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This paper discusses the value of clan name research as a means of uncovering Aboriginal place names. It argues that clan names are able to provide a layer of place names that in some instances is the only source of information available to researchers of indigenous toponymy. They are an important data set that is useful in the mapping of Aboriginal spatial organization. [ABSTRACT FROM AUTHOR]

Groundwaters, surface runoff and river discharge have been studied at the Fish Hole area of the Big Fish River catchment, near Aklavik, N.W.T., to quantify the seasonal variations in groundwater contributions to baseflow in a permafrost basin. Geochemical and isotope methods are used to distinguish three principal water types: (1) subpermafrost Na-Cl thermal waters (16°C) discharging from bedrock along the river, (2) shallow, Ca-SO4 groundwaters, and (3) low-salinity, Ca-HCO3, suprapermafrost drainage. Cl and SO4 concentrations in river water show that baseflow is largely derived from groundwater sources (Na-Cl and Ca-SO4 components), with less than 30% contributed from surface water runoff in any season. Thermal groundwaters discharge year-round at a calculated 1.6 m3 s−1. The shallow, Ca-SO4 groundwater is the dominant component of baseflow in summer but is absent in winter baseflow. Discharge analysis based on a single flow measurement (25.5 m3 s−1 in June, 1997) and Cl-dilution allows calculation of total river discharge. This is shown to vary from a low of 2.2 m3 s−1 in the winter, to 1050 m3 s−1 during early spring melt. [ABSTRACT FROM AUTHOR]

Surficial CO 2 efflux surveys have been used to delineate hydrocarbon source zones in contaminated aquifers and provide estimates of hydrocarbon biodegradation rates. This approach requires distinguishing between CO 2 derived from petroleum degradation and CO 2 produced from natural soil respiration. To this end, radiocarbon has been used to differentiate between 14C–depleted CO 2 from hydrocarbon degradation and 14C–enriched CO 2 from natural soil respiration to effectively quantify the contribution of each source to total CO 2 efflux, and by deduction natural source zone depletion (NSZD) rates. In this study, a systematic method comparison has been conducted to evaluate available approaches for collecting CO 2 gas samples for radiocarbon analysis used to correct total CO 2 efflux measurements for quantifying natural source zone depletion rates. Gas samples for radiocarbon analysis were sampled from (i) dynamic closed chambers (located at ground surface), (ii) static chambers (also at ground surface), (iii) shallow soil gas probes (0.3 m bgs), and (iv) soil gas monitoring wells (~0.6 m below ground surface) during a CO 2 efflux survey conducted at the site of a historical pipeline rupture near Bemidji, MN. The mean fraction of radiocarbon (F14C) obtained from samples overlying the source zone were (i) 0.93 ± 0.01, (ii) 0.73 ± 0.03, (iii) 0.71 ± 0.04, and (iv) 0.41 ± 0.06, for the four methods respectively. These F14C values were used to apportion total CO 2 efflux measurements into contributions of contaminant–derived CO 2 efflux and natural soil respiration to evaluate natural source zone depletion processes. Results suggest that the method of radiocarbon sampling has a significant effect on the calculated fraction of the CO 2 efflux originating from contaminant-related soil respiration, with contributions ranging between 27% and 59% of total soil respiration. Results indicate that radiocarbon sampled from static chambers and shallow soil gas probes methods offer the best compromise between CO 2 sample yield and sample representativeness, providing the most reliable estimates of CO 2 effluxes originating from contaminant degradation. However, the results also show that for this study, all methods agree within a factor of <2.3 regarding the inferred NSZD rates. • Carbon dioxide efflux monitoring for natural source zone depletion • Radiocarbon methods for apportioning contaminant soil respiration • Estimating hydrocarbon source zone biodegradation rates • Dynamic closed chamber, static chamber, soil gas probe and soil gas monitoring well methods for monitoring petroleum hydrocarbon source zones [ABSTRACT FROM AUTHOR]

Presents information on a study on a temporal monitoring of environmental isotopes and geochemistry in ground water within the Raisin River basin, an agricultural watershed in eastern Ontario, Canada. Field sampling and analytical methods; Precipitation and runoff during study period; Seasonal variations in Carbonated geochemistry.

The sulfhydryl-selective fluorescent reagent acrylodan (6-acryloyl-2-dimethylaminonaphthalene) was used to label tropomyosins from rabbit cardiac muscle and from equine platelets. Addition of bovine pancreatic deoxyribonuclease Ito solutions of acrylodan-modified tropomyosins significantly altered the emission properties of the samples. Muscle and non-muscle tropomyosin fluorescence were affected in qualitatively similar manners; emission maxima were red-shifted by about 8 nm to 522-525 nm and maximal intensities were reduced by approximately 15%. Addition of KI to each of the fluorescent samples caused a greater degree of fluorescence quenching in the presence of DNase I than in its absence. The slopes of Stern-Volmer plots were 15-25% steeper in the presence of DNase I. Fluorescence polarization values for acrylodan-labelled tropomyosin samples were 25-35% lower in the presence of DNase 1. Each of these effects could be saturated by addition of about a two- fold molar excess of DNase I to tropomyosin. Together they suggest that interaction with DNase I causes localized unfolding of tropomyosin, thereby allowing the fluorescent label to become more exposed to the solvent and less restricted in its local motions. Circular dichroism measurements support this idea. Addition of DNase I to solutions of either labelled or unlabelled tropomyosin results in a net 14-18% loss in ellipticity near 220 nm, indicative of unfolding of α-helix. [ABSTRACT FROM AUTHOR]

Identifies the main differences between the decision-making environments of the International Monetary Fund (IMF) and Canadian governments. International character and need to solve collaboration problems as basis of decision-making in the IMF; Lessons for Canadian governments from IMF administrative practices.

Presents several letters to the editor concerning health in Great Britain. View of the general practitioners on prehospital thrombolysis; Benefits of physical activity for cardiovascular disease and functional ability of elderly people; Role of alcohol on post-traumatic stress disorder.

Rat paravalbumin (PV) and oncomodulin (OM) display considerable sequence similarity and structural similarity, but differ in the and selectivity of metal binding to their CD site a Ca2+/Mg2+-mixed site in PV and a Ca2+-specific site in OM. In an attempt to identify the structural basis for these differnces mutations were introduced in the previously generated [W102]PV mutant contain a unique trytophan as a conformational-sensitive probe inside the hydrophobic core. In the present report. We sustituted selected amino acid residues in the CD site of PV by those present at identical positions in OM, One mutant protein, named [F66, W102]PV, has one new substitution in which isoleucine at position 66 was exchanged by phenylalamine. The second mutant protein, [146, 150, L58, F66, W102] PV, has four new substitutions, namely V46→I, L50→I,I58→L and I66→F, Tryptophan fluorescence and difference spectrophotometry indicated that the mutation do not alter significance the hydrophobic core. Both mutant proteins display two-binding sites of identical affinities with intinsic affinity constant Kca2+ of 2.9&times107 M-1 for [F66, W102 ]PV and 1.7× M-1 for [146, 150, L58, F66, W102] PV and KMg2+ of 3.1×104 M-1 for [F66, W102]PV and 1.9×104 M-3for [146,150,L58, F66, W102]PV. Thus the five-residue substitution, but not the two-residues one, leads to a small decrease of affinity compared to [W102]PV (Kca2+=2.7× 107 M-1, KMg2+=4.4 × 104 M-1). [ABSTRACT FROM AUTHOR]

Abstract: This paper considers the naming history of indigenous rock art sites in the Grampians-Gariwerd National Park in southwest Victoria, Australia. These sites are found to present management problems because many of the names are dysfunctional, and fail as information markers. Rather than contribute to the creation of positive atmosphere and sacralization, many site names have contributed to site vandalism, disfigurement of signage and negative word of mouth promotion. The function of site naming and their role in place making is reconsidered from the insights of leading theorists in attraction systems such as MacCannell, Gunn, and Leiper. Naming, it is argued, is a very important management tool in the protection and promotion of rock art tourism. [Copyright &y& Elsevier]

The principal purpose of this study was to gain a greater understanding of the utilitarian and symbolic significance of koalas for Aboriginal communities in Queensland, Australia as recorded by colonists during the early period of colonization and the early twentieth century. It does this primarily through a close examination of the nineteenth-century and early twentieth-century archival records and contemporary publications that relate to Queensland Aboriginal peoples' associations with koalas. This paper is the third in a series investigating the historic and cultural importance of the koala according to the location in Australia. It likewise employs the historical method approach, which relies on identifying historical sources, evaluating their relative authority, and combining their testimony appropriately in order to construct an accurate and reliable picture of past events and environments. Through a critique of the published historical sources, the distribution of and the etymology of "koala" are briefly discussed before an examination is made of the animal's spiritual importance, associated cultural traditions, and simultaneous utilitarian role. Mirroring previous studies published by the authors on Victoria and New South Wales, we confirm that the predominately non-Aboriginal historical records reveal that koalas were hunted for food and their skin in some Queensland regions. It shall be seen that the ethno-historical records are inconclusive about the koala's distribution in Queensland, whether they were hunted across all of the state at the point of colonization and whether they were considered an integral food source in some regions. Furthermore, this study demonstrates that the extent to which they were used varied across regions and between language groups and was subject to certain rules, and that their spiritual significance can be traced directly to epic creation stories. The implications of this paper are consistent with the earlier New South Wales and Victorian studies: regional variations exist in Queensland in relation to the (pre-colonial, colonial and post-colonial) historic relationship between Aboriginal communities and koalas and that close consultation with Aboriginal communities needs to be taken into consideration when planning conservation measures relating to koalas. [ABSTRACT FROM AUTHOR]

Abstract: The study of ancient massive ground ice and sediment-rich ice bodies not only allows an understanding of the stability of permafrost, but also offers the possibility to understand the long-term preservation and viability of microbes within these ice bodies. Although microorganisms have been identified in ancient bodies of ground ice and permafrost, there still is a lack of convincing evidence that the microbes were metabolically active within the ice. In this study, we combine geomicrobiology methods with the measurements of occluded gasses in four ancient massive ground ice bodies to provide evidence of microbial respiration. In our samples, abundant cold-adapted heterotroph microorganisms were identified using culture-dependent and -independent methods. The occluded gas measurements, with low δ(O2/Ar) (less than −21.4%) and δ13CCO2 (as low as −25.2‰) values and high δ18OO2 (up to +16.3‰) values are suggestive of in situ consumption of O2 by heterotrophic psychrophilic bacteria living within the ice matrix. Overall, the multi-disciplinary approach provides a strong set of tools from which to infer metabolic activity within bodies of ground ice. The analysis of δ(O2/Ar), δ18OO2 and δ13CCO2 from occluded gasses in ice are strong isotope biosignatures that could allow detecting evidence of life on other planetary icy bodies such as Mars. [Copyright &y& Elsevier]

Abstract: In this study, various approaches that can potentially distinguish between vapor- and liquid-derived ground ice in the martian regolith (petrography, geochemistry, stable O-H, CO2-O2-N2 mposition) are examined using terrestrial ground ice examples. Although the stable O-H 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 CO2 and the O2/Ar, N2/Ar and N2/O2 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. [Copyright &y& Elsevier]

Abstract: A massive ground-ice body was found exposed in the headwall of a thaw flow developed within the Chapman Lake terminal moraine complex on the Blackstone Plateau (Ogilvie Mountains, central Yukon Territory), which is contemporaneous to the Reid glaciation. Based on visible cryostructures in the 4-m-high headwall, two units were identified: massive ground ice, overlain sharply by 2 m of icy diamicton. The nature and origin of the Chapman Lake massive ground ice was determined using cryostratigraphy, petrography, stable O–H isotopes and the molar concentration of occluded gases (CO2, O2, N2 and Ar) entrapped in the ice, a new technique in the field of periglacial geomorphology that allows to distinguish between glacial and non-glacial intrasedimental ice. Collectively, the results indicate that the Chapman Lake massive ground ice formed by firn densification with limited melting–refreezing and underwent deformation near its margin. Given that the massive ground-ice body consists of relict glacier ice, it suggests that permafrost persisted, at least locally, on plateau areas in the central Yukon Territory since the middle Pleistocene. In addition, the d value of Chapman Lake relict glacier ice suggests that the ice covering the area during the Reid glaciation originated from a local alpine glaciation in the Ogilvie Mountains. [Copyright &y& Elsevier]

Abstract: Acidic SO4–Ca–Fe waters are discharging from sandstone bedrock overlying pyrite-rich shales along the Dempster Highway near Eagle Plains, northern Yukon Territory. Although evidence of acid drainage was present prior to the construction of the Dempster Highway in the 1970''s, the removal of surficial sediments during its construction amplified the release of acidity by allowing the active layer to penetrate into the freshly exposed pyrite-rich shale. Acid drainage originating from the excavated area has a pH value averaging 3.1±0.3 and over 5 g/L of dissolved solids (SO4 2− =3915 mg/L, Fetotal =459 mg/L, Ca2+ =418 mg/L and Altotal =83.6 mg/L) whereas the unaffected drainage has a pH greater than 4.4 and total dissolved solids in the 100 to 200 mg/L range. Geochemical modeling of the surface waters and active layer pore water using PHREEQC hydrogeochemical computer code predicted saturation in Fe-hydroxide and Fe-sulfate minerals, which is confirmed by the observation of abundant ferrihydrite precipitates along the acidified stream. The solute concentrations of the acidified stream and active layer soluble ions versus SO4 plot on very similar slopes, suggesting a recycling of solutes. It is suggested that the effect of seasonal freeze-thaw of the active layer plays an important role in sustaining acidity in the stream. Freeze-back of the acid waters in the active layer produces both Fe-sulfate minerals and residual sulfuric acid. During the thaw season, this acidity is released, thus enhancing further dissolution of alumino-silicate minerals. The release of these contaminants, including acidity, not only causes a perturbation of the water quality, but also has a negative impact on the sensitive Arctic ecosystem, by disturbing the local permafrost conditions. [Copyright &y& Elsevier]

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 granitic and gneissic rocks of the Precambrian Canadian Shield. Strontium isotope ratios (87Sr/86Sr) indicate that the major source of calcium is derived from the local dissolution of fracture-filling calcite and a minor source is derived from silicate weathering. The calcite crusts have δ13C values between 1.6‰and 12.0‰and δ18O values in the –13.0‰and –7.9‰range. These values are highly enriched over the predicted isotopic values based on the δ13CDIC and δ18O of the local water and temperature at which calcite precipitation occurred. The isotopic enrichments are attributed to a combination of both equilibrium and kinetic evaporation and were verified experimentally. The series of evaporative experiments indicate that kinetic evaporation produces a far-from-equilibrium isotope effect on both the δ13C and δ18O composition of the precipitating calcite (13CKIE CaCO3–CO2 between 20.2‰and 40.5‰VPDB; 18OKIE averaging 34.9% ± 3.7% VSMOW). Based on these results, the formation of the calcite crusts is ascribed to the evaporation of stagnating ephemeral lakes and streams following the retreat of valley glaciers. Given the >1500 m difference in heights between the highland and the valley, the katabatic winds originating from the Penny Ice Cap can act as a catalyst to increase the rate of evaporation. In addition, radiocarbon dating of ten of these crusts yielded Holocene ages (7640 cal (calibrated) BP to modern). These results suggest that the maximum expansion of Holocene valley glacier in Akshayuk Pass, previously thought to have occurred during the Little Ice Age, is probably much older. [ABSTRACT FROM AUTHOR]

This article collects and presents nineteenth-century ethnographic evidence from the Newer Volcanics Province of Australia and explores how volcanism was recorded and understood in Aboriginal oral traditions. It investigates whether Aboriginal Australian oral traditions can be understood as persistent eyewitness accounts of volcanic eruptions in the Newer Volcanics Province, how and what kind of geological and volcanological knowledge was embedded within Aboriginal Australian oral traditions, and considers what value the ethnographic evidence has for understanding both the socio-cultural and geological histories of the Newer Volcanics Province. • Europeans collected ethnographic evidence of Aboriginal Australian oral traditions. • Oral traditions include creation myths and placenames from the Newer Volcanics Province. • Oral traditions demonstrate extensive Aboriginal Australian volcanological knowledge. • History enriches the cultural and geological heritage of the Newer Volcanics Province. [ABSTRACT FROM AUTHOR]

The study presents a detailed investigation of S-isotope systematics of pyrite from Cambrian-Ordovician sedimentary rocks along the eastern flank of the Michigan Basin, Ontario, Canada. Whole-rock and secondary-ion mass spectrometry (SIMS) pyrite analyses of 34S/32S were undertaken in association with a detailed petrographic investigation of the different crystal morphologies to better constrain the diagenetic history of the sedimentary rocks by informing about the processes of pyrite formation. The broad range of SIMS isotopic data (i.e., −37.1‰ < δ34S < +80.3‰) reveals that three different stratigraphic units experienced different diagenetic pathways of pyrite formation: (1) the Ordovician shales containing primarily biogenic framboidal pyrite formed during two different crystal growth phases (i.e., early diagenesis with δ34S from ~−20 to +5.0‰ and late diagenesis with δ34S from ~+20.0 to +80‰); (2) the Cobourg formation containing relatively 34S-depleted tabular pyrite (i.e., δ34S ~ −25‰) which likely reflects a late replacement phase after sulphate mineral dissolution; and (3) the Cambrian and the Ordovician Black River Group carbonates that share a genetic link in pyrite formation and a complex history of hydrothermal fluid movement. In general, the pyrite in the studied stratigraphic sequence seems to have retained S-isotope signatures indicative of a closed system at the scale of pyrite formation. This study demonstrates the importance of investigating the isotopic systematics of S-species at the microscale level to help understand the evolution of sedimentary basins over geological time scales. • Reconstruction of the diagenetic history of the Michigan Basin • Evidence for closed system pyrite formation • Sedimentary pyrite is heterogeneous in morphology and isotopic composition • Formation of "superheavy" pyrite formation unrelated to anaerobic methane oxidation [ABSTRACT FROM AUTHOR]

Perennially ice-covered lakes that host benthic microbial ecosystems are present in many regions of Antarctica. Lake Untersee is an ultra-oligotrophic lake that is substantially different from any other lakes on the continent as it does not develop a seasonal moat and therefore shares similarities to sub-glacial lakes where they are sealed to the atmosphere. Here, we determine the source of major solutes and carbon to Lake Untersee, evaluate the carbon cycling and assess the metabolic functioning of microbial mats using an isotope geochemistry approach. The findings suggest that the glacial meltwater recharging the closed-basin and well-sealed Lake Untersee largely determines the major solute chemistry of the oxic water column with plagioclase and alumino-silicate weathering contributing < 5% of the Ca2+–Na+ solutes to the lake. The TIC concentration in the lake is very low and is sourced from melting of glacial ice and direct release of occluded CO2 gases into the water column. The comparison of δ13CTIC of the oxic lake waters with the δ13C in the top microbial mat layer show no fractionation due to non-discriminating photosynthetic fixation of HCO3– in the high pH and carbon-starved water. The 14C results indicate that phototrophs are also fixing respired CO2 from heterotrophic metabolism of the underlying microbial mats layers. The findings provide insights into the development of collaboration in carbon partitioning within the microbial mats to support their growth in a carbon-starved ecosystem. [ABSTRACT FROM AUTHOR]

Abstract This paper describes a technique of making carbonate by rapid CO 2 capture from groundwater for direct measurement of the 14C content by accelerator mass spectrometry (AMS). The DIC in groundwater was extracted from acidified water in the form of carbon dioxide (CO 2), and transferred into saturated barium hydroxide solution to form barium carbonate (BaCO 3). After the BaCO 3 precipitate was freeze-dried, it was mixed with a metal powder and pressed into an AMS target for measurement. The behaviors of Si, Al, Fe and Ta powder as the binder with carbonate were evaluated. The C3+ currents from carbonate targets mixed with Fe or Ta were found generally larger than those with Si or Al by a factor of two. The baked Ta was shown to produce fewer contaminating 14C counts than all the others, with or without baking. The CaCO 3 /Ta and BaCO 3 /Ta mass mixing ratios in the range from 1:2 to 1:4 and in 1:1.5, respectively, produced optimized currents. The precision and accuracy of the measurement by direct CaCO 3 or BaCO 3 sputtering using Ta as the binder, were evaluated in comparison to a selected reference material. The agreement was reasonably good between the direct carbonate measurement and the high precision measurement through combustion and graphitization. These findings support the further development of a rapid assessment method directly from field work to measurement. [ABSTRACT FROM AUTHOR]

Holocene climate change resulted in major vegetation reorganization in sub-arctic Canada near modern treeline. However, little is known of the effects of long-term climate change on boreal forest composition and fire regimes below treeline in this region. We present a high-resolution vegetation and fire history from two sites within the modern boreal forest in the central Northwest Territories, Canada, to provide new insight on sub-arctic vegetation response to Holocene climate dynamics and the role of fire in boreal ecosystems. Palynological analysis of sediments retrieved from Waite and Danny's lakes (informal) is used to reconstruct regional vegetation dynamics and boreal fire regimes. The longer Danny's Lake record documents treeline expansion beginning at ca. 7430–7220 cal yr BP. Integration of our new data with previous work shows that treeline expanded between ca. 4050 cal. yr BP and ca. 3840 cal yr BP at a rate of ca. 50 m/yr in response to the 1–2 °C increase in temperature estimated for the Holocene Thermal Maximum. Forest fires were relatively frequent during the early Holocene, before declining in frequency in response to development of cooler and wetter climate conditions associated with the Neoglacial (beginning after ca. 2200–2320 cal yr BP). We document a trend of increasing fire frequency in the 20th century that is correlated with warming at this time. These dynamics south of modern treeline provide insight into factors creating heterogeneity in plant community responses to large-scale climate events in high northern latitudes and suggest that large scale reorganization of boreal vegetation and fire regimes can be expected over the coming decades. [ABSTRACT FROM AUTHOR]

Abstract: Retrogressive thaw slumps are one of the most dramatic thermokarst landforms in periglacial regions. This study investigates the impacts of one stable and two active thaw slumps on the geochemistry of streams in the Stony Creek watershed (Peel Plateau, NWT, Canada). The objective of this study is to elucidate the geochemical processes associated with ground ice ablation in retrogressive thaw slumps and the geochemical evolution of slump runoff to streams. This is accomplished by describing the geochemical composition of runoff across active mega-slumps, impacted and pristine tundra streams, as well as that of the ice-rich permafrost exposed in the slump headwalls. In the Stony Creek watershed, runoff derived from active and stable thaw slumps is characterized by a Ca(Mg)–SO4 geochemical facies with conductivity and solute concentrations approximately one order of magnitude higher than in pristine streams. The elevated solute concentrations in the slump runoff are directly related to thawing of highly weatherable Late Pleistocene age ice-rich and solute-rich permafrost exposed in the headwalls of slumps, which has solute concentrations nearly 100 times higher than those measured in the uppermost 1–2m (i.e., above the early Holocene thaw unconformity). An examination of ionic relations revealed a strong relation between Ca2+ and SO4 2− and (Ca2++Mg2+)–SO4 2−, suggestive that sulfate dissolution is the main process responsible for the geochemical composition of slump impacted streams. Thaw slumps significantly impact the geochemistry of streams, by increasing their solute load well above that of pristine streams along any reach of impacted streams. Unlike shallow active layer disturbances, the thaw slumps can degrade permafrost to depths of 10m or more and the impacts of abundant slump activity on stream geochemistry can be detected at the 10^2 km2 watershed-scale. [Copyright &y& Elsevier]

Abstract: This study presents new ages for the northwest section of the Laurentide Ice Sheet (LIS) glacial chronology from material recovered from two retrogressive thaw slumps exposed in the Richardson Mountains, Northwest Territories, Canada. One study site, located at the maximum glacial limit of the LIS in the Richardson Mountains, had calcite concretions recovered from aufeis buried by glacial till that were dated by U/Th disequilibrium to 18,500calyr BP. The second site, located on the Peel Plateau to the east yielded a fossil horse (Equus) mandible that was radiocarbon dated to ca. 19,700calyr BP. These ages indicate that the Peel Plateau on the eastern flanks of the Richardson Mountains was glaciated only after 18,500calyr BP, which is later than previous models for the global last glacial maximum (LGM). As the LIS retreated the Peel Plateau around 15,000calyr BP, following the age of the Tutsieta phase, we conclude that the presence of the northwestern margin of the LIS at its maximum limit was a very short event in the western Canadian Arctic. [Copyright &y& Elsevier]

Abstract: The geochemistry, mineralogy and microbiology of bacteriogenic iron oxides (BIOS) deposited at a circumneutral groundwater seep were examined to evaluate the biogeochemical controls on the redox cycle of iron in such environments. X-ray diffraction and extended X-ray absorption fine structure (EXAFS) spectroscopy showed that 2-line ferrihydrite dominated (60–70%) the BIOS mineralogy, with more crystalline lepidocrocite and goethite phases comprising the remainder, likely the product of Fe(II)-induced dissolution–reprecipitation pathways. Subsurface porewater profiles displayed an increase in dissolved (<0.2μm) equilibrium concentrations of Fe(II), also reflected in peaks in HCl-extractable sedimentary Fe(II) at depth, indicative of biological iron reduction. Interestingly EXAFS analysis of sediments collected from such depths revealed little mineralogical change from the surficial BIOS. Dissolved concentrations of Fe(III), likely present as nanoparticulates or organic complexes, also rose with depth. Scanning electron microscopy images of the surface BIOS samples showed a proliferation of sheath structures characteristic of Fe(II)-oxidizing Leptothrix spp. A 16S rRNA clone library obtained from the surficial BIOS included microorganisms closely associated to known Fe(II)-oxidizing (Gallionella spp., Sideroxydans spp.) and Fe(III)-reducing (Rhodoferax ferrireducens and Geothrix fermentans) bacteria. Analysis of subsurface sediment collected from an Fe(III)-reducing horizon revealed a drop in the proportion of β-Proteobacteria, which hosts numerous Fe(II)-oxidizing genera, and a rise in the δ-Proteobacteria, home to anaerobic metal-reducing prokaryotes. The recognition of clones with close identity to bacteria intimately involved in complementary iron redox transformations in the same surficial BIOS sediment suggests that microbial oxidation and reduction of iron may be tightly coupled in this, and other, shallow sedimentary environments. [Copyright &y& Elsevier]

In this study, the sediments exposed in a fluvial terrace and in the headwall of a thaw slump in ihc Eagle River valley, northern Yukon, provide new data about the timing of Hooding of glacial Lake Old Crow, the I'ormalion (if massive ground ice bodies, and the vegetation and the launa in eastern Beringia during ihe late Quaternary. The .straiigraphy 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 14C year BP; (3) permafrost and large intrusive ice bodies aggraded through ihe glaciolacustrine and underlying sediments following the drainage ot glacial Lake Old Crow from the site; (4) at 11 290 14C year BP, a shrub-sedge tundra colonized an uneven surface deformed by the bodies of ground ice; (5) a thaw lake drained at 6730 14C 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 12210 ± 70 14C year BP. The age from the bison bone is amongst the most recent of the late Pleistocene bison specimens yet found in eastern Beringia. [ABSTRACT FROM AUTHOR]

Abstract: This study describes the origin and age of a body of massive ground ice exposed in the headwall of a thaw slump in the Red Creek valley, central Yukon, Canada. The site is located beyond the limits of Pleistocene glaciation in central Yukon and within the southern limit of the modern continuous permafrost zone. The origin of the massive ground ice, which is preserved under a fine-grained diamicton containing thin layers of tephra, was determined through ice petrography, stable O-H isotope composition of the ice, and gas composition of occluded air entrapped in the ice. The age of the massive ground ice was established by identifying the overlying tephra and radiocarbon dating of a “muck” deposit preserved within the ice. Collectively, the results indicate that the massive ground ice formed by snow densification with limited melting-refreezing and is interpreted as being a buried perennial snowbank. The muck deposit within the ice, which yielded an age of 30,720±340 14C a BP, and the Dawson tephra (25,300 14C a BP) overlying the perennial snowbank, indicates that the snowbank accumulated at roughly the transition between marine isotope stages 3 and 2. Dry climatic conditions at this time and possibly high winds enabled the snowbank to accumulate in the absence of extensive local valley glaciation as occurred in the mountains to the south. In addition to documenting the persistence of relict permafrost and ground ice to warming climate in regions where they are predicted to disappear by numerical models, this study presents evidence of an isotopic biosignature preserved in a body of massive ground ice. [Copyright &y& Elsevier]

Abstract: The effect of microbial reduction of bacteriogenic iron oxides (BIOS) on the release of sorbed Sr was examined using a naturally low-Sr BIOS (n-BIOS) collected from Chalk River, Canada, and a naturally high-Sr BIOS (Äspö-BIOS) collected from Äspö, Sweden. EXAFS analysis suggested that Sr was bound to the Äspö-BIOS as an outer-sphere complex of hydrated Sr2+. During reduction, Sr desorption from n-BIOS was concomitant with the production of Fe(II), resulting in solubilization of 80% of the total Sr. In contrast, nearly 100% of the Sr was solubilized from Äspö-BIOS, although Sr desorption was delayed, relative to Fe(II) production. When n-BIOS were artificially saturated with Sr, there was a significant decrease in the rate and extent of Fe(III) reduction and an induced delay in Sr desorption (similar to that observed for Äspö-BIOS). Saturation of synthetic hydrous ferric oxide with Sr had no such effect on Fe(III) reduction rate, although a delay in Sr desorption was again observed. In all instances, the levels of desorbed aqueous Sr remained constant, suggesting that re-sorption or co-precipitation of Sr with secondary mineral precipitates (vivianite) did not occur under the experimental conditions. In situ porewater analysis of the Chalk River BIOS indicated positive correlations between soluble-phase concentrations of Fe(II) and Sr at depth, suggesting that anaerobic reduction of Fe(III) releases Sr back into the groundwater flow at the site. Further, in areas where BIOS deposition is occurring within the groundwater discharge zone, levels of soluble Sr are 2 to 3 times lower than in areas where BIOS is absent. The data indicate that phase partitioning of Sr within BIOS is governed largely by Fe oxidation state, and that BIOS will act as effective sorbents of Sr as long as oxidizing conditions are maintained. However reduction of the BIOS will likely result in significant desorption and remobilization of the bound Sr. [Copyright &y& Elsevier]