Camp Century Subglacial Sediments
Project
ID: 000583289
Public
Basal materials in ice cores contain information about paleoclimate conditions, glacial processes, and the timing of past ice-free intervals all of which contribute toward understanding ice-sheet stability and contribution to sea-level rise in a warming climate. Only a few ice cores have been drilled through ice sheets to the underlying sediment and bedrock, producing limited material for analysis. The Camp Century ice core, which was drilled in northwest Greenland from 1960-1966 CE, recovered 3.44 meters of sub-glacial sediment that was not thoroughly studied at the time. Here, we document the scientific history of the Camp Century sub-glacial sediment, and present our core-cutting, sub-sampling, and processing methodology for this unique archive. We documented, described, and then cut each frozen archived sample (n=26). We saved an archival half and then cut the working half into eight oriented sub-samples under controlled temperature and light conditions for varied physical, geochemical, isotopic, sedimentological, and biological analyses. Our approach maximized sample usage for multi-proxy analysis, minimized contamination, and preserved material for future analyses of this legacy sample material. Grain size, bulk density, sedimentary features, ice content, pore ice pH and conductivity, and magnetic susceptibility measurements suggest that the basal sediments contain five stratigraphic units (from bottom to top): a diamicton with sub-horizontal ice lenses (Unit 1); vertically-fractured ice bearing few dispersed fine sediments (< 20% in mass) (Unit 2); a graded bed of pebbles to very fine sand in an icy matrix (Unit 3); bedded very fine to fine sand (Unit 4); and bedded medium to coarse sand (Unit 5). Plant macrofossil remains are present in all samples and most abundant in Units 3 and 4; insect remains were present in some samples (Units 1, 3, and 5). Camp Century basal units are comprised of multiple facies that represent different depositional environments in sub-glacial and ice-free conditions. Our approach provides an example for future studies of ice-core basal sediments because it includes intentional planning of core sub-sampling, processing methodologies, and archiving strategies to optimize the collection of paleoclimate and glacial process data from rare sediment archives of limited size. Our work benefited from an archive that was carefully curated and preserved allowing for the application of techniques not available when the core was recovered nearly six decades earlier. Preserving uncontaminated core material for future analytical capabilities is an important consideration for rare archive materials such as these from Camp Century.