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In the Canadian high Arctic, tabular massive ground ice is found extensively throughout the Eureka Sound Lowlands (ESL). This study evaluates the development of tabular massive ice in raised marine-deltaic sediments of the ESL based on new cryostratigraphic data from sites found between the coastline and the Holocene marine limit. At all sites, massive ice is found below laminated fine-grained marine sediments, and the upper contact between the ice and the overlying marine sediments is conformable and gradational. The concentration of major ions in the massive ice is orders of magnitude higher than expected for glacial ice, but Na/Cl molar ratios vary following elevation: the higher-elevation site has ratios similar to glacial ice, but sites at lower elevations have ratios closer to seawater. The δ18O values of the ice indicate that the main source of water is glacial meltwater but the δD-δ18O regression slope values suggest that the ice formed in an open system while receiving an influx that had a substantially different isotopic signature than the initial reservoir. The development of massive ice in the marine-deltaic sediments involves glacial meltwater recharging an aquifer beneath the Holocene marine sediments with a contribution of 1-10% of seawater. [ABSTRACT FROM AUTHOR]

In the late 1980’s and early 1990’s, various media in karst environments in the Northern Yukon Territory were examined for their diatom content. Cryogenic cave calcite powders, grus and various ice formations (ice plugs, ice stalagmites and floor ice) were collected from three freezing caves and one slope cave to make an inventory of the diatom content, and to explain the spatial distribution of the diatoms within the caves. The results show that approximately 20% of diatoms in the caves originate from external biotopes and habitats (e.g., river, lake, stream), with the remaining 80% of local origin (i.e., from subaerial habitats near cave entrances). The results also indicate that the greater abundance of diatoms is found in the larger caves. This is explained by the fact that the air circulation dynamics are much more important in caves that have a larger entrance. Also grus, ice plugs and ice stalagmites have the lowest diatom diversity, but greater relative abundance, indicative of growth in specific habitats or under specific conditions. Overall, these results are a contribution to the study of particles transport in ice caves.

In this study, the sediments exposed in a fluvial terrace and in the headwall of a thaw slump in the Eagle River valley, northern Yukon, provide new data about the timing of flooding of glacial Lake Old Crow, the formation of massive ground ice bodies, and the vegetation and the fauna in eastern Beringia during the late Quaternary. The stratigraphy and radiocarbon ages establish the following chronology of events: (1) a gravel fluvial terrace was deposited by an overflow from glacial Lake Hughes into glacial Lake Old Crow; (2) a carbonate silty clay was deposited during the maximum level of glacial Lake Old Crow at 15 120 [sup.14]C year BP; (3) permafrost and large intrusive ice bodies aggraded through the glaciolacustrine and underlying sediments following the drainage of glacial Lake Old Crow from the site; (4) at 11 290 [sup.14]C year BP, a shrub-sedge tundra colonized an uneven surface deformed by the bodies of ground ice; (5) a thaw lake drained at 6730 [sup.14]C year BP after flooding the site; (6) during the early Holocene and from the previous major event onwards, material from the slope nearby the site buried the previous organic and inorganic sediment and the ice bodies; and (7) a bison (Bison) vertebra with conspicuous cut marks was dated to 12 210 ± 70 [sup.14]C year BP. The age from the bison bone is amongst the most recent of the late Pleistocene bison specimens yet found in eastern Beringia. Dans cette etude, les sediments exposes dans une terrasse fluviale et dans la paroi d'un affaissement du au gel de la vallee de la riviere Eagle, dans le nord du Yukon, fournissent de nouvelles donnees concernant le moment de l'inondation du lac glaciaire Old Crow, la formation d'amas massifs de glace dans le sol ainsi que la vegetation et la faune dans la Beringie orientale au Quaternaire tardif. La stratigraphie et les ages determines par radiocarbone etablissent la chronologie des eveenements suivante : (1) une terrasse fluviale de gravier a ete deposee par un deebordement du lac glaciaire Hughes dans le lac glaciaire Old Crow; (2) une argile silteuse carbonateea ete; deposee lorsque le niveau du lac glaciaire Old Crow etait a son maximum a 15,120 anneees [sup.14]C avant le present; (3) le pergelisol et de grands amas intrusifs de glace se sont accrus a travers les sediments glacio-lacustres et ceux sous-jacents a la suite du drainage du lac glaciaire Old Crow du site; (4) a 11,290 annees [sup.14]C avant le present, une toundra parsemeee de cypeeraceees et d'arbrisseaux a colonise une surface irreguliere deeformee par les amas de glace dans le sol; (5) un lac de fonte s'est draine il y a 6730 annees [sup.14]C avant le present, apres avoir inonde le site, durant l'Holocene precoce et (6) a partir de ce dernier grand eveenement, le materiau de la pente avoisinant le site a enseveli les anciens sediments organiques et inorganiques et les amas de glace. Finalement, une vertebre de bison (Bison) comportant des marques eevidentes de coupures a ete dateeea 12,210 ± 70 annees [sup.14]C avant le present. L'age de l'os de bison est parmi les plus recents des specimens de bisons du Pleistocene tardif trouvesa ce jour dans la Beringie orientale., Introduction During the late Pleistocene, the unglaciated regions of interior Alaska and Yukon were connected to northeast Eurasia as part of the continental-scale, ice-free region known as Beringia (Hopkins et [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2008.05.017 Byline: Denis Lacelle (a), David Fisher (b), Ian D. Clark (c), Alain Berinstain (a) Keywords: Mars; polar geology; Geological processes Abstract: In this study, various approaches that can potentially distinguish between vapor- and liquid-derived ground ice in the martian regolith (petrography, geochemistry, stable OH isotopes, CO.sub.2 O.sub.2 N.sub.2 Ar gas composition) are examined using terrestrial ground ice examples. Although the stable OH isotope composition ratios can distinguish between vapor- and liquid-derived terrestrial ground ice, there might be to much mixing between the various water reservoirs on Mars to effectively use it, and, like on Earth, petrographic and geochemical approaches need to be complemented with additional supporting evidences. Of the different approaches currently being employed to determine the origin of terrestrial massive ground ice and icy sediments, it is the concentration of CO.sub.2 and the O.sub.2/Ar, N.sub.2/Ar and N.sub.2/O.sub.2 ratios of air entrapped in the ice that has proven to be the less ambiguous and most discriminatory. This is because the molar ratios of atmospheric gases change during their dissolution in water due to differences in their relative solubilities, thus providing distinctive ratios for the dissolved gases. The gas composition of air entrapped in the ice not only distinguishes between vapor- and liquid-derived ground ice, but any deviation from the theoretical dissolved values can provide insights into potential physical and biological processes operating in the subsurface, a key component for astrobiology. Author Affiliation: (a) Planetary Exploration and Space Astronomy, Canadian Space Agency, 6767 route de l'aeroport, St-Hubert, QC, J3Y 8Y9, Canada (b) Glaciology Section, Geological Survey of Canada, NRCan, 601 Booth Street, Ottawa, ON, K1A 0E8, Canada (c) Ottawa-Carleton Geoscience Center, Department of Earth Sciences, University of Ottawa, 140 Louis Pasteur, Ottawa, ON, K1N 6N5, Canada Article History: Received 19 March 2008; Revised 22 May 2008

This study examines the physical and geochemical properties of near-surface sediments, as well as the geochemical and stable O-H-C isotope composition of (ground)surface waters in and around the Haughton impact structure region (Devon Island, Nunavut) to determine the types of weathering (mechanical, (bio)chemical) and their relative contribution in this polar desert environment. The surface sediments collected from the Allen Bay and Thumb Mountain formations surrounding the impact crater are dominated by sand-sized particles; whereas the impact melt breccias inside the crater have a greater abundance of silt-sized particles. The subsurface sediments in the Allen Bay formation show a near equal amount of sand- and silt-sized particles. However, the micromorphologies of the sand-sized particles collected at the surface revealed that these grains, irrespective of the local geology, were heavily fractured. By contrast, fractures and rounded pits are observed on the surface of the sand grains located within the active layer; whereas those located just above the permafrost table have only rounded cavities on their surface. The (ground)waters also show variations in their solute concentration with depth; the highest concentrations being found in the groundwaters near the top of permafrost. Taken together, these observations suggest that there is a progressive evolution from a mechanically dominated weathering regime near the surface, to increasing chemical weathering with depth. The transition from mechanical weathering near the surface to increasing chemical weathering with depth can be attributed to the decreasing frequency and intensity of mechanical weathering processes (i.e., frost action, wetting- drying, thermal dilation) with depth, and to the presence of permafrost, which allows a greater availability of water for chemical aqueous reactions at the base of the active layer. Cette etude examine les proprietes physiques et geochimiques de sediments pres de la surface ainsi que la composition geochimique et la composition des isotopes stables O-H-C des eaux souterraines et de surface dans la region de la structure d'impact Haughton et autour de celle-ci (ile Devon, Nunavut) afin de determiner le type de meteorisation (mecanique, (bio)chimique) et leur contribution relative dans cet environnement de desert polaire. Les sediments de surface recueillis des formations d'Allen Bay et de Thumb Mountain entourant le cratere d'impact comprennent surtout des particules de la taille du sable, alors que les breches de fusion d'impact a l'interieur du cratere presentent plus de particules de la taille du silt. Les sediments sous la surface dans la Formation d'Allen Bay montrent des quantites presque egales de particules de la taille du sable et du silt. Toutefois, la micromorphologie des particules de la taille du sable recueillies a la surface revele que ces grains etaient grandement fractures, peu importe la geologie locale. Cependant, des fractures et de petites depressions arrondies sont observees a la surface des grains de sable situes dans la couche active, alors que les particules situees tout juste au-dessus de la nappe du pergelisol ne presentent que des cavites arrondies a leur surface. Les eaux souterraines presentent aussi des variations de concentration de solute avec la profondeur; les plus hautes concentrations se retrouvent dans les eaux de surface pres du sommet du pergelisol. Prises ensemble, ces observations suggerent qu'il existe une evolution progressive d'un regime d'alteration principalement mecanique pres de la surface a une alteration de plus en plus chimique avec la profondeur. La transition d'une alteration mecanique a proximite de la surface a une alteration chimique plus poussee avec la profondeur peut etre attribuee a la frequence et l'intensite decroissantes des processus d'alteration mecanique (c.-a-d. l'action du gel, les cycles de mouillage et sechage, la dilatation thermique) avec la profondeur et a la presence du pergelisol qui permet une plus grande disponibilite d'eau pour des reactions chimiques aqueuses a la base de la couche active. [Traduit par la Redaction], Introduction In periglacial environments, weathering processes (i.e., mechanical, chemical, and biological) occur mainly in the active layer, which is the top layer of soil that undergoes annual freezing and thawing. [...]

Abstract: This study documents the discovery of calcite crusts on the upper surface of clasts within morainic complexes in Akshayuk Pass, southern Cumberland Peninsula (Baffin Island), a region underlain by [...]