Paleoenvironmental conditions in the Western Strait of Magellanes (53°S) during the last deglaciation and Holocene

This study presents paleoenvironmental proxies for the last 16.000 cal. years B.P. as determined in two sediment cores retrieved from the Western Strait of Magellanes. Overall goal was to determine the biogenic and terrigenous sediment fluxes and their relationship to paleoenvironmental changes. The chronology is based on well-dated tephra layers from the region and AMS 14C ages of marine shells and marco plant remnants. The variability of sediment input during the late glacial and deglaciation period is related to the global warming trend and rapid deglaciation in the Southern Andes. The maximum in magnetic susceptibility reflects the retreat of small mountain glaciers in the Western Strait of Magellanes. The time between 16.000 to 14.000 cal. years B.P. is characterised by maximum terrigenous and minimum biogenous accumulation rates. Marine transgression to the Western Strait of Magellanes occurred between around 14.000 to 12.000 cal. years B.P. and is characterised by strongly increased biogenic carbonate content and corresponding biogenic carbonate accumulation rates. The laminated interval in the investigated core Tamar is a local event indicating initial deglaciation in the region and the formation of a proglacial lake, followed several thousand years later by the invasion of salt water as sea level rose. The period between around 11.000 to 6.000 cal. years B.P. is characterised by high organic matter and low terrigenous accumulation rates, and minor chemical variations. This reflects a climate optimum with a well established Magellanic rainforest and minor climate fluctuations. Evidence for pronounced Neoglacial conditions, as reported from some glaciers in the Andes (40° to 50°S) and the South Atlantic between 5.000 and 1.000 cal. years B.P., have not been found in the fjord sediment records of the Andean transect. These cores also show some extreme precipitation events during the Neoglacial time and probably more unstable and colder climatic conditions. High sedimentation rates, high amounts of mineralogical fractions and relatively high TOC accumulation rates in sediment core PALM reflect a southward migration of the westerlies and subsequently higher precipitation. The Little Ice Age (LIA) of the last millennium is not evident in the investigated sediment records.