Editing Thuringian Forest (section)

== Geology ==
=== Overview ===
[[File:Thuringian Forest Geology.png|thumb|left|Geological map of Thuringian Forest]]
Geologically, the Thuringian Forest is defined by a belt of strongly uplifted and deformed [[Metamorphic rock|metamorphic]] and [[igneous rock]] that divides the relatively flat sedimentary plains of the ''Thüringer Becken'' (to the northeast) from similar rock formations in the valley of the [[Werra]] (to the southwest). It consists of a large [[fault block]] in [[Variscan orogeny#Nomenclature|hercynian]] orientation, which consists from [[sandstone]]s and [[Conglomerate (geology)|conglomerate]]s of [[Rotliegend]] age in its western parts (Eisenach trough), followed by [[granite]]s and [[gneiss]]es of the ''Ruhlaer Kristallin'' formation of early [[paleozoic]] origin which were uplifted in the Rotliegend era, and the conglomerates, sandstones, and abundant [[volcanic rock]]s ([[rhyolite]]s and [[andesite]]s) of the Oberhof trough.<ref name = "bergmannsverein"/> Ore deposits associated with the upthrust of the range have been of significant historical importance in the development of the region, for example, the metalworking tradition in [[Suhl]]<ref>{{cite web |url= http://www.eisenstrasse.de/ |title= Erkenntnisse zum Bergbau in der Region Suhl |publisher= Verein für Archäologie und Denkmalpflege e. V. Suhl |access-date= 3 February 2017}}</ref> and the mining history of [[Ilmenau]].<ref>{{cite web |url= http://www.museum-digital.de/thue/index.php?t=sammlung&instnr=19&gesusa=167 |title= Collection: "Der Ilmenauer Bergbau" |publisher= museum-digital thüringen |access-date= 3 February 2017}}</ref>

The uplift of the [[Horst (geology)|horst]]-like fault block was part of the Saxonian tectonic processes and is understood as a long range effect of the [[Alpine orogeny]]. It began in the upper [[Cretaceous]] era and ended in the late [[Tertiary]] after about 40 million years.

Thuringian forest is surrounded on three sides by triassic rocks: the [[Thuringian Basin]] in the northeast, the [[Hesse Highlands]] in the west, and the northeastern parts of the [[South German Scarplands]] in the south, and by the [[Variscan orogeny|Variscan]] rocks of the [[Thuringian Highland]] towards the east. The geological borders differ from the geographical ones insofar, as the Rotliegend rock of the Thuringian forest finds its continuation in the Masserberg and Crock block in [[Hildburghausen (district)|Hildburghausen district]], southeast of the main range, and the rock types of the Thuringian Highland are also found in the Schleuse horst between Schönbrunn reservoir and Schönau, and in the Vesser complex near [[Schmiedefeld am Rennsteig|Schmiedefeld]], an island of Variscan rocks embedded in Rotliegend. While the near-surface rocks of the Thuringian Highland comprise mostly the [[Fold (geology)|folded]] Variscan [[Basement (geology)|basement]], the oldest unfolded overlying strata (dating from the Permosilesian age) of this basement are exposed in the Thuringian forest. Common to both ranges, but also to other low mountain ranges in Central Europe uplifted at the same time, are the bordering [[Zechstein]] deposits which contain [[Bryozoa]] reefs. These stretch especially wide on the northwestern edge of the Thuringian forest, where the landscape park of [[Altenstein Palace]] is located on one of the largest Zechstein reefs in Germany.

=== Eisenach trough ===

[[File:Lower Permian fanglomerate.jpg|thumb|left|Permian conglomerate of the Eisenach formation from an alluvial fan below Wartburg castle]]
The Eisenach trough is part of the much larger Werra basin, which in turn is part of the Saar-Unstrut depression of [[Cisuralian|early Permian]] origin. It was uplifted as one of the fault blocks in the Saxonian tectonic era<ref name="VoigtTIF">{{cite book | author = Sebastian Voigt | title = Die Tetrapodenichnofauna des kontinentalen Oberkarbon und Perm im Thüringer Wald - Ichnotaxonomie, Paläoökologie und Biostratigraphie | location = Göttingen | year = 2005 | pages = 308 | isbn=3-86537-432-8}}</ref> and is filled with Variscan [[molasse]]s, named ''Eisenach formation'' after the location. It consists mostly of monotonous sequences of reddish [[Conglomerate (geology)|conglomerates]] representing a proximal [[alluvial fan]] which originated in debris flows from the Ruhla anticline. Dated in the upper Rotliegend, the Eisenach formation consists of some of the youngest geological units in the Thuringian forest. The lack of volcanic rocks suggests that at the time of the deposition of the Eisenach formation, no significant tectonic processes took place in the Werra basin which was by then a mostly consolidated depositional environment.<ref name="VoigtTIF"/>

=== Ruhla anticline ===
[[File:WAK Ruhla 037a.jpg|thumb|Outcrop of amphibolite and mica schist of the Ruhla Group of the Ruhla Crystalline Complex in a former quarry]]
In the Ruhla anticline the basement rocks, folded in the Variscan era, are exposed. They are named ''Ruhlaer Kristallin'' after the location and are according to [[Franz Kossmat]] considered part of the Central German Crystalline Zone, of which [[Odenwald]] and [[Spessart]] are also constituents.<ref name="HenKat">{{cite book | author = Dierk Henningsen, Gerhard Katzung | title = Einführung in die Geologie Deutschlands | issue = 7th issue | publisher = Spektrum Akademischer Verlag | location = München | year = 2006 |isbn=3-8274-1586-1}}</ref> In the Rotliegend era the region formed the crest of a mountain range where the debris originated that was deposited in the Eisenach trough and the northwestern part of the Oberhof trough.

The sedimentary, volcano-sedimentary, and magmatic rocks which were deposited or formed in the area from the Cambrian until the upper [[Devonian]] were subjected to intense [[Metamorphism|metamorphosis]] during the Variscan uplift and are now mostly present in the form of [[gneiss]] or [[schist]].<ref name="ZehExFu">{{cite book | author = Armin Zeh | title = Exkursionsführer in das Kyffhäuser Kristallin und Ruhlaer Kristallin | year = 2005 | pages = 44 | url = http://www.mineralogie.uni-frankfurt.de/petrologie-geochemie/mitarbeiter/zeh/downloads/exkursionsfuehrerhighquality.pdf }}{{Dead link|date=June 2018 |bot=InternetArchiveBot |fix-attempted=no }}</ref>

=== Oberhof trough ===
[[File:Thuringia Tambach-Dietharz asv2020-07 img29 Falkenstein.jpg|thumb|left|Falkenstein near Tambach-Dietharz, consisting of volcanites of Oberhof formation]]
The Oberhof trough is by far the largest of the main geologic parts of the Thuringian Forest. It consists of the uplifted part of the so-called ''Thuringian Forest Basin'' whose contents can be further subdivided into several formations. Their relative ages have not been fully resolved yet, partly because the Oberhof trough had been a [[rift]] zone with intense tectonics and continual changes of the internal relief and of the main areas of deposition.<ref name="VoigtTIF"/> The tectonic processes were accompanied by an intense [[felsite|felsitic]] volcanism which was the origin of many volcanic rock formations, predominantly rhyolites of [[Porphyry (geology)|porphyric]] structure with accompanying [[tuff]] deposits. These volcanic rocks alternate in sequence with the typical reddish molasse sediments (conglomerates, sandstones, siltstones, and claystones) of the Rotliegend.

=== Little Thuringian Forest ===

The [[Little Thuringian Forest]] (German: ''Kleiner Thüringer Wald'') is a narrow horst south of [[Suhl]] and northwest of [[Schleusingen]], northwest of Schleuse river, embedded in the [[Triassic]] foothills of Southern Thuringia. It is oriented roughly parallel to the Thuringian Forest and, while a separate structure, is geologically very similar to the latter, as it consists of the same rock types such as granite, [[hornfels]], porphyrites, Rotliegend and Zechstein sediments, and thus forms part of the [[Variscan chain]].<ref>{{cite book | author = Martin Meschede | chapter = Deutschland im Perm und Mesozoikum | title = Geologie Deutschlands | pages = 103–159 | date = 24 March 2015 | publisher = Springer | location = Berlin and Heidelberg| bibcode = 2015gede.book.....M }}</ref><ref>{{cite book | author = Maximilian Tornow | title = Die Geologie des Kleinen Thüringer Waldes | publisher = Schade | year = 1907}}</ref> It is about {{convert|11|km|abbr=on}} long and {{convert|1|km|abbr=on}} to {{convert|2|km|abbr=on}} wide, with an average altitude of 460 m. Mining for [[fluorite]], [[baryte]], and [[limonite]] has been attempted there on several occasions, but was given up as unprofitable due to difficult drainage. Large baryte deposits prospected in the 1950s have remained untouched.

=== Waltershausen Foothills ===

The Waltershausen foothills (German: ''Waltershäuser Vorberge'') are a wooded chain of [[Buntsandstein]] hills immediately north of and parallel to the Thuringian Forest between Eisenach, Waltershausen, Friedrichroda, and Georgenthal.  An outcrop of [[Muschelkalk]] rock can be found in their northern part, south of Waltershausen. They are generally regarded a part of the [[Thuringian Basin]],<ref>{{cite book | author = Emil Meynen, Josef Schmithüsen | title = Handbuch der naturräumlichen Gliederung Deutschlands | publisher = Bundesanstalt für Landeskunde | location = Remagen and Bad Godesberg | year = 1953–1962}}</ref> but with numerous deeply eroded river valleys and the dense forestation they resemble very much the Thuringian Forest.