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Palaeoglacier margins from the Zanskar Range of the north-western Indian Himalaya are reconstructed through geomorphological mapping and sedimentology. These are dated ilsing Optically Stimulated Luminescence (OSL) techniques on quartz extracted from related fluvioglacial and lacustrine deposits. A glaciated palaeosurface with broad, gentle slopes >280m above river level and high grade metamorphic erratics represents the oldest and most extensive glaciation, the Chandra Stage. This formed an ice-cap with its ice-shed to the south over the High Himalaya. A change from broad glacial troughs to narrow V -shaped gorges along with large subdued moraine ridges and drift/erratic limits defines an extensive valley glaciation, the Batal Stage, with its maximum close to -78.0±12.3ka BP (Oxygen Isotope Stage (OIS) 4). Distinct sets of moraine ridges represent a less extensive glaciation, the Kulti Stage, which is dated to shortly after the global Last Glacial Maximum (OIS 2) and a minor advance, the Sonapani, is represented by sharp crested moraine ridges < 2km from current ice bodies. The change in glacier extent and style from the Chandra Stage to the later glaciations may be related to uplift of more southerly ranges blocking monsoon precipitation and incision of the landscape such that ice reached lower altitudes over shorter horizontal distances. Batal and Kulti Stage Glacier Elevation Indexes (GEls) calculated for this and adjacent areas increase from south-west to the north-east, but decrease again towards the Indus valley, reflecting attenuation of the south-westerly monsoon and possible channelling of westerly depressions along the broad upper Indus valley. GEl values were depressed by ~500m during the Batal Stage and -300m during the Kulti Stage. Six new OSL age estimates from the Zanskar Range greatly improve the glacial chronology of the north-west Himalaya and reinforce the emerging asynchrony between this region and the Central and Eastern Himalaya, which experienced its maximum glaciation during OIS 2 rather than OIS 4. Improved glacier mass balance data, palaeoclimatic proxy data for the summer monsoon and particularly the winter westerlies, and numerical age estimates from Himalayan glaciers are required to explain this asynchronous maximum.

The Loch Lomond Advance limits and raised marine shorelines in N. W. Argyll have been mapped and surveyed. Radiocarbon dated Lateglacial and Postglacial pollen sites at Salen and Loch Shiel provide the vegetational history and chronology for the area. 14 Loch Lomond Advance glacier termini and associated limits were mapped using the distribution of hummocky and fluted moraine, together with a survey of erratic boulders. 83% of the reconstructed former glaciers had a southerly aspect relating to southerly snow-bearing winds. The average firnline gradient was 7.5m/km increasing in altitude towards the north-east; the average firnline height for the area was 369m. The Main Lateglacial Shoreline, formed during the Loch Lomond Stadial, slopes towards 270 with a gradient of 0.15m/km from 9m in the east to Om in the west of the area. It was formed by freeze-thaw action operating under exceptional conditions, and its formation was influenced by rock type. Two Postglacial shorelines are recognized : the Main Postglacial shoreline that slopes towards 270, from 14m to 8m with a gradient of 0.06m/km, and a lower shoreline at approximately 5m which has no definite gradient. An absolute Lateglacial pollen site at Salen, Ardnamurchan, shows an early pioneer community of Rumex, Salix, Gramineae and Cyperaceae species being replaced by an Empetrum heath during the Lateglacial Interstadial. Subsequent stadial conditions are reflected by open herb communities and the onset of coarse minerogenic sedimentation. This minerogenic influx ceased around 10,000 to 9,700 B.P. with a rapid recolonization of the surrounding area by pioneer herbs, then dwarf shrub and finally deciduous woodland. Middle and Late Postglacial vegetational development is recorded by lacustrine sediments from Loch Shiel where the fossil pollen record shows that a mixed deciduous woodland of Quercus, Alnus, Betula and Corylus was progressively cleared by man. Palaeomagnetic and chemical records were obtained from the site. The Main Postglacial Transgression flooded Loch Shiel resulting in the deposition of shells of the marine bivlave Thyasira flexonosa.

Abstract The high Drakensberg of southern Africa has received considerable geomorphological interest during recent decades. In particular, there has been an ongoing debate concerning the accuracy of landform interpretations which propagate past glaciation and permafrost. This research examines the macro and micro-sedimentology of various deposits found in eastern Lesotho and compares them with possible geomorphological process origins such as debris flows, debris avalanches, mudflows, mudslides, landslides, solifluction deposits, rock glaciers, pronival ramparts, glacial moraines and fluvial deposits. The results support the contention that four of the deposits are moraines, formed by small glaciers, and one is a debris flow which was initiated by a small glacier. However, two further deposits indicate that localities in close proximity to the linear deposits experienced mass wasting, associated with past periglacial conditions. With the assistance of applying glacier reconstruction methods, modelling hillshade, the provision of new palaeoclimatic extrapolations, and correlation of deposits with contemporary snow patch distribution, it is demonstrated that the valley slope deposits are determined by a past climate that was within the glacial/periglacial equilibrium zone, and was influenced by specific topographic and associated micro-climatic thresholds. It is shown that macro-topographic factors (e.g. slope gradient, aspect etc) and summit altitude are critical factors determining whether slopes were influenced by periglacial (mass wasting) or glacial processes (small niche/cirque glaciers) in adjacent valleys.

The Gaskiers glaciation (c. 580 Ma) has been classically traced along the Neoproterozoic Avalonian-Cadomian Terranes, which are now found scattered around the North Atlantic Ocean. Around 625 Ma these terranes were composed of volcanoes and arc-type basins. ‘Till-like’ diamictite horizons identified within these basins have been used as evidence for a ‘Snowball Earth-type’ glaciation at 580 Ma. However, others argue that these deposits are non-glacial debris flow deposits. To test the non-glacial interpretation of these deposits, a detailed sedimentological and basin analysis was conducted on the Neoproterozoic Squantum Member that occurs conformably with the volcanic-sedimentary rocks of the Boston Bay Group (eastern Massachusetts); this deposit is one of the most referenced ‘tillite’ deposits for the Gaskiers glaciation. This thesis shows that the ‘tillites’ of this succession are volcanically-influenced non-glacial debrites. Using the Lesser Antilles Arc and the adjacent Grenada Basin in the Caribbean Sea as a modern depositional analogue for the Avalonian-Cadomian Terranes, this study further reveals that debris flow facies types (diamicts) comparable to those of the Avalonian-Cadomian Terranes are produced at this modern arc and are recorded in the fill of the Grenada Basin. A similar study was conducted on the modern diamicts produced at the heavily glaciated Mount Rainier volcano (Washington, USA), revealing that despite the presence of local glaciers, debris flow is the dominant process depositing diamicts due to eruptions and flood events. The major thrust of this thesis is that it highlights the key role of tectonics and volcanism, not glaciation, in producing the diamictites of the Avalonian-Cadomian Terranes, and the importance of examining Neoproterozoic diamictite facies in their wider sedimentary, stratigraphic and tectonic context.

The Gaskiers glaciation (c. 580 Ma) has been classically traced along the Neoproterozoic Avalonian-Cadomian Terranes, which are now found scattered around the North Atlantic Ocean. Around 625 Ma these terranes were composed of volcanoes and arc-type basins. ‘Till-like’ diamictite horizons identified within these basins have been used as evidence for a ‘Snowball Earth-type’ glaciation at 580 Ma. However, others argue that these deposits are non-glacial debris flow deposits. To test the non-glacial interpretation of these deposits, a detailed sedimentological and basin analysis was conducted on the Neoproterozoic Squantum Member that occurs conformably with the volcanic-sedimentary rocks of the Boston Bay Group (eastern Massachusetts); this deposit is one of the most referenced ‘tillite’ deposits for the Gaskiers glaciation. This thesis shows that the ‘tillites’ of this succession are volcanically-influenced non-glacial debrites. Using the Lesser Antilles Arc and the adjacent Grenada Basin in the Caribbean Sea as a modern depositional analogue for the Avalonian-Cadomian Terranes, this study further reveals that debris flow facies types (diamicts) comparable to those of the Avalonian-Cadomian Terranes are produced at this modern arc and are recorded in the fill of the Grenada Basin. A similar study was conducted on the modern diamicts produced at the heavily glaciated Mount Rainier volcano (Washington, USA), revealing that despite the presence of local glaciers, debris flow is the dominant process depositing diamicts due to eruptions and flood events. The major thrust of this thesis is that it highlights the key role of tectonics and volcanism, not glaciation, in producing the diamictites of the Avalonian-Cadomian Terranes, and the importance of examining Neoproterozoic diamictite facies in their wider sedimentary, stratigraphic and tectonic context.

The genetic structuring of populations can be influenced by present processes and past events. One of the largest historical events to affect the distribution and genetic characteristics of present-day North American biota is the Pleistocene glaciation. Thus, the study of post-glacial colonization patterns of species in northern landscapes can relay important ecological information, as species had to expand their range extensively following the retreat of the glaciers and are often at the terminal end of their expansion. These species consequently exhibit the genetic fingerprints of sequential founder events, in turn decreasing the genetic variation available for adaptation. Using amphibians to investigate post-glacial range expansion is advantageous, as they have limited dispersal abilities revealing fine-scale patterns and they are thought to be one of the first vertebrates to colonize post-glacial habitat. Therefore, to model the phylogeography of a primary colonizer and the population structure of anurans in northern landscapes, population genetics analyses of wood frogs (Lithobates sylvaticus) were performed in the James Bay area. Wood frogs were sampled from 17 localities around James Bay and genetic analyses were conducted with seven microsatellite loci and mitochondrial DNA sequences of the ND2/tRNATRP genes. Results show that the post-glacial recolonization of the James Bay area by wood frogs originated from the putative refugium in western Wisconsin, an area known as the Driftless Area. Two routes were taken by founders to colonize the James Bay area: one north-west of Lake Superior, colonizing western Ontario, and one through the Upper Peninsula of Michigan, colonizing southern and eastern Ontario and western Québec. Interestingly, the meeting of the two lineages south-west of James Bay led to the establishment of a zone of higher genetic variation than expected under the founder effect hypothesis. Additionally, population structure analyses revealed the segregation of three genetic populations east, north-west, and south-west of the bay, the latter showing the highest genetic variation and likely representing a zone of secondary contact. This study shows that past events such as post-glacial range expansions can explain present patterns of genetic variation and population structure, and that studies in northern landscapes may be very useful in understanding genetic patterns throughout the range of a species.

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.

Species long-term persistence is to a great extent contingent on the ability of populations to mount variable responses to perturbations; the breadths of which are largely dependent on the amount of heritable variation present at the population level. However, populations are not necessarily equivalent in their amount of genetic variation, or in their responses to future environmental conditions, and information about the magnitude and spatial distribution of intraspecific genetic variation is integral to conservation planning, and preserving species evolutionary potential. Using neutral molecular markers, I demonstrate that latitude is an important determinant of the amount and spatial distribution of genetic variation within and among Nearctic fishes. Latitudinal declines observed among species were mirrored by declines within species, and encourage a cautionary approach for interspecific comparisons and inferences of broad spatial patterns of genetic variation when data for individual species are obtained from only a portion of their range. I subsequently examined the magnitude and spatial distribution of microsatellite based variation for 33 spawning runs from across the range of American shad (Alosa sapidissima). Sequential reductions of intraspecific genetic variation with latitude were observed among spawning runs from formerly glaciated regions; consistent with stepwise post-glacial range expansion, and successive population founder events. Canadian populations exhibited temporally stable genetic differentiation characterized by a significant pattern of isolation by distance, and exhibited evidence of metapopulation structure. Although isolation by distance was observed among U.S. spawning runs, population structure was comparatively weak; a possible consequence of increased levels of gene flow (human-mediated or natural). Different spatial patterns of population structure were detected across the species’ range, but are not likely due to alternative reproductive strategies (iteroparity vs. semelparity). Rather, these different patterns probably reflect different management strategies in Canada (no stocking) and the United States (stocking), alternative glacial histories, or combinations thereof. Reciprocal patterns of genetic diversity and differentiation observed across the species’ range suggests that U.S spawning runs contribute more to diversity and less to differentiation than Canadian spawning runs. These results have implications for future shad restoration efforts, and the long-term persistence of the species.

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.