2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 137-8
Presentation Time: 9:00 AM-6:30 PM


GUTIÉRREZ-NAVARRO, Rodrigo, Institute of Geology, Universidad Nacional Autónoma de México, Av. Universidad #3000, C. U., Coyoacán, México City, 04510, Mexico, BARBOZA-GUDIÑO, José Rafael, Instituto de Geologia, Universidad Autónoma de San Luis Potosí, Manuel Nava 5, zona universitaria, San Luis Potosí, Juarez 20, Villa Hidalgo S.L.P, San Luis Potosí, 78240, Mexico and FITZ-DIAZ, Elisa, Instituto de Geologia, UNAM, Av. Universidad #3000, C. U., Coyoacan, Mexico, D. F., 04510, Mexico, rodrigo.gutierrezn@gmail.com

The Sierra de Catorce (SC, Range of Catorce) includes some of the westernmost exposures of the Mexican Fold-Thrust Belt (MFTB) and at the same time is one of the easternmost Basin and Range features (horst) in central Mexico. This physiographic feature has a maximum elevation of 3 km above the sea level and resulted from Late Cretaceous-Paleogene contraction and subsequent Neogene extension affecting this region. Rocks exposed across the SC include Triassic clastic units, unconformably covered by a succession of Jurassic volcaniclastic rocks, in turn covered by fluvial deposits, which are overlaid by Late Jurassic-Cretaceous carbonates, and intruded by Eocene quartz monzonitic dikes. Along an E-W cross-section, the SC shows an anticlinorium like structure cut by normal faults dipping to the valleys on both sides.

The Triassic units show ductile E-W shortening as suggested by a pervasive, continuous, planar, N-S trending cleavage developed at very low-grade metamorphic conditions. Such first generation of cleavage is associated with folds with vertical axes. The Jurassic units also show a pervasive, sub vertical pencil cleavage associated with spaced open folds, which is also trending N-S, and were formed in the anchizone. The Jurassic units’ cleavage is disrupted by a regional detachment localized at the base of the carbonate succession (Zuloaga Fm.), which separates cleavage dominated shortening in the Jurassic clastic units from fold-dominated shortening in the upper Cretaceous carbonates. Above the detachment zone, folds have axial planes oriented N20E 60 SW with a dominant vergence towards the East.

All shortening directions are nearly co-axial. The Triassic/Jurassic unconformity indicates there are at least two phases of deformation in the rocks of SC, and one of them is probably Triassic-Early Jurassic in age. However, ages of younger structures are not well established. We applied Ar-Ar illite dating to folds and to the detachment zone in order to determine the age of shortening affecting the Cretaceous carbonates. We also use apatite and zircon U-Th/He thermochronology to test if the last important exhumation of SC occurred during the formation of the MFTB (Late Cretaceous-Paleogene) or during Basin and Range extension in the region (Oligocene).