I. Rod Smith

Large-scale reorganization and sedimentation of terrestrial ice streams during late Wisconsinan Laurentide Ice Sheet deglaciation.

Glacial geomorphological mapping of Shuttle Radar Topography Mission (SRTM) data from the western Canadian Prairies demonstrates that during the last (late Wisconsinan) deglaciation of the Laurentide Ice Sheet terrestrial ice streams underwent a major reorganization of their flow configuration. This reorganization involved a 90° shift in flow direction and was accompanied by a corresponding increase in the influence of topography on streaming flow. Ice streams included both topographically confined and “pure” ice streams that flowed independent of topography. Streaming flow is recorded by suites of highly elongate (>60 km long) subglacial bedforms, bounded sharply at their lateral margins by prominent moraines. Initial streaming flow was unconfined by topography but was replaced progressively, and crosscut, by younger topographically confined flows. Flow reorganization is inferred to have been caused by temporal and spatial variations in the interaction between frozen and thawed bed conditions, with thinning and shutdown of one ice stream ultimately triggering initiation of others. This highlights the role of internal glaciodynamically driven reorganization in triggering streaming flow within large ice sheets and shows that large-scale flow reorganization can occur over the time scale of a single deglaciation in terrestrial ice streams.

Diatom-based Holocene paleoenvironmental records from continental sites on northeastern Ellesmere Island, high Arctic, Canada

Stratigraphic changes in diatom assemblages from four small lakes on northeastern Ellesmere Island, high Arctic, Canada, provide a proxy lake-ice cover and paleoenvironmental record. Low absolute diatom abundances and a benthic Fragilaria (sensu lata) dominated assemblage during the postglacial (< 7.6 ka B.P.) to mid-Holocene record the moderating effects of locally retreating glaciers. Around 5.5 ka B.P. diatom concentrations begin to rise, reaching their highest levels (109 valves per g dry sediment) between 4.2 and 3 ka B.P., interpreted to be the warmest period in this region. Topoclimatic differences between lakes on Hazen Plateau and those lower in Lake Hazen Basin account for the initial decline in diatom abundances in the upper lakes after 3 ka B.P. This change is thought to reflect a lowering of the regional snowline, accordant with widely recognized Neoglacial advances on Ellesmere Island and Greenland. Lakes in lower Lake Hazen Basin maintained extensive summer ice free conditions until ~ 1.9 ka B.P., after which diatom abundances declined, suggesting prolonged summer lake-ice cover through the remainder of the recovered Holocene record. Differences between the records presented here and those from coastal areas of the Canadian high Arctic highlight the unique topoclimatic characteristics and continentality of the Lake Hazen region, and possible effects that local marine environments may have had on coastal records. Such differences serve to demonstrate the inherent geographic variability of paleoenvironmental records from the high Arctic.

Timing and extent of plio-pleistocene glaciations in north-western canada and east-central alaska

Abstract North-western Canada and eastern Alaska are recognised as having one of the oldest known continental glacial records (Late Pliocene) preserved in stratigraphical sections. These include the individual and complex records of Cordilleran, montane and continental glaciations. Regional scale glaciations (Cordilleran and continental) started in northwestern Canada and east-central Alaska between 2.9 and 2.6 million years ago. Overall, two Cordilleran glaciations and two plateau ice caps (Horton Ice Cap) developed in Late Pliocene (Gauss and Matuyama Chron). During the Early Pleistocene, three Cordilleran glaciations occurred, while one to five continental glaciations (Keewatin Ice Sheet and Horton Ice Cap) are inferred from the Banks Island stratigraphic record (late Matuyama Chron). Three Middle-Pleistocene glaciations are recorded for the Cordilleran (including the Reid Glaciation) as well as three continental (Keewatin Ice Sheet and Horton Ice Cap) events (early Brunhes Chron). During the Late Pleistocene (late Brunhes) a well defined, extensive continental ice sheet (Keewatin) covered western and northwestern Canada, while in the Yukon Cordillera and Yukon-Tanana Uplands, two glaciations (Early-Late Pleistocene Eagle Glaciation, and Late Pleistocene McConnell Glaciation) are recognised. Successive Cordilleran glaciations diminished in size, while continental glaciations increased. The moisture source for the Cordilleran ice was largely the Pacific Ocean, however, for the Horton Ice Cap, an open Arctic Ocean may have been a significant moisture source. The role of tectonics in the development of the two major physiographic barriers, Wrangell/St. Elias Mountains and the Continental Divide (Mackenzie/Selwyn Mountains) appears to have been an important controlling variable in moisture distribution in northwest Canada and east-central Alaska. The timing and interplay of tectonic uplift versus erosion of these barriers has very much controlled the growth, thickness and decay of ice masses in the interior of Yukon and valleys east of the continental divide.

Paleolimnology of the middle and high Canadian Arctic

The objective of this chapter is to complement, rather than duplicate, previous reviews of arctic paleolimnology (Smol and Douglas 1996; Douglas and Smol 1999), paleoclimatology (Ovenden 1988; Bradley 1990), and developments in the application of paleolimnological techniques to the reconstruction of climate change (Smol and Cumming 2000). Our approach is to first provide a detailed environmental overview of this vast region, then a brief history of limnological and paleolimnological research, before assessing regional paleolimnological records from the oldest to youngest deposits. Methodological considerations are limited, since these are covered in separate contributions to this volume. Emphasis is placed on climatic influences on lake development and, consequently, on demonstrating the utility and limitations of paleolimnology in the generation of proxy paleoclimate data. In many ways, this is the most pressing agenda for paleoenvironmental research in the high latitudes, given (a) the relatively poor spatial coverage of available data by comparison to temperate regions, and (b) the acknowledged sensitivity of the Arctic to climate change, borne out of its intimate linkage to ocean circulation, atmospheric feedback mechanisms involving snow and ice cover, and biospheric modulation of greenhouse gas concentrations.

Data Mining Seismic Shothole Drillers’ Log Records: Regional Baseline Geoscience Information in Support of Pipeline Proposal Design, Assessment, and Development

Assessment and development of pipeline projects in northern Canada, such as the proposed Mackenzie Valley gas pipeline (MGP), are hampered by a lack of baseline terrain geoscience information including drift thickness, sediment type, presence of massive ground ice, and the availability of granular aggregate resources. Clearly there is a need by Industry, Regulators, Aboriginal groups, and others, to understand the nature and character of near-surface earth materials, in order that pipeline proposals can be properly developed, evaluated, and when approved, proceed with the greatest degree of environmental sustainability and economic efficiency. While numerous field-based reports and surficial geology maps have been prepared for the MGP, there are long stretches along the proposed route for which little near-surface geoscience information is available. This is even more apt for areas outside the defined MGP corridor, where the likelihood of tie-in and gathering pipeline systems exist. Drillers’ logs, recorded during auger drilling of seismic shotholes, represent a virtually untapped resource of regional baseline geoscience information. The Geological Survey of Canada recently produced a digital archive of 76,000 shothole records from the Northwest Territories and Yukon, which had originally been collected on file cards in response to the 1970’s MGP proposal. Released in 2007 as a freely downloadable Open File report (#5465), the archive provides users with an Access database of drillers’ logs and derivative GIS maps in which shapefiles of drift isopach thickness, potential granular aggregate resources, geohazards, permafrost and ground ice occurrences, and muskeg thickness can be opened, viewed, and queried, or otherwise incorporated into GIS platforms of the user’s choice. Realizing the amount of additional archival shothole information held by Industry, and the great utility of bringing this forth in a public database and derivative GIS, a subsequent project has focused on capturing and integrating additional data. Receiving near-universal support by the Petroleum Industry, a Version 2 of the database and GIS is currently being assembled, and is scheduled for release in 2009 with some quarter million individual shothole drillers’ records. This presentation highlights the nature, character and distribution of shothole drillers’ logs in northern Canada. It also reviews the derived GIS layers, and how this baseline geoscience information can be beneficially utilized by the Pipeline and related infrastructure development industries, particularly as it may apply to focusing future field studies. It also serves as a key reference tool for those assessing pipeline development proposals.Copyright