USING 210PBXS TO TRACK DOWNSLOPE TRANSPORT OF SEDIMENTS IN THE SOUTHERN GULF OF MEXICO: A “PULSE INDEX” AND MASS ACCUMULATION RATE APPROACH

Sediment cores collected throughout the Southern Gulf of Mexico (SGoM) in 2015 were used to evaluate downslope transport of sediments which may have associated contaminants and compared to the Northern Gulf of Mexico (NGoM). Their main difference is the SGoM has less terrestrial sediment influence unlike the NGoM’s input from the Mississippi River. Short-lived radioisotope (SLR) analysis of cores for 210-Pb excess (210Pbxs) provided downcore 210Pbxs profiles, which were used to determine age dates and mass accumulation rates (MAR) using the Constant Rate of Supply model. A“Pulse Index” value for each site was determined using profile shape for the number of episodic sedimentation “pulse” events, the percentage of sediments accumulated in each event, and the length of each pulse. This “Pulse Index” provides a relative evaluation of how consistent/stable vs episodic (downslope transport events) sediment accumulation is at each site for the past 100 years. The NGoM has high index values, likely due to Mississippi River input with higher potential for downslope transport of contaminants associated with the 2010 Deepwater Horizon oil spill. The SGOM has lower index values, besides the IXTOC site, with lower potential for downslope transport of contaminated sediments from the 1979 IXTOC oil spill. This indicates more stable sediment accumulation patterns in the SGoM and lower potential for downslope transport of contaminants. Future research can help in understanding the use of SLRs to find downslope transport and recognize patterns in sediment movement throughout the GoM.

Presentation Preference: Poster

Primary Presenter: Selby Shipley, Eckerd College (sashipley@eckerd.edu)

Authors:

Selby Shipley, Eckerd College  (sashipley@eckerd.edu)

Rebekka Larson, Eckerd College  (larsonra@eckerd.edu)

Patrick Schwing, Eckerd College  (schwinpt@eckerd.edu)

Gregg Brooks, Eckerd College  (brooksgr@eckerd.edu)