GENERATING CONTINUOUS X-RAY FLUORESCENCE GEOCHEMISTRY FROM THE PALEOCENE TO THE MIOCENE IN SEDIMENT CORES FROM SANDTOWN, DELAWARE

In May and June 2023, the Delaware Geological Survey, in conjunction with researchers from the US Geological Survey and Rutgers University, drilled a 766 ft (233.5 m) corehole with 85% core recovery in Sandtown, Delaware (kb33-26) as part of a larger paleoclimate and groundwater resource project. Using the Minalyze continuous XRF core scanner at the Rutgers-IODP Core Repository, we generated a continuous geochemistry dataset for the Sandtown core. From this data we constructed concentration profiles for common elemental proxies, including Ca, Al, Ti, K, Fe, Zr, Si, Sr, Rb, Mn, Ba, and S, as well as several elemental ratios which have proved useful for paleoredox, sediment provenance, and grain size analyses such as Fe/Ca, Ti/Ca, Fe/K, and Si/Al. (Govin et al. 2012). We observe a definite variation in elemental composition with depth, especially as the sediment composition ranges between clay, silt, and glauconitic sand. We also observe a notable shift in composition that illustrates an inverse relationship between the concentration of Fe and Ti, Zr, Al, and to a lesser extent K and Sr, in the Eocene from 330 ft (100.58 m) to 470 ft (143.26 m) depth. The concentration of Fe is generally higher in sand-dominated intervals. The Al concentration is high during clay-dominated sections in the Miocene, and low in sand-dominated ones. We also observe notable spikes in the concentration of S around 340 ft (103.63 m) depth in the middle Eocene. At intervals with high amounts of shell material during the Miocene, we see increases in Ca concentration. The Si concentration is high above 150 ft (45.72 m) due to increased abundance of diatoms from 16.5 – 15.6 Ma. In conjunction with further sedimentary and stratigraphic analysis, these data will shed insight into depositional conditions in the Salisbury embayment from the late Paleocene through the Miocene, elucidating a critical period in the history of the Atlantic Coastal Plain.