Stratigraphy, neo-tectonics and mass wasting of deep water drifts in the Fram Strait

Abstract

The primary goal for this thesis was the reprocessing and interpretation of 2D seismic lines in the Fram Strait and West Svalbard Margin (WSM). Seismic data quality was significantly improved through the implementation of new processing steps that had previously not been applied, incl. e.g. burst removal and a more advanced type of migration. The reprocessed lines were acquired by CAGE over multiple years prior to 2016 and were integrated in a seismic database with a number of seismic surveys in the study area to comprise a regional database. This database, together with bathymetric data collected in the area, made up the basis of interpretations, which focused on stratigraphic development of the deep-water area of the West Svalbard Margin and Fram Strait in relation to contourite drift development, neotectonic setting and processes of submarine landslides in the area. Notable features in this deep-water setting were several smaller and larger drift deposits, among which the Vestnesa Ridge is well-known and well-studied for its active fluid flow system. The seismic database allowed extending stratigraphic correlations of the 1.5 Ma and 2.78 Ma horizons from ODP sites and existing stratigraphy on the Yermak Plateu further south and into the deep-water area. This facilitated studying the differences in sedimentation rates on the WSM and revealed high sedimentation rates at Vestnesa Ridge as well as slightly thicker sediment packages south on WSM than north. Two main seismic facies were identified in the data and were characterized by 1) Parallel and horizontal and 2) subparallel and wavy reflection patterns. Parallel and horizontal reflection patterns were observed along the gentler sloped areas east on the WSM and are related to hemipelagic settling and sheeted drift structures. Subparallel and wavy reflection patterns were interpreted to be related to drift deposits with moat-levee structures and were observed exclusively on the deeper and steeper parts of the western slope along the WSM, indicating strong bottom currents along the Molloy Ridge. Landslides were observed on the western slope of WSM and are related to the development of drift deposits on the steeper slopes, which have contributed to slope instability. Combined with toe erosion of the slope by normal faults related to the Knipovich and Molloy Ridges and earthquakes these conditions may have triggered the landslides observed.