Neogene erosion of the Andean Cordillera in the flat-slab segment as indicated by petrography and whole-rock geochemistry from the Manantiales Foreland Basin (32°–32°30′S)

Abstract

The Miocene Manantiales Foreland Basin is defined as a thick succession of sedimentary rocks belonging to the Chinches Formation in the Frontal Cordillera between 32 degrees S and 32 degrees 30 degrees S, located over the flat-slab segment of the Andean Cordillera. It has been interpreted as a foreland basin that mainly received contributions from several mountain ranges such as the Principal Cordillera and Frontal Cordillera to the west. In this paper, we present a detailed study of its provenance based on the petrography and whole-rock geochemistry of sedimentary rocks from the Chinches Formation. Our results indicate that the Manantiales Basin was fed by igneous provinces in the hinterland that contain sub-alkaline intermediate rocks (andesitic) and acidic rocks (dacitic to rhyodacitic and granitic) arranged in a clear stratigraphic progression. These signatures may be assigned to Cenozoic rocks (Farellones Formation) in the Principal Cordillera and Permo-Triassic (Choiyoi Group) in the Frontal Cordillera. In contrast to a previous result, we found a continuous geochemical trend in the Chinches Formation between ca. 19 and 10 Ma opposing the idea of a tectonic repetition in the sedimentary succession. (C) 2014 Elsevier B.V. All rights reserved.