Abstract
Late Cenozoic outbuilding of the mid-Norwegian continental shelf (62º N-69º 30’N) demonstrates strong relationship between uplift, erosion, subsidence, variations in relative sea level, basin infill, glacial dynamics and climate. During Late Cenozoic clastic wedges prograded NW making toplap truncations with the URU (Upper Regional Unconformity). Sequences above the URU demonstrate aggradation and progradation at smaller scale.
The purpose of this study has been to get better understanding of the Plio-Pleistocene source-to-sink relationships, influence of glacial-interglacial cyclicity, variation in accommodation space as function of basin subsidence and glacioeustacy, and glacial dynamics and sedimentation. The present project includes seismic stratigraphic interpretation of 45 multi-channel 2D regional high resolution seismic lines of the mid-Norwegian continental shelf followed by seismic sequence analysis and seismic facies analysis. 32 sequences developed during 32 glacial-interglacial cycles which were initiated about 2.8 m.y. ago. The seismic sequences have been grouped and mapped into four megasequences.
Megasequence-1 is comprised of steeper clinothems whereas megasequence-2 and megasequence-3 have gentler clinothems. Moreover, seismic sequences associated with megasequence-2 and megasequence-3 have great extension in mid-Norwegian continental shelf. Ages of seismic sequences have been interpolated partly from previous studies. Glacial-interglacial cyclicity is about 70 000 years in megasequence-1, 80 000 years in megasequence- 2, 115 000 years in megasequence-3 and c. 70 000 years in megasequence-4. Relative sea level fluctuations have been determined with trajectory analysis. Glaciations of Iceland and Svalbard margin have been correlated with glaciations of the mid-Norwegian continental shelf.
Depositional environments have been determined using seismic facies. Furthermore, four seismic facies are interpreted with in the Naust Formation which correspond to glacigenic debris flows, glacimarine sediments, slide debrites and hemipelagic/contouritic sediments.