Landform assemblages in inner Kongsfjorden, Svalbard: evidence of recent glacial (surge) activity

Abstract

Swath bathymetry and chirp data have been used to investigate the submarine landform assemblages in inner Kongsfjorden, Svalbard, to reconstruct glacial dynamics during the Late Holocene. Multiple sets of landforms include two types of glacial lineations (groove-ridge features and small, drumlinoid ridges), terminal moraines and associated debris lobes, as well as small push moraines, and indicate repeated surge activity during the last 150 years for four of the five tidewater glaciers terminating in inner Kongsfjorden. Aside from confirming previously documented surges of Kronebreen in 1869, of Kongsvegen, in 1948, and of Blomstrandbreen in 1960, the local bathymetry also indicates a surge of Kongsbreen in 1897, a glacier that has so far been regarded as a non-surge type glacier. A conceptual model was developed to summarize the surge-induced landform assemblages in Kongsfjorden, and to compare them with other models from terrestrial and marine settings. Striking similarities exist between the Kongsfjorden model and landform assemblages documented for other Spitsbergen fjords. However, eskers and crevasse-fill ridges, the latter thought to be the only landform certainly indicative of glacier surges, lack in Kongsfjorden. Furthermore, the small, drumlinoid ridges inferred to be suggestive of the past ice flow direction in the study area seem to have more in common with glacial lineations generated by surging glaciers on land. The acoustic data was supplemented with two sediment cores from Kongsfjorden’s innermost basin. The reworked glacimarine deposits at the base of the more proximal core reflect proximal conditions, as they are part of a debris lobe that formed on the distal flank of the terminal moraine deposited during the 1948 surge of Kongsvegen. The stratified muds from the second core contain varying amounts of clasts and also occur on top of the debris lobe. They reveal a relatively distal glacimarine environment mainly influenced by suspension settling from turbid meltwater emanating from Kronebreen or Kongsvegen. Geochemical fluctuations indicate temporal variations in the sediment supply from the two glaciers after 1948. The few landforms in the outer parts of the study area suggest glacial activity unrelated to the glacier surges. Together with the landforms previously documented from outer Kongsfjorden and its adjacent trough (Kongsfjordrenna), the mega-scale glacial lineations in the outer part of the study area indicate part of a landform assemblage deposited from a fast-flowing ice stream during the Last Glacial Maximum.