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Sedimentary structures include all kinds of features in sediments and sedimentary rocks, formed at the time of deposition. Sediments and sedimentary rocks are characterized by bedding , which occurs when layers of sediment, with different particle sizes are deposited on top of each other. [ 1 ]
There are a few distinctly different channel types based on their geological structure and depositional environment. Braided rivers carry fairly coarse-grained sediment down a fairly steep gradient. They typically exhibit numerous channels that split off and rejoin each other to give a braided appearance.
Bouma A is the first layer deposited by a flow, provided the flow has sufficient energy. Otherwise Bouma B, C or D will be the first layer deposited. Bouma A is deposited when the flow energy is high enough that fluid turbulence is able to keep the coarsest grains in suspension. When energy drops below a critical level, the grains tend to ...
As a consequence, a slightly different set of sedimentary structures develops in turbidites deposited by high-density turbidity currents. This different set of structures is known as the Lowe sequence , which is a descriptive classification that complements, but does not replace, the Bouma sequence.
In case of volcanic rocks, the lithostratigraphic unit equivalent to a bed is a flow. A flow is “...a discrete, extrusive, volcanic rock body distinguishable by texture, composition, order of superposition, paleomagnetism, or other objective criteria.” A flow is a part of a member as a bed of sedimentary rock is a part of a member. [18] [19]
For the main article about the sedimentary structures known as flutes and flute casts, please see Sole markings. In sedimentology, a flute is a primary sedimentary structure consisting of a discontinuous scoop-shaped, spatulate, or lingulate depression or groove. Flutes typically range from 5–50 cm (2.0–19.7 in), in width, from 1–20 cm (0 ...
Sand waves are formed through the action of the wind or water (through waves or tidal currents) [2] and are a product of unidirectional flow. Sand waves are the result of a mean flow velocity between 40 and 70 cm/s. Sand waves also form underwater. [3] [4]
The belief of the researchers is that the water flow is the tail-end of the process that starts at the seafloor. [1] In the most typical case of oceanic turbidity currents, sediment laden waters situated over sloping ground will flow down-hill because they have a higher density than the adjacent waters.