Structure and tectonic evolution of hybrid thick- and thin-skinned systems in the Malargüe fold-thrust belt, Neuquén basin, Argentina

Abstract

Andean Cenozoic shortening within the Malargüe fold-thrust belt ofwest-central Argentina has been dominated by basement faults largely influenced by pre-existing Mesozoic rift structures of the Neuquén basin system. The basement contractional structures, however, diverge from many classic inversion geometries in that they formed large hanging-wall anticlines with steeply dipping frontal forelimbs and structural relief in the order of several kilometres. During Cenozoic E-W shortening, the reactivated basement faults propagated into cover strata, feeding slip to shallowthrust systems thatwere later carried in piggyback fashion above newly formed basement structures, yielding complex thickand thin-skinned structural relationships. In the adjacent foreland, Cenozoic clastic strata recorded the broad kinematic evolution of the fold-thrust belt. We present a set of structural cross-sections supported by regional surface maps and industry seismic and well data, along with new stratigraphic information for associated Neogene synorogenic foreland basin fill. Collectively, these results provide important constraints on the temporal and geometric linkages between the deeper basement faults (including both reactivated and newly formed structures) and shallow thin-skinned thrust systems, which, in turn, offer insights for the understanding of hydrocarbon systems in the actively explored Neuquén region of the Andean orogenic belt.