Structural analysis of the Devonian Basin of northrn Svalbard shows that the basin fill is affected by large-scale, N-S trending folding and thrust faulting. This folding can be attributed to both the Late Devonian Svalbardian and the West Spitsbergen Fold Belt deformation tectonic events. Each of these events corresponds to E-W compression and there is no evidence for Late Devonian transpression. The basin fill is presently limited by N-S trending extensional faults which parallel those controlling the post-Eocene structure of the western margin of Svalbard. The older basin sediments reflect extensional fault activity at the time of deposition, while deposition of the younger rocks was not accompanied by any signilicant faulting. Simplilied modelling of the subsidence history of the Devonian Basin suggests that most of the tectonic subsidence occurred during the 8 Ma Gedinnian period by extension which produced a lithospheric thinning with a stretching factor of about 1.82. The tectonic subsidence was followed by thermal subsidence from Siegenian to Famennian time (41 Ma). The Svalbardian tectonic event can be correlated with the Mid-Devonian to Early Carboniferous Ellesmerian orogeny which alfected large areas of the North American-Greenland Block.
Geoff Manby, Thames Polytechnic, School of Earth Sciences, Walburgh House, Bigland Str., London El 2NG, UK;
Nicolas Lyberis, Universite Paris VI, DP' de Geotectonique, 4 Place Jussieu, 75252 Paris Cedex 05, France.