Geology of the Franconian Alb
The geology of the Franconian Alb is determined by a layer level of the southern German layer level country . It consists of flat sedimentary terrestrial and marine deposits in the form of thick layers of clay , calcium carbonate and marl , which have not been overlaid by metamorphosis . They are part of the lithostratigraphic rock unit of the southern German Jura . According to their color, this rock unit is subdivided from bottom to top into the Black Jura (Lias), the Brown Jura (Dogger) and the White Jura (Malm).
The development period extends from the Upper Keuper (beginning about 206 million years ago) of the Germanic Triassic to the end of the Upper Cretaceous (about 66 million years ago).
Location and extent
To the northeast, the Franconian Alb borders on the Upper Main Hill Country and the Upper Palatinate Hill Country , summarized as the Upper Palatinate-Upper Main Hill Country . Tectonically, they form the southern German Bruchschollenland. This borders on the Franconian line , which delimits the Tafeldeckgebirge of the southern German layer level country to the east and northeast from the Variscan basement . To the southwest, the Alb merges into the Franconian Keuper-Lias-Land with its components foreland of the Southern Franconian Alb, foreland of the Middle Franconian Alb, foreland of the Northern Franconian Alb and Middle Franconian Basin .
Lower limits the Frankish Alb to the Ries , which has a front mya resulting meteor crater represents. The Swabian Alb joins there. The northern foothills of the Franconian Alb extend to the Staffelberg and the neighboring Kordigast near the Main .
tectonics
Lithostratigraphically , the rocks of the Franconian Alb are based on the predominantly sand and claystones of the Upper Keuper in the Keuperbergland .
The southern German layer level country or the southern German large plaice, within which the Franconian Alb lies, is tectonically characterized by several large bulges (see anticline ) and hollows (see syncline ) with sometimes long fracture zones and faults . Their multi-phase evolution has a connection with the Variscan orogeny and probably began in the Stefanium (from 305 mya) of the Carboniferous .
The Franconian Jura is located in the area of subsidence of flachherzynisch trending Frankenalbfurche or -mulde. Herzynisch refers to the west-north-west / east-south-east course of the Harz north rim fault or the entire Harz floe. The Frankenalbfurche was probably created in the beginning already at the end of the Middle Keuper (from approx. 209 mya) in the Triassic . The furrow runs through the grave field basin in the north and runs further south-east with a length of about 200 kilometers and a width of 5 to 8 kilometers the entire Franconian Alb to the area of Regensburg , where it turns into the large subsidence zone of the extra-alpine molasse and up to continues beyond the Inn .
The Frankenalbfurche is structured by slight transverse bulges that separate several hollows and ditches . The deepest subsidence areas are located south of Regensburg and in the middle of the Alb near Hollfeld . From a tectonical point of view , the Hollfelder Mulde is sunk by 300 m towards Erlangen and by 600 m towards Bayreuth .
Tectonic forces generated bending of rock layers on both sides of the Franconian valley (see flexure ) and faults . Both are closely related genetically and are bound to the same clod edges of the consolidated subsoil. They mostly have the Hercynian course of the entire furrow, but different stages of development of the same tectonic process. In the initial flexures, various longitudinal, transverse and diagonal fractures, shear surfaces and, finally, faults parallel to the fracture developed. These processes date before the Cenomanian (from about 100 mya) of the Cretaceous .
Chronostratigraphic development
The sedimentary rocks of the Franconian Alb were deposited to the west in front of the basement mountains of the Saxothuringian, a tectonic unit of the Variscan Mountains . These include the Franconian Forest , the Vogtland , the Fichtel Mountains and the Upper Palatinate-Bavarian Forest . The northern area of this basement is separated from the upstream sedimentary cover by the very well exposed Franconian Line . It represents a geological fault that was created as part of the Variscan Orogeny or even earlier and later reactivated.
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The outcrops of the South German Jura show a complete sequence from the sandstones of the Upper Keuper to the different rocks of the Black Jura and Brown Jura to the limestone and dolomite layers of the White Jura. Other deposits form the weathering - loams on the plateaus (Albüberdeckung), flight sands from the last glacial period , floating earth - and talus formation , filling the valleys and young Quellkalke .
The Hetzleser Berg, also called Hetzlas, shows as a witness mountain with its outcrops all three lithostratigraphic groups of the southern German Jura.
The sequence of layers in the Franconian Alb initially sedimented in an area near the coast, which was subject to frequent changes between continental and marine conditions up to a shallow shelf sea. In the main phase of the deposition, the area was below sea level at different depths of a tributary of the Tethys Ocean .
The German geologist Friedrich August Quenstedt divided the Jura deposits into the main strata levels Lias, Dogger and Malm and these into six further sub-levels, the Quenstedt division . They are designated with letters of the Greek alphabet (from bottom to top: Alpha, Beta, Gamma, Delta, Epsilon, Zeta). This forms the basis for dating the chronostratigraphic development of the southern German Jura . The terms Lias, Dogger and Malm are still used synonymously with the terms Schwarzer, Brauner and Weißer Jura.
Development in the Triassic
The lowest deposits of the Franconian Alb originated in the Upper Keuper of the Germanic Triassic near the coast in swampy lake plateaus , river deltas , silting areas and lagoons of the Germanic Basin . The Germanic Basin was an intra-continental depression which, after the Zechstein Sea dried up about 200 million years ago, expanded to the south as a result of further crust subsidence. Conditions were predominantly continental, but were accompanied by marine advances. These transgressions came from an extension of a north-facing sea. The basin was surrounded by high mountains , the weathered debris deposited in different places and depressions at irregular times and intensities. Relocations of the sediments from the edge towards the center and vice versa also took place. Temporary lakes had also formed in the basin, which often looked more like a drying salt lake than a freshwater reservoir filled with life.
The characteristics of the sedimentation in the Germanic Basin is determined by a sequence of facies belts . These belts were not stationary, but shifted with changes in environmental conditions, such as the climate, the intensity of weathering and erosion, the acceleration or deceleration of the subsidence of the basin center, and the transgression or regression of the sea. Depending on this, different facies belts emerged, such as alluvial fans or alluvial cones of rivers, salt plains , also known as the playa plains, and freshwater or saltwater playa lakes.
Towards the end of the Upper Keuper ( Rhaetium ), the sea expanded in a south-easterly direction. The former largely continental deposit area was now gradually flooded by the sea. Rivers transported sediments from the mainland of the Bohemian Massif and the Vindelizi Sill connected to it to the coastal area.
The deposits in the Rhätium formed the western part of the Franconian Alb, the foothills of the Alb, characterized by soft hill forms. The oldest geological layers are located here: sandstones and clays of the Upper Keuper with an age of around 200 million years. This is followed by clays of the Trossingen formation (Feuerletten) and the sandstones of the so-called Rhätolia, a transition layer from the Upper Keuper to the Lias, Alpha 2, a lower layer in the Black Jura . But Keuper rocks were also deposited east of the Franconian Alb up to the Franconian Line.
The sequence of layers of the Germanic Triassic forms the lower floor on which the rock sequences of the Franconian Alb lie.
Development in the Jura
The turning point initiated in the Rhaetium led to geology and geography during the Jurassic period, which began 199.3 million years ago. With the opening of the Central Atlantic about 150 million years ago as a result of a rift system (English rift) between Gondwana and Laurasia , smaller oceanic basins opened up in the area of the Alpine sedimentation area. In the Upper Jurassic , the Vindelice Sill disappeared into the sea and the bottom of the shallow sea in southern Germany began to drop off to the south towards the opening Tethys into deep sea areas. Associated with this were different sedimentation conditions, which are reflected in the lithostratigraphic groups of the southern German Jura . The shifts in the color of the sedimentary rocks correspond to the increasing expansion and opening of the ocean, until the southern German area in the White Jura was in unhindered connection with the western foothills of the Tethys Ocean. With the constant subsidence of the crust, mighty rock sequences were deposited on the sea floor. The Jura sediments form the largest part of the deposition sequences occurring in the Franconian Alb. They are structured as follows:
- The marine deposits of the Black Jurassic (Lias) formed 199 to 175 million years ago in an area of the Jurassic Sea, an extension of the Tethys Ocean, which was still very close to the coast. The Black Jura consists mainly of dark sandstones, clays, marls and limestones, some of which can also be bituminous , as in the Posidonia slate formation . The clays of the Posidonia Schist Formation often contain a relatively large amount of petroleum , which was also extracted during the Second World War . The layers are up to about 80 meters thick.
The basal layer of the Black Jura is formed by the Franconian Bamberg Formation and Bayreuth Formation , which are interlocked with the Psilonotenton Formation of the rest of the southern German Jura. These sediments mainly consist of clay stones with some embedded siltstone banks, silty-sandy limestone banks or limestone banks with chamositoids . The uppermost deposit level is the Jurensis marl formation . It is characterized by gray, brownish, sometimes yellowish marl and marl limestones, in which bulbous limestone and condensation horizons ("ammonite soaps", dense accumulations of ammonites) can intervene. The sediment layers in the Black Jura were often deposited under reducing or oxygen-free and hydrogen sulfide-containing conditions, which led to the rocks turning black.
The main slope of the Main on the Trimensel or Trimeusel is probably the most impressive Lias outcrop with the mightiest formation of Posidonia slate in all of Northern Bavaria.
- Formed in the Brown Jura (Dogger) between 175 and 161 million years ago under shelf sea conditions. The Brown Jura consists mainly of iron-rich sandstones, iron sandstone, as well as clays, marls and limes, some of which are mixed with iron oxides and weather brownish. This weathering was made possible by the increased oxygen conditions compared to the Lias. The thickness is up to about 260 meters.
The lowest Dogger step, the Opalinus Clay Formation , consists of predominantly uniform clays and clay stones with individual layers of clay iron geodes (cavities) . The iron in the clays still occurs in the form of pyrite . In the iron sandstone formation above (Dogger beta), seams made of sandstones containing iron oxide are already found.
In the uppermost Great Dane layer, the Sengenthal formation, which is interlocked with the ornate clay formation of the Swabian Alb and other formations further to the west, there are predominantly claystones with a few embedded Eisenoolith banks, glauconitic sandstones and a horizon with limestone concretions as well as oolite limestone and - mergeln.
- The White Jura (Malm) was sedimented about 161 to 150 million years ago at the bottom of a shallow and warm shelf sea, which at that time covered southern Germany. This was an extension of the Tethys Ocean. The deposits mainly consist of limestone, limestone marls and marls, often in alternating layers. The thickness is up to about 600 meters. It represents the classic formation of limestone and dolomite.
The Malmgesteine ranging from bright marls and Mergelkalken the lowermost Malm alpha to the reef - dolomites of Malm zeta. These form the roof of the Frankenalb. The light to white stone colors of the Malm are due to the strong predominance of carbonate stones . With an increasing proportion of clay, the stone colors become grayer. In general, the proportion of clay in the carbonates decreases from the Lower to the Upper Malm. The purest limestones are in the uppermost Malm.
The upper areas of the Malm layers, especially the reef limestone , were secondarily dolomitized by the addition of magnesium and converted into the so-called Franconian dolomite . The original structure of the rock including the fossils was largely unrecognizable, the rock then shows a coarsely crystalline appearance, often described as "sugar-grained". These mighty reef dolomites, together with the table-bank limestone, build the characteristic hilltop landscape of the Alb highlands (Kuppenalb). There are many indications that the dolomite peaks were already carved out of the surrounding rock in the subtropical climate of the older Cretaceous period. On steep slopes, the massive reef dolomites now appear as dirty gray, block-like rock towers with smooth walls, e.g. B. the Müllerfelsen in Wiesenttal near Streitberg .
The basal layer of the White Jura in the Franconian Alb is formed by the Dietfurt Formation, which connects to the Impressamergel Formation to the west . It comprises dark gray to light gray marl limestone with a few limestone banks embedded in it and reaches a maximum thickness of 25 to 125 m. The uppermost Franconian deposits are in the Rennertshofen Formation and the uppermost Neuburg Formation.
In the White Jura there are three types of limestone deposits: the stratified limestone facies, also known as working limestone or bench limestone facies, the mass limestone facies and the plate limestone facies. They are an expression of different lime formation and lime binding.
- The stratified limestone facies generally consist of a lower package of clay marls to marl limestone and an upper section of limestones that are mostly very evenly banked. The lithological transition between the two sections is fluid and the carbonate content rises more or less continuously. During the sedimentology of the stratified limestone facies , biogenically produced and chemogenically precipitated carbonates were formed, which mixed in the lower marl limestone facies with different levels of clay . The carbonate of the stratified facies essentially comes from the very small plankton , the so-called nanoplankton. This includes u. a. Diatoms , flagellates , dinoflagellates and yellow-green algae . Another biogenic formation process took place through the metabolism of organisms. The chemogenic precipitation of the carbonates was mainly caused by changes in temperature and concentration of the seawater. As a result, thinner layers develop in the same time units.
- The unbanked mass limestone facies represent a biogenic carbonate formation that originates from living beings with calcareous shells or skeletons of the pelagic , the open water area far from the shore and the benthal , the living area on and in the ocean floor . In particular, there were sponges , algae , arm pods (brachiopods), mussels and sea urchins and cephalopods such as ammonites and belemnites . The calcareous sponges growing on the thresholds of the seabed have been able to form large bio-thermal sponge reefs with algae crusts over the course of millions of years . They represent the main part of the mass limestone (see also the corresponding geotope display board).
- The plate limestone facies formed between depressions of the bio-thermal sponge reef elevations of the mass limestone facies. Initially reefs and depressions were flooded and the water was in contact with the open sea; there was good water exchange and water circulation. Biostromes , flat sponge lawns, populated the slopes and floors of the reef elevations. With temporary slight regression of the sea level, areas with island groups ( archipelagos ) and lagoons formed . The exchange of water in the lagoons was impeded, which led to stagnation and a lack of oxygen in the bottom water with salt enrichment. Upper reef areas died. The fine-grained to muddy micritic sediments sinking to the bottom formed thin layers in the lagoons that were overgrown by microbes and, as it were, sealed off. After fresh water was fed into the lagoons, further sediment deposits formed, so that a stack of plates was created from a multitude of layers from millimeters to centimeters thick. The Plattenkalke date from around 155 to 150 mya. Dead organisms in an exceptionally good condition have fossilized between individual plates. The Solnhofener Plattenkalke and the Wattendorfer Plattenkalke are known .
Development in Chalk
The rocks of the White Jura have been subject to karstification since the Cretaceous period, from 145 million years ago. The name karst was derived from the eastern hinterland of Trieste ( northern Italy ), in which a geologically similarly structured limestone mountains appear. During karstification, it is primarily the limestone and dolomite rocks that are dissolved by the precipitation water enriched with carbon dioxide, which comes from the air and the topsoil . A small part of the substances dissolved in this way are deposited above ground, but most of them are discharged underground with the water. The insoluble components that are usually also present can gradually accumulate on the surface of the earth and then form the often loamy cover of the Alb cover. Such a covering of clay is called “covered” karst, in contrast to “bare” karst, where the rock is exposed. The karstification continues recently and is not yet complete.
In the Lower Cretaceous, southern Germany was tectonically elevated and the Franconian Alb became mainland. Under humid tropical climates, the Malm table was heavily karstified and largely removed and the typical cone karsts (conical erosion forms) formed. Other erosion phenomena are extensive cave systems reaching deep into the subsoil , e.g. B. the Teufelshöhle near Pottenstein , the Poljen (elongated, closed, trough-shaped, larger depressions in the ground with temporary lakes), the sinkholes (shallow, funnel-shaped smaller terrain depressions of different sizes) (see also the Fellnerdoline geotope display near Gößweinstein , Upper Franconia ), Ponore (swallow holes , into which a flowing or standing body of water flows and continues underground), e.g. B. the Teufelsbrunnen near Eckersdorf / Donndorf, Upper Franconia, (see also the corresponding geotope display board) the carts (solution channels in various forms), (see also geotope display board) Druidenhain near Wohlmannsgesees, Upper Franconia, the dry valleys (mostly dry valleys, but episodic fed during periods of heavy precipitation or after the snow has melted) by tumblers (also known as hunger wells ) and other karst forms. Caves mark the underground path of water from the karst surface to the groundwater receiving water . The water, which mostly runs underground, still causes a lack of water on the Alb plateau today.
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With the beginning of the Upper Cretaceous, sea invasions began from today's Eastern Alps - Carpathian region to Eastern Bavaria . The first sea advance in the lower Cenomanian about 100 million years ago probably followed a narrow erosion furrow along the pile zone and penetrated into what is now the central and northern Upper Palatinate , presumably even to Hollfeld in the northern part of the Franconian Alb. The Upper Cretaceous sediments completely buried the Lower Cretaceous karst relief. With the entry of the sea water into the valleys of the Jura Mountains, the karst water level in the Malm table also rose. There, the iron-rich weathering masses stored in the caves were transported to the water-filled poljes, to the sea-flooded valleys on the eastern edge of the Jura and to the Upper Palatinate Bay (see also Upper Palatinate Hügelland ). At the end of the Upper Cretaceous the sea withdrew again. The area became mainland and the erosion process began, which is still ongoing.
Development in the Palaeogene and Neogene
In the early Palaeogene , extensive karstification of the Malm table began again under tropical climatic conditions. Over the course of millions of years, the upper chalk sediments were increasingly removed, so that the lower Cretaceous relief was partially exposed again and further corroded and eroded .
Of the higher-lying Cretan cave systems, which were temporarily reactivated and then dried up again, only remnants remained, which today lie on isolated mountain tops and often only have a thin roof. The first construction of today's (dry) valley systems probably took place in the Miocene , 23 million years ago. The almost complete evacuation of the chalk sediments and thus the rediscovery of the lower Cretaceous Malmkarst surface took place at the beginning of the Pliocene from 5.3 million years ago. The rough features of today's landscape emerged until the end of Neogens .
Development in the Quaternary
In the Quaternary there was a sequence of cold (glacial) and warm (interglacial) periods during the Pleistocene (approximately from 2.6 to 0.012 million years ago ). Southern Germany experienced the Günz , Mindel , Riss and Würm Ice Ages . The Franconian Jura was between these Alps - glaciers and the northern ice cap . The Alb area was characterized by a tundra and cold steppe, similar to today's Siberia . Deep layers above a permafrost were subject to a series of thaws and renewed freezes. These changes worked up the rock horizons, and the soil, which was very watery in summer, migrated down the slopes as floating earth and block debris . Long-lasting, icy winds blew the weathered rock material as drifting sand or loess and deposited it again in sheltered locations.
The rivers could not saw their way into the depths above the permafrost, but they were very watery during the thawing periods in summer. In line with the cyclical climate, accumulations developed in the valleys during the cold periods. Deep erosion was again possible in the warm periods.
In the Holocene , the current period (from 0.012 million years ago), deposits of drifting sand and dunes formed .
Alb cover
Large parts of the Alb plateau are covered with a loamy-clay layer. The so-called protective field layers from the Cretaceous period, which consist of brightly colored, often bright red, occasionally coarse-sand to kaolinite clay, are often located under this Alb cover . From these sediments it is concluded that the karst landscape of the Franconian Alb was at least partially formed in the Lower Cretaceous and is therefore over 100 million years old. In the Upper Cretaceous, the colored earths were also formed under lateritic weathering conditions, which were mined at Amberg , Pommelsbrunn and Betzenstein , among others , until modern times.
The loamy-clayey Alb cover was created under the tropical climate of the Paleogene through the weathering of Malm limes and marls. The loam of the Alb cover was redistributed during the glacial periods by soil flow processes ( solifluction ) and mixed with less weathered Malm residues and Cretaceous remains. Today, the mostly 5 to 15 meter thick Alb clays and loams are mostly stored over banked limestone and rarely reach over the dolomite deposits.
In the loams and clays of the Alb cover there are regionally varying concentrations of red-brown to black, pea to bean-shaped ore spheres up to about 2 cm in diameter. These so-called floor ores are brown iron ore - concretions that owe their formation to iron ore precipitation from weathering solutions in the soil. Probably as early as the Hallstatt period (from around 800 BC) these floor ores were mined in many ore pits and smelted into iron.
Although the Alb cover is not very thick, it is often used for agriculture . The Kalkscherbenäcker have emerged as a characteristic feature. They are characterized by a large number of limestone fragments or shards present on the surface. These are repeatedly brought to the surface by forestry and soil cultivation, make field work more difficult and reduce the yield.
Both the Cretaceous protective field layers and the paleogenic clays of the Alb cover act as water-retaining horizons on which the rainwater can collect in small pools .
Effects of karstification
The most striking feature of karst regions is the extensive lack of surface rivers. The drainage of these landscapes has been underground for millions of years. The precipitation sinks into the fissures and crevices of the carbonate rocks , whereby these separating joints in the mountains constantly widen under the influence of the carbon dioxide contained in the precipitation water and over the course of millennia they sometimes become considerable underground cavities. The interplay of aboveground and underground dissolution and drainage created the charming and small-scale karst landscape of the Franconian Alb on the limestone and dolomite rocks over millions of years.
During the Holocene , the previously barren tundra and cold steppe soil was again increasingly populated by bushes and trees . This formed the basis for human settlement. In the 16th century BC, in the so-called Subboreal (from 3,710–450 BC), most of the arid valleys of the Alb plateau still carried water. Some of them were still water-bearing until the Middle Ages . Today's river valleys were mostly swampy and unsuitable for permanent settlement. The water supply of the Alb plateau, which was still relatively good at the time, was therefore better suited for their settlement. Remains of settlements date from the Barrow Bronze Age (from around 1,600 BC). They are often located above the former spring pots in today's dry valleys. Later, built in the early Hallstatt period (from about 800 v. Chr.), The Celts their homes and built on the Dolomite peaks of the Alps impressive hilltop castles and Viereckschanzen .
The intensive karstification phenomena in the limestone, marl and dolomites of the White Jura strata caused extreme water poverty on the Alb, from which the population on the entire Alb plateau suffered for centuries. The karst plateau is predominantly made up of highly water-permeable dolomite peaks, which are separated by large dry troughs. Only the floors of the karst tubs made up of the brown allohms and loam of the protective field layers could hold back water.
The localities on the Alb plateau were therefore preferably built on these - only regionally widespread - water-retaining layers. The surface water collected in existing pools or in created shells (earth pits). These covers were used to cover the minimum water requirements of humans and animals. In addition, the rainwater was collected from the roofs of houses in cisterns or, with a lot of effort, was carried out of streams in valleys, often over steep paths, with a cart or with human power. This water shortage with the mostly bad and health-endangering water in the covers and cisterns resulted in a very low population and high child mortality. The cattle were also affected. It was often sick, emaciated, and overworked.
There was no pipe network water supply for the villages before about 1938 due to lack of money. It was only after the Second World War that the American troops stationed here expanded to the size it is today. In the period that followed, the infrastructure was expanded and tourism developed. The residents benefited from this to an increasing extent.
Hydrology
In the case of the underground aquifer, the impermeable layer, the groundwater non-conductor , or also called the aquifuge, and the groundwater conductor , also known as the aquifers, are of particular importance. The aquifer forms the bottom of the flow of water, while the aquifer with its pores, crevices and other cavities allows water to flow. These layers lie on top of one another in an alternating layer sequence, and the layer thicknesses can in some cases vary greatly. Usually the groundwater non-conductors are much less thick.
Karst hydrographically, three main waterways can be distinguished in the Franconian Alb: The deeply cut, partly canyon-like main valleys with perennial rivers, the extensive dry valley systems on the plateaus that only lead to snowmelt or after heavy rainfall and the separating surface structure formed in the mountain body, which indirectly leads to the formation of the waterway seeds (e.g. caves, ponors, sinkholes, karst springs) and the layout of the (dry) valleys.
The main water-bearing valleys of the Franconian Alb are cut deeply into the karst mountains and, with their abundance of water, are in stark contrast to the waterless plateaus of the Alb. The main valleys mark the receiving water level in the deep karst : here the water flowing in the surrounding karst mountains emerges again over partly strong karst springs.
The dry valley systems that are very pronounced in the Franconian Alb are geared towards today's water network; they are much more closely meshed than the current valley networks of the neighboring non-karstified areas. The dry valleys show all geomorphological forms of fluvial erosion. These dry valley systems were formed under ice age conditions by the melt water flowing off the surface over the karst cavities closed by permafrost .
There are several hydrologically independent aquifers in the Franconian Alb area . From the lying (below) to the hanging wall (above) these are the Burgsandstein, the Rhätsandstein, the Doggersandstein, the Malmkarst and - subordinate - the Quaternary valley fillings.
In the foothills of the Alb, above all, Burgsandstein and Doggersandstein are rich aquifers, from which numerous perennial springs that carry water all year round arise. The clay-like Feuerletten of the Trossingen Formation represents the groundwater cover layer of this aquifer and at the same time the groundwater bed of the Rhätsandstein aquifer.
In the Dogger sandstone above, the underlying Opalinus Clay formation (Dogger alpha) is impermeable to water and represents the bottom of the Dogger aquifer. The banked and mostly well-fractured iron sandstones of the Dogger beta are groundwater-conducting.
The Disciteston in the upper part of the Doggersandstein acts regionally as another aquifuge. The following sandstones of the uppermost Dogger beta as well as the oolite limestone and marl limestone of the Dogger gamma to epsilon also have groundwater-conducting properties.
The ornate clay formation of the Dogger zeta, together with the limestone marls of the Malm alpha, forms an aquifuge that hydrologically separates the Dogger aquifer from the overlying Malm karst aquifer.
The higher Malm layers predominantly form a continuous groundwater storey. Only in the Malm gamma are the layered carbonates intercalated with limestone marl layers, so that regional "floating groundwater layers" can occur here. In its entirety, the Malm Aquifer represents a mighty, abundant karst water reservoir, which is increasingly endangered due to the karst-specific surface drainage and the associated input of pollutants .
Fossils
In Jura is multifaceted developed in the then prevailing warm climate life of fauna and flora on land, at sea and in the air. In the rocks of the Franconian Alb, a large number of them have been preserved in the form of fossils , often with an impressive level of detail.
Fossil sites and localities
The fossil deposits and sites are in clay pits , quarries , (large) construction sites - outcrops or spoil heaps , e.g. B. of ICE - tunnels or the waterway of the Rhine-Main-Danube Canal , as well as surface deposits.
Particularly well-known are the Wattendorf limestone from a quarry near Wattendorf near Bamberg and the Solnhofen limestone from the Weißenburg-Gunzenhausen district and the Eichstätt district . They are characterized by a wide range of fossils with the finest degree of preservation.
Fossilized living things
Practically all living things of that time have been preserved as fossils. A small selection is listed below as an example.
Ammonite Pleuroceras spinatum
Ichthyosaurs Leptopterygius trigonodon , ( Leptonectes ) skull and bones
Sea lily Isocrinus basaltiformis , finely branched tentacles
Starfish Pentasteria sp
Ammonites Homoeoplanulites , syn Choffatia
Nautilidae Pseudaganides
Ammonite Parkinsonia , longitudinal section
Gervilleia hartmanni crumbly shell
Sea snail Purpurina serrata
Belemnite rostrum with part of the phragmocone
Bridge lizard, indefinite
Tortoise Eurysternidae, juvenile ventral side
Archeopteryx lithographica paris
Angel shark Pseudorhina sp.
Bone fish Proscinets sp.
Crayfish Soleryon schorri
Diorama of different glass sponges
Coral stick
Stenophlebia spec. Solnhofen
Bennettitales Zamites frond
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Geotopes
A selection of geotopes illustrates various geological, geomorphological and hydrological formations and manifestations:
- Lias, Dogger
- Doggerfelsen Niederhofen
- Former quarry NE from Sengenthal from Dogger Zeta to Malm Delta.
- Malmschichten on the Arzberg
- Sponge limestone cliffs of the mass limestone facies Streitburg near Streitberg
- Honorary civic rock made of Franconian dolomite on the Walberla mountain ENE von Wiesenthau
- "Quackenburg" with "Quackenschloss" made of Franconian dolomite with brachiopod fossils, SSW from Engelhardsberg
- Sintered terraces on the Lillach ESE from Weißenohe made of Werkkalk (Malm Beta)
- Impact slope of the Main SW of Nedensdorf ("Trimeusel"), posidonia layers (Lias Epsilon)
- Lias outcrop in the Teufelsgraben S of Oedhof / Eckental from Posidonia layers and Amaltheenton.
- Oil shale exposure NNW of Hetzles from Posidonia layers (Lias Epsilon).
- Law profile Staffelberg
- The Hetzlas or Hetzleser Berg
- Mistelgau fossil pit with the “Belemnitenschlachtfels”, Lower Jura
- Solnhofen limestone fossil site , Upper Jura
- Cave (D99) in the Fellner sinkhole SE from Gößweinstein , Upper Franconia from Frankendolomit (Upper Jura)
- Druidenhain SW of Wohlmannsgesees, Upper Franconia from Frankendolomit (Upper Jura)
- Wasserberg near Pegnitz , Ponor cave in Malm alpha and beta
Web links
- Internet presence Trias Verein Thüringen e. V.
- Alfons Baier: The karstification. In: Publication of the Friedrich-Alexander University Erlangen, GeoZentrum Nordbayern. applied-geology.geol.uni-Erlangen PDF
- State environmental portal Environment Navigator Bavaria Geological overview Bavaria. [2]
Individual evidence
- ↑ Alfons Baier: A short history of the Franconian Alb. In: Publication of the Friedrich-Alexander University Erlangen, GeoZentrum Nordbayern. applied-geology.geol.uni-Erlangen PDF
- ^ Walter Freudenberger: Overburden north of the Danube. In: Landesumweltportal Umwelt Navigator Bayern, Die Tektonik der Süddeutsche Großscholle. [1]
- ^ Alfons Baier: Tectonics of the Franconian Alb. In: Publication of the Friedrich-Alexander University Erlangen, GeoZentrum Nordbayern. applied-geology.geol.uni-Erlangen PDF
- ↑ Gottfried Hofbauer: The geological history of the region - basic features from a current perspective. In: Naturhistorische Gesellschaft Nürnberg e. V., Annual Reports 2003, Nuremberg 2004, pp. 101–144, ISSN 0077-6025 Nature and Humans georegion-francs PDF
- ^ M. Franz, B. Niebuhr and A. Zeiss: Sengenthal formation. In: Lithographisches Lexikon LithoLex, Lithostratigraphic Units Germany. Archived copy ( memento of the original from October 3, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ Birgit Niebuhr: Dietfurt formation. In: Lithographisches Lexikon LithoLex, Lithostratigraphic Units Germany. Archived copy ( memento of the original from October 3, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ Jung: Rennertshofen formation. In: Lithographisches Lexikon LithoLex, Lithostratigraphic Units Germany. Archived copy ( memento of the original from October 27, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ Jung: Neuburg formation. In: Lithographisches Lexikon LithoLex, Lithostratigraphic Units Germany. Archived copy ( memento of the original from October 27, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Bavarian State Office for the Environment, website lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment, Health and Consumer Protection lfu.bayern PDF
- ↑ Geotope display board of the local action group Kulturerlebnis Fränkische Schweiz e. V. cultural experience PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
- ↑ Geotope display board of the Bavarian State Ministry for the Environment lfu.bayern PDF
