Sedimentological studies in the late Precambrian and lower Cambrian rocks of east Finnmark

• Main Author: Banks, N
• Format: Thesis
• Language: unknown
• Published: 2017
• Subjects: Breivik; Finnmark; Varanger
• Online Access: https://ora.ox.ac.uk/objects/uuid:c5d28a02-a9d9-4d5d-a8e7-e5af03eb072b

In eastern Finnmark a northward thickening wedge of late Precambrian and Cambro-Ordovician sedimentary rocks extends 200km from east to west, with a maximum north- south width of approximately 50km. The succession lies unconformably upon Precambrian crystalline basement, which crops out to the south. The maximum thickness is between 4,000m and 5,000m with shallow water sandstones and shales predominating. Two distinct tillite formations occur, beneath each of which there is an unconformity shown only by local downcutting and slight regional discordance. Otherwise the succession is conformable, deposition having occurred in a gently subsiding basin. Structural deformation is very slight in the east but increases towards Laksefjord in the west where the rocks are strongly folded. In the far west of the area two distinct units are present, the Gaissa Nappe consisting of folded Precambrian sandstones and, underlying this, the autochthonous undeformed Dividal Group (previously the "Hyolithus Zone") of late Precambrian and Lower Cambrian age. This study is concerned with the six members which form almost the entire succession from the top of the Upper Tillite to the top of the Lower Cambrian. These members are the Innerelv and Manndraperelv Members of the Stappogiedde Formation, the Lower and Upper Members of the Breivik Formation and the Lower and Upper Members of the Duolbasgaissa Formation The lower three members are found over a wide area and can be correlated with the Members of the Dividal Group in the extreme southwest of the region. Their maximum thickness of about 775m is found on the Digermul Peninsula and gradual thinning occurs towards the southwest, the thickness of the Dividal Group being about 230m. It is possible that some slight thinning also occurs on the Varanger Peninsula to the southeast of the Digermul Peninsula. The upper three members are confined to the Digermul Peninsula and have a maximum thickness of about 900m. The majority of the sediments are thought to have been deposited in a variety ...