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Some of the most unusual concretion nuclei are World War II military shells, bombs, and shrapnel, which are found inside siderite concretions found in an English coastal salt marsh. [10] Depending on the environmental conditions present at the time of their formation, concretions can be created by either concentric or pervasive growth.
Similar to the marine nodules, concretion layers are defined based on iron and manganese content as well as their combination. [2] High iron content nodules appear a red or brown color, while high manganese content appears black or grey. [2] The dominant metal oxide is related to the elements enriched in the nodule.
The concretions occur in localized deposits within the silty to sandy mudstones, in the lower four metres of the formation. The paleoecosystem was once believed to be a large river delta system, deposited by at least one major river system flowing from the northeast, but it has been reinterpreted as a bay into which some rivers brought some ...
The Pierre Shale is the host formation for commercial petroleum deposits in the Florence and Canon City fields in Fremont County, Colorado, and the Boulder Oil Field in Boulder County, Colorado. More recently, natural gas has been extracted in the Raton Basin in southern Colorado .
Cone-in-cone structures have been known since the late 1700s, and people have attempted to explain the reasons for their formations. One of the earlier explanations was actually on par with the currently accepted methods for formation as discussed above. Some of the other methods offered for their formation were given by Shaub (1937). [9]
Devonian nodular limestone Concretionary nodular limestone at Jinshitan Coastal National Geopark, Dalian, China. In geology and particularly in sedimentology, a nodule is a small, irregularly rounded knot, mass, or lump of a mineral or mineral aggregate that typically has a contrasting composition from the enclosing sediment or sedimentary rock.
Part of the hammer is embedded in a limey rock concretion, leading to it being regarded by some as an anomalous artifact. The tool is identical to late 19th-century mining hammers, and the most likely explanation for its encasement in rock is that a deposit of highly soluble travertine formed and hardened around it within a relatively short time.
A coal ball is a type of concretion, varying in shape from an imperfect sphere to a flat-lying, irregular slab.Coal balls were formed in Carboniferous Period swamps and mires, when peat was prevented from being turned into coal by the high amount of calcite surrounding the peat; the calcite caused it to be turned into stone instead.