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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 ]
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]
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 ...
The convention for analysing structural geology is to identify the planar structures, often called planar fabrics because this implies a textural formation, the linear structures and, from analysis of these, unravel deformations. Planar structures are named according to their order of formation, with original sedimentary layering the lowest at S0.
Heterolithic bedding is a sedimentary structure made up of interbedded deposits of sand and mud. It is formed mainly in tidal flats but can also be formed in glacial environments. Examples from fluvial environments have been documented but are rare. [1] Heterolithic bedding forms in response to alternations in sediment supply and tidal velocity ...
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 ...
These phase diagrams [1]: 1 [9] are used for two main purposes: i) for prediction of bed states in a known flow and sediment transport condition, and, ii) as a tool for the reconstruction of paleoenvironments from a known bed state or sedimentary structure. Despite the great utility of such diagrams, they are very difficult to construct, making ...
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]