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Summary Concretionary siderite horizons are quite common in massive clay sequences. One such horizon, from the Westphalian of Yorkshire, has been studied in detail. Two iron-rich carbonate minerals occur together although they cannot be distinguished in thin section on account of very fine grain size. One is much richer in magnesium (pistomesite) than the other (siderite). The latter is rela ...
Jan 1, 2011 · Iron oxide concretions are formed from post depositional, paleogroundwater chemical interaction with iron minerals in porous sedimentary rocks. The concretions record a history of iron mobilization and precipitation caused by changes in pH, oxidation conditions, and activity of bacteria. Transport limited growth rates may be used to estimate ...
- W.T. Parry
- 2011
Apr 20, 2018 · The mass of C within a tusk-shell spherical concretion is given by: Vc = 4/3πr c 3 · d(c) · n c, where r c is the radius of a concretion (mean value; 0.75 cm), d(c) is the average density of a ...
- Hidekazu Yoshida, Koshi Yamamoto, Masayo Minami, Nagayoshi Katsuta, Sirono Sin-ichi, Richard Metcalf...
- 2018
Oct 1, 2012 · Iron‐bearing concretions are valuable records of oxidation states of subsurface waters, but the first concretions to form can be altered drastically during later diagenetic events.
Iron oxide concretions are similarly complex and difficult to study. The differences in the abundances of the constituent solutes (Ca and carboxyls in carbonate system are more abundant than Fe and O2 in water) also suggest there would be significant differences in the reaction-transport mechanisms associated with the two concretion types.
Nov 1, 1996 · EARTH-SCIENCE REVIEWS ELSEVIER Earth-Science Reviews 41 (1996) 177-210 Concretion morphology, classification and genesis J. Sellés-Martínez Dep. Ciencias Geologicas, Fac. Ciencias Exactas, Universidad de Buenos Aires, Pa6ellon 2 Ciudad Universitaria, 1428 Buenos Aires, Argentina Received 10 October 1995; accepted 17 April 1996 Abstract A ...
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Mar 18, 2013 · Carbonate concretions are common features of sedimentary rocks of all geological ages. They are most obvious in sandstones and mudstones as ovoid bodies of rock that protrude from natural outcrops: clearly harder or better cemented than their host rocks. Many people are excited by finding fossils in the centre of mudstone-hosted concretions ...
