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Glacial geomorphology of the Altai and Western Sayan Mountains, Central Asia
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK). Purdue University, USA.ORCID-id: 0000-0003-0306-5291
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).ORCID-id: 0000-0001-8812-2253
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
Vise andre og tillknytning
2016 (engelsk)Inngår i: Journal of Maps, ISSN 1744-5647, E-ISSN 1744-5647, Vol. 12, nr 1, s. 123-136Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In this article, we present a map of the glacial geomorphology of the Altai andWestern Sayan Mountains, covering an area of almost 600,000 km2. Although numerous studies provide evidence for restricted Pleistocene glaciations in this area, others have hypothesized the past existence of an extensive ice sheet. To provide a framework for accurate glacial reconstructions of the Altai and Western Sayan Mountains, we present a map at a scale of 1:1,000,000 based on a mapping from 30 m resolution ASTER DEM and 15 m/30 mresolution Landsat ETM+ satellite imagery. Four landform classes have been mapped: marginal moraines, glacial lineations, hummocky terrain, and glacial valleys. Our mapping reveals an abundance of glacial erosional and depositional landforms. The distribution of these glacial landforms indicates that the Altai and Western Sayan Mountains have experienced predominantly alpine-style glaciations, with some small ice caps centred on the higher mountain peaks. Large marginal moraine complexes mark glacial advances in intermontane basins. By tracing the outer limits of present-day glaciers, glacial valleys, and moraines, we estimate that the past glacier coverage have totalled to 65,000 km2 (10.9% of the mapped area), whereas present-day glacier coverage totals only 1300 km2 (0.2% of the mapped area). This demonstrates the usefulness of remote sensing techniques for mapping the glacial geomorphology in remote mountain areas and for quantifying the past glacier dimensions. The glacial geomorphological map presented here will be used for further detailed reconstructions of the paleoglaciology and paleoclimate of the region.

sted, utgiver, år, opplag, sider
2016. Vol. 12, nr 1, s. 123-136
Emneord [en]
glacial geomorphology, paleoglaciology, Altai Mountains, Western Sayan Mountains, remote sensing
HSV kategori
Forskningsprogram
naturgeografi
Identifikatorer
URN: urn:nbn:se:su:diva-122453DOI: 10.1080/17445647.2014.992177ISI: 000365605200012OAI: oai:DiVA.org:su-122453DiVA, id: diva2:866432
Prosjekter
Central Asia Paleoglaciology Project (CAPP)
Forskningsfinansiär
Swedish Research Council, No. 2011-4892Tilgjengelig fra: 2015-11-02 Laget: 2015-11-02 Sist oppdatert: 2020-02-20bibliografisk kontrollert
Inngår i avhandling
1. Paleoglaciology of the Tian Shan and Altai Mountains, Central Asia
Åpne denne publikasjonen i ny fane eller vindu >>Paleoglaciology of the Tian Shan and Altai Mountains, Central Asia
2016 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

The mountain-systems of Central Asia, act as barriers to atmospheric circulation patterns, which in turn impose striking climate gradients across the region. Glaciers are sensitive indicators of climate change and respond to changes in climate gradients over time by advancing during cold and wet periods and receding during warm and dry periods. The aim of this thesis is to investigate whether there are large-scale patterns in how past glaciers in the Tian Shan and the Altai Mountains of Central Asia responded to climate change. Multiple methods have been used, including: remote sensing, terrain analysis, field investigations, and cosmogenic nuclide (CN) dating. The glacial landform records indicate that the region experienced mainly alpine-style glaciations in the past. Large complexes of ice-marginal moraines in high elevation basins are evidence of outlet glaciers sourced from large valley glaciers, ice caps and ice-fields, and these moraine sequences, record the maximum extent of paleoglaciation. In the Ikh-Turgen Mountains, located in the continental, eastern Altai Mountains, deglaciation of these moraines occurred during marine oxygen isotope stage (MIS) 3 at ~45 ka. This is consistent with a colder and wetter climate during this time, inferred from ice core and lake level proxies. Another deglacial phase occurred during MIS 2 at ~23 ka, synchronous with the global Last Glacial Maximum. In the Russian Altai Mountains, lobate moraines in the Chuya Basin indicate deglaciation at ~19 ka, by a highly dynamic paleoglacier in the Chagan-Uzun catchment, which experienced surge-like behaviour. Furthermore, across the Tian Shan, an evaluation of new and existing CN glacial chronologies (25 dated moraines) indicates that only one regional glacial stage, between 15 and 28 ka (MIS 2), can be defined and spatially correlated across the region. These paleoglaciers were mainly restricted to valleys as a result of arid conditions during this time and variation in their extents is interpreted to reflect topographic modulation on regional climate. The ages of the oldest evidence for robust local glacial stages in the Tian Shan are not yet well constrained, however, moraines in the central Kyrgyz Tian Shan and the eastern Chinese Tian Shan have apparent minimum ages overlapping with MIS 5 and MIS 3 (with missing MIS 4 and 6 stages). However, different geological processes, such as inheritance and post-depositional shielding (e.g. deposition by surging glaciers or hummocky terrain deposition), have influenced the dating resolution, making several moraine ages inappropriate for regional comparison. Finally, to quantify regional patterns of paleoglaciation, the hypsometry (area-elevation distribution) of glacial landforms is used to estimate average paleo equilibrium line altitudes for the region. This analysis shows that while present-day ELAs mirror strong climate gradients, paleoglaciation patterns were characterised by more gentle ELA gradients. The paleo-ELA depressions across Central Asia were most prominent in the continental southern and eastern regions (500–700 m). Finally, the results from this thesis, show that Central Asia was repeatedly glaciated in the past, but underscore the importance of considering 1) catchment characteristics and styles of glaciation and 2) other non-climatic factors controlling glacier dynamics when interpreting CN chronologies to make paleoclimate inference.

sted, utgiver, år, opplag, sider
Stockholm: Department of Physical Geography, Stockholm University, 2016. s. 34
Serie
Dissertations from the Department of Physical Geography, ISSN 1653-7211 ; 59
Emneord
Paleoglaciology, glacial geomorphological mapping, cosmogenic nuclide dating, Tian Shan, Altai Mountains
HSV kategori
Forskningsprogram
naturgeografi
Identifikatorer
urn:nbn:se:su:diva-134748 (URN)978-91-7649-567-4 (ISBN)978-91-7649-568-1 (ISBN)
Disputas
2016-12-09, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (engelsk)
Opponent
Veileder
Prosjekter
Central Asia Paleoglaciology Project (CAPP)
Forskningsfinansiär
Swedish Research Council, No. 2011-4892
Merknad

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Accepted. Paper 5: Manuscript.

Tilgjengelig fra: 2016-11-16 Laget: 2016-10-17 Sist oppdatert: 2020-03-31bibliografisk kontrollert

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