PALYNOLOGICAL EVIDENCE FOR HOLOCENE PALEOENVIRONMENTAL CHANGES ON THE ATLANTIC COAST OF TIERRA DEL FUEGO (ARGENTINA): THE ARROYO GAMMA RECORD

Abstract

This study presents a paleoenvironmental reconstruction of the Atlantic coast of Tierra del Fuego based on the analysis of a 170-cm-thick sedimentary sequence exposed along the lower reach of Arroyo Gamma (AG, 53°27′46″ S, 68°05′21.2″ W). During the middle Holocene, this area likely constituted a bay that was subsequently sheltered from ocean wave action by the development of beach-ridge plains. Through an integrated approach combining palynological, sedimentological, and multivariate statistical analyses, two palynological zones were identified. AG-1 was characterized by the predominance of Chenopodiaceae, accompanied by Poaceae, Empetrum rubrum, freshwater algae, and scarce marine dinocysts, indicating the development of halophytic communities associated with tidal salt-marsh environments. The occurrence of fine-grained sediments and rhythmic stratification supports the interpretation of a low-energy setting corresponding to a transitional coastal system. AG-2 recorded an increase in Caryophyllaceae, Poaceae, Acaena, and Asteraceae, an assemblage comparable to the herbaceous communities that currently characterize the Fuegian steppe. Freshwater algae occurred throughout the sequence, indicating the recurrent presence of shallow water bodies. The transition from coastal environments dominated by halophytic vegetation and tidal influence to more continental conditions characterized by herbaceous steppe communities is consistent with paleoenvironmental and vegetation changes reconstructed from other coastal sequences in the region, providing further insights into the evolution of coastal systems in Southern Patagonia.