thermokarst lake basin sediments tuktoyaktuk coastlands western arctic canada three stages of deposition are distinguished in thermokarst lake basin sequences in ice rich permafrost of the tuktoyaktuk coastlands western arctic canada 1 widespread retrogressive thaw slumping around lake margins that rapidly transports upland sediments into thermokarst lakes forming a distinctive basal unit of impure sand and or diamicton 2 a reduction or cessation of slumping because of the pinching out of adjacent ground ice slump stabilization or climatic cooling that reduces the input of clastic sediment permitting reworking of sediment around lake margins and suspension settling principally in basin centres 3 lakes drain and deposition may continue by gelifluction and accumulation of in situ peat or aeolian sand radiocarbon dating of detrital peat and wood from a progradational sequence basal unit defines a lateral younging trend in the direction of progradation a progradation rate is calculated to be 4 cm yr 1 consistent with rapid deposition during stage 1 above the nonuniform nature of the trend is attributed to episodic influxes of old organic material by slumping and reworking by waves and currents in comparison with thermokarst lake basin sequences previously described in alaska canada and siberia the middle unit of those in the tuktoyaktuk coastlands is similar whereas the basal unit is generally thicker and by contrast often contains diamicton these differences are attributed respectively to larger scale resedimentation of upland sediments by retrogressive thaw slumping and debris flow deposition in thermokarst lakes in the tuktoyaktuk coastlands compared with the sediments within supraglacial lakes in areas of moderate to high relief the middle unit of thermokarst lake basin sequences in the tuktoyaktuk coastlands lacks clastic varves and the basal unit is much thinner and texturally less variable these differences are attributed to higher relief and larger volumes of meltwater and glacigenic sediment in supraglacial lakes which promote more suspension settling and resedimentation of glacigenic sediment than in thermokarst lakes in the tuktoyaktuk coastlands it may be impossible to distinguish glacial and periglacial thermokarst lake basin sediments in permafrost areas of incomplete deglaciation not only is it often difficult to distinguish intrasedimental and buried glacier ice but the depositional processes associated with thaw of both ice types are presumably the same and the host sediments very similar

late holocene diatom biostratigraphy and sea level changes in the southeastern beaufort sea late holocene sediments from the atkinson point area were analysed to provide quantitative reconstructions of recent sea level changes in the southeastern beaufort sea the succession of diatom assemblages in five cores revealed paleoenvironmental changes induced by the transgression of the beaufort sea during successive periods of lacustrine conditions breaching and flooding of thermokarst lakes by the sea and the landward migration of sandy spits based on radiocarbon dates and quantitative paleodepth determinations a relative sea level curve for the late holocene has been developed despite a loss of temporal precision due to old carbon contamination an envelope of sea level change has been defined for the last 2 ka bp suggesting a sea level rise in the order of 1 1 mm a 1 for the last millennium this paper presents the first sea level reconstruction inferred from a diatom based transfer function it represents an improvement over traditional methods which were limited to qualitative estimates of

spatial distribution of coarse woody debris dams in the lymington basin hampshire uk abstract debris dams of coarse woody debris have a significant influence on channel processes in forested areas but few detailed studies have been made of variations within a single basin results from previous research are standardised and show that average variations throughout basins include densities of debris dams up to 40 per 100 metres of channel and can involve a loading value of up to 225 kg per m2 of channel variations have been ascribed to distance downstream to channel width to land use effects to felling and to the management of coarse woody debris in streams this study of the lymington basin 110 4 km2 in drainage area shows that the input of storm debris resulting from blowdown accounts for 45 of the gross load the remaining 55 net load varies to distance downstream to land use with the greatest loads in deciduous woodland areas and according to management removal of debris from streams and multiple regression equations are provided it is deduced that as a consequence of long term management the present channel debris may be as little as 7 of the total net load that could have been present if no management had occurred

high resolution stable water isotopes as tracers of thaw unconformities in permafrost a case study from western arctic canada abstract the knowledge of past permafrost conditions is of importance to assess the potential magnitude of changes that periglacial environments may experience as a result of climate warming or disturbance to assess if past thaw unconformities may be preserved from isotopic and geochemical discontinuities within permafrost this study investigates the distribution of ground ice stable water isotopes and major cations in two permafrost cores collected in a hummocky terrain site near inuvik northwest territories canada a site where the evolution of the active layer during a recent period of permafrost degradation and subsequent aggradation was documented based on the high resolution isotope geochemistry profiles closed system rayleigh type ionic segregation and isotope fractionation occurred during thermally induced water migration into shallow permafrost and its freezing along a negative soil temperature gradient due to thermally induced water migration into permafrost 18 o may not always be able to identify thaw unconformities however the calculation of the 18 o enrichment factors between ice and water e 18 o i w may be used to determine position of thaw unconformities in permafrost if thaw events are followed by permafrost aggradation the approach of using e 18 o i w provides additional information regarding past permafrost conditions that can complement change in cryostructures observed along natural exposures

the assessment of ree patterns and 143nd 144nd ratios in fish remains abstract the ree content and isotopic composition of sr and nd have been determined in fish teeth ranging in age from the trias to the present and from various localities mostly around the atlantic these measurements have been carried out on selachian and teleost remains from the same locality in togo and show no appreciable difference which suggests with the help of a mass balance calculation of the ce anomaly that diagenetic effects are not responsible for the ree enrichment of biogenic phosphates one group of fossil teeth has about 3 times the ree abundances of shale and a shale normalized pattern with a minimum at sm it is thought to reflect deposition in the open sea environment a second group has ree concentration about 10 times higher than the first group with either a regular light ree enrichment or more frequently a maximum in the middle ree both being probably indicative of deposition in estuarine or near shore conditions the shape of the ree spectra and the size of the ce anomaly can be used semi quantitatively to determine the depth of deposition the results presented here on late cretaceous eocene fish teeth samples from morocco reflect an increasing influx of deep waters with a lowla yb ratio and strong negative ce anomaly which agrees well with the evolution of sediment chemistry and microfauna associations in contrast nd is typical of the water mass in which the fish debris decayed examples of nearly isolated basins identified with nd isotopes include the south atlantic prior to the lutetian nd 13 5 the miocene persian gulf nd 3 1 and bolivia during the late cretaceous nd 12 8 togo and guinea bissau results suggest that in the south atlantic the meridional oceanic circulation had not started before 45 ma ago combination of ree and nd data suggests that the assignment of jurassic cretaceous samples measured so far to open sea water masses is still ambiguous

enriched 13c composition of interstitial waters in sediments of a freshwater lake the dic dissolved inorganic carbon of interstitial waters from sediments of a small carbonate precipitating lake in southern ontario has highly enriched 13c values of up to 13 relative to pdb peedee belemnite this post depositional isotopic enrichment is attributed to the metabolism of methanogenic bacteria the 13c values of marl in the sediment profile are also enriched by an average of 3 to 4 relative to the associated molluscs photosynthetically induced carbonate precipitation and post depositional recrystallization are among the processes that are considered to contribute to the isotopically enriched marls evidence for the latter process is drawn from geochemical analyses on interstitial waters which show them to be at or very close to saturation with respect to calcite indicating that net calcite dissolution has occurred probably under the influence of high pco2 s generated by methanogenic bacteria such freshwater carbonate sediments with interstitial waters enriched in 13c provide

isotopic and geochemical composition of marl lake waters and implications for radiocarbon dating of marl lake sediments radiocarbon dates on organic and calcareous fractions of sediment cores from marl lakes may yield anomalous ages due to the assumption of a constant hardwater correction factor along the sediment sequence a study of eight marl lakes in southern ontario that are actively precipitating calcium carbonate was conducted in order to assess those isotopic and aqueous geochemical parameters in modern lakes that may be utilized to estimate the history and extent of variations in the hardwater effect along such sediment sequences results show an increase in the 13c composition of lake dic dissolved inorganic carbon as approach to isotopic equilibrium with atmospheric co2 occurs differences in the extent to which this equilibrium is established also appear responsible for observed differences in the 14c activity of dic between lakes of as much as 20 pmc percent modern carbon these variations have been related to the relative residence times of water in each lake by examination of their corresponding seasona

diet preferences and climate inferred from oxygen and carbon isotopes of tooth enamel of tarbosaurus bataar nemegt formation upper cretaceous mongolia abstract stable isotopes of oxygen and carbon of tooth enamel are increasingly being used as tracers to study palaeoecology and the diet preferences of fossil vertebrates we serially sampled tooth enamel carbonate along the growth axes of five early maastrichtian carnivorous dinosaur teeth tarbosaurus bataar tyrannosaurid from the nemegt formation mongolia in order to identify seasonal climatic variations and determine the diet of this apex predator additional bulk samples of dentine bone and surrounding sediment were analyzed in order to exclude diagenetic obfuscation of the isotopic record enamel samples of potential prey species for dietary studies were also analyzed in the case of the largest specimens the sampled teeth usually recorded annual cycles ranging between two thirds and a full year fluctuations in 18o values in tyrannosaurid teeth suggest seasonality high annual temperatures with distinct precipitation humidity maxima during summer months with mean annual temperatures mat ten degrees higher than those of present day mongolia the seasonal pattern of 18o shows similarities to that of the modern day shijiazhuang global network of isotopes in precipitation station northern china and suggests that the nemegt biota flourished when exposed to a cool temperate monsoon influenced climate herbivore and carnivore carbon isotopes 13c values from tooth enamel imply the presence of a woodland ecosystem dominated by coniferous trees such as araucariaceae and are consistent with the hypothesis that large sauropods and hadrosaurids were the preferred prey of tarbosaurus mean annual precipitation map based on the relationship between modern day c3 gymnosperms and local average map is estimated at 775 835 mm yr these results show that large theropod teeth can serve as valuable archives for palaeoenvironmental studies

thaw lake expansion in a two dimensional coupled model of heat transfer thaw subsidence and mass movement 1 thaw lakes widespread in permafrost lowlands expand their basins by conduction of heat from warm lake water into adjacent permafrost subsidence of icy permafrost on thawing and movement of thawed sediment from lake margins into basins by diffusive and advective mass wasting we describe a cross sectional numerical model with thermal processes and mass wasting to test the model and provide an initial investigation of its utility the model is driven using historical daily temperatures and permafrost conditions for the northern seward peninsula alaska nsp thick syngenetic ice mean annual air temperature maat 6 c and yukon coastal plain ycp thin epigenetic ice maat 10 c in the model lakes develop dynamic equilibrium profiles that are independent of initial morphology these profiles migrate outward episodically and match the morphology of profiles from lakes that were measured at each site modeled nsp lakes expand more rapidly than ycp lakes 0 26 versus 0 10 m a 1 under respective modern climates when identical climates are imposed nsp lakes still grow more rapidly because their deeper basins and steeper bathymetric slopes move thawed insulating sediment away from the lake margin in sensitivity tests an increase of 3 c in maat causes 2 5 nsp and 1 6 ycp faster expansion of lakes an 8 c decrease essentially halts expansion for both sites consistent with paleostudies which attribute basins to postglacial warming in the model basins expand monotonically but lakes do not the 1 interannual variability of lake expansion is 0 51 nsp and 0 44 m a 1 ycp with single year rates of up to 8 m occurring because of instabilities from thermal mass movement coupling even under a stationary climate this variability is likely a minimum estimate compared to natural variability and suggests that long measurement time series of basins not lake surfaces would best detect thermokarst acceleration resulting from a climate change

palaeoenvironments of the late triassic rhaetian sea implications from oxygen and strontium isotopes of hybodont shark teeth the oxygen and strontium isotopic composition of 125 teeth of the hybodont sharks lissodus and hybodus from various late triassic rhaetian bone bed localities in the central european basin are used as environmental and ecological tracers for the shallow epicontinental rhaetian sea the preservation of tooth enameloid was ascertained by cathodoluminescence microscopy mean 18op values differ regionally across the rhaetian sea with values of 18 6 0 6 near the western gate 16 1 0 8 in the east 15 4 0 6 in the southeast and 17 7 0 9 in the south the 18op values in the eastern rhaetian sea are 4 5 lower relative to tethyan seawater while teeth from the southern and western parts close to the marine gates are less fractionated the strontium isotopic composition of teeth from most localities is more radiogenic in comparison to late triassic seawater the observed spatial 18op trend in the rhaetian sea indicates a shift from marine to brackish conditions in the south and west towards extensively brackish conditions with salinities of less than 16 in the east thus confirming the existence of two marine gates brackish conditions persisted throughout early rhaetian times and were maintained by increased fluvial discharge from the vindelician bohemian and fennoscandian highs as a result of enhanced atmospheric moisture availability in the course of the rhaetian transgression the 18op values of lissodus and hybodus indicate euryhaline behaviour of rhaetian hybodonts by exceeding modern shark intraspecific variability the lack of accordance in 18op values between different isotopically conspicuous localities in the rhaetian sea contradicts a basin wide migration pattern differences between co site taxa might indicate some degree of niche partitioning

the incorporation of uranium into diagenetic phosphorite abstract the behavior of u during the diagenetic formation of marine phosphorite has been modelled the model examines a dissolution reprecipitation replacement of skeletal hydroxyapatite calcium carbonate and earlier generated francolite by francolite the amount of organic matter consumed relative to the mass of francolite formed the replacement reaction progress and the concentration of u in the replaced phases are the important parameters which dictate the concentration of u in the phosphate rock a partition coefficient between apatite and interstitial solution was calculated and is u f 0 57 natural phosphorites have been examined and are discussed in the light of the proposed model the u mass balance in a recent phosphorite is in good accord with theoretical predictions differences in u concentrations between sea floor phosphorites are explained either by the original variation in the organic matter distribution in the corresponding sediments and or by mineralogical differences caco3 vs hydroxyapatite therein senonian phosphate rocks which were formed via the francolite francolite transformation demonstrate that during that process the organic matter content in the sediment was approximately 50 the model supports the idea that phosphorite rock formation is a multistage process

a full scale field experiment 1978 1995 on the growth of permafrost by means of lake drainage western arctic coast a discussion of the method and some results on 13 august 1978 a lake on the western arctic coast was artificially drained in a multidisciplinary experiment on the growth of permafrost on the unfrozen bottom of the drained lake a bowl shaped talik unfrozen basin with a maximum depth of about 32 m underlay the lake bottom prior to drainage in the first winter after drainage downward freezing started on the exposed lake bottom and upward freezing from permafrost beneath the talik after drainage the soft lake bottom sediments hardened from water loss and freeze thaw consolidation gradual thinning of the active layer at many sites was accompanied by ground uplift and the growth of aggradational ice downward and upward freezing has resulted in solute rejection freezing point depressions pore water expulsion from the freezing of the saturated lake bottom sands and convective heat transfer from groundwater flow in an open hydrologie system the increasingly saline intrapermafrost groundwater flowing at an increasingly negative temperature be

cathodoluminescence tools provide clues to depositional history in miocene and pliocene mammalian teeth abstract this paper presents the results of a study which used cathodoluminescence cl observations optical images and sem spectra as a tool for assessing diagenetic processes during fossilisation of continental mammalian teeth the study was performed on fossil teeth of large mammals gomphotheriidae rhinocerotidae and hippopotamidae from namibia and from kenya with ages from the lower and middle miocene to pliocene the fossil sites are distinguished by their environmental conditions they include floodplain deposits fluvial deposits of the proto orange river and aeolianite deposits in namibia and fluvio lacustrine deposits of different ages in kenya optical cl provides information about the sites environments and diagenetic processes related to those environments a blue intrinsic luminescence for the aeolianite deposits and purple to yellowish for floodplain or fluvial deposits the cl spectra of these samples show sharp emission bands which are classically related to late recent incorporation of rare earth elements ree substituting in the ca 2 sites high resolution mapping of the distribution of these ree shows a gradient from the enamel interior low concentrations to the outer enamel margin high concentrations

cryostratigraphy paleogeography and climate change during the early holocene warm interval western arctic coast canada botanical and cryostratigraphic records from northwest canada indicate that the climate of the early holocene was considerably warmer than today tree line was over 100 km farther north and a thaw unconformity dating from 8000 14c years bp formed at the base of an active layer 2 5 times thicker than at present numerous thermokarst lake basins formed in the preceding millennia both the botanical and cryostratigraphic indices described are products of summer conditions previous reconstructions of early holocene climate have not assessed the significance of paleocoastal location on the seasonality and extent of apparent climate warming at present there is a steep gradient in growing season conditions between cooler sites on the beaufort sea coast and warmer inland locations winter conditions are more uniform because both sea and land are snow covered coastal retreat in the region has been rapid due to sea level rising over a gently sloping shelf containing readily erodible sediments the coastlin

evidence of climatic change from oxygen and carbon isotope variations in sediments of a small arctic lake canada radiocarbon dating of the organic rich sediments of lake illisarvik in the outer mackenzie delta indicates that formation of the lake occurred approximately 9500yr bp with maximum expansion around 6000 yr bp sedimentation rates have remained relatively constant at an average of 0 3mm yr 13c results on biogenic and inorganic carbonates and organics indicate a change from dominantly terrestrial organics 27 to 28 0 to submerged aquatic vegetation or plankton 18 to 23 0 upon formation of the lake 9500yr bp and a dramatic return to dominantly terrestrial organics at 5800yr bp 13c 27 to 30 0 this latter shift is accompanied by a drastic reduction in the macroflora and fauna populations 18o results suggest that a warmer climate than today existed prior to the shift at 5800yr bp

physical and temporal factors controlling the development of near surface ground ice at illisarvik western arctic coast canada near surface permafrost was sampled in summer 2010 at 26 sites in the illisarvik drained lake basin and nine sites in the surrounding tundra on richards island nwt to investigate the growth of segregated near surface ground ice permafrost and ground ice have developed in the lake basin since drainage in 1978 the lake bed soils are predominantly silts of varying moisture and organic matter contents with sandier soils near the lake margins excess ice contents in the basin were also variable and ice enrichment was observed to a maximum depth of 60 cm below the 2010 permafrost table shrub covered wet areas had the highest mean excess ice content in the top 50 cm of permafrost 10 while grassy dryer areas 4 and poorly vegetated marginal areas 1 were less enriched with ice site wetness was the most important variable associated with near surface excess ice content in the lake basin silt content was a secondary variable mean excess ice content in the top 50 cm of permafrost at tundra sites

ice wedges on hillslopes and landform evolution in the late quaternary western arctic coast canada in rolling to hilly areas of the western arctic coast of canada anti syngenetic wedges which by definition are those that grow on denudational slopes are the most abundant type of ice wedge through prolonged slope denudation hilltop epigenetic wedges can evolve into hillslope anti syngenetic wedges and some bottom slope anti syngenetic wedges by means of deposition from upslope can evolve into bottom slope syngenetic wedges the axis of a hillslope wedge is oriented perpendicular to the slope so the wedge foliation varies according to the trend of the wedge with respect to the slope because the tops of hillslope wedges are truncated by slope recession the mean chronological age of anti syngenetic wedge ice decreases with time so the growth record for an old wedge is incomplete summer and winter measurements show that a thermally induced net movement of the active layer of hillslope polygons tends to transport material from their centres towards their troughs independent of the trends of the t

ecological and physiological variability of sr ca and ba ca in mammals of west european mid wurmian food webs the middle to upper paleolithic transition in western europe is characterized from an ecological point of view by large ungulate communities adapted to cold climatic conditions the aim of this study is to reconstruct the trophic relationships prevailing in these paleoecosystems which have no equivalent in the modern world bone and dentine remains representing five mammalian assemblages dated around 35 ka bp one of which included a neandertal specimen are investigated for sr ca and ba ca of bioapatites examination of the n content and u ree luminescence of bulk material ca p ratios and mn and ca contents of purified samples demonstrates that the sr ca and the ba ca ratios of bone and dentine samples are not significantly altered by diagenesis as a consequence of the biological discrimination of sr and ba in relation to ca sr ca and ba ca values are impoverished with increasing trophic position and are strongly correlated within a trophic web the slopes of the linear regressions between sr ca and ba ca are consistent with modern variability furthermore a statistical difference was found between ba ca of foregut and hindgut herbivores when coexisting collagen is preserved the sr ba ca and 15n are strongly correlated the distribution of values suggests that the 15n range is mainly controlled by the variability of soil conditions whereas the 13c range may be related to resource availability

time dependent morphology of thaw lakes and taliks in deep and shallow ground ice 1 the shape and depth of thaw lake basins depends on lake age on whether the talik thaw bulb is at steady state and on the distribution of ice in the ground to investigate implications of this broad hypothesis we use a numerical model of conductive heat transfer phase change and thaw subsidence of ice rich sediment beneath a lake in cross section for ground thermal properties with lake temperatures and dimensions consistent with measurements modeled talik depth approximately increases with except in lakes in deep ground ice which deepen more rapidly because of consolidation on thawing in deep ground ice environments basins achieve depths of 20 m in 5 ka expanding lakes with disequilibrium taliks have deep basins with broad 100 m wide inclined margins in shallow ground ice settings either original epigenetic ice or in permafrost that has reformed in drained basins lakes are 3 m deep and flat bottomed unaffected by preexisting topography and ground ice variations first generation lakes in deep ground ice are rounder and grow larger in area than later generation lakes these predictions are consistent with gps sonar and remote sensing measurements of bathymetry and plan view shape of first and later generation lakes in substrates with deep syngenetic ground ice pleistocene loess northern seward peninsula alaska and shallow epigenetic ice yukon arctic coastal plain

diffusion of rare earth elements in fish teeth from deep sea sediments the distribution of rare earth elements rees in biogenic phosphate phases in sediments such as the remains of fish teeth has been proposed as an indicator of the depositional environment in the water column recording for example palaeo redox conditions1 and isotope geochemical2 5 and hydrothermal6 7 processes enrichment of these phases in rees takes place only during early diagenesis8 9 for which reason the ree signal has often been assumed to represent the unfractionated record of ree distribution in the water column overlying the sediment surface1 4 5 10 here we report on studies of ree zoning in fish teeth from pacific sediments from which we extract a ree diffusion coefficient of 70 mm2 myr 1 this value suggests that diffusion of rees from sea water into the fish teeth before burial is too slow to produce the enrichments observed instead the ree distributions must derive from the surrounding sediment pore fluids the use of these distributions as palaeoceanographic indicators is therefore called into question

the ree and end of 40 70 ma old fish debris from the west african platform ree concentrations and nd isotopic compositions have been determined in late cretaceous early cenozoic fish debris from west african and israeli platform sediments and show a strong regional control independent of time except for those from the northern morocco it is suggested that although diagenetic fluids do not contribute ree s directly to the phosphatic debris they may significantly change the ce anomaly and the end t value of the epicontinental seas which in turn control the ree in marine phosphates it is shown that over the investigated period the north moroccan shelf seawater was progressively flushed by deep north atlantic water

evidence from north west canada for an early holocene milankovitch thermal maximum according to the milankovitch theory of global climatic change maximum summer solar radiation at high latitudes of the northern hemisphere occurred at 10 000 yr bp refs 1 2 in particular it predicts summer solstice radiation greater by 9 10 preliminary climate simulation experiments with these increased values of radiation confirm that high latitude land surfaces received maximal insolation at 10 000 yr refs 3 4 paradoxically however the large volume of fossil pollen and other evidence from north america indicates a maximum of holocene warmth at 7 000 6 000 yr ref 5 and a recent review of the evidence from new england suggests that the warming began at 9 000 and ended at 5 000 yr but also stresses the difficulties of interpretation in terms of climate change6 we summarize here data from sites in the north west corner of mainland canada fig 1 that directly support the milankovitch hypothesis

luminescence of uranium bearing opals origin and use as a ph record abstract fluorescence of minerals has been long used for u exploration it is proposed here that opal fluorescence can be used as a probe of the ph of the formation solution bringing constraints for modeling u speciation and sequestration at the earth s surface we present a study of fluorescence spectroscopy of u in opals resulting from low temperature 29 c alteration of mineralized rhyolitic lavas nopal i u deposit sierra pena blanca mexico these opals show green fluorescence with a concentric distribution at microscopic scale which is unambiguously assigned to uranyl groups oxidized form of u spectra appear typical of uranyl in opal as reported in literature for other localities according to peak positions when considering also the lifetime of fluorescence spectra with time resolved laser fluorescence spectroscopy fingerprinting indicates that uranyl occurs either as phosphate or hydroxo polynuclear complexes trapped onto the opal internal surface data are indicative of a ph of opal formation around 8 as derived from both conditions of laboratory experiments and reference to calculated diagrams of speciation this ph value is consistent with the nopal geological formations that were potentially in contact with the aquifer involved in the hydrothermal process in addition the microscopic zoning of u suggests that the speciation has been stable since opal formation more than 50 ka ago which allows the record of ph that prevailed at that time

tundra lakes and permafrost richards island western arctic coast canada lakes of average size 33 ha occupy a quarter of the surface area of richards island northwest territories most of the lakes have a central pool deeper than the thickness of winter ice and many have prominent shallow littoral terraces the relatively warm lake bottoms cause considerable disturbance to the surrounding continuous permafrost water and lake bottom temperatures the configuration of permafrost and active layer thickness were measured at a tundra lake between 1992 and 1997 the lake is oval 1 6 km long 800 m wide and as deep as 13 m sandy terraces covered by less than 1 m of water extend over 100 m from the shore the terraces are underlain by permafrost which terminates almost vertically at their edge the annual mean temperature measured at lake bottom in the central pool ranged between 1 5 c and 4 8 c depending on depth and between 0 2 c and 5 c on the terraces due to differences in snow cover and proximity to the central pool in consequence the temperature of permafrost at 7 m depth in the terraces also varied from 2 c near shore to 5 c in mid terrace the active layer in the terraces was uniformly 1 4 m deep geothermal modelling of talik configuration indicates that there is no permafrost beneath the central pool of the lake the modelling indicates that under equilibrium conditions about one quarter of the lakes on richards island have taliks that penetrate permafrost and at least 10 15 of the island is underlain by talik short term climatic changes predicted for the region imply a small increase in summer lake water temperature and an extension of the open water season accompanied by thicker snow cover in winter following such changes with longer freeze up and warmer terrace temperatures in winter permafrost may not be sustainable in the lake terraces

holocene climate effects on the development of a peatland on the tuktoyaktuk peninsula northwest territories abstract six cores were collected from a small peatland on the tuktoyaktuk peninsula yielding up to 1 8 m of organic material and 1 2 m of ice rich material stratigraphic relationships radiocarbon dating and pollen plant macrofossil and isotopic analyses are used to reconstruct the developmental history of the peatland organic matter began to accumulate in the basin about 7200 yr b p during a period when the climate is thought to have been warmer than present initially the permafrost table was probably below the bottom of the basin and an open water mineral wetland with emergent and submergent aquatic vegetation occupied the site enriched 18 o values from ice samples confirm the existence of an open water body with a water balance strongly affected by evaporation transformation to a graminoid fen peatland was underway by 6300 yr b p permafrost and ice began to form in the peatland at this time low centered polygons probably began to develop by 4700 yr b p and subsequently evolved into the high centered polygons which characterise the southwestern part of the peatland today peat accumulation in the polygons has been extremely slow for the last 4000 years the eastern wetter part of the basin has largely remained unchanged since its inception about 7000 yr b p development of the peatland may be linked to permafrost formation that was controlled by regional climate changes during the holocene

geochemistry and extractable fe and al in cold temperature soils of northwestern siberia the concentrations of major minor and trace elements in three cryosols from north western siberia were analysed to determine profiles of geochemical uniformity element mobility and the release and build up of extractable fe and al the scope of this study involves weathering processes over all or part of the lateglacial to the holocene epoch 10 ka bp q1 in a cold environment the variability of hf content in the horizons is likely silica induced and accounts for much of the concentration variation in the other elements the slight increases of mobile to immobile elements in the b horizons indicate trivial downward movement within the profiles iron and al extracts were investigated to elicit information regarding profile age and palaeoclimate extractable fe and al show slight increases relative to the total concentrations in the soil sola ah bw horizons lattice fe decreases in the ah bw horizons as a result of weathering and production of sesquioxides over time increases of ferrihydrite in the ah horizons and in the parent material of some profiles may indicate perched water tables at some time in the past possibly as sustained yearly water levels in the active layer free iron fed relative to total fe increases in the ah bw horizons compared with the lower horizons where the oxidation potential is weaker low total fe reflects reworked felsic rich deltaic and shallow marine deposits from the permian to the early tertiary thereafter emplaced by episodic flooding of glacial meltwater from the arctic urals and or the kara sea ice sheet organically complexed al alp uniformly low in all soils nevertheless shows trends indicating some downward movement a rather unique occurrence in arctic tundra soils as indicated by the slow increase of oxihydrites it may not be realistic to estimate the age of a profile by its physical characteristics however it appears possible to determine broad age ranges from the isotopic composition of water in soils organic carbon concentrations between and within soil profiles indicate it may be more prevalent in tundra soil than previously thought and may also play a significant role in uploading co2 to the atmosphere as warming and microbial activity q2 progresses copyright 2009 john wiley sons ltd

the first 20 years 1978 1979 to 1998 1999 of active layer development illisarvik experimental drained lake site western arctic coast canada active layer thickness snow depth minimum soil temperatures near surface ground ice soil heave and permafrost temperatures have been measured for over 20 years following the 1978 artificial drainage of lake illisarvik measurements of active layer thickness and other variables have been made at 25 m intervals along the major and minor axes of the oval shaped drained lake bed permafrost aggradation commenced in the lake bottom during the first winter following drainage before the establishment of vegetation there was little snow cover minimum ground temperatures were low and the active layer was relatively thin however both snow depth and minimum ground temperatures have risen where vegetation has grown the active layer has thickened and in response the temperature in permafrost has gradually increased in the lake bottom the change in snow depth associated with vegetation growth has been the dominant control on variation in active layer thickness and not summer weather conditions which ar

luminescence of uranium and rare earth elements in apatite of fossil fish teeth abstract time delayed laser induced luminescence of uranium and rare earth elements ree in apatite of fossil fish teeth from the phosphorites of the senonian mishash formation israel were investigated before and after thermal treatment the unheated samples show luminescence of uo 2 2 luminescence of ree 3 sm eu pr is observed only after heating the samples at 1100 k in air the spectral properties indicate that uo 2 2 in the unheated samples is located in two different positions as aqua complexes of uranyl ions and associated with organic matter the ree in the unheated samples are accommodated in non luminescent form after heating the ree 3 sm eu pr are located in the ca 2 ii site presumably due to thermal diffusion

oxygen and strontium isotopes from fossil shark teeth environmental and ecological implications for late palaeozoic european basins article i nfo fossil shark remains occur in both marine and nonmarine late palaeozoic deposits therefore their palaeo ecology is controversial the oxygen and strontium isotopic composition of biogenic fluorapatite in 179 teeth scales and spines predominantly of hybodontid lissodus and xenacanthiform orthacanthus xenacanthus bohemiacanthus triodus sharks from various late carboniferous moscovian to early permian artinskian basins of europe are used as ecological tracers to decipher diadromous or obligate freshwater lifestyle of the investigated taxa the 18 op values of the different shark teeth range from 11 7 to 20 2 within the different basins with mean values of 16 9 0 5 for the bohemian massif 16 2 0 8 for eastern germany 18 2 1 0 for southwestern germany 18 5 0 7 for southern central spain 17 6 0 4 for