Nuevos aportes a la palinología, cronología y paleoambiente de la Precordillera Occidental de Argentina:

formaciones El Planchón, Codo (Devónico) y El Ratón (Mississippiano)

Abstract

“New contributions to the palynology, chronology and palaeoenvironment of the Western Precordillera of Argentina: El Planchón, Codo (Devonian) and El Ratón (Missis- sippian) formations”. New palynological data from the Devonian and the Mississippian rocks at the Calingasta area, south of the San Juan river, Western Precordillera of Argentina are presented. The palynological assemblage obtained from the Codo Formation (Devonian) is mainly composed of acritarchs ( Lophosphaeridium spp., Cerastum sp.), and scarce and poorly pre- served spores of the genus Apiculiretusispora and Cyclogranisporites . The assemblage is ten- tatively attributed to the Givetian-Frasnian based on the age of the genus Cerastum Turner. The El Ratón Formation (Mississippian) yielded an assemblage composed of spores dominated by the genus Cristatisporites , and diagnostic spores such as Anapiculatisporites amplus Pla- yford and Powis, Anapiculatisporites hystricosus Playford, Colatisporites decorus (Bharadwaj and Venkatachala) Williams en Neves, Gueinn, Clayton, Ioannides, Neville and Kruszewska, Ver- rucosisporites morulatus Potonié and Kremp emend. Smith and Butterworth and Verruco- sisporites papulosus Hacquebard that allow to asigned it to the early Visean and thus to correlate it with the middle part of the Malimán Formation. The extension of the hiatus between Codo and El Ratón formations is estimated based on the palynological results, spanning part of the Late Devonian and the Tournaisian. The Upper Member of the El Panchón Formation (Devonian) is palynologically barren. New sedimentological information here obtained, suggests a shallow marine palaeoenvironment.