Black shales are dark carbonaceous shales rich in organic matter, containing 0.5 to more than 10% organic carbon. They contain dispersed kerogen, which is finely mixed with the mineral matrix (especially clay minerals). Depending on the sedimentary environment and allochthonous support, the kerogen can be of algal origin (originally high H/C ratio, aliphatic character), transitional or terrestrial higher plants origin (low H/C, high O/C ratio, aromatic character).
Black shales are deposited in quite aquatic environments receiving a certain minimum amount of organic matter. Well-known representatives of these sedimentary rocks are Proterozoic Nonesuch black shales (Michigan, USA), Devonian black shales (Indiana, Kentucky and Ohio, USA), Jurassic, Lower Toarcian Posidonia shales (France, Germany). Black shales and sapropels are frequently parts of sequences representing changing environmental conditions as oxic/anoxic transitions or organic rich/organic poor transitions (Cita et al.,...
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Bibliography
Cita, M.B., de Lange, D.J. and Olausson, E. (1991) Anoxic basins and sapropel deposition in the Eastern Mediterranean: past and present. Mar. Geol., 100, 1–4.
Didyk, B.M., Simoneit, B.R.T., Brassell, S.C. and Eglinton, G. (1978) Organic geochemical indicators of paleoenvironmental conditions of sedimentation. Nature, 272, 216–22.
van Graas, G., Viets, T.C., De Leeuw, J.W. and Schenck, P.A. (1983) A study of the soluble and insoluble organic matter from the Livello Bonarelli, a Cretaceous black shale deposit in the Central Apennines, Italy. Geochim. Cosmochim. Acta, 47, 1051–9.
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Jehlička, J. (1998). Black shales and sapropels . In: Geochemistry. Encyclopedia of Earth Science. Springer, Dordrecht. https://doi.org/10.1007/1-4020-4496-8_34
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DOI: https://doi.org/10.1007/1-4020-4496-8_34
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