Urlauchert

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The term Urlauchert describes several geological conditions in the prehistory of the Lauchert landscape and river system . Today the Lauchert is a small river on the Middle Swabian Alb . After long processes of weathering, massive erosion, sedimentation , tectonic movements and the first karstification, the river landscapes and land surfaces of a primeval valley are almost lost.

Rare geo-archives

Only for the last 5.3 million years (Ma), that is, for the Pliocene and the subsequent Quaternary, there are sufficient geo-archives with the help of which a relatively complete representation of this part of the Lauchert river history is possible. The early history of the river has to be reconstructed from a few relics that can still be interpreted. The geology assumes that a Urlauchert a great few south-facing drainage strands of southwestern Germany was. Today the Lauchert is only a very small river that is threatened by geological and hydrogeological phenomena in its (above-ground) existence.

Eocene and Oligocene (≈ 65 to 24 Ma)

Geological section through the Hegau

The prerequisites for the emergence of a Urlauchert were created in the Cenozoic epochs (Earth New Age: Tertiary and Quaternary) through the formation of the Upper Rhine Rift (≈50Ma) and the Alps ( Alpine orogeny and foreland depression of the Molasse basin , ≈30Ma). This created the two large basin landscapes that shape the geology of southwest Germany . In the Molasse Basin, sea invasions and silting phases alternated several times. There are therefore both marine deposits (lower sea molasses, UMM; upper sea molasses, OMM) and freshwater sediments (lower fresh water molasses, USM; upper fresh water molasses, OMM).

On the northern edge of the Molasse Basin, especially in Hegau , the marginal facies , fluvial limestone pebbles , dating back to the processing of the White Jura of the Swabian Alb, mesh with the basin facies of the USM. These debris-carrying sediments, which drained far beyond the Neckar, were subsequently “ cemented ” with a calcareous binding agent and are now known as the “Older Jura- Nagelfluh ”.

Miocene (≈24 to 5.3 Ma) traces of ancient river systems

At least up to the beginning of the Upper Miocene , southwest Germany was still an extreme bas-relief (100-250m above sea level, today: 560m-1000m). The Alb eaves as the northern edge of the tectonically raised Jura strata and the south-west German stratiform land were not yet developed. The layers of the Jura reached far beyond today's Albtrauf to the north.

Large rivers meandering in wide, shallow gullies , drained far beyond what is now the Neckar region with a slight gradient . The Jura panel was barely broken. The Urlauchert probably developed in this Miocene milieu.

After the last receding of the shallow sea from the Molasse basin (≈ 20Ma), the so-called “ Graupensandrinne ”, documented as a geo-archive, developed in the northern part , which still drained from east to west into western Switzerland. After the backfilling at the end of molasses sedimentation (≈ 11-10Ma) the gradually developed ancient Danube and formed, for example 8mA to an almost completely southwestern Germany and Switzerland comprehensive flow system (the still small flow system of Oberrheingraben excluded). The Urlauchert is very likely to have flowed into both drainage lines, Graupensandrinne and Urdonau.

In a second major tectonic phase from the Upper Miocene onwards, the Jura panel rose and tilted towards SE. In this geological period the Upper Rhine Rift deepened and a primeval Rhine developed in it , the catchment area of ​​which was initially still small. However, the new, deeper erosion base constantly attacked the S-directed drainage system of the Juratafel due to more powerful, retrograde erosion of the Rhine tributaries . That changed the situation in southwest Germany fundamentally. The rapidly growing Rhine made z. B. a mighty Urlone flowing to the south tributary, that is, it reversed the direction of flow in front of the Juratafel! The Urlone was finally beheaded on the Albtrauf near Geislingen an der Steige ( Strunkpass ). Today the Lone is an extremely karstified , sometimes dry , small stream that rises in the Middle Swabian Alb in Lonsee .

Younger Jura-Nagelfluh on both sides of the Lauchert . In Lauchertgraben also discarded

Remaining areas of fluvial gravel strands on both sides of the great Urlauchert and Urlone rivers have been preserved and documented as the “Younger Jura-Nagelfluh”. W and E of the Lauchert near Veringendorf (Veringenstadt) is occupied at 5 places Jüngere Jura-Nagelfluh, 9km E from the Lauchert also on larger areas around Inneringen (Hettingen) and Emerfeld (Langenenslingen) .

After the barley sand channel had been filled in and the molasses sedimentation ended, the lower reaches of the large rivers coming from the north were sealed by huge masses of debris (mainly OSM from the S). Due to massive erosion in the further course from the Upper Miocene to the Lower Pliocene, the tertiary OSM and also Jurassic layers were cleared again to varying degrees. Today only a few remnants of tertiary ceilings remain on the southern Albrand. The first deepening began.

In the Upper Miocene and far into the Middle Pliocene (≈3.5 Ma) were the primary rivers that drained southwest Germany from the north: Feldberg-Danube , Brigach and Breg , Urprim (Prim) , Urschmeie (Schmeie) , Urlauchert, Urlauter (Louder) , Urlone (Lone) , Urbrenz (Brenz) .

Upper Miocene (from ≈11 Ma): traces of a first karstification phase

The development of the river history of Urlauchert and Lauchert can not be separated from the development of karstification and the widening of fissures and caves . In the new survey (2005/6) a series of overgrown today Bohnerzgruben Burghaldenstrasse, a witness mountain on the Middle Swabian Alb south of Salmendingen cave typical sediments were stalagmites and Wandversinterungen found. Stimulated by these findings, numerous (large) mammal - fauna remains that had been collected and preserved during the time of the last mine ore excavations around 1900, were again paleontologically classified. The taxa could be assigned to fauna species that were widespread here between the Lower and Upper Miocene. Time overlaps in the “ MN 9 ” (“European Land Mammal Mega-Zone”) allow the pit surfaces and the rows of the ore pits to be interpreted as cave ruins of a “post-Upper Miocene relief” (ie as predanubic). In the Swabian Alb, for the first time, there was evidence of a karstification phase that can be related to the Miocene Urlauchert.

Wide valley of a Urlauchert ? Oberste Lauchert, very small, often dried out
West-east longitudinal profile from Rottenburg am Neckar to Mägerkingen ; Evidence for formerly large Alb rivers.

The valley basin of the Oberste Lauchert, which is up to 1.5 km wide, from the Albtrauf to the mouth of the Erpf where the small Lauchert trickle is just up to three meters wide is striking . It can be assumed that this is the valley of a Urlauchert of "River Level IV", which today stretches out in the air at the Albtrauf in a north-west direction - was "beheaded", that is, the valley forms a trunk pass . The phenomenon Strunkpass is empirically proven in the literature on the Swabian Alb for the Fehla , who was beheaded by the Rhenish Starzel west of Burladingen . Obviously there was an Urfehla higher up and further north. Oldest Pleistocene ( Tegelen ) Neckar terrace gravel near the Starzel estuary is documented. Ufrecht plausibly connects the Urfehla with faunal fossils of the same age in the Karls- and Bärenhöhle . For him, the broad Oberste Laucherttal and the tapping through the Steinlach and the already proven connection between the bear and Karl caves and the Lauchert are obvious.

The northern continuation of a Urlauchert above today's mouth of the Erpf has not yet been adequately scientifically proven (as of 2011). Therefore, the equally uncertain interpretation applies that the morphology , old Erpf river terraces and the Bären- and Karlshöhle as Pliocene geo-archives of an old, not yet dried up Urerpf are the northern continuation of the Lauchert.

Incidentally, the Miocene and Early Pliocene reliefs of the Jura plateau, including the Urlauchert relief, have been completely removed and therefore geologically unreliable to this day.

Individual evidence

  1. ↑ Eberle (2007), p. 39; Erl. GeoK 1: 50000, 1992, Hegau, p. 42ff
  2. ↑ Eberle (2007), p. 44
  3. ↑ In the ≈60Ma (lowest Tertiary ) old volcanic vent of Katzenbuckels , approx. 40km N Heilbronn , the Middle and Lower Jura were found. Eberle (2007), p. 29; Geyer & Gwinner (1986), p. 291
    In the northernmost volcanic vent of the Swabian volcanism (≈ 15 Ma, Middle Miocene), the small outcrop near Scharnhausen - 19 km as the crow flies to today's Albtrauf - Upper Jura is documented. Villinger (2008) p. 14
  4. ↑ Eberle (2007), p. 48
  5. ↑ Eberle (2007), p. 33
  6. ↑ The most important evidence of this is the cliff line of the last Molasse Sea, which runs from 900m in the W to approx. 450m in the E today
  7. ↑ The Urlone, consisting of a "Cannstatter Lone" which reached in the north to around Heilbronn and a "Tübingen Lone" as the forerunner of the Neckar , had drained large parts of southwest Germany into the Molasse basin. The Urfils as a tributary of the Urlone became the tributary of the Neckar, Villinger (2008)
  8. ↑ Most of the karst water of the small Lone gathers in the Donauried . Around 60% of the drinking water obtained by the Baden-Württemberg state water supply in Langenau is karst water, mainly from the Lone.
  9. ↑ According to Schreiner 1965 and Erl. Geokarte 7821, p. 47ff. River sedimentation in the Upper Miocene, facies of the OSM. Ufrecht refers to the findings of Kiderlen (1931) and dates the Jura-Nagelfluh der Urlauchert earlier: "The Jura-Nagelfluh was poured (on the Middle Alb) before or at the latest at the same time as the Lower to Middle Miocene Alb volcanism" (≈15 Ma); For the Urlauchert, Nagelfluh was also found in the chimney of the volcano “Hungersberg-Münsingen”, Ufrecht (2006) p. 53.
  10. ↑ Erl. GeoK 7821, Veringenstadt , 1978, p. 48; Abel (2003a); Geyer & Gwinner (1986), p. 318
  11. ↑ Eberle (2007), p. 61
  12. ↑ the Schmeie is called Schmiecha up to Straßberg (Zollernalbkreis)
  13. ↑ Villinger in Rosendahl (2007), p. 15. Although the Aare of the Aare-Danube was a main strand of the Danube river system up to the Middle Pliocene, it drained Switzerland, not southwest Germany
  14. ↑ Kornbühl , Monk, Aufberg, Käpfle and Burghalde are non-volcanic witness mountains near Salmendingen / Melchingen that are not in front of the Albtrauf
  15. ↑ Ufrecht (2006), p. 50 ff.
  16. ↑ Eberle (2007) p. 46, p. 39.
  17. ↑ Abel (2003a), pp. 87 ff .; Ufrecht (2006), p. 56.
  18. ↑ The receding erosion in the Rhenish river system still contributes to the constant southward shifting of the Alb eaves.
  19. ↑ Ufrecht (2003), Ufrecht (2006) p. 54. Oldest Pleistocene gravel occupy the Neckar near Rottenburg at approx. 415 m above sea level (Rähle & Bibus, 1992); evidence from the Tegelen can also be found in the former river cave Bären- and Karlshöhle, which is now 800m isolated today. The river cave is assigned by Abel (2003a), pp. 87 ff., To a primordial “river level IV”.
  20. ↑ Abel (2003a), p. 68; Scheff (1983)
  21. ↑ Abel (2003a)

literature

Erl. GeoK: Geological map of Baden-Württemberg, 1: 25000, explanations on sheet no, sheet name, year; Hrgb: State Office for Geology, Raw Materials and Mining, Freiburg, (LGRB)

Kiderlen (1931): Kiderlen, Helmut, contributions to the stratigraphy and paleogeography of the southern German tertiary, (Diss., Tü 1930). New yearbook f. Mineralogy, geology, etc. Paläontologie, Beilage-Band, B 66, pp. 215–384, Stuttgart 1931

Schreiner (1965): Schreiner, A., The Juranagelfluh in Hegau. Century geol. L.-Amt, Baden-Württ., 7.

Scheff (1983): Scheff, J. Karstung in the upper Laucherttal - attempt to date age, p. 99ff, Laichinger Höhlenfreund, 18, Laichingen 1983

Geyer & Gwinner (1986): Geyer, OF, Gwinner, MS, Geology of Baden-Württemberg, 3rd edition, Stuttgart 1986

Rähle & Bibus (1992): Rähle, W. & Bibus, E., An old Pleistocene mollusc fauna in the gravel of the Neckar near Rottenburg, Württemberg. Annuals of the Geological State Office Baden-Württemberg, 34, Freiburg 1992, pp. 319–341

Erl.GeoK 1: 50000: Geological map 1: 50000 of Baden-Württemberg, explanations on the Hegau and western Bodensee sheets, Hrgb: State Office for Geology, Raw Materials and Mining (LGRB), Freiburg 1992

Ufrecht (2003): Ufrecht, W., Abel, Th. & Harlacher, Chr., On the plio-Pleistocene development of the bear and Karl caves near Erpfingen (Swabian Alb) taking into account the sintering technology, Laichinger Höhlenfreund, 38, H. 2 / 2003, Laichingen 2003

Abel (2003a): Abel, Th., Investigations into the genesis of the Malmkarst of the Middle Swabian Alb in the Quaternary and later Tertiary (Diss., Tü 2003), TGA, C67, Tübingen 2003

Ufrecht (2006): Ufrecht, W., A sealed cave ruin stage on the Kuppenalb between Fehla and Lauchert (Zollernalbkreis, Swabian Alb), Laichinger Höhlenfreund, Laichingen 2006

Eberle (2007): Eberle, J .; Eitel, B .; Blümel, WD; Wittmann, S., Germany's South from the Middle Ages to the Present, Heidelberg 2007

Villinger (2008): Villinger, E., The Swabian Alb - a geological picture book landscape, in: Rosendahl (2008), pp. 8–23

Rosendahl (2008): Rosendahl, W., et al, Hrgb, Migrations in der Erdgeschichte (18), Schwäbische Alb, 2nd edition, Munich 2008

Commons artwork

Commons : Lauchert  - album with pictures, videos and audio files