{{Short description|Early Jurassic geological formation of south-western Germany}} {{Copy edit|date=October 2025}} {{Infobox rockunit | name = Sachrang Formation | image = Posidonienschiefer.jpg | caption = Posidonia Shale (''Posidonienschiefer'') Outcrop | type = Geological formation | age = Early-Late Toarcian<ref name=Astrono>{{cite journal |last1=Ruebsam |first1=W. |last2=Schmid-Röhl |first2=A. |last3=Al-Husseini |first3=M. |title=Astronomical timescale for the early Toarcian (Early Jurassic) Posidonia Shale and global environmental changes |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |date=2023 |volume=623 |article-number=111619 |doi=10.1016/j.palaeo.2023.111619 |bibcode=2023PPP...62311619R |s2cid=258545235 |url=https://www.sciencedirect.com/science/article/pii/S0031018223002377 |access-date=10 July 2023|url-access=subscription }}</ref><ref name=LateToarc>{{cite journal |last1=Burnaz |first1=L. |last2=Littke |first2=R. |last3=Grohmann |first3=S. |title=Lower Jurassic (Pliensbachian–Toarcian) marine paleoenvironment in Western Europe: sedimentology, geochemistry and organic petrology of the wells Mainzholzen and Wickensen, Hils Syncline, Lower Saxony Basin |journal=Int J Earth Sci |date=2024 |volume=113 |issue=1 |pages=1999–2022 |doi=10.1007/s00531-023-02381-8 |doi-access=free |bibcode= 2024IJEaS.113.1999B}}</ref><br />~{{fossilrange|184|178}}{{period fossil range|Jurassic|184|178}}<small>Possible Latest Pliensbachian records<ref name=vulcanism>{{cite journal |last1=Neumeister |first1=S. |last2=Gratzer |first2=R. |last3=Algeo |first3=T. J. |last4=Bechtel |first4=A. |last5=Gawlick |first5=H. J. |last6=Newton |first6=R. J. |last7=Sachsenhofer |first7=R. F. |title=Oceanic response to Pliensbachian and Toarcian magmatic events: Implications from an organic-rich basinal succession in the NW Tethys |journal=Global and Planetary Change |date=2015 |volume=126 |pages=62–83 |doi=10.1016/j.gloplacha.2015.01.007 |bibcode=2015GPC...126...62N |url=https://www.sciencedirect.com/science/article/pii/S0921818115000235 |access-date=12 December 2023|url-access=subscription }}</ref></small> | period = Toarcian | prilithology = Black shale | otherlithology = Lime mudstone, nodular claystone | namedfor = The village of Sachrang, Bavaria | namedby = Jacobshagen | year_ts = 1965 | region = Western & Central Europe | country = Germany, Netherlands, Austria, Switzerland, France, Luxembourg | coordinates = | unitof = {{indented plainlist| *Altena Group (Netherlands) *Black Jurassic (Germany) *Northern Calcareous Alps (Austria) }} | subunits = {{indented plainlist| *Dactyliocerassandstein *Dörnten Member *Lehmhagen Member *Schistes bitumineux (Luxembourg) }} | underlies = {{indented plainlist| * Jurensismergel Formation (Germany) * Klaus Formation (Austria) * Marnes à Bifrons Formation (Luxembourg) * Glashütte Formation (Germany) * Werkendam Formation (Netherlands) }} | overlies = {{indented plainlist| * Aalburg Formation (Netherlands) * Amaltheenton Formation (Germany) * Scheibelberg Formation (Austria) * Wolgast Formation (Germany) }} | thickness = | extent = {{indented plainlist| *Northern Limestone Alps *North German basin *South German Scarplands }} | area = | location_ts = Border with Tyrol above Sachrang | coordinates_ts = {{coord|47.69|N|12.24|E|display=inline,title}}<ref>{{cite web |title=Typlokalität der Sachrang-Formation W von Sachrang |url=https://www.umweltatlas.bayern.de/standortauskunft/rest/reporting/sb_geotope/generate/Geotope.pdf?additionallayerfieldvalue=187A014|access-date=31 January 2024}}</ref> | map = {{Location map+ | Germany | relief = 1 | width = 250 | float = center | places = {{Location map~ | Germany | lat_deg = 48.63 | lon_deg = 9.56 | mark = Blue pog.svg | marksize = 10 }} }} | map_caption = Holzmaden, location of the main Outcrop }} The '''Posidonia Shale''' ({{langx|de|'''Posidonienschiefer'''}}, also called '''Schistes Bitumineux''' in Luxembourg) geologically known as the '''Sachrang Formation''', is an Early Jurassic (Early to Late Toarcian) geological formation in Germany, northern Switzerland, northwestern Austria, southern Luxembourg and the Netherlands, including exceptionally well-preserved complete skeletons of fossil marine fish and reptiles.<ref name="Switz1">{{Cite journal |last1=Etter |first1=Walter |last2=Kuhn |first2=Olivier |date=2000 |title=An Articulated Dragonfly (Insecta, Odonata) From The Upper Liassic Posidonia Shale Of Northern Switzerland |journal=Palaeontology |volume=43 |issue=5 |pages=967–977 |doi=10.1111/1475-4983.00157 |bibcode=2000Palgy..43..967E |s2cid=140165815 |issn=0031-0239}}</ref><ref name="Luxembourg1">{{Cite journal |last1=Henrotay |first1=M. |last2=Marques |first2=D. |last3=Paicheler |first3=J. C. |last4=Gall |first4=J. C. |last5=Nel |first5=A. |date=1998 |title=Le Toarcien inférieur des régions de Bascharage et de Bettembourg (grand-duché du Luxembourg): évidences paléontologiques et sédimentologiques d'environnements restreints proches de l'émersion |url=https://sciencepress.mnhn.fr/sites/default/files/articles/pdf/g1998n2a4.pdf |journal=Geodiversitas |volume=20 |issue=2 |pages=263–284}}</ref><ref name="EFP2001">{{Cite book |last1=Clements |first1=Thomas |last2=Gabbott |first2=Sarah |title=Encyclopedia of Life Sciences |chapter=Exceptional Preservation of Fossil Soft Tissues |date=2022-04-13 |pages=1–10 |doi=10.1002/9780470015902.a0029468|isbn=978-0-470-01617-6 }}</ref>

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.<ref name="NewName">{{Cite journal |last=Mönnig |first=Eckhard |date=2018 |title=Der Jura in der Stratigraphischen Tabelle von Deutschland (STD 2016) |url=https://bib.telegrafenberg.de/fileadmin/bib/pdf/Verlag/STD2016.pdf |journal=Newsletters on Stratigraphy |volume=41 |issue=1–3 |pages=253–261 |doi=10.1127/0078-0421/2005/0041-0253 |issn=0078-0421}}</ref> 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''.<ref name=NewName/> The type profile is still located on Dotternhausen.<ref name=NewName/>

The formation comprises finely laminated layers of oil shales formed of fine-grained sediments intercalated with bituminous limestones and crops out in several locations in southwestern Germany, although most remains are from near the village of Holzmaden and Dotternhausen.<ref name=EFP2001 /> 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.<ref name=EFP2001 /><ref>{{Cite journal |last=Brenner |first=K. |date=1978 |title=New aspects about the origin of the Toarcian Posidonia Shales |url=https://cir.nii.ac.jp/crid/1573105976303104256 |journal=Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen |volume=157 |issue=3 |pages=11–18|doi=10.1127/njgpa/157/1978/11 |bibcode=1978NJGPA.157...11B |url-access=subscription }}</ref>

== Geology == thumb|Posidonia slate - outcrop of the Black Jura near Hetzles|247x247px

The Posidonia Shale was originally referred to as the Schwarzjura Lias, which was first recovered from the Franconian Jura, which borders to the northeast on the Obermainisches Hügelland and the Oberpfälzisch-Obermainisches Hügelland, tectonically part of the Faulkschollenland. The recovered Franconian Jura rocks lie west of the Saxothuringian basement, bordering the Franconian Line. It is recovered laterally extensive within Germany belonging to the early Toarcian Central European Epicontinental Basin, that evolved gradually from low tophography tidal flat to floodplains to a shallow shelf sea with intermittent N connection with the Viking Corridor and the Proto-Atlantic Ocean and with the Tethys Ocean towards the S, that filled with seawater the area, subdivided in several subasins with heterogeneous conditions and biotas, from the Netherlands to the Tirol Area.<ref name=":0">{{Cite journal |last=Ziegler |first=P.A. |date=1982 |title=Geological Atlas of Western and Central Europe |url= |journal=Amsterdam, Shell International Petroleum Maatschappij |volume=22 |issue=2 |pages=145–146 |doi= |issn=}}</ref> The CEB stablished a relatively shallow transcontinental seaway between the Tethyan and Boreal Arctic Sea biota, thus mixing cold and hot waters.<ref>{{Cite journal |last1=Bjerrum |first1=Christian J. |last2=Surlyk |first2=Finn |last3=Callomon |first3=John H. |last4=Slingerland |first4=Rudy L. |date=2001 |title=Numerical paleoceanographic study of the Early Jurassic Transcontinental Laurasian Seaway |journal=Paleoceanography |volume=16 |issue=4 |pages=390–404 |doi=10.1029/2000pa000512 |bibcode=2001PalOc..16..390B |s2cid=128465643 |issn=0883-8305 |url=https://discovery.ucl.ac.uk/id/eprint/188170/ }}</ref><ref name=":3">{{cite book |last1=RÖHL |first1=H.-J. |chapter=Lower Toarcian (Upper Liassic) Black Shales of the Central European Epicontinental Basin: A Sequence Stratigraphic Case Study from the Sw German Posidonia Shale |date=2005 |title=Deposition of Organic-Carbon-Rich Sediments: Models |pages=165–189 |publisher=SEPM (Society for Sedimentary Geology) |last2=SCHMID-RÖHL |first2=A.|doi=10.2110/pec.05.82.0165 |isbn=1-56576-110-3 }}</ref> The Mesozoic was marked by the breakup of Pangea during the Late Triassic, which led to the appearance of the early Atlantic connecting with the Boreal waters of the Panthalassa Ocean, and several marine to continental subasins locally.<ref name=":0" /> The CEB was part of the Laurasian continental-marine shelf that, resting over the Keuper, slowly opened towards the southeast into the deeper Tethys Ocean. With the flooding in the Early Jurassic by marine waters, several islands, submarine sills, and deeper subbasins developed, which contributed to and controlled the evolution of the paleocurrents.<ref name=":0" />

Towards the W is determined by the north–south Kilberg Fault of the Keilberg Rift, the main fault in the Regensburg Basin.<ref name="Bauberger2">{{cite journal |last1=FREUDENBERGER |first1=WALTER |last2=CHWERD |first2=KLAUSS |title=Erläuterungen zur Geologischen Karte von Bayern 1:500000 |journal=Geol. Kt. Bayern 1:500000 |date=1996 |volume=329 |pages=1–368 |url=https://www.bestellen.bayern.de/application/applstarter?APPL=eshop&DIR=eshop&ACTIONxSETVAL(artdtl_geo.htm,APGxNODENR:203255,AARTxNR:10000,AARTxNODENR:203256,USERxBODYURL:artdtl.htm,KATALOG:StMUG,AKATxNAME:StMUG,ALLE:x)=X |access-date=12 December 2023}}</ref> Developed by the sinking of the southern German Jura Plateau during the Miocene, it separates the higher, older crystallization of the Moldanubian Basement from the Lower Jurassic chalk complex of the eastern Franconian Jura.<ref name="Geolo22">{{Cite journal |last1=Brunotte |first1=Ernst |last2=Garleff |first2=Karsten |last3=Jordan |first3=Heinz |date=1985-12-01 |title=A Geomorphological Map to Accompany Sheet 4325 (Nörten-Hardenberg) of the 1: 25 000 Geological Map of Lower Saxony |journal=Zeitschrift der Deutschen Geologischen Gesellschaft |volume=136 |issue=1 |pages=277–285 |doi=10.1127/zdgg/136/1985/277 |issn=0012-0189}}</ref> During the late Pliensbachian, the zone became a relatively narrow, flat deposit area which flooded during the early Toarcian and reemerged during the Bifrons substage with a changing coastline, thanks to rhythmic uplifts and subsidence of older Paleozoic and Triassic siliciclastic deposits from the east.<ref name="Geolo22" /> The granites and gneisses resulting from crystallization were eroded from the Paleozoic exposures on the east, and were deposited on the Jurassic prograded alluvial nearshore sandstone that evolved gradually into the Bajocian layers.<ref name="Geolo22" /> The slopes of the area are partially covered by till, soliflucted rubble and loess from the Würm glaciation.<ref name="Geolo22" />

== Stratigraphy == thumb|Lithostratigraphy of the Posidonia Shale in Germany|223x223px

The bituminous facies overlie the Pliensbachian, and are mostly clay marl to marl shales with an organic carbon content of over 2%, with some levels referred to as "bitumen-free" or "bitumen-poor".<ref name=":1">{{Cite book |last=Quenstedt |first=Fr. Aug. von |title=Das Flözgebirge Würtembergs: mit besonderer Rücksicht auf den Jura / von Fr. Aug. Quenstedt |date=1843 |publisher=H. Laupp'schen |location=Tübingen|doi=10.5962/bhl.title.45496 |url=https://www.biodiversitylibrary.org/item/98744 }}</ref> The lowermost sequence is known as Seegrasschiefer (seagrass slate), appearing just above the limit, being actively burrowed horizons, approximately 15–20&nbsp;cm thick with clay marl stone appear in the darker, brownish to gray, bituminous clay marl/marl slate.<ref name=":2">{{Cite journal |last=Hauff |first=Rolf B. |date=1921 |title=Untersuchung der Fossilfundstätten von Holzmaden im Posidonienschiefer des Oberen Lias Württembergs |url=https://www.schweizerbart.de/papers/palae/detail/64/67083/Untersuchung_der_FossilfundstxE4_tten_von_Holzmaden_im_Posidonienschiefer_des_oberen_Lias_WxFC_rttembergs |journal=Palaeontographica |volume=58 |issue=1–42 |pages=255–263 |doi= |issn=}}</ref> This initial horizons have abundant foraminifera and ostracods as the medium to light gray color without a brown tint.<ref name=":2" /> The Formation evolves from bottom to top: blue-gray marls of the uppermost Pliensbachian spinatum zone, being medium gray, pyrite-rich clay marl stones that are still part of the Amaltheenton Formation, which gradually wedge out to the east in the area of Aalen-Wasseralfingen. Towards the middle, they start to include thin, disturbed bituminous horizons found throughout southwest Germany. Gradually, the bioturbation of the seegrasschiefer merges into the subsequent ash-gray marls without a sharp facies boundary.<ref name=":1" /> The Aschgrauen Mergel (ash-gray marl) marks the start of the Posidonia Shale, made by dark gray marl, abundant in pyrite with bituminous marl slate intrusions. This horizon marks a sea transgression, as it extends from Asselfingen/Wutach to Aalen-Reichenbach and then wedges out to the east from Aalen-Wasseralfingen. This initial sequence is overlied by extremely thin (2–5&nbsp;cm), unnamed bituminous, seegrasschiefer clay marl, followed then by a darker layers with the same lithology.<ref name=":1" /> The next are the "Koblenzer-Hainzen" clay successions of the upper semicelatum subzone, initially poorly layered and more or less bituminous with abundance of ''Steirmannia radiata'' and ''Dactylioceras semieelatum''. This section is marked by pyritized lagerstätten fossils, which are limited to certain areas (Dotternhausen, Holzmaden), and is now well-layered and black-brown in color.<ref name=":2" /> The Unteren Schiefern layers (Exaratum) appear next, marked by the highest bitumen content and characterized by very fine light/dark stratification, abundance of pyrite, fine-grained weathering, and the largely absence of bioturbation derived from anoxic conditions, while the accumulation of exceptionally preserved fossils indicates very weak water movement.<ref name=":2" /> The next, Untere Stein, is the most important level of the formation, especially in southwest Germany, southern France, and Alsace-Lorraine. It appears across the area either as a concretionary "laibstein" horizon (Aalen region) or as a uniformly layered limestone bank (Wutach area), with ''Leptolepis coryphaenoides'' as the character fossil of this limestone bank.<ref name=":2" />

The Mittleren Schiefer/Schieferklotz (upper exaratum to lower elegans subzones) become increasingly poorly layered until it becomes a small brittle limestone bank, the "Stinkkalkbank" (Dotternhausen to Gomaringen and Nürtingen) with ''Coelodiscus'' shells, low on bitumen and with biota that marks better oxygenated conditions, such as foraminifera and occasional ostracods.<ref name=":1" /> The Obere and Wilder Stein (upper elegans) medium to brown-gray always remain formed as a regular limestone bank of approximately uniform thicknessis, rarely laminated (Dotternhausen) and often shows traces of minor bioturbation (Dotternhausen, Mössingen, Gomaringen; Aalen-Wasseralfingen), becoming calcified towards the upper limit between Nürtingen and Holzmaden, marked with increased presence of ''Cucullaea muensteri'' as well foraminifera and ostracods, as well scoria horizons with fish, cephalopod and larger vertebrate remains, as well often contain belemnite rostrums.<ref name=":1" /> The last level of the formation is the Wilden Schiefer (probably reaching Bifrons zone) with the presence of "Monotis bank", from Altdorf to Dotternhausen and Göppingen area, with slates getting poorer in bitumen and less layered. The top section is known as "bollensis camp", marked by the mass deposition of ''Bositra buchi'', closed at the top by a new seegrasschiefer. The limit with the Jurensismergel Formation is mostly eroded in profiles, evolving into marlstones.<ref name=":1" /> Several outcrops, mostly in the NW (ex. Harz hills), show that relict levels of the Posidonienschiefer lasted until the Upper Toarcian, contemporaneous with the Jurensismergel Fm, known as "Dörntener Schiefer".<ref name="LateToarc" />

=== Sachrang === The Sachrang Shales were originally cited in the restudy of the Alpine Upper Black Slate, composed of dark gray, somewhat sandy, disintegrating into thin but large plates of Marl that overlies Pliensbachian breccia. The definition of the Sachrang Shales has been convoluted throughout the history of studies at the location, where works on the North Alpine Mesozoic have preferred to call these deposits the Sachranger Shale to give them a brief, different diagnosis.<ref name="Tollman">{{Cite journal |last=GLAESSNER |first=M |date=1977 |title=Analyse des klassischen nordalpinen Mesozoikums. Stratigraphie, fauna und fazies der no¨rdlichen kalkalpen |journal=Earth-Science Reviews |volume=13 |issue=2 |pages=192–194 |doi=10.1016/0012-8252(77)90023-x |bibcode=1977ESRv...13..192G |issn=0012-8252}}</ref> On the Unken Syncline near Lofen, basinal deposits with abundant Aragonite and Calcite helped to know the major Jurassic basin geometry, where on several layers of the same age was complicated due to the posterior Alpine deformation.<ref name="paleom">{{Cite journal |last1=Channell |first1=J. E. T. |last2=Brandner |first2=R. |last3=Spieler |first3=A. |last4=Stoner |first4=J. S. |date=1992 |title=Paleomagnetism and paleogeography of the northern calcareous Alps (Austria) |journal=Tectonics |volume=11 |issue=4 |pages=792–810 |doi=10.1029/91tc03089 |bibcode=1992Tecto..11..792C |issn=0278-7407}}</ref> Correlated Unken and Diessbach basins developed mostly during the Toarcian, with deposition of abundant material from the near Emerged Landmasses.<ref name="paleom" /> On the Unken Syncline, the breccias associated with the normal faults were deposited until Oxfordian age.<ref name="paleom" />

== Lithology == The black shales are the main part of the strata present, with a major bacterial component. The shale is made represent blackish gray to dark brown bituminous, fine-leaved, somewhat sandy marl slate, that lies on the profile of the strata, alternated with storage light brown (max. 4&nbsp;mm) and darker layers (rarely over 2&nbsp;mm) characteristic.<ref name=Tollman/> The lighter layers present in the rock get darker while it keeps its fine-plate character.<ref name=Tollman/> The Shale has a Dark-Gray to brownish tone, alternated with more rarely light gray shades.<ref name="EBLIA">{{cite journal |last1=Ebli |first1=O. |last2=Draxler |first2=I. |last3=Klein |first3=P. |last4=Kodina |first4=L. A. |last5=Lobitzler |first5=H. |title=Fazies, Paläontologie und organische Geochemie der Sachranger Schiefer (Untertoarcium) im Mittelabschnitt der Nördlichen Kalkalpen zwischen Isar und Saalach |journal=Jahrbuch der Geologischen Bundesanstalt |date=1991 |volume=134 |issue=1 |pages=5–14 |url=https://www.zobodat.at/pdf/JbGeolReichsanst_134_0005-0014.pdf |access-date=13 December 2023}}</ref> Blue fittings are relatively common, as are wood and fish remains (bones and scales).<ref name=Tollman/> The younger strata with the fresh outcrops develops on a series of several meters thick wall, that splits into fine paper Slates when weathered.<ref name=Tollman/> The Slate is among the most common mineral on the strata, with an average lime content of 40.2%, where maximum values are at 58% and minimum values at 26%.<ref name=Tollman/> Bituminous Claystones are present in the Edge facies of the Sachrang Shale (="Unken Shales"), with green Clay march engagements.<ref name=Tollman/> There is no clear separation between "Manganese Shale" and "Bituminous shale" in the main localities of the formation, because the Bituminous content fluctuates with the manganese content, which is always high. The Unken Shales on the Bächental locality is layered on a major Silicate component of the 60% with a pronounced dominance of Illite, along with a significant amount of Montmorillonite.<ref name=EBLIA/> The presence of Quartz and Calcite is relative with other locations of the same region from also the Toarcian, while the Pyrite content is also consistently high. Finally, the Unken Shale samples also show minor levels of Dolomite and Feldspar.<ref name=Tollman/> There is a great abundance of Foraminiferans and Coccoliths.<ref name=Eblib>{{cite journal |last1=Ebli |first1=O. |title=Foraminiferen und Coccolithen aus den Lias-Epsilon-Schiefern der Unkener Mulde (Tirolikum, Nördliche Kalkalpen) |journal=Mitt. Bayer. Staatsslg. Paläont. Hist. Geol |date=1989 |volume=29 |issue=1 |pages=61–83 |url=https://www.zobodat.at/pdf/Mitt-Bayer-Staatsslg-Pal-hist-Geol_29_0061-0083.pdf |access-date=3 March 2022}}</ref> Dinoflagellates are the major organic component and the most abundant microfossils.<ref name="Ebli">{{Cite journal |last1=Ebli |first1=Oskar |last2=Vető |first2=István |last3=Lobitzer |first3=Harald |last4=Sajgó |first4=Csanád |last5=Attila Demény |last6=Hetényi |first6=Magdolna |date=1998 |title=Primary productivity and early diagenesis in the Toarcian Tethys on the example of the Mn-rich black shales of the Sachrang Formation, Northern Calcareous Alps |journal=Organic Geochemistry |volume=29 |issue=5–7 |pages=1635–1647 |bibcode=1998OrGeo..29.1635E |doi=10.1016/s0146-6380(98)00069-2 |issn=0146-6380}}</ref> Manganese is present, such as in the Toarcian deposits of Hungary. Those are completed by the marl levels, composed of lithoclasts. quartz and smectite are the main minerals, along with illite, chlorite, and plagioclase in minor amounts. Bächental bituminous marls consist mainly of quartz and carbonate minerals.<ref name="quimic1">{{Cite journal |last1=Suan |first1=Guillaume |last2=Schlögl |first2=Jan |last3=Mattioli |first3=Emanuela |date=2016-08-01 |title=Bio- and chemostratigraphy of the Toarcian organic-rich deposits of some key successions of the Alpine Tethys |journal=Newsletters on Stratigraphy |volume=49 |issue=3 |pages=401–419 |doi=10.1127/nos/2016/0078 |bibcode=2016NewSt..49..401S |issn=0078-0421}}</ref> Isorenieratene derivatives are highly abundant on this level, related to several processes such as sedimentary iron, influenced by anoxic conditions.<ref name="IronA">{{Cite journal |last1=Reinhardt |first1=M. |last2=Duda |first2=J.-P. |last3=Blumenberg |first3=M. |last4=Ostertag-Henning |first4=C. |last5=Reitner |first5=J. |last6=Heim |first6=C. |last7=Thiel |first7=V. |date=2018-03-22 |title=The taphonomic fate of isorenieratene in Lower Jurassic shales—controlled by iron? |journal=Geobiology |volume=16 |issue=3 |pages=237–251 |doi=10.1111/gbi.12284 |pmid=29569335 |bibcode=2018Gbio...16..237R |s2cid=4907374 |issn=1472-4677}}</ref> Rhodochrosite and manganese rich calcite are present in the manganese levels, while the Black Shale levels are rich in Pirite.<ref name=Ebli/> The lower matrix is composed by clay and carbonate minerals, such as muscovite and feldspar. The presence of altered Celadonite, suggest volcanogenic solutions as the most probable source, where the high amounts of dissolved manganese of continental origin was translated to the epicontinental margins of the Tethys.<ref name=quimic1/> On the ''Bächental bituminous marls'' had a bulk mineralogy where the Calcite is the most abundant fraction (49%), followed by Phyllosilicates (35%), Quartz (11%) and Pyrite (5%). While the Clay mineral distribution includes a large amount of Illite (51%), Montmorillonite (40%) and Kaolinite (9%).<ref name="Tollman" />

== Dating == thumb|right|The former marl pit of Hondelage, NW Germany. At the bottom of the image there is an {{convert|8|m|ft|abbr=on|adj=mid|-long}} stretch of Posidonia Shale exposed.

Based on sedimentological and palynological features, a tidally influenced transgressive development within the Lower Toarcian is inferred, with increased continental matter transported to marine areas, causing anoxic conditions; the Posidonia Shale is the reference formation for this interval. The Posidonia Shale of Dotternhausen and Schesslitz is well dated on the basis of ammonite and microfossil biostratigraphy. The Lower Toarcian sections are subdivided into three ammonite biozones (''Dactyloceras tenuicostatum'', ''Harpoceras falciferum'', and ''Hildoceras bifrons'') and several subzones.<ref name=":3" /> On the other hand, Black shale formation in the Toarcian of NW Germany is associated with a major turnover in phytoplankton assemblages interpreted as the response to lowered salinities in surface waters of the epicontinental sea. The presence of the Turnover is essential for the datation and the preservation of the fauna of the formation, with detailed index ammonites preserved.<ref>{{cite book |last1=Riegel |first1=Walter |chapter=Effects and causes in a black shale event — the Toarcian Posidonia Shale of NW Germany |title=Global Bio-Events |pages=267–276 |place=Berlin/Heidelberg |publisher=Springer-Verlag |isbn=3-540-17180-0 |last2=Loh |first2=Hartmut |last3=Maul |first3=Bernd |last4=Prauss |first4=Michael|series=Lecture Notes in Earth Sciences |date=1986 |volume=8 |doi=10.1007/bfb0010214 }}</ref> The study of the different layers and strata of the Posidonia Shale has given different data about the chronology of the formation. Dormettingen shales have been calculated biochronologically and with isochron data, giving an approximate age of 183-181 million years, being close to the Pliensbachian boundary based on the recent revisions of the Early Jurassic Subperiods.<ref name="Acken2019">{{Cite journal |last1=van Acken |first1=D. |last2=Tütken |first2=T. |last3=Daly |first3=J.S. |last4=Schmid-Röhl |first4=A. |last5=Orr |first5=P.J. |date=2019 |title=Rhenium‑osmium geochronology of the Toarcian Posidonia Shale, SW Germany |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=534 |article-number=109294 |doi=10.1016/j.palaeo.2019.109294 |bibcode=2019PPP...53409294V |s2cid=201318850 |issn=0031-0182}}</ref> The Toarcian and the Pliensbachian are considered as strongly constrained in terms of chronology, where the deposition has been estimated to have lasted 3.2&nbsp;Myr in the South Germany Basin, with the uppermost sequences estimated to be Bifrons in age.<ref name=Astrono/> The Posidonienschiefer lasts until the Late Toarcian (Variabilis Biozone) in the NW German Basin with the "Dörntener Schiefer", while it mostly disappears in the SW, substituted by the Jurensismergel Fm, with few deposits where it lasts (Wutach area, Nürtingen).<ref name=LateToarc/>

== History == thumb|Friedrich August von Quenstedt, a German mineralogist who studied the jurassic strata along Germany, including the Black Shales of the Posidonia Shale|196x196px

The Posidonia Shale has been a focus of scientific interest for the last 100 years. The first fossils were recorded in 1598 by the medical doctor Johannes Bauhin, who interpreted the local ammonites as "metallic things" in rocks and as "miraculous tricks" of nature, while the crinoids were interpreted as either huge flowers or heads of medusa, and evidence of the biblical flood.<ref name="His">{{cite book |last=Hess |first=Hans |chapter=Lower Jurassic Posidonia Shale of Southern Germany |date=1999-10-28 |title=Fossil Crinoids |pages=183–196 |publisher=Cambridge University Press|doi=10.1017/cbo9780511626159.025 |isbn=978-0-521-45024-9 }}</ref> Many people did important geological and paleontological research on the Swabian Posidonia Shale, including Carl Hartwig von Zieten (1785–1846), Eberhard Fraas (1862–1915), Bernhard Hauff senior (1866–1950) and Adolf Seilacher (1925–2014).<ref name=His/>

The first geological studies were carried out, motivated by shale extraction at the southern quarries. Several fossils were reported, studied and named at the time from locations such as Banz Abbey, Ohmden, Holzmaden or Dotternhausen, including ''Macrospondylus'' in 1824 (As ''Steneosaurus'', being originally identified as a Gharial), the pterosaur ''Dorygnathus'' (as a species of ''Pterodactylus'') in 1830, the fish ''Lepidotes'', the selachian ''Hybodus'' or the crinoid ''Pentacrinites''.<ref>{{cite book |last1=Wurstemberger |first1=A. R. |title=Über lias epsilon |date=1876 |publisher=Schweizerbart |url=https://books.google.com/books?id=fN5EAAAAYAAJ&dq=+%C3%9Cber+lias+epsilon&pg=PA5 |access-date=27 January 2024}}</ref> The first insight into the flora was done in 1845, with partial leaf fragments.<ref>{{cite journal |last1=Kurr |first1=J. G. |title=Beiträge zur fossilen Flora der Juraformation Württembergs |journal=Gedruckt in der Guttenberg'schen Buchdr |date=1845 |url=https://www.biodiversitylibrary.org/bibliography/6129 |access-date=27 January 2024}}</ref> Boué in 1829 did a study of the general geology of the Jurassic along Germany, recovering limestone and shale facies, with a superficial assignation of what he considered most of the main Jurassic Strata, without classifying the layers on a concrete subperiod.<ref>{{cite book |last1=Boué |first1=A. |title=Geognostisches Gemälde von Deutschland: mit Rücksicht auf die Gebirgs-Beschaffenheit nachbarlicher Staaten: mit acht Steindruck-Tafeln. |date=1829 |publisher=Hermann'sche Buchhandlung |url=https://books.google.com/books?id=7o1OAAAAcAAJ&dq=Geognostisches+gem%C3%A4lde+von+Deutschland%3A+Mit+r%C3%BCcksicht+auf+die+gebirgs-beschaffenheit+nachbarlicher+staaten&pg=PR1 |access-date=27 January 2024}}</ref> Further geological work was then carried out, recovering examples of marine facies representing various biomes, all associated with black shale deposits in other areas, as towards the NW or at Regensburg.<ref name=":1"/> The main work that described the facies formally was Quenstedt´s 1843 one, classifying the levels based on the amount of bitumen, providing a preliminary stratigraphy and lithology, which would be the basis for most subsequent works.<ref name=":1"/>

In the 1900s, major paleontological addons included the description of ''Stenopterygius'' in 1904 (as ''Ichthyosaurus'').<ref>{{cite journal |last1=Jaekel |first1=O. |title=Eine neue Darstellung von Ichthyosaurus|journal=Zeitschrift der deutschen geologischen Gesellschaft |date=1904 |pages=26–34 |url=https://www.schweizerbart.de/papers/zdgg_alt/detail/56/66040?l=EN |access-date=27 January 2024}}</ref> While in 1921, the 1st major fossil inventory was done by Hauff, reporting exquisite specimens, most of them from Holzmaden and some of them nearly complete, including Ammonites, Fish and Marine reptiles, such as Plesiosaurs and Icthyosaurs.<ref name=Hauff21>{{cite journal |last1=Hauff |first1=B. |title=Untersuchung der Fossilfundstätten von Holzmaden im Posidonienschiefer des Oberen Lias Württembergs |journal=Palaeontographica |date=1921 |pages=1–42 |url=https://www.schweizerbart.de/papers/palae/detail/64/67083/Untersuchung_der_Fossilfundstatten_von_Holzmaden_im_Posidonienschiefer_des_oberen_Lias_Wurttembergs |access-date=27 January 2024}}</ref> Hauff described in 1938 "Acidorhynchus" (''Saurorhynchus''), the latest surviving of the Saurichthyiformes.<ref>{{cite journal |last1=Hauff |first1=B. |title=Über Acidorhynchus aus den Posidonienschiefern von Holzmaden |journal=Paläontologische Zeitschrift |date=1938 |volume=20 |issue=2 |pages=214–248 |doi=10.1007/BF03041918 |bibcode=1938PalZ...20..214H |s2cid=128821484 |url=https://link.springer.com/article/10.1007/BF03041918 |access-date=27 January 2024|url-access=subscription }}</ref> In 1953, an impressive Insect fauna was revised in the Northern outcrops.<ref name="Bode">{{cite journal |last1=Bode |first1=A. |title=Die Insektenfauna des Ostniedersachsischen Oberen Lias |journal=Palaeontographica Abteilung A |date=1953 |volume=103 |issue=1 |pages=1–375 |url=https://lacewing.tamu.edu/neuropterida/neur_bibliography/edoc12/bode1953ref1603-6712.pdf |access-date=2 March 2022}}</ref> On 1978, Wild described the First and only know Dinosaur Fossil from the formation, what he named ''Ohmdenosaurus'', a small sized Sauropod.<ref name=Ohmdeno>{{cite journal |last1=Wild |first1=R. |title=Ein Sauropoden-Rest (Reptilia, Saurischia) aus dem Posidonienschiefer (Lias, Toarcium) von Holzmaden |journal=Stuttgarter Beiträge zur Naturkunde, Serie B (Geologie und Paläontologie) |date=1978 |volume=41 |issue=2 |pages=1–15}}</ref> Latter works revisited the exceptional preservation of the biota, especially the presence of soft parts.<ref>{{cite journal |last1=Urlichs |first1=M. |last2=Wild |first2=R. |last3=Ziegler |first3=B. |title=Fossilien aus Holzmaden |journal=Stuttgarter Beiträge zur Naturkunde, Serie C |date=1986 |volume=11 |pages=1–34}}</ref> The lithology and sedimentology of the formation was revisited, with several suggestions such as stagnant basin models and restricted open marine ones, all suggested to be deposited on a shallow epicontinental sea.<ref name=Hauff21/> The abundance of organic matter and the composition of the shales, chemically or lithologically, went under diverse renoved works.<ref>{{cite journal |last1=Kroepelin |first1=H. |last2=Wurziger |first2=J. |title=Zur Kenntnis der organischen Substanz des Posidonienschiefers. I. Untersuchungen über den Stickstoffgehalt |journal=Abhandlungen der Braunschweigischen Wissenschaftlichen Gesellschaft|date=1949 |issue=1 |pages=28–32 |url=https://leopard.tu-braunschweig.de/servlets/MCRFileNodeServlet/dbbs_derivate_00026876/Kroepelin_Wurziger_Posidonienschiefer.pdf |access-date=27 January 2024}}</ref><ref>{{cite journal |last1=Blumer |first1=M. |title=Porphyrinfarbstoffe und Porphyrin-Metallkomplexe in schweizerischen Bitumina |journal=Geochemische Untersuchungen V. Helvetica Chimica Acta |date=1950 |volume=33 |issue=6 |pages=1627–1637|doi=10.1002/hlca.19500330630 }}</ref> With the addition of multiple new references, the expansion of information thanks to the revision of profiles, boreholes and other outcrops, new works on the characteristics of the deposition, the type of environment and the conditions that led to the exquisite preservation were produced, where paleocurrents where found to be nfluenced from the north and the south of the Central European Basin.<ref>{{cite journal |last1=Kauffman |first1=E.G. |title=Ecological reappraisal of the German Posidonienschiefer (Toarcian) and the stagnant basin model |journal=Communities of the Past |date=1981 |volume=3 |pages=311–381}}</ref> The Black shale deposition was found to be related with changues in the oxygen levels.<ref>{{cite journal |last1=Savrda |first1=C. E. |last2=Bottjer |first2=D. J. |title=Anatomy and implications of bioturbated beds in" black shale" sequences: Examples from the Jurassic Posidonienschiefer (southern Germany) |journal=PALAIOS |date=1989 |volume=4 |issue=4 |pages=330–342 |doi=10.2307/3514557 |jstor=3514557 |bibcode=1989Palai...4..330S }}</ref> Thanks to the renewed information, a new cycle of publications reviewing the microfacies took place between 1980-1990.<ref>{{cite journal |last1=Seilacher |first1=A. |title=Die Holzmadener Posidonienschiefer Entstehung der Fossillagerstätte und eines Erdölmuttergesteins |journal=Klassische Fundstellen der Paläontologie |date=1990 |volume=2 |pages=107–131 |url=https://www.leo-bw.de/web/guest/detail/-/Detail/details/DOKUMENT/wlbblb_labi/1266663/Die+Holzmadener+Posidonienschiefer++Entstehung+der+Fossillagerst%C3%A4tte+und+eines+Erd%C3%B6lmuttergesteins |access-date=27 January 2024}}</ref> The most important works of the XX century where done by Riegraf in 1985-86, being a complete review of all aspects of this formation, updating multiple points based on all the information compiled throughout the century: lithology, stratigraphy, biota list and ammonite biozonation, followed by a focused work on a complete mapping of the microfacies composition and extent of the shale deposits.<ref name="MAJORFos"/>

In the 2000s, the Posidonienschiefer has seen a series of studies focused on enriching the information previously examined in depth and revising and updating the depositional models.<ref name=":3"/> Likewise, the biota has received multiple updates, with the reclassification of some taxa and the discovery of new ones, as well a revision of the biotic interactions.<ref name=MainInteractions>{{cite journal |last1=Maxwell |first1=Erin E. |last2=Cooper |first2=Samuel L. A. |last3=Mujal |first3=Eudald |last4=Miedema |first4=Feiko |last5=Serafini |first5=Giovanni |last6=Schweigert |first6=Günter |title=Evaluating the Existence of Vertebrate Deadfall Communities from the Early Jurassic Posidonienschiefer Formation |journal=Geosciences |date=2022 |volume=12 |issue=4 |pages=158–176 |doi=10.3390/geosciences12040158 |bibcode=2022Geosc..12..158M |doi-access=free |hdl=11380/1368001 |hdl-access=free }}</ref>

== Paleogeography and paleoenvironment == thumb|Paleogeography of the Early Toarcian Central European Area, with close panoramic of the Hondelange & Schandelah outcrops and adjacent emerged lands|361x361px

The Posidonia Shale was located in the SW and NW Germanic basins, as part of a shallow epicontinental sea, and was surrounded and influenced by various highs and emerged lands that provided most of the terrestrial matter found within the Formation. The main outcrops of the formation are disposed along the modern southern Germany, recovering the locations of Holzmaden, Ohmden, as well as Niedersachsen, and others appearing along the east, such as the strata related to the Banz Abbey strata or Regensburg.<ref name="MAJORFos"/> The deposition of the shales where delimited to several minibasins, including the Southwest German Basin, a hemipelagic deposit, with the influence of open sea currents from the north and the south, with an estimated water depth of 2–100 m, with few deeper shelf environments.<ref name=":3"/><ref name=structu>{{cite journal |last1=Böhm |first1=F. |last2=Brachert |first2=T. C. |title=Deep-water stromatolites and Frutexites Maslov from the early and Middle Jurassic of S-Germany and Austria |journal=Facies |date=1993 |volume=28 |issue=1 |pages=145–168 |doi=10.1007/bf02539734 |bibcode=1993Faci...28..145B |s2cid=129365360 |url=https://www.researchgate.net/publication/251225434 |access-date=2 March 2022}}</ref> Connected to the SW German basin where the Paris Basin, that recovered central France, with correlated sedimentation to the Shale deposition on Germany, also sharing a epicontinental sea, bordered by carbonate facies, specially towards the south.<ref>{{cite journal |last1=Tissot |first1=B. |last2=Califet-Debyser |first2=Y. |last3=Deroo |first3=G. |last4=Oudin |first4=J. L. |title=Origin and evolution of hydrocarbons in early Toarcian shales, Paris Basin, France |journal=AAPG Bulletin |date=1971 |volume=55 |issue=12 |pages=2177–2193 |doi=10.1306/819A3E2E-16C5-11D7-8645000102C1865D |bibcode=1971BAAPG..55.2177T |url=https://pubs.geoscienceworld.org/aapgbull/article-abstract/55/12/2177/35593/Origin-and-Evolution-of-Hydrocarbons-in-Early |access-date=27 January 2024}}</ref> At the north, the Wenzen Well report little deeper basinal settings, heavily influenced by continental matter coming from the main continental land present anywhere nearby the formation, Fennoscandia.<ref name="Littke1">{{cite journal |last1=Littke |first1=R. |last2=Leythaeuser |first2=D. |last3=Rullkötter |first3=J. |last4=Baker |first4=D. R. |title=Keys to the depositional history of the Posidonia Shale (Toarcian) in the Hils Syncline, northern Germany |journal=Geological Society, London, Special Publications |date=1991 |volume=58 |issue=1 |pages=311–333 |doi=10.1144/GSL.SP.1991.058.01.20 |bibcode=1991GSLSP..58..311L |s2cid=129097635 |url=https://www.lyellcollection.org/doi/abs/10.1144/GSL.SP.1991.058.01.20 |access-date=27 January 2024|url-access=subscription }}</ref> In this area, the main emerged units present was the Rhenish High at the west, being a small land of the size of Sicily, and on the east, the N Bohemian Massif.<ref name=MainNORTH>{{cite journal |last1=Arp |first1=G. |last2=Balmuk |first2=Y. |last3=Seppelt |first3=S. |last4=Reimer |first4=A. |title=Biostratigraphy and sedimentary sequences of the Toarcian Hainberg section (Northwestern Harz foreland, Northern Germany) |journal=Zitteliana |date=2023 |volume=97 |pages=1–27 |doi=10.3897/zitteliana.97.110677 |doi-access=free |bibcode=2023Zitte..97....1A |url=https://zitteliana.pensoft.net/article/110677/download/pdf/ |access-date=27 January 2024}}</ref> The Bohemian massif with the Southern Vindelician High represent the major emerged units present on the Central European basin on the Toarcian.<ref name="Littke1"/> The Vindelician Land/High has been represented as a peninsula to the Bohemian Massif, or an isolated landmass, that is due to its connections that had not been recovered in depth, being considered a mostly plain emerged sedimentary structure.<ref name="Littke1"/> Finally, the southernmost part of the formation, the SWGB was separated from the Tethys Ocean by a series of islands related with the Bern High (Allemanic Swell), forming the continuation of the Vindelician High being a small terrestrial setting with similar size to modern Sardinia, with nearby sections like the Salem paleo-swell.<ref name=":5">{{cite journal |last1=Aldinger |first1=H. |title=Die Palaeogeographie der schwäbischen Jurabeckens |journal=Geologisch-Paläontologisches Institut der Technischen Hochschule Stuttgart |date=1968|url=https://www.e-periodica.ch/cntmng?pid=egh-001%3A1968%3A61%3A%3A924 |access-date=27 January 2024}}</ref><ref>{{Cite journal |last1=Ajuaba |first1=Stephen |last2=Sachsenhofer |first2=Reinhard F. |last3=Galasso |first3=Francesca |last4=Garlichs |first4=Thorsten U. |last5=Gross |first5=Doris |last6=Schneebeli-Hermann |first6=Elke |last7=Misch |first7=David |last8=Oriabure |first8=Jonathan E. |date=2024-03-27 |title=The Toarcian Posidonia Shale at Salem (North Alpine Foreland Basin; South Germany): hydrocarbon potential and paleogeography |journal=International Journal of Earth Sciences |volume=113 |issue=8 |pages=2093–2130 |language=en |doi=10.1007/s00531-024-02392-z |issn=1437-3262|doi-access=free |bibcode= 2024IJEaS.113.2093A}}</ref>

left|thumb|293x293px|Pliensbachian–Toarcian plankton communities in the NGB

The Germanic Epicontinental sea is considered to be an analog, as it compares well to the sedimentation rate in deep-water settings, of the Black Sea.<ref>{{Cite journal |last1=Galasso |first1=F. |last2=Feist-Burkhardt |first2=S. |last3=Schneebeli-Hermann |first3=E. |date=2022 |title=Do spores herald the Toarcian Oceanic Anoxic Event? |journal=Review of Palaeobotany and Palynology |volume=306 |article-number=104748 |doi=10.1016/j.revpalbo.2022.104748 |bibcode=2022RPaPa.30604748G |s2cid=251499608 |issn=0034-6667}}</ref> Most of the outcrops (Holzmaden, Dotternhausen, Ohmden, or Dormettingen) represent low-energy depositional environments, far from deltaic sediment sources.<ref name=":3" /> The Toarcian epicontinental seas of Europe were driven by several global events and changes present on the surface, like the coeval Karoo-Ferrar eruptions in the Southern Hemisphere, which created an enhanced hydrological cycle & oxygen depletion, allowing exceptional preservation. This stage was marked with the presence of a general deposition of shale mudrock along with strong variations on the associated organic matter, associated with extincions such as the Toarcian Oceanic Anoxic Event.<ref name=":4">{{Cite journal |last1=Schmid-Röhl |first1=Annette |last2=Röhl |first2=Hans-Joachim |last3=Oschmann |first3=Wolfgang |last4=Frimmel |first4=Andreas |last5=Schwark |first5=Lorenz |date=2002 |title=Palaeoenvironmental reconstruction of Lower Toarcian epicontinental black shales (Posidonia Shale, SW Germany): global versus regional control |journal=Geobios |volume=35 |issue=1 |pages=13–20 |doi=10.1016/s0016-6995(02)00005-0 |bibcode=2002Geobi..35...13S |issn=0016-6995}}</ref> The black shales characteristic of this unit reveal a shallow marine environment, influenced by arctic and Tethyan waters, with marked episodes of disappearance of benthic biota. Also, measure a change in carbon-isotope excursion in marine and terrestrial life, and it was probably a perturbator of the carbon cycle.<ref>{{Cite journal |last=Brumsack |first=Hans-J. |date=1991 |title=Inorganic geochemistry of the German 'Posidonia Shale': palaeoenvironmental consequences |journal=Geological Society, London, Special Publications |volume=58 |issue=1 |pages=353–362 |doi=10.1144/gsl.sp.1991.058.01.22 |bibcode=1991GSLSP..58..353B |s2cid=129835129 |issn=0305-8719}}</ref> Global seawater has been proved to be approximately, for the interval of the negative carbon-isotope excursion, close to 1.45‰, less than modern values, with estimated 2.34‰. Waters interchange was one of the major effects on palatine de-oxygenation observed in most Lower Toarcian Layers worldwide, with the connection to the Viking Corridor as a key factor, due to Arctic waters freshening and disrupting oceanic circulation.<ref>{{Cite journal |last1=Dera |first1=Guillaume |last2=Donnadieu |first2=Yannick |date=2012 |title=Modeling evidences for global warming, Arctic seawater freshening, and sluggish oceanic circulation during the Early Toarcian anoxic event |journal=Paleoceanography |volume=27 |issue=2 |article-number=2012PA002283 |doi=10.1029/2012pa002283 |bibcode=2012PalOc..27.2211D |issn=0883-8305}}</ref> The effect was consequently negative on the German realm, where the environments expose a tropical fluctuation, with conditions similar to the modern Caribbean Sea, which hosted a high variety of sea fauna, except on the bottom layers, where only a few genera were able to survive until oxygen conditions got slightly better.<ref>{{Cite journal |last1=Dickson |first1=Alexander J. |last2=Gill |first2=Benjamin C. |last3=Ruhl |first3=Micha |last4=Jenkyns |first4=Hugh C. |last5=Porcelli |first5=Donald |last6=Idiz |first6=Erdem |last7=Lyons |first7=Timothy W. |last8=van den Boorn |first8=Sander H. J. M. |date=2017 |title=Molybdenum-isotope chemostratigraphy and paleoceanography of the Toarcian Oceanic Anoxic Event (Early Jurassic) |journal=Paleoceanography |volume=32 |issue=8 |pages=813–829 |doi=10.1002/2016pa003048 |bibcode=2017PalOc..32..813D |issn=0883-8305}}</ref> The changes on the benthic oxygen where common, with most of the animals dying without being scavenged by bottom-dweller organisms, and sessile life, with this biota limited to "benthic islands" associated with ammonite shells or vertebrate carcasses (Except some Polychaetans on higher oxygen conditions).<ref name=":4" /><ref name="MainInteractions" /> Towards the middle Toarcian show changes on the environment reflect more oxygenated waters and different depositional settings with the presence of trace fossils such as ''Chondrites'' and ''Phymatoderma granulata'', surfacing deposit-feeding animals, being adapted for effective nutrient searching, becoming more common on the uppermost layers, yet in some areas, the shale remained until the Late Toarcian.<ref>{{Cite journal |last=Izumi |first=Kentaro |date=2012 |title=Formation process of the trace fossil Phymatoderma granulata in the Lower Jurassic black shale (Posidonia Shale, southern Germany) and its paleoecological implications |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=353-355 |pages=116–122 |doi=10.1016/j.palaeo.2012.07.021 |bibcode=2012PPP...353..116I |issn=0031-0182}}</ref> Regressive sea levels mark the uppermost layers, as it is shown on layers across Bavaria where major events set the fate of the nearshore environments.<ref name="Monotis–Dactylioceras" /> One example is the case of the Monotis–Dactylioceras beds, that had an extent of +500&nbsp;km, that has been linked with a possible Tsunami. There is no major indication of synsedimentary faulting in South Germany, but it is present on the western Tethyan Shelf, with earthquake-generated breccias occurring on Toarcian levels of the Austrian Adnet Formation. It would start as an initial wave propagation affecting the Altdorf High, aiming for the south, where it would have hit the shoreline of the Bohemian Island.<ref name="Monotis–Dactylioceras">{{Cite journal |last1=Arp |first1=Gernot |last2=Gropengießer |first2=Sebastian |date=2015-06-09 |title=The Monotis–Dactylioceras Bed in the Posidonienschiefer Formation (Toarcian, southern Germany): condensed section, tempestite, or tsunami-generated deposit? |journal=PalZ |volume=90 |issue=2 |pages=271–286 |doi=10.1007/s12542-015-0271-7 |bibcode=2016PalZ...90..271A |s2cid=128091360 |issn=0031-0220 }}</ref>

[[File:Grimmen_Formation_distribution.png|thumb|239x239px|Simplified paleogeography of the NGB in the Toarcian, with the extent of the Grimmen Formation and adjacent units]] left|thumb|264x264px|Lehmhagen Member biota

The main terrestrial environments of the Posidonia Shale are the near emerged lands where the Black Forest High/Swell (known thanks to strata containing fine sand in the tenuicostatum Zone, 'Glaukonit und viel Feinsand', at Obereggenen im Breisgau), located at 70&nbsp;km at the west and the Ries Swell, W of Regensburg, then far towards the W the Vosges Massif is also suggested to be present (known by the abundant detrital quartz from the EST433 borehole located near Bure, Meuse).<ref name=":3" /><ref>{{Cite journal |last1=Lézin |first1=Carine |last2=Andreu |first2=Bernard |last3=Pellenard |first3=Pierre |last4=Bouchez |first4=Jean-Luc |last5=Emmanuel |first5=Laurent |last6=Fauré |first6=Philippe |last7=Landrein |first7=Philippe |date=2013 |title=Geochemical disturbance and paleoenvironmental changes during the Early Toarcian in NW Europe |journal=Chemical Geology |volume=341 |pages=1–15 |doi=10.1016/j.chemgeo.2013.01.003 |bibcode=2013ChGeo.341....1L |issn=0009-2541}}</ref> The Environments of these highs are assumed to have been through phases os aridity and humidy marked by the Toarcian Oceanic Anoxic Event based on Palynology.<ref name="PalyDor" /> In the east the SW German sub-basin was bounded by the Bohemian-Hercynian landmass (Modern Bohemian Massif), with the Vindelician peninsula at the S-SW, reaching the west area of Augsburg. Between the Hettangian-Toarcian, this threshold was perhaps temporarily connected via a land bridge with an island in the area of the Aarmassif.<ref>{{cite journal |last1=Trümpy |first1=R. |title=Hypothesen über die Ausbildung von Trias, Lias und Dogger im Untergrund des schweizerischen Molassebeckens |journal=Eclogae Geologicae Helvetiae |url=https://www.e-periodica.ch/digbib/view?pid=egh-001%3A1959%3A52%3A%3A519 |date=1959 |volume=52 |issue=2 |pages=435–448}}</ref> The Bohemian Massif was located in a relatively warm, precipitation-rich climate with Bavarian shallow areas receiving freshwater inflows from the east, which temporarily lowered the salinity of the seawater in the whole basin or in parts.<ref name=":5" /> The margins of the SWGB, as well as the hinterland relief, had very gentle topography, and therefore fine-grained siliciclastic sediments were easily transported and deposited in the nearshore area of the basin, as well as long transported driftwood, and the lack of insects or terrestrial vertebrates.<ref name=":5" /><ref name=":6">{{Cite journal |last1=Muscente |first1=A.D. |last2=Vinnes |first2=Olivia |last3=Sinha |first3=Sinjini |last4=Schiffbauer |first4=James D. |last5=Maxwell |first5=Erin E. |last6=Schweigert |first6=Günter |last7=Martindale |first7=Rowan C. |date=2023 |title=What role does anoxia play in exceptional fossil preservation? Lessons from the taphonomy of the Posidonia Shale (Germany) |journal=Earth-Science Reviews |volume=238 |article-number=104323 |doi=10.1016/j.earscirev.2023.104323 |issn=0012-8252|doi-access=free |bibcode=2023ESRv..23804323M }}</ref> In the south-eastern North-German Basin at Hondelange and Schandelah, the Posidonienschiefer was deposited in the "Oberaller Through", a local depression bordered by the emerged "Calvörde Island" and the submerged Altmark Swell to the N, while the shallow submerged Fallstein Swell closed it at the south, and more towards the E the Bohemian Massif hosted a large delta that discharged towards Oberaller.<ref>{{Cite journal |last1=Marten |first1=Tim |last2=Ruebsam |first2=Wolfgang |last3=Mutterlose |first3=Jörg |last4=Wiesenberg |first4=Guido L. B. |last5=Schwark |first5=Lorenz |date=2024-06-27 |title=Latest Pliensbachian to Early Toarcian depositional environment and organo-facies evolution in the North-German Basin (Hondelage Section) |journal=International Journal of Earth Sciences |volume=113 |issue=8 |pages=2043–2064 |doi=10.1007/s00531-024-02433-7 |issn=1437-3254|doi-access=free |bibcode= 2024IJEaS.113.2043M}}</ref>

In Microfacies, after the Pliensbachian-Toarcian, a significant decrease in the Crinoid skeleton elements, also that of the Ophiurida; the Echinoids take their place, where they really blossomed at that time, while Pedicellaria are observed very often.<ref name="MAJORFos" /> On the bituminous marls, there is a great abundance of saturated Hydrocarbons in the hexanesoluble fraction, Methyl and Methylene, where found along long-chain paraffinic molecules (n-alkanes).<ref name="EBLIA" /> Benzenemethanol resins are especially strong for the Benzene-Methanol fraction.<ref name="Bachlitho">{{cite journal |last1=Kodina |first1=Lvudmila A. |last2=Bogatcheva |first2=M. P. |last3=Lobitzer |first3=H. |year=1988 |title=An Organic Geochemical Study of Austrian Bituminous Rocks |url=https://opac.geologie.ac.at/ais312/dokumente/JB1312_291_A.pdf |journal=Jb. Geol. B.-A. |volume=131 |issue=2 |pages=291–300}}</ref> The main maceral found is Lamalginite, which may derive from thin-walled planktonic and benthic organisms, including Green Algae, Cyanobacteria, and Bacterial mats. There is a clear low frequency of Vitrinite and Inertinite, which suggests that terrestrial inputs of organic matter are of less importance, although the main part of OM contained in the basal mudstone, including charred material, was derived from terrestrial sources. This Mudstone contains charred organic material, typically connected to wildfires, along with large amounts of expandable Smectite, possibly derived from alteration of volcanic ash, which indicates a clear contribution of volcanic-derived detritus during deposition.<ref name=":6" /> In the Austrian area, the volcanic materials where probably also sourced by the rift history of the Valais, {{ill|Briançonnais (natural region)|lt=Briançonnais|fr|Briançonnais}} and Piemonte-Liguria domains (Sinemurian-Callovian), and the Toarcian break-up of the Ligurian-Penninic oceanic realm.<ref>{{Cite journal |last1=Ratschbacher |first1=Lothar |last2=Dingeldey |first2=Christian |last3=Miller |first3=Christine |last4=Hacker |first4=Bradley R. |last5=McWilliams |first5=Michael O. |date=2004 |title=Formation, subduction, and exhumation of Penninic oceanic crust in the Eastern Alps: time constraints from <sup>40</sup>Ar/<sup>39</sup>Ar geochronology |journal=Tectonophysics |volume=394 |issue=3–4 |pages=155–170 |doi=10.1016/j.tecto.2004.08.003 |bibcode=2004Tectp.394..155R |issn=0040-1951}}</ref> There are measurements of the reduction of the local salinity in the water where elevated inputs of freshwater due to an accelerated hydrological cycle resulted in a surface-water layer.<ref name=":6" />

===Dactyliocerassandstein=== Occurs only in the south-east of the northern Bavarian Jura region, as appears on places like Bruck in der Oberpfalz, the north-east of the Banz Abbey, Wittelshofen, Regensburg and Bodenwöhr, composed mostly by coarse grained sediments, clusters of clay sandstone and sand-lime stone facies (shale, slightly bituminous in layers, and sandstone, older lias sand, sand marl, marl, oolithic limestone and sand-lime banks). This series is coeval with the Posidonienschiefer, marked with more thin outcrops such as the "crassumbank" (''Coeloceras cf. crassum'', latter found to be ''C. raquinianum'', thus Variabilis in age) at Bodenwöhr, or the ''Dactylioceras'' sandstones at Irlbach (NE Regensburg).<ref name="Bauberger2"/><ref name=Krum32>{{cite journal |last1=Krumbeck |first1=L. |title=Über den Fallaciosus-Horizont im Lias Mittel-ζ von Irlbach bei Regensburg |journal=Centralblatt für Mineralogie, Geologie und Paläontologie, Abteilung B |date=1932 |volume=10 |pages=499–518}}</ref> These levels lack bituminous facies or are interspersed with them in profiles as one moves westward, indicating that they probably belonged to more coastal sectors with better oxygenated waters, with the full transition from shale to sandstone in Regensburg, Bruck and Naab areas considered as caused by a major regression of the sea level, marked at Irlbach by white-yellow levels indicating karst funnels or Cenote-like depostion.<ref name=Krum32/><ref>{{cite journal |last1=Arp |first1=G. |last2=Gropengießer |first2=S. |last3=Schulbert |first3=C. |last4=Jung |first4=D. |last5=Reimer |first5=A. |title=Biostratigraphy and sequence stratigraphy of the Toarcian Ludwigskanal section (Franconian Alb, Southern Germany) |journal=Zitteliana |date=2021 |volume=95 |pages=57–94 |doi=10.3897/zitteliana.95.56222 |doi-access=free |bibcode=2021Zitte..95...57A |url=https://zitteliana.pensoft.net/article/56222/download/pdf/ |access-date=27 January 2024}}</ref>

=== Lehmhagen Member === [[File:Ciechocinek_Formation_Reconstruction.jpg|alt=Reconstructed picture of dinosaurs|thumb|Terrestrial environment of the Toarcian Fennoscandinavia, with flora based on the Sorthat Formation. Animals are based on material found on the Lehmhagen Member, the Grimmen Formation, and tracks of the older Drzewica Formation.]] left|thumb|224x224px|Profile at Grimmen The Lehmhagen Member, designated after Klein Lehmhagen village, was previously referred to the Ciechocinek Formation and then to the Grimmen Formation, yet was in 2025 identified as a new subunit within the Posidonia Shale, notoriously the one with Dinosaur remains and continental biota, otherwise mostly unknown from the formation. It comprises organo-detrital shales interspersed with coastal heterolithes and sandstones ranging from fine- to coarse-grained. The type section is situated in the northern Grimmen clay pit.<ref name="Ansorge2025">{{Cite journal |last1=Ansorge |first1=J. |last2=Franz |first2=M. |last3=Götz |first3=A.E. |date=2025 |title=Stratigraphy and palaeoecology of the Toarcian in NE Germany: organo-detrital and detrital sedimentation in response to the productivity of the planktic ecosystem |journal=PalZ |doi=10.1007/s12542-025-00718-z|bibcode=2025PalZ..tmp...18A |doi-access=free }}</ref> This sequence overlies an erosive boundary with upper Pliensbachian shoreface sands, transitioning upward from coarse coastal sands to finer organo-detrital clays and heterolithes, culminating with a sharp contact to the organic-rich clay. In the North German Basin axis, the member thins to a few decimeters, as observed in the Grambow 5 well. Organic-rich clays and heteroliths with concretions are also noted in Dobbertin. Biostratigraphically significant concretions, named for their index ammonites, mark this member.<ref name="Ansorge2025" />

=== Dörnten Member === The Dörnten Member was also named in 2025, despite being known before, and reflects a transgressive phase of the upper Posidonia Shale, overlaying greenish clays of the Grimmen Formation and fluvio-deltaic sandstones of the Glashütte Formation. Equivalent to the 'Dörntener Schichten' in the Salzgitter and NW Germany regions, it is characterized by fossiliferous, organic-rich strata. The reference section is in the Grambow 5 well, a 16 m thick sequence of dark grey laminated claystone.<ref name="Ansorge2025" /> Ammonite records indicate a range from the upper bifrons to upper thouarsense Zone.{{cn|date=January 2026}} The member thins eastward in the Reinberg 1E well and transitions upward into marine claystones of the Opalinuston Formation or fluvio-deltaic sandstones of the lower Glashütte Formation.<ref name="Ansorge2025" />

== Economical value == thumb|right|Former clay pit in Mistelgau

The Posidonia slate has been mined in the Holzmaden area for centuries to make wall, table, and window panels. Other uses of the shale included making fireplace stones in Gomaringen-Mössingen, which were later replaced by Eifel pumice stone. At Dotternhausen, the ROHRBACH Zement company uses oil shale in the production of binders, mining up to 1,600 t in the 80's. Shale oil, especially after World War II, when where burned on coal ovens, was temporarily obtained from the bituminous slate through smoldering and distillation by oil works near Reutlingen; Frommem or Holzheim near Göppingen, yet this turned out to have low profitability and the fact that they produced a lot of slag and sulfur-containing exhaust gases, production lasted not long.<ref name="MAJORFos">{{cite book |last1=Riegraf |first1=W. |url=http://mmtk.ginras.ru/pdf/Riegraf.et.alii.1984.Die.Posidonienshiefer.Biostratigraphie.Fauna.und.Fazies.J1t.pdf |title=Der Posidonienschiefer: Biostratigraphie, Fauna und Fazies des südwestdeutschen Untertoarciums (Lias e) |last2=Werner |first2=G. |last3=Lörcher |first3=F. |date=1984 |publisher=F. Enke |isbn=3-432-94361-X |location=Berlin |access-date=20 February 2022}}</ref>

Recent studies have shown that the petroleum generation potential of the PS is high across all studied regions due to high TOC and Hydrogen Index values. However, differences exist that can be expressed by SPI values.<ref>{{Cite journal |last1=Lorcher |first1=Fritz |last2=Keller |first2=Thomas |date=1985 |title=Preparation Techniques for Material From The Posidonienschiefer (Lias Epsilon, Upper Liassic) of Germany |journal=Geological Curator |volume=4 |issue=3 |pages=164–168 |doi=10.55468/gc749 |issn=0144-5294}}</ref> The latter are highest for northern Germany, where the PS is richest in TOC and has the highest HI values combined with a thickness of 30 to 40 m at most places.<ref>{{Cite journal |last1=Song |first1=Jinli |last2=Littke |first2=Ralf |last3=Weniger |first3=Philipp |last4=Ostertag-Henning |first4=Christian |last5=Nelskamp |first5=Susanne |date=2015 |title=Shale oil potential and thermal maturity of the Lower Toarcian Posidonia Shale in NW Europe |journal=International Journal of Coal Geology |volume=150-151 |pages=127–153 |doi=10.1016/j.coal.2015.08.011 |bibcode=2015IJCG..150..127S |issn=0166-5162}}</ref> Since the first serious evaluations in the 2000s, different organic samples were extracted to revise the changes and potential presence of the Shale Oil on the main quarries of the southern realm. Based on several core samples with abundant organic material (Dinoflagellate cysts and other microorganism fragments, such as microscopic algae), varying thermal maturity has been observed, especially in samples from the Hils Syncline strata. The maturation of this strata has implied a loss of organic carbon and a decrease in hydrogen index values. Beyond that, the status of the samples has been stable during at least 40 measured years.<ref>{{Cite journal |last1=Fang |first1=Ronghui |last2=Littke |first2=Ralf |last3=Zieger |first3=Laura |last4=Baniasad |first4=Alireza |last5=Li |first5=Meijun |last6=Schwarzbauer |first6=Jan |date=2019 |title=Changes of composition and content of tricyclic terpane, hopane, sterane, and aromatic biomarkers throughout the oil window: A detailed study on maturity parameters of Lower Toarcian Posidonia Shale of the Hils Syncline, NW Germany |journal=Organic Geochemistry |volume=138 |article-number=103928 |doi=10.1016/j.orggeochem.2019.103928 |bibcode=2019OrGeo.13803928F |s2cid=204261799 |issn=0146-6380}}</ref>

thumb|right|Former clay pit in Marloffstein

== Paleontological significance == {{Main|Paleobiota of the Posidonia Shale}} In addition to their ''Posidonia bronni'', the shales contain some spectacularly detailed fossils of other Jurassic sea creatures—ichthyosaurs and plesiosaurs, spiral-shelled ammonites and crinoids, or sea-lilies.<ref name="MAJORFos"/> The best-preserved fossils found in the Early Jurassic can be the ones from the Posidonia Shale. There are also abundant fish fossils (including genera such as ''Pachycormus'', ''Ohmdenia'', ''Strongylosteus'', and chondrichthyes like ''Hybodus'' or ''Palaeospinax''). Most of the fauna is marine, with several terrestrial specimens, including semiaquatic forms such as the sphenodont ''Palaeopleurosaurus'' and fully terrestrial ones like the dinosaur ''Ohmdenosaurus'' and several insects.<ref name="MAJORFos"/>

Flora has been found, especially the genus ''Xenoxylon'', but also macrofloral remains ''Otozamites'', ''Equisetites'' and ''Pagiophyllum'' and palynomorphs, dominated by ''Classopollis''.<ref name="Wilde">{{cite journal |last1=Wilde |first1=V. |title=Die Landpflanzen-Taphozönose aus dem Posidonienschiefer des Unteren Jura (Schwarzer Jura [Epsilon], Unter-Toarcium) in Deutschland und ihre Deutung |journal=Staatliches Museum für Naturkunde |date=2001 |volume=304 |issue=2 |pages=1–12 |url=https://silo.tips/download/stuttgarter-beitrge-zur-naturkunde-5 |access-date=3 March 2022}}</ref><ref name=PalyDor>{{cite journal |last1=Galasso |first1=F. |last2=Feist-Burkhardt |first2=S. |last3=Schneebeli-Hermann |first3=E. |title=The palynology of the Toarcian Oceanic Anoxic Event at Dormettingen, southwest Germany, with emphasis on changes in vegetational dynamics |journal=Review of Palaeobotany and Palynology |date=2022 |volume=304 |issue=1 |article-number=104701 |doi=10.1016/j.revpalbo.2022.104701 |bibcode=2022RPaPa.30404701G |doi-access=free }}</ref>

left|thumb|225x225px|Interior of the Urweltmuseum Hauff

=== Urweltmuseum Hauff === thumb|The exterior of the Urweltmuseum Hauff

The Main Museum with the taxa Found on the Posidonia Shale, the Hauff Museum recovers the best specimens found in the last 150 years; it is situated on Ohmden.<ref name="HauffMus" /> With different expositions, the museum has several spaces for the marine fauna, where it is exposed, including a disposed strata with the layer showing the provenance of every taxon and its fossil. The Museum has been open since 1937-38, and was founded by Bernhard Hauff, using his private collection of fossils as a base, as opposed to Alwin Hauff, who wanted to use the layers for industrial production.<ref name="HauffMus" /> The Museum was reformed between 1967 and 1971. In the year 2000, an external park with Dinosaur models was added.<ref name="HauffMus">{{cite book |last1=Hauff |first1=R. B. |title=Paleontological Collections of Germany, Austria and Switzerland |last2=Joger |first2=U. |date=2018 |publisher=Springer |isbn=978-3-319-77400-8 |edition=1 |series=Natural History Collections |location=Berlin |pages=325–329 |chapter=HOLZMADEN: Prehistoric Museum Hauff—A Fossil Museum Since 4 Generations—(Urweltmuseum Hauff) |doi=10.1007/978-3-319-77401-5_31 |access-date=27 January 2024 |chapter-url=https://link.springer.com/chapter/10.1007/978-3-319-77401-5_31}}</ref> The museum has several halls with different kinds of fauna found on the layers of the formation, where the vertebrate specimens are exposed on the main parts, including on those Icthyosaur remains and several fishes. The Museum has the world's largest colony of sea lilies, measuring approximately 100 square meters. Rolf Bernhard Hauff is the actual director of the museum.<ref>[https://www.urweltmuseum.de/en/urweltmuseum/jurassic-sea-life/ Urweltmuseum Hauff - Jurassic sea life]</ref>

==See also== {{div col|colwidth=29em}} * Blue Lias, England * Charmouth Mudstone Formation, England * Jurensismergel Formation, Germany * Sorthat Formation, Denmark * Hasle Formation, Denmark * Zagaje Formation, Poland * Drzewica Formation, Poland * Ciechocinek Formation, Poland * Borucice Formation, Poland * Rotzo Formation, Italy * Saltrio Formation, Italy * Moltrasio Formation, Italy * Marne di Monte Serrone, Italy * Calcare di Sogno, Italy * Podpeč Limestone, Slovenia * Coimbra Formation, Portugal * El Pedregal Formation, Spain * Fernie Formation, Canada * Whiteaves Formation, British Columbia * Navajo Sandstone, Utah * Ziliujing Formation, China * Yanan Formation, China * Aganane Formation, Morocco * Tafraout Group, Morocco * Azilal Formation, Morocco * Budoš Limestone, Montenegro * Kota Formation, India * Cañadón Asfalto Formation, Argentina * Los Molles Formation, Argentina * Kandreho Formation, Madagascar * Elliot Formation, South Africa * Clarens Formation, South Africa * Evergreen Formation, Australia * Cattamarra Coal Measures, Australia * Hanson Formation, Antarctica * Mawson Formation, Antarctica {{div col end}}

== References == {{Reflist}}

== External links == * [https://web.archive.org/web/20110930132528/http://www.urweltmuseum.de/website/museum/index.htm Images of fossils in the Urwelt-Museum Hauff (Holzmaden)]

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Category:Posidonia Shale Category:Shale formations Category:Open marine deposits Category:Source rock formations Category:Fossiliferous stratigraphic units of Europe Category:Paleontology in Germany Category:Geologic formations of Germany Category:Geologic formations of the Netherlands Category:Geologic formations of Austria Category:Geology of Luxembourg