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 is an excellent site to investigatehow the pattern of detrital zircon age varies through the time in differenttectonic regimes. Here we analyze the U-Pb zircon age database published forthis sector of the Andes. In the Early Mesozoic (rift stage) the source regionswere locally and strongly influenced by the active volcanism coeval withextensional tectonic activity. The rift relief lasted until the first marinetransgression of the Los Molles Formation. The source regions in the retroarcsetting (sag stage) are variable and showed reversal provenance. In the Middleand Late Jurassic the magmatic arc became the most important source, but in theEarly Cretaceous eastern cratonic regions were the main source areas ofsediment contribution. The reversal of the provenance pattern can be explainedby the base-level fall or by a period of exhumation of the Sierra Pampeanaslinked to generation of rift systems. The source regions in the Late Cretaceous(foreland stage) indicate a mountain chain uplift and exhumation along the Andean magmatic arc; although younger anddistal units showed that a peripheral bulge is growing in the eastern cratonicsector. Cawood?s tectonic discrimination diagram may be an useful tool to successfullyapply in the southern Central Andes. However, it is necessary to consider morecomplex settings with the relative positions to the magmatic arc and to theorogenic front.