A geophysical study of the northern Svalbard continental margin

In the summer of 1999, the first systematic seismic profiles were acquired across the northern Svalbard continental margin east of 15degreesE. Approximately 1470 km of multi-channel seismic reflection data as well as sonobuoy wide-angle data were collected up to 82degreesN. With few exceptions the signals imaged the whole sedimentary cover down to the acoustic basement. The uppermost sedimentary deposits of the inner shelf yield P-wave velocities of 2 km s(-1) and higher, indicating erosion and compaction due to a former ice load. The inner shelf east of Hinlopen Strait has only a thin veneer of over-consolidated sediments above the acoustic basement. Beneath the outer shelf, up to 3.5 km of sedimentary deposits cover the down-faulted acoustic basement. The continental slope is heavily eroded due to bottom current activity and slumping. At about 30degreesE the morphology of the continental slope has a smooth appearance. Shelf progradation only in the vicinity of glacial troughs crossing the shelf (associated with submarine fans) indicates main sediment transport by ice streams during former glacial periods. The maximum sedimentary thickness in the Sophia Basin is more than 9 km, and the Nansen Basin has a sediment thickness of 4.5 km close to the margin. Gravity modelling along the seismic profiles was performed to constrain the position of the continent-ocean transition. Existing sedimentary thickness and structural maps were extended over the area investigated. The new data provide no evidence for the presence of former extensive subaerial volcanic sequences (seaward-dipping reflectors), which would have been emplaced during the break-up along the margin. Thus, we consider this part of the margin as non-volcanic.