Turbidity currents

In the case of the turbidity currents, this redistribution usually occurs along the foot of the continental slope and is largely responsible for the accumulation of sediments in the continental rise. The resuspension of particles by contour currents can also maintain permanent nepheloid layers as shown in Figure 13.10. 

About 25% of the carbonates deposited in shallow water are eventually eroded and carried downslope by bottom and turbidity currents to become part of the shelf and pelagic sediments. Shallow-water carbonates are also notable for their mineral composition. In addition to calcite and aragonite, some shallow-water calcifiers deposit hard parts containing high percentages of magnesium. These are referred to as magnesium-rich calcites. 

Some basinal evaporites appear to have been deposited by turbidity currents as shown in Figure 17.10c. In this mode of formation, salts originally deposited in shallow waters are transported into the basin by turbidity currents. These salts fill in the basin. The decline in water depth then promotes in situ precipitation of evaporites. Subsidence would have kept the basin floor below the sill. 

Turbidite The sedimentary deposit created by turbidity currents. The latter are underwater mudslides common to the continental slope and rise. 

Turbidity current An underwater mudslide common to the continental slope. The particles deposit at the foot of the slope to form the continental rise. The resulting deposit is often referred to as a turbidite. 

Redeposition from shallower sites, both by mass transport (turbidity currents) and by resuspension. 

Turbidity currents—Local, rapid-moving currents that result from water heavy with suspended sediment mixing with lighter, clearer water. Causes of turbidity currents are earthquakes or when too much sediment piles up on a steep underwater slope. They can move like avalanches. 

Terrigenous sediments, i.e. elastics consisting of material eroded from the land surface, are not only understood as nearshore shallow-water deposits on the shelf seas, but also comprise the deltaic foreset beds of continental margins, slump deposits at continental slopes produced by gravity transport, and the terrigenous-detrital shelf sediments redistributed into the deep sea by the activity of debris flows and turbidity currents. 

The rather steep continental slope off the coast of Uruguay is distinguished by frequent irregular sedimentary transport events. Not only turbidity currents but also slides of relatively... 

Studies of sedimentation on the MAP revealed large sequences of turbidites. Turbidites are sediments transported by turbidity currents that are rapidly accumulated sedimentary units (Weaver and Kuijpers, 1983 Weaver et al, 1998b). There are three different types of... 

The emplacement process produced repeated units of turbidites spread over the whole area of the abyssal plain with weU-mixed material in each individual unit. Carbonate dissolves very rapidly and the carbonate content may in part be dissolved during transport in turbidity currents, thus causing a relative increase in TOC. 

Masson D. G. (1994) Late Quaternary turbidity current pathways to the Madeira Abyssal Plain and some constraints on turbidity current mechanisms. Basin Res. 6, 17-33. 

Weaver P. P. E. and Thomson J. (1993) Calculating erosion by deep-sea turbidity currents during initiation and flow. Nature 364, 136-138. 

On extensive areas of the seafloor, fast-flowing turbidity currents erode cohesive mud, which replaces the coarser-grained material settling out of the suspension in the slackening body and tail of the currents (Komar, 1969 Piper et al., 1988 Einsele, 1992 Walker, 1992a),... 

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