ABSTRACT This study presents the first apatite fission-track results from the Tolimán area, which is located in the western portion of the southern Sierra Madre Oriental, central Mexico. In total, six rock samples from different lithostratigraphic units were dated, adding new results to the thermochronological data set of the Sierra de los Cuarzos–San Joaquín–Tamazunchale transect in the Mexican fold-and-thrust belt. The apatite fission-track ages vary from 84 ± 4 Ma to 52 ± 2 Ma, indicating that the main denudation period of the Tolimán area lasted until the Eocene. Combining our results with previous geological data, we suggest that the western part of the southern Sierra Madre Oriental was uplifted and undergoing erosion during the whole period of development of the Campanian–Ypresian Mexican orogenic system. Therefore, the Tolimán area may be considered as one of the source areas from which clastic materials of the Campanian–Maastrichtian Méndez and Paleocene–Eocene Velasco and Chicontepec Formations were partially derived. Older cooling ages recording the latest Aptian accretion of the Guerrero terrane with the Mexican continental interior were not detected in samples from the Tolimán area.

ABSTRACT Two main tectonic scenarios have been proposed for the area corresponding to the Guerrero terrane in western Mexico. The first model suggests that the Guerrero terrane was an allochthonous volcanic arc developed over oceanic substrate, which was accreted to nuclear Mexico. The second tectonic model proposes that the Guerrero terrane was a para-autochthonous volcanic arc developed over continental crust, which was rifted during the extensional phase of the Arperos back-arc basin and then tectonically attached to nuclear Mexico. Based on U-Pb geochronology and Hf isotope analyses of detrital zircon grains extracted from Mesozoic sedimentary successions of the Guerrero terrane and western nuclear Mexico, this study provides new evidence to support the interpretation that the Late Jurassic–Early Cretaceous Guerrero terrane was built above a pre–Late Jurassic continentally sourced basement. Hf isotopic signatures of detrital zircon from Late Jurassic–Early Cretaceous sedimentary rocks of the Guerrero terrane range from –14 to +13 and display depleted mantle model ages (T DMc , using a mean crustal value of 176 Lu/ 177 Hf = 0.015) between ca. 2.0 and 0.3 Ga, indicating provenance from both pre–Late Jurassic basement and juvenile crustal components. The most juvenile magmas were formed during the earliest Cretaceous extensional phase, which resulted in the formation of the Arperos basin. Additionally, the negative ε Hf ( t ) values are consistent with recycling of Proterozoic and Paleozoic continental materials in Mesozoic magmas.