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1
Arnscheidt, Constantin W., and Daniel H. Rothman. "Routes to global glaciation." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 476, no. 2239 (2020): 20200303. http://dx.doi.org/10.1098/rspa.2020.0303.
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Theory and observation suggest that Earth and Earth-like planets can undergo runaway low-latitude glaciation when changes in solar heating or in the carbon cycle exceed a critical threshold. Here, we use a simple dynamical-system representation of the ice–albedo feedback and the carbonate–silicate cycle to show that glaciation is also triggered when solar heating changes faster than a critical rate. Such ‘rate-induced glaciations’ remain accessible far from the outer edge of the habitable zone, because the warm climate state retains long-term stability. In contrast, glaciations induced by changes in the carbon cycle require the warm climate state to become unstable, constraining the kinds of perturbations that could have caused global glaciation in Earth’s past. We show that glaciations can occur when Earth’s climate transitions between two warm stable states; this property of the Earth system could help explain why major events in the development of life have been accompanied by glaciations.
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Duk-Rodkin, Alejandra, and Owen L. Hughes. "Pleistocene Montane Glaciations in the Mackenzie Mountains, Northwest Territories." Géographie physique et Quaternaire 46, no. 1 (2007): 69–83. http://dx.doi.org/10.7202/032889ar.
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ABSTRACT During the Pleistocene the Mackenzie Mountains were affected by a series of glaciations. Through all the glaciations a single pattern seems to have been repeated: a Cordilleran ice sheet formed to the west of the continental divide and montane valley glaciers formed to the east. The montane glaciers in the Mackenzie Mountains emanated from two differents sources: a) a glacial divide, lying generally along the topographic divide between Pacific and Arctic drainage, and dividing the westerly flowing Cordilleran Ice Sheet from easterly and northerly flowing montane glaciers, b) local peaks in the Canyon Ranges. There were two well defined glacial advances in this mountain region: lllinoian, Late Wisconsinan, and one or more less defined pre-lllinoian glaciation(s). lllinoian and Late Wisconsinan glaciations are herein named Mountain River and Gayna River glaciations respectively. These advances are usually identifiable in valleys by frontal and segments of lateral moraines and glacial erosional features. Pre-lllinoian glaciation(s) have been recognized so far only in stratigraphie sections. The older advances were more extensive than the Gayna River advance; associated deposits occur higher on the valley sides and further down the valley than those associated with Gayna River Glaciation. During Mountain River Glaciation some of the montane glaciers in the Canyon Ranges merged to form piedmont glaciers. In contrast, during Gayna River Glaciation, the local glaciers consisted of single tongues, and these were mostly restricted to tributary valleys that had northward facing cirques.
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Lindner, Leszek, and Jan Dzierżek. "Pleistocene deposits in the western part of the Holy Cross Mountains." Studia Quaternaria 36, no. 2 (2019): 75–85. http://dx.doi.org/10.24425/sq.2019.126381.
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The paper presents characteristics of the Pleistocene sediments in the western part of the Holy Cross Mountains. They are subdivided into four complexes and their stratigraphic setting is referred to the updated scheme for the Pleistocene of Poland. The Preglacial Complex includes fluvial sediments characteristic for its lack of Scandinavian material. Sediments of three main glaciations (Nidanian, Sanian 1 and Sanian 2) within the South Polish Complex, are referred also as the South Polish Glaciations. The oldest of these glaciations (Nidanian) is separated from the middle glaciation (Sanian 1) by sediments of the Podlasian Interglacial, represented by clay at the Kozi Grzbiet Cave that contains faunal remains and record of the Brunhes/Matuyama palaeomagnetic boundary. During the middle (Sanian 1) and youngest glaciation (Sanian 2), the Holy Cross Mountains were almost completely covered by the Scandinavian ice sheet, forming glacial deposits separated by fluvial series of the Ferdynandovian Interglacial. The Middle Polish Complex begins with sediments of the Mazovian Interglacial, represented by a pollen record from the Zakrucze site. They are followed by deposits of periglacial and fluvial origin of the Liwiecian Glaciation, Zbójnian Interglacial, Krznanian Glaciation and Lublinian Interglacial. The following glaciation (Odranian) is represented by the youngest glacial deposits that document presence of the Scandinavian ice-sheet in the westernmost part of the Holy Cross Mountains. The North Polish Complex is composed of a climatic warming (Eemian Interglacial) and cooling (Vistulian Glaciation), and is represented by valley and periglacial deposits. The last cooling of the Pleistocene is recorded in faunal remains in the Raj Cave.
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Tsai, Cheng-Lung, Kôhei Kubota, Hong-Thai Pham, and Wen-Bin Yeh. "Ancestral Haplotype Retention and Population Expansion Determine the Complicated Population Genetic Structure of the Hilly Lineage of Neolucanus swinhoei Complex (Coleoptera, Lucanidae) on the Subtropical Taiwan Island." Insects 12, no. 3 (2021): 227. http://dx.doi.org/10.3390/insects12030227.
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The present study demonstrates that the complicated genetic structure of the hilly lineage of the Neolucanus swinhoei complex was driven by its biological features and habitat requirements as well as hindrance by the CMR during periodical Pleistocene glaciations. The results revealed a tendency of geographical differentiation and major and sub- lineage divergences before and after the Riss glaciation, followed by stable population growth during Würm glaciation. At least four refugia were inferred for N. swinhoei during the Riss–Würm glaciations. The ancestral haplotype retention in the cytochrome oxidase subunit I (COI) gene and compensated substitution in 16S rRNA gene is a possible evolutionary scenario resulting in the inconsistent evolution pattern between COI and 16S rRNA gene coupled with the long-distance dispersal of N. swinhoei. Although the CMR did hinder the dispersal of N. swinhoei, its ancestors may have dispersed to eastern Taiwan through the northern and southern low mountains of the CMR before the Riss glaciation. Our finding suggests that the population growth in the Würm glaciation led a dispersal back to western Taiwan, which is contrast to the more common dispersal scenario from western Taiwan to eastern populations proposed in other studies.
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Barrows, Timothy T., John O. Stone, L. Keith Fifield, and Richard G. Cresswell. "Late Pleistocene Glaciation of the Kosciuszko Massif, Snowy Mountains, Australia." Quaternary Research 55, no. 2 (2001): 179–89. http://dx.doi.org/10.1006/qres.2001.2216.
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AbstractLate Pleistocene glaciation of the Australian mainland was restricted to a small area of the southeastern highlands. Geomorphic mapping of the area and exposure dating using thein situproduced cosmogenic isotope10Be provides evidence for at least two distinct glaciations. The Early Kosciuszko glaciation consisted of a single glacier advance before 59,300 ± 5400 years ago (Snowy River Advance). The Late Kosciuszko glaciation comprised three glacier advances 32,000 ± 2500 (Headley Tarn Advance), 19,100 ± 1600 (Blue Lake Advance), and 16,800 ± 1400 years ago (Mt. Twynam Advance). The Early Kosciuszko glaciation was the most extensive and the Late Kosciuszko advances were progressively less extensive. These periods of glaciation in the highlands correspond to episodes of periglacial activity and peaks in lake levels and river discharge at lower elevations in southeastern Australia. Glacier advances on the Kosciuszko Massif correlate with advances in Tasmania, South America, and New Zealand and are broadly representative of hemispheric climate changes during the last glacial cycle.
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Humlum, Ole, Hanne H. Cristiansen, Lis E. Mortensen, Finlay M. Stuart, and John O. Stone. "Weichselian Glaciation of the Faroe Islands." Bulletin of the Geological Society of Denmark 72 (February 23, 2023): 19–100. http://dx.doi.org/10.37570/bgsd-2023-72-02.
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This paper presents a new complete field mapping of glacial landscapes, landforms and sediments in the Faroe Islands, supplemented by observations from bathymetric maps of the Faroe Shelf. In addition, previous investigations of Quaternary and espe-cially the Weichselian glaciation of the archipelago are reviewed. New cosmogenic nuclide exposure ages indicate that the last extensive glaciation of the Faroe Islands occurred during the Late Weichselian, most likely during the Last Glacial Maximum (LGM; c. 26.5–19.0 cal. ka BP), although a Younger Dryas (c. 12.9–11.7 cal. ka BP) age cannot be entirely excluded. Geomorphological mapping provides a background for reconstructing the extent and type of the glaciation of the Faroe Islands. The reconstructed Weichselian glaciation appears to have had the character of an exten-sive valley glaciation, with several marine glacier termini. The present glaciation of southern Spitsbergen, Svalbard, represents a modern analogue of the reconstructed Weichselian glaciation in the Faroe Islands. The lack of raised coastal features in the Faroe Islands, also at protected sites, suggests that postglacial isostatic uplift was smaller than post-LGM eustatic sea level rise. Numerical glacier reconstructions carried out for different extents of the last extensive Faroese glaciation suggest that such limited postglacial isostatic crustal uplift requires that the Faroe Shelf was not extensively glaciated during the Late Weichselian, but it doubtless was so during at least one of the previous Quaternary glaciations.
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Fitzsimons, Sean J., and Eric A. Colhoun. "Pleistocene glaciation of the King Valley, Western Tasmania, Australia." Quaternary Research 36, no. 2 (1991): 135–56. http://dx.doi.org/10.1016/0033-5894(91)90022-w.
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AbstractAnalysis of the geomorphology, geology, and palynology of deposits in the King Valley permits the identification of four glaciations and two interglaciations and has led to a revision of the Pleistocene stratigraphy of the West Coast Range. The oldest late-Cenozoic deposits in the valley appear to predate glaciation, contain extinct pollen types, and are probably of late-Tertiary age. Overlying deposits of the Linda Glaciation show intense chemical weathering and have a reversed detrital remanent magnetization indicating deposition before 730,000 yr B.P. The highly weathered tills are conformably overlain by organic deposits of the Regency Interglaciation which show a transition from montane scrub rainforest to lowland temperate rainforest. Deposits formed during the later Moore Glaciation record advances of the King Glacier and glaciers from the West Coast Range. A pollen-bearing fluvial deposit records an interstade during this glaciation. On the basis of weathering rinds, amino acid dating, and palaeomagnetism the deposits are estimated to have formed between 730,000 and 390,000 yr B.P. The Moore Glaciation deposits are overlain by sediments of the Henty Glaciation which are believed to predate 130,000 yr B.P. These deposits record multiple advances of the King Glacier and the development of a large lake during an interstade. Deposits of the subsequent Pieman Interglaciation consist of organic fine sands and silts that record a lowland scrub rainforest. Deposits of the last (Margaret) glaciation are restricted to small areas in the northern part of the valley. Although the most recent ice advance culminated after 19,000 yr B.P., evidence of older deposits of the Margaret Glaciation suggests that an early last-glaciation ice advance may have occurred. When combined with earlier studies, the recent work in the King Valley has provided one of the more complete records of Pleistocene glaciation in the Southern Hemisphere. Comparison of the deposits with the record of glaciation in southern South America and Westland, New Zealand, suggests some similarities exist between pre-last-glaciation events and indicates that glacial events in Southern Hemisphere middle latitude areas were synchronous during the last glaciation.
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Duk-Rodkin, Alejandra, and Owen L. Hughes. "Age Relationships of Laurentide and Montane Glaciations, Mackenzie Mountains, Northwest Territories." Géographie physique et Quaternaire 45, no. 1 (2007): 79–90. http://dx.doi.org/10.7202/032847ar.
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ABSTRACT The Mackenzie Mountains were glaciated repeatedly by large valley glaciers that emanated from the Backbone Ranges, and by much smaller valley glaciers that emanated from peaks in the Canyon Ranges. During the Late Wisconsinan the Laurentide Ice Sheet reached its all-time maximum position. The ice sheet pressed against the Canyon Ranges and moved up major valleys causing the diversion of mountain waters and organizing a complex meltwater system that drained across mountain interfluve areas towards the northwest. Two ages of moraines deposited by montane glaciers occur widely in the Mackenzie Mountains. Near the mountain front certain of the older moraines have been truncated by the Laurentide Ice Sheet, and others have been incised by meltwater streams emanating from the Laurentide ice margin, indicating that these older moraines predate the maximum Laurentide advance. Locally, certain of the younger montane moraines breach moraines and other ice marginal features of the Laurentide maximum, indicating that the younger montane glaciation post-dated the Laurentide maximum. Some large montane glaciers extended out from the mountains to merge with the retreating Laurentide Ice Sheet. There are several localities that display the age relationships between montane and Laurentide glaciations such as Dark Rock Creek, Durkan-Lukas Valley, Little Bear River and Katherine Creek. The older of the local montane glaciations is correlated tentatively with Reid Glaciation (lllinoian?) of central Yukon, and the younger with the Late Wisconsinan McConnell Glaciation. The Laurentide Glaciation is correlated with Hungry Creek Glaciation of Bonnet Plume Depression, which probably culminated about 30,000 years ago or somewhat later.
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Fairburn, William A., and Mark D. Bateman. "Possible new evidence for Mid-Pleistocene glaciation in the Vale of Pickering, North Yorkshire, UK." Proceedings of the Yorkshire Geological Society 63, no. 4 (2021): pygs2020–019. http://dx.doi.org/10.1144/pygs2020-019.
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Whilst the Late Devensian glaciation (MIS2) of the Vale of Pickering is well-documented, earlier glaciations within it are not. A proposed limited glaciation in the Mid-Pleistocene, thought to be of Marine Isotope Stage 8 (MIS) age is not well constrained. This paper aims to obtain preliminary ages for two of the most prominent geomorphic features in the Vale of Pickering to see if they related to pre-Devensian glaciations. New luminescence dating by infra-red stimulation of feldspars from sand accumulations near the summit of Gallows Hill, part of the Wykeham Moraine, and from a section through poorly sorted fluvial sand and gravel on the flanks of the Hutton Buscel Terrace in Yedman Dale gave ages of 176 ± 14 ka and 156 ± 12 ka, respectively. Evidence suggests they represent a glacial incursion (MIS 6) into the Vale of Pickering blocking its eastern end and forming a pre-Devensian Glacial Lake Pickering. Whilst they could be older, this style of glaciation is very different to the limited plateau ice-field proposed for MIS 8 at the western end of the Vale of Pickering. Taken at face value, these preliminary ages suggest that the Vale of Pickering was partially glaciated in MIS 6 as part of a wider ice sheet and contemporary with the Saalian glaciation in Europe.
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Dortch, Jason M., Lewis A. Owen, and Marc W. Caffee. "Quaternary glaciation in the Nubra and Shyok valley confluence, northernmost Ladakh, India." Quaternary Research 74, no. 1 (2010): 132–44. http://dx.doi.org/10.1016/j.yqres.2010.04.013.
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AbstractThree glacial stages (Deshkit 1, Deshkit 2 and Dishkit 3 glacial stages) are identified in the Nubra and Shyok valleys in northernmost Ladakh, northwest India, on the basis of geomorphic field mapping, remote sensing, and 10Be terrestrial cosmogenic nuclide surface exposure dating. The glacial stages date to ∼ 45 ka (Deshkit 1 glacial stage), ∼ 81 ka (Deshkit 2 glacial stage) and ∼ 144 ka (Deshkit 3 glacial stage). A mean equilibrium line altitude depression of ∼ 290 m for the Deshkit 1 glacial stage was calculated using the area accumulation ratio, toe-to-headwall ratio, area–altitude, and area–altitude balance ratio methods. Comparison of glaciation in the Nubra and Shyok valleys with glaciations in the adjacent Central Karakoram of northern Pakistan and northern side of the Ladakh Range of northern India indicates that glaciation was synchronous on Milankovitch timescales across the region during MIS-6, but differed greatly in extent, with more extensive glaciation in the Karakoram than the morphostratigraphically equivalent glaciation on the northern slopes of the Ladakh Range. This highlights the strong contrast in the extent of glaciation across ranges in the Himalaya–Tibetan orogen, necessitating caution when correlating glacial successions within and between mountain ranges.
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Karabanov, Eugene B., Alexander A. Prokopenko, Douglas F. Williams, and Steven M. Colman. "Evidence from Lake Baikal for Siberian Glaciation during Oxygen-Isotope Substage 5d." Quaternary Research 50, no. 1 (1998): 46–55. http://dx.doi.org/10.1006/qres.1998.1980.
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The paleoclimatic record from bottom sediments of Lake Baikal (eastern Siberia) reveals new evidence for an abrupt and intense glaciation during the initial part of the last interglacial period (isotope substage 5d). This glaciation lasted about 12,000 yr from 117,000 to 105,000 yr B.P. according to correlation with the SPECMAP isotope chronology. Lithological and biogeochemical evidence of glaciation from Lake Baikal agrees with evidence for the advance of ice sheet in northwestern Siberia during this time period and also with cryogenic features within the strata of Kazantzevo soils in Southern Siberia. The severe 5d glaciation in Siberia was caused by dramatic cooling due to the decrease in solar insolation (as predicted by the model of insolation changes for northern Asia according to Milankovich theory) coupled with western atmospheric transport of moisture from the open areas of Northern Atlantic and Arctic seas (which became ice-free due to the intense warming during preceeding isotope substage 5e). Other marine and continental records show evidence for cooling during 5d, but not for intense glaciation. Late Pleistocene glaciations in the Northern Hemisphere may have begun in northwestern Siberia.
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Ward, Brent C., Jeffrey D. Bond, and John C. Gosse. "Evidence for a 55–50 ka (early Wisconsin) glaciation of the Cordilleran ice sheet, Yukon Territory, Canada." Quaternary Research 68, no. 1 (2007): 141–50. http://dx.doi.org/10.1016/j.yqres.2007.04.002.
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AbstractCosmogenic 10Be ages on boulders of 54–51 ka (n=4) on a penultimate Cordilleran ice sheet (CIS) drift confirm that Marine Oxygen Isotope Stage (MIS) 4 (early Wisconsin) glaciation was extensive in parts of Yukon Territory, the first confirmed evidence in the Canadian Cordillera. We name the glaciation inferred from the mapped and dated drift the Gladstone. These results are in apparent contrast to the MIS 6 (Illinoian) age of the penultimate Reid glaciation to the east in central Yukon but are equivalent to exposure ages on MIS 4 drift in Alaska. Contrasting penultimate ice extents in Yukon requires that different source areas of the northern CIS in Yukon responded differently to climatic forcing during glaciations. The variation in glacier extent for different source areas likely relates to variation in precipitation during glaciation, as the northern CIS was a precipitation-limited system. Causes for a variation in precipitation remain unclear but likely involve the style of precipitation delivery over the St. Elias Mountains possibly related to variations in the Aleutian low.
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DOTSENKO, Valeriy, and Ibragim KERIMOV. "ABOUT THE REASONS OF CLIMATE WARMING BASED ON STUDYING THE HISTORY OF QUATERNARY GLACIOSES OF THE CAUCASUS (ON THE EXAMPLE OF THE INTERDURCHIE TEREK AND THE ANDIAN KOISU)." Sustainable Development of Mountain Territories 12, no. 3 (2020): 461–71. http://dx.doi.org/10.21177/1998-4502-2020-12-3-461-471.
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The Greater Caucasus experienced repeated glaciation during the Quaternary (early, middle, upper Pleistocene, late Glacial, and late Holocene), which occurred under changing climatic conditions and differentiated tectonic movements. These glaciations, of course, are associated with changes in terrain, the formation of new deposits, transgressions and regressions of the Caspian Sea, changes in vegetation and soil types, so the problem of glaciation affects all earth Sciences to varying degrees. The study of Quaternary glaciation, especially Holocene glaciation, is currently relevant for understanding climate change. Against the background of significant climate fluctuations within the epochs of glaciation, there are smaller cooling phases that cause the temporary onset of glaciers. Short-term climate fluctuations are manifested in oscillations – minor fluctuations in the languages of glaciers. All this indicates that the climate undergoes significant changes in a short time, which are reflected in the morphosculpture of the terrain, the latest deposits and modern precipitation. Glaciation of the Greater Caucasus in the Prikazbeksky region reached its maximum in the middle Pleistocene,when glaciers went far into the Ossetian basin. All these traces have been preserved due to the lower capacity of the Chanty-Argun glacier and its fluvioglacial flow, which developed during the late Pleistocene epoch. Volcanic activity, especially active in the late Pliocene and continuing up to the present time, is associated with the late horn stage of development of the Caucasus. The formation of the Rukhs-Dzuar molass formation more than 2 km thick in the late Pleistocene in the Ossetian basin of the Tersky-Caspian flexure is associated with the activity of volcanoes in the Kazbek volcanic region. In the early Pleistocene, volcanic activity on the BC decreased significantly. The most intense outbreak of volcanism in the Kazbek and Elbrus volcanic regions occurred at the beginning of the late Pleistocene, which roughly coincided with the maximum phase of the late Pleistocene (Bezengian) glaciation. Then, in the second half of the late Pleistocene, volcanic activity was manifested on the mount Kazbek. The last outbreak of volcanic activity occurred in the Holocene no more than 2-3 thousand years ago. Fresh lavas are available on Elbrus, Kazbek, in the Terek valley near villages. Sioni and on the Kel volcanic plateau. Fumarolic activity still continues on Elbrus. Thus, in the Kazbek region, eruptions occurred from the late Pliocene to the late Holocene inclusive. Keywords: Pleistocene, Holocene, glaciation stages, nival-glacial processes, causes of glaciations, climate change, anthropogenic factors, natural factors, Earth degassing, magmatogenic degassing branch, seismotectonic degassing branch, greenhouse gases, newest geodynamics, volcanism, mud regimes, volcanism, methane hydrates, land degradation, water reclamation.
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Nielsen, Michael Houmark. "Extent and age of Middle and Late Pleistocene glaciations andperiglacial episodes in southern Jylland, Denmark." Bulletin of the Geological Society of Denmark 55 (February 23, 2007): 9–35. http://dx.doi.org/10.37570/bgsd-2007-55-02.
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New evidence on distribution and chronology of glaciations in southern Jylland is presented. Ten stratigraphic units including four till-formations have been identified in Middle- and Late Pleistocene sediment successions. The timing of successive glaciations and periglacial interludes based on luminescence dating is established for the past c. 200 kyr. The OSL-chronology predicts that deposition of Lillebælt Till (Late Saalian, Warthe Glaciation) occurred at 180-160 kyr. Deglaciation followed and barren periglacial environments existed until beginning of the Eemian. Periglacial conditions were restored c. 115 kyr ago and lasted well into the Middle Weichselian. Expansion of the Scandinavian Ice Sheet through the Baltic depression into southern Jylland caused deposition of Ristinge Klint Till (Ristinge Glaciation) c. 55–50 kyr ago. Glaciers flowed westwards beyond the Main Stationary Line (MSL) and may have terminated along ice showed ridges in the periglacially smoothed landscape east of the present North Sea coast. This traditionally named “Old Baltic”glaciation is now recognized elsewhere in the circum Baltic region besides Denmark. Deglaciation was succeeded by periglacial environments with cryoturbation, ice wedge growth, formation of wind abrasion pavements and low arctic habitats. Approaching the global glacio-eustatic low stand of the Last Glacial Maximum increased cooling and enhanced down slope creep caused widespread solifluction. In a sequence of Late Weichselian glacier advances, Mid Danish Till, East Jylland Till and Bælthav Till was deposited under progressing deglaciation between 25 and 18 kyr ago. Retarded melting of dead ice from the Ristinge Glaciation formed thermo karst depressions on the surfaceof outwash plains in front of MSL.
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Matthews, John V., Charles E. Schweger, and Owen L. Hughes. "Plant and Insect Fossils from the Mayo Indian Village Section (Central Yukon): New Data on Middle Wisconsinan Environments and Glaciation." Géographie physique et Quaternaire 44, no. 1 (2007): 15–26. http://dx.doi.org/10.7202/032794ar.
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RÉSUMÉ La coupe du village indien de Mayo renferme le Till de Mayo, témoin de la Glaciation de McConnell datant du Wisconsinien, sous lequel se trouvent des sédiments fluviatiles comprenant des matériaux organodétritiques rares. Les datations au 14C du till et des sédiments sous-jacents obtenues antérieurement n'avaient pas permis de dater avec précision l'âge de la Glaciation de McConnell. La nouvelle date de 29,6 ka obtenue par accélérateur sur des graines de Corispermum hyssopifolium provenant des dépôts sous-jacents au till indique que la Glaciation de McConnell date probablement du Wisconsinien supérieur et qu'elle correspond aux glaciations de Kluane (Kluane Lake) et de McCauley (région de Snag-Klutan) et à la glaciation représentée par le "Till D" dans la coupe de Tom Creek (Liard Plain). À partir de cette conclusion et grâce à une nouvelle datation sur le tephra de Old Crow, on peut croire que les glaciations de Reid, de Mirror Creek et probablement de Shakwak sont d'âge illinoien. Les fossiles de végétaux (pollen et graines) et d'insectes trouvés dans les sédiments organodétritiques associés à la date de 29.6 ka BP témoignent d'un milieu en grande partie dépourvu d'arbres. Même si les végétaux caractéristiques du bas Arctique comme les Éricacées, l'aulne et le bouleau arbustif sont rares ou absents, le pollen et les macrofossiles laissent entrevoir un climat qui n'était pas plus froid que le climat actuel de la toundra du bas Arctique, mais probablement plus sec. Les épinettes ont peut-être survécu dans la région mais seulement sous forme de bosquets et non de forêt riparienne.
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Glushkova, O. Yu, та V. N. Smirnov. "Реконструкция масштабов и морфологических особенностей плейстоценовых оледенений на Северо-Востоке России". Bulletin of the North-East Science Center, № 2 (30 червня 2021): 50–67. http://dx.doi.org/10.34078/1814-0998-2021-2-50-67.
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Based on the currently available data, it has been established that the earliest glaciations occurred in the Late Eopleistocene and at the end of the Early Neopleistocene. They had local distribution in the most uplifted parts of the Chersky Range. Their traces are presented in the form of moraines enclosed in sediments of intermontain depressions. Glacial forms of this age have not been identified in the relief of mountains and plains in the North-East of Russia. The Middle Neopleistocene glaciation was the largest, both in area and length of individual glaciers. It was mountain-valley and reticulated; in some areas, mountain-cover. Its time coincides with the stage of activation of the ascending neotectonic movements in the Middle Neopleistocene. Traces of the last two Late Neopleistocene glaciations are well expressed in the relief in widespread exaration, moraine, and fluvioglacial complexes. The first Late Neopleistocene glaciation (Zyryan) was significantly inferior to the one occurred in the Middle Neopleistocene, in all parameters, but it also left large amphitheaters of terminal moraines in the foothill belts. Glacial complexes of the last Late Neopleistocene glaciation are widespread in areas 2-3 times smaller than the previous one and, as a rule, are located within its contours.
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Gschwentner, Philipp, Hanns Kerschner, and Christoph Spötl. "Late Glacial ice advance in the Kellerjoch region near Schwaz (Tyrol, Eastern Alps)." Austrian Journal of Earth Sciences 113, no. 1-2 (2020): 211–27. http://dx.doi.org/10.17738/ajes.2020.0013.
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Abstract The Kellerjoch forms a small isolated massif at the northernmost rim of the central Eastern Alps of Tyrol and shows a number of geomorphological features of glacial and periglacial origin. Mapping yields evidence of two local glaciations postdating the Last Glacial Maximum. Using a simple glaciological approach the palaeoglaciers related to these events were reconstructed. The older glaciation yields an equilibrium line altitude (ELA) ranging from 1660 m for the maximum extent to 1800 m a.s.l. for the innermost moraine. For the younger glaciation, ELAs were reconstructed at 1905 m and 1980 m (depending on the reconstruction) for the Kellerjoch palaeoglacier 2, as well as 1870 m and 2060 m a.s.l. for the Proxen palaeoglacier and the Gart palaeoglacier, respectively. A comparison with published data from the Eastern Alps shows that the older glaciation in the Kellerjoch region likely corresponds to the Gschnitz stadial. Low basal shear stresses of the glacier tongues point towards a cold and dry climate, similar to the reconstruction for the Gschnitz type locality at Trins. The younger glaciation cannot unambiguously be assigned to a specific Late Glacial ice advance, but a Younger Dryas age is a distinct possibility.
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Schaller, Sebastian, Marius W. Buechi, Bennet Schuster, and Flavio S. Anselmetti. "Drilling into a deep buried valley (ICDP DOVE): a 252 m long sediment succession from a glacial overdeepening in northwestern Switzerland." Scientific Drilling 32 (October 26, 2023): 27–42. http://dx.doi.org/10.5194/sd-32-27-2023.
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Abstract. The modern Alpine landscape and its foreland were strongly impacted by the numerous glacier advance and retreat cycles during the Middle-to-Late Pleistocene. Due to the overall erosive character of each glaciation cycle, however, direct traces of older glaciations tend to be poorly preserved within the formerly glaciated domains of the pan-Alpine area. Nevertheless, sediments of older glaciations may occur hidden under the modern surface in buried glacially overdeepened troughs that reach below the normal level of fluvial erosion (fluvial base level). These sedimentary archives, partly dating back to the Middle Pleistocene period, are of great scientific value for reconstructing the timing and extent of extensive Alpine glaciation, paleoclimate, and paleoenvironmental changes in the past and help to better understand ongoing and future changes in the pan-Alpine area. Therefore, the International Continental Scientific Drilling Program (ICDP) project DOVE (Drilling Overdeepened Alpine Valleys) targets several of these glacial overdeepened sedimentary basins to recover their sedimentary infills. In the frame of the DOVE project, a 252 m long drill core of unconsolidated Quaternary sediments was recovered in northern Switzerland from an over 300 m deep glacially overdeepened structure (“Basadingen Trough”) formed by the former Rhine Glacier lobe system. The recovered sedimentary succession was divided into three stratigraphic units on the basis of lithological and petrophysical characteristics. The lowest unit, deposited below the fluvial base level, consists of an over 200 m thick succession of glacial to (glacio)lacustrine sediments and contains remains of possibly two glaciation cycles. Overlying this lowermost succession, an ∼ 37 m thick fluvial-to-glaciofluvial gravel deposit occurs, which correlates to a locally outcropping Middle Pleistocene formation (“Buechberg Gravel Complex”). The sediment succession is capped by an ∼ 11 m thick diamictic succession interpreted as the subglacial till from the later extensive glaciation, including the regional glaciation during the Last Glacial Maximum. The recovered sediment succession thus supports the proposed multi-phase origin of trough formation and its infill.
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Ryder, June M., and Denny Maynard. "The Cordilleran Ice Sheet in Northern British Colombia." Géographie physique et Quaternaire 45, no. 3 (2007): 355–63. http://dx.doi.org/10.7202/032881ar.
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ABSTRACT Dates from lavas associated with tills and erratics indicate that ice-sheet glaciations occurred between 4 and 0.6 Ma BP. The few radiocarbon dates that are available suggest that the chronology of the Late Wisconsinan (Fraser Glaciation) ice sheet of northern British Columbia was similar to that of the southern part of the province. During what may have been a long, early phase of this glaciation, Glacial Lake Stikine was dammed by advancing valley glaciers in the Coast Mountains, and alpine glaciers developed on the intermontane plateau. At the climax of Fraser Glaciation, ice-flow patterns were dominated by outflow from a névé centred over the northern Skeena Mountains. Déglaciation occurred partly by frontal retreat of ice tongues and partly by downwasting of stagnant ice. Recessional moraines mark one or more resurgences or stillstands of the ice margin. During déglaciation, Stikine River valley was occupied by an active outlet glacier and a major subglacial drainage system.
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Van Vliet-Lanoë, Brigitte. "The autocyclic nature of glaciations." Bulletin de la Société Géologique de France 178, no. 4 (2007): 247–62. http://dx.doi.org/10.2113/gssgfbull.178.4.247.
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Abstract The maximum extent of a glaciation is often confused with the coldest part of a glaciation. During the Last Glaciation, the date of the Last Ice Maximum Extent (LIME) is diachronous very early at high latitudes close to the traditional date in the intertropical mountains. The classical Last Glacial Maximum (LGM) never corresponds to the LIME with the exception of intertropical regions. At middle and high latitudes advances of the LGM only correspond to surges of a lately thickened ice sheet. The same structure also exists at the level of the entire Cenozoic of a whole glaciation or of much shorter events as the scale of a whole Bond’s cycle. For each type of event the reactional sequence is autocyclic: a rapid warming ends a slowly cooling trend due to the higher susceptibility of lower latitudes to external forcing (orbital and solar activity). Moisture supply from an ice-free ocean is the sine qua non to build glaciers. The syngenetic extent of the cold desert toward the equator is the limiting factor for ice volume: when glaciations develop in intertropical mountains with the development of sea ice in the polar zones, glaciers recede by precipitation starvation with restricted sedimentation. During a glacial era in parallel with ice cap building, the progressive sea level lowering and the subsequent enhanced aridity counterbalance the generalization of a world-scale glaciation. This concept could be also valid for the Neoproterozoic Glacial era and should probably invalidate the snowball hypothesis.
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Roed, Murray A., René W. Barendregt, Jeff A. Benowitz, et al. "Evidence for an Early Pleistocene glaciation in the Okanagan Valley, southern British Columbia." Canadian Journal of Earth Sciences 51, no. 2 (2014): 125–41. http://dx.doi.org/10.1139/cjes-2013-0106.
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Depositional evidence of Early Pleistocene glaciations in British Columbia are documented at only a few sites. Near Kelowna, in southern British Columbia, a construction project exposed glacial sediments beneath Lambly Creek Basalt, providing a minimum age for this glaciation. The basalt is composed of a number of flows yielding ages that range from 0.76 ± 0.11 to 1.5 ± 0.1 Ma. The sediments consist of a diamicton, interpreted to be till, up to 3 m thick mantled by a weakly developed paleosol. The diamicton is underlain by fluvial sands up to 5 m thick, in places revealing injection features, and minor faulting. A unit of stratified gravel underlain by grey clay is inferred to underlie the exposed sediments, based on nearby outcrops and excavations. Sediments and overlying basalts are normally magnetized and are assigned to the Jaramillo normal subchron (1.069–0.987 Ma). The till is here referred to as the Westbank First Nation Till. It is Early Pleistocene in age and represents the earliest evidence of glaciation in the Okanagan Valley. Stone fabric analysis and clast lithologies suggest that ice movement was from northwest to southeast, and is here referred to as the West Kelowna Advance; we infer that this advance was part of a larger regional glaciation. Other Early Pleistocene glaciations in the Cordillera are briefly reviewed.
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Huston, Matt M., Julie Brigham-Grette, and David M. Hopkins. "Paleogeographic Significance of Middle Pleistocene Glaciomarine Deposits on Baldwin Peninsula, Northwest Alaska." Annals of Glaciology 14 (1990): 111–14. http://dx.doi.org/10.3189/s0260305500008375.
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Baldwin Peninsula, northwest Alaska, is a middle Pleistocene push-moraine complex composed of marine, fluvial, and glaciogenic sediments. The peninsula was formed by three ice lobes emanating from the De Long and Baird mountains and the Selawik Lowlands in the southwest Brooks Range during the Anaktuvuk River glaciation. This glaciation was nearly an order of magnitude more areally extensive than late Pleistocene glaciations in the same region and occurred c. 500 to 600 ka B.P. based on paleomagnetism, and amino-stratigraphic and morphostratigraphic correlations with other numerically-dated northwest Alaskan deposits.Extensive deposits of massive and laminated clayey silt with striated, faceted stones indicate that local sea level was high as glacial ice reached its maximum extent. Glacio-isostasy does not seem to have been important in maintaining a high relative sea level; therefore we infer that eustatic sea level remained high during ice advance. For this to occur, high latitude glaciation must have preceded the build-up of ice in lower latitudes. The source of moisture for such massive glaciation may have come from submerged Bering and Chukchi shelves, enhanced flow of North Pacific/southern Bering Sea winter storms, reduced intensity of the winter Arctic High, or a combination thereof.
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Huston, Matt M., Julie Brigham-Grette, and David M. Hopkins. "Paleogeographic Significance of Middle Pleistocene Glaciomarine Deposits on Baldwin Peninsula, Northwest Alaska." Annals of Glaciology 14 (1990): 111–14. http://dx.doi.org/10.1017/s0260305500008375.
Full textAbstract:
Baldwin Peninsula, northwest Alaska, is a middle Pleistocene push-moraine complex composed of marine, fluvial, and glaciogenic sediments. The peninsula was formed by three ice lobes emanating from the De Long and Baird mountains and the Selawik Lowlands in the southwest Brooks Range during the Anaktuvuk River glaciation. This glaciation was nearly an order of magnitude more areally extensive than late Pleistocene glaciations in the same region and occurred c. 500 to 600 ka B.P. based on paleomagnetism, and amino-stratigraphic and morphostratigraphic correlations with other numerically-dated northwest Alaskan deposits. Extensive deposits of massive and laminated clayey silt with striated, faceted stones indicate that local sea level was high as glacial ice reached its maximum extent. Glacio-isostasy does not seem to have been important in maintaining a high relative sea level; therefore we infer that eustatic sea level remained high during ice advance. For this to occur, high latitude glaciation must have preceded the build-up of ice in lower latitudes. The source of moisture for such massive glaciation may have come from submerged Bering and Chukchi shelves, enhanced flow of North Pacific/southern Bering Sea winter storms, reduced intensity of the winter Arctic High, or a combination thereof.
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Burbank, Douglas W., and Kang Jian Cheng. "Relative dating of Quaternary moraines, Rongbuk valley, Mount Everest, Tibet: Implications for an ice sheet on the Tibetan Plateau." Quaternary Research 36, no. 1 (1991): 1–18. http://dx.doi.org/10.1016/0033-5894(91)90013-u.
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AbstractRelative-dating studies applied to high-altitude moraines (5000–5500 m) in the Rongbuk valley on the northern flank of Mt. Everest reveal strong contrasts in the weathering characteristics of the boulders exposed along moraine crests. These differences serve to define three intervals of major Pleistocene glaciation that, on the basis of the degree of weathering, are interpreted to extend back to at least the penultimate glaciation and probably encompass at least one still older glaciation. Either interpretation indicates that some of these moraines are considerably older than their previously assigned ages. The magnitude of equilibrium-line lowering during Neoglacial and late Pleistocene times is calculated to be ca. 50–100 and 350–450 m, respectively. The data described here are incompatible with the recently proposed model (Kuhle, 1987) for large-scale ice-sheet development on the Tibetan Plateau. The reconstructed equilibrium-line lowering in the Everest region is only 30% of that cited in the ice-sheet model. Moreover, the flow patterns and geometry of the former Rongbuk glaciers are in opposition to those proposed by the model. Based on the data from the Everest region, it appears that valley glaciation, rather than ice-sheet growth, characterized the southern margin of the Tibetan Plateau during the middle and late Pleistocene glaciations.
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Jackson Jr, L. E., R. W. Barendregt, J. Baker, and E. Irving. "Early Pleistocene volcanism and glaciation in central Yukon: a new chronology from field studies and paleomagnetism." Canadian Journal of Earth Sciences 33, no. 6 (1996): 904–16. http://dx.doi.org/10.1139/e96-068.
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The paleomagnetism of the Selkirk Volcanics and nearby stratified Pleistocene sediments was investigated to resolve the chronology of Early Pleistocene glaciations in central Yukon. Radiometric dates on these low-K basalts have proven to be erroneously old. Most sampled sediments and all basalts accurately record the paleofield and true reversals. The valley-filling phase of the Selkirk Volcanics was in part coeval with the younger pre-Reid glaciation. It was erupted during the Matuyama Chron, either post-Cobb Mountain Subchron or post-Jaramillo Subchron, over a period too brief to average secular variation. The older pre-Reid glaciation occurred after ca. 1.60 Ma and prior to the eruption of the Fort Selkirk tephra (pre-Jaramillo or pre-Cobb Mountain). Sediments investigated at Revenue Creek and Braden's Canyon are normally magnetized. The assigned Brunhes age is compatible with their occurrence in valleys that were cut or deepened sometime after the pre-Reid glaciations.
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Stauch, Georg, and Frank Lehmkuhl. "Quaternary glaciations in the Verkhoyansk Mountains, Northeast Siberia." Quaternary Research 74, no. 1 (2010): 145–55. http://dx.doi.org/10.1016/j.yqres.2010.04.003.
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AbstractGeomorphological mapping revealed five terminal moraines in the central Verkhoyansk Mountains. The youngest terminal moraine (I) was formed at least 50 ka ago according to new IRSL (infrared optically stimulated luminescence) dates. Older terminal moraines in the western foreland of the mountains are much more extensive in size. Although the smallest of these older moraines, moraine II, has not been dated, moraine III is 80 to 90 ka, moraine IV is 100 to 120 ka, and the outermost moraine V was deposited around 135 ka. This glaciation history is comparable to that of the Barents and Kara ice sheet and partly to that of the Polar Ural Mountains regarding the timing of the glaciations. However, no glaciation occurred during the global last glacial maximum (MIS 2). Based on cirque orientation and different glacier extent on the eastern and western flanks of the Verkhoyansk Mountains, local glaciations are mainly controlled by moisture transport from the west across the Eurasian continent. Thus glaciations in the Verkhoyansk Mountains not only express local climate changes but also are strongly influenced by the extent of the Eurasian ice sheets.
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Guattari, Félix. "Glaciation." Lignes 4, no. 3 (1988): 125. http://dx.doi.org/10.3917/lignes0.004.0125.
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Locke, William W. "The late Quaternary geomorphic and paleoclimatic history of the Cape Dyer area, easternmost Baffin Island, N.W.T." Canadian Journal of Earth Sciences 24, no. 6 (1987): 1185–98. http://dx.doi.org/10.1139/e87-114.
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The Cape Dyer area of easternmost Baffin Island was isolated from the Laurentide Ice Sheet by the fiords of Cumberland Peninsula. Accordingly, the glacial chronology at Cape Dyer is that of local ice only and is indicative of the local climate throughout the late Quaternary. Six drift units, representing three periods of restricted glaciation and three of expanded glaciation, are present. Beyond the most distal drift is an area that has not been modified by glaciation.The expanded glaciations were dated through correlation on the bases of moraine morphology, soil development, and amino-acid racemization in marine mollusc shells incorporated in the drifts. No maximum age can be assigned to the earliest glaciation in the Cape Dyer area, but the last major glacial advance occurred about 70 000 years BP. The presence of extensive glaciofluvial features, faunal indicators of warm ocean water, and rapid soil development indicate that major glaciations of the Cape Dyer area accompanied winters warmer than at present but summers sufficiently cool to allow ice advance.The restricted ice advances were dated through correlation on the bases of moraine morphology, soil development, and lichen cover to the period between 9000 years BP and the present. They indicate ice extent similar to or less than at present throughout the past 60 000 years, in response to climatic conditions that were colder and dryer than the present until 9000 years BP, then slightly warmer than the present.Correlation with indicators of hemispheric and global climate indicates both in-phase and out-of-phase relationships. Glaciations at Cape Dyer are in phase with periods of high accumulation on Arctic ice caps, ice rafting of sediment in the Labrador Sea, and computed summer-insolation minima – winter-insolation maxima at 65°N latitude. This is as would be expected given the climatic interpretations of the drifts. Glaciation of the Cape Dyer area is out of phase with global ice volume as indicated by oxygen isotopes, suggesting the Antarctic dry valleys as a modem climatic analog for the Pleistocene eastern Canadian Arctic. The record of ice extent, climatic interpretations, and proposed model for climatic change are in agreement with most previously published reconstructions.
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Barendregt, R. W., J. S. Vincent, E. Irving, and J. Baker. "Magnetostratigraphy of Quaternary and late Tertiary sediments on Banks Island, Canadian Arctic Archipelago." Canadian Journal of Earth Sciences 35, no. 2 (1998): 147–61. http://dx.doi.org/10.1139/e97-094.
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Sediments approximately 50 m thick from Banks Island (Canadian Arctic Archipelago) contain one of the longest terrestrial records of Pleistocene climate changes in North America. Samples have been obtained from 126 horizons distributed among four localitites, of which 116 horizons yielded acceptable paleomagnetic data. In sediments of the Matuyama Reversed Zone, there are recorded at least two and possibly as many as five full continental glaciations, two interglacial intervals, and a nonglacial interval at the beginning which is considered preglacial. Subzones attributable to the Olduvai and Jaramillo are present within the Matuyama Reversed Zone. The Brunhes Normal Zone records three full continental glaciations and three interglaciations. The Brunhes-Matuyama boundary occurs within interglacial deposits. The preglacial Worth Point Formation records a climate milder than today, and cooler than that of the late Tertiary. Based on floral, faunal, stratigraphic, and paleomagnetic constraints, a normal polarity sequence in the Worth Point Formation is assigned to the Olduvai normal polarity subzone (1.95-1.77 Ma). The earliest direct evidence of glaciation on Banks Island occurs in sediments that postdate the Worth Point Formation ( <<1.77 Ma). Consequently, in the western Canadian Arctic, the first continental glaciation postdated the first glaciation in the Canadian Cordillera (2.6 Ma) by at least a million years. The overall mean direction of the Quaternary geomagnetic field in Banks Island does not differ significantly from the geocentric axial dipole field, and these sediments contain no inclination error.
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Briner, Jason P., and Darrell S. Kaufman. "Late Pleistocene Glaciation of the Southwestern Ahklun Mountains, Alaska." Quaternary Research 53, no. 1 (2000): 13–22. http://dx.doi.org/10.1006/qres.1999.2088.
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AbstractGlacial deposits in the southwestern Ahklun Mountains, southwestern Alaska, record two major glacier advances during the late Pleistocene. The Arolik Lake and Klak Creek glaciations took place during the early and late Wisconsin, respectively. During the Arolik Lake glaciation, outlet glaciers emanated from an ice cap centered over the central portion of the Ahklun Mountains and expanded beyond the present coast. During the Klak Creek glaciation, ice-cap outlet glaciers terminated ∼60 km upvalley from Arolik Lake moraines. The area also supported numerous alpine glaciers that expanded from small massifs. During both episodes of glaciation, these alpine glaciers apparently reached their maximum positions sometime after the retreat of the ice-cap outlet glaciers. Equilibrium-line altitudes for reconstructed alpine glaciers of the Klak Creek glaciation average ∼390 ± 100 m elevation in the western Ahklun Mountains, which is at most 500 m, and possibly only 200 m, below the estimated modern equilibrium-line altitude. The maximum late Pleistocene advance in the southwestern Ahklun Mountains occurred during the early Wisconsin, similar to advances elsewhere in western Alaska, but in contrast to the isotopic signal in the deep-sea record of global ice volume. The restricted extent of Klak Creek glaciers might reflect the increased distance to the Bering Sea resulting from eustatic sea-level regression and decreased evaporation resulting from lower sea-surface temperatures and increased sea-ice extent.
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Fulton, R. J., E. Irving, and P. M. Wheadon. "Stratigraphy and paleomagnetism of Brunhes and Matuyama (>790 ka) Quaternary deposits at Merritt, British Columbia." Canadian Journal of Earth Sciences 29, no. 1 (1992): 76–92. http://dx.doi.org/10.1139/e92-009.
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A succession of Quaternary deposits in the Merritt basin of south-central British Columbia contains evidence for four glaciations and two interglaciations. Paleomagnetic signatures in these sediments are of three types: normal polarity, proposed to have been acquired during the Brunhes Normal Polarity Chron; reversed polarity, proposed to have been acquired during the Matuyama Reversed Polarity Chron; and reversed polarity (Matuyama age) all but obscured by a normally magnetized overprint (Brunhes age).Reversely magnetized deposits at the base of the succession include glacial lacustrine deposits, interpreted as representing two different glaciations, and a paleosol and a succession of nonglacial sediments, which are evidence of two interglaciations. As the reversed polarity of these deposits is proposed to have been acquired during the Matuyama Reversed Polarity Chron, they are older than 790 ka.Normally magnetized deposits, which make up the rest of the succession, contain evidence for only two glaciations, but traces of other glaciations may have been removed during the erosion interval encompassed by a major unconformity that underlies deposits of the last glaciation. All are referred to the Brunhes Normal Polarity Zone. In addition to these glacial and interglacial deposits, a series of normally magnetized Quaternary basalt flows forms a bench 90 m above the floor of the basin. These basalts were extruded after 790 ka but before the penultimate glaciation.
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Hughes, Philip D., Philip L. Gibbard, and Jürgen Ehlers. "The “missing glaciations” of the Middle Pleistocene." Quaternary Research 96 (February 4, 2020): 161–83. http://dx.doi.org/10.1017/qua.2019.76.
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AbstractGlobal glaciations have varied in size and magnitude since the Early–Middle Pleistocene transition (~773 ka), despite the apparent regular and high-amplitude 100 ka pacing of glacial–interglacial cycles recorded in marine isotope records. The evidence on land indicates that patterns of glaciation varied dramatically between different glacial–interglacial cycles. For example, Marine Isotope Stages (MIS) 8, 10, and 14 are all noticeably absent from many terrestrial glacial records in North America and Europe. However, globally, the patterns are more complicated, with major glaciations recorded in MIS 8 in Asia and in parts of the Southern Hemisphere, such as Patagonia, for example. This spatial variability in glaciation between glacial–interglacial cycles is likely to be driven by ice volume changes in the West Antarctic Ice Sheet and associated interhemispheric connections through ocean–atmosphere circulatory changes. The weak global glacial imprint in some glacial–interglacial cycles is related to the pattern of global ice buildup. This is caused by feedback mechanisms within glacial systems themselves that partly result from long-term orbital changes driven by eccentricity.
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Dieleman, Catharina, Marcus Christl, Christof Vockenhuber, Philip Gautschi, Hans Rudolf Graf, and Naki Akçar. "Age of the Most Extensive Glaciation in the Alps." Geosciences 12, no. 1 (2022): 39. http://dx.doi.org/10.3390/geosciences12010039.
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Previous research suggested that the Alpine glaciers of the Northern Swiss Foreland reached their maximum extensive position during the Middle Pleistocene. Relict tills and glaciofluvial deposits, attributed to the Most Extensive Glaciation (MEG), have been found only beyond the extents of the Last Glacial Maximum (LGM). Traditionally, these sediments have been correlated to the Riss glaciation sensu Penck and Brückner and have been morphostratigraphically classified as the Higher Terrace (HT) deposits. The age of the MEG glaciation was originally proposed to be intermediate to the Brunhes/Matuyama transition (780 ka) and the Marine Isotope Stage 6 (191 ka). In this study, we focused on the glacial deposits in Möhlin (Canton of Aargau, Switzerland), in order to constrain the age of the MEG. The sediments from these deposits were analyzed to determine the provenance and depositional environments. We applied isochron-burial dating, with cosmogenic 10Be and 26Al, to the till layer in the Bünten gravel pit near Möhlin. Our results indicate that a glacier of Alpine origin reached its most extensive position during the Middle Pleistocene (500 ± 100 ka). The age of the MEG thus appears to be synchronous with the most extensive glaciations in the northern hemisphere.
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Miara, Stefan, and Konrad Rogner. "Die glazifluvialen Sedimente im unteren Günztal (Bayerisch Schwaben/ Deutschland) nach morpho- und pedostratigraphischen Befunden sowie TL-Daten." E&G Quaternary Science Journal 46, no. 1 (1996): 32–47. http://dx.doi.org/10.3285/eg.46.1.03.
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Abstract. Until now in the lower valley of the river "Günz" the glaciofluvial gravel deposits were interpreted as an accumulation of the same glaciation (Riss). But the result of the stratigraphic investigation of loess cover sediments and glaciofluvial gravel layers - in connection with TL (Thermoluminescence)-datings - show that a mindelian gravel body lies beside the gravel deposits of the rissian upper high-terrace. The comparison of both subfaces of the gravel layers demonstrate that the older mindelian gravel deposits can be found on a higher level. Moreover, it is possible to connect the subface of the mindelian gravel with the subface of the "Grönenbach-Schwaighausener" gravel (it is the mindelian gravel of A. PENCK'S classical subdivision of the Ice Age with four glaciations in the area of Memmingen) in the south of the "Iller-Lech”-region. Furthermore, the stratigraphie division of the aeolian cover sediments at the localities of "Autenried" and "Günzburg" indicates the different ages of both gravel terraces (rissian and mindelian age). In that case the development of both gravel terraces do not belong to the same glaciation; they represent the main gravel deposits of two different glaciation periods.
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Ramadhin, Christine, and Chuixiang Yi. "ESD Ideas: Why are glaciations slower than deglaciations?" Earth System Dynamics 11, no. 1 (2020): 13–16. http://dx.doi.org/10.5194/esd-11-13-2020.
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Abstract. The Earth's climate during the Quaternary is dominated by short warm interglacials and longer cold glaciations paced by external forcings such as changes in insolation. Although not observed in the solar radiation changes, the time series of the cycles display asymmetry since transitions to full glacial conditions are slower than the termination of glaciations. Here an idea is proposed for the slower transition by identifying and describing two negative sea ice feedbacks dominant during the glaciation process that could serve as a control on the intermediate stage and decrease the pace of the process.
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Huybers, P., and P. Molnar. "Tropical cooling and the onset of North American glaciation." Climate of the Past 3, no. 3 (2007): 549–57. http://dx.doi.org/10.5194/cp-3-549-2007.
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Abstract. We offer a test of the idea that gradual cooling in the eastern tropical Pacific led to cooling of North America and the initiation of glaciation ~3 Myr ago. Using modern climate data we estimate how warming of the eastern tropical Pacific affects North American temperature and ice-ablation. Assuming that the modern relationship holds over the past millions of years, a ~4°C warmer eastern tropical Pacific between 3–5 Ma would increase ablation in northern North America by approximately two meters per year. By comparison, a similar estimate of the ablation response to variations in Earth's obliquity gives less than half the magnitude of the tropically-induced change. Considering that variations in Earth's obliquity appear sufficient to initiate glaciations between ~1–3 Ma, we infer that the warmer eastern equatorial Pacific prior to 3 Ma suffices to preclude glaciation.
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Huybers, P., and P. Molnar. "Tropical cooling and the onset of North American glaciation." Climate of the Past Discussions 3, no. 3 (2007): 771–89. http://dx.doi.org/10.5194/cpd-3-771-2007.
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Abstract. We offer a test of the idea that gradual cooling in the eastern tropical Pacific led to cooling of North America and the initiation of glaciation ~3 Myr ago. Using modern climate data we estimate how warming of the eastern tropical Pacific affects North American temperature and ice-ablation. Assuming that the modern relationship holds over the past millions of years, an eastern tropical Pacific warmer by ~4° between 3–5 Ma would increase ablation in northern North America by approximately two meters per year. By comparison, a similar estimate of the ablation response to variations in Earth's obliquity gives less than half the magnitude of the tropically-induced change. Considering that variations in Earth's obliquity appear sufficient to initiate glaciations between ~1–3 Ma, we infer that the warmer eastern equatorial Pacific prior to 3 Ma suffices to preclude glaciation.
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Tidey, Emily J., and Christina L. Hulbe. "Bathymetry and glacial geomorphology in the sub-Antarctic Auckland Islands." Antarctic Science 30, no. 6 (2018): 357–70. http://dx.doi.org/10.1017/s0954102018000342.
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AbstractNew high-resolution multibeam swath bathymetry along the east coast of the Auckland Islands is combined with subaerial topography and evaluated in the context of Quaternary glaciation of the islands. The marine geomorphology represents a mixture of past and current processes so that submerged glacial features are more evident in some areas than others. Fjords in the central and southern parts of the coastline are characterized by well-preserved terminal moraines and other glacial features while fjords to the north tend to have more subdued glacial features and a smoother seabed. This is the farthest north record yet established of extensive sub-Antarctic glaciation, relative to the position of the modern sub-Antarctic and Polar Front. This is the first analysis of detailed sea floor geomorphology in the area and provides a starting point for new studies of paleoclimate and past glaciations.
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Ou, Hsien-Wang. "Tropical Glaciation and Glacio-Epochs: Their Tectonic Origin in Paleogeography." Climate 13, no. 1 (2025): 9. https://doi.org/10.3390/cli13010009.
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Precambrian tropical glaciation is an enigma of Earth’s climate. Overlooking fundamental difference of land/sea icelines, it was equated with a global frozen ocean, which is at odds with the sedimentary evidence of an active hydrological cycle, and its genesis via the runaway ice–albedo feedback conflicts with the mostly ice-free Proterozoic when its trigger threshold was well exceeded by the dimmer sun. In view of these shortfalls, I put forth two key hypotheses of the tropical glaciation: first, if seeded by mountain glaciers, the land ice would advance on sea level to be halted by above-freezing summer temperature, which thus abuts an open cozonal ocean; second, a tropical supercontinent would block the brighter tropical sun to cause the required cooling. To test these hypotheses, I formulate a minimal tropical/polar box model to examine the temperature response to a varying tropical land area and show that tropical glaciation is indeed plausible when the landmass is concentrated in the tropics despite uncertain model parameters. In addition, given the chronology of paleogeography, the model may explain the observed deep time climate to provide a unified account of the faint young Sun paradox, Precambrian tropical glaciations, and Phanerozoic glacio-epochs, reinforcing, therefore, the uniformitarian principle.
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Bell, M., and E. P. Laine. "Erosion of the Laurentide Region of North America by Glacial and Glaciofluvial Processes." Quaternary Research 23, no. 2 (1985): 154–74. http://dx.doi.org/10.1016/0033-5894(85)90026-2.
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Collection of seismic reflection data from continental margins and ocean basins surrounding North America makes it possible to estimate the amount of material eroded from the area formerly covered by Laurentide ice sheets since major glaciation began in North America. A minimum estimate is made of 1.62 × 106 km3, or an average 120 m of rock physically eroded from the Laurentide region. This figure is an order of magnitude higher than earlier estimates based on the volume of glacial drift, Cenozoic marine sediments, and modern sediment loads of rivers. Most of the sediment produced during Laurentide glaciation has already been transported to the oceans. The importance of continental glaciation as a geomorphic agency in North America may have to be reevaluated. Evidence from sedimentation rates in ocean basins surrounding Greenland and Antarctica suggests that sediment production, sediment transport, and possibly denudation by permanent ice caps may be substantially lower than by periodic ice caps, such as the Laurentide. Low rates of sediment survival from the time of the Permo-Carboniferous and Precambrian glaciations suggest that predominance of marine deposition during some glacial epochs results in shorter lived sediment because of preferential tectonism and cycling of oceanic crust versus continental crust.
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Newton, Alicia. "Pliocene glaciation." Nature Geoscience 4, no. 11 (2011): 734. http://dx.doi.org/10.1038/ngeo1315.
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Arzhannikov, S. G., A. V. Arzhannikova, A. A. Chebotarev, et al. "Experience of applying the cosmogenic dating method (<sup>10</sup>Be) to assess the age and scale of the Pleistocene Glaciation in North-Eastern Siberia (based on the example of glacier complexes of the Chersky Ridge)." Geomorfologiâ i paleogeografiâ 55, no. 3 (2024): 53–72. https://doi.org/10.31857/s2949178924030039.
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The history of studying glacial complexes in North-Eastern Siberia goes back more than 150 years. During this period, extensive geological and geomorphological features were obtained, which made it possible to determine the stages, nature and extent of glaciations. At the same time, the lack of direct dating of the glacial relief obtained by geochronological methods does not allow for full-fledged paleogeographic reconstructions. This leads to discussions in both Russian and English literature about the possibility of the existence of glaciation in the mountains of North-Eastern Siberia. In this regard, to determine the size and time of glaciation in the southern part of the Chersky Range, we carried out a complex of geomorphological and geochronological studies, which are part of the international project “Searching for the missing ice sheet in Eastern Siberia”. Because of fieldwork in the Ohandya Ridge, in the Malyk-Sien River valley, three terminal moraine ridges have been identified, reflecting different stages of glaciation. Based on the dating of exposed boulders within three terminal moraine complexes, 22 10Be cosmogenic dates were obtained. The average exposed age for the outer moraine is 120.8±13.7 ka, for the middle one North-Eastern 37.7±4.9 ka and for the internal moraine North-Eastern 13.8±2.2 ka. The age of the terminal moraine complexes testifies to the mountain-valley character of the glaciation of the Chersky Range in the Middle and Late Pleistocene, and emphasizes the trend towards a gradual decrease in the maximum length of glaciers in Northeast Asia. The successive reduction of glaciers from MIS 6 to MIS 2 indicates an increase in the deficit of atmospheric precipitation and a significant cryoaridization of the region. The decreasing trend may be related to the sharply continental conditions observed in the interior of Eurasia and western North America. This trend contrasts with much of the glaciated areas in the Northern Hemisphere, where the maximum area of Late Pleistocene glaciers is reconstructed for LGM time (MIS 2). The obtained datings of the glacial complexes of the Chersky Ridge confirm that at the end of the Middle and Late Pleistocene glaciations here were of a limited nature and there was no single ice cover in the mountains.
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Peck, Stewart B., and Kenneth Christiansen. "Evolution and zoogeography of the invertebrate cave faunas of the Driftless Area of the Upper Mississippi River Valley of Iowa, Minnesota, Wisconsin, and Illinois, U.S.A." Canadian Journal of Zoology 68, no. 1 (1990): 73–88. http://dx.doi.org/10.1139/z90-012.
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This paper reports the results of a long-term survey of the invertebrates living in caves and other subterranean habitats in the Upper Mississippi River Valley, particularly in the region frequently but erroneously called the Driftless Area. Sixteen troglobitic species are known: two flatworms, two amphipods, one isopod, four spiders, one mite, and six collembolans. The terrestrial troglobite fauna probably represents cave invasion and isolation following Early Pleistocene glaciation, and demonstrates that the caves were habitable while the region was at the margin of Late Pleistocene glaciations. The groundwater troglobite fauna may have survived in situ while the region was covered by glacial ice in the Early Pleistocene. The troglophile fauna consists of at least 78 species, and these species may or may not have come into the region since the Wisconsinan glaciation recession. The presence of troglophile species in a particular cave is highly sporadic.
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Zech, Wolfgang, Rupert Bäumler, Oksana Savoskul, Anatoli Ni, and Maxim Petrov. "Bodengeographische Beobachtungen zur pleistozänen und holozänen Vergletscherung des Westlichen Tienshan (Usbekistan)." E&G Quaternary Science Journal 46, no. 1 (1996): 144–51. http://dx.doi.org/10.3285/eg.46.1.11.
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Abstract. Soil geographic studies were carried out in the Oigaing valley between Ugamsky and Pskemsky range NE of Tashkent (W-Tienshan, Republic of Uzbekistan) with special regard to the Pleistocene and Holocene glaciation. Clear end moraines of the last main glaciation are preserved at the junction of Maidan and Oigaing river at 1500-1600 m a.s.l. They show intensively weathered soils with a depth of more than 80 cm. Similar deposits ol presumably Pleistocene or late glacial origin are also located upvalley at the embouchure of numerous side valleys (Beschtor, Tekesch, Aütor) into the main valley of Oigaing. All side valleys are characterized by late glacial ground and end moraines in 2500-2700 m a.s.l. showing intensively weathered brown colored soils of 30-40 cm depth. Further moraines of Holocene or recent origin are located approach of the recent glaciers which descend to 3000-3200 m. They show shallow, initial soils, and presumably correspond with glacial advances during the so-called "Little Ice Age" with a maximum advance at about 1850 in the Alps, and in the middle Holocene at about 2000 or 4000 a BP. Highly weathered, and rubefied interglacial soils developed from old Quaternary gravel are preserved above high glacial ice marginal grounds of the last main glaciation (>2850 m a.s.l.) in the lower side valley of the Barkrak river. In the upper valley huge drift could be shown above the ice marginal grounds, but without typical forms of morainic deposits. They give evidence for older glaciations with a greater extent compared with the last main glaciation. However, no corresponding moraines are present in the working area.
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Matmon, A., J. P. Briner, G. Carver, P. Bierman, and R. C. Finkel. "Moraine chronosequence of the Donnelly Dome region, Alaska." Quaternary Research 74, no. 1 (2010): 63–72. http://dx.doi.org/10.1016/j.yqres.2010.04.007.
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AbstractWe present 10Be exposure ages from moraines in the Delta River Valley, a reference locality for Pleistocene glaciation in the northern Alaska Range. The ages are from material deposited during the Delta and Donnelly glaciations, which have been correlated with MIS 6 and 2, respectively. 10Be chronology indicates that at least part of the Delta moraine stabilized during MIS 4/3, and that the Donnelly moraine stabilized ∼ 17 ka. These ages correlate with other dates from the Alaska Range and other regions in Alaska, suggesting synchronicity across Beringia during pulses of late Pleistocene glaciation. Several sample types were collected: boulders, single clasts, and gravel samples (amalgamated small clasts) from around boulders as well as from surfaces devoid of boulders. Comparing 10Be ages of these sample types reveals the influence of pre/post-depositional processes, including boulder erosion, boulder exhumation, and moraine surface lowering. These processes occur continuously but seem to accelerate during and immediately after successive glacial episodes. The result is a multi-peak age distribution indicating that once a moraine persists through subsequent glaciations the chronological significance of cosmogenic ages derived from samples collected on that moraine diminishes significantly. The absence of Holocene ages implies relatively minor exhumation and/or weathering since 12 ka.
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Monegato, Giovanni, Cesare Ravazzi, Marta Donegana, Roberta Pini, Gilberto Calderoni, and Lucia Wick. "Evidence of a two-fold glacial advance during the last glacial maximum in the Tagliamento end moraine system (eastern Alps)." Quaternary Research 68, no. 2 (2007): 284–302. http://dx.doi.org/10.1016/j.yqres.2007.07.002.
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AbstractThe glacial history of the Tagliamento morainic amphitheater (southeastern Alpine foreland, Italy) during the last glacial maximum (LGM) has been reconstructed by means of a geological survey and drillings, radiocarbon dating and pollen analysis in the amphitheater and in the sandur. Two phases of glacial culmination, separated by a distinct recession, are responsible for glacial landforms and related sediments in the outer part of the amphitheater. The age of the younger advance fits the chronology of the culmination of the last glaciation in the Alps, well established between 24 and 21 cal ka BP (20 to 17.5 14C ka BP), whereas the first pulse between 26.5 and 23 cal ka BP (22 to 21 14C ka BP), previously undated, was usually related to older (pre-LGM) glaciations by previous authors. Here, the first pulse is the most extensive LGM culmination, but is often buried by the subsequent pulse. The onset and final recession of the late Würm Alpine glaciation in the Tagliamento amphitheater are synchronous with the established global glacial maximum between 30 and 19 cal ka BP. The two-fold LGM glacial oscillation is interpreted as a millennial-scale modulation within the late Würm glaciation, caused by oscillations in inputs of southerly atmospheric airflows related to Dansgaard–Oeschger cycles. Phases of enhanced southerly circulation promoted increased rainfall and ice accumulation in the southern Alps.
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Kaplan, Michael R., Daniel C. Douglass, Bradley S. Singer, Robert P. Ackert, and Marc W. Caffee. "Cosmogenic nuclide chronology of pre-last glacial maximum moraines at Lago Buenos Aires, 46�S, Argentina." Quaternary Research 63, no. 3 (2005): 301–15. http://dx.doi.org/10.1016/j.yqres.2004.12.003.
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At Lago Buenos Aires, Argentina, 10Be, 26Al, and 40Ar/39Ar ages range from 190,000 to 109,000 yr for two moraines deposited prior to the last glaciation, 23,000�16,000 yr ago. Two approaches, maximum boulder ages assuming no erosion, and the average age of all boulders and an erosion rate of 1.4 mm/103 yr, both yield a common estimate age of 150,000�140,000 yr for the two moraines. The erosion rate estimate derives from 10Be and 26Al concentrations in old erratics, deposited on moraines that are >760,000 yr old on the basis of interbedded 40Ar/39Ar dated lavas. The new cosmogenic ages indicate that a major glaciation during marine oxygen isotope stage 6 occurred in the mid-latitude Andes. The next five youngest moraines correspond to stage 2. There is no preserved record of a glacial advance during stage 4. The distribution of dated boulders and their ages suggest that at least one major glaciation occurred between 760,000 and >200,000 yr ago. The mid-latitude Patagonian glacial record, which is well preserved because of low erosion rates, indicates that during the last two glacial cycles major glaciations in the southern Andes have been in phase with growth and decay of Northern Hemisphere ice sheets, especially at the 100,000 yr periodicity. Thus, glacial maxima are global in nature and are ultimately paced by small changes in Northern Hemisphere insolation.
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Aber, James S., and Jan Lundqvist. "Glaciotectonic Structures in Central Sweden and their Significance for Glacial Theory." Géographie physique et Quaternaire 42, no. 3 (2007): 315–23. http://dx.doi.org/10.7202/032739ar.
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ABSTRACT Various glaciotectonic structures and landforms created by ice pushing are common in drift and interstadial sediments in a narrow belt of central Sweden. Described examples from the Lake Storsjôn vicinity demonstrate that glaciotectonic deformation took place while the area was deeply covered by the last Fennoscandian Ice Sheet. Deformation was controlled by pressure gradients related to position of the ice divide and ice movement away from the divide. As the position of the divide shifted during the last glaciation, so did the orientation of glaciotectonic structures. The regional distribution of glaciotectonic features in Fennoscandia falls into three zones: (1) inner zone of widespread, small- to moderate-sized features in older drift, (2) intermediate zone of small, isolated features in drift of the last glaciation, and (3) outer zone with all manner of large and small features in drift and soft bedrock. These zones are the cumulative results of multiple glaciations and reflect the overall distribution of deformable sediment and bedrock within the continental substratum.
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Dobrowolski, Radosław, Sławomir Terpiłowski, Marcin Szeliga, and Tadeusz Wiśniewski. "Flints of the Chełm Hills (Rejowiec flints) – origin, sedimentation environment and exploitation in prehistory – a case study from the Lechówka site." Sprawozdania Archeologiczne 74, no. 1 (2022): 11–29. http://dx.doi.org/10.23858/sa/74.2022.1.3110.
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Rejowiec flint from the Chełm Hills occur among glacigenic sediments of the Odranian glaciation and is referred to as erratic flints. The authors, based on the analysis of the sedimentary succession of a kame in Lechówka – within the boundaries of the largest outcrop, in so-called ‘Region I’ (Rejowiec region) – indicate that: (1) the probable source of the flints were older series of glacigenic sediments – from before the Odranian glaciation, (2) their great accumulation directly under the surface and – as a result – their considerable accessibility for exploitation in prehistory were caused by the ‘upfreezing of stones’ in the conditions of a periglacial environment during successive glacial periods (Odranian, Wartanian and Vistulian glaciations). The analysis of archaeological data confirmed the use of the local flints as early as in the Middle Palaeolithic and their most intense exploitation during two main periods – the final stage of the Palaeolithic and a period from the Late Neolithic to the Early Iron Age.
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Le Hir, G., Y. Goddéris, Y. Donnadieu, and G. Ramstein. "A geochemical modelling study of the evolution of the chemical composition of seawater linked to a "snowball" glaciation." Biogeosciences 5, no. 1 (2008): 253–67. http://dx.doi.org/10.5194/bg-5-253-2008.
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Abstract. The Snowball Earth theory initially proposed by Kirschvink (1992) to explain the Neoproterozoic glacial episodes, suggested that the Earth was fully ice-covered at 720 Ma (Sturtian episode) and 640 Ma (Marinoan episode). This succession of extreme climatic crises induced environmental perturbations which are considered as a strong selective pressure on the evolution of life (Hoffman et al., 1998). Using a numerical model of carbon-alkalinity global cycles, we quantify environmental stresses caused by a global glaciation. According to our results, we suggest that during global glaciations, the ocean becomes acidic (pH~6), and undersaturated with respect to carbonate minerals. Moreover the quick transition from ice-house to greenhouse conditions implies an abrupt and large shift of the oceanic surface temperature which causes an extended hypoxia. The intense continental weathering, in the aftermath of the glaciation, deeply affects the seawater composition inducing rapid changes in terms of pH and alkalinity. We also propose a new timing for post glacial perturbations and for the cap carbonates deposition, ~2 Myr instead of 200 kyr as suggested in a previous modelling study. In terms of Precambrian life sustainability, seawater pH modifications appear drastic all along the glaciation, but we suggest that the buffering action of the oceanic crust dissolution avoids a total collapse of biological productivity. But short-lived and large post-glacial perturbations are more critical and may have played the role of an environmental filter proposed in the classic snowball Earth theory. Although the link between environmental changes and life sustainability cannot be modelled accurately, we suggest that only a permissive life (Knoll, 2003) may explain the relative continuity in microfossils diversity observed before, during and after Neoproterozoic glaciation events.