A MULTI-PROXY ANALYSIS OF A RED CLAY CORE FROM THE NORTH PACIFIC ABYSSAL PLAIN TO RECONSTRUCT DEPOSITIONAL PROCESSES AND PALEO-WINDS

Sediment in the North Pacific Ocean is dominantly red clay, yet with low sedimentation rates and a lack of biogenic carbonate, research in this region is limited. A review of red clays (Glasby, 1991) concludes that most clays and silt in the central Pacific were wind transported from central Asia; this is supplemented by authigenic precipitation of ferromanganese nodules and some clay minerals. In 2016, the STEMSEAS expedition traveled from San Diego to Honolulu on the R/V Oceanus and collected sediment cores from the North Pacific Ocean abyssal plain. While the expedition’s purpose was to provide students with on-board hands-on research experience, it created the opportunity for students to conduct research on the cores post-cruise. This course-based research focused on the 1.78 m long core from Site 2 (4458 m water depth). The goals were to: 1) describe the cored sedimentary sequence using multiple lines of observation, 2) use grain size to evaluate processes of sediment transport as eolian or hemipelagic, and 3) infer potential variations in paleo-wind strength and sediment provenance over time.

Observations were made using smear slides, SEM, XRD, XRF, and a Laser Diffraction Particle Size Analyzer at JMU. Magnetic susceptibility and color reflectance data were collected at the USGS in Reston, Virginia. Grain size analysis showed little variation downcore, with a mean grain diameter of 3-4 µm. This distribution pattern mostly resembles Rea and Hovan’s (1995) eolian model, suggesting transport to this site was consistently eolian-dominated, with slight variations in wind strength based proxies for sorting. Illite is the dominant clay at Site 2, suggesting high rates of terrestrial input compared to authigenic processes. Three sections where smectite dominates may be from shifts in authigenic processes versus eolian input, or changes in provenance. Similar downcore variations in MS and major elements suggest changes in paleo-wind strength, although authigenic processes may play a role as well. Without age data for these results, there cannot yet be direct correlations to specific paleoclimate events. Using published linear sedimentation rates for other abyssal plain sites in the North Pacific Ocean we hypothesize possible age models.