Urbrenz
As Urbrenz refers to a prehistoric river system of the Danube flowing not. It existed in the area of the upper rivers of Rems , Kocher and Jagst , which today flow in the opposite direction to the Neckar .
State of research
The existence of a large Urbrenz or several large wild rivers north of the Swabian Alb is considered to be proven due to the relatively undisturbed occurrence of fluvial Goldshöfer sands in numerous localities - mainly in the eastern Swabian-Franconian forest mountains , on the Frickenhofer Höhe and near Aalen . The remains of Goldshöfer sands deposited from today's Keuperrand step upwards were transported and deposited by the ancient Pleistocene tributaries of the Urbrenz that drained to the Danube. The typical material properties of the sands attracted large-scale opencast mining, which is still taking place today. In order to keep a geo-archive accessible, a large forest and meadow area and several extensive natural monuments were placed under legal protection in 2001. The name Goldshöfer Sande refers to the type locality Goldshöfe ⊙ , the most important and largest contiguous valley backfilling of the Urbrenz before the breakthrough through the Aalen gate of the Albtrauf. Deposits up to 20 m thick can be reached here. The same or similar deposits of sand and rubble from the “ Rhenish ” rivers Jagst and Kocher and their tributaries are no longer listed under this category of names .
In the meantime, Keuper-Feuerstein finds have also proven that Urbrenz feeders began far away in the Hohenlohe and western Swabian-Franconian forest mountains.
A reference on the upper surface of the high-Jura Schwäbischen Alb ( "Ochsenberg gravel" ⊙ , about 100 m above Königsbronn ) even has a feeder Tertiary Urbrenz.
Delimitation of the Danubian and Rhenish rivers
Ur-Kocher and Ur-Jagst advanced from the Rhine and Neckar by means of retrograde erosion . They eroded their catchment areas and relocated part of the older Keuperrand step , i.e. the layer step of the Keuper in the south-west German layer step country , which in the Tertiary was about 10 million years ago on the line Künzelsau - Weikersheim , to the south. The Rhenish rivers attracted more and more areas of the river system that previously drained to the Danube . They finally broke through the Pleistocene Keuperrand and immediately attacked the Danubian Urbrenz tributary, which was broad and sluggishly flowing with a very slight gradient.
On both sides of the Rhenish rivers Kocher and Jagst, which are deeply dug into the flat landscape and flow to the north, some river terraces have been preserved (sand and gravel terraces ). Numerous height determinations of river terraces along the Jagst resulted in a gradient of only 5 m for the part of the Danubian hillside terraces over a distance of approx. 20 km, whereas the main terraces formed by the Rhenish Jagst and its predecessors showed a gradient of 27 m.
Danubian tributaries: river history of a Pleistocene primeval fire
The Goldshöfer Sands
"As Goldshöfer sands" - naming follows the name of the hamlet Goldshöfe where the type locality is located 2.5 km east of Hüttlingen - "are those of sand and gravel remains in the catchment area of Kocher and Jagst called that, now mostly in inverted relief on lying on the heights, document an oldest Pleistocene water network, the veins of which flowed radially towards the Albpforte near Aalen and flowed through the Alb to the Danube. ”(Zeese 1972), p. 48. The Goldshöfer sands are a weathering and erosion product of the Danubian tributaries, which due to the narrowing from a few km to a few hundred meters and due to the massive reduction in their remaining Danubian drainage areas . Originally, only the terrace sands lying in the narrow Kastental valley of the Albtrauf breakthrough were unequivocally regarded as evidence of a Danubian drainage system reaching into Hohenlohe . When, in 1959, a borehole sank at the Seegartenhof (between the sources of the Schwarzer Kocher and Brenzpopf ) it was verified that the erosion floor was ≥ 456.5 m above sea level. If NN is much lower than previously assumed, the sands and boulders up to the edge of the Keuperrand step could be conclusively assigned to an Urbrenz. The feeders flowed onto the Alb with a slight, but still just sufficient, gradient (0.25 ‰) because the rock support surface in the north was sufficiently higher.
All sands and gravels , which are quite similar in nature , but whose heights follow the Rhenish rivers Kocher and Jagst, are considered to have only been relocated again and no longer belong to the Goldshöfer Sands. (Compare here on the graphic the markings Goldshöfer Sande and the blue arrows). More Goldshöfer Sande, z. B. to Adelmannsfelden , lie on hilltops up to 492 m above sea level. NN . At these heights one assumes a terracing of the accumulation bodies.
Texture of the Goldshöfer sands
The Goldshöfer sands, which mainly originate from Keuper layers and have been relocated several times, appear today as an occurrence of decalcified, yellowish to rust-brown, not solidified, often medium, but also coarse and fine-grained sands in parts (see grain size classifications ). At times, larger rock pockets, rather at the bottom but small powerful rubble layers, usually with poorly rounded or square-platy pebbles observed and limonitic iron enrichments (iron rinds). "The boulders range covers Jurassic - flints , Brown - and Black Jura - sandstones , chalcedony , silicified Keuper sandstone Keuper crystals and -Feuersteine and cobbles from the Stubensandstein . In addition to fine sandy bands and lenses of silt , which are only a few cm thick, there are occasionally some dm to 1 m thick clay and silt horizons, which are interpreted as high tide deposits and paleo-soil formations ”.
The sediments show the structures of a kilometer-wide, widely branched pigtail river system with shallow gullies and bars that were constantly being rebuilt. An oblique stratification can often be observed in the vertical structure, indicating a south and south-east flow direction. The appearance of cryoturbation ( ice wedges , choke floors, etc.) suggest that the ice and cold ages , which were frequent in the Pleistocene, repeatedly caused thawing and freezing processes.
The sand deposits in front of the Albpforte (in the “Bürgle” north of Aalen) are 40 m above today's Kocher. Here they are up to 20 m thick, elsewhere they are between 6 and 10 m thick.
Timing: Goldshöfer Sande, Rhenish tap
"In the former sand pits east of Aalen [...] remnants of a mammalian fauna that was not exactly rich, but rare because of its old age, were found, which allow a rough paleontological dating". (Adam 1953) assessed and documented the most important find of a complete lower jaw of the southern elephant Elephas meridionalis NESTI . The finds of the Goldshöfer sands of the lower Aalen terrace "are to be classified in the time before the third to last Ice Age, after Adam [...] in the lower Mosbachian or the" older steppe period "." The finds of two halves of the antler of the broad-fronted elk '' Alces latifrons '' and two lower jaw branches of the zebra-like '' Equus süßenbornensis '' are also of great importance. “Absolute age dating was never carried out in the sands”, sampling with the now established method of cosmogenic nuclides failed on the sample material from the borehole.
The retreating erosion of the Rhenish rivers Kocher and Jagst showed, according to the available ages, that the Aalen river tapping and thus the end of the Danubian erosion of the Zopfstrom river system took place around 700–600 ka ago.
Pleistocene Keuper flint stones
Of particular importance for the further determination of the extent of the Urbrenz feeder in the west and north of the then and now Keuperrand step are two Keuper-Feuerstein finds, namely in today's Keuperbergland
- The Keuper -Feuersteine on the Flinsberg in the Mainhardt Forest ( 353 m above sea level , 2.3 km north-west of Oberrot , the outlying mountain created by the reversal of relief lies in the tectonic rift "Neckar-Jagst-Furche"). On the Flinsberg there are some meter-large blocks of flint.
- The Keuper fire stones in the Fichtenberger red that flows into the stove .
as well as outside
- The finds of Keuper fire stones in the Ziegeleigrube S of Reubach (469– 465 m above sea level ) on the high “Schrozberger Schild”. These Keuper fire stones are multiple rearrangements on the Hohenloher plain, which is now completely free of keuper after erosion .
Nature and occurrence of the Keuper fire stones
Keuper fire stones occur en masse on the sandstone plateaus of the Oberkeuper in the Swabian-Franconian Forest Mountains , the marl marl and in the parlor sandstone.
The Hohenlohe flint stones are often collected because of their differentiated colors or made into pieces of jewelry because they have a "beautiful" color spectrum. The material is predominantly chalcedony , a fibrous, microcrystalline structure variety of the mineral quartz. They are hard, splintery, silicified (SiO 2 -containing) pebbles. They are usually only rounded and have a diameter of up to 5 cm. Due to their hardness (7 on Moh's hardness scale 1–10), they are only marginally present after long fluvial transport , but above average they are present and therefore easy to identify.
In the Fichtenberger Rot and Kocher area, i.e. in the Mainhardt Forest and in the central Swabian-Franconian forest mountains, the layers of marl and parlor sandstone are still in full swing. The most important occurrences of Keuperfeuerstein are around the Flinsberg. In the Ice Ages of the Pleistocene, small flint stones from the Flinsberg got through solifluction into the erosion zones of the Danubian Fichtenberger Rot, then into a Danubian cooker and finally into Goldshöfer Sande and even into terraces on the Swabian Alb.
Simon writes in (Schüßler et al. 1999), p. 56 about the research in the Reubacher pit, which is on the now completely keuper-free Hohenlohe plain and even north of the Pleistocene Keuperrandstufe: “The measurement of the storage of flat boulders enables to determine the former transport directions of the ballast. These are directed to the southeast, southwest and north-northwest. The second direction represents the direction of flow of the step edge river , […] “, which flowed along the Pleistocene Keup step edge , broke through it and transported flints in the erosion material of a Danubian tributary further south to the Alb eaves.
According to (Reiff & Simon 1990) are Keuper fire stones
- large areas in "scattered rubble cover" on both sides of the middle and lower Fichtenberger Rot and the cooker from Schwäbisch Hall and
- in the Reubach mine and extensively in "flint corridors" on the eastern Hohenlohe plain
proven.
The evidence that the sedimentation of Keuper fire stones took place in several cycles has also shown that the catchment area of the Danubian feeder must have been extended far beyond the finds in the Goldshöfer Sands.
Economic utilization of the Goldshöfer sands as a raw material
The Goldshöfer sands were used in the Wasseralfinger (Aalener Teilort) ironworks as molding sands or were and are still used today - as far as this is economical - as a sought-after building material (NSG 1.245 2001). “The degree of preparation is decisive for use : The Goldshöfer sands are z. B. unwashed as cable and bricklaying sand, washed used as an aggregate for plaster and concrete. "(LGRB 2006) p. 24.
Protection of the current landscape as a geographic archive of the Goldshöfer Sands
The lively, economically profitable opencast mining in Goldshöfer sand pits and the enormous pressure of the towns to settle with the overbuilding of large areas endangered the at least minimal preservation and accessibility of the irreplaceable landscape above the sand sediments. After several years of debate, this ultimately led to areas being placed under legal protection.
2001, a Brown Jura mountain range between Aalen-Hofen and Huettlingen in Ostalbkreis , a 46.5-hectare forest and meadow area as natural space subunit " 102.11 Goldshöfer patio stones ," as well as several area natural monuments under legal nature (provided Coll . Of 23 February 2001, p. 130). Under the layers of earth of the nature reserve on both sides of the Kocher is the largest contiguous valley backfilling of the type locality Goldshöfer Sande (NSG 1.245 2001).
Examples of sand pits with Goldshöfer sands
As geotopes are u. a. recorded, but not legally protected (only "worthy of protection"):
- An abandoned sand pit east of Onatsfeld (district of Aalen). Limonitic iron accumulations are baked in the gravel and sand layers . "In addition to inclined stratification structures and cryogenic (cold-time) curvature of the strata, incisions in small erosion channels can also be observed." (LGRB 2005), p. 180.
- Opened sand pits near Buch ( Rainau- Schwabsberg), at about 470 m above sea level. NN . Between Buch and Schwabsberg in the Jagst Valley, south of Ellwangen , several sand pits have been abandoned and filled or recultivated . The direction of the pouring corresponds to the Urbrenzlauf. (LGRB, 2005)
- The sand pit of the company Fuchs, W von Dietrichsweiler (between Jagstzell and Ellwangen), at about 470 m above sea level. NN , in operation since 1996, lying discordantly on the lower Stubensandstein in Mittelkeuper. The thickness is 7–9 m, towards the edge 5–6 m. The sediments are divided by a silt / clay horizon up to 0.4 m thick, which shows interesting cryoturbation phenomena. "The sands are whitish, white-gray, yellowish-brown and rust-brown in layers, where they are also solidified by increased iron and manganese concentrations." The lower layers are layered clearly at an angle. (LGRB, 2005), p. 239f
- Sand pit south of Dietrichsweiler. In this sand pit, post-sedimentary fold structures and pocket-like curvatures of the layer as a result of sunken clay lumps are particularly noticeable. (LGRB, 2005)
Urbrenz feeder since the Old Tertiary
The Danubian river system existed long before the Pleistocene. This is proven by the higher lying fluvial sediments near Hinterwald (municipality of Bühlerzell ) and on the Swabian Alb, for example near Ochsenberg (municipality of Königsbronn, around 610 m above sea level ). This river system also drained parts of Osthohenlohe. However, equivalent deposits of this age are no longer available in Hohenlohe (Schüßler 1999) p. 63.
Individual evidence
- ↑ Keuper flint stones were transported from an area of Hohenlohe (" Schrozberger Schild") and from the catchment area of the Fichtenberger Rot (western Swabian-Franconian forest mountains) in the Pliocene / Pleistocene to the Aalen Albtrauf and the Swabian Alb.
- ↑ Schüßler et al. 1999, p. 19.
- ↑ 25 observations of old river terraces of today's Jagst from Schwabsberg ( 457 m above sea level ) to Jagstzell (place at 414 m above sea level , Jagst terrace “lower sand” at 430 m above sea level , Danubian terrace “upper sand” at 462 m above NN ), (Wagner 1952), illustration "Sand terraces of the Keuperjagst in longitudinal section", p. 143.
- ↑ A flat, barely recognizable valley watershed separates the valley from Kocher (flowing north) and Brenz (flowing to the Danube). The sources of the two rivers are only 4.1 km apart between Königsbronn and Oberkochen . The watershed was created when the erosion force of the Urbrenz had become less than the uplift of the Swabian Alb.
- ↑ "In the Brenzeinschnitt itself the rock bed was under a valley filling up to 50 m thick at the" Seegartenhof "NW Königsbronn at 456.5 m above sea level. NN (probably not at the lowest point) and in the "Seewiesen" near Heidenheim at 451.5 m above sea level. NN erbohrt. "(Etzold 1994), p. 126.
- ↑ (Zeese 1972) p. 66, (Etzold 1994), p. 127
- ↑ (LGRB 2006), p. 23
- ↑ (Etzold 1994), p. 135
- ↑ (Etzold 1994), p. 136
- ↑ (Etzold 1994), p. 135ff
- ↑ (Strasser 2009), p. 47 and p. 57f
- ↑ (Strasser 2009), p. 35 after (Hagdorn & Simon 1985), (Etzold 1994)
- ↑ (Schüßler et al. 1999)
- ↑ Keuper fire stones can also be found on the remains of shell limestone and Keuper of the Hohenlohe plain, in river terraces and valleys of the Kocher and Jagst rivers and in the Upper Jura of the Swabian Alb . Flint stones also occur in other rock formations in Germany and neighboring countries (Schüßler et al. 1999).
- ↑ (Schüßler et al. 1999). The “all- round substance” SiO2 is sometimes represented by over 90% in Keupersandstone and Buntsandstein
literature
- (Wagner 1952), Wagner, R., The Keuper in the upper Jagst area and the Goldshöfer Sande , Diss. Uni Tübingen, Tübingen 1952
- (Adam 1953), Adam, KD, Elephas meridionalis NESTI from the old Pleistocene sands near Aalen (Württemberg) , Ice Age and Present (E&G, Quaternary Science Journal), 3, Deutsche Quartärvereinigung eV, Öhringen 1953
- (Zeese 1972), Zeese, R., The valley development vin Kocher and Jagst in the Keuperbergland - river history as a contribution to the interpretation of the layer level morphogenesis , Diss. Uni Tübingen, Tübingen 1972
- (Zeese 1975), Zeese, R., The Goldshöfer Sands and the Quaternary Relief Generations in the Alb foreland of Eastern Württemberg , Ice Age and the Present, (E&G Quaternary Science Journal) 26, Öhringen 1975
- (Hagdorn & Simon 1985), Hagdorn, H., Simon, T., Geology and Landscape of the Hohenloher Land , Sigmaringen 1985
- (Hagdorn 1988), Hagdorn, H. (Hrgb), New Research on the Geological History of Crailsheim , Stuttgart, Korb 1988
- (Geyer & Gwinner 1989), Geyer, OF, Gwinner, MP, Geologie von Baden-Württemberg , 3rd edition, Stuttgart 1986
- (Reiff & Simon 1990), Reiff, W., Simon, T., The history of the river Urbrenz and its main source rivers (excursion L on April 21, 1990, in: (Jber. Mitt ...), NF 72, 1990
- (Etzold 1994), Etzold, A., Geological Map 1: 25000 von Baden-Württemberg ', Explanatory Notes on Sheet 7126 Aalen , 2nd improved edition, Landesvermessungsamt Baden-Württemberg, Stuttgart 1994
- (Simon 1996), Simon, T., The gravel from Reubach in the east of Hohenlohe - in: (Jber. Mitt ...), NF 78, 1996
- (Schüßler et al. 1999), Schüßler, H., Simon, T., Warth, M., Origin, beauty and riddle of the Hohenloher Feuersteine , Bergreute 1999
- (NSG 1.245, 2001), nature reserve Goldshöfer Sande, text of the appreciation, October 20, 1998, www2.lubw.baden-wuerttemberg.de/public/abt2/dokablage/oac_12/wuerdigung/1/1245.htm
- (LGRB 2005), Huth, T & Lunker, B., Geotourist map of Baden-Württemberg 1: 200000 - North, explanations , Freiburg 2005
- (Simon 2005), Simon, T., River and landscape history in the Taubertal and Osthohenlohe (excursion G on April 1, 2005) , in: (Jber. Mitt ...) NF 87, 2005
- (LGRB 2006) Information 18, Raw Materials Report 2006; State Office for Geology, Raw Materials and Mining, Freiburg
- (Eberle et al. 2007), Eberle, J., Eitel, B., Blümel, D., Wittmann, P .; The south of Germany from the Middle Ages to the present , Heidelberg 2007
- (Rosendahl etal 2008), Rosendahl, W., Junker, B., Megerle, A. Vogt, J., (Eds.), Walks in die Erdgeschichte , 18, Swabian Alb, 2nd edition, Munich 2008
- (Simon 2008), Simon, T., Excursion 6: Mining, river and landscape history in Aalen and the surrounding area , in: Rosendahl etal 2008)
- (Strasser 2009), Strasser, A., Reconstruction of former Danubian landscapes and Rhenish erosion over a period of one million years - a modeling and calculation using the example of two southern German river systems , Diss.University Stuttgart, Stuttgart 2009
- (Strasser etal 2010), Strasser, A., Strasser, M., Seyfried, H., Quantifying erosion over timescales of one million years: A photogrammetric approach on the amount of Rhenish erosion in southwestern Germany , in: Geomorphology 122, 2010
- (Geyer Gwinner 2011), Geyer, OF, Gwinner, MP, Geologie von Baden-Württemberg , 5th completely revised edition, Geyer, M. Nitsch, E., Simon, T. (Ed.), Stuttgart 2011
- (Jber. Mitt ...), Jber. Mitt. Oberrhein. geol. Ver. Annual reports and communications from the Upper Rhine Geological Association, New Series , Stuttgart
Web links
- LGRB map for individual geotope texts
- Goldshöfer Sande nature reserve, text of the appreciation, October 20, 1998
- Map of the Ur-Brenz drainage area near the Alb , with the Goldshöfes roughly in the middle of the map, on: State Agency for the Environment Baden-Württemberg (LUBW) ( information )
Map with all coordinates: 