Editing Franconia (section)

==== General ====
[[File:Grube Wilhelmine 4.jpg|thumb|Opened-up, copper-ore-bearing, Spessart crystalline rock in [[Sommerkahl]] near Aschaffenburg]]
[[File:Seltenbachschlucht.jpg|thumb|Fine sandstone, siltstone and argillites of the [[bunter sandstone]] layer (Lower Triassic) in the [[Seltenbach Gorge]] in the Spessart]]
[[File:Judenhof+Turmkarst Tüchersfeld.jpg|thumb|Tower-like rocks of [[Upper Jurassic]]-[[Corallian Limestone]] in [[Tüchersfeld]], northern Franconian Jura (Franconian Switzerland)]]
Only in the extreme northeast of Franconia and in the Spessart are there [[Variscan]] [[outcrop]]s of the crystalline [[basement (geology)|basement]], which were uplifted from below the surface when the [[Alps]] exerted a northwards-oriented pressure. These are rocks of pre-[[Permian]] vintage, which were folded during various stages of [[Variscan orogeny]] in the [[Late Palaeozoic]] - before about 380 to 300&nbsp;million years ago - and, in places, were [[metamorphism (geology)|metamorphosed]] under high pressure and temperature or were crystallized by ascending [[magma]] in the [[Earth's crust]].<ref name="geobavaria_S4">Stefan Glaser, Gerhard Doppler and Klaus fword (eds.): ''GeoBavaria. 600 Millionen Jahre Bayern. Internationale Edition.'' Bayerisches Geologisches Landesamt, Munich, 2004 ([https://www.bestellen.bayern.de/shoplink/93019.htm online] {{Webarchive|url=https://web.archive.org/web/20160304073250/http://www.bestellen.bayern.de/shoplink/93019.htm |date=2016-03-04 }}), p.&nbsp;4</ref> Rocks which were unchanged or only lightly metamorphosed, because they had been deformed at shallow crustal depths, include the [[Mississippian (geology)|Lower Carboniferous]] shale and greywacke of Franconian Forest. The Fichtel mountains, the Münchberg Plateau and the Spessart, by contrast, have more metamorphic rocks ([[phyllite]], [[schist]], [[amphibolite]], [[gneiss]]). The Fichtel mountains are also characterized by large [[granite]] bodies, called post-kinematic [[Pluton (geology)|plutons]] which, in the late phase of Variscan orogeny, intruded into the metamorphic rocks. In most cases these are S-type granites whose melting was caused by heated-up sedimentary rocks sunk deep into the Earth's crust.<ref name = "geobavaria_S24">Stefan Glaser, Gerhard Doppler and Klaus fword. (eds.): ''GeoBavaria. 600 Millionen Jahre Bayern. Internationale Edition.'' Bayerisches Geologisches Landesamt, Munich, 2004 ([https://www.bestellen.bayern.de/shoplink/93019.htm online] {{Webarchive|url=https://web.archive.org/web/20160304073250/http://www.bestellen.bayern.de/shoplink/93019.htm |date=2016-03-04 }}), p.&nbsp;24</ref> While the Fichtel and Franconian Forest can be assigned to the Saxo-Thuringian Zone of Central European Variscan orogeny, the Spessart belongs to the Central German Crystalline Zone.<ref name="geobavaria_S4"/> The Münchberg mass is variously attributed to the Saxo-Thuringian or Moldanubian Zones.<ref>Alfons Baier, Thomas Hochsieder: ''[https://www.angewandte-geologie.geol.uni-erlangen.de/muenchbe.htm Zur Stratigraphie und Tektonik des SE-Randes der Münchberger Gneismasse (Oberfranken)] {{Webarchive|url=https://web.archive.org/web/20160907001253/http://www.angewandte-geologie.geol.uni-erlangen.de/muenchbe.htm |date=2016-09-07 }}.'' Website of the University of Erlangen-Nuremberg with a summary of the essay of the same name in the ''Geologischen Blättern für Nordost-Bayern'', Vol. 39, No. 3/4, Erlangen, 1989</ref>

A substantially larger part of the shallow subsurface in Franconia comprises [[Mesozoic]], unmetamorphosed, unfolded rocks of the [[South German Scarplands]].<ref name="geobavaria_S26">Stefan Glaser, Gerhard Doppler and Klaus Schwerd (eds.): ''GeoBavaria. 600 million years Bavaria. International Edition. GeoBavaria. 600 Millionen Jahre Bayern. Internationale Edition.'' Bayerisches Geologisches Landesamt, Munich, 2004 ([https://www.bestellen.bayern.de/shoplink/93019.htm online] {{Webarchive|url=https://web.archive.org/web/20160304073250/http://www.bestellen.bayern.de/shoplink/93019.htm |date=2016-03-04 }}), p. 26</ref> The regional geological element of the South German Scarplands is the Franconian Platform (''Süddeutsche Großscholle'').<ref>Dickinson, Robert E (1964). ''Germany: A regional and economic geography'' (2nd ed.). London: Methuen, p 568. .</ref> At the so-called [[Franconian Line]], a significant [[fault (geology)|fault line]], the Saxo-Thuringian-Moldanubian basement was uplifted in places up to 2000&nbsp;m above the Franconian Platform.<ref>Walter Freudenberger: ''Tektonik: Deckgebirge nördlich der Donau.'' In: Walter Freudenberger, Klaus Schwerd (Red.): ''Erläuterungen zur Geologischen Karte von Bayern 1:500&nbsp;000.'' Bayerisches Geologisches Landesamt, Munich, 1996 ([https://www.bestellen.bayern.de/shoplink/10000.htm online] {{Webarchive|url=https://web.archive.org/web/20160304075943/http://www.bestellen.bayern.de/shoplink/10000.htm |date=2016-03-04 }}), p.&nbsp;259-265</ref> The western two-thirds of Franconia is dominated by the [[Triassic]] with its [[sandstone]]s, [[siltstone]]s and [[claystone]]s (so-called [[siliciclastic]]s) of the [[bunter sandstone]]; the [[limestone]]s and [[marl]]s of the [[Muschelkalk]] and the mixed, but predominantly siliciclastic, sedimentary rocks of the [[Keuper]]. In the [[Rhön]], the Triassic rocks are overlain and intruded by [[vulcanite|volcanic rock]] ([[basalt]]s, [[basanite (rocks)|basanites]], [[phonolite]]s and [[trachyte]]s) of the [[Tertiary]]. The eastern third of Franconia is dominated by the [[Jurassic]] rocks of the [[Franconian Jura]], with the dark shales of the [[Black Jura]], the shales and ferruginous sandstones of the [[Brown Jura]] and, the weathering-resistant limestones and [[dolomite (rock)|dolomitic rocks]] of the [[White Jura]], which stand out from the landscape and form the actual ridge of the Franconian Jura itself.<ref name="geobavaria_S26"/> In the Jura, mostly siliciclastic sedimentary rocks formed in the [[Cretaceous (geology)|Cretaceous]] have survived.

The Mesozoic sediments have been deposited in largescale basin areas. During the Triassic, the Franconian part of these depressions was often part of the mainland, in the Jurassic it was covered for most of the time by a [[marginal sea]] of the western [[Tethys (ocean)|Tethys Ocean]]. At the time when the limestones and dolomites of the White Jura were being deposited, this sea was divided into sponge reefs and intervening lagoons. The reef bodies and the fine-grained lagoon limestones and marls are the material from which the majority of the Franconian Jura is composed today.<ref name="geobavaria_S40ff">Stefan Glaser, Gerhard Doppler and Klaus Schwerde. (eds.): Stefan Glaser, Gerhard Doppler und Klaus Schwerd (Red.): ''GeoBavaria. 600 Millionen Jahre Bayern. Internationale Edition.'' Bayerisches Geologisches Landesamt, Munich, 2004 ([https://www.bestellen.bayern.de/shoplink/93019.htm online] {{Webarchive|url=https://web.archive.org/web/20160304073250/http://www.bestellen.bayern.de/shoplink/93019.htm |date=2016-03-04 }}), p.&nbsp;40&nbsp;ff.</ref> Following a drop in the sea level towards the end of the Upper Jurassic, larger areas also became part of the mainland at the beginning of the subsequent Cretaceous period. During the Upper Cretaceous, the sea advanced again up to the area of the Franconian Jura. At the end of the Cretaceous, the sea then retreated again from the region.<ref name="geobavaria_S40ff"/> In addition, large parts of South and Central Germany experienced a general uplift -or in areas where the basement had broken through a substantial uplift - the course of formation of the Alps during the Tertiary. Since then, Franconia has been mainly influenced by [[erosion (geology)|erosion]] and [[weathering]] (especially in the Jura in the form of [[karst]]), which has ultimately led to formation of today's landscapes.