Late Quaternary palaeoenvironmental and palaeogeographic evolution in the Fuego river valley, central Tierra del Fuego, southern South America

Abstract

Palaeoenvironmental and palaeogeographic evolution were reconstructed from a Late Quaternary sedimentary section at Fuego river valley (53° 58.602′ S - 67° 32.230′ W) on the Atlantic coast of the forest-steppe ecotone, central Tierra del Fuego, southern Argentina. This multiproxy study integrates geomorphology, palynology (sporomorphs and non-pollen palynomorphs-NPPs), sedimentology, tephrochronology, and geochemical parameters (organic matter content). During Marine Isotopic Stage 5e, the shoreline configuration resembled the present but was positioned 13–15 m above the current mean sea level. Subsequently, fluvial erosion processes, associated with a drop in base-level, shaped the coastal landscape, creating canyons and narrow valleys. In the Early Holocene (approximately 10,000 cal yr BP), the development of salt carpet vegetation dominated by Chenopodiaceae, along with the presence of marine palynomorphs, suggests that the Fuego River valley was inundated during the Holocene marine transgression driven by post-glacial sea-level rise. A subsequent interval characterized by low palynomorph content is attributed to taphonomic processes that impeded palynomorph preservation, hindering the detailed reconstruction of environmental conditions during the mid-Holocene maximum marine transgression. In the Late Holocene, after 1200 cal yr BP, the development of grassland (Poaceae) and herbaceous (Caryophyllaceae) vegetation was associated with alluvial environments, while the presence of freshwater aquatic palynomorphs suggests shallow freshwater conditions near the study area.