CASADIO Silvio Alberto
Multiproxy provenance analysis of Lower to Upper Cretaceous synorogenic deposits in the Southern Andes (34-35°S): evidence of coeval volcanism during the onset of the Andean orogeny
GÓMEZ, RICARDO; GALETTO, ANTONELLA; ARZADÚN, GUADALUPE; TUNIK, MAISA; CASADIO, SILVIO; PARADA, MARTIN; LOTHARI, LUCAS
CRETACEOUS RESEARCH (PRINT)
ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD
The combination of detrital low-temperature thermochronology with previous U-Pb geochronology, petrological, stratigraphic and sedimentological analyses, has been a valuable approach to constrain the provenance of non-marine Lower to Upper Cretaceous synorogenic deposits in the northern Neuquén Basin. This work focuses on the study of the Diamante Formation, a fluvial succession that represents the first synorogenic erosion products of the Andean foreland basin at 34-35°S. The results indicate that the deposition of Diamante Formation occurred simultaneously with the existence of an active western volcanic arc during the onset of the foreland basin in the latest Early Cretaceous. The facies associations evidence the transition between the back-arc and the foreland basin stages and the inception of fluvial sedimentation in the foredeep depozone. Petrographic analyses, together with changes in the paleocurrents and the record of limestone clasts suggest a regional source shift. Apatite fission track analyses (AFT) of a sample collected from the lower part of the Diamante Formation indicate an Albian central cooling age. This sample also evidence a remarkable presence of angular apatite and zircon crystals with subordinated rounded and subangular grains. Zircon fission-track analyses (ZFT) of a sample from the upper part of the Diamante Formation yield two discrete populations of cooling ages, both reflecting source-cooling during the Late Jurassic (~161 Ma) and the Permian (~265 Ma). Finally, a comparison between the AFT and the U-Pb maximum depositional zircon-ages of the same sample of the Diamante Formation reveal a short lag time (ca. 3 ma), likely related to the rapid magmatic cooling of a coeval volcanic source at ~110 Ma (Albian).