Sachrang Formation | |
---|---|
Stratigraphic range: Early-Late Toarcian[1][2] ~ Possible Latest Pliensbachian records[3] | |
![]() Posidonia Shale (Posidonienschiefer) Outcrop | |
Type | Geological formation |
Unit of |
|
Sub-units |
|
Underlies | Jurensismergel Formation (Germany) Werkendam Formation (Netherlands) Klaus Formation (Austria) Marnes à Bifrons Formation (Luxembourg) |
Overlies | Amaltheenton Formation (Germany) Aalburg Formation (Netherlands) Scheibelberg Formation (Austria) |
Lithology | |
Primary | Black shale |
Other | Lime mudstone, nodular claystone |
Location | |
Region | Western & Central Europe |
Country | ![]() ![]() ![]() ![]() ![]() ![]() |
Extent |
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Type section | |
Named for | The village of Sachrang, Bavaria |
Named by | Jacobshagen |
Location | Border with Tyrol above Sachrang |
Year defined | 1965 |
Coordinates | 47°41′N 12°14′W / 47.69°N 12.24°W[4] |
Holzmaden, location of the main Outcrop |
The Posidonia Shale (German: Posidonienschiefer, also called Schistes Bitumineux in Luxembourg) geologically known as the Sachrang Formation, is an Early Jurassic (Early to Late Toarcian) geological formation of southwestern and northeast Germany, northern Switzerland, northwestern Austria, southern Luxembourg and the Netherlands, including exceptionally well-preserved complete skeletons of fossil marine fish and reptiles.[5][6][7]
The Posidonienschiefer, the German translation, takes its name from the ubiquitous fossils of the oyster-related bivalve "Posidonia bronni" (synonym of Bositra buchii and Steinmannia bronni) that characterize the mollusk faunal component of the formation. The name Posidonia Shale has been used for more than a century, until revisions in 2016 proposed the Sachrang Formation as new name for the Germanic unit, in a same way Altmühltal Formation is the official name of the Solnhofen Limestone.[8] The Posidonia Shales where stablished as a valid vulgar name for this regions lower Toarcian Black Shales. The name Posidonienschiefer, while valid, represents another vulgar nomination, as Posidonia is an invalid genus and junior synonym of Bositra.[8] The type profile is still located on Dotternhausen.[8]
The formation comprises finely laminated layers of oil shales formed of fine-grained sediments intercalated with bituminous limestones and crops out in a number of locations in southwestern Germany, although most remains are from near the village of Holzmaden and Dotternhausen.[7] The European oil shales deposited on a sea floor during the Early Toarcian in the ancient Tethys Ocean are described as being deposited in an anoxic, or oxygen-depleted, deep water environment, although the details of the depositional environment are the subject of debate by researchers of the formation.[7][9]
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