Kettle holes, ‘dead-ice’ topography and eskers on a lake floor in Telemark, southern Norway

Abstract

Hummocky terrain in deglaciated areas is often attributed to ‘dead-ice’ activity, that is, a depositional environment produced by the presence and melt-out of large blocks of stagnant ice (Gravenor & Kupsch 1959; Eyles et al. 1999). Morphologically similar dead-ice terrain is found on the floor of Lake Bandak in southern Norway, a former fjord now isolated from the sea, where a stagnant glacier terminated during the Late Weichselian deglaciation. Lake Bandak is an east–west-orientated lake with a length of c. 26 km, an average width of c. 1 km, and an area of 26.4 km2 (Fig. 1). It is situated 72 m above sea level some 85 km inland from the outer coast (Fig. 1b). The marine limit is 120–130 m above present sea level due to postglacial isostatic rebound (Bergstrom 1999), implying that the glacier which filled the valley at the Last Glacial Maximum terminated in a fjord during deglaciation. Both the glacial ice divide and present watershed lie west of the lake, indicating flow from west–east. The lake is deepest (200–300 m) and relatively flat from Lardal and eastwards with steep lateral slopes (Fig. 1a), whereas the western part is shallower (typically <100 m deep). Seismic and backscatter data suggest that …