Lower terrace of the Upper Rhine

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Sediments from the lower terrace on the embankment of a quarry pond near Rastatt

The lower terrace of the Upper Rhine is a river terrace that consists of large gravel areas covered by high-tide sediments and drifting sands with layers of sand of varying thickness. It stretches in the Upper Rhine Rift, so to speak, from Basel to the Rhine-Main area to the west and east, parallel to the Upper Rhine and its accompanying floodplains with different dimensions and thicknesses of the sediments . This pile of gravel, gravel and sand is an almost flat strip, usually between seven and eight kilometers wide. Relief is created by the debris cone of the flowing waters and the blown drifting sands. The deposits of the Rhine and its upper tributaries are initially predominantly of alpine origin, and are constantly interlinked with the material from the peripheral landscapes brought in by tributaries and streams.

The Pleistocene , würmeiszeitliche landscape structure is the high shore in the Upper Rhine country within the Southwest German escarpment country , in which the Holocene Rhine aue has (Rhein valley) deepened, but which also Pleistocene Kinzig-Murg-Rinne , as other previous and recent waters.

Natural spaces

This lower terrace comprising at German floor the natural spatial units in the range of the Northern (Nature space 22 according to the classification in the manual of the natural spatial structure of Germany (1953-62) / main units: 224 Neckar-Rhein-level , 225 Hessian Rheinebene 223 Hardt levels ), middle (21 / 210 Offenburg Rhine Plain) and southern (20/200 Markgräfler Rheinebene) Upper Rhine Plain (all collectively referred to as D53 according to the modified classification of the Federal Agency for Nature Conservation (BfN) 1994) as well as the Rhine-Main Lowland (23/232 Untermainebene, 237 Ingelheim- Mainzer Rhine Plain) on the right bank of the Rhine. On the Rhineland-Palatinate side is the Vorderpfälzer Tiefland (221), an alternation of loessriedeln , lowlands and alluvial fans of the streams that drain the Palatinate Forest . In contrast to the other bank, dunes are rarer here. There is also loess cover on the eastern section, particularly in the form of alluvial loess washed down.

course

The trench edge clods of the Markgräflerland and the Sundgau quickly narrow the embankments of the Rhine in the south, so that here the high bank, the jump from Niederterrasse to Rheinaue, is up to 15 meters. In Neuenburg am Rhein , for example, the difference in level is between 12 and 14 meters. To the north of Mulhouse , the deposits of the Rhine extend in its low terrace to the lowland of the Ill , until this river cuts through it near Strasbourg and unites with the Rhine. Dreisam , Glotter and Elz make up the majority of the low terrace gravel in the Freiburg Bay area . North of the Kaiserstuhl in the middle Upper Rhine Lowland, the river has only slightly buried itself in the low-lying sediments due to its lower gradient; a clear demarcation is often not possible or only possible with great effort. From the mouth of the Rench further north, the river, originally with little gravel and incline in this area, has shifted the high bank line, which traces the course of its meanders before the Rhine correction, in its loops (as at the Hockenheimer Rheinbogen). Here, on the deposits of the lower terrace, large areas of drifting sand can be found , some of which culminate in dunes up to 25 meters high (such as in the Schwetzinger Sand or in the Iffezheimer Hardt), fine material blown out of the ice age from neighboring areas that have fallen dry and are therefore free of vegetation. These extend from Rheinmünster , interrupted by the inflowing rivers and streams (including Murg , Alb , Saalbach , Leimbach , Neckar , Weschnitz ) down the Rhine as far as Hesse . On the western, the Alsatian and Rhineland-Palatinate side, the lower terrace is mostly covered with alluvial loess from the streams that feed it;

To the “outside”, towards the shoulders of the trench, further peripheral lowlands such as the mentioned Kinzig-Murg-Rinne, foothills or hill countries and the low mountain ranges ( Black Forest , Vosges , Palatinate Forest, Odenwald ) as well as Kraichgau and the Hessian hill country between Darmstadt and Main are connected . In some places, such as Speyer , the lower terrace extends to the course of the river. There their sediments come in a wedge shape up to the Rhine and support the cathedral , among other things . The “jumps” here between the lowland, the low terrace and the high terrace are each up to ten meters, edges of the terrain that can be easily followed in the built-up urban area. The gravel layers are covered by the river Schlick , which forms a layer of clay of around half a meter.

Influences

The straightening of the Rhine and the associated cutting of the now faster flowing river resulted in a general lowering of the groundwater in the sediment body of the lower terrace. Sometimes there are also swamp moors or traces of earlier such wetlands on the lower terrace, especially in gullies. The sinking of the groundwater level into lower levels also results in a change in the soil structures and characteristics. Thus arose the southern Upper Rhine from boggy alluvial soils after the regular flooding stayed away, Parabraunerden and brown earth -Parabraunerden what the agronomic use very accommodates. Types that predominate in this area under consideration, also in the form of bands (para) brown earths, podsol-like variants are also to be found numerous.

Regardless of whether it is forest-covered or presented as open cultivated land , both manifestations are based on the same initial situation, mostly with the same original material, but differ significantly in the further development of their soils and surface forms after centuries of separate forms of use . Above all, soil erosion occurs in the arable sector, especially if, for example, asparagus or grapevine rows, field furrows or the like are not laid parallel to the slope and thus promote erosion, their attack surfaces. This also applies to paths and paths that promote linear sediment transport - even when the vegetation is otherwise completely covered .

use

After the intensive human use (logging, forest pasture , litter use , resin extraction , etc. ), the original forest cover is barely available, at most in a restored or rudimentary form. Diversity still alternates with monotonous "forest plantations". In some areas, but not only the attempt is made as close to the potential natural vegetation (establishment of Bann and protection forests get hold), but there are also efforts, special cultural landscapes with their mostly immigrant Eastern European or Mediterranean plant communities to obtain ( sandy grass meadows , heath formations ) . Pine proportions are quite high over large areas.

In terms of arable farming , asparagus (on sand) and tobacco cultivation , and earlier also hops , are important in many areas . However, other intensive forms of agriculture such as growing vegetables can also be found.

The gravel deposits are important for road construction and the construction industry. Rheingold was found in 1906 in the Niederterrasse near Endingen am Kaiserstuhl .

Literature and further links

Individual evidence

  1. ^ Alfred Osann , Die Mineralien Baden , 1927, p. 30