The Svalbardian tectonic event affecting the Devonian sediments of northem Spitsbergen formed thrusts and folds with cleavage structure, unconformably overlain by Early Carboniferous sediments. The Devonian basin was an asymmetrical, N-S trending graben, characterized by an easterly dipping basement. The Late Silurian to Early Devonian basin infill is affected mostly by extensional features while the Middle and Late Devonian sediments form thrusts and folds associated with cleavage. Bed-parallel normal movements and normal slip surfaces attest a general detachment and movernent of the Devonian sediments from west to east. This general detachment is Late Devonian in age and may have been gravity induced, favoured by the slope of the east-dipping asymmetric graben. The detached sediments moving to the east were compressed against the large eastern border fault while they were extended in the western part of the graben. This event did not interrupt significantly the lithospheric graben evolution, and subsidence proceeded afterwards during the Carboniferous.
J. Chorowicz, Departement de Geotectonique, Universite Paris 6, URA-CNRS 1315, Boite 129, 4 place Jussieu, 75252 Paris Cedex 05, France.