During the last glacial maximum (LGM), some 20 ka ago, northern Manitoba was situated beneath 3 to 4.5 km of ice, on the outer fringe of a major ice spreading center of the Laurentide Ice Sheet. The region has also been affected by major paleoglaciological changes linked to multiple source areas, migration of ice centres, and ice-sheet thickening/thinning over multiple glacial cycles. The net effect of this evolution is a very complex geological record, which has major implications for ice-sheet reconstructions and drift prospecting. Theory-based hypothesis for the region suggest initial advance-phase deposition was followed by either net-erosive or cold-based conditions for much of the glacial cycle. In contrast, observation-based reconstructions of ice-sheet behaviour consider the glacial landscape to have been predominately formed by near-complete overprinting during warm-based deglaciation. Some complexity has been recognized in sediment-landform records, but new insights into glacial dynamics and sediment-landscape evolution are needed. Systematic mapping (remote-sensing) and fieldwork (ice-flow indicators, till composition, ground truthing) in northeastern Manitoba has led to the recognition of spatio-temporal variability in landscape (streamlined-landform event-flowsets) and landform (micro and meso-scale ice-flow indicator records) and till composition inheritance. In particular, analysis of the spatio-temporal characteristics of the subglacial landscape led to the recognition of disjoint zones with internally-consistent assembly histories – termed glacial terrain zones (GTZ). These GTZ were then classified as (1) relict-glacial, (2) palimpsest, or (3) deglacial in nature. Generally, (1) is interpreted as pre-LGM, (2) may include pre-LGM terrain but also LGM to early deglaciation (ice margin still far from study area; ice sheet thinning phase) and (3) was formed during the final ice retreat phase. The resultant surface till composition within relict and palimpsest GTZs is a spatial mosaic interpreted to reflect variable intensities in modification (overprinting) and preservation (inheritance) of a predominately pre-deglacial till sheet. In these regions, streamlined landforms parallel to a known deglacial ice-flow orientation were unable to overprint the underlying inherited glacial sediment composition. Secondly, field investigations (sedimentology, clast fabrics, till composition, near-surface S-wave seismic surveys) have characterized the widespread Rogen moraine terrain. These transverse subglacial ridges are spatially associated with streamlined landforms, are situated on regionally low-lying terrain without topographic constraints and may have small bedrock ‘knob’ obstacles at their up-ice base. This thesis assesses Rogen moraine formation hypotheses within the new paleoglaciologic context of northern Manitoba, favours an instability mechanism for formation, and provides important field data against which further formation hypothesis should be tested. The main insight of this study is not a detailed reconstruction (local history), but rather a series of forms of evidence suggesting that the glacial history of the region is one of prevailing patchy low-erosion conditions which favored preservation of a fragmentary record of non-coeval and sometimes contrasting warm-based (more dynamic) conditions. Despite being near a thick inner-core region of the Laurentide Ice Sheet, where basal conditions are generally considered stable and meltwater availability is low, the hard-bed study area was subject to local spatio-temporal shifts in subglacial conditions that led to generation of a complex palimpsest glacial landscape. Spatial differences in the preservation of older streamlined landforms, variably drumlinized Rogen moraine and the concentrations of inherited subglacial detritus all culminate in a hypothesis that suggests the subglacial landscape was continually evolving and subject to spatio-temporal variations in the intensity of ice-bed processes throughout the last glaciation (subglacial bed mosaic). Based on the new glacial history, and a general lack of ice-marginal landsystems, most warm-based ice-flow phases likely occurred near LGM – with only weak overprinting during late deglaciation. The idea of landform generation at patches within a transient subglacial bed mosaic now allows for a close association between subglacial drumlins and Rogen moraine ridges, that may have formed by disconnected and not necessarily coeval or related processes. This mosaic, of slow to non-flowing basal ice (‘sticky regions’) and wet-based flowing-ice patches, also helps to explain preservation of immature landforms (Rogen moraine) and relict or palimpsest terrain. Sticky regions may have formed by at least two different mechanisms: localized heterogeneous switches in basal thermal regime (frozen-bed patches), or within a warm-based subglacial environment from wet to stiff, dewatered till.

Field study at seven Scottish sites has resulted in the following evidence for late- and post-glacial earthquakes and fault movements. a) Glen Roy, western Highlands: Earthquake-induced deformation structures are observed in 10,000 year-old lake deposits, and can be related to a surface fault rupture and several landslides. The deformation structures have been mapped over an area of 100 sq. km and display most intense deformation in a central area, with decreasing degrees of deformation in peripheral zones. This zonation is interpreted in terms of varying intensities of ground-shaking during a major earthquake. The field data indicate a magnitude 6.25 event. b) Kinloch Hourn, western Highlands: A prominent, 14-km long fault displays evidence for recurrent movement. A magnitude 5.5-6.0 event occurred between 3500 and 2400 years ago, and unquantified movement has occurred since then. c Firth of Lorn (west coast): Levelling survey, at two sites, indicates several vertical displacements of up to 3m, of a 10,000 year old raised shoreline. d) Lismore (west coast): Lateral fault displacements of c. 0.5m have disrupted present rock and soil morphology and indicate movement in the last few thousand years. e Tayside, eastern Scotland: Two sites display soft-sediment deformation structures in late-glacial sands and silts. The structures are interpreted as the result of (unquantified) earthquake ground-shaking. This field evidence is collectively evaluated in terms of crustal stress, earthquake recurrence and present-day earthquake hazard. Earthquakes as large as magnitude 7 are thought to have occurred but were probably triggered by glacial rebound stesses. Earthquakes upto magnitude 6 have certainly occurred, some as recently as 3000 years ago, and are likely to recur. Present-day surface fault displacements of up to 0.1m are considered likely on fractures favourably orientated with respect to the present-day stress field.

No description available.

A proper methodological approach of investigating Holocene sea level changes is a prerequisite in order that the sea-level index points can be useful and significant. This requires the correct identification of the indicative meaning. The indicative meaning of the sea level indicator is defined as the altitudinal relationship of the local environment in which it accumulated to the contemporaneous reference tide level. This study identifies the index points using the litho-, bio-, and chrono-stratigraphic approach. The sea level indicator is derived from the regressive contact of the intercalated peat and marine clastic sequence, while the indicative meaning is estimated based upon the relationship with the contemporary samples. The study was carried out at two contrasting coastal locations, the fossil sites from Meru and Mardi in Kelang in the west and Penur (north and south transects) in Kuantan in the east, while the contemporary sites are from various ecological environments from both areas. Microfossil analysis of pollen and diatoms indicates that the former are more applicable, and defined the changing microfossil assemblages within the regressive contact of the sea level indicator samples. Seven sea level index points are identified. The finding agrees to the general assumptions of high mid-Holocene sea level history in peninsular Malaysia. A relative sea level difference between the west and east coast is indicated, but the significance, if any, is dealt with caution. The explanations of presumed differential crustal movement or sheer age/altitude variability of the index points are suggested.

During the last glacial maximum (LGM), some 20 ka ago, northern Manitoba was situated beneath 3 to 4.5 km of ice, on the outer fringe of a major ice spreading center of the Laurentide Ice Sheet. The region has also been affected by major paleoglaciological changes linked to multiple source areas, migration of ice centres, and ice-sheet thickening/thinning over multiple glacial cycles. The net effect of this evolution is a very complex geological record, which has major implications for ice-sheet reconstructions and drift prospecting. Theory-based hypothesis for the region suggest initial advance-phase deposition was followed by either net-erosive or cold-based conditions for much of the glacial cycle. In contrast, observation-based reconstructions of ice-sheet behaviour consider the glacial landscape to have been predominately formed by near-complete overprinting during warm-based deglaciation. Some complexity has been recognized in sediment-landform records, but new insights into glacial dynamics and sediment-landscape evolution are needed. Systematic mapping (remote-sensing) and fieldwork (ice-flow indicators, till composition, ground truthing) in northeastern Manitoba has led to the recognition of spatio-temporal variability in landscape (streamlined-landform event-flowsets) and landform (micro and meso-scale ice-flow indicator records) and till composition inheritance. In particular, analysis of the spatio-temporal characteristics of the subglacial landscape led to the recognition of disjoint zones with internally-consistent assembly histories – termed glacial terrain zones (GTZ). These GTZ were then classified as (1) relict-glacial, (2) palimpsest, or (3) deglacial in nature. Generally, (1) is interpreted as pre-LGM, (2) may include pre-LGM terrain but also LGM to early deglaciation (ice margin still far from study area; ice sheet thinning phase) and (3) was formed during the final ice retreat phase. The resultant surface till composition within relict and palimpsest GTZs is a spatial mosaic interpreted to reflect variable intensities in modification (overprinting) and preservation (inheritance) of a predominately pre-deglacial till sheet. In these regions, streamlined landforms parallel to a known deglacial ice-flow orientation were unable to overprint the underlying inherited glacial sediment composition. Secondly, field investigations (sedimentology, clast fabrics, till composition, near-surface S-wave seismic surveys) have characterized the widespread Rogen moraine terrain. These transverse subglacial ridges are spatially associated with streamlined landforms, are situated on regionally low-lying terrain without topographic constraints and may have small bedrock ‘knob’ obstacles at their up-ice base. This thesis assesses Rogen moraine formation hypotheses within the new paleoglaciologic context of northern Manitoba, favours an instability mechanism for formation, and provides important field data against which further formation hypothesis should be tested. The main insight of this study is not a detailed reconstruction (local history), but rather a series of forms of evidence suggesting that the glacial history of the region is one of prevailing patchy low-erosion conditions which favored preservation of a fragmentary record of non-coeval and sometimes contrasting warm-based (more dynamic) conditions. Despite being near a thick inner-core region of the Laurentide Ice Sheet, where basal conditions are generally considered stable and meltwater availability is low, the hard-bed study area was subject to local spatio-temporal shifts in subglacial conditions that led to generation of a complex palimpsest glacial landscape. Spatial differences in the preservation of older streamlined landforms, variably drumlinized Rogen moraine and the concentrations of inherited subglacial detritus all culminate in a hypothesis that suggests the subglacial landscape was continually evolving and subject to spatio-temporal variations in the intensity of ice-bed processes throughout the last glaciation (subglacial bed mosaic). Based on the new glacial history, and a general lack of ice-marginal landsystems, most warm-based ice-flow phases likely occurred near LGM – with only weak overprinting during late deglaciation. The idea of landform generation at patches within a transient subglacial bed mosaic now allows for a close association between subglacial drumlins and Rogen moraine ridges, that may have formed by disconnected and not necessarily coeval or related processes. This mosaic, of slow to non-flowing basal ice (‘sticky regions’) and wet-based flowing-ice patches, also helps to explain preservation of immature landforms (Rogen moraine) and relict or palimpsest terrain. Sticky regions may have formed by at least two different mechanisms: localized heterogeneous switches in basal thermal regime (frozen-bed patches), or within a warm-based subglacial environment from wet to stiff, dewatered till.

Thesis (Ph. D.)--University of Chicago, 1936. / Vita. Lithoprinted. "Private edition, distributed by the University of Chicago libraries, Chicago, Illinois."

No description available.

Population fragmentation and subsequent isolation in different refugia during the glacial advances of the Pleistocene are believed to have had a significant impact on current levels of genetic and morphological diversity. Despite the importance of these glacial refugia for biodiversity, our understanding of their distribution on the northwestern coast of North America and their relative impact on populations remains limited. As the most isolated group of islands in the Pacific Northwest, Haida Gwaii has been the subject of intense study both from the perspective of its complex glacial history and endemic flora and fauna. The ubiquitous presence of glacial features on this archipelago points to extensive ice cover during the late Wisconsin (Fraser glaciation) and populations which could only have become established postglacially. However, the large assemblage of unique mammalian and avian fauna found on Haida Gwaii has led to suggestions that these divergent vertebrates actually evolved through long isolation by continuously inhabiting these islands or nearby regions throughout the last glacial maximum. To assess Haida Gwaii’s role as a glacial refugium and the relictual status of its endemic black bear (Ursus americanus), marten (Martes americana), short-tailed weasel (Mustela erminea), caribou (Rangifer tarandus) and Saw-whet Owl (Aegolius acadicus), a broad phylogeographic study using sequence comparisons of the mitochondrial gene cytochrome b was undertaken. Phylogeographic structure was observed in the black bear (n= 33), marten (n= 18) and short-tailed weasel (n= 32). Based on parsimony, maximum likelihood, and neighbour-joining analyses of 719 bp of cytochrome b, two geographically structured black bear lineages were unambiguously identified: 1) a continental lineage found in the Yukon, Alberta, Alaska, Montana and Pennsylvania (americanus) and mainland BC (americanus and cinnamomum) and 2) a coastal lineage found on Haida Gwaii (carlottae), Vancouver Island (vancouveri) and the Olympic Peninsula (altifrontalis). The two lineages were defined by 24 synapomorphies and an average sequence divergence of 3.6%. Average intralineage divergence was 0.1%. Similarly, two geographically structured lineages, continental and coastal, were also identified in marten using the same types of analyses on 3II bp of cytochrome b. The continental lineage included marten from mainland BC (caurina and abietinoides) and Newfoundland (atrata) whereas the coastal lineage included marten from Haida Gwaii (nesophila) and Vancouver Island (vancouverensis). The two lineages were defined by three synapomorphies and an average sequence divergence of 1.2%. Average intralineage divergence was 1%. Phylogeographic structure was also observed in the short-tailed weasel using 148 to 673 bp of cytochrome b. Three major lineages were identified and named according to their putative refugial source areas: Beringia, which included weasels from Japan (orientalis) and the Yukon (arctica), a continental or southern source, which encompassed weasels from mainland BC (richardsonii, invicta,fallenda), Manitoba (bangsi), and Ontario (cicognanii), and Haida Gwaii which included only those weasels from Haida Gwaii (haidarum). Short-tailed weasels from Vancouver Island (anguinae) and some areas along the coast demonstrated an affinity to both southern and Haida Gwaii weasels. Relative to the continental lineage, the coastal lineage was defined by 13 synapomorphies; the Beringian lineage was defined by 10 synapomorphies. Average sequence divergence was 2.5 % and 2.2% respectively. Divergence between the coastal weasels and Beringian weasels was 2.4%. There was little mtDNA diversity within the coastal lineage as the average intralineage divergence was 0.8%. Little or no phylogeographic structure was observed in the caribou and Saw-whet Owl. Of the 313 bp examined in two barren ground caribou (granti) and seven woodland caribou (four tarandus and three dawsoni), three tarandus and two dawsoni formed a lineage defined by one synapomorphy. The two barren ground, one tarandus, and one dawsoni were excluded from this lineage by one to three substitutions. Similarly, little phylogeographic structure was observed in the Saw-whet Owl. Analyses of a 241 bp of cytochrome b sequenced from this species indicated no genetic divergence between individuals as far apart as Haida Gwaii (brooksi) and Manitoba (acadicus). The maximum divergence observed between individuals was 0.4%. The phylogeographic patterns from these five species have two major implications with regard to the issue of glacial refugia and the relictual status of the Haida Gwaii endemics: 1) With the possible exception of haidarum, the suite of morphological features characterizing the endemics carlottae, nesophila, dawsoni and brooksi appear to have been derived postglacially. In fact close genetic affinity of these endemic subspecies with adjacent conspecifics suggest that population fragmentation caused by glaciers has had little effect on morphological differentiation and that adaptation to local ecological environments has played a more influential role in their evolution. 2) Emerging data of a mid-Pleistocene split of many vertebrate taxa and the geographic distribution of these various generic lineages, including the black bear, marten and short-tailed weasel in this region cumulatively suggests that a refugium existed on the continental shelf off the central coast of British Columbia and was possibly part of a larger (or series of refugia) refugium which extended further north and south along this coast. Given the broad assemblage of taxa which might have persisted here during the last glaciation, this refugium was probably ecologically productive and as such, was likely to have been an important alternate source area for the postglacial recolonizarion of northwestern North America. / Graduate

No description available.

No description available.