shallow burial dolomitization and dedolomitization of cenozoic cool water limestones southern australia geochemistry and origin abstract the gambier limestone a bryozoan rich cool water carbonate of late eocene to early miocene age in the otway basin of southeastern australia is about one third variably dolomitized limestone and dolostone individual dolomite crystals range from 10 to 500 m and are of three types 1 silt size crystals 4 64 m diameters having a brightly luminescent core 10 20 m of nearly stoichiometric dolomite with 1 mol mnco3 and sio2 but no fe surrounded by a thin dull or alternating dark and bright cl cortex that is nonstoichiometric with 44 46 mol mgco3 but sharp to diffuse zoning in mn and fe 2 sand size crystals which also have a brightly luminescent and stoichiometric core and dark and bright non stoichiometric thin inner cortex but are mostly a thick outer cortex at ca 50 m diameter that is nonluminescent and nonstoichiometric with some fe but no mn and 3 identical sand size crystals with a variably leached core and inner cortex that is either a void or a void filled with late calcite cement these three crystal populations represent two distinct dolomites and their alteration product the smallest of the silt size crystals which are rarely preserved are also the cores of the larger crystals upon which grew an inner and outer cortex of somewhat different composition the 18o values of dolomite rhombs 1 6 to 2 9 correlate positively with 13c values 0 7 to 3 0 with the lowest values from silt size or small sand size crystals and the highest values from large sand size crystals with leached unfilled cores low and variable 18o and 13c values in conjunction with high and variable mn and fe contents in both the core and inner cortex of all crystals are consistent with formation from a mixture of brackish water and seawater higher values for the outer cortex in sand size crystals are typical of those expected for precipitation from normal or near normal seawater low sr mn and fe contents in the largest crystals in conjunction with fluid inclusions of seawater salinity in the outer cortex are also consistent with the bulk of the large crystals having precipitated from seawater using the sr isotope evolution curve for cenozoic seawater sr isotope ratios of the dolomites can be divided into four distinct groups which correspond to times of major transgressions this cenozoic example in which dolomite petrography and crystal chemistry can be explained in terms of simple transgression regression offers a simple sedimentological explanation for many similar dolomites where processes of formation cannot be so easily constrained

permafrost tectonics and past and future regional climate change yukon and adjacent northwest territories late tertiary changes in the general circulation of the atmosphere regionally enhanced by uplift of the wrangell saint elias and coast mountains were sufficient to promote permafrost development in the western arctic permafrost developed in yukon territory and adjacent northwest territories during early pleistocene glacial periods after continued tectonic activity led to further modification of regional climate but degraded in the interglacials permafrost has been present in northern parts of the region since the illinoian glaciation but most ground ice in central yukon formed in the late wisconsinan the present interglacial is the only one with widespread evidence of permafrost which is maintained in the valleys of central and southern yukon by the saint elias mountains blocking continental penetration of maritime air from the gulf of alaska this reduces snow depth in winter while cold air drainage in the dissected terrain of the yukon plateaus enhances the near surface inversion leading t

coupling patterns between para glacial and permafrost degradation responses in antarctica the recently deglaciated environments in maritime permafrost regions are usually affected by very active paraglacial processes elephant point is an ice free area of 1 16 km2 located in the sw of livingston island south shetland islands antarctica between 1956 2010 the retreat of the ice cap covering most part of this island has exposed 17 3 of the land surface in this peninsula two geomorphological units were identified in this new ice free area a moraine extending from the western to the eastern coastlines and a relatively flat proglacial surface the glacier in 1956 sat in contact with the northern slope of the moraine but its accelerated retreat in parallel to the warming trend recorded in the antarctic peninsula left these areas free of glacier ice subsequently the postglacial evolution was controlled by the relaxation phase typical of paraglacial systems the typology and intensity of geomorphological processes show a significantly different dynamics between the southern and northern slopes of the moraine this pattern is related to the different stage of paraglacial adjustment in both slopes in the southern side on coarser sediments pronival ramparts debris flows and alluvial fans are distributed with a low to moderate activity of slope processes in the northern side mass wasting processes are extremely active on fine grained unconsolidated sediments ice rich permafrost is being degraded by thermokarst processes landslides and mudflows transfer large amounts of sediments down slope the surface affected by retrogressive thaw slumps in the moraine has been quantified in 24 172 m2 which accounts for 9 6 of its surface the abundance of kettle lakes is also indicative of the degradation of the ground ice paraglacial processes are expected to continue in the moraine and proglacial area in the near future although their intensity and duration will depend on the magnitude and rate of future climate trends in the northern antarctic peninsula copyright 2015 john wiley sons ltd

the thermal conductivity for granite with various water contents the thermal conductivities of granite were measured under different conditions of porosity and water content to investigate the effects of the porosity and water content on the thermal conductivity for the dry samples the thermal conductivities range from 2 12 w mk for the rocks with a high porosity to 3 12 w mk for the ones with a low porosity water sorbed samples have greater thermal conductivities than dry samples of the same granite the thermal conductivities range from 2 99 w mk for granites with a high porosity to 3 62 w mk for ones with a low porosity under saturated condition

thermal conductivity of soils and rocks from the melbourne australia region the thermal conductivity of soils and rocks is an important property for the design of thermally active ground structures such as geothermal energy foundations and borehole heat exchange systems this paper presents the results of a laboratory study of the thermal conductivity of soils and rocks from around melbourne australia the thermal conductivity of six soils and three rock types was experimentally measured using both a thermal needle probe and a divided bar apparatus soil samples were tested at a wide range of moisture contents and densities the results demonstrated that the thermal conductivity varied with soil moisture content density mineralogical composition and particle size coarse grained soils were observed to have a larger thermal conductivity than fine grained soils in addition the thermal conductivity of soils increased with an increase in dry density and moisture content siltstone sandstone and basalt rock samples were tested dry and water saturated they demonstrated an increase in thermal conductivity with an increase in density when dry however when water saturated siltstone and sandstone showed no significant correlation between density and thermal conductivity whereas a linear increase in thermal conductivity with density was observed for the saturated basalt samples these differences were attributed to both variations in mineralogy and anisotropy of each sample the thermal conductivity data obtained from this study provides an initial database for soils and rocks from the melbourne australia region which can serve for the design of thermo active structures installed locally and in locations with similar ground conditions

creep characteristics and process analyses of a thaw slump in the permafrost region of the qinghai tibet plateau china abstract a thaw slump in the permafrost region of the qinghai tibet plateau was monitored to investigate typical characteristics of creep positions and processes in combination with soil property analyses the results show that the thaw settlement exhibits a contraction effect in the horizontal direction because of uneven thaw settlement slope displacement of creep occurs only in the top 50 cm of the soil the gravimetric water content soil porosity and soil temperature are higher near the thaw slump in thaw seasons compared with the undisturbed soil however the shear strength is lower melting ground ice releases thaw water that converges along the slope and forms an overland flow at the front part of the gentle slope area and a ponding depression at the slope bottom the analyses of slope stability using the infinite slope model shows that the headwall of the slope is inevitably unstable and slides under saturated conditions whereas the gentle slope area and slope bottom with slight creep displacement are relatively stable the small retrogressive thaw slump is in an early development stage with increasing degree of thaw settlement and rate of erosion the headwall will become steeper and a thermokarst lake will form at the slope bottom

distribution and growth of thaw slumps in the richardson mountains peel plateau region northwestern canada abstract retrogressive thaw slumps are one of the most active geomorphic features in permafrost terrain this study investigated the distribution and growth of thaw slumps in the richardson mountains and peel plateau region northwestern canada using tasseled cap tc trend analysis of a landsat image stack based on the tc linear trend image more than 212 thaw slumps were identified in the study area of which 189 have been active since at least 1985 the surface area of the slumps ranges from 0 4 to 52 ha with 10 slumps exceeding 20 ha the thaw slumps in the region are all situated within the maximum westward extent of the laurentide ice sheet based on relations between frequency distribution of slumps and that of terrain factors in the landscape the slumps are more likely to occur on the ice rich hummocky rolling moraines at elevations of 300 350 m and 450 500 m and along east facing slopes slope aspects of 15 to 180 with gradients of 8 to 12 pixel level trend analysis of the tc greenness transformation in the landsat stack allowed calculating headwall retreat rates for 19 thaw slumps the 20 year average retreat rates 1990 2010 period for 19 slumps ranged from 7 2 to 26 7 m yr 1 with the largest slumps having higher retreat rates at the regional scale the 20 yr headwall retreat rates are mainly related to slope aspect with south and west facing slopes exhibiting higher retreat rates and large slumps appear to be generating feedbacks that allow them to maintain growth rates well above those of smaller slumps overall the findings presented in this study allow highlighting of key sensitive landscapes and ecosystems that may be impacted by the presence and growth of thaw slumps in one of the most rapidly warming region in the arctic

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

measuring the sediment thickness in urban areas using revised h v spectral ratio method abstract for the sake of safety it is crucial for civil engineers to determine the thickness of the sediment layers in the urban areas however the noisy detection environment in a city presents a significant challenge to the traditional artificial source geophysical methods which are used to estimate and monitor of sediment thickness given this otherwise challenging detection environment the h v spectral ratio method provides an effective and cheap means of detecting sediment thickness it exploits microtremor signals to obtain the resonant frequency of the surface layer which is then used to determine site sediment thickness with an empirical equation using the data from a single observation station in this study we collected microtremor data at 109 locations in the aoshan bay area of the shandong peninsula and determined the resonant frequency and analysed the morphological features of the h v spectral ratio curves in order to calibrate the frequency bedrock depth equation accurately to the local conditions vs profile estimation is used to fine tune the frequency bedrock depth equation by comparing the s wave velocity structure obtained using the microtremor spac method with that found from borehole samples we were able to verify the reliability and accuracy of application of the microtremor spac method by using the h v spectral ratio method and the modified equation that transforms resonance frequencies to sediment thickness we generated a thickness map of the sedimentary layers in the aoshan bay area of the shandong peninsula the map provides useful information for ensuring the safe construction of the city s infrastructure we conclude that the use of microtremor signals can provide important geological information as a cheaper and quick way for the construction and development of urban infrastructure

seasonal patterns of coupled flow in the active layer at three sites in northwest north america vertical arrays of temperature and electric potential probes were installed in the upper soil at sites along the mackenzie river valley and on the north slope of alaska time series were obtained at subdiurnal frequencies throughout the year in the active layer and upper permafrost if the data acquisition system is properly configured the time series can be used to infer soil physiochemical processes the electric potential develops primarily in response to soil water solute concentration gradients in the soil column and is a crude surrogate of the soil water electrolytic conductivity summer precipitation can cause rapid penetration of the thaw front when percolating rainwater warmed at the ground surface carries sensible heat downward to the thawing front rates of warming at depth occur significantly faster than those typical of conductive heat transfer in early winter as the freezing front penetrates downward toward the permafrost table ions are excluded from the ice and concentrated in the intermediate unfrozen zone nearly instantaneous warming of the active layer is triggered by spring snowmelt at happy valley in northern alaska temperatures at the 29 cm depth rise from 7 to 3 c in 1 h for several hours during this event the temperature at 29 cm is warmer than that at regions both above and below producing a strong thermal inversion time series of electric potential or a surrogate derived from electric potential suggest rapid transport of meltwater from the snowpack to depth probably through soil cracks serial events hasten active layer warming by 1 2 weeks

using neural networks to predict thermal conductivity from geophysical well logs summary we present a new approach based on neural networks to predict the thermal conductivity of sedimentary rocks from a set of geophysical well logs this method is calibrated on ocean drilling program odp data which provide several thousands of conductivity measurements combined with five geophysical well logs sonic density neutron porosity resistivity and gamma ray this data set is used to train multilayer perceptrons mlp and to find an empirical relationship between well logs mlp inputs and thermal conductivity mlp output validation tests suggest that mlp provide better estimates of thermal conductivity within 15 per cent confidence level than classical linear models and still give satisfying results with sets of only four well logs if neutron porosity is included in two odp sites 863b and 1109d mlp s predictions are compared to conventional mixing methods although this latter technique gives reliable results provided that rocks description is precise enough the mlp is more straightforward does not need any extra parameter and makes predictions in good agreement with the experimental trends this method will be useful in the estimation of heat flow from data acquired in scientific and industrial boreholes

fifty years of coastal erosion and retrogressive thaw slump activity on herschel island southern beaufort sea yukon territory canada abstract patterns of coastal erosion in the arctic differ dramatically from those coasts in more temperate environments thick sea ice and shore fast ice limit wave based erosional processes to a brief open water season however despite this permafrost coasts containing massive ice ice wedges and ice bonded sediments tend to experience high rates of erosion these high rates of erosion reflect the combined thermal mechanical processes of thawing permafrost melting ground ice and wave action climate change in the arctic is expected to result in increased rates of coastal erosion due to warming permafrost increasing active layer depths and thermokarst rising sea levels reduction in sea ice extent and duration and increasing storm impacts with the most ice rich permafrost in the canadian arctic the southern beaufort sea coast between the tuktoyaktuk peninsula and the alaskan border is subject to high rates of erosion and retrogressive thaw slump activity under many climate change scenarios this area is also predicted to experience the greatest warming in the canadian arctic this paper presents results of a remote sensing study on the long term patterns of coastal erosion and retrogressive thaw slump activity for herschel island in the northern yukon territory using orthorectified airphotos from 1952 and 1970 and an ikonos image from 2000 corrected with control points collected by kinematic differential global positioning system and processed using softcopy photogrammetric tools mean coastal retreat rates of 0 61 m yr and 0 45 m yr were calculated for the periods 1952 1970 and 1970 2000 respectively the highest coastal retreat rates are on north west facing shorelines which correspond to the main direction of storm related wave attack during the period 1970 2000 coastal retreat rates for south to south east facing shorelines displayed a distinct increase even though these are the most sheltered orientations however south to south east facing shorelines correspond to the orientations where the highest densities of retrogressive thaw slumps are observed differences in rates of headwall retreat of retrogressive thaw slumps and coastal erosion results in the formation of larger thermokarst scars and the development of polycyclic thaw slumps on south to south east exposures the number and the total area of retrogressive thaw slumps increased by 125 and 160 respectively between 1952 and 2000 as well the proportion of active retrogressive thaw slumps increased dramatically polycyclic retrogressive thaw slumps appear to develop in a periodic fashion related to retrogressive thaw slump stage and maximum inland extent

thermokarst lakes and ponds on mars in the very recent late amazonian past the history of water is fundamental to understanding the geological evolution of mars and to questions concerning the possible development of life on the red planet today mars is cold and dry it

thermal conductivity of unconsolidated sediments with geophysical applications a theoretical model for the prediction of the thermal conductivity of unconsolidated granular sediments with application to sand shale mixtures is presented the sediment is modeled as an assemblage of grains of thermal conductivity s immersed in a pore fluid of thermal conductivity in order to take into account for the thermal interactions between the grains a differential effective medium approach is used to provide a relationship between the effective thermal conductivity of the isotropic mixtures of grains saturated by the pore fluid the porosity and the thermal conductivities of the grains and pore fluid the influence of the topology of the interconnected pore space is accounted for through the use of the electrical cementation exponent m which is related to the electrical formation factor f by f m where is the interconnected porosity the main assumption of the model lies in the small contiguity between the grains this assumption holds well for unconsolidated sand shale mixture sediments as demonstrated by comparing the model to available experimental data the model offers the possibility to derive thermal conductivity profiles from downholes measurements of natural radioactivity electrical resistivity and bulk density

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

patterns of burial and tectonically controlled dolomitization in an upper devonian fringing reef complex leduc formation peace river arch area alberta canada abstract cumulative patterns of dolomitization in a subsurface upper devonian carbonate platform in the peace river arch area alberta are related to progressive burial 1 km fracturing focused basin derived fluids along subvertical structural conduits and into adjacent permeable strata in the early mississippian 3 wt fe dolomite in the platform heralding increased fe mobilization during burial diagenesis a negative shift in 18o values 6 5 to 15 is associated with successive fracture related dolomites and is interpreted to reflect an increase in fluid temperatures fracture related flow was probably rapid petrographic and isotopic signatures of fracture related dolomitization can be traced 300 m upsection from the leduc formation

headwall retreat of ground ice slumps banks island northwest territories the relationship between ice face ablation and headwall retreat is described for three ground ice slumps in the sand hills moraine southwest banks island retreat exceeds ablation by a geometric factor that depends on the slope of the ice and the gradient of the surrounding terrain amounts of retreat predicted from ice ablation calculations compare favourably with field measurements except at the start of thermokarst activity in the spring or when the ground ice remains covered by debris for long periods long term headwall retreat for slumps in southern banks island with different orientations and ice contents can be estimated using a model based on meteorological information the model predicts headwall recession of 11 m a for a ground ice slump facing south and 8 8 9 3 m a for one facing north with inputs of a 35 ice face a ground slope of 5 and a volumetric latent heat of 270 mj m3 these predictions are close to the maximum rates of retreat over a 10 year period as measured from air photographs

host rock dolomitization and secondary porosity development in the upper devonian cairn formation of the fairholme carbonate complex south west alberta canadian rockies diagenesis and geochemical modelling the upper devonian carbonate reefs in west central alberta are important petroleum reservoirs that are well known for their extensive secondary porosity an outcrop analogue study indicates that an early matrix selective dolomitization event occurred which is characterized by a major late devonian sea water component with increased salinity because of evaporation it is interpreted that the matrix replacive dolomite formed during the famennian as the result of a combination of both seepage and latent reflux dolomitization although an additional type or overprinting of later immediate burial dolomitization cannot be excluded formation of the moulds is attributed mainly to the dissolution of undolomitized fossil cores most typically stromatoporoids geochemical modelling indicates that carboxylic acid fluids have the highest potential for dissolving residual calcite in this case geochemical models consistent with this analysis and interpretations can reproduce the secondary porosite and suggest a viable dolomitization process for the localities studied

stratigraphic isotopic and mineralogical evidence for an early holocene thaw unconformity at mayo yukon territory ice rich glaciolacustrine sediments near mayo yukon territory reveal a thaw unconformity in the form of truncated ice wedges and abrupt changes in cryotexture the unconformity has been radiocarbon dated at 8870 200 years bp which is within the holocene period of optimal climatic conditions in northern yukon and the mackenzie delta area reported by other workers analysis of the mineralogy of the sediments indicates that the material above the unconformity is enriched in minerals that are the products of a more intense weathering environment than those deeper in the profile oxygen isotope ratios of ground ice in the sediments suggest the presence of two genetically distinct ice units above and below the unconformity an average rate of upward permafrost growth in this area of 0 1 0 2 mm year 1 is calculated for the period since the climatic optimum

terrain controls on the occurrence of coastal retrogressive thaw slumps along the yukon coast canada retrogressive thaw slumps rtss are among the most active landforms in the arctic their number has increased significantly over the past decades while processes initiating discrete rtss are well identified the major terrain controls on the development of coastal rtss at a regional scale are not yet defined our research reveals the main geomorphic factors that determine the development of rtss along a 238 km segment of the yukon coast canada we 1 show the current extent of rtss 2 ascertain the factors controlling their activity and initiation and 3 explain the spatial differences in the density and areal coverage of rtss we mapped and classified 287 rtss using high resolution satellite images acquired in 2011 we highlighted the main terrain controls over their development using univariate regression trees model coastal geomorphology influenced both the activity and initiation of rtss active rtss and rtss initiated after 1972 occurred primarily on terrains with slope angles greater than 3 9 and 5 9 respectively the density and areal coverage of rtss were constrained by the volume and thickness of massive ice bodies differences in rates of coastal change along the coast did not affect the model we infer that rates of coastal change averaged over a 39 year period are unable to reflect the complex relationship between rtss and coastline dynamics we emphasize the need for large scale studies of rtss to evaluate their impact on the ecosystem and to measure their contribution to the global carbon budget

geochemical constraints on the origin of the kicking horse and monarch mississippi valley type lead zinc ore deposits southeast british columbia canada two mississippi valley type mvt ore deposits kicking horse and monarch have been studied with the aim of comparing the ores at the two localities and to characterize the origin of the mineralizing fluids and the ore formation process es both deposits are hosted by the middle cambrian cathedral formation carbonate host rocks kicking horse on the north and monarch on the south flank of the kicking horse valley near field se british columbia the ore bodies are situated at the transition of western basinal to eastern shallow water strata of the paleo pacific passive margin succession in the cordilleran foreland province of the western canada sedimentary basin both deposits are related spatially to normal faults in both localities the ore minerals are dominated by pyrite sphalerite and galena dolomite minor quartz and calcite are also present in close association with the ores the salinity 21 30 wt nacl eq and homogenization temperatures 63 182 c measured in fluid inclusions in carbonate quartz and sphalerite lie within the typical range of mvt fluid conditions the good stoichiometry 50 53 mol caco3 low 18o values 21 to 14 vienna peedee belemnite and relatively high homogenization temperatures 95 c of the dolomite suggest the dolomites were formed under burial diagenesis the ore forming fluids probably interacted with siliciclastic units based on elevated li contents and 87sr 86sr ratios which are highest in the dolomite type after the main ore stage we propose that the ores formed from the mixing of a downward infiltrating sulfur bearing halite dissolution fluid with an upward migrating metal rich evaporated seawater fluid which had already undergone minor mixing with a dilute fluid

influence of groundwater flow on the estimation of subsurface thermal parameters we investigated the influence of groundwater flow on the thermal tests performed in borehole heat exchangers to infer the underground thermal properties temperature time signals were simulated with a moving line source mls model under different hypotheses of darcy velocity periodic and random noise was included in the synthetic data obtained with this model in order to mimic high frequency disturbances caused by several possible sources e g equipment instability and changes in environmental conditions during the experiment that often occur in real signals the subsurface thermal conductivity the darcy velocity and the borehole thermal resistance were inferred by minimising the root mean square error between the synthetic dataset and the model the calculated thermal and hydraulic parameters were consistent with the a priori values the optimisation procedure results were then tested with the infinite line source ils model for a darcy velocity exceeding 10 7 m s 1 ils largely overestimates thermal conductivity the approach relying on the mls model was finally tested with real temperature time data and produced reliable estimates of thermal conductivity darcy velocity and borehole thermal resistance the inferred groundwater flow was cross checked by means of an independent method based on the analysis of temperature depth logs recorded under thermal equilibrium conditions such a test validates the darcy velocity inferred with the mls approach

lateral heterogeneities and microtremors limitations of hvsr and spac based studies for site response abstract we report a site effect study carried out in a small alluvial valley nari basin in ulleung island republic of korea in that small valley a permanent broad band array of five stations records ground motion continuously in addition we performed microtremor measurements using two arrays of stations a small aperture array 60 m and a medium aperture one 500 m ambient vibration was also recorded at 38 points inside the basin the records were analyzed using horizontal to vertical spectral ratios hvsr to estimate dominant frequency and maximum amplification and the spatial autocorrelation spac method to estimate the subsoil structure via phase velocity dispersion curves nari basin is clearly a 3d structure but it was expected that a laterally irregular model might be built from the interpolation of several 1d models dominant frequency maps based on results from hvsr suggest a simple sedimentary structure with mostly smooth lateral variations in contrast maximum amplification distribution is very irregular and shows no correlation with dominant frequency in the case of nari it seems that the complexity of the basin structure cancels the usefulness of hvsr we could estimate a phase velocity dispersion curve for 81 of the station pairs recording simultaneously ambient vibration in our arrays in all the cases the resulting dispersion curve had a simple shape suggesting that the subsoil structure consists of a single layer over a half space however the dispersion curves are incompatible among them even for different station pairs covering the same path something impossible if the subsoil structure were 1d it seems that the passive methods we have used in nari basin are not adapted to its structure this makes a tomography unfeasible and we are unable to propose a subsoil structure for nari basin our results show that surface wave dispersion may be estimated using the spac method even when the medium is far from 1d we believe that this problem is enhanced by the small size of this basin which amplifies the effect of lateral heterogeneities

on the nature and origin of muck deposits in the klondike area yukon territory organic rich muck deposits which blanket auriferous gravels in the klondike area yukon territory comprise two principal stratigraphic units i a silty late pleistocene deposit and ii holocene organics lying unconformably on the silt the deposits are found predominantly in valley bottoms and if undisturbed are normally perennially frozen field and laboratory investigations of particle size mineralogy and morphology as well as organic matter and sedimentary structures indicate that the silt is both primary massive and redeposited bedded loess by weight 87 medium and coarse silt and fine sand radiocarbon dates indicate that the loess was deposited during late wisconsinan mcconnell glaciation beginning after 27 000 14c years bp the loess was likely derived from the floodplain of the yukon river during periods of low flow turf in growth position and organic matter in the silt similar to that of loessal grasslands near kluane lake suggest a grassland environment for the area during

an empirical relationship between thermal conductivity and elastic wave velocities in sandstone measurements in three samples of very clean quartz sandstone in the porosity range 4 16 under dry and 100 water saturated conditions show that p and s wave velocities are linearly correlated with thermal conductivity the experimental results agree with the theoretical relation between seismic velocities predicted by the kuster and toksoz model 1974 and thermal conductivity predicted by weighted geometric mean

application of the initial model feature of microtremor to investigate a part of the geothermal field of jiangsu region in china application of geothermal resources draws growing attention in recent years as geothermal resources are an emerging clean and renewable energy there are tremendous geothermal resources in jiangsu province which have been considered as significant contributions to regional economic development and climate variation controlled by tectonic structure the spatial distribution of geothermal resources is highly uneven because of the complexity in terms of thermal storage background and reservoir types successful application of geothermal resources is facing many practical difficulties such as determining the drilling location of geothermal well thus successful geothermal exploration is still of high risk firstly geothermal resources of jiangsu province can be categorized into four areas thus geothermal reservoirs of different areas are discussed in this paper according to the results of rock samples testing and analyzing a geothermal reservoir physical model of southern jiangsu geothermal resource area has been established which can provide an initial restriction for microtremor inversion two survey points with major inversion error under blind inversion are recalculated as well the results show that the initial inversion model can effectively improve the accuracy of inversion and thus benefit the sounding reservoirs by introducing the actual initial inversion model microtremor survey method can achieve more accurate results to provide critical information for the development of geothermal resources which reduce the risk of successful geothermal drilling

distribution of carbon and nitrogen along hillslopes in three valleys on herschel island yukon territory canada abstract thermokarst results from the thawing of ice rich permafrost and alters the biogeochemical cycling in the arctic by reworking soil material and redistributing soil organic carbon soc and total nitrogen tn along uplands hillslopes and lowlands understanding the impact of this redistribution is key to better estimating the storage of soc in permafrost terrains however there are insufficient studies quantifying long term impacts of thaw processes on the distribution of soc and tn along hillslopes we address this issue by providing estimates of soc and tn stocks along the hillslopes of three valleys located on herschel island yukon canada and by discussing the impact of hillslope thermokarst on the variability of soc and tn stocks we found that the average soc and tn 0 100 cm stocks in the valleys were 26 4 8 9 kg c m 2 and 2 1 0 6 kg n m 2 we highlight the strong variability in the soils physical and geochemical properties within hillslope positions high soc stocks were found at the summits essentially due to burial of organic matter by cryoturbation and at the toeslopes due to impeded drainage which favored peat formation and soc accumulation the average carbon to nitrogen ratio in the valleys was 12 9 ranging from 9 7 to 18 9 and was significantly higher at the summits compared to the backslopes and footslopes p

relations between air and surface temperature in discontinuous permafrost terrain near mayo yukon territory the association of site characteristics with the n factor a ratio of air to ground surface temperature was investigated at five sites in the boreal forest near mayo yukon territory permafrost was in equilibrium with surface conditions at three sites was degrading at another and was absent from the fifth air and near surface ground temperatures were recorded by data loggers between september 2000 and april 2002 and mean daily temperatures were accumulated to calculate n factors for the freezing nf and thawing nt seasons air temperature did not vary between the sites so inter site differences in nf and nt were because of variations in surface temperature variations in nf between the sites over the two winters were primarily because of differences in snow depth but at sites with similar snow cover the surface temperatures were relatively high when the site was underlain by unfrozen ground during summer daily mean surface temperatures were initially less than air temperatures however once

the thermal regime of a retrogressive thaw slump near mayo yukon territory the development of a retrogressive thaw slump near mayo yukon territory has been traced from initiation by bank erosion 1949 of the stewart river to stabilization in 1993 1994 the stabilized headwall of the slump is 450 m from the river and the slope of the slump floor is 3 a transect of the slump from the river to the stabilized headwall was drilled in july 1995 to determine the extent and rate of permafrost degradation in the slump floor thermistors were placed in access tubes to 12 m depth at five sites four near the transect and one in undisturbed terrain to determine the magnitude of thermal disturbance due to slump development data loggers at the sites recorded the ground temperature at 1 m depth for two years from august 1995 the annual mean ground temperatures measured by the data loggers varied between 1 2 and 1 8 c in the slump compared with 2 4 c in undisturbed ground indicating a disturbance of about 4 c due to slumping the depth of thaw in the slump floor is consistent wit

inverse estimation of rock thermal conductivity based on numerical microscale modeling from sandstone thin sections abstract the effective thermal conductivity etc of porous rocks is primarily controlled by the matrix thermal conductivity mtc and the thermal conductivity of the pore fluid as a function of porosity rock etc has been investigated widely however information on mtc is rather sparse this study proposes a new approach using a numerical model to determine the mtc of porous rocks by parameter fitting to the measured etc the model represents realistic rock textures as detailed information on grain and pore geometries was obtained from microscopic images of thin sections mtc fitted from water saturated condition water as pore fluid showed plausible values between 4 9 and 7 6 w m k while mtc values from dry condition air as pore fluid were disproportionate except for one model with consistent mtc for both conditions this supports the idea that at constant temperature and pressure mtc is an intrinsic property independent of fluid saturation for this reason mtc from water saturated condition was used to calculate dry etc the model showed lower dry etc than the lab measurements but within a reasonable range for dry sandstones investigation of etc regarding saturation degree revealed that the samples may contain 12 45 residual moisture which explained the higher measured dry etc additionally the models allowed observation of textural influences showing that grain size distribution and connectivity affected the heat conduction of porous rocks

thermal conductivity characterisation of shallow ground via correlations with geophysical parameters abstract thermal conductivity is an important physical property of geological formations for example a comprehensive assessment of the thermal conductivity variations in the shallow ground surrounding a heat exchanger borehole can be used to determine the installation parameters of a ground source heat pump however in some locations it is not possible to measure thermal conductivity directly one of the most common methods to indirectly infer thermal conductivity is to establish correlations between thermal conductivity and various geophysical parameters by utilising test data acquired from drilling sites and ascertaining the corresponding geophysical parameters via non invasive geophysical methods such correlations can be obtained at 11 test sites the thermal conductivities were measured in situ via thermal response testing and the corresponding values for the s wave velocity and density were calculated using the microtremor survey method msm the correlations between the thermal conductivity s wave velocity and density in the tested shallow ground were built by exponential fitting by utilising the established correlations two dimensional 2d cross sections along the microtremor survey line were created to illustrate the thermal conductivity variations in the shallow ground these results demonstrate that this approach can be used to infer the thermal conductivities of areas that cannot be tested directly

simulating the decadal to millennial scale dynamics of morphology and sequestered carbon mobilization of two thermokarst lakes in nw alaska 1 thermokarst lakes alter landscape topography and hydrology in widespread permafrost regions and mobilize significant permafrost carbon pools including releasing methane ch4 to the atmosphere despite this the dynamics of lake evolution permafrost thawing and carbon mobilization are not well known we present a 3 d numerical model of thermokarst lakes on organic rich yedoma permafrost terrains with surface water flow and pooling naturally defining lakes that deepen expand laterally and drain due to talik formation bank retreat and both gradual and catastrophic drainage we predict the 3 d pattern of microbial methane production within the talik over time as a first model test and calibration beginning with small protolakes we simulated 10 000 years of evolution of pear and claudi lakes two neighboring thermokarst features on the northern seward peninsula alaska simulated lakes approximated observed bathymetry but results are sensitive to initial topography and soil ice content local topography caused markedly different dynamics for the two lakes pear expanded rapidly across low relief topography fully drained multiple times and released little methane in later stages due to pleistocene carbon depletion by the first and largest lake generation claudi grew slowly and continuously across high relief topography forming high subaerial banks partial drainages left remnant horseshoe lakes that continued to expand into virgin yedoma mobilizing carbon at roughly the same rate irrespective of lake drainage the 2 discrepancy between simulated ch4 production and observed emission rates in claudi likely results from misestimation of hot spot ebullition labile carbon content ch4 co2 production ratio or microbial ch4 oxidation