Concentrations of uranium (U), thorium (Th), and potassium (K) in geological materials provide insight into many important lithological characteristics and geologic processes. In marine sediment, they can aid in identifying clay compositions, depositional environments, and diagenetic processes. They can also yield information about the alteration and heat production of rocks (Ketcham 1996; Barr et al., 2002; Revillon et al., 2002; Brady et al., 2006; Bartetzko, 2008). Measurements of the concentrations of these elements in geological materials are relatively straightforward in shore-based laboratories. Rapidly determining their abundance within cores of sedimentary and igneous rock sequences onboard a research vessel is a more challenging but potentially very useful method to non-destructively and quickly provide important geochemical information about the concentrations of U, Th, and K within the sequences being cored.