Sedimentology of the late Pleistocene to Holocene paleolake Merzbacher in the northern Inylchek Valley (central Tien Shan, Kyrgyzstan)
- Autor(en)
- Hermann Häusler, Alexander Kopecny, Diethard Leber, Michael Wagreich, Susanne Gier, Sabine Hruby-Nichtenberger
- Abstrakt
During an expedition to the central Tien Shan, Eastern Kyrgyzstan, in 2011, lake deposits in the Northern Inylchek Valley were investigated. Deposits at four locations were studied; from West to East at the Peremitschka plain, which is seasonally flooded by melt waters and then turns to Lower Lake Merzbacher, which is dammed by the Southern Inylchek Glacier; at the stable moraine-pond-ensemble, and at the glacier front of the Northern Inylchek Glacier. The development of the Southern- and Northern Inylchek Glacier is quite complex, because in the Holocene the Northern Inylchek Glacier retreated and ad-vanced at least twice, and hence two fluctuation cycles can be described. The youngest fluctuation-cycle has been documented for the last century by remote sensing imageries. In the 1950s a proglacial lake developed, which enlarged to the 1990s by four kilometres, then termed Upper Lake Merzbacher. In 1996 the Northern Inylchek Glacier rapidly advanced again, shortening the Upper Lake Merzbacher by 75%. For analysing the older cycle, which happened before 1900, fine-grained, bedded deposits in the Peremitschka, in the stable mo-raine-pond-ensemble, and at the front of the Northern Inylchek Glacier, consisting of clayey silt, sandy silt and sandy clay, were investigated. Clay mineralogy of these fine-grained deposits reflects the mineralogical composition of the surrounding Paleozoic bedrock, the bulk spectrum containing potassium feldspar, plagioclase, chlorite, quartz, muscovite, biotite and calcite. The fine-grained clay- and silt-deposits of the stable moraine-pond-ensemble plot in the field of pelagic suspension in Passega’s CM-grain size diagram. Soft-sediment deformation of the laminated lake-sediments on top of the stable moraine-pond-ensemble comprises microstructures such as asymmetrical and disharmonic folds. The glacio-lacustrine deposits on top of the stable moraine-pond-ensemble are overlain by ground moraine material indicating glacier advance at the end of the older fluctuation cycle, during which the Northern Inylchek Glacier probably piled up multiple moraine walls east of the Peremitschka plain. Lining up fine-grained glacio-lacustrine deposits covering the Peremitschka, the stable moraine-pond-ensemble, and the surged Northern Inylchek Glacier, one can delineate a paleolake of approximately 10 kilometres in length, which results in a paleo water level at 3500 m altitude. This lake is termed “Paleolake Merzbacher”, which is inferred to have been dammed by both the Southern and Northern Inylchek Glaciers. Late-glacial to Neoglacial moraines at Poljana, at an altitude of 3530 m above sea level, indicate that the Southern Inylchek Glacier was able to dam Paleolake Merzbacher.
- Organisation(en)
- Institut für Geologie
- Journal
- Austrian Journal of Earth Sciences
- Band
- 107
- Seiten
- 74-88
- ISSN
- 0251-7493
- Publikationsdatum
- 2014
- Peer-reviewed
- Ja
- ÖFOS 2012
- 105901 Glaziologie, 105121 Sedimentologie, 207402 Fernerkundung, 105404 Geomorphologie
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/eb281625-8f27-4678-a533-6263005681bc