Middle to late Holocene environmental conditions inferred from paleosols at the perched dune in the Laguna Arturo, Fuegian steppe, southern Argentina

Abstract

In the present study, we carried out palynological (pollen, spores, fungal remains, and freshwater algae) and pedological analyses from three paleosols (Ps6, Ps7, and Ps8) that developed in the upper part of the Arturo perched dune deposits, in the periphery of the homonymous lake, and compared the results with modern palynological assemblages from the Fuegian steppe in southern Argentina. These proxies offer an exceptional opportunity to enhance our knowledge of environmental conditions during the Holocene in the southern high latitudes. Pollen spectra from the paleosols Ps6 (middle Holocene), Ps7 and Ps8 (late Holocene) were dominated by Asteraceae subf. Asteroideae undifferentiated, which suggests that herbaceous and/or shrub vegetation probably developed locally on the dune. The existence of herbivorous grazers is indicated by the record of ascospores of several coprophilous fungi (Coniochaeta cf. lignaria, cf. Delitschia pachylospora, cf. Schizothecium sp., Sordaria-type, Sporormiella-type). Most other fungal remains (Glomus, cf. Cryptendoxyla hypophloia, Microthyriaceae, Alternaria sp., Dictyosporium sp.) are likely associated with the presence of steppe vegetation communities. In general, the paleosols displayed a low degree of pedological development and in one of them (Ps7) there is evidence of the re-activation of eolian processes. Taken together, our palynological and pedological results, as well as sedimentological and geomorphological data, indicate that Ps6 developed under less humid conditions than the overlying paleosols, Ps7 and Ps8. The variations in moisture availability during soil-forming intervals could be related to shifts in the latitudinal position and/or strength of westerlies throughout the middle to late Holocene.