Silberling et al., 1992) and around the Pacific Ocean (Howell, 1985), with its primary purpose being an understanding of the plate tectonic evolution (Coney, 1983) and metallic mineral and energy resource distributions. Applying the principles ofterrane analysis (Jones and Silberling, 1979; Howell et al., 1985), Campa and Coney (1983) recognized 12 terranes (Fig. 1A), of which 7 were considered to be composite (C), because existing geological maps did not allow subdivision. They grouped the terranes into three categories depending on their provenance: (1) North American provenance—two Precambrian–Mesozoic terranes (Chihuahua and Caborca [C]);(2) Gondwanan provenance—three Paleozoic terranes accreted to North America during the latest Paleozoic Ouachita-Marathon orogeny (Coahuila, Maya, and Sierra Madre, all composite); and (3) Pacific provenance—seven Mesozoic (–Precambrian) terranes accreted to western Mexico in the Late Cretaceous (Alisitos, Vizcaino [C], Guerrero [C], Juarez, Mixteca [C], Oaxaca, and Xolapa). The nextcomprehensive terrane analysis of the whole of México appeared 10 years later by Sedlock et al. (1993) who outlined 16 terranes (Fig. 1B), 2 of North American provenance, 7 of Gondwanan prov1Email:

duncan@servidor.unam.mx

enance, and 7 of Pacific provenance, named after the various indigenous cultures of Mexico. Although the basic outlines of the terranes are similar to those of Campa and Coney (1983),the following changes occurred: (a) in the Gondwanan terranes, the Coahuila terrane and Sierra Madre terranes were each split into two, and the Mixteca and Oaxaca terrane were recognized as being of Gondwanan (rather than Pacific) provenance; (b) the Alisitos and Guerrero terranes were each split into two; and (c) the Vizcaino terrane was subdivided into four subterranes. Sedlock et al. (1993)went on to propose a tectonic evolution for Mexico. Since 1993, further studies have allowed many of the composite terranes to be subdivided. Thus the Guerrero composite terrane on mainland Mexico has been subdivided into five terranes (Centeno-García et al., 1993, 2000, 2003; Talavera-Mendoza and Suastegui, 2000; Freydier et al., 2000). The ~1 Ga basement of the Oaxaca terrane has been traced intothe Sierra Madre terrane, thereby giving rise to the Oaxaquia microcontinent (Ortega-Gutiérrez et al., 1995). Subsequently, Ortega-Gutiérrez et al. (1999) subdivided the Mixteca terrane into ophiolitic and sedimentary units that were inferred to have been juxtaposed in the Late Ordovician–Early Silurian. In 2001, Dickinson and Lawton classified the Mexican terranes in terms of eight, internally...