Holocene environmental changes in Dicksonfjorden, west Spitsbergen, Svalbard

Abstract

Fjord systems in the high latitudes host a complex suite of depositional processes controlled by climate changes, glaciers and sea ice, river networks, and sea-level changes. This study aim to parse the physical and chemical properties of the Holocene sediments in Dicksonfjorden, a fjord system unaffected by tidewater glaciers, to reconstruct the environmental development in the fjord including shifts in sources of detrital sediment and organic matter, fluctuations in sea-ice rafting, as well as falling relative sea-level in response to the post-glacial isostatic rebound. Multi-proxy analyses of two sediment cores from Dicksonfjorden were performed to reconstruct Holocene environmental conditions in this northern tributary of the Isfjorden fjord system, the largest fjord system on Svalbard. While sediments were derived from Paleozoic siliciclastic and carbonate bedrocks occurring at the head and sides of the fjord, their relative contributions were controlled by falling relative sea-level and the resultant progradation of the main stream and delta systems closer to the core sites. Deposition of clasts from sea-ice rafting persisted throughout 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. The latter can be related to regional climate cooling and the prograding river systems prompted by the low sea-level. Reduced ice rafting from c. 3 ka suggests enhanced formation of 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, can account for the increased marine organic matter produced in the outer Dicksonfjorden. In the absence of tidewater glaciers, the palaeoenvironmental conditions documented in this fjord are in accordance with the fjords hosting tidewater glaciers in western Spitsbergen, reflecting climate and oceanographic changes.