NJG84-2-04
2004
Late Quaternary, cryoplanation of rock surfaces in lacustrine environments in the Bergen area, Norway
84
2
pp. 125-137
82-92394-13-3

Relatively horizontal and smooth rock surfaces bordering lakes 65-150 m a.s.l. in the relatively mountainous Bergen area are described. The surfaces, 1- 4 km2 in size and up to 1.5 km wide are developed in strongly foliated metamorphic Proterozoic and Paleozoic bedrock ranging in composition from granitic to gabbroic. The detailed topography of the bog-covered rock surfaces has been mapped by various methods: map surveys, probing and levelling, profiling with seismic refraction and ground penetrating radar (GPR) as well as direct levelling of the rock platforms around the lakes. The formation of the rock surfaces is compared to the recent formation of an up to 20 m wide rock platform along one of the lakes.Alternating air temperature inversions in the lake basin and heavy precipitation during milder periods (NAO) are thought to be responsible for frequent freeze/thaw fluctuations as well as an oscillating lake level facilitating frost weathering. The rock surfaces are thought to have formed during Weichselian interstadials by frost weathering (cryoplanation) along the shores of former lakes and rivers. Implications for the formation of the 30 km wide Norwegian strandflat in similar rocks just north of this area are discussed.

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