Abstract
The Taxco region, 160 km south of Mexico City, is one of the oldest mining districts in North America. Structurally the Taxco study area is located in the Guerrero Branch of the Mexican Thrust Belt. The regional stratigraphic column consists of four distinct units: (1) pre-Cretaceous (pre-Barremian) low grade metamorphic, greenschist rocks (Taxco Schist and Roca Verde Taxco Viejo); (2) late Barremian-Albian platform carbonates of the Achuizotla-Morelos formations and their basinal equivalents the Pochote-Xochicalco formations; (3) Late Cretaceous deeper water carbonates and clastics of the Cuautla and Mexcala formations; (4) Paleocene and younger plutons, volcanics and volcaniclastic conglomerates, which intrude or unconformably cover the older units. Two regional unconformities divide these strata into 3 tectonostratigraphic sequences. These are: (1) Basement (Tierra Caliente Complex); (2) late Lower-Upper Cretaceous marine, sequence and (3) Tertiary continental sequence. Previous geologic maps of the study area show normal faulting, with localized thrusting and large outcrops of metamorphic rocks. The boundary between the allegedly allocthonous Guerrero terrane and Mixteca terrane was also mapped in the area. My interpretations of 1:50,000 Landsat TM images and field observations show that: (1) large scale thrusting is the predominant structural element and the key to understanding Laramide deformation in the region; (2) about 95% of the area previously mapped as metamorphic rocks is Late Cretaceous marine strata and (3) there is no Laramide terrane boundary separating the Mixteca and Guerrero terranes. I concluded that: (a) previous tectonic reconstructions that relied upon the distribution of metamorphic rocks as depicted in previous maps should be revised; (b) Laramide deformation was accommodated primarily by east-vergent large scale thrusting and folding. These results were integrated with additional regional stratigraphic and tectonic data, both published and unpublished to constrain a new model of the Mesozoic tectonic evolution of Southern Mexico.