Evidence of pore-water advection in the Madeira Abyssal Plain from pore-pressure and temperature measurements

Abstract

Summary Measurements of pore pressure and temperature made in the Great Meteor East region of the Madeira Abyssal Plain (approximately 31°30′N, 24°30′W) are described in this paper. The aim of the study was to establish whether pore-water advection exists in the upper sediment sequence which is important for assessing the area as a potential repository for high-level radioactive waste. The relative merits of deducing advection velocities from pore-pressure or temperature gradients are considered, together with the accuracies that can be obtained from each technique and the data collected to date. Heat-flow measurements and non-linear sediment-temperature profiles indicate that hydrothermal circulation is present in the basement with upward advection occurring within sediments over some basement highs. However, the pore-pressure data imply that advection is generally absent within the area. The discrepancies in these interpretations are discussed with respect to the geological setting and the physical characteristics of the sediments.