DOI: 10.1016/j.quascirev.2013.02.018
Scopus记录号: 2-s2.0-84900479261
论文题名: Subglacial sediment, proglacial lake-level and topographic controls on ice extent and lobe geometries during the Last Glacial Maximum in NW Russia
作者: Larsen E. ; Fredin O. ; Jensen M. ; Kuznetsov D. ; Lyså A. ; Subetto D.
刊名: Quaternary Science Reviews
ISSN: 2773791
出版年: 2014
卷: 92 起始页码: 369
结束页码: 387
语种: 英语
英文关键词: Ice sheet
; Ice-bed interface
; Ice-lake interaction
; Ice-lobe dynamics
; Ice-lobe geometries
; Last Glacial Maximum
Scopus关键词: Glacial geology
; Glaciers
; Lakes
; Landforms
; Rivers
; Sea ice
; Digital elevation model
; Ice sheet
; Ice-lake interaction
; Last Glacial Maximum
; Pore-water pressures
; Subglacial sediment
; Topographic control
; Topographic thresholds
; Sediments
; bedform
; Last Glacial Maximum
; pore pressure
; proglacial environment
; reconstruction
; Scandinavian Ice Sheet
; subglacial deposit
; topographic mapping
; topography
; Russian Federation
; Vaga
英文摘要: Investigations in sections along the rivers Severnaya Dvina and Vaga, and morphological mapping based on a new digital elevation model and Landsat imagery, allow for a reinterpretation of the extent of the Scandinavian Ice Sheet during the Last Glacial Maximum (LGM). The reconstruction provides a muchbetter link between stratigraphical and morphological expression of glaciation than previous proposals. Most striking is the configuration of long, low-gradient ice-lobes (ice-streams) extending for some 300-400km up the wide and smooth river valleys. Their extremely low surface gradients are evidenced by glacial trimlines that formed along the sides of the ice-lobes in contact with the gentle valley slopes. In the main valleys, end moraines marking terminal positions are present, whereas drumlins are rare in the peripheral areas of the ice sheet but found in some tributary valleys at somewhat higher elevations. Large drumlin fields, however, are found farther up-ice. The glacial sediment succession is composed of waterlain sediments and tills. The sediments provide evidence of distal ice damming, glacier overriding and retreat, and finally distally glaciolacustrine sedimentation and lake drainage. The diamicton unit associated with the LGM shows evidence of basal coupling, although more striking is the abundant evidence for ice-bed decoupling. These include in situ waterlain sediments within tills, and clastic sills running along the till/substrate contact showing lift-off. These features indicate that the weight of the glacier lobes was, to a large extent, carried by pore-water pressure in subglacial sediments, and that subglacial shear and erosion were moderate. Thus, fast ice flow in the lobes is envisaged. The balance between glacier weight and pore-water pressure was probably maintained over time by the buoyancy effect of glaciers advancing into proglacial lakes. Subglacial lakes may have formed by capture of proglacial lakes during glacial advance. The combination of low-gradient ice and decoupled beds indicate that glacier advance and extent was largely controlled by lake levels and topographic thresholds. This is taken to indicate that steeper-gradient ice much farther upstream was providing the gravitational push. A presumably abrupt change in ice-surface profile is supported by the mapped distribution of glacial bedforms. The model presented herein potentially has wide applicability for large parts of northern Russia as the topographic setting and glacier advance in lakes across fine-grained low-permeable sediments provide very similar conditions. © 2013 Elsevier Ltd. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/60283
Appears in Collections: 过去全球变化的重建
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作者单位: Geological Survey of Norway, P.O. Box 6315 Sluppen, NO-7491 Trondheim, Norway; Norwegian University of Science and Technology, Museum of Natural History and Archaeology, NO-7491 Trondheim, Norway; Norwegian University of Science and Technology, Department of Geography, NO-7491 Trondheim, Norway; The University Centre in Svalbard, P.O. Box 156, NO-9171 Longyearbyen, Norway; Institute of Limnology, Russian Academy of Sciences, Sevastyanova Str. 9, St. Petersburg 196105, Russian Federation; Department of Physical Geography and Environment, Alexander Herzen State, Pedagogical University, St. Petersburg 191186, Moika 48, Russian Federation
Recommended Citation:
Larsen E.,Fredin O.,Jensen M.,et al. Subglacial sediment, proglacial lake-level and topographic controls on ice extent and lobe geometries during the Last Glacial Maximum in NW Russia[J]. Quaternary Science Reviews,2014-01-01,92