paleoaltimetry from stable isotope compositions of fossils stable isotope systematics of phosphatic vertebrate and carbonate invertebrate fossils are reviewed emphasizing external vs biological controls on isotope compositions and their variation external controls include elevation and isotopic lapse rates temperature atmospheric circulation patterns aridity and changes to precipitation seasonality e g development of monsoons biological controls include temperature regulation and temperature dependent biological activity water balance behavior and rates of hard part secretion and maturation some key factors include what sources of water an animal samples how those sources respond isotopically to elevation and the isotopic sensitivity of a biologic tissue to environmental changes general research design criteria are enumerated including numbers of fossils and analyses required as well as uncertainties in the interpretability of isotopic shifts isotope zoning from fossil teeth and shells from the indian foreland demonstrate comparable seasonal monsoon signals at 11 ma vs today implying a high and broad plateau at that time mean isotope compositions of fossil teeth from the lee of the cascade range central oregon show a pronounced decrease in 18 o initiating 7 ma signaling topographic rise associated with impingement of basin and range extension on the arc mean compositions and zoning in fossil shells from the northern rocky mountains indicate high elevations and topographic relief in the late cretaceous and early paleogene paleoaltimetry will principally benefit from better estimates of temperature because temperature lapse rates are less variable than isotopic lapse rates and because the combination of temperature and isotopic studies may help distinguish between local isotopic changes and distal ones caused by catchment or rain shadow effects

observations of periglacial landforms in utopia planitia with the high resolution imaging science experiment hirise 1 the region of western utopia planitia 80 105 e 40 55 n displays several types of landforms similar to earth periglacial features including scallop shaped depressions and networks of polygonal terrains the scalloped depressions have been proposed to originate from thermokarstic processes such as sublimation and or melting of near surface ground ice using hirise imagery we characterize these depressions and several associated distinct polygon networks in unprecedented morphologic and topographic detail and investigate support for an ice based degradation process the scalloped depressions and interior polygons and ridges are found to evolve together mainly influenced by sublimation local proximity of ground ice to the surface and obliquity variations

strong sea forcing and warmer winter during solar minima 2765 yr b p recorded in the growth bands of crassostrea sp from the confluence of river ganges eastern india abstract long term variation of solar activity plays a key role in controlling climatic oscillations during glacial interglacial cycles the records of such climatic shifts can be retrieved from sedimentary archives in overbank deposits found in the estuary regions of major rivers in the tropics which are fed by glaciers in this study we have shown the effect of solar variability on regional climate by altering the river discharge and incursion of warm water pool into the region adjoining bay of bengal during seasonal dry period the incremental growth bands present in the modern day meretrix sp and late holocene crassostrea sp were examined for reconstruction of temperature and water composition at the head bay region of the river ganges the conventional c14 techniques on fossil oyster yielded age of 2765 130 yr b p which coincides with a solar minima analysis of clumped isotope thermometry on the growth bands provided temperature estimates for the growth of shells the temperature estimates for the modern shell suggesting range of values showed a range between 13 and 42 c close to the observed temperatures recorded in the climatological data while the fossil shell had a range of values between 22 and 38 c the 18o measured in the aragonite together with the estimated temperature were used to deduce the water composition during growth at equilibrium condition the water 18o varied between 4 8 and 1 2 for the modern sample close to the observed values of water measured near this locality while the range in water composition inferred for the paleo samples was from 2 37 to 0 82 suggesting a stronger influence of sea water throughout the year the results are consistent with the argument of infiltration of water from neighbouring warm water pool into the estuary a similar approach can be extended to evaluate the effects of climate variability due to differential action of river discharge into the sea at seasonal time scales based on available mollusc shells in the sedimentary successions from the region

thermal contraction crack polygons on mars a synthesis from hirise phoenix and terrestrial analog studies thermal contraction crack polygons are complex landforms that have begun to be deciphered on earth and mars by the combined investigative efforts of geomorphology environmental monitoring physical models paleoclimate reconstruction and geochemistry thermal contraction crack polygons are excellent indicators of the current or past presence of ground ice ranging in ice content from weakly cemented soils to debris covered massive ice relative to larger topographic features polygons may form rapidly and reflect climate conditions at the time of formation preserving climate information as relict landforms in the geological record polygon morphology and internal textural characteristics can be used to distinguish surfaces modified by the seasonal presence of a wet active layer or dry active layer and to delimit subsurface ice conditions analysis of martian polygon morphology and distribution indicates that geologically recent thermal contraction crack polygons on mars form predominantly in an ice rich latitude dependent mantle more likely composed of massive ice deposited by precipitation than by cyclical vapor diffusion into regolith regional and local heterogeneities in polygon morphology can be used to distinguish variations in ice content deposition and modification history and to assess microclimate variation on timescales of ka to ma analyses of martian polygon morphology guided by investigations of terrestrial analog thermal contraction crack polygons strongly suggest the importance of excess ice in the formation and development of many martian thermal contraction crack polygons implying the presence of an ice rich substrate that was fractured during and subsequent to obliquity driven depositional periods and continually modified by ongoing vapor equilibration processes

oxygen and carbon isotope ratios of lampsilis cardium unionidae from two streams in agricultural watersheds of iowa usa abstract climate archives preserved as seasonal variation in oxygen and carbon isotope ratios 18o and 13c in unionid shells potentially provide records of pre instrumental environmental conditions in mid to high latitude continental regions this study measured 18o and 13c values of biogenic carbonate and 18owater to investigate the timing of growth line formation and to examine the utility of lampsilis cardium as an environmental archive we tested the hypotheses that 1 l cardium precipitates its shell in isotopic equilibrium with the environment during biomineralization and 2 growth lines form seasonally during winter months these questions were addressed by monitoring water chemistry by tagging l cardium to record growth and by combining sclerochronology and stable isotope geochemistry temperature and 18owater were measured fortnightly from september 2002 to july 2004 with a break in sampling from december 2003 to february 2004 in two iowa rivers boone river and buffalo creek these data were used to calculate expected 18o values to compare to measured shell values one hundred fifty four individuals were marked at the postero dorsal margin in september 2002 and june 2003 to monitor growth seven recaptured shells collected in july 2004 were analyzed for shell 18o and 13c across three growth lines including growth lines prior to the initial marking period from the growing edge toward the umbo comparison of shell 18o with expected values revealed precipitation of 18o in equilibrium with the ambient environment from early spring to early fall winter values were not recorded due to winter growth cessation change in temperature or reaching a threshold temperature appeared to control the onset and cessation of growth moreover the locations of seasonal growth lines corresponded to winter growth cessation allowing the assignment of calendar years to growth lines seasonal growth lines were distinguished from non seasonal disturbance lines by their seasonal location inferred from the 18o time series recorded in shell growth thus we can faithfully reconstruct ontogeny through time and environmental and climate conditions from mid to high latitudes using l cardium variation in 13cshell followed a more or less sinusoidal trend similar to the seasonal profiles of 18oshell suggesting that seasonal processes influenced the variation in carbon isotopes reduced amplitudes and more negative 13cshell values with increasing age suggest that kinetic and or metabolic isotope effects become important through ontogeny as observed in other bivalves the profiles of 13cshell potentially record local differences in landscape vegetation however specific factors influencing 13cshell are unknown and further study of water quality are required to fully assess the variation of 13cshell as an environmental proxy

oxygen isotope records of the australian flat oyster ostrea angasi as a potential temperature archive abstract the response of the oxygen isotope ratio 18o in shells of the australian native flat oyster ostrea angasi to changes in water temperature has been assessed using growth experiments conducted for one year at two locations on the east coast of australia the analysed 18o of the oyster shells 18oshell closely follows the predicted oyster shell 18o constructed from measured 18o in the water 18owater and water temperature influxes of freshwater that occur in the estuarine habitats of o angasi can modify the 18owater and consequently 18oshell salinity fluctuations can also cause interruptions to shell growth in this species this can cause overestimated temperatures in o angasi 18oshell temperature reconstructions a 18oshell temperature calibration was established for o angasi yielding the relationship t c 13 97 3 57 18oshell 18owater 0 17 18oshell 18owater 2 n 79 r2 0 79 which within the experimental uncertainties of the data is similar to other published biogenic carbonate paleotemperature equations

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

short and long term temporal variations in salinity and the oxygen carbon and hydrogen isotopic compositions of the hooghly estuary water india abstract the hooghly river estuary provides a unique experimental site to understand the effect of monsoonal river discharge on freshwater and seawater mixing water samples collected bi weekly for a duration of 17 months were analyzed for salinity 18o 13cdic as well as d to investigate the differential mixing of freshwater and seawater the differences in salinity and 18o of samples collected during low and high tides on the same day are strongly correlated suggesting a well mixed water column at our sampling site low salinity and depleted 18o during monsoon is consistent with increased river discharge as well as high rainfall we identified different slopes in a 18o versus salinity plot for the estuary water samples collected during monsoon and non monsoon seasons this is driven by composition of the freshwater source which is dominated by rainwater during monsoon and rivers during non monsoon months selected d analyses of samples indicate that groundwater contributes significantly to the hooghly estuary during low rainfall times of the year 13cdic measured in the water recorded low values towards the end of monsoon indicating low productivity i e increased organic respiration while progressively increasing 13cdic values from october till january as well as during some of the pre monsoon months can be explained by increasing productivity very low 13cdic 20 suggests involvement of carbon derived from anaerobic oxidation of organics and or methane with potential contribution from increased anthropogenic water supply an estimate of seawater incursion into the hooghly estuary at different times of the year is obtained by using salinity data in a two component mixing model presence of seawater was found maximum 31 37 during february till july and lowest less than or equal to 6 from september till november we notice a temporal offset between ganges river discharge farther upstream at farakka and salinity variation at the hooghly estuary we believe that this time lag is a result of the physical distance between farakka and kakdweep our sampling location and put constraints on the travel time of river water during early monsoon

validation of the recipe for broadband ground motion simulations of japanese crustal earthquakes the robustness of broadband ground motion simulation can promote seismic hazard assessment a broadband ground motion simulation technique called the recipe is used in the scenario earthquake shaking maps of the national seismic hazard maps for japan the recipe represents a fault rupture based on a multiple asperity model referred to as the characterized source model broadband ground motion time histories on the engineering bedrock are computed by a hybrid approach of the 3d finite difference method and the stochastic green s function method for the long 1 s and short period 70 km such conditions are outside of the target range of the recipe simulations using a 1d velocity structure model were also examined the simulation results for the 1d and 3d velocity structure models indicated that the 3d velocity structure models are important in reproducing pgv and the later phases with long duration especially on deep sediment sites

recipe for predicting strong ground motion from crustal earthquake scenarios we developed a recipe for predicting strong ground motions based on a characterization of the source model for future crustal earthquakes from recent developments of waveform inversion of strong motion data used to estimate the rupture process we have inferred that strong ground motion is primarily related to the slip heterogeneity inside the source rather than average slip in the entire rupture area asperities are characterized as regions that have large slip relative to the average slip on the rupture area the asperity areas as well as the total rupture area scale with seismic moment we determined that the areas of strong motion generation approximately coincide with the asperity areas based on the scaling relationships the deductive source model for the prediction of strong ground motions is characterized by three kinds of parameters outer inner and extra fault parameters the outer fault parameters are defined as entire rupture area and total seismic moment the inner fault parameters are defined as slip heterogeneity inside the source area of asperities and stress drop on each asperity based on the multiple asperity model the pattern of rupture nucleation and termination are the extra fault parameters that are related to geomorphology of active faults we have examined the validity of the earthquake sources constructed by our recipe by comparing simulated and observed ground motions from recent inland crustal earthquakes such as the 1995 kobe and 2005 fukuoka earthquakes

modification of wave cut and faulting controlled landforms from a casual observation that the form of degraded fault scarps resembles the error function this investigation proceeds through an elementary diffusion equation representation of landform evolution to the application of the resulting equations to the modern topography of scarplike landforms the morphologic observations can be analyzed either in the form of one or more cross strike elevation profiles or in the form of the slope offset plot a point plot of maximum scarp slope versus scarp offset working with either or both of these data representations for nine geologic structures which range in age from 3 to 400 ka b p and in offset from 1 to 50 m we apply analytical solutions for the vertical initial value scarp the vertical continuous offset scarp and the finite slope initial value scarp the model calculations are intrinsically ambiguous yielding as the final answer only the product t in the case of the initial value problem or the product a 1 in the case of the repeated faulting problem here t is the age of a single scarp forming event 2a is the vertical slip rate and is the mass diffusivity a single profile across three sea cliffs along the santa cruz california coast is analyzed as three separate initial value problems a reasonably constrained age for the sea cliff standing above the highway 1 platform returns 11 gkg 1 gkg 1 m2 ka with this we can date the two older sea cliffs in fact we do the converse age estimates for these two older sea cliffs based on a uniform rate of uplift both yield the same as for the lower sea cliff we treat a single profile of the raymond fault in pasadena san marino in terms of the repeated faulting problem for it the uplift rate of r crook and others yields 16 gkg the very substantial preexisting offset across the raymond fault must have been buried leveled some 230 ka b p when the modern topography began to form our analysis of the lake bonneville shoreline scarps reveals a dependence of t on 2a suggestive of nonlinear modification processes this appearance is treated with the finite slope initial value scarp model to determine 1 1 gkg for the lake bonneville shoreline scarps the suggestion of m n machette that approximately 100 000 year old meter high scarps are unobservable in weakly consolidated alluvial terranes of the basin and range and rio grande rift valley provinces can be formulated as 1 gkg the coincidence between this inequality and the lake bonneville shoreline is striking and it suggests that the value of 1 gkg may be generally applicable as a good first approximation to the modification of alluvial terranes within the semiarid regions of the western united states the lake bonneville shoreline is the basis for dating four sets of fault scarps in west central utah the drum mountains fault scarps can be modeled in several different circumstances but the most likely interpretation is that these fault scarps formed as the result of a single episode of normal faulting 3 6 to 5 7 ka b p the younger age is associated with quite low initial slope angles 25 the other three sets of fault scarps show no evidence for finite initial value slopes fault scarps along the eastern base of the fish springs range are very young 3 ka b p we estimate the age of fault scarps along the western flank of the oquirrh mountains to be 32 ka b p which meets the weak geologic constraint that they be older than the lake bonneville shoreline fault scarps along the northeastern margin of the sheeprock mountains are even older 53 ka b p an intriguing consequence of our single event analysis of these scarps is that an 11 5 m offset occurred in a single earthquake

calibrating the element composition of donax deltoides shells as a palaeo salinity proxy abstract bivalve shell chemistries provide valuable insights into past environments if relationships between shell chemistry and environmental conditions are known this study assessed the suitability of goolwa cockle donax deltoides shell element composition as an environmental proxy for southern australia a region lacking high resolution environmental records cockles were collected along an environmental gradient and the element composition of corresponding water and shell samples were quantified using a combination of icp aes and icp ms for water samples and la icp ms for shells of the elements analysed ba ca li ca and mg ca in shells reflected ambient water chemistries shell ba ca concentrations showed a significant negative relationship with recorded salinities and a positive non significant trend was observed between mg ca and water temperature further assessment of environmental and biological controls on element incorporation are required however ba ca in d deltoides shells appears a suitable palaeo salinity tool and has the potential to provide an easily accessible and valuable proxy to gain insights into past environmental conditions over extensive time scales

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

high resolution isotopic records from corals using ocean temperature and mass spawning chronometers abstract we present a 6 year long 1978 1984 18 o and 13 c record from a great barrier reef pandora reef porites lutea coral based on near weekly sample intervals a sampling technique was designed to minimise any smoothing or distortion of the isotopic record due to complex coral growth calyx architecture and calcification at depth within the tissue layer the arrival time of the mid winter minimum sea surface temperature is very consistent 2 weeks near pandora reef and provides an annual time marker offering more precision than the traditional density band chronometer the improved chronology and high resolution record demonstrate that signal distortion in porites due to calcification within the tissue layer and variable intra annual coral extension is generally negligible also confirmed is that the arrival time of monsoonal floods is precisely preserved 1 week within the skeleton of porites the sensitivity of weekly sampling allows the detection of a subtle warm to cool sea surface temperature anomaly which preceded by more than one year a similar temperature anomaly associated with the 1982 83 el nin o in the east pacific sharply higher 13 c values coincide with the time of the annual coral mass spawning event in the great barrier reef recognition of this mass spawning signal should simplify the interpretation of coral 13 c records and provides an additional precise time marker with which to adjust chronologies when intra annual coral extension is not constant

biological and water chemistry controls on sr ca ba ca mg ca and δ18o profiles in freshwater pearl mussel hyriopsis sp abstract we investigated oxygen isotope and sr ca ba ca and mg ca ratios in shells of a commercially cultured freshwater pearl mussel hyriopsis sp unionidae and ambient water the first order fluctuations of oxygen isotope ratios of the outer shell layer along the maximum growth axis recorded the mussels annual growth from 2002 to 2007 clear annual sr ca cycles suggest that sr was incorporated into the shells at a high rate during warm seasons all three examined shells showed a clear decrease in annual average sr ca with age inter and intra annual trends suggest that sr incorporation was higher during periods of faster growth the ba concentration and the ba ca ratio of ambient water showed neither an annual periodicity nor a seasonal trend in contrast to the findings of an inorganic aragonite precipitation experiment ba ca was positively correlated with ambient temperature in addition ba ca and sr ca ratios were positively correlated with each other these results suggest that not thermodynamic equilibrium partitioning but the shell growth rate controls ba incorporation into hyriopsis shells the mg ca profiles of the three shells suggest that complex factors control the incorporation of mg into shell aragonite water temperature and annual growth rates did not significantly influence mg incorporation and substantial interspecimen differences suggested that physicochemical factors do not exert any systematic control on mg ca ratios in hyriopsis instead the mg content of shell aragonite might reflect biological contamination with organic material or adsorption phenomena during crystal precipitation rather than regulated substitution into the aragonite crystal lattice our results suggest that trace element profiles in aragonitic bivalve shells could be interpreted as the result of strong biological controls over riding environmental influences on trace element incorporation

shell sclerochronology and stable isotopes of the bivalve anomalocardia flexuosa linnaeus 1767 from southern brazil implications for environmental and archaeological studies abstract this study presents the first stable isotopic and sclerochronological calibration of the bivalve anomalocardia flexuosa linnaeus 1767 in relation to environmental variables in a subtropical coastal area of southern brazil we investigate incremental shell growth patterns and 18o and 13c values of modern specimens collected alive from the laguna lagoonal system lls shells of anomalocardia flexuosa are also one of the main biological components of pre columbian archaeological shell mounds and middens distributed along the brazilian coastline we therefore selected archaeological specimens from a local late holocene shell mound cabecuda to compare their stable carbon and oxygen isotope values with those of modern specimens shell growth increments 18o and 13c values respond to a complex of environmental conditions involving for example the effects of temperature and salinity the isotopic information extracted from archaeological specimens from cabecuda shell midden in the lls indirectly indicates that environmental conditions during the late holocene were different from present day in particular intra shell 18o and 13c values of archaeological shells reveal a stronger marine influence at 3 ka cal bp which is in contrast to the seasonal freshwater seawater balance that currently prevails at the lls

rupture processes of the 2004 chuetsu mid niigata prefecture earthquake japan a series of events in a complex fault system 1 we relocated the hypocenters of the 2004 chuetsu earthquake sequence niigata japan using the double difference method the distribution of aftershocks reveals a complex fault system consisting of five different fault planes inversions of strong motion records for the five major events within the sequence indicate that the mainshock mw 6 6 and the largest aftershock mw 6 3 occurred on parallel wnw dipping fault planes the zones of large slip asperities of these two events are located near the hypocenters in contrast the three other large earthquakes mw 5 9 5 7 and 5 9 occurred on east dipping fault planes oriented perpendicular to the fault plane of the mainshock we used slip distributions deduced from waveform inversions to estimate the coulomb failure stress changes that occurred immediately prior to each event cff values were positive at the hypocenters and within the asperities of the major aftershocks these results suggest that stress changes resulting from individual earthquakes led directly to the occurrence of subsequent earthquakes within the complex fault system

drought and flood signals in subtropical estuaries recorded by stable isotope ratios in bivalve shells isotope ratios of carbon and oxygen recorded in biogenic carbonates can be effective proxies for ambient conditions in estuaries including salinity and temperature together they have the potential to allow periods of drought and flooding to be identified in subtropical estuaries that receive stochastic and aperiodic delivery of freshwater inflow we investigated the ability of 13c and 18o values in shell increments from the eastern oyster crassostrea virginica sampled from subtropical estuaries in the western gulf of mexico to indicate differences in temperature and salinity dynamics at fine spatial scales oyster shells at locations that experienced both hypersalinity during droughts and dramatic decreases in salinity during floods showed distinct variations in shell 13c and 18o values that reflected local salinity conditions in contrast oysters at sites where no major salinity fluctuation occurred showed only seasonal fluctuations in isotopes reflecting temperature and possibly feeding patterns further similar isotopic patterns were observed across multiple individuals from each site our results show that 13c and 18o values in shells measured together provide a powerful method to identify droughts and floods in subtropical estuaries and therefore extend records of dynamic inflow to these stressed ecosystems

a 2000 yr record of sacramento san joaquin river inflow to san francisco bay estuary california oxygen and carbon isotopic measurements of fossil bivalves macoma naarfa contained in estuarine sediment are used to reconstruct a late llolocene record of sitlinity and stream flow in san francisco bay discharge into the bay is a particularly good indicator of paleoclin ate in california because the bay s influent streams drain 40 of the state the isotopic record suggests that hetween al oul 1670 ant1 1900 calcnd r yc trs yr cal 1i i inflow to the bay was sul stantially greirler tlian the cstinli tecl precliversion inllow ol 1100 m3 s an unconforn ity representing a 900 yr hiatus is present in the core between 1670 ancl 750 yr cirl ii 13 possil ly r lusc cl by i n tjor 11ydrologic rl event over the p ist 750 yr strcitn ilow to s iii i ril cisco ikty ii is vitrirtl wit11 i pcriotl ol 200 yr i1lter11itte wet iltttl tlry i tlrougl t intc r rls typiritlly 11 rvc i lstecl 40 to 100 yr

nonlinear dynamics of ice wedge networks and resulting sensitivity to severe cooling events patterns of subsurface wedges of ice that form along cooling induced tension fractures expressed at the ground surface by ridges or troughs spaced 10 30 m apart are ubiquitous in polar lowlands1 fossilized ice wedges which are widespread at lower latitudes have been used to infer the duration2 3 4 and mean temperature5 6 of cold periods within proterozoic2 and quaternary climates3 4 5 6 7 8 9 10 11 12 13 and recent climate trends have been inferred from fracture frequency in active ice wedges14 here we present simulations from a numerical model for the evolution of ice wedge networks over a range of climate scenarios based on the interactions between thermal tensile stress fracture and ice wedges we find that short lived periods of severe cooling permanently alter the spacing between ice wedges as well as their fracture frequency this affects the rate at which the widths of ice wedges increase as well as the network s response to subsequent climate change we conclude that wedge spacing and width in ice wedge networks mainly reflect infrequent episodes of rapidly falling ground temperatures rather than mean conditions

experimental evidence of reaction induced fracturing during olivine carbonation author s zhu w fusseis f lisabeth h xing t xiao x de andrade v karato si abstract 2016 american geophysical union all rights reserved mineral carbonation a process that binds co2 in the form of carbonates by silicate weathering is widespread on the earth s surface because of the abundance of silicate rocks and the permanence of the carbonated solids sequestering co2 via mineral carbonation has generated lots of interests however it is unclear how the fluid rock reaction proceeds to completion in spite of an increasing solid volume we conducted a mineral carbonation experiment in which a sintered olivine aggregate reacted with a sodium bicarbonate solution at reservoir conditions time resolved synchrotron x ray microtomographic images show cracks in polygonal patterns arising in the surface layers and propagating into the interior of the olivine aggregate the nanotomography data reveal that the incipient cracks intersect at right angles we infer that stretching due to nonuniform volume expansion generates polygonal cracking of the surfaces our data shed new lights on the processes that control hydration and carbonation of peridotite

seasonal variability of rainfall recorded in growth bands of the giant african land snail lissachatina fulica bowdich from india seasonal rainfall patterns in bangalore india have been reconstructed using stable isotopic ratios in the growth bands of giant african land snail shells the present study was conducted at bangalore india which receives rain during the summer months the oxygen isotopic record in the rainwater samples collected during different months covering the period of the summer monsoon of the year 2008 is compared with the isotopic ratio in the gastropod growth bands deposited simultaneously the chronology of the shell growth band is independently established assuming the growth rate observed in a chamber experiment maintaining similar relative humidity and temperature conditions a consistent pattern observed in the isotopic ratio in the gastropod growth bands and rainwater is demonstrated and provides a novel approach for precipitation reconstruction at seasonal and weekly time scales this approach of using isotopic ratios in the gastropod growth bands for rainfall can serve as a substitute for filling gaps in rainfall data and for cases where no rain records are available in addition they can be used to determine the frequencies and magnitudes of dry spells from the past records c 2013 elsevier b v all rights reserved

oxygen isotopes of marine mollusc shells record eocene elevation change in the pyrenees abstract constraining paleoaltimetry of collisional orogens is critical to understand the dynamics of topographic evolution and climate tectonics retroactions here we use oxygen stable isotope record on oyster shells preserved in marine foreland deposits to examine the past elevation of the pyrenees during the eocene our approach is based on the comparison with the paris basin an intracratonic basin not influenced by orogenic growth the finding of a shift of 1 5 between 49 and 41 ma indicating more negative 18oc in the south pyrenean foreland is interpreted to reflect the inflow of river water sourced from higher elevation in the pyrenees to test this and provide paleoelevation estimate we adopt a morphologic hydrological model accounting for the hypsometry of drainage basin our best fitting model shows that the pyrenees rose up to 2000 m this indicates that the pyrenees reached high elevation in the eocene thus providing new critical constraints on their long term orogenic development 18o of marine mollusc shells are proved potentially attractive for paleoelevation studies especially for mountain belts where elevated continental surfaces have not been preserved

relic permafrost structures in the gobi of mongolia age and significance relict permafrost structures ice wedge casts and cryoturbation structures are present in the gobi of southern mongolia luminescence dates of sediments are presented to constrain the age of formation of permafrost structures these data show that there was a phase of permafrost development during the latter part of the last glacial after about 22 to 15 ka that resulted in cryoturbated sediments and ice wedge casts furthermore permafrost degradation occurred during late pleistocene times 13 10 ka and was absent during the early holocene these permafrost structures mark the southernmost evidence of permafrost in northern asia during late quaternary times and indicate that the mean annual air temperature was below approximately 6 c during their formation 1998 john wiley sons ltd

high latitude patterned grounds on mars classification distribution and climatic control patterned grounds such as polygonal features and slope stripes are the signature of the presence of ground ice and of temperature variations in cold regions on earth identifying similar features on mars is important to understand its past climate as well as the ground ice distribution in this study young patterned grounds are classed and mapped from the systematical analysis of mars observer camera high resolution images these features are located poleward of 55 latitude which fits the distribution of ground ice found by the neutron spectrometer onboard mars odyssey thermal contraction due to seasonal temperature variations is the predominant process of formation of polygons formed by cracks which sizes vary from 15 to 300 m the small 40 m widespread polygons are very recent and degraded by the desiccation of ground ice from the cracks which enhances the effect of ice sublimation the large polygons 50 to 300 m located only around the south co2 polar cap indicate the presence of ground ice and thus outline the limit of the co2 ice cap they could be due to the blanketing of water ice deposits by the advances and retreats of the residual co2 ice cap during the last thousand years large 50 250 m and homogeneous polygons similar to ice wedge polygons hillslope stripes and solifluction lobes may indicate that specific environments such as crater floors and hillslopes could have been submitted to freeze thaw cycles possibly related to higher summer temperatures in periods of obliquity higher than 35 these interpretations must be strengthened by higher resolution images such as those of the hirise mission of the mars reconnaissance orbiter because locations with past seasonal thaw could be of major interest as potential landing sites for the phoenix mission

can shells of freshwater mussels unionidae be used to estimate low summer discharge of rivers and associated droughts this paper examines if shell oxygen isotope ratios 18oar of unio sp can be used as a proxy of past discharge of the river meuse the proxy was developed from a modern dataset for the reference time interval 1997 2007 which showed a logarithmic relationship between discharge and measured water oxygen isotope ratios 18ow to test this relationship for past time intervals 18oar values were measured in the aragonite of the growth increments of four unio sp shells two from a relatively wet period and two from a very dry time interval 1910 1918 and 1969 1977 respectively shell 18oar records were converted into 18ow values using existing water temperature records summer 18ow values reconstructed from 18oar of 1910 1918 showed a similar range as the summer 18ow values for the reference time interval 1997 2007 whilst summer reconstructed 18ow values for the time interval 1969 1977 were anomalously high these high 18ow values suggest that the river meuse experienced severe summer droughts during the latter time interval 18ow values were then applied to calculate discharge values it was attempted to estimate discharge from the reconstructed 18ow values using the logarithmic relationship between 18ow and discharge a comparison of the calculated summer discharge results with observed discharge data showed that meuse low discharge events below a threshold value of 6 m3 s can be detected in the reconstructed 18ow records but true quantification remains problematic

a late miocene early pliocene chain of lakes fed by the colorado river evidence from sr c and o isotopes of the bouse formation and related units between grand canyon and the gulf of california we report strontium isotopic results for the late miocene hualapai limestone of the lake mead area arizona nevada and the latest miocene to early pliocene bouse formation and related units of the lower colorado river trough arizona california nevada together with parallel oxygen and carbon isotopic analyses of bouse samples to constrain the lake overflow model for integration of the colorado river sr isotopic analyses on the basal 1 5 cm of marl in particular along a transect over a range of altitude in the lowest altitude basin that contains freshwater brackish and marine fossils document the 87 sr 86 sr of first arriving bouse waters results reinforce the similarity between the 87 sr 86 sr of bouse formation carbonates and present day colorado river water and the systematic distinction of these values from neogene marine sr basal bouse samples show that 87 sr 86 sr decreased from 0 7111 to values in the range 0 7107 0 7109 during early basin filling 87 sr 86 sr values from a recently identified marl in the las vegas area are within the range of bouse sr ratios 87 sr 86 sr values from the hualapai limestone decrease upsection from 0 7195 to 0 7137 in the approach to a time soon after 6 ma when hualapai deposition ceased and the colorado river became established through the lake mead area bouse formation 18 o values range from 12 9 to 1 0 vienna pee dee belemnite vpdb and 13 c between 6 5 and 3 4 vpdb negative 18 o values appear to require a continental origin for waters and the trend to higher 18 o suggests evaporation in lake waters sr and stable isotopic results for sectioned barnacle shells and from bedding planes of the marine fish fossil colpichthys regis demonstrate that these animals lived in saline freshwater and that there is no evidence for incursions of marine water either long lived or brief in duration lack of correlation of sr and o isotopic variations in the same samples also argue strongly against systematic replacement of sr in bouse carbonates after deposition our results reinforce the conclusion that the bouse formation was deposited in a descending series of basins connected by overflow of colorado river water the hualapai limestone records a separate and earlier lake that may have been progressively influenced by colorado river water as the time of river integration approached

micro relief development in polygonal patterned ground in the dry valleys of antarctica polygonal patterned ground in polar regions of both earth and mars has received considerable attention in comparison with the size shape and arrangement of the polygons the diverse micro relief and topography termed here simply relief of polygonal patterned ground have been understudied and yet the relief reflects important conditions and processes occurring directly below the ground surface and it can be observed readily in the field and through remote sensing herein we describe the relief characteristic of the simplest and relatively young form of patterned ground in the dry valleys of antarctic we also develop a numerical model to examine the generation of relief due to subsurface material being shouldered aside contraction cracks by incremental sand wedges growth and to down slope creep of loose granular material on the surface we model the longterm subsurface deformation of ice cemented permafrost as a non linear viscous material our modeling is guided and validated using decades of field measurements of surface displacements of the permafrost and relief this work has implications for assessing the activity of surfaces on earth and mars and much larger scale potential manifestations of incremental wedging in icy material namely the distinct paired ridges on europa

relict sand wedges in southern patagonia and their stratigraphic and paleo environmental significance abstract relict sand wedges are ubiquitous in southern patagonia at six sites we conducted detailed investigations of stratigraphy soils and wedge frequency and characteristics some sections contain four or more buried horizons with casts the cryogenic features are dominantly relict sand wedges with an average depth maximum apparent width minimum apparent width and h w of 78 39 3 8 and 2 9 cm respectively the host materials are fine textured silt loam silty clay loam clay loam till and the infillings are aeolian sand the soils are primarily calciargidic argixerolls that bear a legacy of climate change whereas the sand wedges formed during very cold 4 to 8 c or colder and dry ca 100 mm precipitation yr glacial periods petrocalcic horizons from calcium carbonate contributed by dustfall formed during warmer 7 c or warmer and moister 250 mm yr interglacial periods the paleo argillic bt horizons reflect unusually moist interglacial events where the mean annual precipitation may have been 400 mm yr permafrost was nearly continuous in southern patagonia during the illinoian glacial stage ca 200 ka the early to mid pleistocene ca 800 500 ka and on two occasions during the early pleistocene ca 1 0 1 1 ma

shaking maps for scenario earthquakes by applying the upgraded version of the strong ground motion prediction method recipe the strong ground motion prediction method recipe was published by the headquarters for earthquake research promotion herp of japan herp has applied this method to prepare shaking maps for scenario earthquakes in specific active faults recently recipe was updated following its verification by simulations of strong ground motions associated with the mw 6 6 off shore earthquake west of fukuoka prefecture in 2005 which occurred in the northwest part of the kego fault zone located in northern kyushu japan one of the prominent changes in the upgraded version of recipe is the inclusion of a procedure to evaluate seismic intensities on the ground surface from waveforms of s wave velocity of 400 m s on the engineering bedrock by applying the upgraded version of recipe we have made shaking maps for earthquakes in the southeast part of the kego fault zone which is located directly below the mega city of fukuoka we assume four source models for scenario earthquakes the locations of the asperities and the hypocenters vary between the models the results show that in all cases disastrous seismic intensities can strike a wide area of fukuoka city differences in the distributions of seismic intensities among the four cases can be clearly observed in the area located on the extension of the source fault furthermore we construct a velocity layer structure model on the engineering bedrock for the central area of fukuoka city we assess not only the distribution of seismic intensities but also waveforms on the ground by using an equivalent linear method for the central area of fukuoka city

spatial relationships between patterned ground and ground ice detected by the neutron spectrometer on mars 1 patterned grounds like polygonal features are the signature of climatic effects in periglacial regions on earth identifying similar features on mars is important for an understanding of the past martian climate in this study we mapped fresh patterned landforms from the systematic analysis of mars orbiter camera high resolution images we show that most of them are distributed at latitudes poleward of 55 making a climatic control likely this distribution correlates to the distribution of ground ice detected by the neutron spectrometer aboard mars odyssey this correlation is likely the consequence of the neutron spectrometer detecting ice no deeper than about 1 m patterned ground formation requires ice in this range of depth because these features are triggered by the propagation of a thermal wave that is driven by seasonal or diurnal changes in insolation which affect the temperature in the uppermost ground layers sublimation seems to play a role in the shaping of many of the small patterns observed at latitudes between 55 and 70 no widespread polygonal features are correlated to the equatorial regions where hydrogen is detected by the neutron spectrometer

marine or estuarine radiocarbon reservoir corrections for mollusks a case study from a medieval site in the south of england abstract mollusk shells are frequently radiocarbon dated and provide reliable calibrated age ranges when the regional marine reservoir correction is well established for mollusks from an estuarine environment the reservoir correction may be significantly different than the regional marine reservoir correction due to the input of bedrock or soil derived carbonates some mollusk species such as oysters are tolerant of a significant range of salinities which makes it difficult to determine which reservoir correction is appropriate a case study is presented of an anomalous radiocarbon age for an oyster shell paint dish found in the fabric of the ruined nave walls of st mary s church shoreham by sea west sussex england stable isotopes 18 o and 13 c were used to establish the type of environment in which the oyster had lived paired marine and terrestrial samples from a nearby medieval site were radiocarbon dated to provide an appropriate reservoir correction

improved chronostratigraphic reference curve of late neogene seawater 87sr 86sr we present a reference curve of seawater 87 sr 86 sr variation through the past 7 m y based on 455 samples of planktonic foraminifera from ocean drilling program odp site 758 in the indian ocean this single site curve is superior to extant curves because of several features 1 a continuous sedimentary section free of disturbances 2 a well determined and precise chronostratigraphy that is calibrated to numeric age on the basis of continuous magnetostratigraphy and a refined astronomical time scale 3 a high temporal resolution sample interval averages 15 ka 4 an improved analytical reproducibility and 5 a uniformly high sample quality the gross structure of the site 758 curve is generally similar to that observed in previous work but the increased temporal resolution and decreased analytical scatter of the curve provide improved chronostratigraphic resolution at the 95 confidence level uncertainties on age estimates range from 0 60 m y in the lower pleistocene and upper miocene to 2 03 m y in the middle pliocene moreover this detailed record identifies two periods of steplike increases in seawater 87 sr 86 sr 6 10 to 5 80 ma and 1 46 to 1 13 ma that are characterized by rates of change of 150 10 6 m y these features if verified at other sites indicate abrupt changes in the sr mass balance of the ocean and may be used as precise event markers in late neogene marine sections

reconstructing intra annual growth of freshwater mussels using oxygen isotopes abstract intra annual growth rates from the bivalve mollusk lampsilis cardium unionidae were reconstructed using measured oxygen isotope 18o profiles together with high resolution environmental records mussels from a single cohort 2007 were grown in two different settings at the columbus zoo aquarium freshwater mussel conservation research center mrc located in central ohio usa outside specimens were collected from sediment laden cages deployed in the o shaughnessy reservoir a single inside specimen was collected from the raceways in the mrc measured 18ocarb profiles from these specimens were calibrated with a predicted oxygen isotope envelope i e the daily range of potential 18ocarb values calculated from hourly water temperatures and weekly 18owater samples collected in 2010 this exercise suggests the outside specimens commenced 2010 shell deposition in late april and ceased in latest october six month growing season in contrast the inside growing season lasted only three months early july and early september calculated daily growth rates from both sites were faster early in the year but highly episodic throughout maximum daily growth rates for the outside and inside specimens were 300 and 436 m day respectively analysis of annual growth rates from the entire cohort suggests the inside specimens grew slower following transplantation in subsequent years however their growth rates were nearly identical to the outside population our results suggest that despite the fact that both populations have similar annual growth rates they have different intra annual growth patterns thus caution should be exercised when extrapolating intra annual growth patterns from cultured specimens to natural populations

taxonomic overview and tusk growth analyses of ziegler reservoir proboscideans abstract at an altitude of 2705 m in the colorado rockies usa the ziegler reservoir fossil site gives a rare look at a high elevation ecosystem from the late pleistocene especially mis 5 of north america remains of more than four mammoths and about 35 mastodons dominate the macrofossil assemblage mammoth remains are attributed to mammuthus columbi and mastodon remains are referred to the well known continent wide mammut americanum mastodon remains occur within and between several lake margin slump deposits their deposition must therefore have occurred as events that were to some degree separate in time we treat the mastodon assemblage in each stratigraphic unit as a source of information on environmental conditions during the lives of these individuals mastodon mandibular tusks are abundant at the site and represent both males and females from calves to full grown adults this study presents the first attempt to use microct thin section and isotope records from mandibular tusks to reconstruct features of life history we recognize an up section trend in 18o profiles toward higher values suggestive of warmer temperatures throughout this sequence mastodon growth histories show low mean sensitivities suggestive of low levels of environmental stress this work helps frame expectations for assessing environmental pressures on terminal pleistocene populations

stable and clumped isotope sclerochronologies of mussels from the brazos river texas usa environmental and ecologic proxy abstract oxygen isotope sclerochronology with mollusk shells can provide vital environmental and ecologic information but is complicated in regulated subtropical rivers by irregular river water 18o and consequently irregular shell 18o patterns we performed multi proxy analyses 18o 13c clumped isotopes from serially sampled freshwater mussels in two specimens each of amblema plicata and cyrtonaias tampicoensis from the brazos river texas to age specimens and test whether they accurately record environmental conditions such as river discharge and water source oxygen isotopic measurements are similar to predicted aragonite 18o values based on temperature and water 18o but the record is complex and irregular to better resolve the chronologies we performed clumped isotope analyses on select shell intervals clumped isotope temperatures t 47 ranged from 19 to 36 c summer t 47 values were 3 5 c higher than measured temperatures suggesting an offset in paleothermometer calibration chronologies based on 47 and 18o reveal specimen ages of 3 4 years and winter growth cessation or dramatic slowing in both c tampicoensis and a plicata highlighting thermal limitations on growth and potential biases in environmental reconstructions compared with modern shells historical shells collected before intensive damming showed lower 18o values yet similar clumped temperatures suggesting enhanced evaporation in modern river water due to impoundment and or the 2011 12 drought carbon isotope trends were similar between conspecific shells but differed between species with substantially higher average values for a plicata shells 9 than c tampicoensis shells 12 the correlation between shell 13c values and the release of 13c enriched waters from upstream reservoirs demonstrates that 13c can be used as a proxy for dam release in regulated rivers

holocene climatic vicissitudes and sea level changes in the south western coast of india appraisal of stable isotopes and palynology abstract the southern kerala coast in sw india has experienced dramatic changes in climate and sea level during holocene these changes are apparently well preserved in the sedimentary archives of the estuarine basins that are entrenched on the uplifted neogene deposits here we report the sedimentary processes palaeoclimate and sea level records decoded from two borehole cores puthenthuruthu and munrothuruthu borehole cores retrieved respectively from the marine and fluvial ends of the second largest estuarine basin in sw india the ashtamudi estuary using sedimentology palynology and stable isotopes as the major proxies the heavy rainfall event at the latter half of early holocene 6117 101 bp is reflected well in the isotopic signatures of the puthenthuruthu borehole core the higher level of lighter isotopes of oxygen and carbon at 10 15 m below ground level is a clear indication of freshwater influx from the hinterland due to intensified monsoon activity this in turn was responsible for the development of bay head delta in the fluvial end of the estuary during early middle holocene period palynological contents below the level indicate a facies change as freshwater and terrestrial elements dominate over marine contents further the occurrence of desmids shows the marine facies is being gradually replaced by freshwater to continental facies this was followed by the deposition of littoral sands as flood tide islands within the estuarine basin the palynological investigations of sediments with radiocarbon age of 4350 90 bp in the munrothuruthu borehole core show a dry phase with high saline depositional environment in the beginning which is followed by influx of freshwater as indicated by the higher content of lighter isotopes of carbon and oxygen in the calcareous nodules algal pisolites embedded in the sediments the occurrence of pteridophytic spores and a few pollen of cullenia in the palynological preparations in the upper half of the silt and clay dominated intervening layers reiterate this view

the use of oxygen isotope variation in shells of estuarine mollusks as a quantitative record of seasonal and annual colorado river discharge abstract we describe a new method for the calculation of river flow that uses the oxygen isotope composition of bivalve mollusk shells that grew in the river water seawater mixing zone of the colorado river estuary sclerochronological techniques are used to identify tidally induced fortnight scale bundles of daily growth increments within shell cross sections these fortnightly markers are used to establish a chronology for samples taken for 18 o analysis a composite seasonal 18 o profile derived from five shells that grew in the absence of river water flow is used as a baseline against which profiles of river influenced shells are compared because this comparison is between matched fortnights within a year the temperature of shell growth is likely to be very similar the difference in 18 o between the river influenced shell and the no flow composite shell therefore represents the change in the 18 o of the water due to the presence of river water in the mixing zone the river water end member is also determined within a fortnightly context so that the change in the 18 o of mixing zone water can be used to calculate the relative proportions of seawater and fresh water the fresh water end member is calculated from the 18 o of bivalves alive prior to the emplacement of dams and water diversions on the colorado river the marine end member is based on direct measurements of the 18 o of northern gulf of california water during times of no colorado river flow the system has been calibrated to absolute flow amounts using recent releases of known volume and rate

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

recent freshening in the kara sea siberia recorded by stable isotopes in arctic bivalve shells oxygen and stable carbon isotope records along the growth direction on shells of the bivalve species astarte borealis and serripes groenlandicus reliably record all important aspects of the bottom water hydrography in the shallow southeastern kara sea despite uncertainties about the isotopic range due to sparse sampling and the possibility of growth rate changes changing freshwater supply from the rivers ob and yenisei is the main cause for seasonal temperature and salinity variations near the three sampling locations in 20 to 70 m water depth as suggested by ctd measurements and modeling peak winter salinity of the simulated hydrographic data series and peak winter values in the isotope records follow negative trends which indicate a freshening of the bottom water due to an increasing fraction of river water during the 1990s this freshening affected the whole kara sea and coincided with a lowering of regional air pressure gradients as indicated by the declining arctic oscillation index the resulting weakening of the prevailing southwesterly winds diminished the inflow of saline atlantic derived water from the barents sea through the kara strait in the southwest and additionally reduced the export of river water toward the north and northeast into the arctic basin saline atlantic derived water thus was replaced by freshwater which was successively accumulated in the kara sea and accordingly imprinted on the stable isotope composition of the bivalve shells the 1990s freshening in the kara sea thus may be caused by natural variations rather than being a signal for global change

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

ice wedge casts and relict patterned ground in central illinois and their environmental significance abstract sediment features and soil patterns indicate that permafrost developed beyond the late wisconsinan woodfordian ice margin in illinois vertical wedge shaped bodies in woodfordian glacigenic deposits and buried by woodfordian loess are interpreted to be ice wedge casts large scale patterned ground common on the late wisconsinan drift plain and on the illinoian drift plain to the south and west also is interpreted to be the result of ice wedge formation permafrost extended to about 38 30 n latitude and formed during the interval from about 21 000 to 16 000 yr b p formation and degradation of permafrost was time transgressive directly related to the ice marginal climate and probably restricted temporally to less than 1000 years at a site the following environmental conditions are suggested near the ice margin mean annual ground temperature 3 c mean annual air temperature 6 2 c less precipitation than modern particularly in winter strong and likely dry wind systems and relatively open vegetation with few woody plants

three dimensional p and s wave velocity structures beneath the japan islands obtained by high density seismic stations by seismic tomography abstract we construct fine scale 3d p and s wave velocity structures of the crust and upper mantle beneath the whole japan islands with a unified resolution where the pacific pac and philippine sea phs plates subduct beneath the eurasian eur plate we can detect the low velocity low v oceanic crust of the pac and phs plates at their uppermost part beneath almost all the japan islands the depth limit of the imaged oceanic crust varies with the regions high vp vs zones are widely distributed in the lower crust especially beneath the volcanic front and the high strain rate zones are located at the edge of the extremely high vp vs zone however vp vs at the top of the mantle wedge is not so high beneath northern japan we can image the high v subducting pac plate using the tomographic method without any assumption of velocity discontinuities we also imaged the heterogeneous structure in the pac plate such as the low v zone considered as the old seamount or the highly seismic zone within the double seismic zone where the seismic fault ruptured by the earthquake connects the upper and lower layer of the double seismic zone beneath central japan thrust type small repeating earthquakes occur at the boundary between the eur and phs plates and are located at the upper part of the low v layer that is considered to be the oceanic crust of the phs plate in addition to the low v oceanic crust the subducting high v pac plate is clearly imaged to depths of approximately 250 km and the subducting high v phs zone to depths of approximately 180 km is considered to be the phs plate beneath southwestern japan the iso depth lines of the moho discontinuity in the phs plate derived by the receiver function method divide the upper low v layer and lower high v layer of our model at depths of 30 50 km beneath kyushu the steeply subducting phs plate is clearly imaged to depths of approximately 250 km with high velocities the high vp vs zone is considered as the lower crust of the eur plate or the oceanic crust of the phs plate at depths of 25 35 km and the partially serpentinized mantle wedge of the eur plate at depths of 30 45 km beneath southwestern japan the deep low frequency nonvolcanic tremors occur at all parts of the high vp vs zone within the zone the seaward side and the landward side where the phs plate encounters the mantle wedge of the eur plate we prove that we can objectively obtain the fine scale 3d structure with simple constraints such as only 1d initial velocity model with no velocity discontinuity

influence of the upwelling events on the δ13c and δ18o of the benthic bivalve shells of the south western continental margin of india in this study the influence of the spatial and temporal variability of upwelling intensity and the associated biological productivity observed during different phases of summer monsoon along the southwestern continental margin of india swcmi on the 13c and 18o of the inorganic biogenic carbonate shells was investigated multispecies benthic bivalve shells 1 5 mm separated from ten surface sediment samples of swcmi off 12 n 10 n and 9 n collected during the onset osm and peak psm phase of the summer monsoon of 2009 were analysed for 13c and 18o sea surface temperature along the study region indicates prominent upwelling in psm than in osm a comparison of analytical and predicted values for 18o in the bivalve shells confirmed their in situ origin during both the sampling periods during psm the 13c values in the benthic bivalve shells were more depleted in 13c than during osm which recorded lower values of 13c in dissolved inorganic carbon of bottom waters expected in the study region in psm due to the upwelled waters high surface productivity and the associated high degradation of the organic matter in the subsurface and bottom waters however this depletion of 13c was not observed in benthic bivalve shells obtained from 10 n since it is influenced by high export fluxes of carbon from the cochin estuary since early monsoon months

variations in the strontium isotopic composition of seawater during the neogene the authors report 261 strontium isotopic analyses of well preserved planktonic foraminifers from three deep sea drilling project sites 519 588 and 607 these samples cover the period from 24 ma to present with an average of approximately one sample per 100 ka the combination of high sample density and uniformity of analytical procedures has produced a well defined record of changes in the sup 87 sr sup 86 sr of seawater during the neogene the record can be viewed as a series of essentially linear segments with slopes ranging from as high as 6 times 10 sup minus 5 m y to as low as 0 m y the times associated with major inflections in the curve do not appear to correspond to simple geologic phenomena such as eustatic cycles but are probably controlled by a combination of tectonic and climatic factors that influenced the abundance and isotopic composition of terrestrial strontium input to the oceans the strontium isotopic data are consistent with a progressive increase in the chemical weathering rates of the continents during the neogene probably related to repeated glaciations increased exposure of continents by lowered sea level and increased continental relief resulting from high rates of tectonic uplift

composition of stable isotopes in geoduck panopea abrupta shells a preliminary assessment of annual and seasonal paleoceanographic changes in the northeast pacific abstract we tested the suitability of using panopea abrupta geoduck shells to evaluate changes in both annual and seasonal sea surface temperature geoducks are long lived and deposit annual growth increments within their shell each winter making them potentially excellent paleoceanographic archives shells were sampled by thin section from the hinge plate region where the first 20 30 years of growth provide relatively wide annual increments suitable for sampling for isotopic analysis the geoducks used in this study were collected in ad 2000 from west of protection island located at the eastern end of the strait of juan de fuca the isotopic record is compared to the historic instrumental record as well as the thickness of geoduck growth increment measurements which were also correlated with water temperature strom a francis r c mantua n j miles e l peterson d l 2004 north pacific climate recorded in growth rings of geoduck clams a new tool for paleoenvironmental reconstruction geophysical research letters 31 p lo6206 doi 10 1029 2004gl019440 the annual average oxygen isotopic values from two geoduck clams whose first years of growth correspond to the early historic instrumental record ad 1920 appear to be recording trends in sea surface temperature intra annual sampling of annual growth increments indicates that the shells also appear to be recording seasonal changes in sea surface temperature preliminary analysis of carbon isotopic data on both the annual and seasonal timescales indicate the potential for assessing productivity changes in ambient seawater

an evaluation of mg ca sr ca and ba ca ratios as environmental proxies in aragonite bivalve shells the influence of salinity and water chemistry on mg ca sr ca and ba ca ratios in the aragonitic shells of the manila clam was investigated clams were reared at constant temperature 20 c under different controlled conditions of salinity commonly encountered in their natural habitat clams were held in three tanks with a constant salinity of 35 for the first 35days and then two tanks were changed to lower salinities 20 and 28 for the next 29days individual shell mg ca sr ca and ba ca ratios were studied through time despite stable conditions temperature salinity and mg cawater for clams reared at salinity 35 during the experiment mg ca shell ratios increased through the time moreover the salinity decrease at t35 slowed the increase of mg ca shell ratios at salinity 28 and resulted in an mg cashell decrease at salinity 20 despite similar mg cawater ratios in the different salinity treatments microprobe analyses illustrate that mg varies along contemporaneous growth lines the variable shell mg ca ratios suggest that incorporation of magnesium into shell carbonate is strongly regulated by the organism and not by environmental conditions interestingly microprobe analyses illustrated that mg was not associated with shell sulfur as other studies have suggested sr ca shell ratios of clams reared at salinity 35 and under constant conditions were also not as constant as expected if sr ca ratios were an environmental proxy there was an inverse correlation between shell sr ca and salinity despite a slight positive correlation between salinity and sr ca ratios of the water indicating that sr ca ratios do not reflect environmental conditions a strong inverse correlation between salinity and ba ca shell ratios and a positive correlation between ba ca shell and ba ca water was observed therefore ba ca shell ratios seem to be a promising proxy of high resolution 1day salinity variations in estuarine waters via the relationship between ba ca water and salinity this study clearly illustrates that both mg ca and sr ca ratios in aragonite shells are not under environmental control and that ba ca ratios are with the later tracking high resolution water ba ca ratios and hence estuarine salinity variations

paleosalinity in a brackish lake during the holocene based on stable oxygen and carbon isotopes of shell carbonate in nakaumi lagoon southwest japan abstract based on the relationship between salinity and 18 o and 13 c of modern shells in the lake nakaumi shinji lagoon system southwestern japan where the salinity changes regularly from ca 1 psu to 34 psu a paleosalinity record for nakaumi lagoon during the holocene has been derived from bulk mollusk shell 18 o and 13 c data the robust relationships between the salinity and modern shell 18 o ar and 13 c ar aragonite were used to calibrate the paleosalinity reconstruction the salinity relationships are expressed by the regressions salinity psu 3 86 18 o ar vpdb 33 9 n 18 r 0 978 salinity psu 4 05 13 c ar vpdb 31 8 n 18 r 0 977 applying these equations to bulk shell 18 o ar and 13 c ar in the 20 m sediment core very similar salinity histories were reconstructed from either oxygen or carbon isotope ratio data at the beginning of lacustrine sediment deposition 8000 7500 14 c yr b p paleosalinity of the bottom water in the central portion of nakaumi lagoon increased from 22 to 32 psu during the 7500 5500 yr b p interval which approximately corresponds to the holocene climatic optimum and high sea level stand salinity ranged from 27 to 37 psu after 5500 yr b p salinity lessened under the cooling climate with a minimum value of 24 27 psu at 3000 1000 yr b p the results show a consistent relationship between climate change sea level and salinity in the lagoon during the holocene

possible pingos and a periglacial landscape in northwest utopia planitia hydrostatic closed system pingos are small elongate to circular ice cored mounds that are perennial features of some periglacial landscapes the growth and development of hydrostatic pingos is contingent upon the presence of surface water freezing processes and of deep continuous ice cemented permafrost other cold climate landforms such as small sized polygonal patterned ground also may occur in the areas where pingos are found on mars landscapes comprising small elongate to circular mounds and other possible periglacial features have been identified in various areas including utopia planitia where water is thought to have played an important role in landscape evolution despite the importance of the martian mounds as possible markers of water most accounts of them in the planetary science literature have been brief and or based upon viking imagery we use a high resolution mars orbiter camera image eo300299 and superposed mars orbiter laser altimeter data tracks to describe and characterise a crater floor landscape in northwest utopia planitia 64 8 n 292 7 w the landscape comprises an assemblage of landforms that is consistent with the past presence of water and of periglacial processes this geomorphological assemblage may have formed as recently as the last episode of high obliquity a similar assemblage of landforms is found in the tuktoyaktuk peninsula of northern canada and other terrestrial cold climate landscapes we point to the similarity of the two assemblages and suggest that the small roughly circular mounds on the floor of the impact crater in northwest utopia planitia are hydrostatic pingos like the hydrostatic pingos of the tuktoyaktuk peninsula the origin of the crater floor mounds could be tied to the loss of ponded local water permafrost aggradation and the evolution of a sub surface ice core

the first 7 years 1978 1985 of ice wedge growth illisarvik experimental drained lake site western arctic coast a large lake measuring 600 m 300 m and with a depth of nearly 5 m was artificially drained on 13 august 1978 observations on the formation width and depth of thermal contraction cracks for the first 7 years show that the crack profiles and ice wedge growth rates differ markedly from those of old ice wedges reported in the literature the first winter s cracks had box like profiles with surface widths to 10 cm and depths to 2 5 m some cracks continued to widen and deepen once opened in early winter and then narrowed or even closed completely in summer mean growth rates for the ice wedges for the first few years have been as much as 3 5 cm year temperature gradients at the time of first cracking have been in the range of 10 15 c m the growth rate of young ice wedges is site specific and temperature dependent varying with factors such as the temperature gradient vegetation and snow cover so an estimate of the age of an ice wedge from its width will usually be impossible a study of crack w

the colorado river system and neogene sedimentary formations along its course apparent sr isotopic connections abstract water samples from the colorado river and its tributaries provide a present day 87sr 86sr profile of the colorado river system from moab utah down to the gulf of california 87sr 86sr values around 0 7097 are prevalent above the grand canyon and values of 0 7103 or higher are observed below the grand canyon 87sr 86sr values close to the seawater ratio of 0 70917 are seen near the colorado river delta all tributaries except the green river contribute sr that is lower in 87sr 86sr than the main colorado the cause of the increase in 87sr 86sr through the grand canyon and lake mead area has not been found samples of carbonate and gypsum from the lower lacustrine member of the mid miocene to pliocene bidahochi formation in northern arizona yield average 87sr 86sr of 0 70972 this agrees quite well with weighted averages of present day colorado system rivers that flow into the area which can be computed at 0 70972 or 0 70984 depending on assumptions this correspondence argues that the present

growth pattern and oxygen isotopic systematics of modern freshwater mollusks along an elevation transect implications for paleoclimate reconstruction abstract fossil mollusk shells are widely distributed in the geologic records and their oxygen isotopic compositions have been used to reconstruct seasonality local climatic and elevation conditions however interpretation of isotope data from fossil shells to estimate paleoclimate and elevation is often ambiguous this study examines the oxygen isotopic systematics of modern freshwater gastropods bellamya and radix shells along an elevation climate transect in the asian monsoon region of china to improve the accuracy of paleoclimate and paleoelevation reconstruction using stable isotopes in fossil shells the results from sclerochronological analyses of the shells show that the intra shell oxygen isotopic pattern is determined by seasonal variations in lake water temperature and water isotopic composition as well as the life cycle of the organism both bellamya and radix appear to grow throughout the year in lakes where water temperature does not fall below 13 c radix in the high elevation cold habitat although prefers to grow in the warmer months can survive through the freezing temperature the 18o patterns in the shells are similar across the elevation climate transect showing high 18o values in the winter months and low 18o values in the summer months consistent with the expected pattern in asian monsoon region the average growth rates of the shells were highest at the lowest elevation site warm and humid climate but were similar at the mid to high elevation sites for large shells 2 2 cm for bellamya and 1 4 cm for radix average growth temperatures calculated using the aragonite oxygen isotope thermometer closely approximate the annual mean water temperature while their intra shell variability is a good proxy for the amplitude of seasonal variations in monthly air temperature this suggests that large shells of both bellamya and radix are excellent archives of lake environmental conditions and most suitable for paleoenvironmental studies

seasonality in the north sea during the allerod and late medieval climate optimum using bivalve sclerochronology seasonal temperature patterns may have changed through time in response to current global warming however the temporal resolution of available proxy records is not sufficient to quantify paleotemperature seasonality prior to anthropogenic forcing of the climate in the present study we reconstructed seasonal and inter annual temperature patterns of the north sea during the last 140 years the allerod interglacial and the late medieval climate optimum using sclerochronological and 18oaragonite data from bivalve shells arctica islandica on average the climate during 1278 1353 ad was ca 1 1 c colder and seasonality was ca 60 less than today during the allerod long term temperatures remained about 3 2 c below present values and absolute summer and winter anomalies were ca 4 and 2 7 c respectively however seasonality was statistically indistinguishable from today long term average temperatures compare well with existing data for the late medieval and allerod but detailed information on seasonality during the studied time intervals has never been presented before our data also demonstrated that annual instrumental and 18oaragonite derived temperatures did not always match this difference is explained by 1 nao driven salinity changes which influence the temperature estimation from 18oaragonite and 2 food driven changes in growth rates portions of the shell that formed more rapidly are overrepresented in carbonate samples our study indicated that individual bivalve shells can open discrete near century long ultra high resolution windows into the climate past such information can be vital for testing and verifying numerical climate models

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