Middle Jurassic-Late Cretaceous Paleogeography of the Western Margin of the Neuquén Basin (34° 30′?36° S)

TAPIA, FELIPE; CHARRIER, REYNALDO; MUÑOZ, MARCIA; DANIELA ASTABURUAGA; FARÍAS, MARCELO

Opening and Closure of the Neuquén Basin in the Southern Andes

Springer International Publishing

Año: 2020; p. 269 - 301

U?Pb dating of detrital and igneous zircons from the retroarc deposits ofthe Neuquén Basin has shed light over the Mesozoic evolution of the western borderof South America, yet the coeval arc and forearc regions remain mostly indirectlycharacterized. Furthermore, recent paleogeographic reconstructions consider the arcand forearc regions as a tectonically stable and static region at least until Late Cretaceous.In this chapter, we aim to contribute to the Middle Jurassic-Late Cretaceouspaleogeographic reconstructions of the western margin of South America from awestern point of view integrating the coeval arc and forearc evolution, between 34°30 and 36° S. We focus here in the deposits exposed along the Chilean slope ofthe Principal Cordillera and use four new detrital zircon age data to determine theirages and main source areas. These ages are compared with 38 published U?Pb detritalzircon ages and integrated into a series of paleogeographic cross sections whichillustrate the Mesozoic evolution along the Southern Central Andes encompassingthe forearc, arc, and retroarc regions. Our data show that the arc and forearc regionswere active at least since the Middle Jurassic. Evidence for this tectonic activitycorresponds to the development of forearc basins in the Middle Jurassic and EarlyCretaceous times. New ages along the Chilean slope of the Andes allow suggestingan early beginning for the compressive period during the latest Early Cretaceous.The formation of a geographic barrier, as a consequence of the compressive regime,would explain the differences in the sediments provenance between western and easterndeposits during the latest Late Cretaceous. Finally, the almost complete record of Mesozoic ages in the detrital and volcanic deposits of the western slope of theSouthern Central Andes constitutes a counter-argument about the null or waningactivity proposed for the Middle Jurassic or Late Cretaceous from U?Pb detritalzircon analysis of the eastern Mesozoic deposits. Conversely, our data indicate acontinued activity of the arc-related volcanism and magmatism throughout all theMesozoic time.