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

VICTOR A. RAMOS; MAXIMILIANO NAIPAUER

Growth of the Southern Andes

Springer Verlag

Lugar: Londres; Año: 2016; p. 33 - 61

The Neuquén Basin constitutes a key site to investigate how the patternof detrital zircon age varies through time in different tectonic regimes. Here weanalyze the U?Pb zircon age database published for the Southern Central Andes. Inthe early Mesozoic (rift stage) the source regions were locally and strongly influencedby the active volcanism coeval with the extensional tectonic activity. The riftrelief associated with the synrift stage lasted until the first marine transgressioncorresponding to the Los Molles Formation. The source regions in the retroarcsetting (sag stage) are variable and showed reversal provenance. In the Middle andLate Jurassic the magmatic arc became the most important source, but in the EarlyCretaceous 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 basement linked 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 discriminationdiagram 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.