When do turbidity currents stop moving

Finally, turbidites may evolve an incorporate more water as they flow and this causes lateral variations in depositional facies and structures. When a certain amount of water starts to be present in the flowing sediment, water infiltrates between grains reducing the overall matrix strength and making the flow non-cohesive.

High density currents like hyperconcentrated and concentrated density flows are sustained by buoyancy and grain- to grain support. Their relatively high viscosity and density hinders the development of Bouma sequences, since grain sizes are not free to move and separate within the flow. Hyperconcentrated flows are still chaotic and poorly organized, while in concentrated density flows we may see graded beds to a certain degree topped with cross and parallel laminae, even if the separation of the various grain sizes is not perfect.

Turbidity currents in a strict sense are low-density flows that can develop Bouma sequences or surge-type flows when only fine-grained sediments are available , as the high water content allows sediments to organize and move more freely within the flow, suspended in the turbulent flow.

Turbidites and erosion Turbidity currents and associated density flows commonly show erosional surfaces at their base. This happens because the currents, travelling on the seafloor at relatively high speed, have enough energy to erode the underlying beds.

Interlayer mudstones layer E of Bouma are often victims of erosive processes and rip-up clasts of mudstone, tore off the seabed, can be incorporated in the overlying bed. Channels and scours may develop at the base of the turbidite, leading to complex architectures characterized by truncated and amalgamated sandstone beds. Erosional contact: the turbidite at the top eroded the layer at the bottom.

The erosional truncation is well visible. Cala del Leone, Quercianella, Italy. Amalgamation between two sandstone layers separated by an erosional contact. Channel fill and complex amalgamation structures in several turbidite layers.

How many layers are there? Note: several clay chips also called rip-up clasts or soft clasts are visible. Soft-sediment deformation Turbidity currents deposit water-saturated sediments. After deposition, sediments start to compact into sedimentary rocks and water is expelled upwards. The presence of sequences of sand permeable and mud impermeable produces an architecture with barriers that hinder water escape from the sediment. Water tends, therefore, to concentrate at the top of turbidites, causing liquefaction to occur.

This deforms original sedimentary structures. The convolute lamination that occurs so frequently at the top of turbidites is the product of liquefaction over original parallel to cross lamination.

Dish , flame , and ball-and-pillow structures constitute other very common liquefaction-related structures. References Bouma, A. Sedimentology of some flysch deposits. Agraphic approach to facies interpretation , Lowe, D. Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents. Journal of sedimentary research , 52 1 , Mulder, T. The physical character of subaqueous sedimentary density flows and their deposits.

Sedimentology , 48 2 , Mutti et al. Deltaic, mixed and turbidite sedimentation of ancient foreland basins. Turbidity currents can be caused by earthquakes, collapsing slopes, and other geological disturbances.

Once set in motion, the turbid water rushes downward and can change the physical shape of the seafloor.

Turbidity is a measure of the level of particles such as sediment, plankton, or organic by-products, in a body of water.

As the turbidity of water increases, it becomes denser and less clear due to a higher concentration of these light-blocking particles. Turbidity currents can be set into motion when mud and sand on the continental shelf are loosened by earthquakes, collapsing slopes, and other geological disturbances. The turbid water then rushes downward like an avalanche, picking up sediment and increasing in speed as it flows.

Turbidity currents can change the physical shape of the seafloor by eroding large areas and creating underwater canyons.