A new palynological assemblage (Carboniferous) from the Chacoparaná Basin, Western Gondwana, and revision of the biostratigraphic scheme

Abstract

A new palynozone for the upper Serpukhovian–Bashkirian (uppermost Mississippian–lower Pennsylvanian) strata of the Chacoparaná Basin (Argentina) is formally proposed based on palynological assemblages from the Santiago Temple YCF.CO1, YCF.CO2 and YCF.CO3 boreholes, drilled in Córdoba province. Thirty samples were analyzed and 222 palynomorph species identified. The Anapiculatisporites concinnus (Ac) Assemblage Zone is present only in the Santiago Temple boreholes and is divided into two subzones (lower and upper). The Ac Assemblage Zone has been identified in the lower part of the Ordóñez Formation, which is characterized by the presence of diamictites that would have been deposited in glaciolacustrine and glaciomarine environments. The Ac Assemblage Zone is correlated with subzones A and B of the Raistrickia densa–Convolutispora muriornata Zone defined in the western basins of Argentina. The known zones in the Chacoparaná Basin succession are redefined based on a review of borehole information, and the new zone is incorporated. Palynostratigraphically, the basin is divided into the Anapiculatisporites concinnus Assemblage Zone (upper Serpukhovian–lower Bashkirian), Potonieisporites–Lundbladispora Interval Zone (late Bashkirian–Gzhelian), Cristatisporites Interval Zone (late Gzhelian–early Kungurian) and Striatites (Kungurian–early Roadian) Assemblage Zone.