Vertical open burrows in deep-sea sediments 2 m in length

Abstract

Previous studies of the mixed layer, in deep-sea sediments suggest a maximum burrowing depth of about 10–30 cm (ref. 1). However, we now report that two recently obtained cores from the north-east Atlantic (S126/2 and S126/4) display open burrows to a depth of 214 cm within a distal pelagic turbidite. An organic lining in one of the burrows indicates a modern origin. Many of the burrows are less than 0.5 mm across and are only visible on fractured surfaces. Their effects on sediment mixing are probably minimal, but they provide a network of open vertical channels which considerably increases the permeability. This is of crucial importance to studies involving pore water movement, such as those associated with the radioactive waste disposal project. The effect of the burrows changes the calculated permeability from the equivalent of a clay to that of a coarse sand. The delicate structure of the burrows may result in their closure during handling, thus requiring their effect on pore water fluxes to be studied in situ.