CONICET | Buscador de Institutos y Recursos Humanos

The multiproxy analysis of a Lateglacial-Holocene sedimentary section located on theAtlantic coast of the Fuegian steppe offers a unique opportunity to study the evolution of thecoastal landscape in relation to past sea level and climate changes in the southern highlatitudes. Palynological, geochemical and diatomological analyses, together withcomplementary sedimentology and geomorphology data, were successful tools forreconstructing the vegetation history and palaeoenvironmental conditions in the Laguna LasVueltas (LLV) area. After ca. 19,000 cal yr BP, the sediments were subjected to subaerialexposition and oxidation processes linked to a low sea level. The Sr/Ba ratio as a paleosalinity geochemical parameter indicated variations in the water body level that would have affected the preservation of palynomorphs. The diatoms evidenced an ephemeral and brackishfreshwater body subject to desiccation processes under arid environmental conditions.Between ca. 11,600 and 8500 cal yr BP, a shrubby steppe vegetation, mainly composed ofAsteraceae subf. Asteroideae, spread over the coastal area along with a shallow freshwaterbody and the deposition of fine-grained sediments in low-energy environments, all indicative of low effective moisture and warm climate conditions. Between ca. 8500 and 8100 cal yr BP, salt carpet vegetation, dominated by Chenopodiaceae, developed around a coastal lagoon in response to the Holocene marine transgression. The record of dinocysts and geochemical data evidenced the seawater influence. Between ca. 8100 and 7000 cal yr BP, salt marshes colonized the coastal area. A coastal lagoon with a more restricted connection to the sea with slight freshwater input were inferred, linked to the beginning of the regression phase. After ca. 7000 cal yr BP, grassland vegetation and an open shrub stratum along with a shallow lake (pan), disconnected from the sea, were developed in relation to a regressive coast and a fall in the sea level. Fluctuations in the water level of the pan and changes in the physicalchemical conditions, as indicated by fluctuations in Mn/Fe, Ti/Ca, Rb/Sr, Ca, TIC and TOC, suggest sudden events of desiccation and flooding. Between ca. 4500 and 2000 cal yr BP a drier phase was evidenced by changes in vegetation, algal content and geochemistry of the pan. A grassland vegetation and a shallow lake with seasonal water level variations characterized the last 2000 years. Our results from LLV area match well with the Andean forest fluctuations and regional climatic conditions recorded from Tierra del Fuego and Chilean southwest.

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