Chapter 7 Sediment Entrainment

Publisher Summary Sediment entrainment refers to the processes by which contour currents capture and transport sediments. This chapter describes the processes that are potentially capable of delivering similar sediments to contour-current systems. Sediment entrainment for contourites is mainly based on theoretical interpretation and on speculations regarding sedimentary features of modern and ancient contourites including grain size, components, textures, and structures––in terms of fluid hydrodynamics of possible flows operating in oceans. The mechanisms of sediment entrainment processes are categorized based on sedimentary textures, structures, and components of various contourites, as well as on their spatial variation. The most important mechanisms for sediment entrainment in contourites are: (1) the resuspension from bottom currents or benthic storms, (2) sediment density flows––including turbiditic and hyperpycnal flows, (3) micro-bioclastics-forming processes, (4) volcanic, (5) glacial activity, and (6) burrowing. Bottom currents resuspend or rework the sediments on their pathways. Gravity flows deliver both fine and coarse sediments to the pathways of contour currents. Bioclastics-forming processes provide bio-skeletons or fragments to contourites. Volcanic and glacial processes provide significant amounts of sediments to contour currents in some special situations. Bioactivity that can resuspend sediments is less significant in most cases.