LGM and late-glacial fluctuations in the Eastern Alps

Abstract

Abstract Studies of glacier development in the Eastern Alps around the Last Glacial Maximum (LGM) for more than a hundred years have created a reasonably well-based knowledge of glacier extent, sedimentation, and palaeoclimate, as well as chronology. This was obtained from broad and detailed mapping, palynological investigations, and radiocarbon dating. Despite a very cold climate between 31 and 21 ka BP, topographical constraints meant that glacier extent was limited to tributary valleys of the main trenches until about 24 ka BP. Then, rapid ice build-up in the main longitudinal valleys led to extended ice streams and to piedmont glaciers in the foreland. This build-up virtually ended at ca. 21 ka BP, according to radiocarbon dates obtained from organic matter embedded in the outwash and periglacial gravels (Niederterrasse). The LGM possibly lasted 3000–4000 years and shows a short ‘Maximalstand’ and a more prolonged ‘Hochstand’, both connected with outwash deposits. The ice decay was apparently very fast, and the glaciers vanished from the longitudinal valleys probably within some hundreds of years. This retreat was interrupted by two short oscillations of active glaciers in contact with huge masses of inactive ice occupying the main valley floors, before these became totally ice-free. These events at the beginning of the Oldest Dryas (ca. 16 ka BP), were followed by a distinct glacier readvance (Gschnitz) marked by end moraines and outwash fans. According to some radiocarbon dates, this occurred around 14 ka BP. During the Bolling interstade, the valleys became almost ice-free. The next two glacier readvances (Daun and Egesen) were limited to cirques and the higher parts of the valleys, and are dated to the Older and Younger Dryas stades respectively.