A new record of Carboniferous fossil woods with primary structures from Western Gondwana, Calingasta-Uspallata Basin, Argentina

Abstract

Three permineralized fossil woods from the Sierra de Barreal in San Juan Province, Argentina are reported. The stems were recovered from the Tres Saltos Formation (Pennsylvanian), which comprises 135 m of red shales, sandstones, and conglomerates deposited in fluvial, transitional, and coastal environments. Although the pycnoxylic woods are mainly poorly preserved anatomy, one of them displays fine details of the anatomy. The latter has preservated a nonseptate parenchymatic pith and primary xylem attached. Tracheids of the primary xylem have helical thickenings. The secondary xylem has distinct growth ring boundaries, exclusively uniseriate rays with nodular thickenings on their horizontal and end walls, and crossfields with 1–6 simple pits. Tracheids of the secondary xylem have uni-biseriate araucarian pits in radial walls. The anatomical features allow it to be assigned to the fossil-species Abietopitys petriellae. This finding is significant as it represents the third worldwide record of the fossil-genus Abietopitys in Carboniferous successions and the first detailed study of wood with preserved anatomy from the Terminal Glacial Stage of the Calingasta-Uspallata Basin. Additionally, it is proposed that bietopitys probably had some climatic tolerance as suggested by its presence in both glacial and post-glacial successions of the Gondwana paleocontinent.