New findings in the Permian xyloflora of Carapacha Formation (Argentina)

Abstract

The Carapacha Formation consists of two members: the Calencó (lower) and the Urre-Lauquen (upper), dated as Permian based on its glossopterid flora. The formation outcrops in La Pampa Province, near the locality of Puelches, with sediments of continental origin, fluvio-lacustrine in type. This study describes two gymnosperm woods species. One, from the Calencó Member, is a Cordaitalean assigned to Scleromedulloxylon aveyronense found in the Permian of Aveyron, France, characterized by having a heterocellular pith with islands of sclerenchymatic cells and unorganized lacunae in transverse section. The other specimen, from the Urre-Lauquen Member, is a conifer of uncertain affinity, Zalesskioxylon uniseriatum, previously reported from the Raniganj (India), Yaguarí (Uruguay), and Tacuary (Paraguay) formations. Both woods exhibit secondary xylem features typical of Paleozoic gymnosperms, particularly concerning the radial system and the arrangement of pits in the tracheid walls. These xylological records confirm that the Carapacha Formation comprises another Permian sedimentological sequences that contain woods with diaphragm-solenoid pith such as the taxa found in the Melo (Uruguay), the Río Bonito, and the Irati (Brazil), the White Band (Africa), the Barakar, and the Raniganj (India) formations. This palaeofloristic association is part of the Australoxylon xylotaphoflora characteristic of the Gondwanan Permian. Finally, this study allows us to infer that the environmental conditions in this formation were warm with low humidity and seasonally dry.