The Tertiary strike-slip basins and orogenic belt of Spitsbergen.

The Svalbard margin evolved to its present rifted configuration through a complex strike-slip history of both transtension and transpression. Because the Paleogene plate boundary, the De Geer Line, lay just W of Spitsbergen, many of the details of this structural evolution are contained in a narrow fold and thrust belt, and within a series of sedimentary basins, on Spitsbergen. The early to mid-Paleocene Central Basin was of extensional (possibly transtensional) origin, and contains >800m of clastic deposits. it evolved from a series of partly connected coal basins to a single, open-marine basin. The late Paleocene to early Eocene Central Basin, of transpressional origin, was infilled by >1.5km of clastic sediments from deltas, which prograded out from the rising orogenic belt. The fold and thrust belt of W Spitsbergen, mainly of late Paleocene to Eocene age, was also a product of transpression. Forlandsundet Graben, infilled by as much as 5km of alluvial and marine clastics, probably formed from late Eocene collapse of the crest of the orogenic belt, or from extension adjacent to a curved fault zone. Rift basins, up to 7km deep, developed W of Svalbard as the continental margin changed, beginning in the early Oligocene, from a strike-slip to a rifted regime.-Authors