Glacial erosion of the Sub-Cambrian Peneplain in Sweden
Adrian M. HallBradley W. GoodfellowJakob HeymanSeulgi MoonMarc W. CaffeeKarin EbertClas HättestrandMaarten KrabbendamStephen J. MartelJens-Öve NäslundT. PerronFinlay M. StuartArjen P. Stroeven
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Kongur Mountain is the largest center of modern glaciation on the Pamir Plateau.During the glacial-interglacial cycles of the Quaternary,Kongur Mountain was extensively and repeatedly glaciated,and the glacial landforms from multiple glaciations are well-preserved in valleys,in basins,and on the piedmonts.Dating samples have been collected according to the distribution and weathering of the glacial tills,the relationship among the glacial deposits,and the loess or soil developed on the moraines. Electron spin resonance(ESR) dating of the samples was done using the germanium(Ge) centers in the glacial quartz grains,which are sensitive to both sunlight and grinding.The ages of the glacial deposits can be divided into four clusters,i.e.,13.1±0.8–27.0±2.2,36.4±3.3–48.7±5.7,65.6±6.8–86.6±8.9,and 105.6±9.4–178.3±17.8 ka.Six glacial advances in this region have been confirmed,which are equivalent in age to the Little Ice Age(LIA) ,Neoglaciation,marine oxygen isotope stages(MIS) 2,mid-MIS3,MIS4,and MIS6.The largest local last glacial maximum(LGML) occurred during MIS4 rather than the global Last Glacial Maximum(LGMG) of MIS2,and a glacial advance that occurred during mid-MIS3 was also larger than the LGMG.Furthermore,deeply weathered tills below 3500 m a.s.l.on the western slope of Kongur Mountain,when compared with the ages of the oldest glaciation of the Muztag Ata region,likely occurred prior to the penultimate glacial cycle.The glacial landforms prior to the penultimate glacial cycle on the northern slope are not well-preserved due to erosion after deposition. Several glacial deposits are only speculated to be distributed at higher elevations on the southwest side of the Gaizi Checkpoint. The extensive hummocky moraines on the western slope were formed by multiple glacial advances,and the latest glacial advance corresponded to mid-MIS3.
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Outwash plain
Last Glacial Maximum
Terminal moraine
Deglaciation
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Quaternary glacial deposits of the Zanda basin and its surrounding mountains may be divided in space distribution into:① glacial deposits in U-shape valleys and foothills in the basin and its surrounding mountains, ② glacial deposits in deep-incised valleys around the basin, ③ glacial deposits on the basin surface, ④ glacial deposits on high terraces of river valleys and in gullies of the basin, and ⑤ glacial deposits in piedmont zones of mountains around the basin. Glacial deposits in different areas differ markedly with respect to the gravel composition, roundness, textures and structures, geomorphologic features. The Quaternary glacial development in the region may be divided from early to late times into the periglacial stage, glacial advance stage, biggest glacial stage and glacial retreat stage according to the features and distribution of glacial deposits. The glacial types corresponding to these stages are the valley, piedmont and ice-cap glacier development stage, ice field glacier development stage and ice-cap, valley glacier and piedmont glacier development stage. The existing data indicate that the Zanda basin and its surrounding mountains are areas where the most abundant, complete and continuously occurring and best-preserved Quaternary glacial deposits are found on the Qinghai-Tibet Plateau. This research provides valuable basic data for the study of Quaternary glaciers in this region and the Qinghai-Tibet Plateau, division and correlation of glacial epochs, establishment of climatostratigraphy and climatic and paleoenvironmental studies.
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Surface exposure dating
Terminal moraine
Last Glacial Maximum
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ABSTRACT This paper reviews the changing environments, developing landforms and terrestrial stratigraphy during the Early and Middle Pleistocene stages in Scotland. Cold stages after 2.7 Ma brought mountain ice caps and lowland permafrost, but larger ice sheets were short-lived. The late Early and Middle Pleistocene sedimentary record found offshore indicates more than 10 advances of ice sheets from Scotland into the North Sea but only 4–5 advances have been identified from the terrestrial stratigraphy. Two primary modes of glaciation, mountain ice cap and full ice sheet modes, can be recognised. Different zones of glacial erosion in Scotland reflect this bimodal glaciation and the spatially and temporally variable dynamics at glacier beds. Depths of glacial erosion vary from almost zero in Buchan to hundreds of metres in glens in the western Highlands and in basins both onshore and offshore. The presence of tors and blockfields indicates repeated development of patches of cold-based, non-erosive glacier ice on summits and plateaux. In lowlands, chemical weathering continued to operate during interglacials, but gruss-type saprolites are mainly of Pliocene to Early Pleistocene age. The Middle Pleistocene terrestrial stratigraphic record in Scotland, whilst fragmentary and poorly dated, provides important and accessible evidence of changing glacial, periglacial and interglacial environments over at least three stadial–interstadial–interglacial cycles. The distributions of blockfields and tors and the erratic contents of glacial sediments indicate that the configuration, thermal regime and pattern of ice flow during MIS 6 were broadly comparable to those of the last ice sheet. Improved control over the ages of Early and Middle Pleistocene sediments, soils and saprolites and on long-term rates of weathering and erosion, combined with information on palaeoenvironments, ice extent and sea level, will in future allow development and testing of new models of Pleistocene tectonics, isostasy, sea-level change and ice sheet dynamics in Scotland.
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Eemian
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Terminal moraine
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Describes two tills exposed in the Maybeso Creek valley on the east coast of the island, differing in stratigraphic position and degree of weathering. The younger is blue-gray, compacted and weathered to 3 ft depth; the older is coarse, leached and with a particle of surface oxidation that suggests it is a remnant of the B horizon of a fossil till soil truncated by advance of the glacier that deposited the younger till. Such a twofold division of glacial deposits is found elsewhere in Southeast Alaska and may represent advances of the Wisconsin glaciation. Four recessional moraines of the younger till mark stillstands during the final retreat of the last glacier.
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Glacial landform
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Marine transgression
Terrace (agriculture)
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