Seismic Study of the Outer Vøring Margin

Abstract

Rifting between Norway and Greenland culminated in Late Paleocene - Early Eocene when the continents of Greenland and Eurasia separated through seafloor spreading. This seafloor spreading was accompanied by voluminous volcanism leaving behind a large magmatic complex. In this project 2D seismic reflection data provided by the Norwegian Petroleum Directorate (NPD) has been used to map and evaluate the architecture of this breakup complex along the Vøring Margin, off Norway. It is found that the volcanic development of the margin north of the Jan Mayen Fracture Zone initially was characterized by voluminous subaerial flood basalt eruptions. The character of these deposits seems to depend on the geometry of the surrounding rift basins and the presence of water. The most conspicuous volcanic facies developed during the first phase of volcanism is the Inner Seaward Dipping Reflectors (Inner SDRs) which represents basalt flows that have acquired a seaward dip subsequent to deposition due to a seaward increasing thickness of the lava pile. Drowning of the volcanic fissure through subsidence led to explosive submarine volcanism resulting in the buildup of prominent volcanic mountains. Continued subsidence along the margin eventually caused the eruption center to reach a level at which explosive volcanism no longer could occur. This resulted in the development of deep marine lava flows filling the space seaward of the volcanic mountains before normal seafloor spreading commenced. The described evolution is consistent with the principles of seismic volcanostratigraphy, developed by Planke et al. (2000). The region along the JMFZ is characterized by an additional volcanic phase, the Outer Plains, previously described by Berndt et al. (2001). The Outer Plains are located between the Inner SDR and normal oceanic basement. The seismic expression of this unit suggests a subaqueous emplacement environment, but its origin remains unknown.A secondary goal of this master was to define the area in which the transition from continental to oceanic crust occurs. Unfortunately, because of the heterogenic nature of the magmatic breakup complex the image of underlying structures is heavily distorted. A zone between the Inner SDR, which is known to be at least partly underlain by continental crust, and the first identified normal oceanic basement is defined to represent the Continent-Ocean Transition (COT).