the structure biological activity and biogeochemistry of cryoconite aggregates upon an arctic valley glacier longyearbreen svalbard glacier surfaces support unique microbial food webs dominated by organic and inorganic debris called cryoconite observations from longyearbreen spitsbergen show how these aggregate particles can develop an internal structure following the cementation of mineral grains mostly quartz and dolomite by filamentous microorganisms measurements of carbon and dissolved o2 show that these microorganisms mostly cyanobacteria promote significant rates of photosynthesis average 17 gc g 1 d 1 which assist aggregate growth by increasing the biomass and producing glue like extracellular polymeric substances the primary production takes place not only upon the surface of the aggregates but also just beneath due to the translucence of the quartz particles however since total photosynthesis is matched by respiration average 19 gc g 1 d 1 primary production does not contribute directly to cryoconite accumulation upon the glacier surface the microorganisms therefore influence the surface albedo most by cementing dark particles and organic debris together rather than simply growing over it time lapse photographs show that cryoconite is likely to reside upon the glacier for years as a result of this aggregation these observations therefore show that a better understanding of the relationship between supraglacial debris and ablation upon glaciers requires an appreciation of the biological processes that take place during summer

mcs based psha procedure and generation of site specific design spectra for the seismicity characteristics of chinamcs based psha procedure and generation of site specific design spectra for the seismicity characteristics

using ftir spectroscopy to characterise the soil mineralogy and geochemistry of cryoconite from aldegondabreen glacier svalbard mineralogical and geochemical diversity in cryoconite granules from aldegondabreen glacier was investigated using ftir spectroscopy results suggest that the technique is an effective tool for investigating mineralogy and identifying spatial differences in geochemistry based upon characteristic spectral signatures

evolution of cryoconite holes and their contribution to meltwater runoff from glaciers in the mcmurdo dry valleys antarctica cryoconite holes are water filled holes in the surface of a glacier caused by enhanced ice melt around trapped sediment measurements on the ablation zones of four glaciers intaylorvalley antarctica show that cryoconite holes cover about 4 6 of the ice surface they typically vary in diameter from 5 to 145 cm with depths ranging from 4 to 56 cm in some cases huge holes form with 5 m depths and 30 m diameters un like cryoconite holes elsewhere these have ice lids up to 36 cm thick and melt from within each spring about one half of the holes are connected to the near surface hydrologic system and the remainder are isolated the duration of isolation estimated from the chlor ide accumulation in hole waters commonly shows ages of several years with one hole of 10 years the cryoconite holes in the mcmurdo dryvalleys create a near surface hydro logic system tens of cm below the ice surface the glacier surface itself is generally frozen and dry comparison of water levels between holes a few meters apart shows independent cycles of water storage and release most likely local freeze thaw effects control water passage and therefore temporary storage rough calculations indicate that the holes gen erate at least 13 of the observed runoff on the one glacier measured this hydrologic system represents the transition between a melting ice cover with supraglacial streams and one entirely frozen and absent of water abstract cryoconite holes are water filled holes in the surface of a glacier caused by enhanced ice melt around trapped sediment measurements on the ablation zones of four glaciers intaylorvalley antarctica show that cryoconite holes cover about 4 6 of the ice surface they typically vary in diameter from 5 to 145 cm with depths ranging from 4 to 56 cm in some cases huge holes form with 5 m depths and 30 m diameters un like cryoconite holes elsewhere these have ice lids up to 36 cm thick and melt from within each spring about one half of the holes are connected to the near surface hydrologic system and the remainder are isolated the duration of isolation estimated from the chlor ide accumulation in hole waters commonly shows ages of several years with one hole of 10 years the cryoconite holes in the mcmurdo dryvalleys create a near surface hydro logic system tens of cm below the ice surface the glacier surface itself is generally frozen and dry comparison of water levels between holes a few meters apart shows independent cycles of water storage and release most likely local freeze thaw effects control water passage and therefore temporary storage rough calculations indicate that the holes gen erate at least 13 of the observed runoff on the one glacier measured this hydrologic system represents the transition between a melting ice cover with supraglacial streams and one entirely frozen and absent of water

temporal variations in physical and chemical features of cryoconite holes on canada glacier mcmurdo dry valleys antarctica cryoconite holes in the mcmurdo dry valleys are ice lidded thus isolating the pools of water from the atmosphere and from potential surface melt hourly measurements of ice and water temperature and water electrical conductivity ec were recorded to broadly characterize the physical and chemical changes on daily to seasonal timescales overall subsurface ice water temperatures were typically several degrees warmer than air temperatures underscoring the importance of subsurface solar heating at no time was surface melt observed and the holes melted from within detailed differences in the timing and magnitude of both temperature and ec variations during melt out and freezeup existed between holes despite short separation distances 1 m we attribute these differences to small scale changes in the optical characteristics of the ice and perhaps different efficiencies in hydrologic connections between holes the holes melt deepened quickly in the first half of the summer before slowing to a rate equal to the rate of surface ablation that kept hole depth constant for the remainder of the season the relatively constant ec of the hole waters during midsummer indicates that these holes were connected to a subsurface water system that flushed the holes with fresher meltwater the early and late season ecs are dominated by freeze thaw effects that concentrate dilute the solutes we speculate that high solute concentrations imply high nutrient concentrations in early summer that may help alleviate potential stresses caused by the production of new biomass after the winter freeze

late precambrian pennatulids sea pens from the eastern yangtze gorge china paracharnia gen nov abstract pennatulids preserved as membranous carbonised compressions from the shibantan member dengying formation sinian system in the eastern yangtze gorge hubei province represent the first genuine discovery of the late precambrian ediacara type metazoan remains in china the specimens were initially referred to charnia ford 1958 and described as c dengyingensis by ding and chen in 1981 a re examination of the type material and comparing it with other late precambrian frond like forms particularly those from the ediacara assemblage of south australia and from the charnwood assemblage of england indicate that this chinese species represents a distinct genus paracharnia gen nov its characteristic polyp leaves individually free standing on distinct leaf stalks along the lateral sides of the median stem resemble those of many living sea pens represented by pennatula and contribute a significant feature to the precambrian charniidae glaessner 1979 its close association with abundant macroscopic algal remains of vendotaenia sp and its proximity to the overlying basal cambrian small shelly fossil assemblages in the same succession emphasise its palaeontological and biostratigraphic significance

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

application of the ce anomaly as a paleoredox indicator the ground rules much attention has been paid in recent years to the potential application of the ce anomaly measured in various marine phases as a paleoceanographic indicator of widespread marine anoxia in this paper we present and discuss results from recent studies of present day rare earth element ree distributions and hence ce anomaly distributions in the marine environment which are particularly pertinent to paleoceanography subsequently we review and discuss the validity of the recent literature in which ce anomalies have been employed as paleoredox indicators

metabolic activity and diversity of cryoconites in the taylor valley antarctica 1 metabolic activity and biogeochemical diversity within cryoconites from the canada commonwealth howard and hughes glaciers in the mcmurdo dry valleys revealed the presence of a productive microbial refuge in this polar desert ecosystem fluorescent in situ hybridization showed a high percentage of cytophaga flavobacteria cells in cryoconite sediments 87 2 while b proteobacterial cells dominated the ice overlying the sediment layer 54 2 the biomass of bacterial cells in the sediments was also greater 4 82 mgc ml 1 than that in the overlying ice 0 18 mgc ml 1 and was related to bacterial productivity on the basis of thymidine incorporation which ranged from 36 ng cl 1 d 1 in the overlying ice to 3329 ng c l 1 d 1 in the sediment containing layers bacteria within both the sediments and overlying ice were able to actively incorporate and respire radio labeled glucose as well as 17 other dissolved organic carbon compounds the cryoconites in the taylor valley support an active diverse assemblage of organisms despite the fact that they may remain sealed from the atmosphere for decades given the density of the cryoconites in the dry valleys 4 6 of ablation zone surfaces flushing of the cryoconites during warm years could provide a vital nutrient and organic carbon source to the surrounding polar desert

nature genesis and provenance of silt pellets on the ice surface of glacier no 1 upper urumqi river tian shan northwestern china this paper reports silt pellets found at the terminus of the east branch of glacier no 1 tian shan northwestern china these pellets of approximately 1 mm in diameter appeared as layers on glacier surface two pellet samples were collected for microscope examination grain size measurement and geochemical analysis to understand their nature origin and provenance observations of thin sections show that the pellet is comprised of an inner structureless core and an outer concentric thin layer explained by a two stage process a nucleus forming stage and a concentric growth stage the pellet is mainly comprised of poorly sorted 1 7 1 8 silts mean grain grain size 6 2 6 5 with quartz feldspar biotite pyroxenes clay and other minerals the chemical compositions of the silt and clay portions are very similar to that of the upper continental crust ucc except for a few elements e g enrichments of li mo and clay sized particles p zn cu and pb and depletion of ca and silt sized particles bi the pellet materials are derived mainly from atmospheric dusts therefore the silt pellets may provide insights into details of the large scale fine sediment recycling between the atmospheric glacial and alluvial systems

the cryoconite ecosystem on the greenland ice sheet this paper presents an assessment of biological activity associated with ice surface debris cryoconite at the ice sheet scale estimates of the mass distribution of cryoconite over the greenland ice sheet gis and the biological activity associated with it are presented and then coupled with a surface mass balance model to estimate total carbon fluxes due to respiration and photosynthesis we find an average loading of 66 g m 2 at kangerlussuaq southwest greenland which compares well with recent estimates from kronprins christians land 17 440 g m 2 boggild and others 2010 in northeast greenland we also report a significant microbial biomass in cryoconite at both these places 10 3 10 4 cells mg 1 and carbon fluxes of the order of 1 3 m mcg 1 d 1 for both respiration and photosynthesis the modelling indicates that total respiration and photosynthesis fluxes are likely to be 10 1 10 2 gg c a 1 and thus far from trivial however estimation of the net ecosystem impact across the entire ice sheet on atmospheric co2 concentrations is problematic because photosynthesis rates were almost certainly low during our field campaign therefore like its water balance the carbon balance of the gis is now known to be important but its accurate quantification will remain elusive until more data are forthcoming

hydrothermal alteration of the ediacaran doushantuo formation in the yangtze gorges area south china abstract the geochemical and fossil record preserved in the ediacaran age 635 551 ma doushantuo formation of south china has been extensively examined to explore the impact of changing climate and the oxidation state of the oceans on the development and distribution of early multicellular life in the yangtze gorges area this formation shows many of the geochemical trends and features thought to typify global ocean chemistry in the ediacaran period but there are indications that post sedimentary processes modified these signals this study of clay minerals and organic matter builds a more detailed picture of the type and degree of post sedimentary alteration at different stratigraphic levels of the formation and focuses on how this alteration influenced stable carbon and oxygen isotope records in the cratonward jiulongwan and huajipo sections of the doushantuo formation its lower part members 1 and 2 consists largely of dolomitic shale rich in authigenic saponite that crystallized in an alkaline sedimentary basin saponite has been altered to chlorite via corrensite across tens of meters of strata in lower member 2 with increased alteration downward toward the cap dolostone the greater chloritization is accompanied by lower 18 o and higher d values of trioctahedral clays this pattern of alteration of trioctahedral clays is likely due to hydrothermal fluid activity in the underlying relatively permeable nantuo formation and cap dolostone a concomitant increase of solid bitumen reflectance toward the base of the formation supports this idea in the uppermost part of the formation in the yangtze gorges area member 4 a typical open water marine dolomitic shale rich in illite and organic matter increases in the methylphenanthrenes ratio index and solid bitumen reflectance correlate with decrease of the bulk rock k al ratio upward providing evidence for hot fluid migration above the nearly impermeable shale clay from the upper part of the formation is enriched in 18 o but not in d relative to clay from the lower parts indicating progressive 18 o enrichment of hydrothermal fluids that percolated upward and laterally through permeable 18 o rich carbonates a maximum hydrothermal alteration temperature of 200 c is estimated from a calibration curve for illitization during burial diagenesis but given that the hydrothermal activity probably occurred in short pulses the temperature could have been much higher k ar ages are consistent across different size fractions of fine illite from member 4 shale 430 ma and from a k bentonite bed near the base of member 2 in the jiuqunao section 325 ma 25 km from jiulongwan and huajipo these age values show that the diagenetic illite of the doushantuo formation is a product of either deep burial diagenesis overprinted by spatially limited hydrothermal activity or of two localized hydrothermal events patterns of carbonate 13 c and 18 o depletion in the basal doushantuo formation are similar to chloritization trends and 18 o variation in diagenetic clay minerals given independent evidence for 13 c depletion of hydrothermal fluids these trends indicate carbonate fluid isotope exchange commensurate with the degree of post sedimentary alteration supporting a model of lithologically controlled differential diagenesis induced by hydrothermal fluids as the main control on c and o isotope variability in this stratigraphic interval this model could potentially explain other notable 13 c excursions higher up in member 3

rare earth element geochemistry of late devonian reefal carbonates canning basin western australia confirmation of a seawater ree proxy in ancient limestones rare earth element and yttrium ree y concentrations were determined in 49 late devonian reefal carbonates from the lennard shelf canning basin western australia shale normalized sn ree y patterns of the late devonian samples display features consistent with the geochemistry of well oxygenated shallow seawater a variety of different ancient limestone components including microbialites some skeletal carbonates stromatoporoids and cements record seawater like ree y signatures contamination associated with phosphate fe oxides and shale was tested quantitatively and can be discounted as the source of the ree y patterns co occurring carbonate components that presumably precipitated from the same seawater have different relative ree concentrations but consistent ree y patterns clean devonian early marine cements n 3 display ree y signatures most like that of modern open ocean seawater and the highest y ho ratios e g 59 and greatest light ree lree depletion average nd sn yb sn 0 413 sd 0 076 however synsedimentary cements have the lowest ree concentrations e g 405 ppb non contaminated devonian microbialite samples containing a mixture of the calcimicrobe renalcis and micritic thrombolite aggregates in early marine cement n 11 have the highest relative ree concentrations of tested carbonates average total ree 11 3 ppm stromatoporoid skeletons unlike modern corals algae and molluscs also contain well developed seawater like ree patterns samples from an estuarine fringing reef have very different ree y patterns with lree enrichment nd sn yb sn 1 possibly reflecting inclusion of estuarine colloidal material that contained preferentially scavenged lree from a nearby riverine input source hence devonian limestones provide a proxy for marine ree geochemistry and allow the differentiation of co occurring water masses on the ancient lennard shelf although appropriate partition coefficients for quantification of devonian seawater ree concentrations from out data are unknown hypothetical devonian canning basin seawater ree patterns were obtained with coefficients derived from modern natural proxies and experimental values resulting devonian seawater patterns are slightly enriched in lree compared to most modem seawaters and suggest higher overall ree concentrations but are very similar to seawaters from regions with high terrigenous inputs our results suggest that most limestones should record important aspects of the ree geochemistry of the waters in which they precipitated provided they are relatively free of terrigenous contamination and major diagenetic alteration from fluids with high non seawater like ree contents hence we expect that many other ancient limestones will serve as seawater ree proxies and thereby provide information on paleoceanography paleogeography and geochemical evolution of the oceans copyright c 2004 elsevier ltd

petrology and geochemistry of antarctic micrometeorites abstract the petrology and geochemistry of twentythree chondritic dust particles with masses of 1 47 g sizes 100 400 m were recovered from blue ice near cap prudhomme antarctica and studied by inaa asem empa and optical microscopy sample selection criteria were irregular shape and for a subsample black color with the aim of studying as many unmelted micrometeorites mms as possible of thirteen unmelted mms six were phyllosilicate dominated mms and seven were coarsegrained crystalline mms consisting mainly of olivine and pyroxene the remaining ten particles were largely melted and consisted of a foamy melt with variable amounts of relic phases scoriaceous mms thus of the black particles selected an astonishing portion 40 by number consisted of largely unmelted mms although unmelted most phyllosilicate mms have been thermally metamorphosed to a degree that most of the phyllosilicates were destroyed but not melted the original preterrestrial mineralogy is occasionally preserved and consists of serpentine like phyllosilicates with variable amounts of cronstedtite tochilinite like oxides olivine and pyroxene the crystalline mms consist of olivine low ca pyroxene tochilinite like oxides and occasional ni poor metal relics in scoriaceous mms consist of the same phases mineral compositions and the coexistence of phyllosilicates with anhydrous phases are typical of cm and cr type carbonaceous chondrites however the olivine pyroxene ratio 1 and the lack of carbonates sulfates and of very fe poor refractory element rich olivines and pyroxenes sets the mms apart from cm and cr chondrites the bulk chemistry of the phyllosilicate mms is similar to that of cm chondrites however several elements are either depleted ca ni s less commonly na mg and mn or enriched k fe as br rb sb and au in mms as compared to cm chondrites similar depletions and enrichments are also found in the scoriaceous mms we suggest that the depletions are probably due to terrestrial leaching of sulfates and carbonates from unmelted mms the overabundance of some elements may also be due to processes acting during atmospheric passage such as the recondensation of meteoric vapors in the high atmosphere most mms are coated by magnetite of platy or octahedral habit which is rich in mg al si mn and ni we interpret the magnetites to be products of recondensation processes in the high 90 km atmosphere which are therefore probably the first refractory aerominerals identified

diagenetic constraints on the use of cerium anomalies as palaeoseawater redox proxies an isotopic and ree study of cambrian phosphorites seawater rare earth element ree distributions show heavy ree enrichment and cerium depletion but these characteristics are only rarely found in ancient marine authigenic minerals such as carbonate fluorapatite and calcite this enigma may be due to changing ree distributions in seawater through time or to post depositional redistribution of ree differentiating between these two factors is however far from straightforward as their relative importance is likely to vary and evidence is often ambiguous in this article we present ree as well as strontium and sulphur isotope data for basal cambrian phosphorites of south china which confirm the emerging rule of thumb that granular phosphorites seldom reveal extreme departures from the seawater norm and tend to undergo therefore less diagenetic alteration of ree spectra than skeletal apatites and other phosphate types this study reveals stratigraphic trends in ce anomalies ce ce that could be taken to imply the preservation of a palaeoenvironmental signal however further investigation of our data shows that such trends in phosphorites can also be caused by post depositional alteration which tends to 1 increase ree contents 2 reverse ce depletion 3 alter eu anomalies and 4 concentrate preferentially the middle ree mree further alteration which may be due to weathering has led to hree depletion and positive la and y anomalies tetrad effect this is the first study where ceanom and phosphate bound sulphate s isotope values could be compared for one particular stratigraphic section which provides us with an additional tool for the interpretation of diagenetic redox conditions least altered phosphorites from meishucun that yield a strongly negative ceanom constrain early cambrian seawater 34s to about 33 we conclude that phosphorite ceanom primarily records variations in the local conditions of diagenesis while outlining some special cases in which diagenetic redox conditions may broadly reflect local bottom water redox conditions

sediments in arctic sea ice implications for entrainment transport and release despite the arctic sea ice cover s recognized sensitivity to environmental change the role of sediment inclusions in lowering ice albedo and affecting ice ablation is poorly understood sea ice sediment inclusions were studied in the central arctic ocean during the arctic 91 expedition and in the laptev sea east siberian arctic region expedition 1992 results from these investigations are here combined with previous studies performed in major areas of ice ablation and the southern central arctic ocean this study documents the regional distribution and composition of particle laden ice investigates and evaluates processes by which sediment is incorporated into the ice cover and identifies transport paths and probable depositional centers for the released sediment in april 1992 sea ice in the laptev sea was relatively clean the sediment occasionally observed was distributed diffusely over the entire ice column forming turbid ice observations indicate that frazil and anchor ice formation occurring in a large coastal polynya provide a main mechanism for sediment entrainment in the central arctic ocean sediments are concentrated in layers within or at the surface of ice floes due to melting and refreezing processes the surface sediment accumulation in central arctic multi year sea ice exceeds by far the amounts observed in first year ice from the laptev sea in april 1992 sea ice sediments are generally fine grained although coarse sediments and stones up to 5 cm in diameter are observed component analysis indicates that quartz and clay minerals are the main terrigenous sediment particles the biogenous components namely shells of pelecypods and benthic foraminiferal tests point to a shallow benthic marine source area apparently sediment inclusions were resuspended from shelf areas before and incorporated into the sea ice by suspension freezing clay mineralogy of ice rafted sediments provides information on potential source areas a smectite maximum in sea ice sediment samples repeatedly occurred between 81 n and 83 n along the arctic 91 transect indicating a rather stable and narrow smectite rich ice drift stream of the transpolar drift the smectite concentrations are comparable to those found in both laptev sea shelf sediments and anchor ice sediments pointing to this sea as a potential source area for sea ice sediments in the central arctic ocean sea ice clay mineralogy is significantly different from deep sea clay mineral distribution patterns the contribution of sea ice sediments to the deep sea is apparently diluted by sedimentary material provided by other transport mechanisms

the ablation zone in northeast greenland ice types albedos and impurities ice types albedos and impurity content are characterized for the ablation zone of the greenland ice sheet in kronprinz christians land 80 n 24 w along this ice margin the width of the ablation zone is only about 8 km the emergence and melting of old ice in the ablation zone creates a surface layer of dust that was originally deposited with snowfall high on the ice sheet this debris cover is augmented by locally derived wind blown sediment subsequently the surface dust particles often aggregate together to form centimetre scale clumps that melt into the ice creating cryoconite holes the debris in the cryoconite holes becomes hidden from sunlight raising the area averaged albedo relative to surfaces with uniform debris cover spectral and broadband albedos were obtained for snow ice hummocks debris covered ice cryoconite studded ice and barren tundra surfaces broadband ice albedos varied from 0 2 for ice with heavy loading of uniform debris to 0 6 for ice hummocks with cryoconite holes the cryoconite material itself has albedo 0 1 when wet areal distribution of the major surface types was estimated visually from a transect video as a function of distance from the ice edge 330 m a s l ablation rates were measured along a transect from the ice margin to the slush zone 8 km from the margin 550 m a s l traversing both pleistocene and holocene ice ablation rates in early august averaged 2 cm d 1 impurity concentrations were typically 4 3 mg l 1 in the subsurface ice surface concentrations were about 16 g m 2 on surfaces with low impurity loading and heavily loaded surfaces had concentrations as high as 1 4 kg m 2 the mineralogical composition of the cryoconite material is comparable with that of the surrounding soils and with dust on a snowdrift in front of the ice margin implying that much of the material is derived from local sources a fine mode clay is present in the oldest ice but not in the nearby soil suggesting that its origin is from wind deposition during pleistocene glaciation

a 3 800 million year isotopic record of life from carbon in sedimentary rocks an increased ratio of 12c to 13c an indicator of the principal carbon fixing reaction of photosynthesis is found in sedimentary organic matter dating back to almost four thousand million years ago a sign of prolific microbial life not long after the earth s formation partial biological control of the terrestrial carbon cycle must have been established very early and was in full operation when the oldest sediments were formed

a snow algal community on akkem glacier in the russian altai mountains snow algae are cold tolerant algae growing on snow and ice and have been reported on glaciers in many parts of the world blooms of snow algae can reduce the surface albedo of snow and ice and significantly affect their melting in addition snow algae found in ice cores can be potential indicators of the paleo environment making them of great interest both to the biology and the geophysics of glaciers a snow algal community was investigated in 2002 and 2003 on akkem glacier in the russian altai mountains where no information on its biological community has previously been available five species of snow algae including green algae and cyanobacteria were observed on the glacier red snow due to a bloom of algae chloromonas sp was visually apparent in the snow area during our study periods the total algal cell volume biomass on the glacier ranged from 97 to 1156 m lm 2 which is equivalent to that reported previously on glaciers in the himalaya and alaska the community structure showed that mesotaenium berggrenii and or ancylonema nordenskioeldii which are common species on glaciers in the northern hemisphere were dominant in the ice area while chloromonas sp was dominant in the snow area such community structures are similar to those on alaskan and arctic glaciers but differ from those on himalayan and tibetan glaciers even though the altai mountains are geographically closer to the himalaya and tibet than to alaska the difference in algal communities between the altaic and other glaciers is discussed together with physical and chemical conditions affecting the algae

the microstructure and biogeochemistry of arctic cryoconite granules a cryoconite granule is a biologically active aggregation of microorganisms mineral particles and organic matter found on glacier surfaces often within shallow pools or cryoconite holes observations of the microstructure of a range of cryoconite granules from locations in svalbard and greenland reveal their structure and composition whereas bulk analyses show that the mineralogy and geochemistry of these granules are broadly similar analyses of their microstructure using optical epifluorescence and confocal microscopy indicate differences in the location and quantity of photosynthetic microorganisms heterotrophic bacteria and organic matter using these findings a hypothesis on the aggregation of cryoconite is presented centred upon multilevel aggregation by bioflocculation and filamentous binding

ediacaran fossil preservation taphonomy and diagenesis of a discoid biota from the amadeus basin central australia abstract aspects of the preservation of the enigmatic soft bodied ediacara biota in relatively coarse grained siliciclastic sediments remain unresolved the taphonomic model proposed by gehling in 1999 is here validated through examination of previously unpublished discoid fossils from the shallow marine deltaic arumbera sandstone in the amadeus basin within the flinders style preservation the model predicts stalked frondose organisms attached by a discoid holdfast to a microbial mat encrusted sea bed with sedimentation as periodic storm event beds during a terminal neoproterozoic taphonomic window a pyrite sole veneer provided critical fossil rigidity during burial the sequence of sedimentation events presented here advances a slightly modified gehling model no direct evidence of pyrite is detected instead a thin haematite clay coating covers fossil hyporelief surfaces nevertheless an original pyrite sole veneer is indirectly validated by tracing its diagenetic history through to today s haematite detailed petrography demonstrates reducing conditions during eodiagenesis that remained anoxic mildly alkaline through mesodiagenesis thus the pyrite sole veneer survived deepest burial meteoric water penetrated the deep regolith during prolonged telodiagenesis creating oxic mildly acidic pore water so pyrite oxidised and hydrolised to haematite the applicability of gehling s model is higher where marine shelf sediments subsided continuously in shallower or eroded areas that experienced intermittent meteoric eodiagenesis diagenetic history was different and ediacaran fossil preservation unlikely diagenetic history therefore has crucial implications for ediacaran fossil preservation

trace fossil evidence for ediacaran bilaterian animals with complex behaviors abstract distinguishing ediacaran trace fossils from tubular body fossils can be a challenge and several ediacaran fossils previously interpreted as animal traces have been shown to be tubular body fossils nonetheless true ediacaran trace fossils are present but they are relatively few and morphologically simple dominated by horizontal trails and shallow burrows such simple morphologies have been taken as evidence for a modest behavioral complexity and limited geobiological impact of animal bioturbators before the cambrian explosion here we report three types of trace fossils horizontal tunnels surface tracks trails and vertical traces from the latest ediacaran dengying formation 551 541 ma in the yangtze gorges area of south china cross cutting tunnels and the presence of scratch marks indicate that these traces are unlikely tubular body fossils instead these three types of traces likely represent animal activities related to under mat feeding epibenthic locomotion and temporary dwelling respectively we show that these three types of traces were constructed by the same bilaterian animals that had moderately complex interactions with microbial mats to exploit nutrients and o 2 resources these animals heralded a new age in ecosystem engineering animal sediment interaction and biogeochemical cycling

correlation of spectral accelerations for earthquakes in china abstract conditional mean spectrum cms is increasingly being accepted as a more reasonable target spectrum for selecting earthquake records than uniform hazard spectrum construction of cms requires the determination of correlation coefficients of spectral accelerations this article presents the first investigation of correlation coefficients based on earthquake records from china first an original methodology to verify the appropriateness of a ground motion prediction equation gmpe to determine correlation coefficients is proposed and illustrated considering seismic hazard in china a dataset of ground motions recorded from 2007 to 2014 in china with magnitudes ranging from m s 5 5 to 7 0 and epicentral distances less than 200 km is then selected and analyzed to obtain correlation coefficients based on a newly developed gmpe the obtained results indicate the same trends as the prediction model proposed by baker and jayaram 2008 based on next generation attenuation west ground motions and gmpes the sensitivity of correlation coefficients to magnitude is also verified and the obtained results are provided in comprehensive tables the results of this work provide the essential data required to develop cms considering seismic hazard in china

structural characterization of kerogen in 3 4 ga archaean cherts from the pilbara craton western australia hydrogen lean kerogen atomic h c 0 46 isolated from the 3 4 ga strelley pool chert in the north pole area pilbara craton western australia were studied by vibrational spectroscopy fourier transform infrared ftir spectroscopy and raman spectroscopy nuclear magnetic resonance spectroscopy solid state 13 c nmr spectroscopy catalytic hydropyrolysis followed by gas chromatography mass spectrometry hypy gc ms and isotope ratio mass spectrometry irms the kerogen occurs in sedimentary rocks as clasts and clots deposited together with other detrital materials that are finely disseminated throughout a chert matrix the bulk kerogen 13 c values range from 28 3 to 35 8 solid state 13 c nmr spectroscopy and ftir spectroscopy reveals that the kerogen is highly aromatic fa varying from 0 90 to 0 92 and contains only minor aliphatic carbon or carbon oxygenated c o functionalities the raman carbon first order spectra for the isolated kerogens are typical of spectra obtained from disordered sp 2 carbons with low 2 d ordering biperiodic structure the implications of the raman results show low 2 d ordering throughout the carbonaceous network indicate the incorrect usage of the term graphite in the literature to describe the kerogen or carbonaceous material in the warrawoona cherts hydropyrolysates contain aromatic compounds consisting of 1 ring to 7 ring polycyclic aromatic hydrocarbons which were covalently bound into the kerogen as well as alkanes linear branched and cyclic which were most probably trapped in the microporous network of the kerogen these pahs have mainly c1 and c2 alkylation while c3 substitued aromatics are low in abundance and do not show a high degree of branched alkylation for the first time we have shown a correlation between elemental analysis h c atomic ratios raman spectroscopic parameters id1 ig id1 id1 ig and la and the degree of alkylation of bound polyaromatic molecular constituents generated from hypy for archaean kerogens similarities in molecular

crystal chemical controls on rare earth element concentrations in fossil biogenic apatites and implications for paleoenvironmental reconstructions abstract fossil biogenic apatites display rare earth element ree patterns which have been proposed to reflect environmental and biological controls on past seawater composition these patterns can be separated in two groups 1 patterns that are similar to those of open ocean and epicontinental waters and 2 patterns that exhibit a strong enrichment in intermediate ree bell shaped patterns because ree trapping in biogenic apatites occurs mostly post mortem it is essential to understand the crystal chemical inorganic factors that can influence the fractionation of ree between apatite and water a model is proposed by which partition coefficients of ree between apatite and water for a substitution mechanism can be extrapolated from mineral melt partition data to seawater or sedimentary basin conditions these are compared with available experimental partition coefficients for ree adsorption mechanism and used to discuss ree patterns in fossil biogenic apatites calculations of ree patterns for apatites at equilibrium with water show that the bell shaped patterns in fossil apatites can be explained by fractionation with seawater or continental fluids at low temperature under crystal chemical control involving a substitution mechanism and in the context of extensive or late diagenesis in that case the equilibrium composition of the fluid cannot be unequivocally determined from observed ree concentrations in fossil apatites this type of sample is inappropriate to discuss the past environmental or biological controls on ree concentrations in the ocean other sample compositions suggest little to moderate alteration of the original oceanic to freshwater pattern through the adsorption mechanism in the context of weak or early diagenesis and may be used with caution for that purpose

remarkable preservation of microbial mats in neoproterozoic siliciclastic settings implications for ediacaran taphonomic models abstract it is beyond doubt that the appearance of infaunal bioturbation and metazoan biomineralization across the ediacaran cambrian transition irreversibly affected the nature of marine sediment architecture and biogeochemistry here we review those changes in relation to their likely effect upon the processes of fossil preservation especially within siliciclastic sediments processes of soft tissue preservation in siliciclastic settings from the ediacaran period including microbes and microbial mats as well as ediacaran macrofossils are here reviewed within this context highlighted examples include the exceptional preservation of microbes found in association with wrinkle structures and ediacaran macrofossils in england and newfoundland replicated by silicate minerals and in the white sea region of russia replicated by iron sulphide these occurrences show that soft tissue preservation in siliciclastic settings went well beyond that typical for ediacaran macrofossils alone and also extended to similar modes of preservation in associated microbes using these new observations it can be argued that several existing explanations for ediacaran fossil preservation can be united within a biogeochemical model that involves evolution of the sediment mixed layer across this transition

assessing biomarker syngeneity using branched alkanes with quaternary carbon baqcs and other plastic contaminants biomarker molecules are valuable for the elucidation of ancient microbial ecosystems and the characterization of petroleum source rocks for such studies acquisition of reliable hydrocarbon data and proof of their syngeneity are essential however contamination of geological samples with anthropogenic petroleum products during drilling storage and sampling can be particularly problematic because these hydrocarbons may over print an original indigenous biomarker profile to evaluate the extent of contamination of drill core and outcrop material we studied the distribution of hydrocarbons in 26 rocks from different locations in the world all rocks had petroleum products on their exterior surfaces twenty two samples also contained surficial hydrocarbons derived from polyethylene plastic including branched alkanes with quaternary carbon centers baqcs and alkylcyclopentanes with pronounced even over odd carbon number preference using three examples from the paleoproterozoic tawallah and mcarthur groups in northern australia we show how indigenous biomarkers can be recognized by comparing hydrocarbon distributions between exterior rock surfaces and the rock interior and how infiltration of allochthonous hydrocarbons can be assessed through the spatial distribution of characteristic polyethylene derived hydrocarbons in the rock the methods outlined in this paper give confidence in the interpretation of biomarkers in particularly sensitive applications such as the first occurrences of certain organisms in the geological record and the provenance of organic matter in meteorites

interactions between ediacaran animals and microbial mats insights from lamonte trevallis a new trace fossil from the dengying formation of south china abstract a new ichnogenus and ichnospecies lamonte trevallis is formally described from the shibantan member limestone of the upper ediacaran dengying formation yangtze gorges area south china it is characterized by horizontal tunnels connected with short vertical burrows and surface trails the horizontal burrows are elliptical or bilobed in transverse cross section preserved in full relief and filled with carbonate intraclasts micrites as well as calcite and silica cements they occur exclusively in silty crinkled and microlaminated layers that are interpreted as amalgamated cyanobacterial microbial mats no burrows have been found in intraclastic layers adjacent to the microlaminated layers the vertical traces are filled with the same material as the burrows but they typically project through the crinkled microlaminae and are exposed on the bedding surface the surface tracks are always preserved in negative epirelief or positive hyporelief and consist of two parallel series of either sharp scratch marks or small knobs the burrow infill has 18ocarb and 13ccarb values distinct from but intermediate between microlaminated and intraclastic layers consistent with petrographic observation that burrow infill consists of a mixture of early carbonate cements intraclasts and micrites bedding plane bioturbation intensity 20 40 measured as percentage of bedding plane area covered by l trevallis traces is comparable to similar measurements in pre trilobite cambrian carbonates the exclusive occurrence of l trevallis within microbial mats may have both taphonomic and ecological significance these mats may have provided firm substrates and localized geochemical conditions that contributed to the structural integrity of the burrows and they may have also facilitated early diagenetic cementation of burrow infill thus facilitating burrow preservation the close association of these burrows with microbial mats implies that the trace producers actively mined cyanobacterial mats to exploit oxygen or nutrient resources the trace makers of l trevallis were better able to utilize the resources around them than many other ediacaran trace makers and provide an ichnological record of a flourishing benthic ecology in late ediacaran oceans at the dawn of the agronomic revolution

comparative analysis of morphological mineralogical and spectral properties of cryoconite in jakobshavn isbrae greenland and canada glacier antarctica we report the results of a comparative analysis focusing on grain size mineralogical composition and spectral reflectance values 400 2500nm of cryoconite samples collected from jakobshavn isbrae west greenland and canada glacier mcmurdo dry valleys antarctica the samples from the greenland site were composed of small particles clumped into larger rounded agglomerates while those from the site in antarctica contained fragments of different sizes and shapes mineralogical analysis indicates that the samples from jakobshavn isbrae contained a higher percentage of quartz and albite whereas those from canada glacier contained a higher percentage of amphibole augite and biotite spectral measurements confirmed the primary role of organic material in reducing the reflectance over the measured spectrum the reflectance of the samples from the antarctic site remained low after the removal of organic matter because of the higher concentration of minerals with low reflectance the reflectance of dried cryoconite samples in the visible region was relatively low e g between 0 1 and 0 4 favouring increased absorbed solar radiation despite high reflectance values in the shortwave infrared region the effect of the presence of cryoconite is negligible at infrared wavelengths where ice reflectance is low

optical characteristics of cryoconite surface dust on glaciers the relationship between light absorbency and the property of organic matter contained in the cryoconite

integrated ediacaran sinian chronostratigraphy of south china abstract the ediacaran period was a critical time in the history of life and earth understanding the complex interactions between geological and biological events during this interval requires high resolution chronostratigraphy thanks to its uniquely favorable palaeogeographic setting south china is an ideal region for constructing a framework for global chronostratigraphic correlation of ediacaran strata here continuous ediacaran successions contain both siliciclastic and carbonate rocks that range from shallow to deep marine and contain rich fossil assemblages showing a variety of preservation styles as part of the present study 62 reference sections distributed throughout the yangtze platform were investigated analyses of the sedimentary facies and sequence stratigraphy of more than 40 sections revealed four major sequences in the shallow marine facies three major sequence boundaries occur respectively in the middle and upper parts of the doushantuo formation and in the middle part of the dengying formation subdivision and correlation of the ediacaran successions of the yangtze platform based on sequence stratigraphy is congruent with the carbon isotope chemostratigraphy of 12 reference sections 1075 samples the sequence boundary sb2 in the middle part of the doushantuo formation is suggested here as the lower xiadongian upper yangtzean series boundary of the ediacaran which coincides with several globally recognizable events namely 1 the end of the neoproterozoic glaciations 2 the first appearance of animals 3 the sudden increase in the diversity of acanthomorphic acritarchs and 4 a negative 13 c excursion the ediacaran system of south china may be subdivided into five stages furthermore the criteria for defining these stages may be applicable throughout the world also the composite carbon isotope profile of the ediacaran of south china can be used as a global reference for chronostratigraphic subdivision and correlation in addition to the globally recognizable negative 13 c excursion in the cap carbonate at the base of the ediacaran the negative 13 c excursion in the uppermost doushantuo wonoka shuram interval represents another globally correlatable major excursion the positive 13 c excursion immediately following the uppermost doushantuo excursion and ending at 548 ma is also useful for global correlation current ediacaran chronostratigraphy and global correlations indicate that the upper doushantuo wonoka shuram negative 13 c excursion ranges from ca 560 ma to 551 ma and therefore coincides with the evolutionary renovation of life feedback between evolutionary innovation and geochemical cycling was the key mechanism for this unique and most strongly negative 13 c excursion in earth history our chronostratigraphic correlations also imply that the earliest known metazoan biotas namely the weng an and characteristic ediacaran biotas do not constitute two temporally separate evolutionary lineages as proposed previously but represent two parallel evolutionary pathways preceding the cambrian explosion of animal life

the ratios of dibenzothiophene to phenanthrene and pristane to phytane as indicators of depositional environment and lithology of petroleum source rocks abstract the ratio of dibenzothiophene to phenanthrene and the ratio of pristane to phytane when coupled together provide a novel and convenient way to infer crude oil source rock depositional environments and lithologies such knowledge can significantly assist in identifying the source formation s in a basin thereby providing valuable guidance for further exploration the ability to infer this information from analysis of a crude oil is especially valuable as frequently the earliest samples in a new area may be shows and or drill stem test samples from exploratory wells which are characteristically drilled on structural highs stratigraphically remote from the source formation s a cross plot of dibenzothiophene phenanthrene versus the pristane phytane ratios measured on seventy five crude oils from forty one known source rocks ranging in age from ordovician to miocene consistently classified the oils into the following environment lithology groups marine carbonate marine carbonate mixed and lacustrine sulfate rich lacustrine sulfate poor marine and lacustrine shale and fluvial deltaic carbonaceous shale and coal the dibenzothiophene phenanthrene ratio alone is an excellent indicator of source rock lithology with carbonates having ratios 1 and shales having ratios the dibenzothiophene to phenanthrene and the pristane to phytane ratios can also be used to classify source rock paleodepositional environments the classification scheme is based on the premise that these ratios reflect the different eh ph regimes resulting from the significant microbiological and chemical processes occurring during deposition and early diagenesis of sediments the dibenzothiophene phenanthrene ratio assesses the availability of reduced sulfur for incorporation into organic matter and the pristane phytane ratio assesses the redox conditions within the depositional environment interpretation of these ratios has been aided by quantitative biomarker analysis and by carbon isotope data for pristane and phytane obtained by gas chromatography isotope ratio mass spectrometry

extreme hydrochemical conditions in natural microcosms entombed within antarctic ice cryoconite holes are near vertical tubes that form in the surface of glaciers when solar heated debris melts into the ice those that form in the mcmurdo dry valleys of antarctica are distinctive in that they have ice lids and are closed to the atmosphere for periods of years to decades photoautotrophs and heterotrophs grow within this closed environment perturbing the poorly buffered water chemistry yet maintaining the potential for photosynthesis microbial excretion and decomposition of organic matter produces dissolved organic carbon doc dissolved inorganic carbon ratios of 1 2 much of the dissolved nitrogen pool 80 100 exists as dissolved organic nitrogen don the don doc ratio is 1 11 mol mol typical of organic particulate material at the earth s surface the combination of photoautotrophy heterotrophy and weak chemical buffering within these microcosms promotes values of ph pco2 o2 saturation and percentage total dissolved nitrogen as don that reach 10 99 10 7 6 atm 160 and 100 respectively which are a unique combination among the surface waters on earth these ice sealed cryoconite holes could be important analogues of refugia on snowball earth and other icy planets

cerium anomaly variations in ediacaran earliest cambrian carbonates from the yangtze gorges area south china implications for oxygenation of coeval shallow seawater abstract the late neoproterozoic ocean witnessed the naissance of animals which is believed to have been stimulated by an increase in oxygen levels in the ocean however apart from the emergence of animal fossils little supporting evidence has been found for the rise of oxygen in shallow seawater here we present ce anomaly data a redox proxy with a higher reduction potential than many other redox proxies for carbonates from well preserved marine successions the doushantuo formation dengying formation and lower yanjiahe formation of the ediacaran period and the upper yanjiahe formation of early cambrian on the neoproterozoic yangtze platform in the yangtze gorges area in order to constrain the redox evolution of the shallow marine environment calculated ce anomalies were screened using the following criteria al 36 in acetic acid leached carbonate to target samples that preserve primary seawater ree features and ce anomalies the samples satisfying this screening show seawater like ree distribution patterns in leached carbonates and may have recorded ce anomalies of the seawater from which the carbonates precipitated these data show that the doushantuo formation has ce ce values between 0 92 and 0 71 the dengying formation between 0 90 and 0 40 and the yanjiahe formation between 0 52 and 0 72 the ce ce values of the doushantuo formation suggest that shallow waters during the doushantuo stage 635 551 ma were anoxic to suboxic from the bottom to the top of the dengying formation ce ce values decrease systematically which cannot be explained by a change in depositional depth of the carbonate but suggests that the shallow waters became more oxygenated during the dengying stages from 551 ma to ediacaran cambrian boundary these results may provide direct evidence for an increase in oxygen levels in the shallow marine environment during the ediacaran period

precambrian cambrian trace fossils from the yangtze platform south china and the early evolution of bilaterian lifestyles abstract siliciclastic carbonaceous and phosphoritic shallow marine sediments from several neoproterozoic ediacaran and precambrian cambrian pc c boundary sections on the yangtze platform south china contain remarkable trace fossil assemblages the present paper provides a general overview on the distribution and the possible palaeobiological and palaeoenvironmental significance of these trace fossil assemblages from selected pc c boundary sections on the passive yangtze platform margins comparative investigations of the typology of neoproterozoic ediacaran ichnofaunas as well as of the related sedimentary environments accompanying the ichnoassemblages demonstrate in general correspondence with other studies worldwide that the neoproterozoic ichnofaunas are mainly composed of slightly curved to straight and unbranched horizontal traces which are usually related to the occurrence of shallow marine softgrounds sealed by microbial mats rare traces show ichnomorphological patterns that indicate developments toward a more effective horizontal exploitation of the feeding ground during the late neoproterozoic and earliest cambrian the majority of these traces appear to represent undermat miners with simple feeding strategies during the earliest phanerozoic early meishucunian stage equivalent to the nemakit daldynian stage of siberia the oxic shallow water environments along the ancient continental passive margins of the yangtze platform were populated by large as yet unknown arthropods which produced rusophycus type trace fossils the late precambrian to early phanerozoic sediments of the yangtze platform generally provide excellently preserved trace fossil records which together with the presence of index fossils ssf from the nemakit daldynian stage provide a more detailed insight into the development of pc c palaeoenvironments and the evolution of lifestyles among early bilaterian metazoans a preliminary comparison of the neoproterozic biotas occurring on the yangtze platform and in other time equivalent ediacaran habitats demonstrates general similarities but also some striking differences probably due to palaeoenvironmental variations the data presented here from south china are critically discussed in the light of current palichnological approaches and theories

geobiology of a palaeoecosystem with ediacara type fossils the shibantan member dengying formation south china abstract despite the importance of palaeoecosystems with ediacara type fossils for the early evolution of metazoans only little is known about the interplay of geological and biological processes in these environments the reason is that sedimentary structures biogenic structures and bio geochemical signatures e g hydrocarbon biomarkers are commonly not well preserved due to the predominance of volcanic and siliciclastic lithologies the shibantan member dengying formation south china is one of only few carbonate settings with ediacara type organisms worldwide and its lithology promises an excellent preservation of sedimentary facies and bio geochemical signatures here we provide the first comprehensive geobiological characterisation of the shibantan member in order to reconstruct the interplay between sedimentary and bio geochemical processes and to assess the microbial activities in the palaeoecosystem with ediacara type fossils facies analyses revealed that carbonate and organic matter were autochthonously formed by bio geochemical processes linked to microbial mats however the material was frequently reworked and re deposited within the same setting i e para autochthonous as evidenced by small scale hummocky cross stratification erosional contacts lenticular bedding and load casts negative ce anomalies ce ce and low v cr ratios demonstrate that molecular o 2 was present in the water column whereas characteristic ni co v v ni and v sc ratios suggest the contemporaneous presence of sub to anoxic water taken together these observations imply a temporarily stratified water body frequently mixed and ventilated by storms 13 c enrichments in the shibantan carbonates 13 c 3 29 to 3 98 vpdb together with 13 c depletions of syngenetic n alkanes cleaved from the extraction residue using catalytic hydropyrolysis hypy 13 c 31 7 to 36 3 vpdb could indicate a significant withdrawal of 12 c by primary producers that thrived within the mats at the same time sulphurised biomarkers in the bitumen and hypy pyrolysate hint at organic matter decomposition and concomitant sulphide production by sulphate reducing bacteria when oxygen was available at the sediment water interface due to mixing by storms sulphide oxidising bacteria were possibly temporarily favoured the results demonstrated that palaeoenvironmental conditions dynamically changed through a complex interplay of biogenic and abiogenic processes

viral dynamics in cryoconite holes on a high arctic glacier svalbard 1 viruses are an abundant and dynamic constituent of microbial communities in aquatic ecosystems in this study we characterized the abundance of viruses associated first with the bottom sediment and overlying water of cryoconite holes and second with shallow ice cores of two different glaciers in svalbard viral abundances were ca 10 100 times lower than the average for marine and freshwater ecosystems in temperate regions virus to bacterium ratios vbr average 10 range between 0 7 and 74 in the water and ice samples and a strong positive correlation between viral and bacterial abundance r 0 93 p 0 01 n 57 indicate that viruses most probably play an important role in controlling bacterial mortality and hence biogeochemical cycling on glaciers samples taken along a transect from the glacier ablation area to proglacial ponds in its forefield showed that viral abundance increased in response to a higher host availability which in turn probably resulted from an increase in temperature and higher mineral levels in the ponds in a transplantation experiment viruses from cryoconite holes were incubated with a bacterial community from a proglacial lake results from the transplantation experiment showed that viruses from cryoconite holes were able to infect bacteria from proglacial lakes and thus influence biogeochemical cycles across different glacial ecosystems our data therefore suggest that viruses in cryoconite holes may be able to infect a broad range of bacterial species

effects of debris on ice surface melting rates an experimental study here we report a laboratory study of the effects of debris thickness diurnally cyclic radiation and rainfall on melt rates beneath rock avalanche debris and sand representing typical highly permeable supraglacial debris under continuous steady state radiation sand cover 50mm thick delays the onset of ice surface melting by 12 hours but subsequent melting matches melt rates of a bare ice surface only when diurnal cycles of radiation are imposed does the debris reduce the longterm rate of ice melt beneath it this is because debris 50 mm thick never reaches a steady state heat flux and heat acquired during the light part of the cycle is partially dissipated to the atmosphere during the nocturnal part of the cycle thereby continuously reducing total heat flux to the ice surface underneath the thicker the debris the greater this effect rain advects heat from high permeability supraglacial debris to the ice surface thereby increasing ablation where thin highly porous material covers the ice in contrast low permeability rock avalanche material slows water percolation and heat transfer through the debris can cease when interstitial water freezes during the cold night part of the cycle this frozen interstitial water blocks heat advection to the ice debris contact during the warm day part of the cycle thereby reducing overall ablation the presence of metre deep rock avalanche debris over much of the ablation zone of a glacier can significantly affect the mass balance and thus the motion of a glacier the length and thermal intensity of the diurnal cycle are important controls on ablation and thus both geographical location and altitude significantly affect the impact of debris on glacial melting rates the effect of debris cover is magnified at high altitude and in lower latitudes copyright 2010 elsevier b v all rights reserved

temporal and spatial variations in spectral reflectance and characteristics of surface dust on gulkana glacier alaska range spectral reflectances in the visible to near infrared wavelength range 350 1050 nm were measured on the surface of gulkana glacier alaska range alaska usa at six different elevations from may to september 2001 the measurements showed variable spectral reflectances on the glacier surface and the spectra changed over time and elevation the spectra in may were those of a typical wet snow surface the reflectance ranged approximately from 0 4 to 0 8 and generally decreased as the wavelength increased as snowmelt proceeded the reflectance gradually fell and specific absorptions appeared in the spectrum at wavelength ranges of 400 600 and 670 680 nm corresponding to a red snow surface due to snow algal bloom as the ice surface was exposed the spectrum finally shifted to a lower 0 1 0 4 and flat reflectance curve typical of an ice surface contaminated with dust analyses of the dust on the glacier surface showed that its quantity and characteristics changed spatially and seasonally and were correlated with spectral albedo the results showed that the temporal and spatial variations in spectral reflectance on this glacier are due not only to physical properties of the glacier surface but also to biogenic materials on the surface e g red colored snow algal cells and cryoconite

rapid quantification of cryoconite granule geometry and in situ supraglacial extents using examples from svalbard and greenland supraglacial dust cryoconite is an important but poorly understood component of the glacial system there is a lack of primary data on cryoconite form extent and dynamics here we present a suite of rapid low cost methodologies for quantification of granule geometry and supraglacial cryoconite coverage using image data captured by commercially available digital cameras we develop robust transferable protocols for analysis of 1 cryoconite granule geometry major axis feret diameter circularity 2 centimetre metre scale supraglacial extent m2 cryoconite m 2 surface and 3 temporal change in supraglacial extent at hourly intervals over several days image processing methodologies were developed using the public domain software imagej manual supervised controls were used to estimate sources of error and measurements then automated using simple scripting tools macros fully automated processing successfully identified 90 of a sample of isolated granules ranging between 2 5 and 39 2 mm with uncertainties of 20 particle sphericity inferred from circularity decreased as particle size increased supraglacial cryoconite extent was obtained with a mean uncertainty of 37 and 22 for data from field sites in greenland and svalbard respectively these methods will facilitate acquisition and analysis of datasets for cryoconite across a range of spatial scales supporting research into cryoconite impacts on supraglacial hydrological connections nutrient and carbon cycling and initiation of primary succession in deglaciating environments

a monte carlo approach to seismic hazard analysis abstract we have developed a monte carlo methodology for the estimation of seismic hazard at a site or across an area this method uses a multitudinous resampling of an earthquake catalog perhaps supplemented by parametric models to construct synthetic earthquake catalogs and then to find earthquake ground motions from which the hazard values are found large earthquakes extrapolated from a gutenberg richter recurrence relation and characteristic earthquakes can be included in the analysis for the ground motion attenuation with distance the method can use either a set of observed ground motion observations from which estimates are randomly selected a table of ground motion values as a function of epicentral distance and magnitude or a parametric ground motion attenuation relation the method has been tested for sites in new england using an earthquake catalog for the northeastern united states and southeastern canada and it yields reasonable ground motions at standard seismic hazard values this is true both when published ground motion attenuation relations and when a dataset of observed peak acceleration observations are used to compute the ground motion attenuation with distance the hazard values depend to some extent on the duration of the synthetic catalog and the specific ground motion attenuation used and the uncertainty in the ground motions increases with decreasing hazard probability the program gives peak accelerations that are comparable to those of the 1996 u s national seismic hazard maps the method can be adapted to compute seismic hazard for cases where there are temporal or spatial variations in earthquake occurrence rates or source parameters

biogeochemical evolution of cryoconite holes on canada glacier taylor valley antarctica 1 the cryoconite holes of the mcmurdo dry valleys are simple closed biogeochemical systems involving water ice mineral and organic debris which serve as ecosystems for consortia of microorganisms this study is the first to document the seasonal and annual chemical evolution of solutes in cryoconite holes samples of glacier ice frozen cryoconite holes and those containing water were collected during the austral summer of 2005 2006 the isolation age was calculated from the excess cl in the holes and varied from 0 to 5 years a consistent with the last hot summer when the cryoconite holes were open to the atmosphere the holes progressively deepen with isolation age variations in dic doc k and so42 suggest that dissolution of primary minerals in the cryoconite debris cyclical precipitation and dissolution of secondary carbonates net photosynthesis over summer and net respiration during the autumnal freeze are the principal reactions which perturb the seasonal and annual solute concentrations in the holes doc is generated in the holes at a rate of 7 5 g c cm 2 a 1 and non sea salt k accumulates in frozen holes at a rate of 0 073 eq cm 2 a 1 we infer that c cycling is complex even in these otherwise simple systems

relationship between inferred redox potential of the depositional environment and geochemistry of the upper pennsylvanian missourian stark shale member of the dennis limestone wabaunsee county kansas u s a analyses of 21 samples collected from a core of the 52 8 cm thick stark shale member of the dennis limestone in wabaunsee county kansas demonstrate four cycles with two orders of magnitude variations in contents of cd mo p v and zn and order of magnitude variations in contents of organic carbon cr ni se and u the observed variability in amounts and or ratios of many metals and amounts and compositions of the organic matter appear related to the cause and degree of water column stratification and the resulting absence presence of dissolved o2 or h2s high cd mo u v zn and s contents a high degree of pyritization dop 0 75 0 88 and high high v v ni 0 84 0 89 indicate the presence of h2s in a strongly stratified water column intermediate contents of metals and s intermediate dop 0 67 0 75 and intermediate v v ni 054 0 82 indicate a less strongly stratified anoxic water column whereas low metal contents and low v v ni 0 46 0 60 indicate a weakly stratified dysoxic water column high p contents at the top of the organic matter rich intervals within the stark shale member indicate that phosphate precipitation was enhanced near the boundary between anoxic and dysoxic water compositions relatively abundant terrestrial organic matter in intervals deposited from the more strongly stratified h2s bearing water column indicates a combined halocline thermocline with the fresher near surface water the transport mode for the terrestrial organic matter the predominance of algal organic matter in intervals deposited from a less strongly stratified water column indicates the absence of the halocline and the presence of the more generally established thermocline relatively low amounts of degraded hydrogen poor organic matter characterize intervals deposited in a weakly stratified dysoxic water column the inferred variability in chemistry of the depositional environments may be related to climate variations and or minor changes in sea level during the general phase of deeper water deposition responsible for this widespread shale member