The Nansen ridge, Arctic Ocean; some geophysical observations of the rift valley at slow spreading rate

Abstract

We have examined continous echo soundings across the Nansen Rift Valley and analysed the first gravity and bathymetric data available across the northern flank of the Nansen Ridge for comparison with other parts of the mid-ocean ridge system. The observed width of the inner floor (1.7–5.5 km) at a total opening rate of 1.5 cm/yr supports the idea of progressive narrowing of the inner floor with decreasing spreading rate for slow spreading ridges. However, the observed distance between the outer walls (18–22 km) or rift valley width (30–33 km) suggests that these parameters at least to a first approximation tend towards a minimum value with decreasing spreading rate. The relation between gravity and bathymetry along the drift track of ice station FRAM-I tentatively suggests that the sea-floor topography of this part of the Nansen Ridge is supported by a plate with an elastic thickness less than what is observed on the Mid-Atlantic Ridge.