Stratigraphy of the central sector of the Loncopué Trough: The Quaternary depocenter of the Huecú (Western sector of the Neuquén basin)

Abstract

The Huecú depocenter is located in the central sectorof the Loncopué trough in western Neuquén. This basin is composed of volcanic,volcaniclastic, fluvial and lacustrine deposits, younger than 1.6 Maencompassing postglacial and even historical sediments and lavas. During mostof its evolution, the Huecú depocenter has constituted a small closeddepression (pullapart basin) restricted to the Loncopué trough, a majorextensional retroarc basin in the Central and Patagonian Andes. This basin wasfed from the north since the beginning of its evolution by a series of bigamalgamated post-Pliocene stratovolcanoes located in the Mandolegüe Cordillera.The basin was also filled by fissural lava flows originated in the Agriocaldera located to the east grouped in the Escorial Basalt of 1.6 to 0.8 Ma.Polygenetic volcanic products form in the region big stratovolcanoes amongwhich the Trolón and Colorado volcanic centers were the most prominent. Thesecenters of Pleistocene age were highly eroded by the last glacial activity thataffected the region. Nearly at the end of the glacial period two fissuralvolcanic fields covered the Huecú depocenter corresponding to the Rankül-LomBasalt and preglacial Tres Hermanos basalts. Finally postglacial volcanic lavascovered most of the Huecú depocenter. These were grouped in the CerroArtillería Basalts and postglacial Tres Hermanos basalt, which have recurrentlydammed the main fluvial basins in the area. The fluvial and lacustrine depositsare represented by El Huecú and Mar Pequeño Formations.