This award supported Expedition 379T aboard the D/V JOIDES Resolution to collect sediment records (up to 100 meters below seafloor) from the Chilean Margin in July and August of 2019. Eight sites were cored during the expedition, recovering a total of 2232 m of sediment cores from a range of water depths that can be used to investigate links between oceanographic changes at the northern margin of the Antarctic Circumpolar Current and climate variability on the South American continent over the past few glacial-interglacial cycles. The 34-member shipboard science party was composed of six senior scientists, 7 postdoctoral scholars, and fifteen graduate students. Education was an important component of the expedition; all members of the science-party were trained in and carried out the shipboard analyses, and contributed to the interpretations and report writing. The expedition report detailing all shipboard operations, data collection, and site summaries has been published and can be accessed here: https://zenodo.org/record/5553428#.Y9BOKezMIUQ. Sediment cores are archived at the Lamont Doherty Earth Observatory. Shipboard data are archived by the JOIDES Resolution Science Operator and can be accessed via the LIMS Online Report Portal (https://web.iodp.tamu.edu/LORE). 

Post-cruise analyses, including radiocarbon, benthic foraminiferal oxygen isotopes, and bulk sediment geochemistry analyzed via x-ray fluorescence core scanning were conducted to improve core stratigraphies at six of the eight sites. Notably, these data confirm a roughly constant sedimentation rate of 6 meters per thousand years across the Holocene at Site J1004. A splice with nearby Site J1002 extends the record to 25 thousand years before present, providing one of the highest resolution records of climate over the last glacial termination and Holocene from the Southern Hemisphere, rivaling the resolution of ice cores over this time frame. For a longer-term perspective, Site J1001 spans the last 900 thousand years, providing multiple examples of glacial-interglacial cycles along the Chilean Margin, including the Eemian time period, which was a primary target for the expedition. Initial interpretations suggest Site J1007 also captures this critical time interval and at much higher temporal resolution.

 The collected sediment cores and their initial characterization have and will continue to support science objectives that advance knowledge of climate variability and sediment-water interactions along the Chilean Margin. These efforts, thus far led by graduate students and postdoctoral scholars that sailed on the expedition, form the basis of two PhD theses, four conference presentations, and two published papers, with more on the way. Notable findings include (1) the first detection of solar cycles in southern westerly wind migrations over the entire Holocene (Riechelson et al., in prep), (2) a 6,000 year lead of Patagonia Ice Sheet glaciation and deglaciation relative to Northern Hemisphere ice sheets, which suggests a Southern Hemisphere pacing of global glaciation (Sproson et al. in prep), (3) the utility of sediment green-blue ratio as an indicator of sediment biogenic silica (Chen et al., 2022), and (4) extreme heterogeneity in fluid migration and diagenesis in the Chilean Margin accretionary complex (Clementi et al., 2022, Clementi et al., in prep). Elemental and isotope measurements show that the down-core freshening observed in several of the sites is not primarily due to dissociation of methane clathrates, which are abundant in this region, but caused by other processes including dilution with meteoric water submarine discharge and diagenetic dehydration of clays, with varying intensities at each site.  

Last Modified: 01/30/2023
Modified by: Samantha C Bova