Benthic responses to warming and ice retreat on the Chilean Margin during the Last Glacial Period

Marine terminating ice sheets and glaciers influence the chemical, biological and physical dynamics of adjacent marine systems. For example, changes in ice extent affect sedimentation rates along glaciated coasts, as well as drive shifts in marine productivity linked to stratification and nutrient delivery. These changes can affect the redox conditions and storage of organic carbon in shelf sediments. Therefore, glacial retreat due to modern climate warming could potentially have major impacts on marine productivity, sedimentation and carbon cycling in the Southern Ocean and other high latitude areas. To study the effects of warming on diagenetic processes and sedimentation dynamics, we analyzed core samples from IODP Expedition 383 Site U1542, collected close to the southern Chilean Margin, a region of rapid sedimentation rates that is linked to the Southern Ocean via the Cape Horn Current and the Drake Passage. This site provides a high-resolution record of changes at the western maximum extent of the Patagonia Ice Sheet (PIS), which was dominant in this setting during the last glacial period. Preliminary results from this Site indicate 7 distinct intervals of short-term warming events (1-5 kyr) between 20 and 60 kyr. We analyzed samples spanning these warming events for total organic carbon, grain size, and Fe minerology, and compared results with records of trace metal (e.g., Mn and Ni) contents from X-ray fluorescence (XRF) analysis. Preliminary results indicate that when the PIS retreated during short-term warming events, the redox conditions in the sediment shifted, becoming more reducing as indicated by trace metal contents and Fe minerology, and the organic carbon content in the sediment increased. In addition, larger grain sizes during warm periods suggest a possible decrease in fine glacial flour input with the retreat of the ice sheet. Overall, this study disentangles signals reflecting diagenetic, benthic redox and sedimentological changes driven by changes in glacial input. This research ultimately aims to improve our understanding of how a marginal marine system responded to climatic warming and ice sheet loss, serving as a potential analog for future loss of modern ice sheets.