Characterization of the 1966 Camp Century Subglacial Sediment Core

📖 The Scoop

In 1966, drilling at Camp Century recovered 3.44 meters of subglacial material from beneath 1350 meters of ice. While prior analysis of this subglacial material showed that the core includes glacial sediment, ice, and sediment deposited during an interglacial, it had never been thoroughly studied. To better characterize this material, we analyzed 26 of the 30 samples remaining in the archive. We performed a multi-scale analysis including X-ray diffraction, micro-computed tomography, and scanning electron microscopy to delineate stratigraphic units and assign facies based on inferred depositional processes. At the macro-scale, quantitative X-ray diffraction revealed quartz and feldspar dominance and little variation in relative mineral abundance between samples. Meso-scale evaluation of the frozen sediments using micro-computed tomography scans showed clear variations in the stratigraphy of the core characterized by the presence of layering, grading, and sorting structures. Micro-scale grain size and shape analysis, conducted using scanning electron microscopy, showed an abundance of fine-grained materials in the lower portion of the core and no correlation between grain shape parameters and depth. These multiscale data define 5 distinct stratigraphic units within the core based on sedimentary process and K-means clustering analysis support this proposed unit delineation. Our observations suggest that interglacial warming first uncovered basal diamicton. It is covered by remnants of basal ice or firn (unit 1, unit 2) after which ice-free conditions established a depositional environment that began with colluvial slumping (unit 3) and transitioned to a small fluvial system of increasing energy (units 4-5). Together, analyses on the Camp Century subglacial sediment indicate a diverse stratigraphy preserved below the ice and capture episodes of glaciated and deglaciated conditions in northwestern Greenland. Our physical, geochemical, and mineralogic analyses reveal a history of deposition, weathering, and sediment transport preserved under the ice and show the promise of subglacial materials to increase our knowledge of past ice sheet behavior over time.

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