| Summary: | Abstract: A series of sediment gravity- and box-cores was collected in Kongsfjorden, Svalbard during the summer of 2009 as part of the Svalbard Research Experience for Undergraduates (REU) project, which aims to characterize the modern sedimentary environment proximal to the Kronebreen-Kongsvegen tidewater glacier margin. This study serves to generate baseline data for future assessment of the local polythermal glacial response to climate change, and to contribute to the framework by which proximal polythermal glaciomarine environments are interpreted in the sediment record. Sedimentary facies identified within the cores, collected between 300 – 900m from the ice face and spanning the ice margin, serve as proxies of modern meltwater and depositional processes at the tidewater margin. Sedimentary facies are characterized, with increasing resolution, through x-radiograph, thin section, and grain size analyses and are considered in relation to local fjord floor morphology and sediment trap data. The lithofacies established in this study account for the dominant depositional mechanisms in the fjord, including turbidity currents, suspension settling, and iceberg rafting. These lithofacies relate well with those found in temperate fjords, suggesting that these two glacial regimes may be indistinguishable in the rock record. Ubiquitous evidence of sediment reworking from turbidity currents in all cores suggests a predominance of underconsolidated mud along the slope of the submarine outwash fan and surrounding moraines. Cyclically laminated fine sand/silt and clay couplets, interpreted to have settled from suspension, are also preserved at varying intervals throughout some cores. Preliminary comparison with sediment trap data suggests that such cyclicty may correspond with the semidiurnal tidal cycle, such that the vertical accumulation of two couplets represents daily sediment accumulation rates. Daily sedimentation rates have hence been preliminarily estimated to be 2 mm/d in a region 600m from the northern ice front, but more elaborate sediment trap data is needed to better constrain this estimate. Ultimately, this study provides an archive of the depositional environment proximal to Kronebreen Kongsvegen for the benefit of future studies addressing the effects of climate change on this subpolar glaciomarine environment.
|
|---|