Holocene environmental changes in Dicksonfjorden, west Spitsbergen, Svalbard

Abstract

Multi-proxy analyses of two sediment cores from Dicksonfjorden were performed to reconstruct Holocene environmental conditions in this northern tributary of Isfjorden, the largest fjord system on Svalbard. Factors affecting the depositional processes include shifts in sources of inorganic and organic sediments, ice rafting, and regional glacio-isostatic rebound. Sediments were derived from Palaeozoic siliciclastic and carbonate bedrocks occurring at the fjord head and sides, respectively. Their relative contributions were controlled by falling relative sea-level and the resulting progradation of the major stream and delta systems closer to the core sites. Deposition of clasts from sea ice rafting persisted throughout the most of the Holocene. Following a period of low, but continuous, clast fluxes (~ c. 11 ？ 7 ka), ice rafting was most intensive between c. 7 and 3 ka. It can be related to extensive seasonal sea ice formation caused by regional climate cooling. The prograding deltas also provided coarse sediments. Reduced ice rafting from c. 3 ka suggests enhanced formation of more shorefast and/or permanent sea ice, suppressing sea ice rafting in the fjord, in response to the cool climate and reduced heat flux from Atlantic Water. Episodic inflow of Atlantic Water, however, as well as low turbidity of surface water, can account for a higher amount of marine organic matter produced in the outer fjord. The sedimentary record in Dicksonfjorden, where tidewater glaciers are absent, reflects similar regional climate and oceanographic variations as reconstructed in fjords on western Spitsbergen that are influenced by tidewater glaciers.