An arm of the North Atlantic seaway reached Svalbard during the Paleocene, either in advance of, or in response to, early drift of Greenland away from the Eurasian continental block. Initial Tertiary sediments in Svalbard were marine, littoral, and paludal clastics and coals formed during an oscillating northeastward transgression of the sea. Second and third depositional cycles followed consisting of marine clay units that grade upward into fine or, locally, coarse regressive sandstone. Through the early stages of the third depositional cycle (mid? Eocene) movements were epeirogenic, and transgressions were toward a land area in northeastern Svalbard. Although Greenland had been drifting away from Norway along the Spitsbergen fracture zone (dextral transform fault), there is no evidence of contemporaneous tectonic interaction between the Greenland and Barents blocks.

The third depositional cycle was brought to a close by an influx of clastic material from the west in response to rapid uplift either within or along the western margin of the basin. Continued uplift in the west provided a flood of detritus that eventually filled the basin with plant-bearing alluvial, fluviatile, and paludal sediments. Uplift culminated in upthrusting, folding, and local overthrusting of the central or western part of the Tertiary basin; only the northeastern part of the basin is preserved now in the strongly asymmetrical Spitsbergen trough. Tectonism was the result of Greenland pressing against the Barents block while moving parallel with it (transpression), and the resulting structures show dextral shear as well as compressional features. Subsequent parting of the Greenland and Barents blocks resulted in tensional stress with dextral shear (transtension) and the formation of large grabens filled with locally derived, coarse-clastic sediments within the uplifted western margin of the trough. Separation is thought to have been completed by latest Oligocene or possibly early Miocene time.

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