Tropical/subtropical Upper Paleocene-Lower Eocene fluvial deposits in eastern central Patagonia, Chile (46 degrees 45 ' S)

A succession of quartz-rich fluvial sandstones and siltstones derived from a mainly rhyolitic source and minor metamorphic rocks, located to the west, represent the first Upper Paleocene-Early Eocene deposits described in Chi lean eastern central Patagonian Cordillera (46 degrees 45 'S). This unit, e xposed 25 km south of Chile Chico, south of lago General Carrera, is here d efined as the Ligorio Marquez Formation. It overlies with an angular unconf ormity Lower Cretaceous shallow marine sedimentary rocks (Cerro Colorado Fo rmation) and subaerial tuffs that have yielded K-Ar dates of 128, 125 and 1 23 Ma (Flamencos Tuffs, of the Divisadero Group). The Ligorio Marquez Forma tion includes flora indicative of a tropical/subtropical climate, and its d eposition took place during the initial part of the Late Paleocene-Early Eo cene Cenozoic optimum. The underlying Lower Cretaceous units exhibit foldin g and faulting, implying a pre-Paleocene-Lower Eocene contractional tectoni sm. Overlying Oligocene-Miocene marine and continental facies in the same a r ea exhibit thrusts and normal faults indicative of post-Lower Miocene con tractional tectonism. (C) 2000 Elsevier Science Ltd. All rights reserved.