Update of the Pennsylvanian palynostratigraphy from central-western Argentina

Abstract

The Raistrickia densa-Convolutispora muriornata (DM) palynological assemblage biozone formerly proposed twenty years ago for Pennsylvanian successions of central-western Argentina is at present represented in fifty stratigraphic sections. The advances in the studies, with detailed paleoenvironmental data and sampling with precise provenance through complete successions, allow the range of several species to be constrained. The biohorizons and composition of the three subzones (A, B, and C) are updated according to a revision of 400 palynological samples, and a new proposal of subdivision is presented. Of stratigraphic importance in the characterization of the DM Biozone are the presence of Lundbladispora braziliensis and radial monosaccate pollen at the lowermost boundary and the appearance of Pakhapites fusus and Vittatina costabilis at the uppermost biohorizon. Subzone B is recognized by the occurrence of Spelaeotriletes ybertii and bisaccate taeniate pollen, while Subzone C is distinguished by the first occurrence of Raistrickia cephalata and increase of taeniate pollen (including Vittatina). Variations in diversity are discussed concerning paleoenvironments, and floristic changes, as well as a comparison with other Gondwanan assemblages is presented. Absolute datings indicate that the age of the Subzone A is constrained within the late Serpukhovian-early Bashkirian, the Subzone B to the late Bashkirian-earliest Moscovian, and the Subzone C to the Moscovian-Kasimovian? The accurate U–Pb zircon CA-TIMS calibration for the DM Biozone allows constraining the stratigraphic range of its species and the correlation with other Gondwanan regions.