SHEDDING LIGHT ON THE BASE OF THE GREENLAND ICE SHEET: LUMINESCENCE DATING OF SUB-GLACIAL SEDIMENT FROM THE CAMP CENTURY ICE CORE, NW GREENLAND

The Camp Century ice core was collected in the 1960’s as part of a scientific cover operation during US military Cold War activities in Greenland. The base of this core contains 3.44 m of subglacial sediment with abundant plant remains and an intervening unit of silty ice, indicating at least two ice-free intervals in NW Greenland (Christ et al., 2021). While the ice core has been extensively studied, the basal sediments only received cursory description. Several new analytical methods were developed during decades of storage following collection, allowing details on the sediment age (luminescence and cosmogenic) and biological record (biomarkers, ancient DNA) to be determined from pristine samples. Pilot samples from the upper and lower 10 cm of the sub-glacial sediment suggest ice-free conditions within the last 1 Myr and an earlier ice-free interval sometime between 1.4 and 3.2 Ma based on cosmogenic burial dating (Christ et al., 2021). The goal of this collaborative international project is to understand when NW Greenland was last ice-free and the environmental conditions at that time.

My research applies luminescence dating to the sub-glacial sediment to provide greater resolution for the timing of ice-free intervals. Luminescence dating provides an age estimate for the last time sediment was exposed to sunlight and therefore provides insight into the timing and duration of ice-free intervals at Camp Century. Initial luminescence results from the 2021 pilot samples indicated that the basal sample was likely beyond the limit of luminescence dating (>1.5 Ma). However, the uppermost sample produced a finite age of 416 +/- 38 ka, indicating that Camp Century was ice free during MIS 11 (Christ et al., 2023). Initial results of my research focus on three sample intervals from the upper sediment package, one from the lower. These samples were further split into ~5 cm subsamples, which resulted in eight samples from the original core segments. These samples were sieved into three grain-size fractions and processed to isolate potassium feldspar. Samples were dated using post-infrared infrared-stimulated luminescence following multiple elevated temperatures (Li and Li, 2011). Luminescence samples are currently being analyzed. This poster summarizes my luminescence dating results and analysis of feldspar mineralogy.