The Neoproterozoic Valdres Group - depositional conditions and stratigraphical developments in the Mellane and Grønsennknippa sections, Valdres, Southern Norway

Abstract

one diamictite unit. The latter is possibly correlative to the diamictite recognised in the Valdres Group at Mellane and may represent a tillite correlatable to the Moelv Tillite (Marinoan glaciation). The Mellane section is more dominated by sandstones and subordinate conglomerates than those at Grønsennknippa. Mineralogical composition and field observations of the Grønsennknippa and Mellane sections indicate relatively short transport distances of the texturally immature sediments. The petrography also reflects a later metamorphic phase (varying greenschist facies) that overprints the original mineralogy. Comparison between the Valdres Group at Mellane and Grønsennknippa sections indicates that the Grønsennknippa succession exhibits an originally more immature mineralogical and textural signature than those at Mellane. The Grønsennknippa sections are more feldspar-rich and dominated by coarse-grained detritus. This may reflect different positions with respect to the source area/basin margin. In this study, the Valdres Group at Grønsennknippa and Mellane is compared with selected fluvial/alluvial formations of the Hedmark Basin, revealing comparable depositional environments and stratigraphic developments. The occurrence of possible tillites at stratigraphical levels comparable to the Moelv Tillite are of particular interest. The petrographical composition and heavy mineral distribution support comparable sediment sources from mainly Sveconorwegian formations in both the Valdres and Hedmark basins.