CAN SEA ICE-RAFTED DEBRIS BE DISTINGUISHED FROM ICEBERG-RAFTED DEBRIS BASED ON GRAIN SURFACE FEATURES? ANALYSIS OF QUARTZ GRAINS FROM MODERN ARCTIC OCEAN SEA ICE FLOES

The analysis of surface textures of quartz grains in continental deposits and marine deposits has successfully been used as a method to infer regional glacial histories and glacial dynamics. In glaciomarine settings such as the Arctic Ocean, where sea ice is an additional transport mechanism, the need to differentiate between glacial (iceberg) and sea ice transported sediments becomes important. Glacial ice and sea ice have different formation and transport histories and have different roles in climate-system feedbacks. The potential for using a set of quartz grain surface features as an indirect indicator for not only iceberg transport, but also sea ice transport in the Arctic, stems from initial work by Dunhill (1998). Based on analysis of samples from modern Arctic sea ice floes and from piston cores she concluded that iceberg and sea ice transported sediment can be differentiated by the abundance or absence of specific groups of grain surface features. Her study remains the primary work characterizing surface textures of sea ice rafted debris, although several other recent studies have applied this methodology in paleo-IRD analyses. The purpose of our research is to conduct an independent analysis of the surface textures in modern Arctic sea ice samples and thereby confirm, modify, or refute Dunhill’s conclusions. Our study is based on 171 quartz grains from 9 modern Arctic Ocean sea ice samples. Each grain was systematically observed using an SEM, and the results were recorded following a hybrid checklist approach. Preliminary statistical analyses show a dominance of grains that are medium relief, contain breakage blocks, evidence of silica dissolution, and a finely layered, ubiquitous microtextures that we refer to as “microlayering.” These results differ from Dunhill’s at two levels: breakage blocks were previously used as in indicator of iceberg transport, although we see these as common in sea ice IRD, and microlayering has not been reported previously. Principle component analysis indicates that there are three end member types of grains with different grain shapes and textures. Sample sources/site locations appear to have no direct impact on the texture of the grains. These end member types may reflect differences in original mineral formation conditions and/or transport prior to sea ice drift.