A GEOMORPHIC AND SEDIMENTOLOGICAL STUDY OF THE PERIGLACIAL PROCESSES AND ENVIRONMENTS, VARDEBORGSLETTA, WESTERN SPITSBERGEN, SVALBARD

Periglacial environments in today’s polar regions are highly susceptible to current and future climate change. In arctic regions, climate has warmed significantly as compared to mid-latitude regions. This study investigates geomorphological and sedimentological evidence of late Holocene changes in Vardeborgsletta, a unique high arctic periglacial landscape situated in karst terrain in western Spitsbergen, Svalbard. Fieldwork was conducted in the summer of 2012 and included geomorphological mapping and investigations of the current status of the active layer of the permafrost and karst hydrologic processes. In addition, two sediment cores were recovered from two lakes, informally named Lake 4 and Lake 7, within this periglacial terrain. Laboratory analyses of the cores shed light on recent changes in climate and in the karst hydrologic system. In Lake 4, field season measurements and geomorphic evidence (raised shorelines, outlet channels and exposed lake floor interbedded with fan-delta deposits) illustrate the dynamic nature of karst and periglacial processes. In Lake 7, the lack of similar geomorphic evidence indicates that lake level has remained stable in recent times.

Laboratory analysis conducted on two surface cores (up to 35cm) from Lake 4 and 7 include loss-on-ignition, bulk density, grain size analysis, and plutonium (^239+240Pu) and radiocarbon age determination. In the Lake 7 core, the lower 20 cm interval is a massive organic-rich silt (10 to 18% LOI) overlain by a 15 cm unit (5 to 10% LOI) comprised of alternating minerogenic clay and silt layers, 1 mm to 1 cm thick. In the Lake 4 core, the upper 18 cm of the core consists of a laminated clayey silt unit. This banded unit overlies a massive silt-rich unit. A 2 meter-deep soil pit excavated at the margin of the delta fan on a section of former lake floor exposes alternating clay-rich and silty sand layers, similar to the Lake 4 core stratigraphy. The sediment core and pit stratigraphy likely reflect periodic (seasonal) input from snowmelt and slope processes as well as episodic fluctuations in lake level.

The development of a clear understanding of the modern and recent processes shaping the periglacial landscape in the Vardeborgsletta terrain will provide insight to the response of the high arctic periglacial environments to future climate change.