Recurrent volcanic activity recorded in araucarian wood from the Lower Cretaceous Springhill Formation, Patagonia, Argentina: Palaeoenvironmental interpretations

DEL FUEYO, GEORGINA M.; CARRIZO, MARTÍN A.; DANIEL G. POIRÉ; LAFUENTE DIAZ, MAITEN A.

ACTA PALAEONTOLOGICA POLONICA

INST PALEOBIOLOGII PAN

Lugar: Varsovia; Año: 2021 vol. 66 p. 231 - 253

0567-7920

This paper describes a petrified trunk collected from a conglomeratebed of the Springhill Formation (Berriasian?Valanginian) in the Estancia ElÁlamo locality, Santa Cruz Province, Argentina. The fossil trunk is classifiedwithin the ubiquitous genus Agathoxylon, but the wood anatomy shows a closeaffinity to that of Araucariaceae. This Patagonian wood has a distinctcombination of anatomical characteristics unique among all known species fromthe Jurassic and Cretaceous of Western Gondwana allowing to diagnose a new fossiltaxon A. mendezii sp. nov. Sedimentological and megafloristic proxies of the SpringhillFormation suggest that A. mendezii sp. nov. grew under a warm and wet climate, whichindicates a subtropical to temperate palaeoenvironment. However, the largenumber of frost rings in the earlywood of this araucarian tree suggests thatthe palaeoenvironment at Estancia El Álamo was subjected to recurrentdisturbances, most likely caused by regional continuous volcanic activityoriginating from volcanoes located far away to the west. This activity wouldhave produced periodic stratospheric veils that promoted rapid decreases in surfaceair temperature; the wood response to such stressful conditions would have beenthe formation of numerous (at least five) frost rings. Although recurrenteruptions in Patagonia during the Early Cretaceous are well recorded, thisstudy is the first to register eruptions recorded in the coniferous wooddescribed herein.