Chapter 60. Evidence for late Neoproterozoic glaciation in the central Scandinavian Caledonides

Abstract: The La°ngmarkberg Formation (Fm). rests on either the Neoproterozoic rift-related Risba¨ck Group or Palaeoproterozoic basement
in central Scandinavia. It is always succeeded in stratigraphy by the marine Ga¨rdsjo¨n Fm. The La°ngmarkberg Fm. is a thin, generally
less than 50-m-thick, discontinuous, but persistent unit, primarily in the Lower Allochthon; subordinately also in the Autochthon,
and Middle Allochthon of the central Scandinavian Caledonides. The formation is composed of a lower diamictite and an upper laminated,
lonestone-bearing mudstone.
Criteria supporting the glaciogenic origin of the formation are (i) a large regional extension of the formation (.5000 km2) and (ii) its
fixed position in the regional stratigraphy, (iii) the ‘tillite-like’ appearance of the lower part of the formation, (iv) the lonestone-bearing
mudstone in the upper part, (v) the presence of striated clasts and (vi) striated pavement. It is interpreted as having formed during one
single glacial–deglacial cycle.
Information on chemostratigraphy and realistic geochronology from this region is missing. ... mehrThe La°ngmarkberg Fm. has commonly
been correlated with the Moelv Fm. in southern Norway and the Mortensnes Fm. in northernmost Norway. The Lower Allochthon in
this region also contains an older, potentially glacially influenced diamictite unit at the base of the Risba¨ck Group, which is also
briefly discussed.