influence of permafrost distribution on groundwater flow in the context of climate driven permafrost thaw example from yukon flats basin alaska united states 1 understanding the role of permafrost in controlling groundwater flow paths and fluxes is central in studies aimed at assessing potential climate change impacts on vegetation species habitat biogeochemical cycling and biodiversity recent field studies in interior alaska show evidence of hydrologic changes hypothesized to result from permafrost degradation this study assesses the hydrologic control exerted by permafrost elucidates modes of regional groundwater flow for various spatial permafrost patterns and evaluates potential hydrologic consequences of permafrost degradation the yukon flats basin yfb a large 118 340 km2 subbasin within the yukon river basin provides the basis for this investigation model simulations that represent an assumed permafrost thaw sequence reveal the following trends with decreasing permafrost coverage 1 increased groundwater discharge to rivers consistent with historical trends in base flow observations in the yukon river basin 2 potential for increased overall groundwater flux 3 increased spatial extent of groundwater discharge in lowlands and 4 decreased proportion of suprapermafrost shallow groundwater contribution to total base flow these trends directly affect the chemical composition and residence time of riverine exports the state of groundwater influenced lakes and wetlands seasonal river ice thickness and stream temperatures presently the yfb is coarsely mapped as spanning the continuous discontinuous permafrost transition that model analysis shows to be a critical threshold thus the yfb may be on the verge of major hydrologic change should the current permafrost extent decrease this possibility underscores the need for improved characterization of permafrost and other hydrogeologic information in the region via geophysical techniques remote sensing and ground based observations

non predatory borings in phanerotrema gastropoda early silurian anticosti island quebec canada non predatory borings in phanerotrema gastropoda early silurian anticosti island quebec canada

layered and laterally constrained 2d inversion of resistivity data in a sedimentary environment quasi layered models often can represent the actual geology more accurately than smooth minimum structure models we present a 2d inversion scheme with lateral constraints and sharp boundaries lci for continuous resistivity data all data and models are inverted as one system producing layered solutions with laterally smooth transitions the models are regularized through lateral constraints that tie interface depths or thicknesses and resistivities of adjacent layers a priori information used to resolve ambiguities and to add for example geological information can be added at any point of the profile and migrates through the lateral constraints to parameters at adjacent sites similarly information from areas with well resolved parameters migrates through the constraints to help resolve areas with poorly constrained parameters the estimated model is complemented by a full sensitivity analysis of the model parameters supporting quantitative evaluation of the inversion result a simple synthetic model proves the need for a quasilayered 2d inversion when compared with a traditional 2d minimum structure inversion a 2d minimum structure inversion produces models with spatially smooth resistivity transitions making identification of layer boundaries difficult a continuous vertical electrical sounding field example from sweden with a depression in the depth to bedrock supports the conclusions drawn from the synthetic example a till layer on top of the bedrock hidden in the traditional inversion result is identified using the 2d lci scheme furthermore the depth to the bedrock surface is easily identified for most of the profile with the 2d lci model which is not the case with the model from the traditional minimumstructure inversion

statistical analysis of mixed motive shell borings in ordovician silurian and devonian brachiopods from northern and eastern canada hundreds of shell borings of different origin and displaying variable patterns were found in strophomenide pen tameride and orthide brachiopods of five paleozoic localities in northern and eastern canada the borings were analyzed using simple statistics as well as cluster and nonmetric multidimensional scaling analyses at the ordovician anticosti island locality all borings are parasitic or post mortem in origin while at the wenlock ludlow baillie hamilton island almost all borings are predatory at the remaining three localities borings represent a mix of predatory parasitic and post mortem domichnial borings in all three brachiopod taxa the proportions of which were controlled largely by brachio pod shell morphology and paleoecology for the strophomenides predatory borings can be segregated from parasitic and post mortem domichnial using simple and multivariate statistical analyses sowerbyella type strophomenides have a higher proportion of predatory borings at the lochkovian localities than at the ordovician localities while the reverse is true for the strophomena type strophomenides in pentamerides and orthides very few predatory borings are identified most bor ings were emplaced by parasitic or post mortem domichnial borers in pentamerides this is due to the internal structure of the shells which elevated the muscles of the organism above the shell floor rendering them inaccessible to boring preda tors in orthides more deliberate defense mechanisms such as toxins or external ornamentation may have deterred preda tion this study indicates that throughout the paleozoic interactions between borers and brachiopods were complex but can be elucidated using a large sample size and statistical analyses resume des centaines de perforations coquillieres d origines et de formes differentes ont eteobservees dans des brachio podes strophomenides pentamerides et orthides de cinq localites paleozoo ques du nord et de l est canadiens ces perfora tions ont eteanalysees al aide de methodes statistiques simples ainsi que d analyses typologiques et d analyses multidimensionnelles non metriques des ordres de grandeur ala localiteordovicienne de l o le d anticosti toutes les per forations sont d origine parasitique ou post mortem alors qu ala localitewenlockienne ludlowienne de l o le baillie hamilton elles sont presque toutes le resultat de la predation aux trois autres localites les trois taxons de brachiopodes presentent un melange de perforations d origines parasitique predatrice et domichniale post mortem dont les proportions respectives sont en bonne partie determinees par la morphologie des coquilles et le milieu paleoecologique en ce qui con cerne les strophomenides des analyses statistiques simples et multivariees permettent de distinguer les perforations resul tant de la predation des perforations parasitiques et domichniales post mortem les strophomenides de type sowerbyella presentent une plus grande proportion de perforations resultant de la predation aux localites lochkoviennes qu aux localites ordoviciennes alors que c est plutot l inverse pour les strophomenides de type strophomena tres peu de perforations re sultant de la predation sont recensees chez les pentamerides et les orthides la plupart etant le fait de foreurs parasitiques ou domichniaux post mortem en ce qui concerne les pentamerides ceci est dua la structure coquilliere interne dans la quelle les muscles de l organisme etaient au dessus du plancher de la coquille de sorte qu ils etaient inaccessibles aux pre dateurs foreurs chez les orthides des mecanismes de defense plus deliberes tels que des toxines ou l ornementation externe pourraient avoir empechela predation l etude indique que durant tout le paleozoo que les interactions entre les foreurs et les brachiopodes etaient complexes mais que ces dernieres peuvent etre elucidees al aide d echantillons de grande taille et d analyses statistiques traduit par la redaction

predatorial borings in late precambrian mineralized exoskeletons the late precambrian tube forming cloudina the earliest known animal to produce a mineralized exoskeleton shows evidence of having been attacked by shell boring organisms of more than 500 tubes from shaanxi province china 2 7 have rounded holes 40 to 400 micrometers in diameter the relation between the size of the holes and the width of the bored tubes suggests that the attacking organism was a predator selecting its prey for size if true this would be the oldest case of predation in the fossil record and would support the hypothesis that selection pressures from predation was a significant factor in the evolution of animal skeletons around the precambrian cambrian boundary

flux of4he from carnmenellis granite modelling of an hdr geothermal reservoir abstract the diffusion coefficient d of he in the carnmenellis granite recovered from the rosemanowes hot dry rock hdr geothermal reservoir is experimentally determined in the laboratory in a temperature range of 100 300 c temperature variation of d fits an arrhenius plot but yields an activation energy for he release from rock significantly lower than the value for feldspar or quartz suggesting that most of the he in the reservoir granite resides within grain boundaries and jointing cement and may be easily released the reservoir surface area s is estimated based on the laboratory determined value of d from granite and the measured4he contents of circulation fluids from rh 15 well in the first year of reservoir circulation 4he based reservoir surface area was about twice that based on222rn it increased and stabilized at about 6 times after 2 a the excess he release from newly opened up fracture surfaces within the reservoir during its expansion is shown to be responsible for the temporal increase in the he based reservoir surface area over that of rn

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

detecting unfrozen sediments below thermokarst lakes with surface nuclear magnetic resonance 1 a talik is a layer or body of unfrozen ground that occurs in permafrost due to an anomaly in thermal hydrological or hydrochemical conditions information about talik geometry is important for understanding regional surface water and groundwater interactions as well as sublacustrine methane production in thermokarst lakes due to the direct measurement of unfrozen water content surface nuclear magnetic resonance nmr is a promising geophysical method for noninvasively estimating talik dimensions we made surface nmr measurements on thermokarst lakes and terrestrial permafrost near fairbanks alaska and confirmed our results using limited direct measurements at an 8 m deep lake we observed thaw bulb at least 22 m below the surface at a 1 4 m deep lake we detected a talik extending between 5 and 6 m below the surface our study demonstrates the value that surface nmr may have in the cryosphere for studies of thermokarst lake hydrology and their related role in the carbon cycle

comparison of fluid inclusion decrepitation and acoustic emission profiles of westerly granite and sioux quartzite abstract acoustic emissions recorded during slow heating of rocks at 1 atm have generally been attributed to intergranular stresses generated by differences in thermal expansion coefficients and elastic moduli of neighboring grains these experiments have considered only the solid phases in analysis of the results and little attention has been given to the role of intragranular or grain boundary fluid inclusions in initiating or facilitating fracturing in principle fluid inclusions may be thought of as a special case in which the neighboring grains are fluids rather than the usual solid mineral phases the major differences are that 1 the number of inclusions per unit volume is usually 10 2 to 10 6 times greater than the number of mineral grains in that same volume and that 2 the volume increase with temperature for most fluids is 1 2 orders of magnitude greater than for minerals thus when fluid inclusion grains are considered the absolute number of grain to grain contacts in a given sample volume is several orders of magnitude greater than if the inclusions are not considered further the magnitude of the stresses between any two adjacent grains may be much higher if one of the grains is a fluid inclusion owing to the larger coefficient of thermal expansion of the fluid relative to a solid phase as a result substantial overpressures may be generated at the fluid inclusion grain mineral grain contact during heating experiments these overpressures result in brittle failure when the stress around the inclusion exceeds the local strength of the host crystal in fluid inclusion terminology this fracturing event is referred to as decrepitation samples of westerly granite and sioux quartzite were heated at 2 c min in a gas flow stage in order to determine the decrepitation profiles number of decrepitations as a function of temperature of these rocks decrepitation was monitored visually during heating experiments and was evidenced by the explosive loss of fluids from the inclusion during a fracturing event decrepitation produces microfractures which originate at decrepitated fluid inclusions and propagate outward into the surrounding mineral four different types of inclusions based on room temperature phase ratios and distribution within the host phase were noted in westerly granite type 1 inclusions contain a single aqueous liquid type 2 are two phase liquid rich inclusions type 3 are mostly one phase fluid inclusions that occur in dense clusters in plagioclase and type 4 are two phase moderate density h 2 o co 2 salt inclusions type 5 inclusions are one phase aqueous liquid inclusions observed in sioux quartzite fluid inclusions in westerly granite decrepitate between 75 and 573 c with peaks at 275 300 c and 400 450 c type 4 inclusions in westerly granite tend to decrepitate at lower temperatures 75 300 c than other inclusion types initial fracturing of the quartz host surrounding type 1 inclusions primary decrepitation generally occurs over the range 100 400 c and the fractures continue to propogate through the quartz secondary decrepitation during further heating from 400 to 573 c fluid inclusions in sioux quartzite decrepitate between 188 and 573 c with a broad maximum at 250 450 c primary decrepitation generally occurs at 200 450 c while secondary decrepitation occurs at 350 573 c in sioux quartzite some small inclusions in both samples do not decrepitate until the quartz transition temperature 573 c is reached decrepitation profiles determined in this study display many similarities and differences when compared to previously published acoustic emission profiles of westerly granite and sioux quartzite owing to fundamental differences in the techniques used to measure acoustic emission and decrepitation and the potentially different energies associated with the two events it is unclear whether decrepitating fluid inclusions are recorded during acoustic emission studies however if decrepitating fluid inclusions are being recorded during acoustic emission measurements then our results suggest that 1 decrepitation contributes more to low temperature portions of acoustic emission profiles than to high temperature portions for both sioux quartzite and westerly granite 2 compared to westerly granite a larger percentage of acoustic emissions in the low temperature decrepitation profile of sioux quartzite is due to fluid inclusions 3 decrepitating fluid inclusions not stresses generated by solid solid interactions cause the majority of intragranular fracturing in quartz below the temperature of the transition in both these rocks

new example of devonian predatory boreholes and the influence of brachiopod spines on predator success three abundant devonian frasnian brachiopod species from the lime creek fm of iowa usa douvillina arcuata devonoproductus walcotti and pseudoatrypa devoniana contain boreholes pooled drilling frequency is 10 6 the boreholes are small usually 1 0 mm diameter cylindrical and drilled perpendicular to the shell surface the borings appear to be type a boreholes as described by ausich and gurrola 1979 j paleontol 53 335 344 based on multiple criteria including statistically significant stereotypy with respect to valve preference site on valve and size class of the prey the boreholes are inferred to be predatory or parasitic in origin for each species the predator preferred to attack the valve closest to the substrate regardless of whether that was the pedicle or brachial valve boreholes were concentrated over the muscle field on each of the three species the success percentage percent of complete holes was statistically lower 2 p 0 04 for the spinose devonoproductus walcotti 33 33 than for the non spinose but otherwise morphologically similar douvillina arcuata 54 22 in spite of the fact that d walcotti has a thinner shell this is the first quantitative evidence for an anti predatory function for brachiopod spines

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

drill hole predation on tubes of serpulid polychaetes from the upper cretaceous of cuba the fossil record of drill holes in shelled invertebrates is focused primarily on bivalves and gastropods as prey the still limited reports on drill holes in serpulid polychaetes are principally recorded from cenozoic deposits and restricted to europe and antarctica this study documents drill holes on the serpulid polychaete pyrgopolon onyx from the upper cretaceous maastrichtian of pepito tey central cuba the oval shaped drill holes attributed to the ichnospecies oichnus ovalis were primarily caused by naticid gastropods probably by individuals of gyrodes sp known from the same formation using five methods the study on an assemblage of 53 non moldic specimens shows that 17 0 and 22 2 of the specimens was drilled this narrow range suggests that these methods can be used successfully for any time period for cylindrical shells including serpulids and scaphopods if the specimens of the sample are reasonably well preserved drill holes were randomly positioned with respect to the side of the tubes but drill holes are preferentially located between the ribs and in the middle part to slightly towards the posterior end of the tube suggesting that naticids selected the drill hole location efficiently on polychaetes with ornamentation already by the cretaceous the reasons for drilled tubes of p onyx are probably related to the withdrawal of their soft body deep inside the tube and or because of the presence of a calcareous operculum closing off the aperture the record of drilling predation in pyrgopolon is restricted to cretaceous deposits which may represent a bias in predation research focused only on cretaceous specimens more research on drilling predation of serpulids should be performed to better understand the function of ornamentation in deterring drilling to determine how common drilling was on serpulids in deep time and to evaluate the paleobiogeography of drilling predation

adaptive morphologies of the brachiopod fauna from danian coral mounds at faxe denmark abstract only few of the brachiopod species that lived in the late cretaceous chalk sea of northern europe survived the mass extinction at the cretaceous paleogene boundary however a rich brachiopod fauna rapidly evolved from the survivors and most of the vacant niches were filled in by the middle danian when a large cool water subphotic coral bryozoan mound complex was developed at faxe in the eastern part of the danish basin the brachiopod fauna of the complex comprises 17 species dominated by micromorphic species of similar types as those known from the upper cretaceous maastrichtian chalk from the same region all species are found in the coral mound facies and six of the species are restricted to this facies large sized species are rare both in terms of species numbers and abundance one species is adapted to a life between the branches of the cool water hexacorals dendrophyllia candelabrum and oculina becki secondarily free living species are close to absent this is in contrast to the maastrichtian chalk fauna where this group includes 10 species 24 of the total brachiopod fauna the otherwise great similarity in morphological adaptations in the brachiopods from the maastrichtian chalk and the danian coral mounds is remarkable and somewhat surprising as the latter almost lacks soft substrates the danian brachiopod fauna essentially represents a continuation of the maastrichtian fauna but in a very different habitat the similarity between the two faunas is explained by the abundance of small hard substrates notably bryozoans in both environments the brachiopods from faxe are one of the very few ancient examples of a rich brachiopod fauna from a coral mound environment

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

cryostratigraphy of late pleistocene syngenetic permafrost yedoma in northern alaska itkillik river exposure abstract extremely ice rich syngenetic permafrost or yedoma developed extensively under the cold climate of the pleistocene in unglaciated regions of eurasia and north america in alaska yedoma occurs in the arctic foothills the northern part of the seward peninsula and in interior alaska a remarkable 33 m high exposure along the lower itkillik river in northern alaska opened an opportunity to study the unmodified yedoma including stratigraphy particle size distribution soil carbon contents morphology and quantity of segregated wedge and thermokarst cave ice the exposed permafrost sequence comprised seven cryostratigraphic units which formed over a period from 48 000 to 5 000 14c yr bp including 1 active layer 2 intermediate layer of the upper permafrost 3 4 two yedoma silt units with different thicknesses of syngenetic ice wedges 5 buried peat layer 6 buried intermediate layer beneath the peat and 7 silt layer with short ice wedges this exposure is comparable to the well known mus khaya and duvanny yar yedoma exposures in russia based on our field observations literature sources and interpretation of satellite images and aerial photography we have developed a preliminary map of yedoma distribution in alaska

drill hole convergence and a quantitative analysis of drill holes in mollusks and brachiopods from the triassic of italy and poland abstract the history of predation is recorded primarily from drilling in cenozoic invertebrates quantitative data are uncommon from the triassic a period before the appearance and radiation of many known drill hole producers such as various gastropod families and octopods we present quantitative evidence of drilling from the late triassic carnian cassian formation of italy and the middle triassic anisian lower muschelkalk of poland documenting the first drill holes in triassic brachiopods a single brachiopod with a cylindrical complete drill hole was found in a brachiopod sample from of poland drilling percentage 0 3 n 365 the cassian formation yielded drill holes in gastropods bivalves and brachiopods indicating that more species are drilled than was known previously the minimum drilling percentage exclusive of incomplete drill holes of a sample from the stuores wiesen cassian formation is 1 7 n 116 5 prey selectivity is evident complete drill holes are primarily present in one gastropod species polygyrina lommeli 11 8 of specimens with a complete drill hole whereas other common species were not drilled single drill holes in brachiopods are cylindrical and complete and may be predatory in origin multiple drill holes in mollusks are common and drill holes are parabolic and often incomplete with a central boss resembling the shape of drill holes produced by extant naticid gastropods a survey of the paleozoic literature showed that such drill holes are also present in devonian and carboniferous brachiopods however naticids did not evolve until the cretaceous so we propose the term drill hole convergence for similar shaped drill holes produced by different organisms the triassic parabolic drill holes are not caused by domicile seeking or boring organisms instead we favor a predatory origin of these drill holes but we cannot entirely rule out parasitism surveying other triassic invertebrate assemblages should yield more evidence of drilling

hydrogeomorphic processes of thermokarst lakes with grounded ice and floating ice regimes on the arctic coastal plain alaska thermokarst lakes cover 20 of the landscape throughout much of the alaskan arctic coastal plain acp with shallow lakes freezing solid grounded ice and deeper lakes maintaining perennial liquid water floating ice thus lake depth relative to maximum ice thickness 1 5 2 0 m represents an important threshold that impacts permafrost aquatic habitat and potentially geomorphic and hydrologic behaviour we studied coupled hydrogeomorphic processes of 13 lakes representing a depth gradient across this threshold of maximum ice thickness by analysing remotely sensed water quality and climatic data over a 35 year period shoreline erosion rates due to permafrost degradation ranged from 0 2 m year in very shallow lakes 0 4 m up to 1 8 m year in the deepest lakes 2 6 m this pattern of thermokarst expansion masked detection of lake hydrologic change using remotely sensed imagery except for the shallowest lakes with stable shorelines changes in the surface area of these shallow lakes tracked interannual variation in precipitation minus evaporation p el with periods of full and nearly dry basins shorter term 2004 2008 specific conductance data indicated a drying pattern across lakes of all depths consistent with the long term record for only shallow lakes our analysis suggests that grounded ice lakes are ice free on average 37 days longer than floating ice lakes resulting in a longer period of evaporative loss and more frequent negative p el these results suggest divergent hydrogeomorphic responses to a changing arctic climate depending on the threshold created by water depth relative to maximum ice thickness in acp lakes copyright 2011 john wiley sons ltd

helium release during shale deformation experimental validation this work describes initial experimental results of helium tracer release monitoring during deformation of shale naturally occurring radiogenic 4he is present in high concentration in most shales during rock deformation accumulated helium could be released as fractures are created and new transport pathways are created we present the results of an experimental study in which confined reservoir shale samples cored parallel and perpendicular to bedding which were initially saturated with helium to simulate reservoir conditions are subjected to triaxial compressive deformation during the deformation experiment differential stress axial and radial strains are systematically tracked release of helium is dynamically measured using a helium mass spectrometer leak detector helium released during deformation is observable at the laboratory scale and the release is tightly coupled to the shale deformation these first measurements of dynamic helium release from rocks undergoing deformation show that helium provides information on the evolution of microstructure as a function of changes in stress and strain this article is protected by copyright all rights reserved

helium in solubility equilibrium with quartz and porefluids in rocks a new approach in hydrology 1 quartz crystals in sandstones at depths of 1200 m 1400 m below the surface appear to reach a solubility equilibrium with the 4he concentration in the surrounding pore or groundwater after some time a rather high 4he concentration of 4 5 10 3 cc stp 4he cm3 of water measured in a groundwater sample would for instance maintain a he pressure of 0 47 atm in a related volume this value is equal within analytical error to the pressure deduced from the measured helium content of the quartz and its internal helium accessible volume to determine this volume quartz crystals of 0 1 to 1 mm were separated from sandstones and exposed to a helium gas pressure of 32 atm at a temperature of 290 c for up to 2 months by crushing melting or isothermal heating the helium was then extracted from the helium saturated samples a volume on the order of 0 1 of the crystal volume is only accessible to helium atoms but not to argon atoms or water molecules by monitoring the diffusive loss of he from the crystals at 350 c an effective diffusion constant on the order of 10 9 cm2 s is estimated extrapolation to the temperature of 70 c in the sediments at a depth of 1400 m gives a typical time of about 100 000 years to reach equilibrium between helium in porewaters and the internal he accessible volume of quartz crystals in a geologic situation with stagnant pore or groundwaters in sediments it therefore appears to be possible with this new method to deduce a 4he depth profile for porewaters in impermeable rocks based on their mineral record

release of radiogenic noble gases as a new signal of rock deformation in this study we investigate the release of radiogenic noble gas isotopes during mechanical deformation we developed an analytical system for dynamic mass spectrometry of noble gas composition and helium release rate of gas produced during mechanical deformation of rocks our results indicate that rocks release accumulated radiogenic helium and argon from mineral grains as they undergo deformation we found that the release of accumulated 4he and 40ar from rocks follows a reproducible pattern and can provide insight into the deformation process increased gas release can be observed before dilation and macroscopic failure is observed during high pressure triaxial rock deformation experiments accumulated radiogenic noble gases can be released due to fracturing of mineral grains during small scale strain in earth materials helium and argon are highly mobile conservative species and could be used to provide information on changes in the state of stress and strain in earth materials and as an early warning signal of macroscopic failure these results pave the way for the use of noble gases to trace and monitor rock deformation for earthquake prediction and a variety of other subsurface engineering projects

near shore talik development beneath shallow water in expanding thermokarst lakes old crow flats yukon it is generally assumed that permafrost is preserved beneath shallow lakes and ponds in the western north american arctic where water depth is less than about two thirds of the late winter lake ice thickness here we present field observations of talik development beneath water as shallow as 0 2 m despite a lake ice thickness of 1 5 m in old crow flats ocf yt conditions leading to the initiation and development of taliks beneath shallow water were investigated with field measurements of shore erosion rates bathymetry ice thickness snow accumulation and lake bottom temperature near the shores of two expanding lakes in ocf the sensitivity of talik development to variations in lake bottom thermal regime was then investigated numerically where ice reached the lake bottom talik development was controlled by the ratio of freezing degree days to thawing degree days at the lake bottom fddlb tddlb in some cases spatial variations in on ice snow depth had a minimal effect on annual mean lake bottom temperature tlb but caused sufficient variations in fddlb tddlb to influence talik development where tlb was close to but greater than 0 c simulations indicated that the thermal offset allowed permafrost aggradation to occur under certain conditions resulting in irregular near shore talik geometries the results highlight the sensitivity of permafrost to small changes in lake bottom thermal conditions where the water column freezes through in early winter and indicate the occurrence of permafrost degradation beneath very shallow water in the near shore zone of arctic ponds and lakes

boreholes in mississippian spiriferide brachiopods and their implications for paleozoic gastropod drilling abstract bored specimens of the spiriferide brachiopod genera brachythyris and spirifer from several localities of the mississippian fort payne formation kentucky usa represent 7 0 of the total sampled population the boreholes are typically single complete circular in plan view and with their long axes perpendicular to the valve these traits and stereotypy with respect to the pedicle valve and the fold and sulcus are consistent with a predatory parasitic origin of the holes the presence of platyceratid gastropods in the fort payne localities with bored brachiopods the previously documented drilling abilities of these gastropods and the occurrence of a platyceratid snail attached to specimen of a bored devonian brachiopod atrypa argue for platyceratids as the most probable culprits

radon and thoron emission from lithophysae rich tuff under increasing deformation an experimental study 1 radon and thoron emissions from lithophysae rich tuff under increasing deformation are measured to determine how mechanical damage affects gas emission levels in tuffs mechanical properties of rocks under stresses should be carefully considered to properly interpret data from geochemical field monitoring two samples are uniaxially loaded up to failure while two others are unloaded at the end of the elastic phase in order to achieve the highest compaction of existing pores changes in the porosity of deformed samples are evidenced by helium pycnometer and microscopy analyses radon and thoron exhalation rates are measured on groups of two samples by alpha spectrometer technique results show that tuff samples are characterised by a dual porosity consisting of a macroporosity given by isolated large pores with sizes from mm up to cm scale and a microporosity ranging between microns to hundreds of microns at the end of the elastic phase pervasive pore collapse is observed due to the closure of the cm scale macropores this is mirrored by a significant decrease of radon and thoron release after failure a further reduction of porosity in the rock adjacent to the fault planes is observed due to extensive closure of both macropores and micropores at this stage radon and thoron emissions increase the formation of new exhaling surfaces is the main carrier of the bulk increase of radon and thoron exhalations strongly prevailing over the densification carried out from the compaction mechanisms in terms of volcanic hazard negative anomalies in radon emissions should be considered as indicators of forthcoming ruptures key words radon and thoron exhalation tuff deformation seismic precursor

drill hole analysis reveals evidence of targeted predation on modern brachiopods abstract if drill holes are made in prey either by mistaken or opportunistic predators or parasites rather than those which do so on a more regular basis we might predict that such drill holes will commonly be incomplete or repaired and show no evidence of behavioural familiarity such as size selection or constancy of attack site these predictions were used to examine the patterns of drill holes found in bulk samples of death assemblages of modern rhynchonelliform brachiopods from around new zealand four samples yielding data for five different taxa four terebratulides and one rhynchonellide were examined in each the proportion of incomplete or repaired holes was low samples of terebratella sanguinea fiordland and gyrothyris mawsoni antipodes islands show statistically significant evidence of both size selection and preferential drill hole siting the sample of notosaria nigricans waikawa shows only evidence of size selection examination of drill hole morphology and the co occurring gastropod fauna suggests that the distinctive countersunk holes in t sanguinea and g mawsoni were likely made by the trophonid gastropod xymene ambiguus aquarium experiments demonstrate that the ranellid gastropod argobuccinum tumidum is also capable of feeding on brachiopods but that the resulting hole is not likely to be readily recognisable in death assemblages

thermokarst lake to lagoon transitions in eastern siberia do submerged taliks refreeze as the arctic coast erodes it drains thermokarst lakes transforming them into lagoons and eventually integrates them into subsea permafrost lagoons represent the first stage of a thermokarst lake transition to a marine setting and possibly more saline and colder upper boundary conditions in this research borehole data electrical resistivity surveying and modelling of heat and salt diffusion were carried out at polar fox lagoon on the bykovsky peninsula siberia polar fox lagoon is a seasonally isolated water body connected to tiksi bay through a channel leading to hypersaline waters under the ice cover the boreholes in the centre of the lagoon revealed floating ice and a saline cryotic bed underlain by a saline cryotic talik a thin ice bearing permafrost layer and unfrozen ground the bathymetry showed that most of the lagoon was ice grounded in spring in bedfast ice areas the electrical resistivity profiles suggest that an unfrozen saline layer was underlain by a thick layer of refrozen talik the modelling suggests thermokarst lake taliks refreeze when submerged in saltwater with mean annual bottom water temperatures below or slightly above 0 c this occurs because the top down chemical degradation of newly formed ice bearing permafrost is slower than the cooling of the talik hence lagoons may pre condition taliks with a layer of ice bearing permafrost before encroachment by the sea and this frozen layer may act as a cap on gas migration out of the underlying talik

diminutive trace fossils in the chengjiang lagerstatte diminutive trace fossils described here have been well preserved in connection with certain pliable carapaces or skeletons of the chengjiang animals taphonomic evidence suggests that these traces were formed in situ the peculiar preservation indicates that some bilaterians of uncertain affinities seem to have been active at the burial site constituting an important group of the hidden majority of cambrian marine community this may be an essential feature closely associated with the palaeoecology and exceptional preservation of the cambrian fossil lagerstatten the rare preservation of such millimetre sized trace fossils raises further doubts about the timing of the initial benthic bilaterians by applying trace fossil evidence

numerical simulation of permafrost thermal regime and talik development under shallow thaw lakes on the alaskan arctic coastal plain 1 thaw lakes are one of the most obvious manifestations of the hydrological system at work in the tundra regions of the alaskan arctic coastal plain but the extent of the role of thaw lakes in arctic land atmosphere interactions and feedback has yet to be fully understood this study uses a two dimensional heat transfer model with phase change under a cylindrical coordinate system to simulate the long term influence of shallow thaw lakes on the thermal regime of permafrost and talik development on the alaskan arctic coastal plain on the basis of previous studies of permafrost and thaw lakes at barrow alaska a series of simulation cases was conducted using different combinations of long term mean lake bottom temperature and lake depth the simulated results indicate that shallow thaw lakes are a significant heat source to permafrost and talik for a thaw lake with a long term mean lake bottom temperature of greater than 0 0 c a talik forms under the thaw lake the maximum talik thicknesses vertical distance from the ground surface to the permafrost surface are 28 0 43 0 and 53 2 m 3000 years after the formation of a shallow thaw lake with long term mean lake bottom temperatures of 1 0 2 0 and 3 0 c respectively talik development rate is very high in the first several years after a thaw lake formation and decreases gradually with time no talik forms below a thaw lake with a long term mean lake bottom temperature equal to or lower than 0 0 c but the temperature of permafrost below the thaw lake increases with time three thousand years after the formation of a thaw lake with a long term mean lake bottom temperature of greater than or equal to 2 0 c ground temperature increases of more than 0 5 c occur as far as 300 m from the lake shore and as deep as about 400 m below the ground surface it is concluded that variation of long term mean lake bottom temperature has a significant influence on permafrost thermal regime and talik development continued monitoring for thaw lake bottom temperature and ground temperature under shallow thaw lakes is needed to further improve the simulation

a fossil record full of holes the phanerozoic history of drilling predation the evolutionary history of drilling predation despite a long and rich fossil record precambrian holocene contains a 120 m y gap late triassic early cretaceous drilled bivalve and brachiopod shells from jurassic deposits of hungary india and four localities documented in the literature indicate that drillers may have existed continuously throughout the mesozoic they may have been descendants of paleozoic predators unknown mesozoic carnivores or precursors of modern drillers a literature database suggests three major phases in the phanerozoic history of drilling predators 1 the paleozoic phase latest precambrian carboniferous dominated by rare to moderately frequent drillings in brachiopods and sessile echinoderms 2 the mesozoic phase permian early cretaceous with very rare or even facultative drillers that had little impact on marine benthic communities but nevertheless may have been present continuously and 3 the cenozoic phase late cretaceous holocene dominated by frequent gastropod drillings in mollusks

the effect of stress on radon emanation from rock a uranium bearing granitic rock of known radon emanation was deformed to failure under uniaxial stress radon emanation and microcrack activity were recorded continuously during the test radon concentration in the closed system was measured by an alpha detector a decrease in emanation was observed during the initial loading of the sample and is interpreted as associated with the closure of pre existing cracks within the rock at a uniaxial stress equal to approximately one half the ultimate strength a temporary increase 50 in the radon emanation was observed that correlated with an increase in microcracking within the sample when the stress was removed for several hours the original emanation was restored however once the specimen failed a temporary emanation increase of 120 was observed the emanation then decreased to a level nearly 5 greater than the prefailure specimen emanation

flow of mantle fluids through the ductile lower crust helium isotope trends heat and mass are injected into the shallow crust when mantle fluids are able to flow through the ductile lower crust minimum 3he 4he ratios in surface fluids from the northern basin and range province western north america increase systematically from low crustal values in the east to high mantle values in the west a regional trend that correlates with the rates of active crustal deformation the highest ratios occur where the extension and shear strain rates are greatest the correspondence of helium isotope ratios and active transtensional deformation indicates a deformation enhanced permeability and that mantle fluids can penetrate the ductile lithosphere even in regions where there is no substantial magmatism superimposed on the regional trend are local high 3he 4he anomalies indicating hidden magmatic activity and or deep fluid production with locally enhanced permeability identifying zones with high resource potential particularly for geothermal energy development

evolution of lakes and basins in northern alaska and discussion of the thaw lake cycle 1 we evaluated the development of lake basins on the central coastal plain of northern alaska on the basis of topographic profiles soil and ground ice surveys radiocarbon dating photogrammetric analysis and regional comparisons our analysis reveals that lake evolution is much more complex and less cyclic than theorized by previous investigations in the area we studied there was insufficient ground ice in the oldest terrain to form thaw lakes the aggradation of ice in the margins of drained lake basins was insufficient to heave the surface up to near original topographic conditions and the process occurs at too slow a rate for a thaw lake cycle to develop within the holocene accordingly we revised the conceptual model of lake and basin development to be consistent with the patterns and process we observed on the extensive sand sheets underlying most of the coastal plain developmental stages include 1 initial flooding of depressions to form primary lakes 2 lateral erosion with sorting and redistribution of sediments 3 lake drainage as the stream network expands 4 differential ice aggradation in silty centers and sandy margins 5 formation of secondary thaw lakes in the heaved centers of ice rich basins and infilling of ponds along the low margins and 6 basin stabilization

increase in radon emission due to rock failure an experimental study 1 radon anomalies are commonly observed prior to dynamic failure in the crust and are interpreted as cracking of the medium thus attracting considerable attention in understanding the precursory phenomena of earthquakes and volcanic activity in this study we have compared the starting radon emissions from low porosity crystalline lava phonolite samples with those from damaged and failed samples the damaged sample was loaded up to just beyond the end of the linear elastic phase as evidenced by the output of ae energy the increase in total porosity and a decrease in p wave and s wave velocity relative to the intact sample whereas the failed sample showed deformation behaviour characteristically brittle with increasing values of ae output and porosity as the sample approached macroscopic failure radon measurements have evidenced that dilatational microcracking of deformed sample produced no significant variation in radon emanation with respect to the intact sample in contrast after macroscopic failure radon emanation drastically increased therefore major finding from this study is that in the case of low porosity and relatively high strength crystalline lavas the development of a macroscopic fracture provides new large exhaling surface resulting in a substantial increase in radon emission rate

stratigraphy of the upper ordovician upper vaureal and ellis bay formations eastern anticosti island quebec marked facies changes occur in late ordovician strata assigned to the uppermost vaureal and ellis bay formations ashgill rawtheyan hirnantian on anticosti island quebec western anticosti features shales and carbonates whereas outcrops along the eastern coast contain prominent discontinuous mixed siliciclastic carbonate units detailed section measurement along the northeast coast allows for the first time accurate definition of seven new members within this uninterrupted sequence sands present in the upper vaureal and lower ellis bay formations in the east appear to have deterred the growth of muddy bottom brachiopod communities comparable to those in the western and central regions of anticosti sand units within the upper vaureal formation contain 1 m diameter colonies of paleofavosites coeval small coral patch reefs are found in the central part of the island where sands are absent the uppermost ellis bay formation of northeast anticosti is marked by a shallow subtidal coral algal onco

record of intense predatory drilling from upper jurassic bivalves of kutch india implications for the history of biotic interaction abstract the study of past biotic interactions is important not only to understand the paleoecological history of a community but also to test the evolutionary role of such interactions drill holes in invertebrate exoskeletons provide one of the very few scenarios where biotic interaction could be studied directly and the related hypotheses could be tested with statistical rigor hence the documentation and interpretation of the spatio temporal patterns of drill hole frequencies has been the subject of extensive paleontological research the two main gastropod groups responsible for the drilling predation in modern marine environment arose in cretaceous as supported by their body fossil however the drill holes have been reported from the fossils of as far back as precambrian age the trend shows an overall low but variable intensity in paleozoic and mesozoic and a significant increase in cenozoic there are few reported cases of drilled bivalves from the mesozoic although in those instances frequencies are fairly low most of the previous records of drilling predation during paleozoic and mesozoic come from north america and western europe here we report 148 drilled bivalve specimens of a single species from the upper jurassic horizon in western india this is highest in number for any taxon ever recorded since precambrian to cretaceous the frequency of drilling constitutes 30 of shells of the same species examined this drilling frequency is highest when compared to all the reported mesozoic drilling frequencies in bivalves the shapes of the drill holes are indicative of gastropod predation the drilling gastropods responsible for these lethal attacks are also similar to their modern counterparts in terms of their highly selective prey choice and site specificity these results suggest that 1 mesozoic bivalves were preyed upon by drilling gastropods often with high intensities and 2 the specialized characters of modern drilling predators were also present in mesozoic this largely unexplored record of bivalve drill holes from the middle mesozoic contradicts the general trend of mesozoic quiescence as claimed by most researchers

boring predation and mesozoic articulate brachiopods abstract a systematic survey of all the mesozoic brachiopods in the large collections of the sedgwick museum cambridge university has revealed more than 213 predatory boreholes from a wide range of largely british localities it seems likely that this type of predation was not infrequent at least locally as evidenced by the proportion of bored valves at some localities and the degree of stereotypy shown in borehole positioning the size of the boreholes and their neat circular cross sections suggest that they were made by large epifaunal predators using chemical attack and those of post albian age may be comfortably if not confidentally assigned to muricid gastropods although it is likely that bivalves with their greater flesh yields were the preferred prey item in most mesozoic shelly benthic communities it is apparent that boring predators may have resulted in a significant predation pressure on articulate brachiopods

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

an anomalous radon decrease in groundwater prior to an m6 0 earthquake a possible precursor a significant decrease in the radon concentration of artesian groundwater was observed at a well established observation site in northeast japan about two days before an m 6 0 earthquake occurred about 200 km from the site on the basis of a concurrent in situ minus 126 m temperature drop of the groundwater the authors infer that precursory changes in regional stress were locally amplified near this site and resulted in the temporary mixing of cooler radon poor groundwater into the normal artesian flow

morphometric analysis of predatory drillholes abstract quantitative studies of post jurassic predatory drillholes assume that drill holes were made by either naticid or muricid gastropods however other potential predators can leave similar traces and the traditional method of discrimination based on differences in vertical shape of drillholes cylindrical vs countersunk is not always applicable poor preservation or thin shells may prevent identification a multivariate morphometric approach including principal component analysis pca canonical variate analysis cva and size free discriminant analysis is suggested here as a supplementary method i test the approach by analyzing 98 drillholes made in the valves of the thin shelled bivalve mulinia coloradoensis collected from subfossil deposits in northeastern baja california using traditional criteria 10 10 2 of 98 drillholes were not correctly identified morphometric analyses indicate that in planar view muricid and naticid drillholes do not differ in shape however they perfectly discriminate in size the cylindrical drillholes oichnus simplex attributed to muricid predators are significantly smaller than countersunk ones oichnus paraboloides made most likely by naticid gastropods the results do not necessarily undermine the validity of the traditional ichnotaxonomy muricids tend to produce smaller drillholes than naticids nevertheless the vertical shape of a drillhole may be a function of both the type of predator and the size of hole drilled more than half of the unidentified drillholes 6 out of 10 from an independent group characterized by a more oval shape octopod drilling the traditional method supported by the morphometric methods employed here is a powerful tool for analysis of drillholes it may be valuable not only as a tool for analysis of muricid and naticid drillholes but also as a method for comparative analysis of drillholes of unknown source found throughout the phanerozoic fossil record

diffusive helium emissions as a precursory sign of volcanic unrest significant increases in helium emissions from the soil and 3 he 4 he ratios in groundwater on el hierro island canary islands spain were observed prior to the 2011 2012 submarine eruption off the coast of the island the changes of diffusive helium emissions rate were observed one month prior to the submarine eruption onset 12 october 2011 and the major increase preceded increases in seismic energy release during the volcanic unrest measured 3 he 4 he ratios in groundwaters from a well in el hierro island increased from 2 3 r a to 7 2 r a r a 3 he 4 he ratio in air 1 month prior to the eruption onset and reached a peak of 8 2 r a indicating a dominant magmatic contribution to the dissolved gases in ground waters 3 he 4 he values and diffusive helium emission studies have been extremely important for forecasting the onset of the volcanic unrest and subsequent volcanic eruption an aseismic exsolution of magmatic gases from magma bodies beneath el hierro island through fractures and vertical permeability structures increased the diffusive helium emission rate prior to episodes of seismic energy release associated with the volcanic unrest

airborne electromagnetic imaging of discontinuous permafrost 1 the evolution of permafrost in cold regions is inextricably connected to hydrogeologic processes climate and ecosystems permafrost thawing has been linked to changes in wetland and lake areas alteration of the groundwater contribution to streamflow carbon release and increased fire frequency but detailed knowledge about the dynamic state of permafrost in relation to surface and groundwater systems remains an enigma here we present the results of a pioneering 1 800 line kilometer airborne electromagnetic survey that shows sediments deposited over the past 4 million years and the configuration of permafrost to depths of 100 meters in the yukon flats area near fort yukon alaska the yukon flats is near the boundary between continuous permafrost to the north and discontinuous permafrost to the south making it an important location for examining permafrost dynamics our results not only provide a detailed snapshot of the present day configuration of permafrost but they also expose previously unseen details about potential surface groundwater connections and the thermal legacy of surface water features that has been recorded in the permafrost over the past 1 000 years this work will be a critical baseline for future permafrost studies aimed at exploring the connections between hydrogeologic climatic and ecological processes and has significant implications for the stewardship of arctic environments

quasi 3d modeling of airborne tem data by spatially constrained inversion we present a new methodology spatially constrained inversion sci that produces quasi 3d conductivity modeling of electromagnetic em data using a 1d forward solution spatial constraints are set between the model parameters of nearest neighboring soundings data sets models and spatial constraints are inverted as one system the constraints are built using delaunay triangulation which ensures automatic adaptation to data density variations model parameter information migrates horizontally through spatial constraints increasing the resolution of layers that would be poorly resolved locally sci produces laterally smooth results with sharp layer boundaries that respect the 3d geological variations of sedimentary settings sci also suppresses the elongated artifacts commonly seen in interpretation results of profile oriented data sets in this study sci is applied to airborne time domain em data but it can also be implemented with other ground based or airborne data types

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

helium and argon isotopes in rocks minerals and related ground waters a case study in northern switzerland abstract to address the problems related to the transfer of helium and argon isotopes from rocks into related aquifers the concentrations of u th li and k and helium and argon isotopes were measured in a sedimentary sequence from tertiary to permo carboniferous and in crystalline rocks in northern switzerland in addition to whole rock samples mineral separates have also been investigated the observed concentrations of 3 he 4 he and 40 ar in rocks minerals and groundwaters are compared to calculated values which would result from in situ radiogenic production in a closed system this comparison shows that the rocks and minerals have almost completely lost radiogenic in situ produced helium loss of 3 he and 4 he has been controlled by different retention capacities of the rock forming and accessory minerals and fillings therefore measured 3 he 4 he ratios in these rocks can differ from the calculated production ratios the deviation is generally less than a factor of 3 however in certain chemical sediments e g anhydrites elevated ratios of 3 he 4 he up to 15 10 8 which is 20 times the production ratio were observed it is postulated that 3 h the precursor of 3 he might be chemically bound in such sediments during the 12 3 years half life of 3 h and that the beta decay energy of 3 h is too small to liberate 3 he the calculated closed system concentrations of helium in groundwater exceed the measured ones by up to three orders of magnitude implying that the water rock system has not been a closed system since the time of sedimentation and that movable waters have removed helium to a discharge area and to the atmosphere stagnant old waters however could contain high concentrations of helium and supply it to younger movable waters aquitards with low permeability permian shales appear to be a more important source of helium isotopes than water bearing rocks permian sandstones high abundances of all parent elements in the shales almost complete loss of radiogenic helium and the enhanced production ratio of 3 he 4 he 7 2 10 8 in these rocks similar to the ratio observed in the neighbour permian aquifer 9 4 10 8 suggest the shale as a major source of helium isotopes for this aquifer and diffusion as a principal process for helium transfer from the stagnant porewaters in shales into the movable waters in sandstones some sedimentary rocks e g permian sandstones and shales contain more helium than could have been produced since the time of sedimentation while permian sandstones mainly have retained this excess rare gas component they have released radiogenic helium the difference in the retention of these two components most probably demonstrates that migration of radiogenic helium from damage tracks along crystal imperfections to grain boundaries is an important process controlling its loss the abundances of excess 3 he and 4 he in rocks cannot be predicted by in situ production calculations studies of rocks and minerals are required the average ratio of 40 ar 36 ar 385 in groundwaters collected from permian sediments from the weiach borehole is much higher than that in the aquifers from the crystalline basement below the sediments radiogenic 40 ar in permian sediments is mainly liberated by diagenetic water rock interactions the low contribution of radiogenic 40 ar in deep aquifers of the crystalline basement and the fact that chlorine concentrations in groundwaters from the basement are also much lower than in the overlaying permian aquifer eliminates a hypothetical upwards fluid flux from this study we envisage intrabasin sources for helium and argon isotopes in groundwaters with mainly lateral migration of waters through sedimentary layers at different rates and diffusion of helium from slower velocity older waters in more stagnant zones shales into flow passes with highervelocity younger waters in sections with higher permeability sandstones an external source for noble gases is not required in such a model

rapid degradation of permafrost underneath waterbodies in tundra landscapes toward a representation of thermokarst in land surface models waterbodies such as lakes and ponds are abundant in vast arctic landscapes and strongly affect the thermal state of the surrounding permafrost in order to gain a better understanding of the impact of small and medium sized waterbodies on permafrost and the formation of thermokarst a land surface model was developed that can represent the vertical and lateral thermal interactions between waterbodies and permafrost the model was validated using temperature measurements from two typical waterbodies located within the lena river delta in northern siberia impact simulations were performed under current climate conditions as well as under a moderate and a strong climate warming scenario the performed simulations demonstrate that small waterbodies can rise the sediment surface temperature by more than 10 c and accelerate permafrost thaw by a factor of between 4 and 5 up to 70 of this additional heat flux into the ground was found to be dissipated into the surrounding permafrost by lateral ground heat flux in the case of small shallow and isolated waterbodies under moderate climate warming the lateral heat flux was found to reduce permafrost degradation underneath waterbodies by a factor of 2 under stronger climatic warming however the lateral heat flux was too small to prevent rapid permafrost degradation the lateral heat flux was also found to strongly impede the formation of thermokarst despite this stabilizing effect our simulations have demonstrated that underneath shallow waterbodies 1 m thermokarst initiation happens 30 to 40 years earlier than in simulations without preexisting waterbody

boreholes in the middle devonian blastoid heteroschisma and their implications for gastropod drilling abstract boreholes in over 100 specimens of the devonian blastoid heteroschisma and the presence of the gastropod platyceras orthonychia sp attached to a specimen of heteroschisma subtruncatus hall 1858 suggest that platyceratid gastropods were capable of drilling their hosts at least as early as the middle devonian and thus represent the first known gastropods to have evolved this ability the presence of similar holes in numerous other devonian and mississippian blastoids and the occurrence of several additional examples of platyceratids attached to blastoids indicate that the interaction between gastropods and blastoids was not infrequent as in the case of the gastropod crinoid interaction this relationship is interpreted as having been parasitic rather than predatory the parasitic drilling platyceratids may have been a factor in the paleozoic precursor of the mesozoic marine revolution some of the anti predatory defenses of crinoids described from the late paleozoic may have been strategies of avoiding platyceratid infestation

modeling study of talik freeze up and permafrost response under drained thaw lakes on the alaskan arctic coastal plain 1 numerical simulations were conducted to investigate the long term impact of thaw lake drainage on the thermal regime of ground under and around drained thaw lakes on the alaskan arctic coastal plain the numerical model used in this study is a two dimensional unsteady finite element model for heat transfer with phase change under a cylindrical coordinate system the initial conditions are the simulated ground thermal regime and talik thickness data at year 3000 under a thaw lake with long term mean lake bottom temperatures of 1 0 2 0 and 3 0 c near barrow alaska the simulated results indicate that lake drainage leads to a rapid freeze up of talik and a substantial decrease in permafrost temperatures under the former lake bottom the initial ground temperature conditions have significant influence not only on the talik freeze up time but also on the permafrost temperature decrease processes after thaw lake drainage taliks with thicknesses of 28 43 and 53 m under the lake will freeze up completely by 40 106 and 157 years and the corresponding ratios of upward and downward freeze up depths for the three simulation cases are 1 8 0 1 7 6 and 1 6 1 respectively after completion of talik freeze up permafrost temperatures still decreased with time and gradually reached a relatively stable value depending on the initial ground temperature and the distance to the former lake bottom

transient electromagnetic sounding for groundwater the feasibility of using the transient electromagnetic sounding ts or tdem method for groundwater exploration can be studied by means of numerical models as examples of its applicability to groundwater exploration we study four groundwater exploration problems 1 mapping of alluvial fill and gravel zones over bedrock 2 mapping of sand and gravel lenses in till 3 detection of salt or brackish water interfaces in freshwater aquifers and 4 determination of hydrostratigraphy these groundwater problems require determination of the depth to bedrock location of resistive high porosity zones associated with fresh water determination of formation resistivity to assess water quality and determination of lithology and geometry respectively the ts method is best suited for locating conductive targets and has very good vertical resolution unlike other sounding techniques where the receiver transmitter array must be expanded to sound more deeply the depth of investigation for the ts method is a

changes in groundwater chemistry before two consecutive earthquakes in iceland precursor events to earthquakes are rarely reproduced measurement of groundwater chemistry in iceland between 2008 and 2013 reveals distinct changes prior to two consecutive m5 earthquakes

a case of intense predatory drilling of brachiopods from the middle miocene of southeastern poland abstract the documentation of biotic interactions in the fossil record is important not only to understanding the earth s paleoecological history but also to testing the evolutionary role of such interactions drill holes in invertebrate shells provide one of the most direct and easily interpretable signals of such interactions and the documentation and interpretation of the spatio temporal patterns of drill hole frequencies in a variety of invertebrate taxa has been the subject of extensive paleontological research for brachiopods the most recent summaries suggest that the record of drill holes extends back to the early paleozoic shows an increase in the devonian and remains highly variable through the rest of the paleozoic there are few reported cases of drilled brachiopods from the mesozoic although in those few instances on record frequencies can be as high as in the paleozoic to date only a few drilled brachiopods have been reported from the record of the cenozoic here we report on over 500 drilled brachiopod specimens constituting 39 9 of all brachiopod shells examined from a single middle miocene locality in southeastern poland this drilling frequency is high when compared to two additional middle miocene localities in poland where frequencies are 2 0 and 3 7 these results suggest that 1 cenozoic brachiopods were predated upon by drilling gastropods often with high intensities and 2 in the miocene drilling frequencies could be highly variable even at proximate localities the largely unexplored record of brachiopod drill holes across the late mesozoic and cenozoic could provide additional evidence for the mesozoic marine revolution

transient electromagnetic surveys for the determination of talik depth and geometry beneath thermokarst lakes thermokarst lakes are prevalent in arctic coastal lowland regions and sublake permafrost degradation and talik development contributes to greenhouse gas emissions by tapping the large permafrost carbon pool whereas lateral thermokarst lake expansion is readily apparent through remote sensing and shoreline measurements sublake thawed sediment conditions and talik growth are difficult to measure here we combine transient electromagnetic surveys with thermal modeling backed up by measured permafrost properties and radiocarbon ages to reveal closed talik geometry associated with a thermokarst lake in continuous permafrost to improve access to talik geometry data we conducted surveys along three transient electromagnetic transects perpendicular to lakeshores with different decadal scale expansion rates of 0 16 0 38 and 0 58 m year we modeled thermal development of the talik using boundary conditions based on field data from the lake surrounding permafrost and a borehole independent of the transient electromagnetics a talik depth of 91 m was determined from analysis of the transient electromagnetic surveys using a lake initiation age of 1400 years before present and available subsurface properties the results from thermal modeling of the lake center arrived at a best estimate talk depth of 80 m which is on the same order of magnitude as the results from the transient electromagnetic survey our approach has provided a noninvasive estimate of talik geometry suitable for comparable settings throughout circum arctic coastal lowland regions

assessing the importance of drilling predation over the palaeozoic and mesozoic abstract plausible predatory palaeozoic and mesozoic drillholes have been reported in the literature from 62 localities mainly from north america and western europe most of which were discovered in the last 20 years twenty nine of these reports include sufficient data to be statistically valid analyses of these data suggest that there was a highly significant increase in drillhole and hence predator size in the early devonian which may reflect a change in predatory taxa as part of the mid palaeozoic marine revolution in this study frequency of drillholes in particular species has been examined examination of drilling frequency suffered by individual taxa from a range of palaeozoic and mesozoic sites showing that these are highly variable just as they are between different holocene localities nevertheless levels of up to 50 in the palaeozoic and 40 in the mesozoic suggest that at least locally drillers did exert an important selection pressure analysis of the currently available data set reveals no significant change in drilling frequency over the palaeozoic and mesozoic there are fewer records of drilling predation from the palaeozoic and mesozoic than from the cenozoic at present however it is difficult to assess whether drilling was truly less widespread than in the cenozoic or whether at least part of the problem is taphonomic loss of information in particular in the late palaeozoic and mesozoic it is striking that relatively few reports involve molluscan prey despite their attractiveness as profitable prey with high flesh yield when compared with the apparently more frequently drilled brachiopods however study of the style of preservation of drilled molluscs that were mostly originally aragonitic suggests that drillholes are only preserved in faunas which are exceptionally preserved such that the original microstructure is still observable by contrast brachiopods which were either originally phosphatic or calcitic have much better preservation potentials and therefore may be more likely to show drillholes an understanding of the preservation biases involved in the recognition of drillholes may suggest suitable localities for further research more data from a suite of localities world wide are required for a more detailed analysis of patterns of drilling predation in the palaeozoic and mesozoic

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