Identifying Downslope Transport From Sr/Ca and Mg/Ca Ratios on the West Florida Shelf Using X-Ray Fluorescence

The objective of this study is to investigate what the use of Sr/Ca and Mg/Ca ratios can tell us about sediment deposition from downslope transport from the West Florida Shelf to the deep sea. Magnesium and Strontium are component elements of aragonite biomineralogical precipitation, primarily found in the biogenic components of shallow water organisms, therefore tracking these elements gives insight to when these shallow water carbonates are found in these deeper waters due to downslope sediment transport. This was done by analysing X-ray fluorescence data previously taken from core GC-22 by the NOZ lab in the Netherlands at 1mm increments and constructing a core log. The results show noticeable spikes in the Mg/Ca ratio around the 15-30 cm and the 35-45 cm area of the core, corresponding to finer sediment texture and lower carbonate composition. Carbon-14 dating was done along these spikes, tracing the sediment in these spikes, as shown in the core log. In addition, Sr/Ca ratios stayed relatively consistent throughout the core, with two short but drastic spikes within the 55-65 cm region. This downslope depositional transport can be traced back to many causes, such as the site's proximity to carbonate mass wasting zones, tectonic movement (micro earthquakes), large scale environmental changes in salinity and temperature, and sea level change as well as climate events such as drastic temperature changes in the late pleistocene epoch, which happens to match up with the Carbon-14 dating from the older Mg/Ca spike. This work is significant because it provides a framework for investigating large-scale changes in sediment transport, helping scientists understand these events further.

For more information email: hduarte@eckerd.edu