The Younger Dryas was the last period during which glaciers shaped large parts of the Scottish landscape. Reconstructing the palaeoclimate and glacial processes that operated during this time is crucial for the understanding of past atmosphere-cryosphere interactions and predicting future climate change. This thesis presents results from geomorphological and geological mapping in the NW Highlands of Scotland that have resulted in the reconstruction of a Younger Dryas ice cap. Reconstruction of equilibrium-line altitudes and palaeo-precipitation values suggest that the Scottish west coast was wetter than at present. Detailed sedimentological analyses of "hummocky moraines" allow the modes of moraine formation to be reconstructed in great detail and existing models to be tested. "Hummocky moraines" largely represent terrestrial ice-contact fans consisting of supraglacial debris flows and intercalated glaciofluvial units indicating an ice-marginal mode of formation. Different stages of deformation in these fans indicate highly dynamic glaciers that oscillated during retreat, partly or completely overriding previously formed landforms during readvances. Clast shape analyses reveal that debris was mostly subglacially derived and transported. The evidence is incompatible with a morphological model according to which the moraines could be formed by englacial thrusting. Comparison with modem glacial landsystems indicates the following similarities with Scottish Younger Dryas glaciers. Low winter temperatures are similar to those on Svalbard, the marginal response of Younger Dryas glaciers to temperate environments and the modes of deposition to less responsive debris-covered glaciers. High precipitation along the Scottish west coast probably suppressed continuous permafrost development and caused high mass turnover and very dynamic, dominantly temperate Younger Dryas glaciers. Only a narrow zone around the margins appears to have been frozen to the ground, aiding elevation of basal debris and rapid deposition near the snout. The specific climatic and glaciological conditions during the Younger Dryas appear not to have a single modem analogue.

Abstract The mineralogy and geochemistry of the fine and clay fractions of till in different moraine types and in different bedrock areas in northern Finland have been studied. A total of 250 till samples from 140 test pits were studied mineralogically and geochemically. X-ray diffraction, differential thermal and thermogravimetric analyses, transmission electron microscopy, X-ray fluorescence and atomic absorption spectrometry were used as analytical methods. In the clay fraction of till quartz, plagioclase, microcline and amphibole are the primary minerals occurring. The clay minerals proper include vermiculite, chlorite, illite, swelling-lattice vermiculite and mixed-layer clay minerals. Kaolinite occurs most abundantly in the clay fractions of till in the Kittilä, Jerisjärvi, Kaaresuvanto and Pulju areas. In the clay fraction of Kittilä and Jerisjärvi illite is dioctahedral type, but in their of other study areas both di- and trioctahedral types occur. Kaolinite and dioctahedral illite are evidence of the mixing of the weathered bedrock material into the till matrix. In the fine fraction of till most abundant minerals are primary minerals and clayminerals are in a minor role. In the clay fraction of till the content of primary minerals are at higher and secondary minerals are at lower level in the Granitic and Archaean gneiss areas than in the Greenstone Belt, Svecokarelian schists and gneiss and Granulite areas. Amphibole, microcline and plagioclase occur in very low amounts or are totally destroyed by chemical weathering in the clay fraction of the till in the Kittilä area. The mineral composition of fine and clay fractions in the tills of northern Inari gives an indication that there occur much more mafic volcanites than is known today. The mineralogical compositions of fine fraction of the tills correlates quite well with the underlying bedrock in all study areas, but clay fraction does not. Geochemical results are in accordance with the mineralogical composition of both fractions. In the fine fraction of the till Si, Ca and Na contents are higher than in the clay fraction. Clay fraction is enriched in Al, Fe, Mg, K and trace elements as compared to the fine fraction. Present study material points out that the distribution of chemical elements in the clay fraction of the till does not correlate with the composition of the underlying bedrock, but fine fraction does so with a few exceptions. The chemical composition of till in Kaaresuvanto and Inari does not fully correspond to the composition of the underlying bedrock as known today. In northern Inari and Kittilä the results give an indication that there are more mafic volcanites and/or sulphide mineralizations occurring in these areas than is known at the present time. The most important factors controlling the mineralogical and geochemical composition of the fine and clay fractions of the tills in northern Finland are the composition of the bedrock and the possible occurrence of an old weathering crust. The final grain size composition of the tills and consequently the quantitative proportions of the different minerals are often related to the last glacial quarrying and sorting processes; therefore the mineralogical composition of the tills is to a certain extent bound also to the respective moraine type.

Five periods of ice advance in the North Klondike-upper Blackstone basins of the Ogilvie Mountains are recognized by the downvalley sequence of progressively older moraines. The youngest occurred during the last millennium and is represented by glacierets and fresh moraines. The other advances are of the Pleistocene Epoch; from youngest to oldest they are: Age I (valley glacier stage), Age II (transection glacier), Age IIA (transection glacier with piedmont) and Age III (mountain ice cap). Evidence for Age III is limited to the north slope of the ranges. Age IIA was recognized only on the north slope and may represent a slightly older pulse of the Age II. This chronosequence is tentatively correlated with those elsewhere in the northern Cordillera. Within the region an array of surficial elements indicates that a continuous and discontinuous mosaic of processes have operated interdependently during the Quaternary. A product of these processes is mapped under one of eight facies - attention being directed to the varieties of features associated with the glacial and periglacial cycles. Of the latter, active, inactive and degradational forms exist. Strong correlations between the distribution of some types of surficial features and the underlying bedrock geology are recognized. No changes in morphology, permafrost distribution, pebble weathering, pedogenesis and floral succession could be related to the ages of the Pleistocene moraines. The influence of permafrost on all ages of moraines, the variability in their environment of deposition, and an edaphic and climatic discontinuity produce greater differences than does the age factor. In the northern half of the study area, permafrost and associated phenomena were observed to greatly retard chemical alteration; on the other hand, they permit the development of only a vegetational and pedological "polyclimax", rather than a single mesic climax, in a time span of less than 11,000-15,000 years. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

By only considering records of climate and glaciers over the period that humans have been monitoring them, one might think that climate normally changes quite rapidly, and that glaciers have always been small. But in the not-so-distant past, an ice sheet covered the Southern Andes, flowing across the southern tip of the continent, and in some places, even terminating into the Atlantic Ocean. Glaciers rewrite the surfaces they inhabit, leaving behind indicators of their past behavior. By studying the landforms they create, we can reconstruct climates of the past. Here I present unique and novel glacier-climate reconstructions over southern and central Patagonia using a state-of-the-art dating approach tied to high resolution spatial mapping and glaciological modeling. The main goal of this thesis is to constrain the precise timing and character of the past advances of three glaciers in Patagonia. To this end, I present new precise 10Be surface exposure datasets from two paleo outlet glacier lobes (at 45°S and 53°S), totaling 71 new moraine boulder ages. In these two valleys, I am able to reconstruct the last three major glaciations (MIS 6, 4, 2), as well as provide a constraint for the last two terminations (T1, T2). At a third site, I create a novel dataset to reconstruct the behavior of the Calluqueo glacier (48°S) from ~7,000 years ago to the present. All three sites are eastwards of the main Andes mountain range, spanning from southernmost Patagonia (53°S) to central Patagonia (45°S). To achieve my thesis objectives, I employed recent improvements in the 10Be exposure dating method, and tied the geochronological studies to new, high resolution maps of the glacial geomorphology created by the former glaciers and associated processes. We find in central Patagonia, the Ñirehuao glacier lobe was most extensive potentially during Marine Isotope Stage (MIS) 8, but certainly prior to MIS 6, followed by a major advance during MIS 6. This study presents one of the first directly dated records of a MIS 6 glacier expansion in Patagonia at 153±5.1 ka, where the glacier may have been in retreat at 137±4.2 ka. During the last glacial cycle, the glacier was most extensive during the middle of MIS 2, at 23.6±0.9 ka. The southernmost section of the Ice Sheet, at Estrecho de Magallanes, was more extensive during Marine Isotope Stage 4 (MIS 4) than during MIS 2, representing the first direct dating of the MIS 4 glacier culmination in South America. Similar to the MIS 2 glacial maximum, within MIS 4 there were multiple advances that we date (6 samples) to between 67.5±2.1 and 62.1±2.0 ka. Inboard of the MIS 4 moraine complex, we date a sequence of geomorphically distinct MIS 2 moraines that represent separate major periods of glacial stability. The MIS 2 maximum extent occurred by 27.4±0.8 ka and was followed by at least four more full glacial culminations over a hundred miles beyond the Andes mountains. About 18 km inboard of the main MIS 2 landforms, the sequence is followed by smaller-scale recessional moraine crests that we date to 18.0±0.8 ka, indicating the glacier was in net retreat at this time. In order to estimate the climate conditions necessary to drive the glacier advances that we date and map, we apply the University of Maine Ice Sheet Model to the Estrecho de Magallanes and Ñirehuao records. Tentative results suggest that the Magallanes lobe may have reached mapped inner and outer MIS 2 moraines with a climate that had approximately 4.5°C and 5.5°C cooler summers, respectively, assuming about 25% less annual precipitation relative to modern conditions. A new record at Calluqueo, in central Patagonia, allows us to reconstruct Holocene (interglacial) glacier changes. Using 33 new 10Be ages with unprecedented precision, geomorphic mapping and historical imagery, we find that the Calluqueo glacier sat at its mid-Holocene maximum extent from ~6,900 until ~6,700 years before the present. Major moraine forming advances subsequently culminated at least seven more times, averaging every 500±31 years, between 5,620±203 and 3,120±106 years ago. A hiatus in moraine formation occurred from 3,120±106 until 1,160±50 years ago (860 CE). Major retreat occurred between 1600-1800 CE, followed by stability from 1800-1940 CE, and pronounced ongoing retreat since after 1940 CE. For the Holocene period, this record represents one of the first precise, directly-dated glacier histories from central Patagonia, and one of the few available for all of Patagonia. The timing of advances of the Calluqueo glacier has little in common with the glacial histories from the Northern Hemisphere, suggesting an inter-hemispheric asynchronicity. All together, we reconstruct the timing of glacial maxima at three sites in terrestrial Patagonia from 53°S to 45°S, with unprecedented precision, from pre-MIS 6 to the present day.

No description available.

Ce mémoire expose les résultats d'analyses sédimentologiques effectuées sur des sédiments d'origine fluvio- glaciaire quaternaire de la plaine de Bièvre-Valloire, en Bas- Dauphiné . (Carte géologique au l/80.000ème, feuilles de Saint-Etienne (177) et Grenoble (178) . Mon travail étant sédimentologique, je me suis basée sur la stratigraphie de ces dépôts établie par F. BOURDIER dans sa thèse (1961) . J'ai récolté des échantillons des différents faciès de chacune des périodes qu'il distingue, au cours des étés 1960, 1961, 1962 .

Le but de ce travail est de reconstituer l'histoire du Quaternaire récent de la Haute Vallée de l'Arc. Deux unitées morphologiques et stratlgraphlques sont distinguées dans le baasln de Bessans : l"Ecroulement de la Madeleine" composé de formations diverses ; la "Cuvette de Bessans" presqu'entlèrement remplie de sédlments lacustres découpées en terrasses de niveaux multlples. Au Nord du bassin les moralnee du VIllaron marquent un stationnement du glacler de l'Arc. Dans le bassln de Lanslebourg, le verrou de Lenslevillard indique un autre stationnement glaciaire. La stratigraphle du bassin de Lanslebourg montre quelques eédlmenta lacustres qui disparaissent vers l'amont sous une formation fluviatile épaisse (cailloutis de Lanslebourg) surmontée de dépôts torrentlels. Dana le bassin de Bramans-Termignon sont conservées les traces de deux statlonnements du glacier du Doron (Solllères et Fontalgnous). Sur les moraines, reposent des alluvions deltaïques couronnées par les cailloutis de Solllères et les alluvions torrentlelles. La description des formos d'érosion et d'accumulation au cours du Quaternalre récent permet d'établir la chronologie suivante: 1. Statlonnement glaciaire de Lanslevlllard (Arc) et des Fontalgnous (Doron), et lac de Lanslebourg. 2. Episode lacustre du Verney pendant le recul des fronts glaciaires entre deux statIonnements. 3. Stationnement glaciaire du Villaron et des Fontalgnous accompagné du dépôt das cailloutis. 4. Alluvionnement torrentiel, façonnement des hautes et basses terrasses, écroulement de la Madelelne et épisode lacustre de Bessans. 5. Evolution finale: creusement du lit actuel de l'Arc et dépôt dea formations de versants. Seule la dernière étape paléogéographlque serait holocène, les 4 autres se situeralent à la fin du retrait wurmien et durant le Tardlglaclalre.

Gerard De Geer was the first one to identify De Geer-moraines, and has since then been mapped by many other studies around the world.  The focus of this study was to examine the environment the ridges form in, regarding the water depth during creation, the importance of topography and the melting rate of the ice. Using airborne Light Detection and Ranging  (LiDAR) data, De Geer- moraines were mapped around eastern Norrbotten county, including Piteå, Boden and Luleå. A total of 14 651 De Geer-moraines were identified over the selected area. Six parameters were analysed during this study; length, orientation, steepness, distance between ridges, current ground level and depth below highest shoreline. In some areas, ridges showed a high, local steepness, while other study sites showed ridges with a varied interconnected form, from straight, to convex and concave. Prominent De Geer-moraines had been identified, where the mean distance between the ridges was calculated to 345 m. Furthermore, other glacial formations (drumlins, flutings, rogen moraines and eskers) showed a relationship to De Geer-moraines, either with a similar angle or a perpendicular relation. A great water depth showed a significant role in the creation of the ridges, with 75% of the identified De Geer-moraines formed in a water depth greater than 150 m. De Geer- moraines found on topographic lows tend to have an interconnected concave form, while over or close to elevated areas; they’re slightly convex. The mean distance between prominent ridges showed a connection to the average retreat rate of the last ice, which suggests that prominent ridges had been formed annually.

Glacial till from the Mt. Achernar moraine (MAM) records pre- and post- last glacial maximum (LGM) compositional variability of an East Antarctic moraine sequence through time and space. Pebble lithology, detrital zircon geochronology, and till geochemistry were analyzed on samples from a 6.5 km transect. Hummocky topography occurs with the most recently exposed material along the active ice margin (Zone 1), followed by a relatively flat and low region (Zone 2), and then a series of ~2 m high parallel/sub-parallel ridges and troughs accompanied by distinct color changes that are directly related to the dominant lithology of the region (Zones 3–5). Zone 3 is dominated by ~38% more sedimentary rocks than adjacent zones and has an overall shape of a broad arch superimposed with smaller ridges. Zone 4 is composed of distinct colored bands that alternate between dominant sedimentary and mafic igneous lithologies. These dominant sedimentary and intermediate/mafic igneous rocks for all Zones are interpreted to be primarily the Beacon and Ferrar Supergroup rocks respectively. The U/Pb data from the till is consistent with a Beacon Supergroup source as samples consistently show significant populations from the Permian ~250-260 Ma, the Proterozoic ~565–600 Ma, ~950–1270 Ma, and ~2300-2320 Ma, as well as (and) the late Archean ~2700-2770 Ma. The Pagoda, Mackellar, Buckley, and Fremouw Formations are potential sources of the detrital zircons. When paired with surface exposure ages, the U/Pb data indicates that the debris source has been consistent over the past ~555 ka, implying relatively stable ice sheet behavior. However, ice sheet change is indicated by a trim line present on Mt. Achernar that can be traced back to the boundary between Zones 3 and 4, as well as a change in pebble lithology, geochemistry, and morphology of Zone 3. Zone 3 records a time of ice sheet thickening and a change in provenance during the LGM. Zone 4 is pre-LGM, Zone 2 records deglaciation, and Zone 1 is still actively connected to the Law Glacier. This study reveals the broader importance of using multiple provenance techniques when interpreting provenance changes in till over time.

This thesis investigates the origin, sedimentological characteristics, and paleoglacial significance of large latero-frontal moraines and moraine-dammed glacial lakes and their potential to generate glacial lake outburst flood (GLOF) events in the Cordillera Blanca, Perú and Iceland. This topic is particularly important as the potential for GLOF events in high altitude regions is increasing as ongoing global climate warming causes rapid glacier recession and the growth of lakes impounded by unstable moraines. The first chapter of this thesis introduces the characteristics of moraine dammed lakes and GLOFs and provides details of the study areas in Perú and Iceland that were selected for this work (Chapter 1). Chapter 2 investigates the glacial history of the Cordillera Blanca, Perú through the compilation, mapping, and analysis of dated moraines in the region. The formation of moraines by different glaciers in the same region at approximately the same time is interpreted to indicate a period of regional climate conditions that were favourable for glacier expansion and/or equilibrium. Six stages of glacial activity are identified from this analysis, ranging in age from older than 35 thousand years (Stage 1) to modern (Stage 6). The third chapter of this thesis identifies the geomorphic and sedimentologic characteristics of a moraine-dammed supraglacial lake (Llaca Lake) in the Cordillera Blanca, Perú. The combined use of imagery collected with an uncrewed-aerial vehicle (UAV), field sedimentological observations and geomorphological mapping allowed the creation of a landsystem model that summarizes the current geomorphic and sedimentologic environment of Llaca Lake (Chapter 3). This is the first study to describe the landform-sediment assemblages in a tropical moraine-dammed supraglacial lake and provides a framework for further landsystem analysis of growing supraglacial lakes that are at risk of GLOF events. The fourth chapter of this thesis describes the sedimentary architecture of the eastern lateral moraine of Gígjökull in southern Iceland. An uncrewed-aerial vehicle was used to acquire high resolution photographs of an exposure through the lateral moraine that allowed the identification of seven lithofacies types and three lithofacies associations. Documentation of the sedimentary architecture of the eastern lateral moraine of Gígjökull enhances understanding of moraine development and the identification of areas of hydrogeological weakness that can reduce the structural integrity of the moraine. The research findings presented in this thesis utilize a glacial sedimentological and geomorphological approach to investigating the relationship between current and past glacial processes in the study areas, and the role that these processes play in determining the characteristics and stability of large ice marginal moraines that impound glacial lakes. This work also furthers our understanding of the dynamic surface processes at work in high altitude regions such as the Cordillera Blanca. Identifying and determining the relationships between current and past processes, sediments and landforms will enhance understanding of the role of large moraines damming glacial lakes in other high-altitude regions such as the Himalayas, British Columbia, Patagonia, and New Zealand and the associated risk of GLOF events. / Thesis / Doctor of Science (PhD)