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Posidonia Shale

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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.

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134-515: 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

268-476: A Gharial), the pterosaur Dorygnathus (as a species of Pterodactylus ) in 1830, the fish Lepidotes , the selachian Hybodus or the crinoid Pentacrinites . The first insight on the flora was done in 1845, with partial leaf fragments. 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

402-553: A basaltic magma to a granitic magma, but the quantities produced are small. For example, granitic rock makes up just 4% of the exposures in the South Sandwich Islands . In continental arc settings, granitic rocks are the most common plutonic rocks, and batholiths composed of these rock types extend the entire length of the arc. There are no indication of magma chambers where basaltic magmas differentiate into granites, or of cumulates produced by mafic crystals settling out of

536-502: A base, as an opposite to Alwin Hauff who wanted to use the layers for industrial production. The Museum was reformed on between the years 1967 and 1971. In the year 2000, an external park with Dinosaur models was added. 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

670-491: A change in carbon-isotope excursion in marine and terrestrial life, and was probably a perturbator of the carbon cycle. 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 were one of the major effects on the palatine de-oxygenation showed on most of the Lower Toarcian Layers around

804-409: A comprehensive picture of a local Jurassic ecosystem . At times, the lagoons almost dried out, exposing sticky carbonate muds that trapped insects and a few small dinosaurs . Over 600 species have been identified, including twenty-nine kinds of pterosaur ranging from the size of a sparrow to 1.2 m (4 ft) in length. The fine-grained texture of the mud silt forming the limestone from

938-520: A diapir it would expend far too much energy in heating wall rocks, thus cooling and solidifying before reaching higher levels within the crust. Fracture propagation is the mechanism preferred by many geologists as it largely eliminates the major problems of moving a huge mass of magma through cold brittle crust. Magma rises instead in small channels along self-propagating dykes which form along new or pre-existing fracture or fault systems and networks of active shear zones. As these narrow conduits open,

1072-430: A few genera were able to survive until oxygen conditions got slightly better. 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). Towards the middle Toarcian show changes on

1206-426: 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 where interpreted as either huge flowers or heads of medusa, and evidencie of the biblical flood. Many people did important geological and paleontological research on

1340-610: A granite that is derived from partial melting of metasedimentary rocks may have more alkali feldspar, whereas a granite derived from partial melting of metaigneous rocks may be richer in plagioclase. It is on this basis that the modern "alphabet" classification schemes are based. The letter-based Chappell & White classification system was proposed initially to divide granites into I-type (igneous source) granite and S-type (sedimentary sources). Both types are produced by partial melting of crustal rocks, either metaigneous rocks or metasedimentary rocks. I-type granites are characterized by

1474-512: A high content of silica and alkali metal oxides that slowly cools and solidifies underground. It is common in the continental crust of Earth, where it is found in igneous intrusions . These range in size from dikes only a few centimeters across to batholiths exposed over hundreds of square kilometers. Granite is typical of a larger family of granitic rocks , or granitoids , that are composed mostly of coarse-grained quartz and feldspars in varying proportions. These rocks are classified by

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1608-565: A high content of sodium and calcium, and by a strontium isotope ratio, Sr/ Sr, of less than 0.708. Sr is produced by radioactive decay of Rb, and since rubidium is concentrated in the crust relative to the mantle, a low ratio suggests origin in the mantle. The elevated sodium and calcium favor crystallization of hornblende rather than biotite. I-type granites are known for their porphyry copper deposits. I-type granites are orogenic (associated with mountain building) and usually metaluminous. S-type granites are sodium-poor and aluminum-rich. As

1742-608: A major regression of the sea level, marked at Irlbach by white-yellow levels indicating karst funnels or Cenote -like depostion. 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 be made into fireplace stones in Gomaringen-Mössingen until was replaced by Eifel pumice stone. At Dotternhausen, the ROHRBACH Zement company uses oil shale in

1876-731: A mostly plain emerged sedimentary structure. 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. The Germanic Epicontinental sea

2010-820: A much higher proportion of clay with the Cecil soil series a prime example of the consequent Ultisol great soil group. Granite is a natural source of radiation , like most natural stones. Potassium-40 is a radioactive isotope of weak emission, and a constituent of alkali feldspar , which in turn is a common component of granitic rocks, more abundant in alkali feldspar granite and syenites . Some granites contain around 10 to 20 parts per million (ppm) of uranium . By contrast, more mafic rocks, such as tonalite, gabbro and diorite , have 1 to 5 ppm uranium, and limestones and sedimentary rocks usually have equally low amounts. Many large granite plutons are sources for palaeochannel -hosted or roll front uranium ore deposits , where

2144-485: A number of locations in southwestern Germany, although most remains are from near the village of Holzmaden and Dotternhausen. 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

2278-536: A peculiar mineralogy and geochemistry, with particularly high silicon and potassium at the expense of calcium and magnesium and a high content of high field strength cations (cations with a small radius and high electrical charge, such as zirconium , niobium , tantalum , and rare earth elements .) They are not orogenic, forming instead over hot spots and continental rifting, and are metaluminous to mildly peralkaline and iron-rich. These granites are produced by partial melting of refractory lithology such as granulites in

2412-521: A preliminary stratigraphy and lithology, which would be the basis for most subsequent works. In the 1900, major paleontological addons included the description of Stenopterygius in 1904 (as Ichthyosaurus ). 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. Hauff described in 1938 "Acidorhynchus" ( Saurorhynchus ),

2546-582: A pronounced dominance of Illite , along with a significant amount of Montmorillonite . 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 . There is a great abundance of Foraminiferans and Coccoliths . Dinoflagellates are

2680-568: A range of hills, formed by the metamorphic aureole or hornfels . Granite often occurs as relatively small, less than 100 km stock masses ( stocks ) and in batholiths that are often associated with orogenic mountain ranges. Small dikes of granitic composition called aplites are often associated with the margins of granitic intrusions . In some locations, very coarse-grained pegmatite masses occur with granite. Granite forms from silica-rich ( felsic ) magmas. Felsic magmas are thought to form by addition of heat or water vapor to rock of

2814-510: 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. The last level of

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2948-415: A result, they contain micas such as biotite and muscovite instead of hornblende. Their strontium isotope ratio is typically greater than 0.708, suggesting a crustal origin. They also commonly contain xenoliths of metamorphosed sedimentary rock, and host tin ores. Their magmas are water-rich, and they readily solidify as the water outgasses from the magma at lower pressure, so they less commonly make it to

3082-466: Is grus , which is often made up of coarse-grained fragments of disintegrated granite. Climatic variations also influence the weathering rate of granites. For about two thousand years, the relief engravings on Cleopatra's Needle obelisk had survived the arid conditions of its origin before its transfer to London. Within two hundred years, the red granite has drastically deteriorated in the damp and polluted air there. Soil development on granite reflects

3216-539: Is microgranite . The extrusive igneous rock equivalent of granite is rhyolite . Granitic rock is widely distributed throughout the continental crust . Much of it was intruded during the Precambrian age; it is the most abundant basement rock that underlies the relatively thin sedimentary veneer of the continents. Outcrops of granite tend to form tors , domes or bornhardts , and rounded massifs . Granites sometimes occur in circular depressions surrounded by

3350-517: Is 3–6·10 Pa·s. The melting temperature of dry granite at ambient pressure is 1215–1260 °C (2219–2300 °F); it is strongly reduced in the presence of water, down to 650 °C at a few hundred megapascals of pressure. Granite has poor primary permeability overall, but strong secondary permeability through cracks and fractures if they are present. A worldwide average of the chemical composition of granite, by weight percent, based on 2485 analyses: The medium-grained equivalent of granite

3484-445: Is a relatively common presence of blue fittings, as well as Wood and Fish remains (Bones, scales). The younger strata with the fresh outcrops develops on a series of several meters thick wall, that splits into fine paper Slates when weathered. 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%. Bituminous Claystones are present in

3618-410: Is an excess of aluminum beyond what can be taken up in feldspars (Al 2 O 3 > CaO + K 2 O + Na 2 O) are described as peraluminous , and they contain aluminum-rich minerals such as muscovite . The average density of granite is between 2.65 and 2.75 g/cm (165 and 172 lb/cu ft), its compressive strength usually lies above 200 MPa (29,000 psi), and its viscosity near STP

3752-618: Is believed to have a mass of around 81 tonnes. It was the tallest temple in south India. Imperial Roman granite was quarried mainly in Egypt, and also in Turkey, and on the islands of Elba and Giglio . Granite became "an integral part of the Roman language of monumental architecture". The quarrying ceased around the third century AD. Beginning in Late Antiquity the granite was reused, which since at least

3886-434: Is called a binary or two-mica granite. Two-mica granites are typically high in potassium and low in plagioclase, and are usually S-type granites or A-type granites, as described below . Another aspect of granite classification is the ratios of metals that potentially form feldspars. Most granites have a composition such that almost all their aluminum and alkali metals (sodium and potassium) are combined as feldspar. This

4020-484: Is considered to be an analogue, as compares well to the sedimentation rate in deep-water settings, of the Black Sea . Most of the outcrops (Holzmaden, Dotternhausen, Ohmden or Dormettingen) represent low-energy depositional environments, far from deltaic sediment sources. The Toarcian epicontinental seas of Europe where driven by several global events and changes present on the surface, like the coeval Karoo-Ferrar eruptions in

4154-433: Is limited by the amount of thermal energy available, which must be replenished by crystallization of higher-melting minerals in the magma. Thus, the magma is melting crustal rock at its roof while simultaneously crystallizing at its base. This results in steady contamination with crustal material as the magma rises. This may not be evident in the major and minor element chemistry, since the minerals most likely to crystallize at

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4288-430: 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 mm) and darker layers (rarely over 2 mm) characteristic. The lighter layers present in the rock get darker while it keeps its fine-plate character. The Shale has a Dark-Gray to brownish tone, alternated with more rarely light gray shades. There

4422-800: Is mostly eroded in the profiles to evolve into marlstones. Several outcrops, mostly in the NW (ex. Harz hills), shows that relict levels of the Posidonienschiefer lasted until the Upper Toarcian, contemporaneous with the Jurensismergel Fm, known as "Dörntener Schiefer". The Sachrang Shales where cited originally on the restudy of the Alpine Upper Black Slate, composed with dark gray, somewhat sandy, disintegrating into thin but large plates of Marl that overlies Pliensbachian breccia. The definition of

4556-404: Is permeated by sheets and channels of light granitic rock (the leucosome ). The leucosome is interpreted as partial melt of a parent rock that has begun to separate from the remaining solid residue (the melanosome). If enough partial melt is produced, it will separate from the source rock, become more highly evolved through fractional crystallization during its ascent toward the surface, and become

4690-680: Is recovered laterally extensive within Germany belonging to the early Toarcian Central European Epicontinental Basin, that evolved gradually from low tophography tidal flat to floodpains 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

4824-454: Is relieved when overlying material is removed by erosion or other processes. Chemical weathering of granite occurs when dilute carbonic acid , and other acids present in rain and soil waters, alter feldspar in a process called hydrolysis . As demonstrated in the following reaction, this causes potassium feldspar to form kaolinite , with potassium ions, bicarbonate, and silica in solution as byproducts. An end product of granite weathering

4958-542: Is shown on layers across Bavaria where major events set the fate of the nearshore environments. One example is the case of the Monotis – Dactylioceras beds, that had an extent of +500 km, that has been linked with a possible Tsunami . There is not major indicative of synsedimentary faulting in South Germany, but is present on the western Tethyan Shelf , with breccias created from earthquakes, present on Toarcian levels of

5092-411: Is some concern that some granite sold as countertops or building material may be hazardous to health. Dan Steck of St. Johns University has stated that approximately 5% of all granite is of concern, with the caveat that only a tiny percentage of the tens of thousands of granite slab types have been tested. Resources from national geological survey organizations are accessible online to assist in assessing

5226-479: Is that magma will rise through the crust as a single mass through buoyancy . As it rises, it heats the wall rocks , causing them to behave as a power-law fluid and thus flow around the intrusion allowing it to pass without major heat loss. This is entirely feasible in the warm, ductile lower crust where rocks are easily deformed, but runs into problems in the upper crust which is far colder and more brittle. Rocks there do not deform so easily: for magma to rise as

5360-410: Is the case when K 2 O + Na 2 O + CaO > Al 2 O 3 > K 2 O + Na 2 O. Such granites are described as normal or metaluminous . Granites in which there is not enough aluminum to combine with all the alkali oxides as feldspar (Al 2 O 3 < K 2 O + Na 2 O) are described as peralkaline , and they contain unusual sodium amphiboles such as riebeckite . Granites in which there

5494-455: Is typically orthoclase or microcline and is often perthitic . The plagioclase is typically sodium-rich oligoclase . Phenocrysts are usually alkali feldspar. Granitic rocks are classified according to the QAPF diagram for coarse grained plutonic rocks and are named according to the percentage of quartz , alkali feldspar ( orthoclase , sanidine , or microcline ) and plagioclase feldspar on

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5628-428: Is uncommon, is classified simply as quartz-rich granitoid or, if composed almost entirely of quartz, as quartzolite . True granites are further classified by the percentage of their total feldspar that is alkali feldspar. Granites whose feldspar is 65% to 90% alkali feldspar are syenogranites , while the feldspar in monzogranite is 35% to 65% alkali feldspar. A granite containing both muscovite and biotite micas

5762-468: 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. The Aschgrauen Mergel (ash-gray marl) mark the start of

5896-579: The Bajocian layers. The slopes of the area are partially covered by till , soliflucted rubble and loess from the Würm glaciation . 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 as “bitumen-free” or “bitumen-poor”. The lowermost sequence is known as Seegrasschiefer (seagrass slate), appearing just above

6030-493: The Benzene - Methanol fraction. 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 , what suggests that terrestrial inputs of organic matter to be of less importance, although, the main part of OM contained in the basal mudstone, including charred material,

6164-564: 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%). According to sedimentologic and palynologic features, a tidally influenced transgressive development within

6298-684: The Keilberg Rift , the main fault in the Regensburg Basin. 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. During the late Pliensbachian, the zone became a relatively narrow, flat deposit area which flooded during

6432-805: The Netherlands to the Tirol Area. The CEB stablished a relatively shallow transcontinental seaway between the Tethyan and Boreal Arctic Sea biota, thus mixing cold and hot waters. In the Mesozoic was marked by the breakup of Pangea during the Late Triassic , what led to the appearance of the early Atlantic connecting with the Boreal waters of the Panthalassa Ocean, and several marine to continental subasins locally. The CEB

6566-710: The Pliensbachian - Toarcian locally is observed a significant decrease in the Crinoid skeleton elements, also that of the Ophiurida ; the Echinoids take their place, where really blossomed at that time, while Pedicellaria are observed very often. 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). Benzenemethanol resins are especially strong for

6700-509: The Solnhofen area (which is composed mainly of the towns of Solnhofen and Eichstätt ) is ideal for making lithographic plates, and extensive quarrying in the 19th century revealed many fossil finds, as commemorated in the name Archaeopteryx lithographica , all the specimens of which come from these deposits. The closest modern analogue to the Solnhofen conditions is said to be Orca Basin in

6834-589: The Valais , Briançonnais  [ fr ] and Piemonte - Liguria domains ( Sinemurian - Callovian ), and the Toarcian break-up of the Ligurian-Penninic oceanic realm. There is measurements of reduction of the local salinity on the water where elevated inputs of freshwater due to an accelerated hydrological cycle resulted in a surface-water layer. Occurs only in the south-east of the northern Bavarian Jura region, as appears on places like Bruck in der Oberpfalz ,

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6968-596: 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). 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

7102-567: The A-Q-P half of the diagram. True granite (according to modern petrologic convention) contains between 20% and 60% quartz by volume, with 35% to 90% of the total feldspar consisting of alkali feldspar . Granitic rocks poorer in quartz are classified as syenites or monzonites , while granitic rocks dominated by plagioclase are classified as granodiorites or tonalites . Granitic rocks with over 90% alkali feldspar are classified as alkali feldspar granites . Granitic rock with more than 60% quartz, which

7236-776: The Austrian Adnet Formation . It would start as an initial wave propagation affecting the Altdorf High aiming for the south, where it would have hitten the shoreline of the Bohemian Island. 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 km at

7370-567: The Edge facies of the Sachrang Shale (="Unken Shales"), with green Clay march engagements. There is not clear separation between "Manganese Shale" and "Bituminous shale" in the main localities of the formation, because the Bituminous content fluctuates with the manganese contents, that is always high. The Unken Shales on the Bächental locality is layered on a major Silicate component of the 60% with

7504-598: The European Union safety standards (section 4.1.1.1 of the National Health and Engineering study) and radon emission levels well below the average outdoor radon concentrations in the US. Granite and related marble industries are considered one of the oldest industries in the world, existing as far back as Ancient Egypt . Major modern exporters of granite include China, India, Italy, Brazil, Canada, Germany, Sweden, Spain and

7638-686: The Germanic unit, in a same way Altmühltal Formation is the official name of the Solnhofen Limestone. 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 . The type profile is still located on Dotternhausen . The formation comprises finely laminated layers of oil shales formed of fine-grained sediments intercalated with bituminous limestones and crops out in

7772-563: The Lower Toarcian is inferred with increased continental matter being moved to marine areas causing anoxic conditions, with the Posidonia Shale being 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. On

7906-631: The Mohs hardness scale) , and tough. These properties have made granite a widespread construction stone throughout human history. The word "granite" comes from the Latin granum , a grain, in reference to the coarse-grained structure of such a completely crystalline rock. Granitic rocks mainly consist of feldspar , quartz , mica , and amphibole minerals , which form an interlocking, somewhat equigranular matrix of feldspar and quartz with scattered darker biotite mica and amphibole (often hornblende ) peppering

8040-501: 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. The Toarcian and the Pliensbachian are considered as strongly constrained in terms of chronology, where

8174-413: 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 cm), unnamed bituminous, seegrasschiefer clay marl, followed then by a darker layers with

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8308-456: The SW and NW Germanic basins, as part of a shallow epicontinental sea, surrounded and influenced by various highs and emerged lands that provided most of the terrestrial matter found along the Formation. The main outcrops of the formation are disposed along the modern southern Germany, recovering the locations of Holzmaden , Ohmden , as well at Niedersachsen , and others appearing along the east, such as

8442-584: The Sachrang Shales has been convoluted along its history of study of the location, where there are works of the North Alpine Mesozoic that prefer before calling these deposits Sachranger Shale to give it a brief different diagnosis. 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

8576-605: The Shale deposition on Germany, also sharing a epicontinental sea, bordered by carbonate facies, specially towards the south. 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 . In this area, the main emerged units present was the Rhenish High at

8710-662: The Solnhofen Plattenkalk include the early feathered theropod dinosaur Archaeopteryx preserved in such detail that they are among the most famous and most beautiful fossils in the world. The Solnhofen beds lie in the German state of Bavaria (Bayern) , halfway between Nuremberg (Nürnberg) and Munich (München) and were originally quarried as a source of lithographic limestone . The Jura Museum situated in Eichstätt , Germany has an extensive exhibit of Jurassic fossils from

8844-668: The Southern Hemisphere, what 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 . 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

8978-580: 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). The first geological studies were carried out, motivated by the extraction of shales in 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

9112-448: The United States. The Red Pyramid of Egypt ( c.  2590 BC ), named for the light crimson hue of its exposed limestone surfaces, is the third largest of Egyptian pyramids . Pyramid of Menkaure , likely dating 2510 BC, was constructed of limestone and granite blocks. The Great Pyramid of Giza (c. 2580 BC ) contains a huge granite sarcophagus fashioned of "Red Aswan Granite". The mostly ruined Black Pyramid dating from

9246-678: 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. 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. The Obere and Wilder Stein (upper elegans) medium to brown-gray always remain formed as

9380-419: The base of the chamber are the same ones that would crystallize anyway, but crustal assimilation is detectable in isotope ratios. Heat loss to the country rock means that ascent by assimilation is limited to distance similar to the height of the magma chamber. Physical weathering occurs on a large scale in the form of exfoliation joints , which are the result of granite's expanding and fracturing as pressure

9514-418: The big difference in rheology between mafic and felsic magmas makes this process problematic in nature. Granitization is an old, and largely discounted, hypothesis that granite is formed in place through extreme metasomatism . The idea behind granitization was that fluids would supposedly bring in elements such as potassium, and remove others, such as calcium, to transform a metamorphic rock into granite. This

9648-561: 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) different thermal maturity has been found, especially on the samples from the Hils Syncline strata. The maturation of this strata has implied losing organic carbon and loss of hydrogen index values. Beyond that,

9782-516: 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. The Black shale deposition was found to be related with changues in the oxygen levels. Thanks to the renewed information, a new cycle of publications reviewing

9916-614: The deposition has been estimated to have lasted 3.2 Myr in the South Germany Basin with the uppermost sequences estimated to be Bifrons in age. 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). The Posidonia Shale has been

10050-404: The division between S-type (produced by underplating) and I-type (produced by injection and differentiation) granites, discussed below. The composition and origin of any magma that differentiates into granite leave certain petrological evidence as to what the granite's parental rock was. The final texture and composition of a granite are generally distinctive as to its parental rock. For instance,

10184-467: The early 16th century became known as spolia . Through the process of case-hardening , granite becomes harder with age. The technology required to make tempered metal chisels was largely forgotten during the Middle Ages. As a result, Medieval stoneworkers were forced to use saws or emery to shorten ancient columns or hack them into discs. Giorgio Vasari noted in the 16th century that granite in quarries

10318-525: 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. 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

10452-401: The east, which temporarily lowered the salinity of the seawater in the whole basin or in parts. The margins of the SWGB as well as the hinterland relief had very gentle topography, and therefore fine-grained siliciclastic sediments where easily transported and deposited in the nearshore area of the basin, as well long transported driftwood, and the lack of insects or terrestrial vertebrates. In

10586-428: 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. The uppermost layers are marked by regressive sea levels, as it

10720-480: The fauna is marine, with several terrestrial specimens, and some of them being semiaquatic, such as the sphenodont Palaeopleurosaurus or fully terrestrial like the dinosaur Ohmdenosaurus and several insects. Flora has been found, especially the genus Xenoxylon , but also macrofloral remains Otozamites , Equisetites and Pagiophyllum and palynomorphs, dominated by Classopollis . The Main Museum with

10854-579: The first magma to enter solidifies and provides a form of insulation for later magma. These mechanisms can operate in tandem. For example, diapirs may continue to rise through the brittle upper crust through stoping , where the granite cracks the roof rocks, removing blocks of the overlying crust which then sink to the bottom of the diapir while the magma rises to take their place. This can occur as piecemeal stopping (stoping of small blocks of chamber roof), as cauldron subsidence (collapse of large blocks of chamber roof), or as roof foundering (complete collapse of

10988-524: 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

11122-464: 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. The abundance of organic matter and the composition of the shales, chemically or lithologically, went under diverse renoved works. With the addition of multiple new references, the expansion of information thanks to the revision of profiles, boreholes and other outcrops, new works on

11256-839: The formation. The Posidonia Shale was originally referred to as the Schwarzjura lias was first recovered from the Franconian Jura , that borders to the northeast on the Obermainisches Hügelland and the Oberpfälzisch-Obermainisches Hügelland, tectonically part of the Faulkschollenland. The Franconian Jura rocks recovered are west of the Saxothuringian basement bordering the Franconian Line . It

11390-684: The grotto is a highly regarded piece of Buddhist art , and along with the temple complex to which it belongs, Seokguram was added to the UNESCO World Heritage List in 1995. Rajaraja Chola I of the Chola Dynasty in South India built the world's first temple entirely of granite in the 11th century AD in Tanjore , India . The Brihadeeswarar Temple dedicated to Lord Shiva was built in 1010. The massive Gopuram (ornate, upper section of shrine)

11524-455: 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 exceptional preserved fossils indicate very weak water movement. The next, Untere Stein, is the most important level of the formation, specially in southwest Germany, southern France and Alsace - Lorraine . It appears across

11658-560: The latest surviving of the Saurichthyiformes . In 1953, an impressive Insect fauna was revised in the Northern outcrops. On 1978, Wild described the First and only know Dinosaur Fossil from the formation, what he named Ohmdenosaurus , a small sized Sauropod. Latter works revisited the excepcional preservation of the biota, specially the presence od soft parts. The lithology and sedimentology of

11792-570: The lighter color minerals. Occasionally some individual crystals ( phenocrysts ) are larger than the groundmass , in which case the texture is known as porphyritic . A granitic rock with a porphyritic texture is known as a granite porphyry . Granitoid is a general, descriptive field term for lighter-colored, coarse-grained igneous rocks. Petrographic examination is required for identification of specific types of granitoids. Granites can be predominantly white, pink, or gray in color, depending on their mineralogy . The alkali feldspar in granites

11926-551: The limestone. Such formations are not plant fossil remains, but iron and manganese oxides ( psilomelane , (Ba,H 2 O) 2 Mn 5 O 10 ) that crystallized out of solutions on bedding planes of the Solnhofen limestone. Dendrites have a chemical-mineralogical origin and are formed by a diffusion process. Granite Granite ( / ˈ ɡ r æ n ɪ t / GRAN -it ) is a coarse-grained ( phaneritic ) intrusive igneous rock composed mostly of quartz , alkali feldspar , and plagioclase . It forms from magma with

12060-465: The limit, being actively burrowed horizons, approximately 15-20 cm thick with clay marl stone appear in the darker, brownish to gray, bituminous clay marl/marl slate. This initial horizons have abundant foraminifera and ostracods as the medium to light gray color without a brown tint. 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

12194-474: The lower crust , rather than by decompression of mantle rock, as is the case with basaltic magmas. It has also been suggested that some granites found at convergent boundaries between tectonic plates , where oceanic crust subducts below continental crust, were formed from sediments subducted with the oceanic plate. The melted sediments would have produced magma intermediate in its silica content, which became further enriched in silica as it rose through

12328-697: The lower continental crust at high thermal gradients. This leads to significant extraction of hydrous felsic melts from granulite-facies resitites. A-type granites occur in the Koettlitz Glacier Alkaline Province in the Royal Society Range, Antarctica. The rhyolites of the Yellowstone Caldera are examples of volcanic equivalents of A-type granite. M-type granite was later proposed to cover those granites that were clearly sourced from crystallized mafic magmas, generally sourced from

12462-435: The magma is inevitable once enough magma has accumulated. However, the question of precisely how such large quantities of magma are able to shove aside country rock to make room for themselves (the room problem ) is still a matter of research. Two main mechanisms are thought to be important: Of these two mechanisms, Stokes diapirism has been favoured for many years in the absence of a reasonable alternative. The basic idea

12596-426: The magma. Other processes must produce these great volumes of felsic magma. One such process is injection of basaltic magma into the lower crust, followed by differentiation, which leaves any cumulates in the mantle. Another is heating of the lower crust by underplating basaltic magma, which produces felsic magma directly from crustal rock. The two processes produce different kinds of granites, which may be reflected in

12730-408: The magmatic parent of granitic rock. The residue of the source rock becomes a granulite . The partial melting of solid rocks requires high temperatures and the addition of water or other volatiles which lower the solidus temperature (temperature at which partial melting commences) of these rocks. It was long debated whether crustal thickening in orogens (mountain belts along convergent boundaries )

12864-484: The main Jurassic Strata, without classifying the layers on a concrete subperiod. 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. The main work that described the facies formally was Quenstedt´s 1843 one, classifying the levels based on the amount of bitumen, providing

12998-603: The major organic component and the most abundant microfossils. Manganese is present, such as in the Toarcian deposits of Hungary. Those are completed by the marl levels, composed by 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. Isorenieratene derivatives are highly abundant on this level, related to several processes such as sedimentary iron, influenced by anoxic conditions. Rhodochrosite and manganese rich calcite are present in

13132-551: The manganese levels, while the Black Shale levels are rich in Pirite . 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. On

13266-405: The mantle. Although the fractional crystallisation of basaltic melts can yield small amounts of granites, which are sometimes found in island arcs, such granites must occur together with large amounts of basaltic rocks. H-type granites were suggested for hybrid granites, which were hypothesized to form by mixing between mafic and felsic from different sources, such as M-type and S-type. However,

13400-468: The microfacies took place between 1980-1990. 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

13534-452: 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 are coeval with the Posidonienschiefer, marked with more thin outcrops such as

13668-530: The northern Gulf of Mexico , though that area is much deeper than the Solnhofen lagoons. In respect of the locality being a 'first-class paleontological site displaying high-quality reference material for scientists worldwide, including all known specimens of Archaeopteryx ', the International Union of Geological Sciences (IUGS) included the 'Jurassic Solnhofen-Eichstätt Archaeopteryx Serial Site' in its assemblage of 100 'geological heritage sites' around

13802-478: 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. The study of the different layers and strata of

13936-441: The overlying crust. Early fractional crystallisation serves to reduce a melt in magnesium and chromium, and enrich the melt in iron, sodium, potassium, aluminum, and silicon. Further fractionation reduces the content of iron, calcium, and titanium. This is reflected in the high content of alkali feldspar and quartz in granite. The presence of granitic rock in island arcs shows that fractional crystallization alone can convert

14070-534: The petroleum generation potential of the PS is high in all studied regions due to the high TOC and Hydrogen Index. However, differences exist which can be expressed by SPI values. 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. Since the first serious evaluations in the 2000s, different organic samples were extracted to revise

14204-476: The production of binders, mining in the 80´s up to 1,600 t. Shale oil, specially after World War II , when where burned on coal ovens was temporally 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 they produced a lot of slag and sulfur-containing exhaust gases, production lasted not long. Recent studies have shown that

14338-517: The quarries of Solnhofen and surroundings, including marine reptiles, pterosaurs , and one specimen of the early bird Archaeopteryx . During the Late Jurassic , this area was an archipelago at the edge of the Tethys Sea . This included placid lagoons that had limited access to the open sea and where salinity rose high enough that the resulting brine could not support life. Since the lowest water

14472-702: The reign of Amenemhat III once had a polished granite pyramidion or capstone, which is now on display in the main hall of the Egyptian Museum in Cairo (see Dahshur ). Other uses in Ancient Egypt include columns , door lintels , sills , jambs , and wall and floor veneer. How the Egyptians worked the solid granite is still a matter of debate. Tool marks described by the Egyptologist Anna Serotta indicate

14606-627: The related to the Banz Abbey strata or Regensburg . 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. Connected to the SW German basin where the Paris Basin , that recovered central France , with correlated sedimentation to

14740-420: The relative percentages of quartz, alkali feldspar, and plagioclase (the QAPF classification ), with true granite representing granitic rocks rich in quartz and alkali feldspar. Most granitic rocks also contain mica or amphibole minerals, though a few (known as leucogranites ) contain almost no dark minerals. Granite is nearly always massive (lacking any internal structures), hard (falling between 6 and 7 on

14874-551: The risk factors in granite country and design rules relating, in particular, to preventing accumulation of radon gas in enclosed basements and dwellings. A study of granite countertops was done (initiated and paid for by the Marble Institute of America) in November 2008 by National Health and Engineering Inc. of USA. In this test, all of the 39 full-size granite slabs that were measured for the study showed radiation levels well below

15008-418: The rock's high quartz content and dearth of available bases, with the base-poor status predisposing the soil to acidification and podzolization in cool humid climates as the weather-resistant quartz yields much sand. Feldspars also weather slowly in cool climes, allowing sand to dominate the fine-earth fraction. In warm humid regions, the weathering of feldspar as described above is accelerated so as to allow

15142-414: The rocks often bear a close resemblance. Under these conditions, granitic melts can be produced in place through the partial melting of metamorphic rocks by extracting melt-mobile elements such as potassium and silicon into the melts but leaving others such as calcium and iron in granulite residues. This may be the origin of migmatites . A migmatite consists of dark, refractory rock (the melanosome ) that

15276-489: The roof of a shallow magma chamber accompanied by a caldera eruption.) There is evidence for cauldron subsidence at the Mt. Ascutney intrusion in eastern Vermont. Evidence for piecemeal stoping is found in intrusions that are rimmed with igneous breccia containing fragments of country rock. Assimilation is another mechanism of ascent, where the granite melts its way up into the crust and removes overlying material in this way. This

15410-469: The same lithology . The next are the called "Koblenzer-Hainzen" clay successions of upper the semicelatum subzone, initially poorly layered and more or less bituminous with abundance of Steirmannia radiata and Dactylioceras semieelatum . This section is marked by pyritized lagerstatten fossils, limited to certain areas (Dotternhausen, Holzmaden), and with now well-layered black-brown in color. The Unteren Schiefern layers (Exaratum) appear next marked by

15544-497: The same age was complicated due to the posterior Alpine deformation. Correlated Unken and Diessbach basins developed mostly during the Toarcian, with deposition of abundant material from the near Emerged Landmasses. On the Unken Syncline, the breccias associated with the normal faults were deposited until Oxfordian age. The black shales are the main part of the strata present, with a major composition of bacterial origin. The shale

15678-405: The shale deposits. In the 2000´s the Posidonienschiefer has seen a series of works, focused on enriching the information previously worked on in depth, revising and updating the deposition models. 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. The Posidonia Shale was located in

15812-538: 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. In Microfacies, after

15946-631: The status of the samples has been stable during at least 40 measured years. 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. The best-preserved fossils found on 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

16080-435: The surface than magmas of I-type granites, which are thus more common as volcanic rock (rhyolite). They are also orogenic but range from metaluminous to strongly peraluminous. Although both I- and S-type granites are orogenic, I-type granites are more common close to the convergent boundary than S-type. This is attributed to thicker crust further from the boundary, which results in more crustal melting. A-type granites show

16214-517: The taxa Found on the Posidonia Shale, the Hauff Museum recovers the best specimens found in the last 150 years, and it is situated on Ohmden . 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

16348-502: The uranium washes into the sediments from the granite uplands and associated, often highly radioactive pegmatites. Cellars and basements built into soils over granite can become a trap for radon gas, which is formed by the decay of uranium. Radon gas poses significant health concerns and is the number two cause of lung cancer in the US behind smoking. Thorium occurs in all granites. Conway granite has been noted for its relatively high thorium concentration of 56±6 ppm. There

16482-599: The use of flint tools on finer work with harder stones, e.g. when producing the hieroglyphic inscriptions. Patrick Hunt has postulated that the Egyptians used emery , which has greater hardness. The Seokguram Grotto in Korea is a Buddhist shrine and part of the Bulguksa temple complex. Completed in 774 AD, it is an artificial grotto constructed entirely of granite. The main Buddha of

16616-572: 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 ). The Environments of this highs are assumed to have been trought phases os aridity and humidy markedby the Toarcian Oceanic Anoxic Event on the basis of Palynology. In the east the SW German sub-basin

16750-565: The west, being a small land of the size of Sicily , and on the east, the N Bohemian Massif . The Bohemian massif with the Southern Vindelician High represent the major emerged units present on the Central European basin on the Toarcian. 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

16884-405: The word, with the connection with the Viking Corridor as one of the main effects, due to the arctic waters freshening and breaking the oceanic circulation. 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

17018-580: The world in a listing published in October 2022. The organisation defines an IUGS Geological Heritage Site as 'a key place with geological elements and/or processes of international scientific relevance, used as a reference, and/or with a substantial contribution to the development of geological sciences through history.' Significant members of the Solnhofen paleofauna include Archaeopteryx , pterosaurs, and marine invertebrates. Dendrites , branched dark brown to black fractal tree-structure, are quite common in

17152-561: The world's largest colony of sea lilies, measuring an approximate size of 100 square metres. Rolf Bernhard Hauff is the actual director of the museum. Altm%C3%BChltal Formation The Solnhofen Limestone or Solnhofen Plattenkalk , formally known as the Altmühltal Formation , is a Jurassic Konservat-Lagerstätte that preserves a rare assemblage of fossilized organisms, including highly detailed imprints of soft bodied organisms such as sea jellies. The most familiar fossils of

17286-721: 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 . The Bohemian Massif was located in a relatively warm, precipitation-rich climate with Bavarian shallow areas receiving freshwater inflows from

17420-450: 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, what indicated a clear contribution of volcanic-derived detritus during deposition. In the Austrian area, the volcanic materials where probably also sourced by the rift history of

17554-508: Was devoid of oxygen , many ordinary scavengers were absent. Any organism that fell, drifted, or was washed into the lagoons from the ocean or the land became buried in soft carbonate mud. Thus, many delicate creatures avoided consumption by scavengers or being torn apart by currents. The wings of dragonflies , the imprints of stray feathers , and terrestrial plants that washed into the lagoons were all preserved. The fossils are not numerous, but some of them are spectacular, and their range gives

17688-513: Was part of the Laurasian continental-marine shelf that, resting over the Keuper, slowly openened 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, what contributed and controlled the evolution of the paleocurrents. Towards the W is determined by the north–south Kilberg Fault of

17822-405: Was sufficient to produce granite melts by radiogenic heating , but recent work suggests that this is not a viable mechanism. In-situ granitization requires heating by the asthenospheric mantle or by underplating with mantle-derived magmas. Granite magmas have a density of 2.4 Mg/m , much less than the 2.8 Mg/m of high-grade metamorphic rock. This gives them tremendous buoyancy, so that ascent of

17956-564: Was supposed to occur across a migrating front. However, experimental work had established by the 1960s that granites were of igneous origin. The mineralogical and chemical features of granite can be explained only by crystal-liquid phase relations, showing that there must have been at least enough melting to mobilize the magma. However, at sufficiently deep crustal levels, the distinction between metamorphism and crustal melting itself becomes vague. Conditions for crystallization of liquid magma are close enough to those of high-grade metamorphism that

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