Clastic dykes from the Precambrian Porsangerfjord Group, North Norway

• Published in: Geological Magazine
• Main Author: Williams, D. M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1976
• Subjects: Finnmark; North Norway
• Online Access: http://dx.doi.org/10.1017/s0016756800036475; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756800036475

Summary Clastic dykes are described from a late Precambrian sequence of shallow water sediments — the Porsangerfjord Group of Finnmark, North Norway. The dykes are from one stratigraphic member of the Group and only occur where this member outcrops in a zone where sedimentation was thought to have been affected by recurrent earthquake shock. The dykes consist of poorly defined sandstone clasts in a muddy matrix. They exhibit no significant internal sedimentary structures. It is suggested that the dykes were intruded due to remobilization of sediment affected by a combination of tectonic shock and hydrostatic load. The dykes bear no genetic relationship to tectonic structures (cleavage and jointing) and evidence suggests that dewatering was virtually complete before the formation of the first cleavage.