Last glacial–interglacial transition and early Holocene vegetation reconstruction: Pollen and plant macrofossil analysis from a Subantarctic forest sequence at 49°S.

To understand plant community succession; paleoenvironmental history, and to contribute to the regional knowledge base for the eastern area of the Southern Patagonian Icefield (SPIF), we present a paleoenvironmental reconstruction from the last glacial–interglacial transition to the early Holocene (18,500 to 9000 cal yr BP). This research was based on pollen and plant macrofossil analyses together with lithostratigraphy characterization from a sequence obtained at the Mallín Ciprés wetland (49°S; Southern Santa Cruz, Patagonia, Argentina). Between 18,500 and 16,000 cal yr BP, cold and arid conditions prevailed in the study area with dwarf-shrub communities dominated by Ephedra, likely under weakened Southern Westerly Winds (SWW). From 16,000 to 12,800 cal yr BP, a shift to grass-dwarf-shrub steppes occurred, along with increased moisture and expansion of Nothofagus, likely driven by stronger SWW contemporaneous with the Antarctic Cold Reversal. Between 12,800 and 9600 cal yr BP, we observe a western grass steppe with Nothofagus forest expansion, indicating warmer but relatively arid conditions under weaker westerly winds. Pilgerodendron began to establish at 10,500 cal yr BP, marking the onset of the wetland's modern dynamics. After 9600 cal yr BP, the significant spread of Nothofagus forest reflects increased moisture during early Holocene warming. This study addresses a critical gap in paleoecological knowledge of the eastern SPIF, providing insights into the influence of SWW variability, temperature fluctuations, and glacial dynamics on vegetation development between 48° and 52°S.