ALBERT

Description: The masses of sediment in the Molasse Basins of Switzerland, Germany and Austria total 0.299×1021 g. In the Neogene, other sediment shed north of the Alps went to the Rhine Graben (0.03×1021 g), and on to the northern European plains and North Sea (0.81×1021 g). During the Quaternary, the drainage systems were drastically reorganized, with the Danube capturing streams that drain the German and Austrian Alps, and delivering the sediment to the Pannonian Basin (0.15×1021 g) and on to the Black Sea (0.31×1021 g). Sediment shed to the west has entered the Bresse and Rhone Grabens (0.05×1021 g) and been deposited in the Rhone Delta (0.19×1021 g) and on the floor of the Gulf of Lions (0.24×1021 g). Sediment shed from the south side of the Alps resides in the Po Basin and Adriatic Sea that have total sediment masses of 0.38×1021 g and 0.36×1021 g respectively. Mass balanced reconstructions suggest that during the Chattian and Aquitanian (Late Oligocene-Early Miocene) thrusting in Switzerland, southern Germany and western Austria (Vorarlberg-Tyrol) resulted in mountains of Himalayan height, with elevations up to 7 km. Erosion attacked these mountains, existing sediments in the Molasse basins alone are equivalent to a layer 0.5 km thick, but represent only a fraction of the material originally deposited in them. Sediments equivalent to another 1.7 km thickness occur in the more peripheral basins. Sediment supply was greatly reduced in the middle Early Miocene (Burdigalian) indicating that the elevation of the mountains had decreased more rapidly than can be explained by erosion alone, which, after isostatic adjustment would have reduced the elevations only to about 5 km. The loss of elevation might have been due to a slow (ca. 1 my) flexural response to the narrow load on the southern edge of the European continental block, or to physical collapse of the mountains.