Wolfratshausen lake
The Wolfratshausener See is a glacial lake that has disappeared in today's Wolfratshausen Basin in the Bavarian foothills of the Alps . It emerged after several cold periods .
Ice age formation
The Wolfratshausen lake was created as a glacial basin by deepening the Isar-Loisach glacier in the Loisach-Voralpental. In this gravel not be stored in a walk-in land surface, but deep channels filled in Tertiary made. Tertiary Riedel were cleared out as watersheds . The basin was created at the end of the third to last Ice Age, the Mind Ice Age . The Tiefenschurf repeated, gravel and the second last ice, the Rißeiszeit , and last, the Würm were deposited on what by drilling at Weidach and Gelting could be detected. The ice thickness over the Wolfratshausen Basin is given as 250-300 meters. A lake probably existed in the Wolfratshausen area in the interglacial period between the Riss and Würme Ice Age. It can definitely be proven a short time after the ice age. The lake was part of a huge lake landscape that formed after the last ice age with the melt water from the glaciers in the Alpine foothills.
Location and extent
At the end of the Würme Ice Age, the location of the lake connected to the northern end of the Kochelsee in the south , separated from it only by the Penzberger Molasse bar. In the north, the sea border was at its overflow at Schäftlarn monastery . The length of the lake was thus about 30 kilometers. Achmühle formed the western border and the area in front of Dietramszell the eastern border . The western sole formed the Wolfratshausener-Weidacher tongue basin, while Diffluenz created an eastern one, which was formed by the Eglinger - Deininger tongue basin. Its meltwater flowed into today's Gleißental and Hachinger Tal . The Babenstuben moors in the Königsdorf basin are remnants of the former lake. In the lake there was at least one large raised terrace island with a layer of loess south of Wolfratshausen, which divided the water into the western and eastern tongue. The lake had the largest deepening under the eastern urban area of Wolfratshausen, about 20 kilometers from the northernmost ice border. The bottom of the valley was around 150 meters, further north an average of 20–30 meters below the current valley floor.
Disappearance of the lake
During the Riss Ice Age and over long periods of the Würme Ice Age, the Ur- Isar did not drain the Wolfratshausen Basin northwards from what is today Bad Tölz , but ran from what is today Gaißach north-east towards Holzkirchen . After the last fall of the ice, the Wolfratshausen Basin was filled with water. Around 15,000 years ago, towards the end of the Würme Ice Age, the Isar broke through a molasse mirror near Bad Tölz to the north and flowed into Lake Wolfratshausen. As a result, this was filled with delta gravel and sea clays from the confluent Isar and had only a short remaining existence.
Extensive amounts of gravel from the Isar were deposited on the lake bed. They took him to two phases to silt up . At first the delta of the new Isar was located north of Bad Tölz. After the southern part of the lake had silted up, it relocated its estuary to what is now Gelting. Now the Wolfratshausen lake only existed between Gelting and Schäftlarn monastery . Eventually the Isar broke through the terminal moraine and the rest of the lake ran out.
Individual evidence
- ↑ a b Hermann Jerz : The Wolfratshausener pool: its glacial conditioning and overdeepening . In: Deutsche Quartärvereinigung eV (Ed.): Ice Age and Present . Vol. 29, No. 1 , 1979, ISSN 0424-7116 , pp. 63–69 , doi : 10.3285 / eg.29.1 ( PDF file; 3.48 MB [accessed June 8, 2020]).
- ^ Joseph Knauer: Diluvial valley filling and epigenesis in southern Bavaria . In: Bayerisches Geologisches Landesamt (Ed.): Geologica Bavarica . No. 11 . Munich 1952 ( PDF file; 2.2 MB [accessed June 8, 2020]).
- ↑ Rolf KF Meyer, Hermann Schmidt-Kaler: In the footsteps of the Ice Age south of Munich - eastern part (= walks in the history of the earth, Volume 8). Pfeil, Munich 1997, ISBN 3-931516-09-1 , p. 35.
- ↑ Historical Geretsried Working Group - from the Ice Age to the Modern Age. In: www.arbeitskreis-historisches-geretsried.de. Retrieved December 5, 2015 .