Holocene aeolian dune-paleosol record at the Fuegian steppe: assessment of interglacial climate and environmental variability at the southernmost tip of Patagonia (Isla Grande de Tierra del Fuego)

Abstract

Late Quaternary aeolian dune-paleosol sedimentary successions in perched dunes at the Fuegian steppe (northern Isla Grande de Tierra del Fuego, Patagonia) offer valuable insights into the Holocene climatic and environmental variability of southernmost South America, on the Southern Hemisphere westerly winds belt. Using morphological and geochemical data from eight paleosols interbedded in the aeolian units of a perched dune related to the ephemeral, shallow Laguna Arturo lake (53◦43′ S, 68◦18′ W), we assessed Holocene soil formation. The morphological characteristics and CIA index of the paleosols indicate poor to moderate weathering, with very limited hydrolysis and leaching mostly due to the subhumid climatic regime of the Fuegian steppe. Despite this,pedogenesis led to the formation of discrete paleosols after the Late Glacial. Oxidation is a conspicuous process in the Lateglacial-Early Holocene and early Middle Holocene paleosols of the succession. The poor pedological structure of paleosols from the late Middle Holocene, along with the aeolian deposits rate of sedimentation, records more likely arid conditions in southern Patagonia, a pattern consistent with other multi-proxy records in the region. The Late Holocene paleosols record slightly higher CIA indices and characteristics compatible with a higher moisture in the environment compared to the Middle Holocene. The studied dune-paleosol successiondocuments relatively short soil formation intervals, possibly linked to increased humidity in the Fuegian steppe due to short-term climate variability since around 12,800 cal yrs. BP, related to the dynamics of the Southern Hemisphere westerly winds.