TECTONIC EVOLUTION OF THE FAULTS AND FOLDS PROVINCE AND THE MEXICAN VOLCANIC BELT IN SOUTH CENTRAL HIDALGO, MEXICO

In south central Hidalgo, Mexico a 0.6-0.8km deep by ca. 11 km long northwest-southeast trending canyon exposes Cretaceous marine sediments that record Laramidic to Plio-Quaternary deformational events. The sedimentary rocks form part of the Folds and Faults Province and are covered by volcanic rocks of the mid portion of the Trans-Mexican Volcanic Belt. The sedimentary rocks underwent a NE-SW oriented chevron folding event (F1) followed by a subsequent almost coaxial compression of the sequence that tightened the pre-existing chevron folds (F1-late). Also associated with F1-late, a set of coaxial folds affected chevron fold limbs and is characterized by short wave-lengths, subhorizontal axial planes, and no related cleavage. Younger fault-bend folds and associated kinks affected F1 and F-late. The detachment planes dip to the southwest and indicate a direction of transport to the northeast. The youngest thrust-faults juxtaposed blocks of Cretaceous sediments against Tertiary volcanoclastic deposits.

We interpret the newly identified deformational sequence as consistent with a tectonic evolution in which a major Laramidic, NE-SW (present day) shortening event folded the Cretaceous marine rocks, and was followed by overthrusting that generated fault-bend folds and ended in northeast directed thrust faulting. The younger over-thrust faulting event postdates Tertiary volcanoclastic deposits suggesting that is probably associated with Quaternary faulting.