To see the other types of publications on this topic, follow the link: Glaciation.
Dissertations / Theses on the topic 'Glaciation'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Glaciation.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Holden, W. G. "The glaciation of central Ayrshire." Thesis, University of Glasgow, 1997. http://theses.gla.ac.uk/1585/.
Full text
2
Ross, Hamish. "The last glaciation of Shetland." Thesis, University of St Andrews, 1997. http://hdl.handle.net/10023/15278.
Full textAbstract:
Evidence of the last glaciation of the Shetland Islands, UK, is re-examined and combined with new data on terrestrial glacigenic deposits and recent offshore data from the continental shelf to produce a dynamic, integrated model of the history of the whole ice cap. It is shown that evidence which has previously been attributed to last glacial, or earlier, Scandinavian ice incursion, might be explained by the eastwards migration of local ice sheds. At its maximum, the ice sheet reached the continental shelf edge to the west of the islands, at least 75 km east, at least 50 km north and might be seen as a peninsular extension of the Scottish ice sheet to the south. The changing patterns of ice flow during deglaciation are reconstructed, implying an early phase of deglaciation at the west and northwest margins (possibly accounting for the suggested eastern migration of the ice shed), followed by retreat at more northern, then eastern, then southern margins. It is suggested that the above pattern reflects tidewater calving controlled by bathymmetric variation around the ice sheet. During a later phase of deglaciation, the margin of the ice cap may have grounded at around the current -100m bathymmetric contour and from there retreated terrestrially. The importance of topographic control on patterns of deglaciation as ice retreated towards the island group is clearly established. Some minor moraines in parts of Shetland are due to active ice margins but their age is unknown. Radiocarbon dates reported here show that the last glaciation was Late Weichselian and that the maximum northern extent was at least 50 km north of the islands. The concepts of an eastwards migrating ice shed and an early, extensive ice cap retreating to a grounding point, could have parallels elsewhere in Scotland during the last glaciation. The methodology applied in this study of Shetland - integrating onshore and offshore data, and developing a dynamic picture of the whole ice cap - needs to be applied to the last Scottish ice sheet also.
3
Rae, Alaric Campbell. "Late Quaternary glaciation in Southwest Ireland." Thesis, Coventry University, 2004. http://curve.coventry.ac.uk/open/items/03055be6-aad0-4313-d72e-1dac2156f221/1.
Full textAbstract:
During the last main phase of glaciations (26-13kaBP) an ice cap developed in south west Ireland and ice, from a dispersal centre in the vicinity of Kenmare, flowed north and diverged on the southern slopes of the Macgillycuddy’s Reeks. On these slopes, a weathering limit separates ice-moulded bedrock, on low ground, from frost-weathered terrain above. Assessment of bedrock dilation joint characteristics, Schmidt hammer R-value data, clay-sized mineral contents and magnetic properties of basal soil samples confirms significant contrasts in the degree of weathering above and below this limit. The weathering limit declines in altitude along former ice flow-lines and is confluent with morainic deposits on the eastern side of the Gap of Dunloe and on the western slopes of Skregbeg. This evidence supports the assertion that the high-level weathering limit is a periglacial trimline that marks the former maximum upper limit of the body of ice, which occupied this area of southwest Ireland during the LGM. This evidence, however, does not confute the notion that cold based, non-erosive plateau ice may have covered some or all of the upland surfaces that occur above the recorded weathering limits. Reconstruction of the former ice surface profile from periglacial trimline limits along three former flow lines yielded mean estimates for basal shear stress that ranged from 104.2 to 125.9 kPa. Although these values are high, they are within the range deemed normal for glaciers and ice sheets. The values suggest that the reconstructed areas of the ice cap were warm based and flowing on a bedrock substrate. This is supported by the geomorphological evidence of these areas, which shows that a landform – sediment association has developed consisting of zones of glacial scour and a thin, discontinuous drift cover. This contrasts with the glacial geomorphology of northern parts of the study area, where drift cover is largely continuous, and extensive in valley bottoms and on surrounding hillsides, and is associated with large lateral moraines.
4
Poussart, Pascale Francine. "Late Ordovician glaciation, modelling experiments of a paradox." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37415.pdf.
Full text
5
Kilfeather, Aoibheann Aoife. "Glaciation, deformation and till porosity : County Laois, Ireland." Thesis, Queen Mary, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413647.
Full text
6
Carr, Simon James. "The last glaciation of the North Sea Basin." Thesis, University of London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266821.
Full text
7
Mitchell, W. A. "Glaciation of upper Wensleydale and adjoining watershed regions." Thesis, Royal Holloway, University of London, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322134.
Full text
8
McCarron, Stephen Gerard. "Late Devensian glaciation of the north of Ireland." Thesis, University of Ulster, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268575.
Full text
9
Hughes, Philip David. "Quaternary glaciation in the Pindus Mountains, Northwest Greece." Thesis, University of Cambridge, 2004. https://www.repository.cam.ac.uk/handle/1810/273442.
Full textAbstract:
Geomorphological and geological evidence for former Quaternary glaciation has been mapped n the Pindus Mountains of Northwest Greece. the dynamics and chronology of glaciation in this area has been established through sedimentological analysis, soil analysis and Uranium-series dating. Four glacial events are recorded in the sedimentological and geomorphological records. The more extensive recorded glaciation pre-dates 350,000 years BP and was characterised by extensive valley glaciers and ice-fields. A second glaciation occurred prior to the last interglacial, before <i>ca</i>. 127,000 years BP, and was characterised by glaciers that reached mid-valley positions. the height of the last glacial stage in Greece (30-20,000 <sup>14</sup>C years BP) is recorded by small cirque glacier moraines and relict periglacial rock glaciers. evidence for a fourth glacial phase is recorded only in the highest cirques of Mount Smolikas (2637 m a.s.l.), the highest peak in the Pindus Mountains. This phase of glaciation is likely to have occurred during the Late-glacial Substage (14-10,000 <sup>14</sup>C years BP). All of the glaciers during the different glacial stages were reconstructed and used alongside periglacial rock glaciers to determine palaeoclimate. During the glacial maximum of the last glacial stage mean annual temperatures were <i>ca</i>. 8-9°C lower than at present, and mean annual precipitation greater than 2000 mm - similar to modern values. Earlier glacial maxima are likely to have been colder but with mean annual precipitation still greater than 2000 mm. Maximum glacier extent in the Pindus Mountains is likely to have preceded the most severe arid phase of glacial cycles indicated in the pollen record and also global glacial maxima. this was because of the small size of the former Pindus glaciers and their rapid response to climate change, as well as the increased prevalence of aridity around the global glacial maxima. The glacial sequence in the Pindus Mountains represents the longest and best-dated recognised record of glaciation in the Mediterranean region and provides a stratigraphical framework for Quaternary cold-stage climates in Greece.
10
Midgley, Nicholas Goulden. "Moraine-mound development in Britain and Svalbard : the development of 'hummocky moraine'." Thesis, Liverpool John Moores University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247350.
Full text
11
Hanna, Joanne E. "Dynamics of coastal and nearshore evolution in southeast Ireland." Thesis, University of Ulster, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274396.
Full text
12
Ghienne, Jean-François. "Modalites d'enregistrement d'une glaciation ancienne : exemple de la glaciation fini-ordovicienne sur la plate-forme nord-gondwanienne en afrique de l'ouest." Université Louis Pasteur (Strasbourg) (1971-2008), 1998. http://www.theses.fr/1998STR13070.
Full textAbstract:
Le gondwana occidental, aux hautes latitudes australes a l'hirnantien (ordovicien superieur), est alors soumis aux effets d'une glaciation majeure enregistree dans les depots silicoclastiques de la plate-forme cratonique nord-gondwanienne (afrique de l'ouest et du nord, moyen-orient, bassins europeens distaux). A partir d'une etude de terrain en mauritanie (regions de l'adrar et du hodh), et d'une revue bibliographique, le but de ce travail est de caracteriser les facies et la dynamique sedimentaires sous controle glaciaire, en precisant la part des effets du glacio-eustatisme et de la glacio-isostasie. La glaciation est enregistree par une mega-sequence mise en place lors de la deglaciation. En afrique de l'ouest, la discordance de ravinement, polyphasee et remodelee par l'erosion glaciaire, est surmontee par des depots fluvio-glaciaires aggradants enregistrant les dernieres fluctuations glaciaires. L'inondation fini-glaciaire permet ensuite le developpement et la progradation de facies deltaiques ou glaciomarins, avec regressions forcees par le rebond postglaciaire dans les domaines proximaux. La fin de la deglaciation se marque par une surface transgressive d'erosion marine, soulignant un biseau transgressif de sables littoraux azoiques et heterochrones surmontes d'argilites a graptolites (ordovicien terminal, silurien inferieur). Des apports surabondants sur une courte periode, comblant une accommodation importante en partie issue des ravinements sous-glaciaires prealables, caracterisent la periode glaciaire pendant laquelle les variations de niveau marin sont determinantes. Des apports deficitaires permettent pendant le silurien l'enregistrement de specificites regionales liees aux regimes de subsidence.
13
Pion, Gilbert. "Magdalénien, Epipaléolithique et Mésolithique ancien au Tardiglaciaire dans les deux Savoie et le Jura méridionnal." Besançon, 2004. http://www.theses.fr/2004BESA1011.
Full textAbstract:
Le sujet de la thèse se rapporte à la connaissance des peuplements magdaléniens, épipaléolithiques et mésolithiques durant la phase du Tardiglaciaire dans les deux Savoie et le Jura méridional. L'étude propose d'abord un bilan des connaissances publiées et issues de fouilles anciennes puis, développe les résultats pluridisciplinaires des recherches de l'auteur effectuées dans quatre sites préhistoriques des deux Savoie. L'auteur analyse les données chrono-industrielles spécifiques à chaque culture, dans leur cadre naturel, c'est à dire en synchronisme avec le paléoenvironnement végétal et animal. Un schéma chrono-culturel de tous les sites de l'étude est proposé pour servir de base de discussions avec les chercheurs concernés par ces cultures<br>This theses deals with the attainments of magdalenian, epipaleolithics and mesolithics settlements during the Tardiglacial period in both Savoie and southern Jura. This essay presents, first, a statement of the attainments published at the end of ancient excavations then it develops the pluridiscinary results of the author's personal excavations achieved in four prehistorics places in both Savoie. The author analysis the chrono-industrial data to each culture in their natural environnment, that is to say synchronised with their paleoenvironnment vegetal and animal. A chrono-cultural schema of all the places of the study is proposed to be used as a bases for further discussions with researchers concerned with those cultures
14
Smith, Jacqueline Ann. "Timing and extent of glaciation in the tropical Andes." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2005. http://wwwlib.umi.com/cr/syr/main.
Full text
15
Colleoni, Florence. "On the Late Saalian glaciation : A climate modeling study." Doctoral thesis, Stockholms universitet, Institutionen för geologi och geokemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-29284.
Full textAbstract:
This thesis focuses on the glaciation of the Late Saalian period (160 -140 ka) over Eurasia. The Quaternary Environment of the Eurasian North (QUEEN) project determined that during this period, the Eurasian ice sheet was substantially larger than during the entire Weichselian cycle and especially that of the Last Glacial Maximum (21 ka, LGM). The Late Saalian astronomical forcing was different than during the LGM while greenhouse gas concentrations were similar. To understand how this ice sheet could have grown so large over Eurasia during the Late Saalian, we use an Atmospherical General Circulation Model (AGCM) coupled to an oceanic mixed layer and a vegetation model to explore the influence of regional parameters, sea surface temperatures (SST) and orbital parameters on the surface mass balance (SMB) of the Late Saalian Eurasian ice sheet. At140 ka, proglacial lakes, vegetation and simulated Late Saalian SST cool the Eurasian climate, which reduce the ablation along the southern ice sheet margins. Dust deposition on snow has the opposite effect. The presence of a Canada Basin ice-shelf during MIS6 in the Arctic Ocean, does not affect the mass balance of the ice sheet. According to geological evidence, the Late Saalian Eurasian ice sheet reached its maximum extent before 160 ka. Northern Hemisphere high latitude summer insolation shows a large insolation peak near 150 ka. The simulated climate prior to 140 ka is milder and ablation is larger along the southern margins of the Eurasian ice sheet although the mean annual SMB is positive. The Late Saalian Eurasian ice sheet may have been large enough to generate its own cooling, thus maintaining itself over Eurasia.<br>Joint PhD Degree between Stockholm University and Université Joseph FourierAt the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Submitted. Paper 5: Manuscript.
16
Corbett, W. M. "Till facies and glaciation in parts of East Anglia." Thesis, University of East Anglia, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309954.
Full text
17
Jull, Matthew Gower. "The effect of glaciation on mantle melting beneath Iceland." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627262.
Full text
18
Adamson, Kathryn. "The response of Mediterranean river basins to Pleistocene glaciation." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/the-response-of-mediterranean-river-basins-to-pleistocene-glaciation(d85806cf-24bf-4e06-81ca-7f2f83bcd00c).html.
Full textAbstract:
Fluvial morphosedimentary records surrounding the Orjen massif, western Montenegro, have been studied to investigate the response of Mediterranean river systems to Pleistocene glaciation. A range of depositional contexts, across 12 sites, have been analysed, including: terraced alluvial valley fills, poljes and alluvial fans. These sites include both ice marginal contexts and more distal locations. It can be argued that these settings are broadly representative of the depositional environments found within glaciated upland catchments across the Mediterranean, and especially those in limestone landscapes. The timing of fluvial activity has been constrained using detailed stratigraphical analysis, 35 U-series dates, calcite micromorphology, and soil profile analysis. The fluvial record is fragmentary but is in good agreement with the Pleistocene glacial history of the Orjen massif, developed by Hughes et al. (2010).Two main phases of Pleistocene fluvial sedimentation have been identified in the morphosedimentary record. The most extensive phase of fluvial aggradation is correlated to MIS 12 (Kotorska-Sušica Member) and is characterised by the infilling of large depocentres beyond the maximum MIS 12 ice margins. These deposits dominate the fluvial record. The next recorded phase of fluvial deposition is correlated to MIS 6 (Krivošije Member) and contains only limited evidence of fluvial activity. No morphosedimentary evidence for fluvial deposition in MIS 5d-2 has yet been observed in the study area. An analysis of published studies shows that the Pleistocene glacial and fluvial archives are highly fragmentary across the Mediterranean basin. The limestone karst terrain of Mount Orjen has exerted an important influence on sediment delivery and the meltwater pathways draining the Orjen ice cap over successive glacial cycles. Evidence suggests that, since MIS 12, sediment supply to the fluvial system has declined in accord with the decreasing magnitude of glaciation and subterranean karst flows havebecome increasingly dominant over surface flows. As ice volume and extent decreased in the cold stages following MIS 12, the Pleistocene glacial and surface fluvial systems became progressively decoupled. Two types of surface meltwater routes operated during MIS 12: Type 1 – steep sided limestone bedrock gorges; and Type 2 - alluvial channels draining directly from the ice margin. These contrasting pathways are associated with distinctive sedimentological signatures both at the macro-scale and within the fine (<63µm) matrix fraction This study provides one of the first attempts to directly correlate Pleistocene glacial and fluvial records – and to consider the process interactions – in a range of depositional contexts at the landscape scale.
19
Salt, Keith Edward. "Palaeo-ice sheet dynamics and depositional settings of the Late Devensian ice sheet in south-west Scotland." Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341950.
Full text
20
Chandler, Benjamin Marc Peter. "Extent, style and timing of former glaciation in the Gaick, Central Grampians, Scotland, and implications for palaeoclimate." Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/44688.
Full textAbstract:
The well-preserved record of glacial sediment-landform assemblages in Scotland provides an excellent opportunity to reconstruct the extent and style of former glaciation. Despite a concerted research effort, there remain areas where glacial events are poorly constrained. This is exemplified by the Gaick, a dissected plateau in the Central Grampians, which has proven to be an enigmatic and controversial area. Previously-proposed models fail to adequately explain glacial events in the area, partly due to a paucity of detailed geomorphological, chronological and sedimentological investigations. This thesis presents the results of systematic studies of the sediment-landform record in the Gaick. These investigations, combined with the application of morphostratigraphic principles, have elucidated sediment-landform signatures indicative of multiple glacier fluctuations, specifically (i) interactions of local and regional ice lobes following unzipping during ice sheet deglaciation, (ii) a major stillstand of an extensive pre-Younger Dryas plateau icefield, and (iii) spatiallyrestricted plateau icefield glaciation during the Younger Dryas. The sediment-landform record also suggests a two-phased Younger Dryas advance, as has been found elsewhere in Scotland. The sediment-landform evidence was used to produce palaeoglaciological reconstructions for the three glacial phases. The clarity and completeness of the geomorphological record relating to the Younger Dryas, combined with ice surface profile modelling, allowed the three-dimensional reconstruction of a ~42 km2 plateau icefield. This reconstruction yielded an equilibrium line altitude value of 751 ± 46 m, which was used to derive a sea-level equivalent precipitation estimate of 826 ± 331 mm a-1. Taken together with glacier-derived precipitation estimates from across Scotland, this indicates a strong west-east precipitation gradient during the Younger Dryas. This thesis arrives at a more nuanced understanding of former glaciation in the Gaick, resolving discrepancies with previous conceptual models. In particular, this thesis demonstrates that the Gaick was an important ice dispersal centre throughout the Last Glacial-Interglacial Transition.
21
Jones, Andrew. "Sedimentological record of the late palaeozoic Gondwanan glaciation in Queensland /." St. Lucia, Qld, 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17532.pdf.
Full text
22
Davies, Mark Thomas Lloyd. "A polar paradise the glaciation of South Victoria Land, Antarctica /." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2004. http://dare.uva.nl/document/71753.
Full text
23
Dortch, Jason M. "Defining the Timing of Glaciation in the Central Alaska Range." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1162575242.
Full text
24
Thackray, Glenn D. "Glaciation and neotectonic deformation on the western Olympic Peninsula, Washington /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/6719.
Full textAbstract:
Thesis (Ph. D.)--University of Washington, 1996.<br>Accompanying maps: Plate 1: Quaternary geologic map of the Hoh, Queets, and lower Clearwater valley, Washington. Plate 2: Stratigraphic cross-section, Hoh River to Raft River. Vita. Includes bibliographical references (leaves [131]-139).
25
Taylor, Justin. "Large-scale sedimentation and ice sheet dynamics in the Polar North Atlantic." Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313014.
Full text
26
Lamy, au Rousseau Roseline. "Dynamique sédimentaire dans un lac proglaciaire : deltas, rythmites, variations du niveau de l'eau... : exemple du bassin de la combe d'Ain (Jura), au Pléniglaciaire würmien /." Dijon : Centre des sciences de la Terre, 1991. http://catalogue.bnf.fr/ark:/12148/cb356879467.
Full text
27
Huntley, David Hayes. "The late Wisconsinan glaciation of east-central Taseko Lakes, British Columbia." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23864.pdf.
Full text
28
Bloxsom, Peter G. "North Atlantic ocean circulation and the onset of Northern Hemisphere glaciation." Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/73539/.
Full textAbstract:
Since the early Cenozoic, the Earth’s climate has been gradually cooling. Large ice sheets have expanded on several occasions in the past 5000 kyr (50 Ma), with the last major expansion being the onset of major ice sheets in the Northern Hemisphere between 3600 and 2500 ka. This period was characterised by a prolonged increase in ice volume, modulated by orbital forcing. At the same time, major tectonic changes were taking place, with the closure of the Central American Seaway most significant. This thesis aims to address the issue of what caused the onset of major Northern Hemisphere glaciation through an in depth study of samples from North Atlantic ODP Site 982 (57° 31’ N, 15° 51’ W; 1145 m water depth). Multi-species benthic foraminifera composite trace metal records (Mg/Ca, B/Ca, Li/Ca, Cd/Ca) were produced, and the composite Mg/Ca record was used to develop a new regional temperature calibration for the Pliocene. Paleoceanographic records of bottom water temperature and saturation state were produced, as well as bottom water flow speed records using the Sortable Silt (SS) proxy. Bottom water temperature (BWT) records showed an abrupt, ~2°C cooling at 2800-2700 ka, consistent with other previously published records. These data are combined with previously published benthic stable isotope (δ18Ob) records to reconstruct seawater oxygen isotope reconstructions (δ18Osw) across the period of study, and this is found to predominately reflect changes in global ice volume. A major and prolonged increase in ice volume (3500-3000 ka) is identified, equivalent to up to ~55m sea level decrease. The response of the North Atlantic region to this ice sheet growth was tested using previously published sea surface temperature (SST) and δ18Ob records from ODP Site 982, in addition to the new record from this study. The ice volume was found to have influenced the response of SST, δ18Ob, and SS to orbital forcing from changing insolation. Prior to the ice sheet growth, bottom water flow speed varied proportionally with sea surface temperatures, with increased deep water formation during periods of high seasonality. The growing ice sheets responded more slowly to insolation changes, and the presence of this ice sheet increased deep water formation by further cooling saline surface waters. This resulted in feedback loops that intensified deep water flow, leading to a significant increase in North Atlantic Deep water penetration to the southern ocean. A major decrease in δ18Osw at 2800-2700 ka was interpreted as either a loss of Antarctic ice mass, or a reorganization of North Atlantic water masses. Comparison of ice volume records with orbital spectra and reconstructions of the closure of the Central American Seaway suggest the immediate cause of Northern Hemisphere glaciation was a period of orbital conditions favourable to ice sheet growth. Another underlying cause was a series of tectonic shifts, including the closure of the Central American Seaway from 4200 ka, which changed heat and moisture transport patterns to the high latitudes.
29
Peters, Jared Lee. "Late Quaternary glaciation of the continental shelf offshore of west Ireland." Thesis, Ulster University, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.697540.
Full textAbstract:
Several attributes of the last British-Irish Ice Sheet (BIIS) make it a potentially important analogue to marine-based sectors of modern ice sheets, which are sensitive to oceanic and climatic changes and unstable during the current global climate warming. However, limitations on knowledge of the last BIIS's marine termini hinder the use of this ice mass in comparative assessments or modelling. This research addresses this critical knowledge gap through multiproxy examinations of BIIS marine landforms, sedimentation and ice-proximal palaeoenvironments. A multifaceted examination of the outer shelf (Porcupine Bank and Slyne Trough) using geomorphology, sedimentology and geochronology provides the first confirmation of BIIS shelf-wide extension during the last glaciation (Late Midlandian/Late Devensian) west of Ireland. Multivariate biofacies examinations from the outer shelf suggest the introduction of relatively warm and saline Atlantic water following BIIS decoupling and ice shelf formation. Shelfwide analyses of glacigenic deposits (till and glaciomarine) and landforms (moraines and grounding-zone wedges) provide the first estimates of BIIS marine-margin retreat rates and detailed reconstructions of BIIS marine-margin behaviour west of Ireland. These analyses reveal a major stillstand (<3,300 years) that punctuated overall retreat and deposited a large (~IS0-km long) grounding-zone wedge. Prior to this stillstand, the BIIS was stabilised by a buttressing ice shelf and its grounding line retreated at ~ 74 km/yr; following the stillstand and the loss of the buttressing ice shelf, the BIIS marine-margin retreated to the modern western Irish shoreline at an accelerated rate of ~ 113 m/yr. Radiocarbon analyses of glacitectonised glaciomarine sediment record the first evidence of an Irish ice mass readvancing offshore during the Nahanagan (Younger Dryas) Stadia. Shelf-wide palaeoenvironmental assessments using both novel and well-established multivariate and statistical techniques elucidate a previously unknown, likely climate-driven readvance (the Galway Lobe readvance) and suggest that initial BIIS marine-margin retreat was forced by climate or ocean warming.
30
Tate, C. Jill. "Late Quaternary glaciation and environmental change in Southern Ross-shire, Scotland." Thesis, University of St Andrews, 1996. http://hdl.handle.net/10023/11114.
Full textAbstract:
Despite considerable active research in the realm of Quaternary studies in Scotland, some parts of the Scottish Highlands remain largely uninvestigated in terms of both glacial and environmental history. For many areas of Scotland the glacial history has been examined: researchers have ascertained aspects of the nature of the Late Devensian (Weichselian) ice sheet that covered most of Scotland and subsequent readvances, chiefly the Loch Lomond Readvance. In a 1979 review of the Loch Lomond Readvance in the British Isles, Sissons published a map of the glacial limits relating to this latest period of glacial activity in Scotland (Figure 1.1). Since then this map has been only slightly modified with certain limits having been established in the western Grampians. For the area further north, little accurate information has been added to this picture. One of the most noticeable omissions in relation to the Loch Lomond Readvance is in the area between Glen Carron and Glen Shiel in southern Ross-shire. Published research regarding the earlier Late Devensian ice sheet is also sparse. Information regarding other aspects of the Quaternary such as those detailed in other parts of the Scottish Highlands are similarly lacking for this area. There are no published accounts of the vegetation history of the area nor of Late Quaternary sea-level changes. This study seeks to fill in some of these gaps with specific reference to the Late Devensian glaciation and aims to relate the patterns of glaciation with other contemporaneous environmental changes through to the establishing of interglacial conditions in the early Flandrian period. Recent studies have demonstrated that aspects of the Late Quaternary environment can usefully be related and this study attempts to follow a similar procedure.
31
Guiter, Frédéric. "Contribution pollen-analytique à l'histoire de la végétation au cours des derniers 100 000 ans dans la région d'Evian (Haute Savoie, France) : implications pour la chronologie du dernier glacier du Rhône." Aix-Marseille 3, 2003. http://www.theses.fr/2003AIX30053.
Full textAbstract:
Un sondage sur le haut Plateau cTEvian a livré un profil tourbeux homogène intercalé entre deux momines. L'étude paléobotanique et paléoentomologique de ce profil témoignent d'un environnement marécageux bordé par une pessière-sapinière. La présence de cette forêt indique que cette tourbe s'est déposée au cours du dernier interglaciaire. Les analyses polliniques et radiométriques de trois profils paléolacustres, prélevés dans deux marais actuels ont permis de reconstituer l'histoire de la végétation depuis le dernier retrait glaciaire. D'après les données palynostrarigraphiques et radiométriques, la déglaciation du plateau aurait débuté avant le L. GM Ces données inédites apportent un calage biostratigraphique en faveur d'un maximum wunnien ancien du glacier du Rhône, et de son extension plus modeste pendant le L. GM Enfin, les études polliniques ont mis en évidence l'impact anthropique sur l'évolution du couvert forestier sur le plateau<br>A 2 m profile of intramoraimc organic sediments was cored from the Evian high plateau. Pollen, plant macrofossils and insect remains were used to reconstruct the local palaeoenvironment, which may be compared with a mire surrounded by a dense Abies /Pvsa mixed forest. Moreover, the use of pollen and macrofossil data led necessarily to attribute this peat layer to the final Eemian. Pollen and radiometric analyses of four palaeolacustrine profiles have allowed us to reconstruct vegetation dynamics since the last ice retreat. According to palynostratigraphic and radiocarbon data, the last degladation would have occurred prior to the L. GM Isotopic and magnetic analyses have evidenced some climatic variability during the Lateglacial that had some impact on vegetation dynamics. Accordingly to the geomorphological context of the area, these new data indicate that the Wiirmian maximum of the Rhone glacier might have occurred earlier than assumed, and prior to the Last Glacial Maximum
32
Ó, Cofaigh Colm. "Late-Quaternary glaciation and postglacial emergence, southern Eureka Sound, high-Arctic Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq39576.pdf.
Full text
33
Pu, Judy (Judy P. ). "Geochronological constraints on the Trinity diamictite in Newfoundland : Implications for Ediacaran glaciation." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/114096.
Full textAbstract:
Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2016.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 21-26).<br>The Avalon terrane in Newfoundland includes the Ediacaran Gaskiers Formation, which has been associated with a Snowball glaciation event. The complicated regional stratigraphy and lack of precise geochronological constraints has made it difficult to determine the spatial and temporal extent of the Gaskiers glaciation. Recent recognition of a diamictite facies on the nearby Bonavista Peninsula correlative with the Gaskiers diamictite has allowed for new, high-precision geochronological constraints on the Gaskiers glaciation and constrains the duration of the event to less than 390 ±320 kyr. The Snowball Earth hypothesis requires that glaciation continued for several millions of years so that CO2 could build up to high enough levels in the atmosphere for catastrophic deglaciation; the short duration of the Gaskiers event makes it unlikely to have been a Snowball event. Further geochronological studies are needed to determine whether the Gaskiers glaciation was a discrete event or if it was a glacial maximum in a longer Ediacaran ice age.<br>by Judy Pu.<br>S.B.
34
Darvill, Christopher. "The nature and timing of Late Quaternary glaciation in southernmost South America." Thesis, Durham University, 2015. http://etheses.dur.ac.uk/11136/.
Full textAbstract:
The timing and extent of former ice sheet fluctuations can demonstrate leads and lags during periods of climatic change and the forcing factors responsible, but this requires robust glacial chronologies. Patagonia, in southern South America, offers a well preserved record of glacial geomorphology over a large latitudinal range that is affected by key climatic systems in the Southern Hemisphere, but establishing the timing of ice advances has proven problematic. This thesis targets five southernmost ice lobes that extended from the former Patagonian Ice Sheet during the Quaternary; from north to south: the Río Gallegos, Skyring, Otway, Magellan and Bahía Inútil – San Sebastián (BI-SSb) ice lobes. The region is chosen because there is ambiguity over the age of glacial limits, which have been hypothesised to relate to different glacial cycles over hundreds of thousands of years but yield cosmogenic nuclide exposure data dominantly < 50 ka. This contradiction is the focus of the thesis: was the sequence of glacial limits deposited over multiple glacial cycles, or during the last glacial cycle? A new geomorphological map is used to reconstruct glacial limits and to help target new dating. Cosmogenic nuclide depth-profiles through glacial outwash are used to date glacial limits whilst accounting for post-depositional processes. These reveal that limits of the BI-SSb lobe hypothesized to date from MIS 12 (ca. 450 ka) and 10 (ca. 350 ka) were actually deposited during the last glacial cycle, with the best-dated profile giving an MIS 3 age of ca. 30 ka, indicating an extensive advance prior to the global Last Glacial Maximum (gLGM). A glacial reconstruction indicates that this may not have been unique to the BI-SSb lobe, and a compilation of published dates reveals that similar advances during the last glacial cycle indicate related forcing factors operating across Patagonia and New Zealand.
35
Blais, Andree (Andree Paul) Carleton University Dissertation Geology. "Lennoxville glaciation of the middle Chaudiere and Etchemin valleys, Beauce Region, Quebec." Ottawa, 1989.
Find full text
36
Langford, Harry. "Sedimentological, palaeogeographical and stratigraphical aspects of the Middle pleistocene geology of the Peterborough area, eastern England." Thesis, Anglia Ruskin University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326053.
Full text
37
Moreau, Julien. "Architecture stratigraphique et dynamique des dépots glacières ordoviciens du bassin de Murzuq (Libye)." Université Louis Pasteur (Strasbourg) (1971-2008), 2005. http://www.theses.fr/2005STR1GE13.
Full textAbstract:
La glaciation ordovicienne est considérée comme un événement majeur et singulier dans l'histoire de la Terre. Ce manuscrit présente les résultats d'une thèse effectuée sur la série glaciaire ordovicienne, particulièrement bien préservée dans le Bassin de Murzuq (Libye). Cette étude est en premier lieu basée sur un travail de terrain associé aux outils de télédétection dans la zone de Ghat-Tikiumit (bordure Ouest du bassin) et à des méthodes d'investigations pétrolières comme la modélisation stratigraphique des affleurements et l'interprétation de blocs sismiques 3D (Nord du bassin). L'utilisation conjointe de ces techniques a conduit à des résultats sur les relations entre la dynamique de l'inlandsis ordovicien, l'architecture stratigraphique et la reconstitution des systèmes de dépôt et ce, à différentes échelles de temps et d'espace. Ainsi, au sein de la série glaciaire de Libye, sont reconnus deux grands cycles glaciaires, chacun se terminant par un retrait complet de la glace du bassin. Chaque cycle comprend plusieurs phases glaciaires (avancée puis retrait de la glace). Chaque retrait glaciaire est suivi du dépôt d'une séquence de dépôt glaciaire dont l'évolution sédimentaire a été analysée en terme de stratigraphie séquentielle. Lors des phases d'avancée, la zone d'étude est plusieurs fois sous l'influence de grands fleuves de glaces. La séquence de déglaciation finale, effectuée par paliers, est à l'origine d'une imbrication le long du profil de dépôt de fan-deltas proglaciaires. La transgression postglaciaire finale utilise la forte topographie résiduelle liée à cette déglaciation, localisant ainsi les réservoirs ordoviciens et la roche mère silurienne. La synthèse des différents résultats a conduit à proposer une courbe d'évolution eustatique ainsi que d'une reconstitution des événements sédimentaires et glaciologiques à l'échelle du Bassin de Murzuq au cours de la glaciation ordovicienne<br>The Late Ordovician glaciation is considered as an outstanding event of Earth history. Preservation of Ordovician glacial deposits is exceptional into the Murzuq Basin (Libya) and the aim of this PhD thesis is to study this succession. This work is principally based on field work study in the Ghat-Tikiumit area (west rim of the basin) associated with remote sensing analysis and petroleum investigation methods (stratigraphical modelling and interpretation of 3D seismic surveys). Results consist in relationships between ice-sheet dynamic, stratigraphical architecture and depositional system reconstructions at various space and time scales. Thus, two major glacial cycles are recognized into the Libyan glacial succession. Both terminate by a complete ice-sheet retreat and associated postglacial transgression at basin scale. Each cycle comprise several glacial phases (ice-sheet advance then retreat). Ice retreat is followed by the deposition of a glacial depositional sequence. During ice-sheet advances, the study area is repeatedly covered by ice streams. The final deglaciation sequence creates landward stepwise imbricate proglacial fan-deltas and associated ice fronts. Final postglacial transgression is driven by strong remnant topography and is responsible for the localisation of the Ordovician reservoir rocks and Silurian "hot-shale". Results consist in, into the Murzuq Basin, sequence stratigraphy interpretation of the glacial succession, eustatic evolution as well as ice-sheet and sedimentary reconstruction through the different glacial cycles and phases
38
Dix, Justin K. "The use of high resolution geophysics for the investigation of submerged palaeo-glaciomarine environments." Thesis, University of St Andrews, 1996. http://hdl.handle.net/10023/15271.
Full textAbstract:
A multi-disciplinary, high resolution, geophysical investigation of a Scottish Sea loch has facilitated both the reconstruction of a detailed late Quaternary para-stratigraphic model and the critical assessment of the acquisition and analytical methodologies most appropriate for the study of submerged palaeo-glaciomarine environments. Loch Ainort, situated on the eastern coast of the Isle of Skye, has been surveyed using a 192 kHz echosounder, a 400 kHz side scan sonar and a 3.5 kHz sub-bottom profiler. Lithological calibration was provided by the analysis of both in situ core data and extant terrestrial data sets. It is proposed that for the effective reconstruction of these and any other nearshore palaeo-environments a multi-disciplinary geophysical approach is essential. The critical control on success is the adherence, during interpretation, to a single unifying seismo-analytical framework. The seismo-stratigraphical analysis technique has been adapted for high- resolution work in order to provide this rigid framework. Objective descriptive analysis of the seismic traces provides a "seismic para-stratigraphy" which when combined with lithological data is used to construct a "composite para-stratigraphy". This is a process based, litho-stratigraphic interpretation that, by virtue of the detailed spatial extent afforded it by geophysical data, can be placed in a wider environmental context. The composite para-stratigraphy for the Loch Ainort basin is dominated by Loch Lomond Stadial glacial activity. Terminal and readvance limits are identified at several localities within the basin. Variable morphological styles of the glacial sequences show that deglaciation occurred in two distinct, climatically controlled, phases. The first marked by a fluctuating ice margin and the second by uninterrupted retreat and in situ ice stagnation. Sub-aerially induced debris flows occur during the initial paraglacial phase but stabilisation of exposed slopes restricts this input and rapid sedimentation of fines from sediment-rich meltwaters becomes dominant. Modern fjordic sedimentation develops after the disappearance of glacier ice.
39
Lewis, Simon G. "The status of the Wolstonian glaciation in the English Midlands and East Anglia." Thesis, Royal Holloway, University of London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294920.
Full text
40
Thomson, Stephen Alexander. "Reconstruction of the Dimlington Stadial glaciation of Holderness, East Yorkshire, England : volume 1." Thesis, University of Glasgow, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272246.
Full text
41
Payne, Donald. "Late Quaternary glaciation in the Cordillera Occidental, Central Andes (16 to 22°S)." Thesis, University of Aberdeen, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287700.
Full textAbstract:
Glacial geomorphology contains information about former climate which is required for modelling global climate change. Most peaks over 5500 m in the Cordillera Occidental show signs of former glaciation although few at present support perennial ice. Cirque headwalls, large sub-parallel lateral moraines, terminal moraines and minor re-advance moraines were measured at six representative study sites, as were active and inactive rock glaciers. The largest sets of lateral moraines are assumed to have formed when glaciers were in equilibrium at the peak of the last glaciation, and a succession of minor re-advance moraines was probably deposited during retreat of the ice. The radiometric age determinations corroborate existing opinion that this retreat began in the central Andes around 14 000-11 500 years BP. Reconstructed former equilibrium lines on fourteen selected palaeo-glaciers range in altitude from 4625 m at 16°S to 4775 m at 22°S. Five methods of former ELA reconstruction were tested based on geomorphological evidence collected in the field. The results imply lowering of the ELA caused by lower temperatures and increased precipitation compared to the present. The maximum extent of glaciation in the Cordillera Occidental appears to have been reached late in the last glacier cycle because of a shortage of available moisture which inhibited glacier growth when temperatures were colder. Active rock glaciers appear to respond to the thermal rather than the hydric regime and terminate close to the 0°C isotherm which was 300 m lower during deglaciation than at present.
42
Lem, Rachael Elizabeth. "Oceanic, climatic and vegetation variability in Western Equatorial Africa since the penultimate glaciation." Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3028522/.
Full textAbstract:
Global temperatures are expected to rise by 2-2.5°C by the middle of the 21st century, posing a significant threat to human populations and the natural environment. Tropical West Africa has been classified as a highly vulnerable region; naturally-driven multi-decadal droughts are predicted to become more frequent and intense 20 years ahead of the global average. Examination of past records of large scale climate change is critical in order to validate climate models and mitigate against future global warming. This thesis examines the land-ocean interactions of a small-scale Western Equatorial African (WEA) river catchment and explores its potential as a record of regional and global climatic change during the Late Quaternary Period. Previous research has documented large-scale WEA climate change using marine cores offshore the Niger and Congo Rivers, however the response of the smaller, medially positioned, Ogooué River catchment remains to be investigated. In 2003, the IMAGES programme recovered 34 m of sediment, spanning the last 150 ka, from the Ogooué Fan, offshore Gabon. Geochemical, sedimentological, isotopic (δ¹⁸O and δ¹³C), trace element and palynological analyses were carried out. Three research objectives were established: (1) reconstruct the hydrological variability of the Ogooué River catchment through the identification of terrigenous fluvial discharge events; (2) explore the glacial and interglacial control of surface and bottom water δ¹³C in the Eastern Equatorial Atlantic (EEA); and (3) examine WEA vegetation biome changes in order to infer the drivers of past regional hydrological and climatic change. Sedimentological and geochemical investigations demonstrated the strong potential of using a Fe/Ti ratio and foraminiferal planktic δ¹⁸O as proxies for Ogooué River discharge variability. Ogooué discharge events were synchronous with the neighbouring Sanaga and Congo Rivers and were also concomitant with precessional maxima. A preliminary sea surface temperature (SST) reconstruction evidenced coeval SST and salinity responses to riverine discharge variability and highlights an opportunity to undertake further trace element analysis on the study material. Planktic and benthic δ¹³C stratigraphies were constructed in order to produce the first Δδ¹³C gradient record from a region of EEA not dominated by upwelling. Thermocline - bottom water Δδ¹³C evidenced an alternation of nutrient-poor North Atlantic Deep Water influx during glacial periods and nutrient-rich Antarctic Intermediate Water masses during interglacial periods. Locally, planktic d18O data support that precessionally driven riverine discharge events contributed to the δ¹³C of the planktic foraminifera Globigerinoides ruber (white variety). Finally, vegetation change in the Ogooué River catchment, and wider WEA, was documented through palynomorph reconstructions. Pollen data evidences a transition from grassland vegetation in glacial marine isotope stage (MIS) 6, through to more precipitation dependent lowland rainforest and swamp biomes from interglacial MIS 5 (~ 100 ka) to present day. High abundances of rainforest taxa in MIS 4-2 suggests rainforests remained as refugia facilitated by a weaker monsoon. The mangrove pollen, Rhizophora, is interpreted as an indicator of sea level change, with high abundances in MIS 5 and 1 evidencing sea level rise. Lastly, the Afromontane pollen Podocarpus, shows a strong correspondence with precession minima, suggesting alternating dominance of trade wind and monsoon intensity over the 23 ka precessional cycle.
43
Bolton, Clara Thérèse. "Orbital and suborbital climate variability during the Pliocene intensification of northern hemisphere glaciation." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/168995/.
Full textAbstract:
The late Pliocene is marked by the end of an interval of warm, relatively stable global climate and a secular shift into a bipolar glaciated world. The intensification of northern hemisphere glaciation (iNHG) central to this climatic transition was accompanied by a decrease in atmospheric carbon dioxide concentrations and commenced around 3.5 million years ago. The climate forcing and response mechanisms involved in the iNHG are subjects of ongoing debate in the palaeoclimate literature. In this thesis, I reconstruct palaeoproductivity and suborbital climate fluctuations during this important interval, with particular focus on the first three consecutive, large, obliquity-paced glacial-interglacial cycles (marine isotope stages, MIS, 101-95), using proxy methods applied to deep-sea sediments in the equatorial oceans and the North Atlantic. In this way, I evaluate the forcing mechanisms, biogeochemical cycles and climate implications during the late Pliocene. In Chapter 2, palaeoproductivity is reconstructed in the western and eastern equatorial Pacific Ocean. Data reveal that productivity fluctuations are in phase between east and west and are obliquity-paced. This implicates high-latitude rather than local forcing of export productivity and no apparent role for east-west thermocline tilting on these timescales, as previously proposed. In Chapter 3, multi-proxy palaeoproductivity reconstructions in the eastern equatorial Pacific and Atlantic Ocean upwelling zones are considered in terms of proxy applicability and export productivity. Results suggest that alkenone accumulation may be a useful indicator of export productivity and that the late Pliocene biological pump was stronger during glacials than interglacials. In Chapter 4, an inferred secular productivity shift is investigated using calcareous nannofossil assemblages. Assemblage shifts at an equatorial Pacific and a North Atlantic Ocean site support the interpretation of an increase and a decrease in export productivity, respectively. Implications of a strengthened tropical biological pump at this time are considered. In Chapter 5, high-resolution climate records are used to investigate suborbital variability at North Atlantic Integrated Ocean Drilling Program Site U1313. Data indicate that only smallamplitude suborbital variability occurs during the late Pliocene, with no amplification within the boundary conditions and inferred ice-volume variations of MIS 103 to 95.
44
Bourahrouh, Ahmed. "Chitinozoaires et palynomorphes de l'ordovicien supérieur nord-Gondwanien : impact de la glaciation ashgillienne." Rennes 1, 2002. http://www.theses.fr/2002REN10051.
Full textAbstract:
Pour évaluer l'impact de la glaciation ashgillienne sur les microfossiles organiques nord-gondwaniens, 156 échantillons prélevés, à limite Ordovicien-Silurien, en Algérie, Maroc, République tchèque et le Massif armoricain ont été analysés. Les crises fauniques du Permo-Trias et Frasnien-Famennien sont brièvement discutées. La biostratigraphie des coupes, basée sur les chitinozoaires, pour fixer la chronologie des événements recensés a été réalisée. L' essentiel de l'étude porte sur la quantification et l'interprétation du comportement du plancton sous les effets d'un stress climatique majeur. Trois périodes principales de fluctuations de la biodiversité et de l'abondance ressortent dans les assemblages de ces microfossiles. La période pré-glaciaire accuse une forte abondance et diversité de ces derniers. La période glaciaire se traduit par l'appauvrissement des populations de chitinozoaires, d'acritarches et sphaeromorphes. Aucune extinction massive en lien direct avec la glaciation n'est enregistrée. La période post-glaciaire enregistre un regain de diversité. La récupération faunique silurienne est perturbée par l'anoxie.
45
Nealon, John S. "Pre-Illinoian Glaciation and Landscape Evolution in the Cincinnati, Ohio / Northern Kentucky Region." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1367940441.
Full text
46
Colleoni, Florence. "La glaciation de la fin du Saalien (160-140 ka) : modélisation du climat." Phd thesis, Grenoble 1, 2009. http://www.theses.fr/2009GRE10131.
Full textAbstract:
Ce travail se concentre essentiellement sur le glaciation de la fin du Saalien (160 -140 ka) en Eurasie. Les résultats du projet Quaternary Environment of the Eurasian North montrent que durant cette période, la calotte Eurasienne était plus grosse que durant le Dernier Maximum Glaciaire (LGM, 21 ka). Les paramètres orbitaux de ces deux périodes étaient différents alors que les concentration de gaz à effet de serre étaient identiques. Afin de comprendre comment cette calotte a pu atteindre cette taille en Eurasie durant la fin du Saalien, nous avons utilisé un modèle de circulation générale atmosphérique (AGCM), un AGCM couplé à une couche mixte océanique ainsi qu'un modèle de végétation pour explorer l'influence des paramètres régionaux, des températures de surface océaniques et des paramètres orbitaux sur le bilan de masse en surface (SMB) de cette calotte Saalienne. A 140 ka, les lacs proglaciaires, la végétation et les températures océaniques simulées refroidissent le climat régional, diminuant l'ablation le long des marges Sud. Les dépôt de poussière au contraire, réchauffent le climat. La présence d'un ice-shelf dans l'Océan Arctique durant le MIS 6 n'affecte pas le SMB de la calotte eurasienne. Selon les données géologiques, la calotte Saalienne avait atteint sa taille maximale avant 160 ka. L'insolation d'été dans les hautes latitudes montre un pic très net vers 150 ka. La climat simulé avant 140 ka est plus humide et l'ablation le long des marges sud est plus importante bien que le SMB reste positif. La calotte Saalienne semble avoir été suffisamment grosse pour générer son propre refroidissement régional et se maintenir en Eurasie jusqu'à la Terminaison II (130 ka)<br>This thesis focuses on the glaciation of the Late Saalian period (160 -140 ka) over Eurasia. The Quaternary Environment of the Eurasian North project evidenced that during this period, the Eurasian ice sheet was substantially larger than during the entire Weichselian cycle and especially than during the Last Glacial Maximum (21 ka, LGM). The Late Saalian astronomical forcing were different than during the LGM while greenhouse gas concentrations were similar. To understand how this ice sheet could have grown so large over Eurasia during the Late Saalian, we use an Atmospherical General Circulation Model (AGCM), an AGCM coupled to an oceanic mixed layer and a vegetation model to explore the influence of regional parameters, sea surface temperatures (SST) and orbital parameters on the surface mass balance (SMB) of the Late Saalian Eurasian ice sheet. At 140 ka, proglacial lakes, vegetation and simulated Late Saalian SST cool the Eurasian climate, reducing the ablation along the southen margins. Dust deposition on snow have the opposite effect. The presence of a Canada Basin ice-shelf during MIS 6 in the Arctic Ocean, does not affect the mass balance of the ice sheet. According to geological evidences, the Late Saalian Eurasian ice sheet reached its maximum extent before 160 ka. Northern Hemisphere high latitudes summer insolation shows a large insolation peak towards 150 ka. The simulated climate prior to 140 ka is milder and ablation is larger along the southern margins of the Eurasian ice sheet although the mean annual SMB is positive. The Late Saalian Eurasian ice sheet, may have been large enough to generate its own cooling needed for its maintenance over Eurasia
47
Colleoni, Florence. "La glaciation de la fin du Saalien (160 - 140 ka): modélisation du climat." Phd thesis, Grenoble 1, 2009. http://tel.archives-ouvertes.fr/tel-00418445.
Full textAbstract:
Ce travail se concentre essentiellement sur le glaciation de la fin du Saalien (160 -140 ka) en Eurasie. Les résultats du projet Quaternary Environment of the Eurasian North montrent que durant cette période, la calotte Eurasienne était plus grosse que durant le Dernier Maximum Glaciaire (LGM, 21 ka). Les paramètres orbitaux de ces deux périodes étaient différents alors que les concentration de gaz à effet de serre étaient identiques. Afin de comprendre comment cette calotte a pu atteindre cette taille en Eurasie durant la fin du Saalien, nous avons utilisé un modèle de circulation générale atmosphérique (AGCM), un AGCM couplé à une couche mixte océanique ainsi qu'un modèle de végétation pour explorer l'influence des paramètres régionaux, des températures de surface océaniques et des paramètres orbitaux sur le bilan de masse en surface (SMB) de cette calotte Saalienne.<br /> A 140 ka, les lacs proglaciaires, la végétation et les températures océaniques simulées refroidissent le climat régional, diminuant l'ablation le long des marges Sud. Les dépôt de poussière au contraire, réchauffent le climat. La présence d'un ice-shelf dans l'Océan Arctique durant le MIS 6 n'affecte pas le SMB de la calotte eurasienne. Selon les données géologiques, la calotte Saalienne avait atteint sa taille maximale avant 160 ka. L'insolation d'été dans les hautes latitudes montre un pic très net vers 150 ka. La climat simulé avant 140 ka est plus humide et l'ablation le long des marges sud est plus importante bien que le SMB reste positif. La calotte Saalienne semble avoir été suffisamment grosse pour générer son propre refroidissement régional et se maintenir en Eurasie jusqu'à la Terminaison II (130 ka).
48
Straathof, Gijsbert Bastiaan. "Neoproterozoic low latitude glaciations : an African perspective." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/9607.
Full textAbstract:
The Neoproterozoic is one of the most enigmatic periods in Earth history. In the juxtaposition of glacial and tropical deposits the sedimentary record provides evidence for extreme climate change. Various models have tried to explain these apparent contradictions. One of the most popular models is the Snowball Earth Hypothesis which envisages periods of global glaciations. All climatic models are dependent on palaeogeography which as yet remains poorly constrained for the Neoproterozoic. This thesis presents a multidisciplinary study of two Neoproterozoic sedimentary basins on the Congo and West Africa cratons including radiometric dating of glacial deposits themselves. In the West Congo Belt, western Congo Craton, a new U-Pb baddeleyite age for the Lower Diamictite provides the first high quality direct age for the older of two glacial intervals. This age is significantly different from previously dated glaciogenic deposits on the Congo Craton. This result strongly suggests that the mid-Cryogenian was a period during which several local glaciations occurred, none of which were global. While the palaeomagnetic results from carbonates around the younger glacial interval are probably remagnetised, detrital zircon and chemostratigraphic results allow correlation with numerous late-Cryogenian glaciogenic deposits worldwide and a Snowball Earth scenario is favoured here. In the Adrar Sub-Basin of the vast Taoudéni Basin, West Africa, the terrigenous Jbeliat glacial horizon has been studied in great detail. Detrital zircon geochronology reveals large changes in provenance through this glacial unit with implications for sedimentological approaches and techniques for provenance characterisations based on one sample alone. Together with recently published U-Pb data these results constrain the age of the Jbeliat Group to a narrow window providing vital geochronological information for this younger glacial event. Combining provenance geochemistry, chemostratigraphy and U-Pb dating has greatly improved our understanding of two of the largest Neoproterozoic sedimentary basins. The dominance of Mesoproterozoic detrital material, for which no source has been reported near either of the field areas, has consequences for the proximity of other cratons at the time of deposition, prior to the final amalgamation of Gondwana.
49
Sutton, Brian. "Glacial landforms and sedimentology and Late Pleistocene evolution of the Mourne Mountains, Northern Ireland." Thesis, University of Ulster, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267825.
Full text
50
Banks, Maria Elaine. "Glacial Processes and Morphologies in the Southern Hemisphere of Mars." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/193842.
Full textAbstract:
Understanding the history of ice on Mars provides important insight into Martian geologic and climatic history. A model capable of ice reconstruction that requires few input parameters, and a detailed analyses of landforms in an area with hypothesized glacial modification, Argyre Planitia, provide further understanding of Martian ice.A threshold-sliding model was developed to model perfectly-plastic deformation of ice that is applicable to ice bodies that deform when a threshold basal shear stress is exceeded. The model requires three inputs describing bed topography, ice margins, and a function defining the threshold basal shear stress. The model was tested by reconstructing the Greenland ice sheet and then used to reconstruct ice draping impact craters on the margins of the Martian South Polar Layered Deposits using a constant basal shear stress of ~0.6 bars for the majority of Martian examples. This result is ~1/3 the value calculated for the Greenland ice sheet. Reasons for the lower Martian basal shear stress are unclear but could involve the strain-weakening behavior of ice. The threshold-sliding model can be used for ice reconstruction and forward modeling of erosion and deposition to provide further insight into the history of ice on Mars.To test the glacial hypothesis in the Argyre region, landforms are examined using images from the High Resolution Imaging Science Experiment (HiRISE) camera and other Martian datasets. Linear grooves and streamlined hills are consistent with glacial erosion. Deep semi-circular embayments in mountains resemble cirques. U-shaped valleys have stepped longitudinal profiles and tributary valleys have hanging valley morphology similar to terrestrial glacial valleys. Boulders blanketing a valley floor resemble ground moraine. Sinuous ridges cross topography, have layers, occur in troughs, and have variations in height that appear related to the surrounding surface slope; these are characteristics consistent with terrestrial eskers. At least portions of Argyre appear to be modified by ice accumulation, flow, erosion, stagnation and ablation. The type and amount of bedrock erosion and presence of possible eskers suggests the ice was, at times, wet-based.