'Geometry and kinematics of the Nuncios detachment fold complex: implications for lithotectonics in northeastern Mexico'

摘要

Using recent geologic mapping combined withdigital elevation data, aerial photo interpretation, andcross section balancing, we describe the threedimensional(3-D) geometry and kinematics of theNuncios Fold Complex in the Monterrey Salient ofnortheastern Mexico. This map-scale, evaporite-coreddetachment fold structure involves Upper Jurassicthrough Cretaceous rocks deformed during theLaramide orogeny and comprises two westwardplunging anticlines and an intervening, eastwardplunging syncline. Seven balanced cross sections anda 3-D model of this north vergent structure documentsubstantial along-strike variations in both foldgeometry and detachment depth, suggesting that 3-Dflow of the detachment layer may have occurredduring folding. Comparison of folds in the MonterreySalient with those in the neighboring Parras Basinsuggests that the latter south vergent folds root to ashallower detachment. We suggest that northwardtransport of the Monterrey Salient folds on the lowerevaporite detachment may have been inhibited by athick sequence of foreland basin rocks in thenortheastern Parras and southern La Popa basins andthat the smaller, south verging folds formed where thelower detachment was abandoned and slip wastransferred to the shallower detachment, forming atriangle zone at the front of the Sierra Madre orogenicwedge.