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The Sachrang Formation or "Posidonienschiefer" Formation (Whose Vulgar name is "Posidonia Shale") is a geological formation of southwestern Germany, northern Switzerland, northwestern Austria, southeast Luxembourg and the Netherlands, that spans about 3 million years during the Early Jurassic period (early Toarcian stage). It is known for its detailed fossils, especially sea fauna, listed below.[1] Composed mostly by black shale, the formation is a Lagerstätte, where fossils show exceptional preservation (Including exquisite soft tissues), with a thickness that varies from about 1 m to about 40 m on the Rhine level, being on the main quarry at Holzmaden between 5 and 14 m.[1] Some of the preserved material has been transformed into fossil hydrocarbon Jet, specially wood remains, used for jewelry.[2] The exceptional preservation seen on the Posidonia Shale has been studied since the late 1800s, finding that a cocktail of chemical and environmental factors let to such an impressive conservation of the marine fauna.[2] The most common theory is the changes in the oxygen level, where the different anoxic events of the Toarcian left oxygen-depleted bottom waters, with the biota dying and falling to the bottom without any predator able to eat the dead bodies.[3]
- ^ a b Hess, H. (1999). "Lower Jurassic Posidonia Shale of Southern Germany" (PDF). Fossil Crinoids. 3 (1): 183–196. doi:10.1017/CBO9780511626159.025. ISBN 9780521450249. Retrieved 3 March 2022.
- ^ a b Martill, D. M. (1993). "Soupy substrates: a medium for the exceptional preservation of ichthyosaurs of the Posidonia Shale (Lower Jurassic) of Germany" (PDF). Kaupia. 2 (1): 77–97. Retrieved 3 March 2022.
- ^ Schmid–Röhl, A.; Röhl, H. J. (2003). "Overgrowth on ammonite conchs: environmental implications for the Lower Toarcian Posidonia Shale". Palaeontology. 46 (2): 339–352. Bibcode:2003Palgy..46..339S. doi:10.1111/1475-4983.00302. S2CID 128413601.