Sandstone composition changes and paleocurrent reversal in the Upper Paleozoic and Triassic deposits of the Huaco area, western Paganzo Basin, west-central Argentina

Abstract

Sandstone detrital modes and paleocurrents in the Upper Paleozoic and Triassic deposits exposed near Huaco on the western sector of the Paganzo basin, western Argentina, reveal two distinctive petrofacies. A quartzofeldspathic petrofacies represented in the lacustrine and fluvial deposits of Carboniferous and early Permian age (Guandacol, Tupe and lower Patquía Formations) is characterized by a high content of monocrystalline quartz, low lithic content and high K-feldspar to total feldspar ratios. The fluvial facies of the lower Patquía grade vertically into eolian sandstones (upper Patquía Formation) which show a significant content of volcanic lithic fragments along with high proportions of monocrystalline quartz. This eolian succession is overlain by a volcaniclastic (lithofeldspathic) petrofacies represented by alluvial-fan and fluvial deposits of the late Permian to Triassic age (Cerro Morado and Cauquenes Formations). These sandstones are characteristic by high proportions of volcanic lithic fragments, plagioclase grains, low content of monocrystalline quartz and low K-feldspar to total feldspar ratios. This change in sandstone composition is accompanied by a reversal in paleocurrent patterns. The quartzofeldspathic petrofacies present in the Carboniferous and Lower Permian deposits show a general paleocurrent pattern from east to west with inferred cratonic provenances of plutonic and metamorphic composition. The volcaniclastic deposits indicate paleocurrents from west to east suggesting source areas associated with the magmatic arc developed on the Paleo-Pacific Gondwana margin during Permian and Triassic times.