Schramberg Basin

from Wikipedia, the free encyclopedia
Schramberg with the Hohenschramberg castle ruins

The Schramberg Basin (also called Schramberg Basin in older literature) is the geological name for an approximately 160 km long and 50 km wide intramontane molasse basin (or inner molasse ) that extends approximately north-east-south-west and is located at the end of the Variscan mountain formation in central Baden-Württemberg and western Bavaria has arisen. The maximum thickness of the permocarbonic sediments and volcanic rocks reaches up to 500 m in outcrops, in boreholes up to 600 m in thickness are proven. The basin and its sediments are now largely covered by younger sediments. It is the second largest permocarbon basin in Baden-Württemberg.

location

The Schramberg Basin lies northeast of the central Black Forest almost entirely in the area of ​​Baden-Württemberg. Only thin foothills under recent cover reach western Bavaria in the east. In the north it is separated from the Kraichgau Basin by the Northern Black Forest Sill , and in the south by the Southern Black Forest Sill from the Northern Switzerland Basin . In the southwest, the Schramberg basin ends abruptly at the Schramberg main fault against the Hornberg threshold , in the east at the Main-Tauber threshold . The only outcrops can be found in the Schramberg urban area.

Origin and history of sedimentation

The oldest sediments in the basin are dark gray silt clay stones (Tierstein formation), which only come to light in two places near Schramberg. However, they have been reliably proven by drilling to Bad Urach . In the pelvic center they are up to 300 m thick. Spores studies have an age of Lower to Middle Stephanian result, d. This means that the pelvis formation has certainly already started in the upper carbon. The Tierstein Formation is overlaid at least in the basin center (drilled there) by the volcanic rocks of the Geisberg Formation. This formation consists of tuffs , tuffites and quartz porphyries (chimneys and ignimbrites ). Absolute age dates vary widely between 286 and 296 million years. This corresponds to an underperm age. This is followed by the arcoses , breccias and conglomerates of the Schramberg Formation. In the only outcrop in the urban area of ​​Schramberg, the Schramberg Formation is 340 m thick or is proven by drilling. Due to its location above the Geisberg Formation, it can safely be dated to the Permian. With the deposition of the sediments of the Schramberg Formation, the development of the Schramberg Basin as an independent sedimentation basin is complete. Above it lies the Kirnbach Formation of the Zechstein, followed by the fluvial Tiger Sandstone Formation, which z. Partly also dovetailed with the Kirnbach formation and represents them. The lithostratigraphic sequence of the Schramberg Basin at a glance:

supporting documents

Individual evidence

  1. ↑ Dieter Ortlam: New aspects to the Cenozoic development in the northern part of the Mediterranean - Mjosen - Zone. Geologische Rundschau, 70 (1): 344-353, Stuttgart 1981 doi : 10.1007 / BF01764333

literature

  • Matthias Geyer, Edgar Nitsch and Theo Simon: Geology of Baden-Württemberg. 5th completely revised edition, 627 pages, Schweizerbart, Stuttgart 2011 ISBN 978-3-510-65267-9
  • Edgar Nitsch and Hubert Zedler: Upper Carboniferous and Permian in Baden-Württemberg. State Office for Geology, Raw Materials and Mining, Information, 22: 7-102, Freiburg 2009.