Analysis of a longitudinal ripple from the Nova Scotian continental rise

Document Type


Date of Original Version



A longitudinal ripple was obtained in a box core taken from the Nova Scotian continental rise in July 1982. Soft brown mud comprising 1.5-10% sand, ∼60% silt and ∼35% of <2 μm clay forms the 5 cm high and ∼40 cm wide ripple. A maximum thickness of 8 cm of this mud under the crest, thinning to 2 cm on the ripple's flank, overlies stiff muddy foram ooze. The vane shear strength of the brown mud is ∼0.4 kPa whereas that of the ooze is ∼4 kPa. X-radiographs show the mud to contain many fine burrows and a few larger ones as well as winnowed horizons rich in foraminifera of both benthonic and planktonic origin. Gentle wet sieving of the sand fraction on board ship showed the sand fraction to contain very few faecal pellets. Thus it appears unlikely that bedload movement played a large part in formation of the ripple. Rapid initial deposition from a concentrated suspension is suggested to have formed the structure, but this was followed by periods of erosion to yield winnowed horizons and further rebuilding with material deposited from suspension. Radiochemical data (234Th and 210Pb) and X-radiographs suggest intense particle mixing (DB ∼90 cm2 yr-1) and rapid sediment deposition (∼1.5 cm month-1). Thus it is possible that the bedform (and associated structures) are destroyed and recreated on a time-scale of a few months. © 1984.

Publication Title

Marine Geology