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As part of an interdisciplinary field program, a 1150-m deep well was drilled in the Canadian Arctic to determine, among other goals, the location, characteristics, and properties of gas hydrate. Numerous physical properties of the host sediment were measured in the laboratory and are presented in relation to the lithology and quantity of in situ gas hydrate. Profiles of measured and derived properties presented from that investigation include: sediment wet bulk density, water content, porosity, grain density, salinity, gas hydrate content (percent occupancy of non-sediment grain void space), grain size, porosity, and post-recovery core temperature. The greatest concentration of gas hydrate is located within sand and gravel deposits between 897 and 922 m. Silty sediment between 926 and 952 m contained substantially less, or no, gas hydrate perhaps because of smaller pore size.

Attempts have been made to simulate hillslope creep observations at a site near the village of Tuktoyaktuk, Northwest Territories. Unlike other creep studies in permafrost, this site was unique in that the deformations occurred within a massive ice body, forming the core of a 30 m high concentric hill approximately 1200 m long and 700 m wide. The described simulation model of slope creep is based on both an extension of a closed-form solution originally proposed for two- and three-dimensional ice caps and a finite element creep analysis. The solution covers cyclic temperature fluctuations and incorporates spatial variations of the temperature-dependent creep parameters. Results of simulations are compared with in situ measurements of creep displacements in the hill.Key words: permafrost, slope, creep, in situ measurements, numerical simulation.

A study of the in situ creep deformation of massive ground ice has been carried out at a field site near the village of Tuktoyaktuk, NWT. Cumulative surface displacements, accounted for by creep deformation to a depth of 25 m, vary from about 3 mm/a at the upslope site to 4 mm/a at the downslope site. While net displacements on a year to year basis were downslope, the creep pattern at both sites displays a quasi-sinusoidal fluctuation, with significant seasonal upslope movement during the late winter and early summer. This fluctuation is thought to be due to the effects of thermal contraction. © 1996 John Wiley & Sons, Ltd.

Active-layer and permafrost temperature data collected in the Mackenzie Delta, at Canadian Forces Station Alert and Baker Lake have been analyzed along with climatic data to determine the response of the active layer and the ground thermal regime to the anomalous warming associated with strong El Nino conditions of 1998. In the Mackenzie Delta region, early warming in 1998 resulted in earlier thaw of the active layer, warmer summer ground temperatures, and a longer thaw season which produced greater thaw penetration compared to previous years in the 1990s. At Baker Lake, warming was less pronounced and occurred later in the summer resulting in a slight extension of the thaw season into the fall. Warming was less extreme in the high Arctic but snow depths were greater at CFS Alert in 1998 and this appears to have resulted in higher shallow ground temperatures during the winter (February to April) of 1998. 2001-E5 S.L. Smith et al. 1 CURRENT RESEARCH RECHERCHES EN COURS 2001 Article Article Titles Titres Purchase Information Information pour acheter

IcewedgesonnorthernRichardsIsland,NorthwestTerritories,andalongtheYukonTerritorycoastlands,haverespondedtoincreasedthawdepths.Observationsmadein1999arecomparedtothoselastmadeintheseareasin1975and1984,respectively.Climatedataindicatethatairtemperaturesintheseareashavebeenwarmerthanaveragesince1978andthatwarmingin1998wasanextremeevent.Increasedthawinresponsetothiswarminghascausedadecreaseinthenumberofsecondaryandtertiaryicewedges,andisattributed to thaw truncation. Depths to the tops of ice wedges on Richards Island have increased, whereasdepths have decreased on the Yukon Territory coastlands due to thaw consolidation. Thaw-tube observa-tions indicate that 1998 thaw depths were the greatest since 1991 across the northern Mackenzie Deltaregion, with increases of as much as 21 cm.1 Resume : Lesfentesdeglacedanslenorddel’ileRichards(TerritoiresduNord-Ouest)etlelongdester-rains cotiers du Territoire du Yukon, ont reagi a l’accroissement de la profondeur de degel. On compare lesobservations faites en 1999 avec celles faites dans les memes regions en 1975 et en 1984, respectivement.Lesdonneesclimatiquesindiquentquedepuis1978,latemperaturedel’airdanscesregionsaetepluseleveeque la moyenne et qu’en 1998, le rechauffement a ete un evenement extreme. Suite a ce rechauffement, undegel plus profond a cause une diminution du nombre de fentes de glace secondaires et tertiaires et estattribuablealatroncatureparledegel.Laprofondeurjusqu’ausommetdesfentesdeglaceaaugmentedansl’ileRichardsalorsqu’elleadiminuelelongdesterrainscotiersduTerritoireduYukonenraisondelacon-solidation due au degel. Les observations dans les tubes de degel ont indique qu’en 1998, la profondeur depenetrationdudegelaetelaplusgrandedepuis1991danslenorddudeltaduMackenzie,avecdesaugmen-tations allant jusqu’a 21 cm.

Drilling in the floor of the Bélanger sand pit (Ontario) near Pointe-Fortune, Québec, added 3 stratigraphic units to those already exposed in the pit: a lowermost till, and an intermediate organic-bearing (?) sand-clay unit overlain by a massive lacustrine clay. The subsurface units, comprising about 70% of the stratigraphy, complete the Quaternary sequence exposed in the pit face : an organic-bearing silty sand (>40 000 years BP) unit truncated by an unfos-siliferous sand unit and overlain by the uppermost till. The overall sequence forms a continuous 18 m column of Quaternary sediments. The Pointe-Fortune sequence shows some similarities with the Trois-Rivières Quaternary series which includes the Saint-Pierre sediments >75 000 years old. In addition to stratigraphie information the combination of direct (drilling) and indirect (geophysical) methods of investigation by providing a three-dimensional picture of the subsurface has proved helpful in interpreting the stratigraphy. The geotechnical properties of a massive overconsolidated clay have been determined to facilitate the planning of future subsurface investigation., Des forages à l'intérieur de la sablière Bélanger (Ontario) près de Pointe-Fortune, Québec, permettent d'ajouter trois unités stratigraphiques à celles déjà visibles à la surface: un till inférieur, et, en position intermédiaire, un ensemble sable-argile avec matière organique(?) recouvert par une argile lacustre. Ces trois unités comprennent près de 70% de la stratigraphie du site et sont recouvertes par une unité de sable et de sable silteux contenant de la matière organique datée à >40 000 ans. Cette dernière est tronquée par une unité de sable non fossilifère, et un till occupe le haut de la coupe. La totalité des sédiments quaternaires forment une séquence de 18 m de haut. La séquence quaternaire de Pointe-Fortune présente des similarités avec la série quaternaire de Trois-Rivières, qui inclut les sédiments de Saint-Pierre d'un âge de plus de 75 000 ans. Cette étude en plus de fournir de nouvelles données sur la stratigraphie démontre que l'utilisation conjointe de techniques directes (forages) et indirectes (géophysiques) s'avère utile à l'interprétation des données stratigraphiques en présentant une image tri-dimensionnelle du terrain. Afin de faciliter de futurs travaux de forage, nous avons établi les propriétés géotechniques de l'argile massive compacte.