INSIGHT INTO CHANGING CLIMATE AND SOURCE AREAS: AN INVESTIGATION OF MARINE ARCTIC CLAY SEDIMENTS

The IODP Arctic Coring Expedition (ACEX) recovered the longest cored sequence (>400 m) from the Arctic Ocean when they drilled sites along the Lomonosov Ridge (87^◦N) in 2004. The sediments recovered provided excellent opportunities for Arctic Cenozoic paleoceanographic investigations, including the reconstruction of past climate and sediment provenance. Our research focuses on Middle Eocene (45.6 to 47 Ma) sediments from ACEX. This stratigraphic interval is of interest because it captures the early stages of the Arctic’s transition from warmer to cooler climates and initial ice growth. The purpose of this research is to use the type and abundance of clay minerals found within these cores to infer the paleoclimatic conditions in this region at the time of deposition, as well as clay provenance which may indicate ice or current paleotransport directions. Clay mineralogy can be used to identify source areas, since different bedrock will produce different weathering products. Clays are also useful as a climate indicator since weathering is climate dependent (e.g. wet vs. dry conditions, warm vs. cold conditions). To determine the clay mineralogy and track relative abundance fluctuations over time, 70 samples are analyzed using X-ray diffraction (XRD). Sediment samples are ultrasonically disaggregated and centrifuged to separate the clay size fraction. Oriented smear slides are made from each sample for air dried and glycolated X-ray diffraction analysis. Preliminary results indicate an abundance of expansive smectite, along with lesser amounts of kaolinite, illite and perhaps mixed-layer clays. This may indicate cooler, dryer climates as smectite is considered to be a less weathered clay than kaolonite. It also suggests transport from volcanic source areas. Initial results suggest that there is a decrease in clay input up core. Further research will include a more detailed examination of the stratigraphic compositional variations, and comparison of our data with results from other Arctic paleoclimate and provenance studies.