Paleontology of Pennsylvanian transgressive deposits in northwestern Precordillera, San Juan province, Argentina

Abstract

In central-western Argentina, sedimentological and paleontological studies have identified changes in sea levels during the Pennsylvanian period. After the late Serpukhovian-early Bashkirian postglacial transgression, two main flooding events occurred. Among these, Pennsylvanian transgressions 1 and 2 are considered the most significant. New palynological samples recovered from the T1 transgression in Puesto Volc´an, western Precordillera (San Juan province) reveal the presence of the Raistrickia densa-Convolutispora muriornata (DM) Biozone. The palynofloras are characterized by the recognition of Ahrensisporites cristatus, Lundbladispora spp., Raistrickia densa, Spelaeotriletes ybertii, and monosaccate pollen grains. The composition of the assemblages includes some taeniate pollen grains suggesting their assignment to the Subzone B. A new orthoconic cephalopod was also identified in the same stratigraphic interval, which adds to the invertebrate faunal record and confirms the marine environment. Imprints of foliage of Fedekurtzia argentina complete the paleofloristic assemblage. A late Bashkirian-earliest Moscovian age is suggested according to the well constrained radiometric control of the palynostratigraphy in the region.