GRAVITY AND S-WAVE MODELLING ACROSS THE JAN MAYEN RIDGE, NORTH ATLANTIC; IMPLICATIONS FOR CRUSTAL LITHOLOGY

Abstract

The horizontal components from fourteen Ocean Bottom Seismometers deployed along four profiles focused along the western margin of the Jan Mayen microcontinent, North Atlantic, have been modelled with regard to S-waves, based on P-wave models obtained earlier. The seismic models have furthermore been constrained by 2D gravity modelling. High V p/V s-ratios (2.3–7.9) within the Cenozoic sedimentary section are attributed to significant porosities, whereas V p/V s-ratios in the order of 1.9–2.2 for the Mesozoic and Paleozoic sedimentary rocks indicate shale-dominated lithology throughout the area. The eastern side of the Jan Mayen Ridge is interpreted as a passive, volcanic margin, based on relatively high crustal V p/V s-ratios (1.9), whereas lower V p/V s-ratios (1.75–1.8) suggest the presence of intermediate composition crust and non-volcanic margin on the western side of the ridge. In the westernmost part of the Jan Mayen Basin, slightly increased upper mantle V p/V s-ratios may indicate some degree of serpentization of upper mantle peridotites.