Characterization of the 1966 Camp Century Sub-Glacial Core: A Multiscale Analysis

Abstract

Abstract. In 1966, drilling at Camp Century, Greenland, recovered 3.44 meters of sub-glacial material from beneath 1350 meters of ice. Although prior analysis of this material showed that the core includes glacial sediment, ice, and sediment deposited during an interglacial, the sub-glacial material had never been thoroughly studied. To better characterize this material, we analyzed 26 of the 30 core 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 that quartz and feldspar dominated the sediment and that there was insignificant variation in relative mineral abundance between samples. Meso-scale evaluation of the frozen material using micro-computed tomography scans showed clear variations in the stratigraphy of the core characterized by the presence of bedding, grading, and sorting. Micro-scale grain size and shape analysis, conducted using scanning electron microscopy, showed an abundance of fine-grained materials in the lower part of the core and no correspondence between grain shape parameters and sedimentary structures. These multiscale data define 5 distinct stratigraphic units within the core based on sedimentary process; K-means clustering analysis supports this proposed unit delineation. Our observations suggest that ice retreat uncovered the Camp Century region exposing basal till, covered with a remnant of basal ice or firn (Units 1 and 2). Continued ice-free conditions led to till disruption by liquid water causing a slump deposit (Unit 3) and the development of a small fluvial system of increasing energy up core (Units 4–5). Analysis of the Camp Century sub-glacial material indicates a diverse stratigraphy preserved below the ice that recorded 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 sub-glacial materials to increase our knowledge of past ice sheet behavior over time.