field scale water transport in unsaturated crystalline rock safe disposal of toxic wastes in geologic formations requires minimal water and gas movement in the vicinity of storage areas ventilation of repository tunnels or caverns built in solid rock can desaturate the near field up to a distance of meters from the rock surface even when the surrounding geological formation is saturated and under hydrostatic pressures a tunnel segment at the grimsel test site located in the aare granite of the bernese alps central switzerland has been subjected to a resaturation and subsequently to a controlled desaturation using thermocouple psychrometers tp and time domain reflectometry tdr the water potentials psi and water contents theta were measured within the unsaturated granodiorite matrix near the tunnel wall at depths between 0 and 160 cm during the resaturation the water potentials in the first 30 cm from the rock surface changed within weeks from values of less than 1 5 mpa to near saturation they returned to the negative initial values during desaturation the dynamics of this saturation desaturation regime could be monitored very sensitively using the thermocouple psychrometers the tdr measurements indicated that water contents changed dose to the surface but at deeper installation depths the observed changes were within the experimental noise the field measured data of the desaturation cycle were used to test the predictive capabilities of the hydraulic parameter functions that were derived from the water retention characteristics psi theta determined in the laboratory a depth invariant saturated hydraulic conductivity k s 3 0 x 10 11 m s 1 was estimated from the psi t data at all measurement depths using the one dimensional unsaturated water flow and transport model hydrus vogel er al 1996 for individual measurement depths the estimated k s varied between 9 8 x 10 12 and 6 1 x 10 11 the fitted k s values fell within the range of previously estimated k s for this location and led to a satisfactory description of the data even though the model did not include transport of water vapor

on the connected porosity of mineral aggregates in crystalline rocks the 14 c pmma impregnation of rock samples and mineral staining methods provide the connected porosity map and the spatial distribution of mineral aggregates respectively combined image analysis of mineral and porosity maps allows quantification of the connected porosity distribution in rock forming mineral aggregates after the two maps have been superimposed numerically the 14 c pmma method provides an indication of the extent of pore connectivity for each pixel in the analyzed area which can be used to obtain the porosity distribution as a function of modal mineralogy when applied to undeformed and deformed kivetty granodiorite samples from finland the method allows for a detailed analysis of the rock porosity porosity distributions related to the undeformed rock are unimodal and approximately identical to each other on the other hand porosity distributions of the deformed granodiorite are multimodal and vary significantly constituent porosity sets of the deformed samples were albite crystals free of alkali feldspar patches and alkali feldspar phenocrysts average porosity 0 21 albite containing alkali feldspar patches 0 59 rapakivi albitic mantles 1 15 quartz 0 39 and mafic minerals 5 8 moreover the analysis indicates that the numerous micropores observed under sem within alkali feldspar phenocrysts and albite crystals free of alkali feldspar patches are unconnected in 3d

late quaternary history of the mackenzie beaufort region arctic canada from modelling of permafrost temperatures 2 the mackenzie delta tuktoyaktuk coastlands in the mackenzie beaufort region maximum permafrost thickness is 750 m in the pleistocene tuktoyaktuk coastlands less than 100 m in the holocene mackenzie delta and 500 m and anomalously warm in the big lake delta plain between the two areas numerical modelling has been used to derive surface temperature histories that fit ground temperatures and permafrost conditions at 12 wells in the unipkat kumak and taglu hydrocarbon fields the models indicate that the present holocene mackenzie delta was built by fluvial processes into a submarine trough the delta front passed a site presently some 20 km from the coast about 4 5 ka and subsequently 58 m of ice bonded permafrost has aggraded in contrast the big lake delta plain was a subaerial platform for much of the wisconsinan it experienced several thousand years of inundation in the holocene probably due to widespread development of thermokarst lakes at sites 8 12 km from the coast the present subaerial conditions were established 0 5 1 5 ka throu

late wisconsinan holocene paleogeography of delaware bay a large coastal plain estuary abstract analyses of an extensive grid of seismic reflection profiles along with previously published core data and modern sedimentary environment information from surrounding coastal areas permit an outline of the paleogeography of the large delaware bay estuary during the last transgression of sea level during late wisconsinan times the delaware river system eroded a dendritic drainage pattern into the gravelly and muddy sands of tertiary and younger age beneath the southern half of the lower bay area this system included the trunk valley of the ancestral river and a large tributary valley formed by the convergence of secondary streams along the delaware coast the evolution of the estuary from this drainage system proceeded as follows 1 when local relative sea level was at 50 m the head of the tide reached the present bay mouth area 2 at 40 m possibly 15 000 12 000 yrs ago the trunk valley of the drainage system was a tidal river that extended more than 30 km up the bay and a small contiguous inlet existed at the bay mouth 3 at 30 m approximately 11 000 10 000 yrs ago the estuary comprised two narrow passages formed by the drowning of the main and tributary river valleys and the bay mouth inlet was 5 6 km wide 4 at 20 m between 8000 and 7000 yrs ago the two passages of the estuary were joined except for a series of small islands on top of a low intervening ridge and the inlet channel was 11 km wide 5 at 10 m between 6000 and 5000 yrs ago the estuary was nearly continuous and encompassed about 60 of the present lower bay area thin coarse grained fluvial deposits accumulated initially within the main channels of the former drainage system as base level was elevated by rising sea level during the subsequent development of the estuary clayey silts were deposited rapidly beneath the nontidal estuarine depocenter turbidity maximum as it migrated through the bay area and organic muds accumulated in tidal wetlands that occupied the mouths of tributaries and small marginal embayments as the fetch and tidal prism of the estuary increased narrow barrier and headland beaches composed of fine to coarse sands were formed locally along the bay shorelines in the later stages of development sediment scour reworking and transport became the dominant processes within the open estuary data from this study demonstrate the great temporal and spatial variability of sedimentary deposits within large drowned river valley estuaries and outline a model that can be used to interpret ancient estuarine strata

multi risk interpretation of natural hazards for settlements of the hatay province in the east mediterranean region turkey using srtm dem many scientists have recently alarmed natural hazards due to global climate change such natural disasters are coastal inundation in response to sea level rise and or river flooding caused by heavy rain falls additionally earthquakes and etc in terms of natural hazards one of the most sensitive and culturally significant areas in turkey is the hatay province in the east mediterranean region the hatay province is located on such a region which is not only vulnerable to coastal inundation and river flooding but also is a tectonically and seismically sensitive area in this study for taking conservation measures against the natural hazards beforehand and decision making on any future land planning a digital terrain model and a 3d fly through model of the hatay province were generated then quantitatively and or qualitatively interpreted by employing the shuttle radar topographic mission digital elevation model besides stream drainage patterns lineaments and structural geological features were extracted for natural hazard risk interpretation of settlements and their relationships among the landscape characteristics were exhibited by combining tectonic information previously confirmed regarding the sea level rise the coastal inundation risk map indicates that the most vulnerable areas are coastlines of iskenderun arsuz payas and samandag respectively by after analyzing the digital terrain of the study region and stream drainage patterns the karasu valley zone where the amik plain settlements of antakya iskenderun arsuz payas and samandag with their flood plains have the most flooding risk in decreasing order respectively when a heavy raining occurs finally analysis of tectonics has revealed that antakya iskenderun hassa kirikhan samandag payas arsuz altinozu kumlu and hacipasa regions have the most sensitivity to earthquake disaster in the study region

the influence of tortuosity on molecular diffusion in freshwater sediments of high porosity abstract in sediments diffusive transport of ions and molecules is basically influenced by two sediment characteristics tortuosity and porosity for the first time the formation factor f which combines the effect of tortuosity and porosity on diffusion was quantified in freshwater sediments at submillimeter resolution sediment cores were treated with kcl and f was determined using a resistivity sensor and k selective electrodes f was determined in sediments from different water depths of the eutrophic lake zug switzerland in sandy sediments from a shallow site 12 m depth f increased by approximately 50 within a few millimeters below the sediment surface in clayey and silty sediments from the oxic 160 m depth f increased by only 10 just below the sediment surface values of f were correlated with the porosity at each depth we found close correlations of f 1 02 1 81 for clay silt sediments and f 1 04 1 21 for sandy sediments the exponents are considerably smaller in lake zug than found for marine sediments thus diffusive transport seems to be less affected by tortuosity in this freshwater system

fracture networks in frozen ground fractures in frozen ground self organize into networks through interactions between sequentially emplaced fractures tensile stress and the developing fracture pattern from this viewpoint we model the development of networks on a lattice representing the ground surface on which fractures initiate propagate and arrest under a combination of uniform thermally induced tensile stress stress reduction near existing fractures and stochastic parameterization of heterogeneity in frozen ground and in insulating snow tensile stress from cooling tensile strength propagation threshold fracture depth and elastic properties are chosen to approximate properties of frozen ground using these parameters model networks assemble with properties similar to natural ice wedge networks including 1 individual fracture paths have lengths ranging from tens to hundreds of meters 2 fractures intersect to enclose regions with characteristic spacing between fractures of approximately 22 m 3 intersections between fractures are predominantly orthogonal with less common three way approximately equiangular intersections joint distributions of relative orientation and spacing between fractures from modeled networks and ice wedge networks at espenberg alaska are comparable at the level of variability in natural examples this similarity is consistent with the hypotheses that networks self organize by stress interactions between sequentially placed fractures in frozen ground and that networks are insensitive to the many details of fracture dynamics omitted from the model spacing between fractures in modeled networks is influenced by sub optimal placement of fractures during network development and increases nonlinearly with the length scale of stress reduction around a fracture three way approximately equiangular intersections form where modeled fractures arrest on the outside of bends in earlier fractures

the direction of ice wedge cracking in permafrost downward or upward field studies have been carried out along the western arctic coast of canada in an attempt to determine whether all ice wedge cracks originate at the ground surface and therefore propagate downward or whether some cracks originate near the top of permafrost and then propagate both upward and downward the field studies have been concentrated upon 1 low and high centred tundra polygons a few thousand years old and 2 ice wedges growing for the first time on the bottom of a lake experimentally drained in 1978 the field instrumentation has included electronic crack direction indicators electronic elapsed timers and continuous temperature measurements the field studies reveal that many of the ice wedge cracks originated near the top of permafrost and then propagated upward to the ground surface as well as downward into ice wedge ice for the 1974 1982 period the field observations showed that about 57 of the ice wedges cracked from the ground surface downward and 43 cracked both upward and downw

the first 20 years 1978 1979 to 1998 1999 of ice wedge growth at the illisarvik experimental drained lake site western arctic coast canada in august 1978 a large tundra lake was drained to study the aggradation of permafrost into newly exposed lake bottom sediments ice wedge growth which started in the first winter following drainage had ceased in most of the lake bottom within about twelve years the gradual cessation of thermal contraction cracking can be attributed to rapid vegetation growth snow entrapment an increase in winter ground temperatures and a decrease in the linear coefficient of thermal contraction associated with freeze thaw consolidation of the initially saturated lake bottom sediments the tilt and separation of markers in the active layer revealed gradual convergence towards the troughs even after ice wedge growth had ceased for the first few years the ice wedge growth rate was up to 3 cm a as determined by excavation drilling separation of the bottoms of benchmarks installed into permafrost and divergence of free floating inductance coils placed on the sides of ice wedges well below the bottom of the active la

the diffusive tortuosity of fine grained unlithified sediments abstract use of fick s first law to estimate solute fluxes is arguably the most common and important calculation related to the geochemistry and environmental chemistry of fine grained unlithified sediments in such porous media the diffusion coefficient in this law must be reduced by the square of the tortuosity to account for the longer diffusive paths experimental methods to estimate tortuosity are specialized or time consuming and not routinely done an analysis of available data shows that tortuosity is accurately correlated to readily measured porosity values through the simple relation 2 1 l n 2

largo bank a shoreface connected linear shoal at the bahia blanca estuary entrance argentina abstract the geomorphology and historical evolution of a shoreface connected linear shoal largo bank located offshore from the bahia blanca estuary in argentina is analyzed the bank has a generally elongate shape is 13 km long and varies in width from 0 6 to 2 5 km a series of ebb and flood sinuses channels are located on both sides of the structure bathymetric comparisons indicate that the northern part of the bank is in an erosional stage while depositional and unchanged zones are mixed in the southern area sedimentation rates are as large as 2 7 m yr while sediment removal in the erosion areas may be up to 1 7 m yr a review of historical charts has indicated that the shoal migrated eastward at about 37 m yr if the dynamic conditions are maintained the shoal may affect the depth of the navigation channel of the major deep water harbour system of argentina

late holocene syngenetic ice wedge polygons development bylot island canadian arctic archipelago the initial configuration of the syngenetic ice wedge polygons that developed in the outwash plain of glacier c 79 after 6000 bp was modified by the accumulation of wind blown and organic sediments that began after 3670 110 bp the late holocene sedimentation led to an increase in the thermal contraction coefficient of the soil and the formation of third and fourth order contraction cracks partially explaining the current configuration of the polygonal network the upturning of the sedimentary strata bordering the ice wedges was associated with the summer thermal expansion and resulting internal creep of the soil the mean annual soil displacement coefficient was in the order of 2 5 2 7 10 5 c at the thousand year scale the late holocene sedimentary strata under the centre of the polygons were undisturbed which will make it possible to use this sedimentary record in further studies to attempt paleoenvironmental reconstructions from cores

shoreline changes and morphology of spits along southern karnataka west coast of india a remote sensing and statistics based approach abstract the changes in shoreline positions and morphology of spits along the karnataka coast western india are investigated for the period from 1910 to 2005 using multi dated satellite images and topomaps the study area has been divided into four littoral cells and each cell into a number of transects at uniform intervals the rate of change in shoreline position has been estimated using the statistical linear regression method and cross validated with regression coefficient r 2 and root mean square error rmse methods past and future shoreline positions have been demarcated and future positions of shoreline are estimated for time periods of 10 and 24 years the study reveals that i about 57 of transects exhibit 10 m rmse values indicating better agreement between the estimated and satellite based shoreline positions and ii transects closer to the cell boundaries exhibit about 50 uncertainties in shoreline change rate estimations based on rmse values the influence of natural processes and anthropogenic factors on shoreline changes has been evaluated the cells transects dominated by natural processes reveal low rmse values whereas the cells transects influenced by anthropogenic activities such as sand mining construction of coastal structures exhibit higher rmse values however the variation in rmse values is not significant if the total number of transects is considered significant changes in morphology of spits have been recorded spits demonstrate variations in areal extent i e length and area if 1910 and 1967 are considered separately as base years the present study demonstrates that combined use of satellite imagery and statistical techniques such as linear regression and rmses can be very useful in quantifying shoreline changes and spit morphology

integration of hydrological factors and demarcation of groundwater prospect zones insights from remote sensing and gis techniques the study demonstrates the potential of geographical information system and statistical based approaches to identify the hydrological processes and demarcate the groundwater prospect zones of the gangolli basin karnataka state india the basin is situated in humid tropical climate and influenced by three major rivers viz kollur 6th order stream chakra 6th order stream and haladi 7th order stream which cover an area of 1 512 km2 and cumulative length of 84 km various thematic maps drainage geomorphology geology slope soil lineament and lineament density were prepared using survey of india topographic maps indian remote sensing irs p6 images and other published maps hydrogeomorphologic characteristics were correlated with different morphometric parameters to identify the hydrological processes and demarcate the groundwater potential zones of the basin all the hydrological units and morphometric parameters were assigned suitable weightages according to their relative importance to groundwater potentiality to identify the most deficit surplus zones of groundwater based on hydrological characteristics integrated thematic maps reveal that 14 217 km2 of basin area falls under very good 32 486 km2 under good 23 353 km2 under moderate and 30 443 km2 under poor zones for groundwater potential from the sub basin wise prioritisation it has been inferred that sb iii scored highest groundwater potential followed by sb x result of morphometric analyses with the hydrologic parameters indicates that 99 area of sb iii and sb x are under very good to moderate groundwater potential zone this study clearly demonstrates that hydrological parameters in relation with morphometric analyses are useful to demarcate the prospect zones of groundwater

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

diffusive transport of water in porous feldspars from granitic saprolites in situ experiments using ftir spectroscopy abstract a novel experimental cell was developed for in situ measurements of transport phenomena in porous media using fourier transform infrared ftir spectroscopy the technique was employed at ambient pressure in the temperatures range of 11 44 c to study the h 2 o d 2 o exchange between water saturated weathered feldspars bulk porosity of 5 19 vol for feldspar from granitic saprolites and a surrounding aqueous liquid such measurements are an important step for understanding internal weathering reactions of feldspars in soils and aquifers effective diffusion coefficients d eff for water in water saturated porous feldspars were determined assuming one dimensional diffusion in a quasi homogeneous medium the values of d eff vary from 7 2 10 10 to 1 9 10 11 m 2 s and are 1 2 orders of magnitude lower than the diffusion coefficients d of protons and molecular h 2 o in liquid water the activation energy for the h 2 o d 2 o exchange process in porous feldspars ranges from 7 8 to 18 8 kj mol the results imply that the effective diffusivity of water is mainly controlled by physical properties of the feldspars like porosity pore connectivity pore geometry and distribution perthitic feldspars with homogeneous pore distribution in the albitic lamellas have diffusional tortuosity factors x d d eff between 3 and 10 while alkali feldspars with inhomogeneously distributed and disconnected pores have much higher x values up to 129 diffusion anisotropy has been verified for a vein perthite with diffusion perpendicular to the lamellas being faster by 0 3 0 5 log units than within the lamellas it has to be emphasized that the study is based only on few selected feldspars including perthitic feldspar and additional work on samples with different weathering stages is needed to test the importance of the different parameters controlling diffusive transport in the pore system

predicted tortuosity of muds tortuosity figures prominently in geochemical hydrological and geophysical calculations concerned with sediments but it is a difficult parameter to measure past theoretical models for predicting the tortuosity from porosity data do not work with marine muds and scientists and engineers have had to resort to entirely empirical models without a mechanistic explanation and with unknown predictive power we offer the first geometric model for the dependence of tortuosity on porosity in marine muds the model is based on the tortuosity of separated layers of nonoverlapping disks the fitted geometric constant in this model indicates that natural marine sediments act as if their fabric were made of disks with thickness diameter ratios very close to 1 2 which indicates a blocklike fabric with respect to diffusion the model was also applied to predict the tortuosity of a variety of sediments and soils not in the original database and it provides a satisfactory prediction of the mean trend in these data

diffusive transport of water in porous fresh to altered mid ocean ridge basalts abstract studying diffusive transport in porous rocks is of fundamental importance in understanding a variety of geochemical processes including element transfer primary mineral dissolution kinetics and precipitation of secondary phases here we report new findings on the relationship between diffusive transport and textural characteristics of the pore systems on the example of mid oceanic ridge basalts having different degree of alteration but very similar bulk pore volume diffusion processes in porous basalts were studied in situ using h 2 o d 2 o exchange experiments the effective diffusion coefficients of water molecules increase systematically from 5 05 10 11 to 1 19 10 10 m 2 s for fresh and moderately altered basalts and from 2 40 10 11 to 6 72 10 11 m 2 s for completely altered basalt as temperature increases from 5 to 50 c the activation energy of the diffusion process increases from 12 29 0 71 kj mol for fresh and moderately altered basalts to 14 3 1 33 kj mol for completely altered basalt the results indicate that neither the bulk porosity nor the degree of alteration can be used as proxies for the efficiency of element transport during morb water interaction the formation of secondary phases that replace primary minerals and fill the pore space in the rock leads to the formation of tiny pores and phases with large specific surface area these factors might have a dominant control on the transport properties of altered basaltic rocks

riverine sediment balance of the mackenzie delta northwest territories canada data acquisition by environment canada and others over the last 20 years now allows the first comprehensive synthesis of the riverine sediment balance of the mackenzie delta the data presented here are sediment inputs from the mackenzie and peel rivers at the delta head and river sediment transfers from the upper delta to the outer delta 1974 1994 in channel and overbank sedimentation including lakes post 1963 and in channel erosion along delta channels 1950 1981 these data indicate that the mean annual sediment input to the delta is about 128 mt and the corresponding loss to offshore is about 85 mt the net sedimentation of 43 mt is divided almost equally between the upper delta mostly on levees and lake beds and the outer delta mostly on lake shores gross sedimentation within the delta about 50 of which is on point bars is much higher estimated at about 103 mt annually the difference is the large amount of sediment reentrainment within the delta through bank erosion primarily along middle channel how much of this pointbar deposition is from settling of sediment delivered by the mackenzie and peel rivers as distinct from local sediment derived from bank scour within the delta is not known such within delta sediment exchange which could be as high as 50 mt might be important in determining the quality of sediment nutrients contaminants etc that it is being delivered offshore it would be naive to assume that all of this sediment is from the present day input of the mackenzie and peel rivers

perennial frost blisters of the outer mackenzie delta western arctic coast canada saturated floodplains in arctic deltas provide conditions favourable for frost mound growth little work has been reported from these settings to determine the origin of frost mounds and the controls on their distribution to assess the longevity of individual mounds or to quantify variation of mound distribution over time a case study is presented on low mounds in low centred syngenetic ice wedge polygons of big lake delta plain outer mackenzie delta in 2008 and 2009 12 mounds were examined by drilling to describe their morphologic variations and to investigate their growth processes the mounds containing a core of ice 15 to 58 cm thick were less than 1 m high and 3 7 to 8 5 m in diameter other mounds were over 10 m long organic inclusions in the ice bubble densities electrical conductivity profiles and ice crystal structure indicated that the mounds were hydrostatic frost blisters up to six frost blisters were found within individual polygons due to the relatively small volume of water needed to create each mound frost blister densities of greater than 1700 km 2 increased toward the wet centres of alluvial islands down gentle topographic gradients the frost blisters were perennial with individuals remaining identifiable on aerial photographs and satellite images for up to 10 years frost blisters collapsed along dilation cracks opened by hydrostatic uplift and by thawing from their sides caused by snow drifting and water ponding cyclical growth and decay of the mounds may degrade the visible polygonal network over time copyright 2013 john wiley sons ltd

low altitude remote sensing and gis based analysis of cropmarks classification of past thermal contraction crack polygons in central western poland abstract the examination of low altitude aerial photographs reveals the presence of more than 400 polygonal nets in central western poland polygons range from 5 to almost 70 m in diameter based on the polygons diameter and intersection angles we identified seven main types of nets geometry based on ground verification we interpreted them as past thermal contraction cracks filled mostly with sand i e sand wedge casts as favourable weather conditions and a proper land cover i e cultivated land are necessary for identifying polygonal nets the observed number of polygons is probably much underestimated the broad occurrence of former thermal contraction cracks polygons indicates that continuous permafrost was widespread in central western poland after the termination of the last glacial maximum lgm preliminary dating of the cracks infilling as well as polygon geometry suggest that thermal contraction cracking occurred in several different phases and that a time frame of a few thousand years is sufficient to form complex mature nets

field observations of syngenetic ice wedge polygons outer mackenzie delta western arctic coast canada 1 low centered ice wedge polygons in the big lake delta plain of the outer mackenzie delta are unusual because their bounding ramparts appear to have a single ridge twenty two ice wedges in the area were examined between 2006 and 2009 to describe their morphology and diagnose their growth processes the ground above ice wedges had a subtle microtopography with ridges of 0 12 m relief and 4 0 m total width bisected by troughs only 0 05 m wide and 0 09 m deep the troughs initially obscured by vegetation growth and organic matter were underlain by ice wedges with average widths that increased downward in the uppermost 1 m of permafrost from 0 03 to 0 95 m shoulders on the ice wedges indicated vertical growth stages temperatures near the top of permafrost were favorable to thermal contraction cracking and ice veins connected to the top of wedge ice were observed in the active layer at five sites these observations indicate the ice wedges are syngenetic and active although without dating control we cannot unequivocally dismiss the possibility that the wedges are epigenetic features that were truncated by a recent thaw unconformity muted relief above the ice wedges which is uncommon above epigenetic ice wedges was largely due to aggradation of the surface secondary ice wedges have not developed within the polygons suggesting that climate variability has not led to polygon network development in this area wedge ice occupied only about 1 5 of the uppermost 1 m of permafrost a much smaller volumetric proportion than in epigenetic settings

air temperature snow cover creep of frozen ground and the time of ice wedge cracking western arctic coast the time of ice wedge cracking is examined for several sites with young and old ice wedges along the western arctic coast the correlation between sharp air temperature drops and ice wedge cracking is highest where the snow cover is thin and least where the snow cover is thick the favoured duration and rate of a temperature drop that results in cracking is about 4 days at a rate of about 1 8 c d such temperature drops have a minimal effect in cooling the top of permafrost wherever there is an appreciable snow cover since short duration temperature drops often result in ice wedge cracking the thermal stresses that trigger cracking probably originate more within the frozen active layer than at greater depth in permafrost although most ice wedges tend to crack during periods of decreasing air temperatures about one third of those monitored have cracked during periods of increasing air temperatures long term measurements show that the active layer and top of permafrost move differentially all year in

sand dynamics at the mouth of a rock bound tide dominated estuary abstract the lowermost kennebec river is a relatively narrow deep bedrock cut estuary situated along the highly indented central coast of maine a large tidal prism and strong tidal currents control bedload sediment transport at the estuary mouth riverine sediment is introduced to the estuary during spring freshets when freshwater discharge may increase by an order of magnitude during the same time some of the existing estuarine sediment is exported to the nearshore a barrier adjacent to the estuary is the product of an abundant riverine sand supply and numerous bedrock ridges which anchor this sand deposit a variety of sedimentologic geomorphic and hydraulic data collected over a 14 year period document a clockwise sand circulation cell that involves the exchange of bedload among the entrance channel to the estuary adjacent beaches nearshore and offshore region tidal currents transport sand from the estuary through a subsidiary channel bordered on both sides by bedrock islands to an offshore subtidal bar northeast storm waves breaking along this outer bar move sand westward and landward toward the beach leading to the development of large bar complexes the welding of a bar complex to the western end of hunnewell beach occurs every 6 9 years and adds 2 300 000 m3 of sand to the shoreline sediment transport calculations along the outer bar are consistent with this volume of sand the sediment gyre is completed as beach sands are moved eastward along the beach and dumped into the estuarine channel this movement of sand is produced by wave action and tidal currents that enter the estuary peripherally during the flooding tide during the ebb cycle strong tidal currents flowing seaward through the subsidiary channel advect water from along the beach which enhances sand transport into the estuary thirteen years of beach profile surveys demonstrate a good correspondence between bar welding events and short term 1 4 years accretionary shoreline changes however the volumetric changes of hunnewell beach cannot be accounted for by bar welding alone the apparent movement of sand between hunnewell beach and other sand is further evidenced by the 135 year record of historical shoreline changes that reveal up to 200 m of shoreline excursions over a 26 year period these data suggest that erosional depositional trends along hunnewell beach are complex and the result of the exchange of sand among the adjacent beaches nearshore zone fox and wood island tombolos kennebec river channel and offshore region the effects of major spring floods and strong bedrock influences produce patterns of sedimentation and a distribution of sand bodies at the mouth of kennebec river that differ markedly from accepted estuarine models that are based on the relative importance of wave and tidal energy this study demonstrates the need to consider structural controls when using these models

the role of intragranular microtextures and microstructures in chemical and mechanical weathering direct comparisons of experimentally and naturally weathered alkali feldspars abstract electron microscopic observations of alkali feldspars from soils show that intragranular microtextures such as exsolution lamellae and microstructures primarily dislocations are both highly significant determinants of the weathering behaviour of these minerals in particular strained structure around intersecting edge dislocations in the plane of exsolution lamellae 6 01 dissolves at a rate which is orders of magnitude greater than unstrained feldspar producing a mesh of intersecting etch tubes extending 5 10 3 cm into the crystal as a result dissolution at dislocations is the major source of solutes during initial stages of chemical weathering in the field with progressive chemical weathering the most highly reactive feldspar is consumed by growth and coalescence of etch tubes but outer parts of the grain are physically weakened leading to mechanical flaking that increases available surface area and exposes further reactive sites in contrast previous dissolution experiments and microscopy of reacted surfaces have shown little or no correlation between dissolution rate and dislocation density and few visible signs of dissolution at particularly reactive sites to resolve the apparent discrepancy between field and laboratory behaviour we have carried out flow through dissolution experiments using ph 2 hcl at 25 c on three alkali feldspars with carefully characterized intragranular microtextures and microstructures these alkali feldspars were 1 eifel sanidine an alkali feldspar that has no microtextures at the tem scale and a low dislocation density 2 3 108 cm 2 and 3 naturally weathered alkali feldspars also from the shap granite which have the same microtextures as unweathered shap granite alkali feldspars but because they have been weathered have a lower density of dissolution reactive dislocations exposed on grain surfaces

influence of snow on near surface ground temperatures in upland and alluvial environments of the outer mackenzie delta northwest territories relations between snow cover active layer thickness and near surface ground temperatures were determined in 2005 2009 for a diverse range of alluvial and upland settings in the outer mackenzie delta here the snow cover developed primarily by wind redistribution with its spatial variation controlled by topography in uplands and vegetation height in allu vial lowlands snow cover was the primary influence on freeze back duration and the mean annual temperature at the top of permafrost ttop with the difference in median ttop between alluvial 3 7 c and upland 6 1 c settings related to the greater snow depth and soil moisture in the alluvial plain the active layer was generally deeper in the wet alluvial low lands where the average duration of active layer freeze back 101 days was nearly double the time taken in the well drained uplands 55 days the surface offset dts up to 11 c dominated the difference between annual mean air temperature amat and ttop dt in alluvial terrain dts varied with snow depth but in the uplands dts was more consistent from site to site the small thermal offset 2 c was slightly greater in alluvial terrain than in the uplands the overall range in dt 2 10 c led to a range during the study of 7 2 c in ttop at the sites the range in amat was 1 3 c but up to 1 7 c in ttop at any one site permafrost was well established throughout the area except adjacent to channels where ttop was close to 0 c

sedimentary processes bedforms and facies associated with a coastal headland portland bill southern uk this investigation presents new findings on the sedimentary processes and deposits associated with a coastal headland in a mixed tide wave setting using data compilation bathymetric and sediment distribution maps collected field data side scan sonar and seabed sampling and sand transport modelling sand transport pathways are described a on the basis of coupled system seabed morphology sand distribution and b from bed shear stress and medium grained sand transport rate simulations the presence of a sequence of sedimentary deposits associated with a complex suite of bedforms and sedimentary facies within an overall framework of limited sediment supply represents a gradient in shear stress and sand transport towards the headland these sequences are observed on both sides of portland bill tending towards a symmetrical distribution the sedimentary facies distribution is combined with sand transport rates and maximum bed shear stress distribution to suggest a conceptual model for sand dispersal and deposit formation around headlands sand dispersal can be explained in terms of a headland associated eddy bedload convergent zone concept maximum bed shear stress is observed at the tip of the headland and is associated with bedrock exposed on the seabed the sequence of sedimentary deposits away from the headland is sandbanks shambles and portland banks sand gravel flats sand shoals adamant and west shoals and rippled sand sheets the banks lie in an area of very high bed shear stress u 0 08 m s 1 this is greater than that for other tidal sandbanks not associated with headlands bank formation is the result of the strong convergent transport component enhanced by the development of transient headland eddies the sandbanks are to some extent also morphologically controlled i e the portland bank is affected by the deep bathymetry to the west side of portland bill the principal characteristic of headland associated eddy bedload convergent zones is the development of bed shear stress convergent zones on both sides of the headland two conceptually distinct regions of sedimentary processes associated with the coastal headlands are recognised a an inner zone with increasing gradients in sand transport and bed shear stress towards the headland and b an outer zone in which sand transport is away from the headland associated with a decrease in the bed shear stress these zones merge into a bed shear stress sand bedload transport convergent zone which enhances the formation of sandbanks around headlands thus headland associated sedimentary deposits are a complex system compared with the occurrence of isolated sandbanks described elsewhere the identification of a sequence of deposits related to and extending much farther from the headland than previously supposed demonstrates that the tidal stirring concept of headland associated sandbanks may explain the formation of headland associated sandbanks however it ignores the presence of a suite of sedimentary deposits around such headlands the conceptual model proposed here provides a sedimentological perspective on the formation and occurrence of headland associated deposits including sandbanks

the frequency of ice wedge cracking 1967 1987 at garry island western arctic coast canada the frequency of ice wedge cracking has been studied at garry island northwest territories for the 1967 1987 period sites have included low centre polygons intermediate centre polygons and polygons that do not fit any classification system analyses of crack frequency have included trough characteristics polygon characteristics and ice wedge types the results show that crack frequencies are highly variable within one site and also between two adjacent sites the correlation between crack frequency and a low air temperature is poor crack frequencies for a site with 59 wedges ranged from 8 to 42 between 1967 and 1979 and for a nearby site with 32 wedges from 22 to 75 between 1967 and 1987 in view of the wide range in crack frequencies at a given site the use of mean ice wedge growth rates for estimating ages of ice wedges and their casts in environmental reconstruction may be hazardous the data show that the common twofold classification into active and inactive wedges is difficult to apply be

evolution of swarna estuary and its impact on braided islands and estuarine banks southwest coast of india qualitative and quantitative evolution of the swarna estuary during the past 38 years 1967 2005 has been analysed by integrating the results of field surveys satellite images hydrodynamic modelling and topographic data in gis context significant changes in erosion accretion patterns of the estuarine banks inlet configuration and adjacent spits and origin morphology orientation and areal extent of fifteen braided islands have been estimated hydrodynamics of the region is studied through modelling and probable flow pattern that is responsible for morphological changes is discussed the simulated flow patterns indicate that current speeds are of the order of 10 20 cm s inside the estuary and of the order of 40 cm s at the mouth the right bank rb of the estuary is subject to net erosion and the left bank lb is subject to net accretion on an average 20 30 of the area of all braided islands would be flooded if the water level rises by 0 7 to 1 0 m islands of this estuary are morphologically very dynamic migrating towards north northeast and southwest directions and subject to net accretion whereas only one island i e the padu has lost its major portion of landmass a conceptual inverse distance weighted idw interpolation model has been generated and evaluated possible flooding on the estuarine shoals and braided islands due to heavy rainfall and or sea level rise the model reveals that the possibility of flooding will be higher for those islands which are located close to the rb than those close to the lb

the principles of cryostratigraphy abstract cryostratigraphy adopts concepts from both russian geocryology and modern sedimentology structures formed by the amount and distribution of ice within sediment and rock are termed cryostructures typically layered cryostructures are indicative of syngenetic permafrost while reticulate and irregular cryostructures are indicative of epigenetic permafrost cryofacies can be defined according to patterns of sediment characterized by distinct ice lenses and layers volumetric ice content and ice crystal size cryofacies can be subdivided according to cryostructure where a number of cryofacies form a distinctive cryostratigraphic unit these are termed a cryofacies assemblage the recognition if present of i thaw unconformities ii other ice bodies such as vein ice ice wedges aggradational ice and thermokarst cave pool ice and iii ice sand and gravelly pseudomorphs is also important in determining the nature of the freezing process the conditions under which frozen sediment accumulates and the history of permafrost

decadal shoreline assessment using remote sensing along the central odisha coast india one of the major requirements of planning coastal protection works is to understand the processes of erosion deposition sediment transport flooding and sea level changes which continuously alter the shoreline significant erosion can affect the stability and productivity of aquatic environment which may have severe implications for coastal inhabitants the middle coastal plains of odisha state on the east coast of india were investigated for morphological assessment of shoreline accurate demarcations of shorelines were carried out at parts of odisha coast specifically along gahirmatha paradip and coast above devi river to quantify erosion and accretion at annual to decadal scale for the years 1990 2000 and 2012 satellite derived remote sensing data landsat and irs p6 were used in the study digital shoreline analysis system discovered the eroded and accreted parts of the study area gahirmatha and coast above devi river experienced heavy erosion during 2000 2012 compared with 1990 2000 whereas paradip coast has comparatively undergone accretion during 2000 2012 some accreted spots are identified nearby river mouths which are attributed to heavy accretion of eroded materials by the action of sediment transport the detailed analysis reveals a maximum erosion of 124 33 and 154 m in a decade at gahirmatha paradip and coast above devi river respectively southern parts of gahirmatha coast showed highly dynamic behavior near hukitola bay and barrier island and are acting as a natural breakwater to conserve the shoreline this region had undergone severe geomorphologic changes due to natural as well as human interventions and poses a threat this coast exhibits unique reasons for erosion with various degrees of combinations of sediment depletion human activities high frequency of cyclones and floods sea level rise etc this study concludes that the shoreline of odisha coast is under heavy erosion and needs scientific and management attention

permafrost and climate change at herschel island qikiqtaruq yukon territory canada 1 herschel island in the southern beaufort sea is dominantly a glacier ice thrust feature composed of ice rich perennially frozen sediments climate data are available for herschel island from 1899 to 1905 and 1995 2006 air temperatures at herschel island are similar to sites on the adjacent mainland late winter snow depth is only about 20 cm or half the depth on the mainland and local topography defines the sites of annually recurring snowdrifts near surface ground temperatures thaw depths and ground ice contents have been investigated over a 750 m transect leading up collinson head the easternmost part of the island the ground temperature profile to 42 m depth indicates recent warming of permafrost because the temperature decreases with depth the temperature at 15 m depth is 8 0 c the same as the annual mean temperature at 1 m depth at windswept sites along the transect a simulation of the ground thermal regime calibrated with local ground properties equilibrated with the climate of 1899 1905 and driven by the climate of the region during the 20th century reproduces the present ground temperature profile and the annual temperature cycle for 1 m depth at windswept sites the model indicates that the mean annual temperatures at the top of permafrost and at 20 m depth have increased by 2 6 and 1 9 c respectively since 1899 1905 and the perturbation in ground temperature has reached about 120 m depth active layer thickness measured in the terrain types studied on herschel island is about 55 cm 15 to 25 cm greater than field data from these units collected in 1985

cessation of ice wedge development during the 20th century in spruce forests of eastern mackenzie delta northwest territories canada ice wedges are presently inactive in white spruce picea glauca forests of eastern mackenzie delta as shown by the absence of vein ice above ice wedges the maintenance of intact breaking cables and the abundance of rootlets propagating across ridge trough sequences at spruce forest sites near surface ground cooling rates and minimum near surface temperatures from the years 2003 2005 were above ice wedge cracking thresholds ground thermal conditions associated with cracking were recorded at a tundra peatland with active ice wedges annual mean permafrost temperatures at the spruce forest sites ranged from 1 8 to 2 9 c whereas at the tundra peatland the permafrost was colder than 6 c although winter air temperatures are similar throughout the study region deeper snow cover thicker active layers and warmer permafrost account for the more gradual seasonal cooling and warmer near surface temperatures recorded at the subarctic forest sites the subtle ridge to trough relief 12 35 cm of permafr

implications of pore space characteristics on diffusive transport in basalts and granites a detailed characterization of the pore space is crucial for understanding of transport and element transfer in rocks here the effect of differences in texture and content of secondary minerals on transport in pore systems was determined for two rocks of widespread occurrence mid ocean ridge basalts morb and granites pore space characteristics were analyzed by hg porosimetry intrusion of a molten alloy and synchrotron based x ray tomographic microscopy for evaluating the role of pore space characteristics for the prediction of diffusive transport data on porosity and the effective diffusion coefficient deff were compared extended connective pore systems due to cracks and mineral dissolution are present in samples of both rocks indicating high internal specific surface area uneven pore size distributions in altered morb samples can be assigned to secondary minerals pore spaces determined by x ray tomography used to determine main direction of pores in the 3 d orthogonal system suggest a slight anisotropy in log log plots both rocks show roughly a linear dependence of deff for h2o and compounds with comparable diffusivities d2o monovalent cations and anions on porosity but at same porosity deff is clearly higher in granitic than in basaltic samples this difference is increasing with decreasing porosity indicating that at low porosities the efficiency of element transport in basaltic samples is diminished mainly inherited by the presence of small pores slowing down diffusion the fact that diffusive transport in basaltic rocks is stronger dependent on porosity than in granitic rocks shows that also other rock characteristics such as pore size distribution and tortuosity of the pore network highly affected by the alteration degree can markedly affect transport and reactivity of pore solution

holocene sea level history of the canadian beaufort shelf new radiocarbon ages pertaining to the holocene sea level history of the canadian beaufort shelf are presented the ages were obtained on samples of freshwater and tidal marsh peat beds from offsho

late holocene climatic changes as detected by the growth and decay of ice wedges on the southern shore of hudson strait northern quebec canada the dating of cryoturbated palaeosols associated with past ice wedge activity on late holocene sandy fluvial terraces in a region of continuous permafrost leads to an interpretation of periods of ice wedge growth and active cracking that alternated with periods of decay dormancy and active layer deepening the reconstruc tion corresponds with palaeoclimatic information obtained from existing arctic wide and regional proxy rec ords the little ice age stands out as a period of intense ice wedge activity in the study area it was followed by a warm thawing interval during the first half of the twentieth century from ad 1946 to 1991 a well documented cooling of the climate took place which reactivated 94 of the studied ice wedges the pyramidal shape of ice wedge tops and the depths of the upgrowth features could be correlated between sites several kilometres apart clearly indicating a regional climatic response the mean annual air temperature dropped from about 7 8 c in 1946 to 8 9 c in 1991 the t