Submersible studies of deep-sea furrows and transverse ripples in cohesive sediments

Abyssal furrows and ripples, formed in cohesive sediments, have been observed and sampled by submersible on the Bahama Outer Ridge. These features have developed as bed forms of steady bottom currents presently flowing at 5-20 cm/sec. Small furrows developed high on the secondary outer ridge are asymmetrical, and have existid for at least the last 11,000 years. Cross-furrow variations in microtopography, sediment type, and accumulation rate suggest that the furrows are maintained by present-day currents. Transverse ripples on furrow wails are developed in cohesive sediments and have small corniches similar to those observed in snow downwind from mountain ridges. Regional changes in furrow type and morphology may reflect changes in sedimentary conditions and furrow evolution (current velocity, sediment type, sedimentation rate), or they may reflect different furrow origins.