Abstract Particle-laden flows or turbidity currents along the seafloor are important to the formation and erosion of submarine topography. To understand the mass-transport process, flume tests were carried out with a continuous supply of quartz-laden suspension. The vertical and horizontal velocities were extracted by two pairs of ultrasound Doppler velocity profilers installed at different angles with respect to the bed-normal direction. Due to the head intrusion into the ambient water, the sediment in the suspension was continuously lifted up and mixed, leaving lobes and clefts. The velocity-maximum layer acted as the main sediment conveyor and divided the body into wall and jet regions. The concentration distribution was also quantified based on the relationship between the fluid density and the intensity of light attenuation obtained using a video recording. An area of high sediment concentration was observed just behind the head frontal area. Analysis of the velocity and concentration distribution demonstrated that sediment in the turbidity current was transported mainly by head movement and that continuous sedimentation took place in the wall region. The results indicate that a turbidity current proceeds while maintaining an ordered inner dynamic structure.

Abstract A unified system of collecting structural data from drill core is proposed. The system encompasses planes and planar fabrics, lineations, fold hinges and hinge surfaces, faults and shear zones, vorticity vectors, shear directions and shear senses. The system is based on standard measurements of angles in the reference frame of the core (α and β angles), which are easily carried out by means of core protractors or templates. The methods for dealing with folds and kinematic analysis of shear zones have not been described previously, but they follow logically from the standard methods for dealing with planes and lines.