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Detrital sedimentary graded beds are formed from erosional, depositional, and weathering forces. Graded beds formed from detrital materials are generally composed of sand, and clay. After lithification, shale, siltstone, and sandstone are formed from the detrital deposits.
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 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.
Any sedimentary rock composed of millimeter or finer scale layers can be named with the general term laminite. When sedimentary rocks have no lamination at all, their structural character is called massive bedding. Graded bedding is a structure where beds with a smaller grain size occur on top of beds with larger grains. This structure forms ...
Graded bedding - In certain types of clastic sedimentary rock, the grain or clast size varies systematically from the base of the bed to its top. In a normally graded bed the grain or clast size is largest at the base and the bed is said to fine upwards. Beds deposited by density underflows such as turbidites typically show normal grading.
Repeated avalanches will eventually form the sedimentary structure known as cross-bedding, with the structure dipping in the direction of the paleocurrent. The sediment that goes on to form cross-stratification is generally sorted before and during deposition on the "lee" side of the dune, allowing cross-strata to be recognized in rocks and ...
Classic, low-density turbidites are characterized by graded bedding, current ripple marks, climbing ripple laminations, alternating sequences with pelagic sediments, distinct fauna changes between the turbidite and native pelagic sediments, sole markings, thick sediment sequences, regular bedding, and an absence of shallow-water features. [3]
They can be found in sedimentary rock sequences of all ages but probably make up less than 1 percent by weight of all sedimentary rocks. They are closely related to sandstones in origin, and exhibit many of the same types of sedimentary structures, such as tabular and trough cross-bedding and graded bedding. [1] [2] [3]