Northern Limestone Alps

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Northern Limestone Alps
Northern Limestone Alps and Grauwackenzone marked here in light blue (Eastern Alpine Mesozoic)

Northern Limestone Alps and Grauwackenzone marked here in light blue ( Eastern Alpine Mesozoic )

Highest peak Parseierspitze ( 3036  m )
location Austria, Germany (Bavaria)
part of Eastern Alps
Classification according to geological-natural
Coordinates , ( CH ) 47 ° 10 '  N , 10 ° 29'  O ( 830.38 thousand  /  229295 ) coordinates: 47 ° 10 '  N , 10 ° 29'  O ; CH1903:  eight hundred thirty thousand three hundred eighty  /  229295
Type Chain mountains , folds and thrust belts
rock Limes (mainly), dolomites and marls
Age of the rock Upper Permian to recent
f1

The Northern Limestone Alps , abbreviated NKA , are a geological section of the Eastern Alps . They extend over 500 kilometers from the Alpine Rhine Valley to Vienna and are between 20 and 50 kilometers wide. Their area of origin was on the southeastern passive continental margin of Eurasia , in which a several kilometers thick succession of sedimentary rocks came from the Permian to the Upper Cretaceous . From the Upper Jurassic onwards, the sediment skin began to detach itself from its base consisting of metamorphic , Austroalpine rocks and slid onto younger sediments of the Eurasian southern rim. Syntectonic sedimentation and ceiling thrusts talked to the Paleogene in.

The highest peak in the Northern Limestone Alps is the Parseierspitze , 3,036  m above sea level. A. , in the Lechtal Alps .

Disambiguation

The Northern Limestone Alps, English Northern Calacareous Alps or NCA for short , are a geological term and thus to be distinguished from the orographic term of the Northern Eastern Alps or Northern Alps . They only make up part of the Northern Alps, on the other hand, with the Rätikon , a whole mountain group of the Central Eastern Alps also belongs geologically to the Northern Limestone Alps.

North of the Limestone Alps are the Flyschberge the Flyschzone that the Alpine foothills reach out there, but between Vorarlberg and Salzburg are largely lacking in the Bavarian region. South of the Northern Limestone Alps lies the Grauwackenzone , which only forms the mountains in the Tyrol / Salzburg and north-western Styria as slate Alps . This means that the Northern Limestone Alps take up most of the Northern Alps, but in the eastern state of Salzburg, for example, they are only half the width of the Northern Alpine range, and even less at the edges in Vorarlberg and near Vienna. In the scientific literature, however, the Grauwackenzone is partly counted as its base ( basement ) in the Upper Eastern Alps of the Northern Limestone Alps.

The limestone of the Limestone Alps - the northern as well as the southern - are deposits of the Tethys Sea around 250-150 million years old . There are also limestone massifs outside the Limestone Alps, for example on Schöckl near Graz, or on Triebenstein , which were formed in a forerunner sea ​​of the Tethys 400–250 million years ago , or the Leithagebirge , which was formed in a very late residual sea of ​​the Thetys around 15 million years ago has been deposited. Such limestone does not belong to the Northern Limestone Alps in the sense of the term. There are also some floes that belong geologically to the limestone Alps, but are not in their area of ​​distribution. Examples can be found around the Pleißlingkeil on the eastern edge of the Tauern window of the central alpine Niedere Tauern or on the Kainach near Köflach on the edge of the Graz basin . During the formation of the Alps, the clods were sheared from the limestone alpine cover and remained in the central alpine region. They are only mentioned in the geological literature under the Northern Limestone Alps.

View from the Seefelder Joch to the Lechtal Alps , Mieming Mountains and Wetterstein massif

geography

At 3,036 meters, the Parseierspitze is the highest point in the Northern Limestone Alps

Demarcation

The Northern Limestone Alps extend from the Alpine Rhine Valley , where they continue in the direction of the Alpstein massif , at a width of 25 to 45 km through Vorarlberg , Tyrol , the Bavarian districts of Swabia and Upper Bavaria , through Salzburg , northern Styria , Upper and Lower Austria to Vienna , where they find their continuation in the Carpathian Mountains after being cut off by the eastward faults of the Miocene Vienna Basin by means of the cliff zone . Its western edge is carved out by erosion - with a few upstream outriggers, the westernmost of which are the Iberg cliffs in Central Switzerland.

In the south, the Northern Limestone Alps are usually accompanied by a distinctive longitudinal furrow. The Rätikon in the far west is without a corresponding demarcation to the south. First the Arlberg line follows in the west, then the Inn Valley to the east from Landeck via Innsbruck to Wörgl . Further east, the furrow runs less prominently via St. Johann in Tirol and Dienten to Bischofshofen , then follows the upper Ennstal again very prominently to the Pyhrn Autobahn . The deep geological disturbance of the Inn-Salzach-Enns line makes use of the valley furrow of the Salzatal , the Palten - Liesing valley further east , and finally the Mur-Mürz furrow to the southeast . The southern border of the northern limestone Alps runs between the respective valley furrows within the mountain groups, sometimes closely interlocked and nested with the Grauwackenzone, and then no longer has any clear orographic delimitation as far as Vienna .

The northern border follows - largely without any orographic significance - the northern edge of the Alps at a distance of 10–50 kilometers. Some stocks, such as the Untersberg near Salzburg, where the limestone Alps break off largely suddenly into the Alpine foothills, have a special position . As a result, many orographic groups that are placed in the Northern Limestone Alps also have parts of the flysch and greywacke zone, which in each case only form foothills. The Vienna Woods , which are divided into the Limestone and Fly Schwienerwald, represent an exception . The Bregenz Forest Mountains , the Kitzbühel Alps , the Salzburg Slate Alps , the Eisenerzer Alps and the Mürz Valley Alps are largely entirely outside the Northern Limestone Alps. Conversely, a number of limestones are assigned to a Central Alps or Slate Alps group, such as the Davenna in Verwall or the Kaiserschild group of the Eisenerzer Alps.

Locally, however, the demarcation can be striking, for example in the Mühlbachtal on the Hochkönig to the Grauwacke, or in the Gschliefgraben on the Traunstein to the Flysch.

structure

In the south-north direction, the Kalkalpen are divided into the Kalkhochalpen in the south and the Kalkvoralpen in the north. The first are mighty high mountains up to just over 3000 m, the second are upstream groups that already have the character of low mountain ranges , but also have prominent limestone peaks.

In a west-east direction, the rough breakdown follows as in the entire northern Alps along the breakthrough valleys (primarily from the Inn , Salzach and Enns , which each bend northwards after their course in the longitudinal valley furrow) in the North Tyrolean Limestone Alps , Bavarian-Salzburg Limestone Alps , Upper Austrian-Styrian Limestone Alps and Styrian-Lower Austrian Limestone Alps . The more isolated, westernmost groups Alpstein and Rätikon are not taken into account here .

The further division takes place in characteristic chains (especially in the west) and solitary sticks (increasingly towards the east). This corresponds to the orographically oriented systems, such as the Alpine Club division of the Eastern Alps  (AVE), the Unified Orographic division  (IVOEA / SUOISA), or the mountain group classification according to Trimmel - with the restriction that the groups specified there also include the Grauwacken, Flysch, Helvetica and molasses shares, and some limestone mountains are assigned elsewhere.

Among the best known largely entirely calcareous groups of Kalkhochalpen include Rätikon, Lechquellengebirge , Lechtal Alps , Wettersteingebirge , Mieminger mountain range , Karwendel , Kaiser Mountains , Lofer and Leogang mountains , Berchtesgaden Alps , Tennengebirge , Dachstein Mountains , Dead Mountains , Gesäuseberge , Hochschwab group , mürzsteg alps and Rax Schneeberg Group .

geomorphology

glacier

The high glacier on the northern flank of the Braunarlspitze
The Höllentalferner from the Jubiläumsgrat

In the Northern Limestone Alps there are only very small and very small glaciers left .

Most of the Northern Limestone Alps are free of glaciers. The remaining glaciers of the Northern Limestone Alps have only a small dimension compared to the glaciers of the Central Eastern Alps or even the Western Alps. In the southern Limestone Alps of the Eastern Alps, however, larger glaciers can be found again.

The glaciers of the Northern Limestone Alps - like many other glaciers in the Alps and around the world - have been in a process of shrinking since 1850 . It cannot be clearly determined whether the annual snow cover of the mountains is also affected by climatic warming. It has not yet been established that the high regions will also be free of snow earlier in the year.

Only a few glaciers that bear this name in the Northern Limestone Alps have the characteristics typical of glaciers, such as crevasses , edge gaps and ice flow . Even if the current climatic trend continues , most of the glaciers in the Northern Limestone Alps will probably have disappeared in 50 to 100 years at the latest.

In the Bavarian language area - in Bavaria and in Tyrol - glaciers are referred to as “Ferner”. In other areas of the Northern Limestone Alps, the High German term is used.

By far the largest glaciers in the Northern Limestone Alps are in the Dachstein Group. The Hallstatt Glacier is the largest glacier in the Dachstein. This sub-group is also home to two other larger glaciers, the Great Gosau and Schladminger Glaciers . The other glaciers in the Dachstein Mountains are now little more than ice fields, such as the Edelgrieß Glacier , the Southern and Northern Torstein Glacier , the Little Gosau Glacier and the Schneeloch Glacier .

The Schneeerner in the Wetterstein Mountains is the largest glacier in Germany . Years ago summer skiing was still practiced here. This glacier has now shrunk to such an extent that it has long since split into two parts, the Northern and Southern Schneeferner. With the Höllentalferner, the Wetterstein Mountains are home to the best-developed German glacier with a multitude of crevasses, edge gaps and glacier tongue. The famous Höllental ascent leads over this to the Zugspitze.

In the Berchtesgaden Alps , the northern roof of the Hochkönig is covered by the Übergossene Alm - a plateau glacier that has recently been showing signs of dissolution. The blue ice on the Hochkalter, which is also severely threatened, is considered to be the northernmost glacier in the Alps. The Watzmann Glacier is also viewed as a glacier by the Bavarian Academy of Sciences . At the foot of the Watzmann east face is the avalanche cone of the ice chapel , the lower end of which is 930 m above sea level and which is therefore probably the lowest ice field in the Alps available all year round.

In the Allgäu Alps , the southern flank of the Mädelegabel is taken up by the Schwarzmilzferner , which has increasingly lost its glacier character due to the strong melting of the last decades. The famous Heilbronner Weg leads directly over the current “little glacier”.

In the Lechtal Alps there is still a real, crevice-rich glacier with visible ice movement: the impressive Vorderseeferner below the Vorderseefitze . There are also other smaller glaciers: The Fallenbacher Ferner below the Feuerspitze , the Parseierferner and the Grinner Ferner at the Parseierspitze, the Pazüelferner on the Trittkopf and the Grießlferner on the northern flank of the Grießlspitze .

In the Karwendel Mountains , on the northern flank of the Eiskarlspitze, there is a small, crevice- rich glacier - the so-called Eiskarln .

In the Mieminger chain , on the south side of the Grießspitzen, there is a small snowman with a few cracks.

Finally, in the Lechquellen Mountains, a small glacier with clear crevasses appears on the northern slope of the Rote Wand , which makes this mountain unmistakable when viewed from the north. Furthermore, the high glacier stretches across the Braunarlspitze .

geology

General

The Northern Limestone Alps belong to the Eastern Alps , more precisely to the Upper Eastern Alps , and consist predominantly of thick sedimentary rocks such as v. a. Dolomite , limestone and marl . The approximately 500 km long mountain range is the result of an enormous thrust of sea ​​sediments from the south. The sedimentary rocks were deposited on older rocks of the Grauwackenzone , which geologically, however, represent a separate unit. It occurs mainly on the southern edge of the Northern Limestone Alps. To the north of the Northern Limestone Alps lie the Flysch Zone, the Helvetic and the subalpine Molasse.

During the mountain formation of the Alps in the period from the Cenomanian to the Oligocene, the limestone nappes were pushed from the south far beyond the edge of the European continent. The Grauwacken rocks at the base of the Northern Limestone Alps represent the remains of a Variscan mountain range that was completely leveled by erosion at the end of the Paleozoic Era and then flooded by the sea.

The spatially insignificant Gosau sediments came to lie in the Upper Cretaceous and the lower Palaeogene on a pile of nappies that was already moving northwards . They are therefore synorogenic and of great importance for dating the orogenic movement sequences.

stratigraphy

Dachsteinkalk des Ramesch , Warscheneckgruppe

Essential components of the Northern Limestone Alps are rocks of the Permomesozoic , to which the Triassic contributed the largest limestone and dolomite masses. The older sediments of the Limestone Alps (Upper Permian to the deeper Jura ) are sequences of a typical passive continental margin . Well-known and powerful formations as well as stratigraphically and topographically striking for the Triassic include the Wetterstein Limestone , the Main Dolomite and the Dachstein Limestone . These limestone and dolomite series form the majority of the highest peaks (such as Watzmann, Hochkönig, Hoher Dachstein , Hochschwab ). Other rocks such as marl , sandstone and slate are less prominent, but the rocks of the Werfen formation (Upper Permian to Lower Triassic) are more widespread in places. The Werfen strata form the boundary between the limestone sediments and the Grauwacke; they are the "sliding layer" over which the northern limestone Alps were pushed northwards, and are accordingly either part of the limestone or slate Alps.

Rocks from the Jurassic era include the Allgäu formation (also known as spotted marl ) and the Oberalmer layers or aptych layers . Most of the strata of the Jurassic are rather thin (especially in the Lower and Middle Jurassic). Pebbly, radiolarian rocks ( Ruhpolding formation ) were deposited in deep sea channels , as they are known from subduction zones , and thus prove the closure of the Neotethys Ocean in the Jura.

The Gosau rocks of the Upper Cretaceous and the Paleogene consist of conglomerates , sandstones , marls and limestones . Their sedimentation took place in intermittent subsidence currents that had formed in front of the folds and ceiling foreheads approaching from the south.

Sedimentary content

Rock salt of the Haselgebirge from the Berchtesgaden salt mine

The Northern Limestone Alps are characterized by the following sequence of layers (from hanging to lying ):

Facies

In the sediment sequence of the Northern Limestone Alps, three facies can be distinguished. From north-west to south-east they show the sequence from the inner shelf via outer shelf to the continental slope of the Meliata Ocean: Bavarian-North Tyrolean facies , Berchtesgaden facies and Hallstatt facies . In general, an increase in thickness towards the Berchtesgaden facies can be observed from both sides. The facies differences mainly concern the sequences of the Permoskyth and the Triassic.

During the Permian period, alpine verrucano was deposited in the Bavarian-North Tyrolean facies area, whereas the mighty Hasel Mountains accumulated in the Hallstatt facies . The Scythian is represented in the Bavarian-North Tyrolean facies by alpine red sandstone , which is however replaced in the two other facies areas by the increasingly marine Werfen formation . In the upper Ladinium, there was a strong subsidence associated with the dissolution of the Meliata Ocean. This caused relative deep water sedimentation of the Reiflinger limestone in the Bavarian-North Tyrolean and in the Berchtesgadener facies area. From now on, the sedimentation of the pelagic Hallstatt limestone began in the Hallstatt facies .

Magmatism

Igneous rocks are virtually non-existent in the Northern Limestone Alps, the only exception being the Ehrwaldites in the Lech Valley blanket south of the Zugspitze massif. These are basanite dike rocks (nepheline basanite) that penetrated Mesozoic sedimentary rocks as far as the Lower Cretaceous in a narrow, almost 50 kilometer long zone ( Puitental ). Their age was determined to be around 100 million years, so they come from the Upper Albium. From their presence it can be concluded that at the time of their magma ascent, there was no subduction zone under the Northern Limestone Alps. Their ascent had taken place under expansion when the Northern Limestone Alps had no roof structure and lay on a continental base, far from a Penninic subduction zone. The rise of the Basanitic Ehrwalditschmelzen is possibly due to a Horst-Graben system - with connections to transpressive tectonics.

Large tectonic stress fields

The Northern Limestone Alps were subject to a polyphase deformation history , which can be divided into three stress regimes:

  • From the Triassic to the Cretaceous, large-scale extension (extension) determined the northwestern edge of the Tethys - as a result of which faults and their segmented leaf displacements developed. The faults are rarely found in the terrain, but they can be reconstructed from differences in thickness or the lack of individual layers.
  • With the end of the Lower Cretaceous and the beginning of the Upper Cretaceous, narrowing (compression) led to the formation of thrusts, several sets of leaf displacements in different orientations, to folds and to actual orogenesis with later isostatic elevation .
  • From the Miocene onwards, post-collisional and gravitationally controlled slippage processes with sideways stretching resulted in the creation of faults, the reactivation of older disturbances and the formation of intramontaneous basins.

Geodynamics

Rauhwacke of the Raibler layers, rubble from the Traun . The very incompetent Raibler layers often form a significant shear horizon.

The Northern Limestone Alps are the largest coherent limestone mass in the Northern Alps, but they are by no means a unified tectonic association. Furthermore, they are alien ( allochthonous ) and have generally slipped northwards from their original area of ​​roots. Together with the underlying Northern Greywacky Zone, they now rest on a strange, Penninic underground. Overall, they represent a huge, heterogeneous fold-and-thrust-belt , the roots of which are likely to be found south of the Hohe Tauern , but north of the current Southern Alps.

Today it is generally accepted that the Northern Limestone Alps are allochthonous. Evidence of this is provided by the Flysch windows, several deep boreholes and seismic depth profiles . At its western end, its all-round underlay by Pennin flysch series can even be seen directly. There, the nature of the ceiling can still be recognized even for its eastern alpine base.

The tectonic development of the Northern Limestone Alps took place in two main stages after the Jurassic movements:

  • In the period from the late Lower Cretaceous to the Upper Eocene , a north-west-Vergent nappes had formed due to transpressive, right-handed shear movements in the orogenic collision wedge of the Eastern Alps .
  • In the Miocene , crust wedges were then pressed out in the central eastern Alps in an easterly direction, as a result of which the shear movements turned into their left-handed opposite.

The transpressive, ie inclined constriction tectonics with a total shortening of 54 to 65 percent manifested itself in the Northern Limestone Alps through northwest-facing nappe thrusts that were created at an acute angle both to the current east-northeast orientation of the orogen and to its northern edge. Blankets and ceiling pleats appeared en-échelon (in a staggered arrangement) and were offset from one another by right-handed lateral shifts in an east-south-east direction. This created a pattern of rhombohedral blocks. The main stretching direction was northeast and ran parallel to the folds and ceiling foreheads, but also to the internal strike direction of the orogen.

The current or post-Miocene spatial disposition of the structures can be explained by a paleomagnetically proven rotation of around 30 degrees clockwise. Immediately before this rotation, which reached its peak in the Campanian 80 million years ago, the main direction of narrowing should have been roughly parallel to the crystal-plastic flow of the central Eastern Alpine, ie in a westerly to west-northwestern direction.

Cover

Allgäu formation of the Allgäu blanket from the Tannheim mountains

Three first-order thrust trajectories can be distinguished within the calcareous alpine nappes, which use facial transitions in the sediment package and the resulting differences in competence. Here, evaporitic layers play an important role as the principal shear horizons, such as the Hasel Mountains with halite and anhydrite , the Reichenhall formation and the Raibler layers without halite but with gypsum . The thrusts mostly took place as so-called ramp-flat structures , the ramps of which ran through rock packs of around 30 °, such as the Wetterstein limestone or the main dolomite. The secondary interior design of the ceiling stack had mainly been determined by pre-existing disturbances .

Geodynamically, the Northern Limestone Alps are therefore divided into three large units - the Bajuvarikum at the bottom , the Tirolikum in an intermediate position and the Juvavikum in the hanging wall.

These large units are then further subdivided, for example the Bajuvarikum into the Cenoman Randschuppe (also Randcenoman ), the Allgäu ceiling and the Lechtal ceiling . The Tirolikum is divided into the Staufen-Höllengebirgs blanket , Inntal blanket (also Inntal-Krabachjoch blanket) and Werfener shed zone . The Juvavikum consists of the Hallstatt ceiling , the Reiteralm ceiling or Berchtesgaden ceiling and the Dachstein ceiling . The lower section of the Juvavikum does not represent a ceiling in the actual sense, but contains deposits in the back of the Tirolikum, into which gigantic olistholiths of the Hallstatt ceiling had slid. The ceilings of the upper section are characterized by thick Dachstein limestone .

To the east of Kufstein, the Tirolikum penetrates diagonally to the northeast towards the edge of the Alps, so that the Bajuvian nappes are crossed and then completely missing in the central section. Further to the east, the Tirolikum swings back to the southeast and the Bajuvarikum appears again in the form of the Ternberg ceiling and the Frankenfels ceiling - the eastern counterparts of the Allgäu ceiling - followed in the hanging wall by the Reichraminger ceiling and the Lunzer ceiling , the equivalents of the Lechtal -Ceiling. Tyrolean ceilings are further east the dead mountain ceiling that Warscheneck ceiling , the rice Alps ceiling , the Unterberg ceiling and Göller ceiling . The Juvavikum is represented here by the Mürzalpendecke and the Schneebergdeck .

In terms of time, the ceiling movements can be broken down as follows:

  • Overturning of the Meliatikum in the Oxfordium 160 million years ago on the Juvavikum and the southern edge of the Tirolikum (across the Allgäu Formation and the Rotkalk group ). Sedimentation of the Strubberg Formation with ultrabasic ophiolite detritus .
  • Slipping of the Juvavikum from the Hallstadt Zone onto the Strubberg Formation of the Tirolikum a little later in the course of the Oxfordian (about 158 ​​million years ago) - at the same time as the deposition of the Tauglboden Formation and the Ruhpolding Formation.
  • Remobilization and thrusting of the already sedimented Juvavikum onto the Rossfeld Formation of the Tirolikum (during the Barremium around 130 million years ago). New entry of ophiolite components.
  • Thrust of the Tirolean onto the Bajuvarikum (Losenstein Formation) with the beginning of the Cenomanian 100 million years ago.
  • Back thrusts on the southern edge of the calcareous Alps in the Upper Paleocene and Lower Eocene 50 to 45 million years ago.
  • Overthrust the tectonic Bajuvarikums auflagernder systems Randcenoman, Rhenodanubikum and finally Molasse in lutetium / bartonian 40 million years ago. In the Tirolikum further internal ceiling construction through the formation of new shear lines, which reach down to the underlying Bajuvarikum in the west. Ingression of the inner-alpine molasses and deposition of the Inntal group around Kufstein and Bad Reichenhall .

metamorphosis

The first metamorphic events had already started in the Eastern Alps in the Oxfordian and Kimmeridgian 160 to 150 million years ago and induced a blue schist metamorphosis in the sedimentation area of ​​the Meliata Ocean . The actual Austroalpine was then affected by an eclogite metamorphosis in the Cenomanian and Turonian between 100 and 90 million years . The warm front then gradually moved further north-west and reached the Penninic in the Lutetian between 49 and 40 million years, the Valais Ocean in the Lutetian and Bartonian between 45 and 37 million years and the continental European northern rim between 42 and 31 million years. The metamorphosis ended in the Eastern Alps in the Rupelian (Upper Oligocene).

However, since the Northern Limestone Alps form the uppermost and most northerly nappe unit of the Eastern Alpine nappe stack, they were as good as not subjected to metamorphic stress. An exception is its southern edge, which documents weak anchimetamorphic changes ( zeolite facies with temperatures up to 250 ° C), which mainly affects the siliciclastic sediments of the Permoskyth. Very low to low degrees of metamorphosis were achieved, as evidenced by the illite crystallinity. The age of this metamorphic event could be determined to be 154 million years (Kimmeridgian). It is believed to be related to the closure of the Meliata Ocean.

Work with the help of the Conodont color change index was able to prove a further thermal event in parts of the Juvavian nappes, which even preceded the oldest thrust faults in the Upper Jurassic. In the Hallstatt limestone of the Pailwand near Abtenau , Gawlick and Höpfer (1996) even found signs of a medium-temperature-high pressure metamorphosis for the period from the Middle to early Upper Jurassic.

Furthermore, a metamorphosis of the Barrow type could be detected in the Lower Cretaceous, the age of which is centered around 90 million years (Turonium). New formations were the minerals pyrophyllite and pumpellyite at temperatures of around 200 ° C. The trigger was the subduction of continental basement, which included the southern edge of the Northern Limestone Alps.

Paleogeography and plate tectonic evolution

General

The general eastward drift of the African plate is responsible for the formation of the Alps
Plate tectonic reconstruction in the Ladinium 230 million years ago - before the opening of the Atlantic. The carbonate platform of the Wetterstein Limestone was created in the Northern Limestone Alps.

Pitman and Talwani (1972) and Dewey et al. (1973) had already investigated the relative movements of the African and Eurasian plates using the magnetic anomalies in the Atlantic. For the period 180 to 80 million years ( Toarcium to Campanium) they found a general south-east movement of Africa towards Eurasia, which from 148 million years ago (Jurassic / Chalk line) additionally induced a strong dextral shear through a slight rotation to the northeast. The general eastward drift changed abruptly from 81 million years ago (Campanian) and turned in a west-northwest direction of Africa towards Eurasia. This was preceded by the opening of the North Atlantic by 95 to 90 million years (Turonian). This reversal of direction induced a relative northward movement in Africa at the beginning of the Upper Cretaceous. The westward movements of Africa lasted until 53 million years (Lower Eocene). From 53 million years ago to the present day, Africa then turned north towards Eurasia. The result was the continental collision (Alpine main phase) in the Upper Eocene and Oligocene .

A large part of the limestone Alps was deposited on the northern continental shelf of the Adriatic Plate ( Adriatic or Apulian Plate ) in the period from Upper Permian to Lower Jurassic . The latter formed a spur protruding to the north, which geologically belonged to Africa . The geodynamic movements of the African Large Plate and the Adriatic Microplate in between should ultimately be of decisive importance for the formation of the Alpine Orogen.

The Hallstatt Zone and, further to the southwest, the Meliaticum are often attached to the actual deposit area of ​​the Northern Limestone Alps . The Hallstatt zone was on diluted continental crust and formed the shelf edge to the western reaches of the Tethys in the southeast - the Meliata Ocean (or Meliata-Maliac Ocean ). This was a western edge basin of the Tethys, which had opened from the anisium . From this point on, the deposit areas of the Austroalpine and Southern Alps formed the north-western continental margin to the Meliata Ocean. The shelf platform further northwest was the sedimentation area of ​​the Northern Limestone Alps, which was located in the Upper Triassic at around 28 degrees north latitude.

In the meantime, however, Handy et al. (2010) differentiate the small plate Alcapia , located north of the Adriatic , as a depository of the limestone sediments. This small plate merged with its southeastern continental margin (the Hallstatt Zone) into the Meliata Ocean, which in turn was subducted to the southeast under the Vardar Ocean at the end of the Triassic (the Vardar Ocean was to remain until the end of the Upper Cretaceous). This created an arch of the island that collided with Alcapia in the Upper Jurassic, pushing ophiolites towards the continent. These Upper Jurassic ophiolites are now in the Dinarides , but were eroded away in the Austroalpine during the Cretaceous and can only be detected as exotic components in the Gosau sediments.

A left-handed lateral shift , an early forerunner of the Periadriatic Seam , separated Alcapia from the Adria to the south. In the north, Alcapia was separated from the small plate Tiszia by staggered fractures . Relay breaks also separated Alcapia from Eurasia (or Europe), where the Penninic Ocean would later invade.

Movement sequence

Plate reconstruction for the tithonium 150 million years ago

The first tectonic movements go back to the Central and Upper Triassic and impaired the Upper Permian Hasel Mountains. The great differences in thickness in the overlying Hallstatt Formation and the Hasel mountain rubble ( olistholiths ) that have been relocated in it indicate the local formation of salt rollers, salt cushions and salt covers in the subsurface. This tectonic event was then sealed by the shallow marine, Upper Jurassic Plassen Formation.

From the Middle and Upper Jurassic onwards, sedimentary rocks were first stacked on the Adriatic Plate - caused by the closure of a sea ​​basin at the western end of the Neotethys , the so-called Meliata Ocean (or Meliata-Maliac-Vardar Ocean ), which was formed by the ocean floor spreading in the Upper Triassic ( Carnian ) 220 million years ago. The Meliata Ocean had been subducted to the southeast under the Vardar Ocean (Neotethys), so that an advancing accretion wedge with ophiolithic blankets (the current classic Hallstatt facies) was pressed (autopsied) towards Alcapia . At the same time, evaporites from the Hasel Mountains were injected into deep sea basins, where tectonically reprocessed in places. These early Upper Jurassic, compressive movements are often referred to as the Cimmerian phase (around 160 to 150 million years ago).

After crustal strain in the lower Jurassic and lower Middle Jurassic unfolded from the Bathonian and Oxfordian an estuary, located between the southeastern continental margin of Eurasia and Alcapia had urged and thereby established a link between the young central north Atlantic Ocean and Tethys in the east. This estuary is known as the Piedmont-Liguria Ocean or Alpine Tethys . The partly oceanic rocks of the Penninic were deposited in it - ophiolites and the radiolarites that covered them . The first rift movements on this estuary (so-called rifting ) began 170 million years ago in the Lower Jurassic ( Bajocium ). The spreading of the Piedmont-Liguria Ocean, which was relatively slow at 21 millimeters / year, was to continue for 130 million years. The rift had advanced south of Iberia as a left-shifting transform fault to the east and then widened to the actual Piedmont-Liguria Ocean spreading to the northeast. The resulting ocean was lined on its northeast side by the ribbon-shaped small plate Alcapeca (acronym for Alborán Sea , Kabylia , Monti Peloritani and Calabria ). How the ocean advanced to the east in the direction of Tethys is not clear, at least it girded the small continent of Cervinia in its northern section .

In this context, it should be mentioned in passing that from the Jura / Cretaceous border 146 million years ago rift fractures formed on the left side of the Piedmont-Liguria Ocean, which broadened to spread the Valais Ocean from the Barremium 130 to 125 million years ago . The space in between was occupied by the Briançonnais plateau. During the Lower Cretaceous the spreading North Atlantic had worked its way up to the level of the Biscay and penetrated further east along the Pyrenees to the Valais Ocean. The Valais Ocean spread up to 92 million years ago (Turonium) and was at an extremely low spread rate of 3 millimeters / year. When exactly the Valais Ocean was closed again is still uncertain, possibly already towards the end of the Upper Cretaceous, but at the latest in the Palaeogene .

Around 135 million years ago ( Valanginium ) the pile of nappes, which had already begun in the Jura, was tectonically overprinted and changed several times in the course of the Lower Cretaceous during the closure of the Alpine Tethys . This development phase, which lasts up to about 100 million years, is known as the Eoalpine phase .

The orogenic movements in the Lower Cretaceous, in turn, had been accompanied by the subduction of large quantities of crustal material under the western end of the Meliata indentation. This created an eclogitic subduction zone around 95 million years ago , which was later exhumed again. The Eoalpine phase is now documented in the Rossfeld Formation (Valanginium to Aptium) through the entry of ultrabasic detritus .

Plate reconstruction for the Maastrichtian 70 million years ago

The final subduction of the Alpine Tethys began around 90 million years ago in the Turonian . Between 80 and 67 million years, however, the subduction shifted to the northwest (so-called roll-back ), which greatly stretched the Austroalpine nappes. The stretching was compensated by shearing off to the east and south-east and partly by shallow detachments. In the Austroalpine area, right-handed, east to east-south-east trending leaf shifts were established around 70 million years ago, which in the central and southern Alps turned into a mutual sense of movement. The syntectonic Gosau sediments were now settling in piggyback basins on the back of the pile of blankets, which moved further north, and which even took on a deep marine character towards the end of the Upper Cretaceous. The Gosau remained in the western section up to the Cretaceous / Tertiary border.

In the Paleocene and Eocene two subduction zones probably should have been present. One lay south of the Valais Ocean and continued across the Pyrenees into the Bay of Biscay. The other was on the southeastern edge of the Piedmont-Liguria Ocean and stretched as far as Corsica . At the beginning of the bartonian 40 million years ago the last oceanic remnants were swallowed, nevertheless the subduction movements continued afterwards, so that the thrusts now progressed in the continental area.

At the end of the thrust processes in the late Eocene 35 million years ago, the Northern Limestone Alps were thrust on their northern edge onto the Randcenoman, the Flysch Zone and the Helvetic, but in some places also onto the Subalpine Molasse. The paleogenic movements (65 to 23 million years ago) comprise the actual main Alpine phase (35 to 23 million years ago - Priabonian to Aquitanium ). It was accompanied by a very strong northward movement of the Adriatic plate, which is estimated to be 600 kilometers.

During the Neogene (from 23 million years ago) the orogen collapsed, which resulted from the Miocene on the Vienna Basin on the eastern edge of the Northern Limestone Alps or the inner-Alpine Inntal Basin south of Kufstein. These intrusion basins (so-called pull-apart basins ) are to be assessed as the result of the neogene stretching of the Eastern Alps by more than 50 percent. This was accompanied by a narrowing in a north-south direction along old west-north-west and north-east trending leaf shifts. The northeast-trending Inntal leaf shift with a sinistral offset of 75 kilometers plays a very important role. Towards the end of the Lower Miocene there was a lateral extrusion of the Eastern Alps to the east - at the same time with a stronger uplift and exhumation of the Tauern Window (the ascent of the Tauern Window had already begun between 40 and 35 million years ago). The central part of the orogen was dominated by expansion tectonics, whereas thrust belts continued to advance towards the Alpine foreland at the edges.

Natural material use

Epitaph made of Adnet marble in the Munich Frauenkirche

Natural stones

In the northern Limestone Alps, decorative stones, some of which are very valuable, are extracted for architecture and applied arts:

Natural resources

When it comes to minerals in the Northern Limestone Alps, it is mainly calcite  (CaCO 3 ) in various variations that occurs, more rarely different mineral phases or mineralizations . Fluorite (fluorspar, CaF 2 ), galena  (PbS) and zinc blende  (ZnS) were and are mined in the Northern Limestone Alps. Compared to the Grauwackenzone , which is particularly rich in raw materials and has historical copper deposits , the Northern Limestone Alps are poor in natural resources.

The salt deposits within the Northern Limestone Alps were and still are of great importance. These were probably mined in the Hasel Mountains for 10,000 years (and certainly then by the Celts ). The centers of salt mining in Germany are Bad Reichenhall and Berchtesgaden , in Austria above all the salt mines of the Salzkammergut such as Altaussee , Bad Ischl and Hallstatt and Bad Dürrnberg near Salzburg. Many place names testify to the presence of salt, such as Salzburg, Hall in Tirol or Hallein .

See also

Web links

literature

  • R. Bousquet et al: Metamorphic framework of the Alps, 1: 1000000 . Commission for the Geological Map of the World (CCGM / CGMW), Paris 2012.
  • HW Flügel and Peter Faupl: Geodynamics of the Alps . Deuticke, Vienna 1987.
  • MR Handy ua: Reconciling plate-tectonic reconstructions of Alpine Tethys with the geological-geophysical record of spreading and subduction in the Alps . In: Earth Science Reviews . tape 102 , 2010, p. 121–158 , doi : 10.1016 / j.earscirev.2010.06.002 .
  • H.-G. Linzer et al .: Build-up and dismembering of the eastern Northern Calcareous Alps . In: Tectonophysics . tape 272 , 1997, pp. 97-124 , doi : 10.1016 / S0040-1951 (96) 00254-5 .
  • H. Peresson and K. Decker: The Tertiary dynamics of the northern Eastern Alps (Austria): Changing palaeostresses in a collisional plate boundary . In: Tectonophysics . tape 272 , 1997, pp. 125-157 , doi : 10.1016 / S0040-1951 (96) 00255-7 .
  • AO Pfiffner: Geology of the Alps . Wiley and Sons, Chichester 2014, pp. 368 .
  • Alexander Tollmann: The construction of the northern Limestone Alps . Deuticke, Vienna 1076, p. 449 .
  • Alexander Tollmann: Geology of Austria, Vol. II: Extra-central Alpine portion . Deuticke, Vienna 1985, p. 710 .

Individual evidence

  1. ^ AO Pfiffner: Geology of the Alps . Wiley and Sons, Chichester 2014, pp. 368 .
  2. ↑ a b Representation in Nikolaus Froitzheim: Geology of the Alps Part 1: General and Eastern Alps. Lecture script , in: Rheinische Friedrich-Wilhelms-Universität Bonn: Structural Geology (online, uni-bonn.de, accessed August 10, 2016).
  3. ↑ a b c Clear short description, for example in: Geology of Styria: 1 The share in the Eastern Alps. Association of Styrian Mineral and Fossil Collectors (vstm.at), accessed August 10, 2016.
  4. ↑ Schöcklkalk of the Graz Paleozoic
  5. ^ Triebenstein limestone of the Veitscher ceiling , Central Eastern Alpine overburden
  6. ↑ Leithakalk of the Molasse Zone
  7. ↑ Names like those of the Steirische and Lungauer Kalkspitze show the exceptional phenomenon in an otherwise different area.
  8. ↑ Main and Wetterstein dolomite in the Radstadt ceiling - this area is one of the geologically most interesting in the Alps, almost all systems and zones of the Eastern Alps are represented here.
  9. ↑ Kainacher Gosau
  10. ↑ O. Krische and H.-J. Gawlick: Age and significance of Lower Cretaceous mass flows: Ischl Breccia revisited (Rossfeld Formation, Northern Calcareous Alps, Austria) . In: Austrian Journal of Earth Sciences . tape 108 (2) , 2015, pp. 128–150 , doi : 10.17738 / ajes.2015.0017 .
  11. ^ V. Trommsdorff et al .: Mid-Cretaceous, primitive alkaline magmatism in the Northern Calcareous Alps: Significance for Austroalpine Geodynamics . In: Geologische Rundschau . tape 79/1 , 1990, pp. 85-97 .
  12. ↑ GH Eisbacher, H.-G. Linzer, L. Meier and R. Polinski: A depth-extrapolated structural transect across the Northern Calcareous Alps of western Tirol . In: Eclogae geol. Helv. Band 83 , 1990, pp. 711-725 .
  13. ↑ JET Chanell, R. Brandner, A. Players and JS Stoner: Paleomagnetism and paleogeography of the Northern Calcareous Alps (Austria) . In: Tectonics . tape 11 , 1992, pp. 792-810 , doi : 10.1029 / 91TC03089 .
  14. ↑ a b Hans-Gert Linzer, Lothar Ratschbacher and Wolfgang Frisch: Transpressional collision structures in the upper crust: the fold-thrust belt of the Northern Calcareous Alps . In: Tectonophysics . tape 242 , 1995, pp. 41-61 .
  15. ↑ Pablo Granado, Eduard Roca, Philipp Strauss, Klaus Pelz and Josep Anton Muñoz: Structural styles in fold-and-thrust belts involving early salt structures: The Northern Calcareous Alps (Austria) . In: Geology . 2018, doi : 10.1130 / G45281.1 .
  16. ↑ Gerhard. W. Mandl, Rainer Brandner and Alfred Gruber: To delimit and define the limestone alpine ceiling systems (Eastern Alps, Austria) . 2017.
  17. ↑ N. Froitzheim, D. Plasienka and R. Schuster: Alpine tectonics of the Alps and Western Carpathians . In: T. McCann (Ed.): The geology of Central Europe . Geological Society, London 2008, p. 1141-1232 .
  18. ↑ M. Kralick, H. Krumm and JM Schramm: Low Grade and Very Low Grade Metamorphism in the Northern Calcareous Alps and in the Greywacke Zone. Illite-Crystallinity Datas and Isotopic Ages . In: H. Flügel and P. Faupl (eds.): Geodynamics of the Eastern Alps . Deuticke, Vienna 1987, p. 164-178 .
  19. ↑ a b M. R. Handy et al .: Reconciling plate-tectonic reconstructions of Alpine Tethys with the geological-geophysical record of spreading and subduction in the Alps . In: Earth Science Reviews . tape 102 , 2010, p. 121–158 , doi : 10.1016 / j.earscirev.2010.06.002 .
  20. ↑ HJ Gawlick, L. and R. Lein Krystin: Conodont color alteration indices: Palaeotemperatures and metamorphism in the Northern Calcareous Alps - a general view . In: Geologische Rundschau . tape 83 . Berlin 1994, p. 660-664 .
  21. ↑ H.-J. Gawlick and N. Höpfer: The middle to early Upper Jurassic high pressure metamorphosis of the Hallstatt Limestone (Triassic) of the Pailwand: a key to understanding the early history of the Northern Limestone Alps . In: Font no. German Geol. Ges. Band 1 , 1996, p. 30-32 .
  22. ^ WC Pitman and M. Talwani: Sea floor spreading in the North Atlantic . In: Geol. Soc. Amer. Bull. Band 83 , 1972, p. 619 .
  23. ^ JF Dewey, WC Pitman, WBF Ryan and J. Bonnin: Plate tectonics and the evolution of the Alpine system . In: Geol. Soc. Amer. Bull . tape 84 , 1973, pp. 31-37 .
  24. ↑ SM Schmid, B. Fügenschuh, E. Kissling and R. Schuster, R .: Tectonic map and overall architecture of the Alpine orogen . In: Eclogae geologicae Helvetiae . tape 97 , 2004, p. 93-117 .
  25. ^ H. Kozur: The evolution of the Meliata-Hallstatt ocean and its significance for the early evolution of the Eastern Alps and the Western Carpathians . In: Palaeogeography, Palaeoclimatology, Palaeoecology . tape 87 , 1991, pp. 109-135 , doi : 10.1016 / 0031-0182 (91) 90132-B .
  26. ↑ P. Strauss, M. König and R. Sauer: Middle Triassic Olistholith in Upper Jurassic layer sequence, Tirolikum, Vienna Basin . In: R. Schuster and T. Ilickovic (Eds.): Working Conference 2015 of the Federal Geological Institute . Federal Geological Institute, Vienna 2015.
  27. ↑ Stampfli u. a .: Western Alps geological constraints on western Tethyan reconstructions. 2002 (PDF, 3.63 MB, from unil.ch, accessed December 12, 2007).
  28. ↑ K. Stüwe and R. Schuster: Initiation of subduction in the Alps: continent or ocean? In: Geology . tape 38 , 2010, p. 175-178 , doi : 10.1130 / G30528.1 .
  29. ↑ H.-J. Gawlick et al: Ophiolitic detritus in Kimmeridgian resedimented limestones and its provenance from an eroded obducted ophiolitic nappe stack south of the Northern Calcareous Alps (Austria) . In: Geologica Carpathica . tape 66 , 2015, p. 473-487 , doi : 10.1515 / geoca-2015-0039 .
  30. ^ C. Leitner and C. Spötl: The Eastern Alps: Multistage Development of Extremely Deformed Evaporites . In: Permo-Triassic Salt Provinces of Europe, North Africa and the Atlantic Margins . 2017, doi : 10.1016 / B978-0-12-809417-4.00022-7 .
  31. ↑ U. Schaltegger et al.: Transition from a rifted continental margin to a slow spreading system: fi eld and isotopic constraints from a Tethyan ophiolite . In: Terra Nova . tape 14 , 2002, p. 156-162 .
  32. ↑ P. Faupl and M. Wagreich: Late Jurassic to Eocene paleogeography and geodynamic evolution of the Eastern Alps . In: Communications Austrian Geological Society . tape 92 , 2000, pp. 70-94 .
  33. ↑ N. Froitzheim, P. Conti and M. van Daalen: Late Cretaceous, synorogenic, low-angle normal faulting along the Schlinig fault (Switzerland, Italy, Austria) and its significance for the tectonics of the Eastern Alps . In: Tectonophysics . tape 280 , 1997, pp. 267-293 .
  34. ^ W. Frisch, J. Kuhlemann, I. Dunkl and A. Brügel: Palinspastic reconstruction and topographic evolution of the Eastern Alps during Late Tertiary tectonic extrusion . In: Tectonophysics . tape 297 , 1998, pp. 1-15 .
  35. ^ H. Reschreiter and K. Kowarik: The prehistoric salt mines of Hallstatt . In: T. Stöllner and K. Oeggl (Eds.): Bergauf Bergab. 10,000 years of mining in the Eastern Alps . VML Verlag Marie Leidorf, Bochum 2015, p. 289-296 .