Changes in source areas at Neuquén Basin: Mesozoic evolution and tectonic setting based on U-Pb ages on zircons

MAXIMILIANO NAIPAUER; VICTOR A. RAMOS

Growth of the Southern Andes

Springer

Año: 2016; p. 33 - 62

The Neuquén Basin constitutes a key site to investigate how the pattern of detrital zircon age varies through time in different tectonic regimes. Here we analyze the U?Pb zircon age database published for the Southern Central Andes. In the early Mesozoic (rift stage) the source regions were locally and strongly influenced by the active volcanism coeval with the extensional tectonic activity. The rift relief associated with the synrift stage lasted until the first marine transgression corresponding to the Los Molles Formation. The source regions in the retroarc setting (sag stage) are variable and showed reversal provenance. In the Middle and Late Jurassic the magmatic arc became the most important source, but in the Early Cretaceous eastern cratonic regions were the main source areas of sediment contribution. The reversal of the provenance pattern can be either explained by the base-level fall or by a period of exhumation of the Sierras Pampeanas basementlinked to generation of rift systems. The source regions in the Late Cretaceous (foreland stage) indicate an uplift of a mountain chain and exhumation along the Andean magmatic arc; although younger and distal units showed that a peripheral bulge would be growing in the eastern cratonic sector. Cawood?s tectonic discrimination diagram is tested as a useful tool in the Southern Central Andes. However, it is necessary to consider more complex settings taking into account the relative positions of the magmatic arc and the orogenic front through time.