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In geology, a bed is a layer of sediment, sedimentary rock, or volcanic rock "bounded above and below by more or less well-defined bedding surfaces". [1] A bedding surface or bedding plane is respectively a curved surface or plane that visibly separates each successive bed (of the same or different lithology ) from the preceding or following bed.
In geology, lamination (from Latin lāmina 'thin layer') is a small-scale sequence of fine layers (pl.: laminae; sg.: lamina) that occurs in sedimentary rocks. Laminae are normally smaller and less pronounced than bedding .
Where the set height is less than 6 centimeters and the cross-stratification layers are only a few millimeters thick, the term cross-lamination is used, rather than cross-bedding. Cross-bed sets occur typically in granular sediments, especially sandstone , and indicate that sediments were deposited as ripples or dunes, which advanced due to a ...
These structures are within sedimentary bedding and can help with the interpretation of depositional environment and paleocurrent directions. They are formed when the sediment is deposited. Cross-bedding Cross-bedding is the layering of beds deposited by wind or water inclined at an angle as much as 35° from the horizontal. [1]
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 ]
Convolute bedding forms when complex folding and crumpling of beds or laminations occur. This type of deformation is found in fine or silty sands, and is usually confined to one rock layer. This type of deformation is found in fine or silty sands, and is usually confined to one rock layer.
In geology, a graded bed is a bed characterized by a systematic change in grain or clast size from bottom to top of the bed. Most commonly this takes the form of normal grading, with coarser sediments at the base, which grade upward into progressively finer ones. Such a bed is also described as fining upward. [1]
Lenticular bedding is a sedimentary bedding pattern displaying alternating layers of mud and sand. Formed during periods of slack water , mud suspended in the water is deposited on top of small formations of sand once the water's velocity has reached zero.