ABSTRACT

The current tectonic interpretation of the Paleogene Central Basin on Spitsbergen operates with two stages, involving Paleocene strike slip and Eocene compression, in accordance with available offshore evidence for paleotectonic regime along a controlling, major intraplate transform fault zone west of Spitsbergen. This paper suggests a new interpretation for the Central Basin, in which the entire Paleocene-Eocene basin fill is incorporated into a foreland-basin scenario. The interpretation is facilitated by recent time constraints on Late Cretaceous and Paleogene sea-floor spreading in the Norwegian-Greenland Sea and Arctic Sea, and recent field data from Spitsbergen. The Central Basin succession displays cyclicity of several scales of magnitude, with a large-scale landward-stepping-basinward-stepping stacking pattern. The Paleocene, overall landward-stepping, eastward-migrating succession of coastal-plain-to-shelf deposits was derived from the peripheral bulge east of the present basin margin, and the Eocene basinward-stepping, also east-migrating succession of clastic wedges was derived from the West Spitsbergen Orogen to the west of the basin. The landward-stepping-basinward-stepping trend is interpreted to be a result of gradual eastward translation of the entire basin in response to lithospheric shortening. The Paleocene, overall landward-stepping trend is perturbed by two intermediate-scale transgressive-regressive cycles. Intermediate-scale transgressions and regressions are interpreted to result from episodic uplift and erosion of the peripheral bulge. Each intermediate-scale cycle in turn consists of numerous stacked, small-scale depositional sequences. Small-scale sequences within the transgressive limbs of intermediate-scale cycles are thin and tabular, and onlap the eastern basin-margin. They probably formed during tectonically "quiet" periods where the peripheral-bulge relief was gradually eroded and the basin floor was gently downwarped due to sediment loading. Small-scale sequences of the regressive limbs are wedge shaped, strongly basinward stepping, and associated with regional unconformities along the eastern basin margin. They probably formed during periods of tilting of the eastern basin margin in response to uplift and basinward migration of the peripheral bulge.