natural uranium and strontium isotope tracers of water sources and surface water groundwater interactions in arid wetlands pahranagat valley nevada usa summary near surface physical and chemical process can strongly affect dissolved ion concentrations and stable isotope compositions of water in wetland settings especially under arid climate conditions in contrast heavy radiogenic isotopes of strontium 87sr 86sr and uranium 234u 238u remain largely unaffected and can be used to help identify unique signatures from different sources and quantify end member mixing that would otherwise be difficult to determine the utility of combined sr and u isotopes are demonstrated in this study of wetland habitats on the pahranagat national wildlife refuge which depend on supply from large volume springs north of the refuge and from small volume springs and seeps within the refuge water budgets from these sources have not been quantified previously evaporation transpiration seasonally variable surface flow and water management practices complicate the use of conventional methods for determining source contributions and mixing relations in contrast 87sr 86sr and 234u 238u remain unfractionated under these conditions and compositions at a given site remain constant differences in sr and u isotopic signatures between individual sites can be related by simple two or three component mixing models results indicate that surface flow constituting the refuge s irrigation source consists of a 65 25 10 mixture of water from two distinct regionally sourced carbonate aquifer springs and groundwater from locally sourced volcanic aquifers within the refuge contributions from the irrigation source and local groundwater are readily determined and depend on proximity to those sources as well as water management practices

radiogenic and stable sr isotope ratios 87 sr 86 sr δ 88 86 sr as tracers of riverine cation sources and biogeochemical cycling in the milford sound region of fiordland new zealand this study reports radiogenic sr isotope ratios 87sr 86sr stable sr isotope ratios 88 86sr and major ion concentrations for river rock sediment soil and plant samples collected from the cleddau and hollyford catchments in the milford sound region of fiordland new zealand the catchments primarily drain gabbro but some tributaries access limestone and volcanogenic sediments the goal of the study was to understand controls on riverine 88 86sr values in a landscape with multiple factors that may influence chemical weathering including dense vegetation high rainfall and abundant freshly eroded holocene fluvio glacial and landslide debris rivers draining gabbro have higher 88 86sr values than bedrock by as much as 0 14 and the 88 86sr values strongly correlate with molar ca sr ratios r2 0 69 leaching of rocks and sediment reveals no evidence for the preferential dissolution of minerals having high 88 86sr values and ca sr ratios in stream sr isotope fractionation seems unlikely because comparison against 87sr 86sr and ca sr ratios demonstrates that riverine 88 86sr values conservatively trace water mass mixing the riverine data are best explained by the input of soil water which is distinct from potential bedrock end members i e silicates and carbonates based on 88 86sr but indistinguishable in terms of ca sr and 87sr 86sr while strontium isotope fractionation during secondary mineral formation and pedogenesis is possible clay mineral formation is minor and most soils are poorly developed instead soil water 88 86sr values more likely reflect plant uptake plant samples yielded a wide range of 88 86sr values but on average they are lower than those for bedrock consistent with the expectation that plants preferentially incorporate lighter sr isotopes mass balance constraints together with 87sr 86sr ratios indicate that soil water 88 86sr values are 0 30 higher than bedrock 88 86sr values and mixing calculations show that the plant fractionated soil water pool contributes 27 of the riverine sr for tributaries accessing limestone and volcanogenic sediments ca sr and 87sr 86sr ratios appear consistent with two component mixing between silicate and carbonate weathering but 88 86sr values reveal a third contribution from soil water inputs similar to gabbro catchments the results of this study suggest that sr isotopes behave conservatively during water mass mixing and stream transport but non conservatively in soil where plant uptake can elevate soil water 88 86sr values relative to bedrock plant uptake or related biogeochemical processes such as ion exchange on organic matter surfaces also appear to modify soil water ca sr ratios many studies use 87sr 86sr and ca sr ratios to apportion riverine solutes between silicate and carbonate weathering but ca sr ratios may be non conservative in densely vegetated areas the stable sr isotope tracer shows promise for resolving riverine cation sources as well as effects from biological cycling

effect of calcite precipitation on stable strontium isotopic compositions insights from riverine and pool waters in a karst cave abstract radiogenic and stable sr isotope ratios 87 sr 86 sr 88 86 sr serve as potential tracers for evaluation of weathering sources and associated physicochemical processes in terrestrial environments despite carbonate weathering sourcing two thirds of the total continental sr flux to the ocean however few attempts have been aimed at studying stable sr isotope fractionation in carbonate dominated aquifers here we present a monthly resolved monitoring dataset of major ion concentrations and sr isotope ratios for karst riverine and pool waters at the luofang cave in the central china to understand the potential controls responsible for water 88 86 sr compositions under various climatic conditions with the exception of some pool waters in the dry period significantly heavier 88 86 sr were detected in the riverine and pool waters 0 20 to 0 42 compared to bedrock 88 86 sr 0 24 to 0 28 which can t be interpreted solely by lithology a sequential leaching experiment of the local soils suggests limited stable sr isotope fractionation during incongruent silicate mineral dissolution local plant utilization and biological activity in the soil overlying the cave are possible processes for causing the observed heavier 88 86 sr in cave water however air partial pressure of co 2 in cave monitoring water ph and sr isotopic mass balance calculations suggest that plant utilization is unlikely to be the primary control on the heavier water 88 86 sr on the other hand significant stable sr isotope fractionation was found between the cave dripping waters and calcite precipitates and the 88 86 sr car aq was estimated to be 0 15 0 07 2sd precipitation of secondary calcites might be a potential process responsible for the heavier 88 86 sr in the waters the negative correlation between 88 86 sr and sr na ratios in the cave waters is consistent with a scenario of preferential incorporation of the light sr isotope by solid phase furthermore by combining the calcite saturation states and water ph our results suggest that calcite precipitation is the most likely process controlling 88 86 sr compositions in cave water we demonstrate that secondary calcite precipitation in carbonate dominated catchments could be important in controlling the riverine water 88 86 sr compositions

88sr 86sr fractionation in inorganic aragonite and in corals conflicting results have been reported for the stable sr isotope fractionation specifically with respect to the influence of temperature in an experimental study we have investigated the stable sr isotope systematics for inorganically precipitated and biogenic coral aragonite natural and laboratory cultured inorganic aragonite precipitation experiments were performed from natural seawater using the co2 diffusion technique the experiments were performed at different temperatures and different carbonate ion concentrations 88sr 86sr of the inorganic aragonite precipitated in the experiments are 0 2 lighter than seawater but showed no correlation to the water temperature or to co32 concentration similar observations are made in different coral species cladocora caespitosa porites sp and acropora sp with identical fractionation from the bulk solution and no correlation to temperature or co32 concentration the lack of 88sr 86sr variability in corals at different environmental parameters and the similarity to the 88sr 86sr fractionation in inorganic aragonite may indicate a similar sr incorporation mechanism in corals skeleton and inorganic aragonite and therefore the previously proposed rayleigh based multi element model gaetani et al 2011 cannot explain the process of sr incorporation in the coral skeletal material it is proposed that the relatively constant 88sr 86sr fractionation in aragonite can be used for paleo reconstruction of seawater 88sr 86sr composition the seawater 88sr 86sr ratio reconstruction can be further used in calcite samples to reconstruct paleo precipitation rates

evidence for stable sr isotope fractionation by silicate weathering in a small sedimentary watershed in southwestern taiwan abstract radiogenic sr isotopes 87 sr 86 sr are robust for provenance identification in hydrology affected mainly by the age of background lithologies and the degree of chemical weathering however there is limited knowledge concerning the fractionation mechanism of stable sr isotopes 88 sr 86 sr in rivers in this study river water was collected on a weekly to monthly basis throughout dry and wet seasons furthermore to study the variations of radiogenic and stable sr isotopes during intense weathering a major flooding event 2000 mm precipitation in three days typhoon morakot water was captured within a small drainage catchment system 161 km 2 along the hou ku river in southwestern taiwan for a better constraint on the end member compositions bedload sediments suspended particles and several host rocks were sampled for a systematic investigation the carbonate and silicate phases of these solids were chemically separated dissolved major elements indicate that the watersheds were predominated by silicate weathering stable sr isotopes show no significant variation 88 sr 0 24 0 31 temporally and spatially with an average of 0 28 additionally all solids showed lower 88 sr values than the river water while the host rocks had higher 88 sr values 88 sr 0 20 0 26 than the residual weathering products 88 sr 0 08 0 22 indicating preferential leaching of heavy sr into the hydrosphere and leaving light sr in the residual solids results of laboratory acid leaching experiments reveal that dissolution of high 88 sr value minerals occurred at an early stage of weathering the variation of weathering intensity does not alter stable sr isotopes in silicate weathering dominated river water which contains higher stable sr isotopes than the associated sediments the silicatic sedimentary rocks preferentially released higher stable sr isotopes into the hydrosphere during chemical weathering thus leaving lower stable sr isotopes in the residual solids

ca sr and ba stable isotopes reveal the fate of soil nutrients along a tropical climosequence in hawaii abstract nutrient biolifting is an important pedogenic process in which plant roots obtain inorganic nutrients such as phosphorus p and calcium ca from minerals at depth and concentrate those nutrients at the surface here we use soil chemistry and stable isotopes of the alkaline earth elements ca strontium sr and barium ba to test the hypothesis that biolifting of p has been an important pedogenic process across a soil climosequence developed on volcanic deposits at kohala mountain hawaii the geochemical linkage between these elements is revealed as generally positive site specific relationships in soil mass gains and losses particularly for p ba and ca using the ratio of immobile elements titanium and niobium ti nb to link individual soil samples to a restricted compositional range of the chemically and isotopically diverse volcanic parent materials at sites where p is enriched in surface soils relative to abundances in deeper soils the isotope compositions of exchangeable ca sr and ba in the shallowest soil horizons 10 cm depth at those sites is consistently heavier than the volcanic parent materials the isotope compositions of exchangeable ca and sr trend toward heavier compositions with depth more gradually reflecting increasing leakiness from these soils in the order ba

introducing δ88 86sr analysis in archaeology a demonstration of the utility of strontium isotope fractionation in paleodietary studies abstract isotopic methods are widely used in archaeology to investigate paleodiet here we present a new method to identify trophic level in archaeological human populations and to investigate paleodiet we demonstrate that strontium isotope compositions reported as 88 86sr vary in a mass dependent manner with increasing trophic level and can elucidate paleodiet in archaeological human populations we present new mass dependent strontium isotope data from tooth enamel and bone from individuals buried during the late intermediate period c ad 1000 1300 in the large cemeteries of chiribaya alta chiribaya baja san geronimo and el yaral in the ilo and moquegua valleys of southern peru we compare these data to radiogenic strontium isotope data 87sr 86sr and light stable isotope data 15ncol and 13ccol from the same individuals to investigate geologic variability in strontium sources as well as marine food consumption among the chiribaya our results demonstrate the utility of measurements of strontium isotope fractionation as a new tool for archaeological investigation of paleodiet importantly this new technique can be used to generate paleodietary 88 86sr and paleomobility 87sr 86sr data from the same specimen minimizing destructive analyses of invaluable archaeological material and provides a new way to examine paleodiet through hydroxyapatite which is particularly important when collagen is poorly preserved

dependence of the flexural rigidity of the continental lithosphere on rheology and temperature while the first order mechanical properties of oceanic and continental lithosphere are well defined and explain the observed increase in lithospheric flexural strength with thermal age the temporal variation of continental flexural rigidity following loading and its dependence on lithospheric composition and temperature structure is only just beginning to be appreciated we describe here the results of a quantitative theological model in which laboratory determined rock deformation data and transienttemperature distributions resulting from intra plate basin formation within continental interiors have been integrated continental flexural rigidity is shown to be controlled by crustal thickness lithospheric thickness through the temperature structure and the interaction of these factors during basin formation for thermally young lithosphere the flexural rigidity is dominated by the quartzo feldspathic theology of the crust while for the thermally older lithosphere it is dominated by the olivine rheology of the mantle flexural data through thermo mechanical models of lithospheric deformation provide a powerful constraint on both the transient and steady state temperature structure of the lithosphere

intraplate lithosphere strength and heat flow the magnitude levels of intraplate stresses and the strength of intraplate lithosphere are critical for understanding the mechanisms of intraplate deformation the decay of stress in the ductile lower lithosphere and its resulting amplification in the brittle upper lithosphere constitute an important mechanism for providing stress levels in the upper brittle lithosphere sufficient for fracture such stress transfer and the subsequent lithosphere deformation are controlled by lithosphere rheology a model is examined here for the deformation of viscoelastic lithosphere with temperature and stress dependent rheology subjected to laterally applied stress for different lithosphere thermal structures the geotherm is found to be of critical importance in determining the strength of the lithosphere and the extent of the resulting lithosphere deformation for lithosphere with heat flow 75 mw m 2 0 25 kbar tensile stress is sufficient to cause geologically significant deformation while for compressional deformation either greater stress levels or a hotter lithosphere are necessary

post buckling relaxation of an elastic layer and its geological relevance insights from analogue experiments in pure shear abstract by physical modelling we investigated the buckling and post buckling behaviour of an elastic layer hosted in a viscous medium as analogue of the elastic response of crustal rocks the experiments were performed by embedding thin elastic layers of finite length in a linear viscous medium and in two successive stages a first stage of layer parallel shortening in pure shear followed by a second stage of post buckling unfolding with zero velocity at the bounding walls the experimental results show that the fold wavelength varies inversely with applied piston velocity following an exponential function for which the higher the piston velocity the higher the number of waves with cessation of layer parallel shortening the buckled layers underwent post buckling relaxation in response to the elastic strain accumulated during the buckling stage such relaxation reduces the number of waves by successive elimination of the lower amplitude folds the relaxation process gives rise to larger folds of higher amplitude in the centre of the elastic layer concomitantly with the production of a train of gentle folds in the outer domains by outward motion of the ends of the elastic layer this means that relaxation is more efficient away from the central domain comparison of our experimental results with available analytical solutions reveals significant discrepancies finally we suggest that a similar process of relaxation of the elastic strain although of lower amplitude may explain the late stage open folding and the formation of overlying extensional basins observed in past orogens like the caledonides in western norway

late orogenic extension in mountain belts insights from the basin and range and the late paleozoic variscan belt from two examples of orogenic domains some general mechanisms significant of late orogenic tectonic processes in mountain belts are characterized the basin and range province and the variscan belt in the french massif central have both suffered important compressional orogenic crustal thickening and the results of late orogenic processes can be observed in the field both areas are covered by deep seismic profiling providing constraints on the geometry of a crust which has been restored to a normal thickness late orogenic features from the two domains are compared at different scales and their tectonic significance for extension mechanisms is discussed at the scale of the orogenic domains the most prominent tectonic features are the metamorphic core complexes mcc which expose deformed rocks from the middle crust generally affected by high temperature low to medium pressure metamorphism partial melting and widespread granite emplacement in these mcc large scale extensional shear zones present an intense mylonitic deformation characterized by low dipping foliations and pervasive stretching lineations they show a complete evolution from early deep seated ductile deformation generally achieved under high temperature low to medium pressure metamorphism to a late shallow brittle stage characterized by cataclastic deformation the late detachment stage generally controls the development of asymmetrical extensional sedimentary basins filled by continental deposits two main geometries of mcc are defined that are characterized by differing geometry and kinematics of low angle shear zones in the first case two low angle shear zones with opposite vergence develop along the flanks of a roughly symmetrical mcc often one system is dominant over the other the second geometry characterizes asymmetrical mcc bounded by a single normal shear zone which is upwarped during uplift and doming of the core caused by tectonic denudation detailed strain analysis performed in several extensional shear zones shows that the deformation regime is heterogeneous and results from general noncoaxial flow deformation along the shear zones evolves progressively from slight homogeneous pure shear strain to intense heterogeneous noncoaxial shear strain strain distribution within the lower crust is less well constrained by field observation however analogies between cocorp and ecors deep seismic reflection profiles give important constraints on crustal structure wide zones of highly subhorizontally layered lower crust and a flat high amplitude reflection moho characterize both evolved orogenic domains suggesting that major deformations and flow occur within the lower crust during extension a kinematic model involving heterogeneous crustal deformation and regional scale flow fits relatively well with late orogenic structures observed in continental domains a weak hot upper mantle allows large scale flow of lower crust material from zones of deep ductile extension to uplifted domains of upper crustal denudation heterogeneous strain is accommodated by low angle extensional shear zones from localized zones of extension in the brittle crust to ductile lower crust combined pure and simple shear occurs along localized shear zones whereas at the scale of the whole lithosphere deformation nearly corresponds to a vertical pure shear such deformation processes which affect a thick and hot crust seem to be common in both compared domains suggesting that late orogenic extensional processes are slightly dependent of the type of contractional tectonics thus as much in the andean type west american cordilleran belt as in the collision type variscan belt late orogenic processes produced similar extensional features

determination of temperature dependent stable strontium isotope 88sr 86sr fractionation via bracketing standard mc icp ms stable strontium isotopes here 88sr 86sr are introduced as a new member of the nontraditional stable isotopes we have developed a bracketing standard method for the determination of 88 86sr using an axiom mc icp ms and normalizing to strontium srm nbs987 for individual measurements the external reproducibility is better than about 25 ppm 1 rsd for the iapso seawater standard a 88 86sr value of 0 381 0 010 2sem was determined for the first time a temperature dependent strontium isotope fractionation during calcium carbonate precipitation could be shown aragonite samples inorganically precipitated under temperature control between 10 and 50 c revealed a 88 86sr temperature dependency of 0 0054 5 c r2 0 987 in contrast for natural coral samples pavona clavus from a proxy calibration study 23 to 27 c we did determine 0 033 5 c r2 0 955 the processes causing this sixfold stronger temperature dependency for the natural coral samples have to be studied in more detail in future studies in a first approach the different slopes can be interpreted as effects of kinetic fractionation of strontium ions with or without a hydrate shell of 22 to 29 water molecules

middle and late pleistocene paleoscape modeling along the southern coast of south africa abstract changing climates environment and sea levels during the middle and late pleistocene must have had significant impacts on early modern humans and their behavior however many important archaeological sites occur along the current coastline of south africa where the gradual slope of the offshore agulhas bank meant that small changes to sea level height potentially caused significant shifts in coastline position the geographic context of these currently coastal sites would have been transformed by sea level shifts from coastal to near coastal to fully terrestrial to understand human adaptations as reflected in the archaeological deposits of these now coastal sites we need to accurately model coastline position through time here we introduce a paleoscape model as a conceptual tool to ground the records for human behavioral evolution within a dynamic model of paleoenvironmental changes using integrated bathymetric datasets gis and a relative sea level curve we estimate the position of the coastline at 1 5 ka increments over the last 420 000 years we compare these model predictions to strontium isotope ratios from speleothems as an independent test and then compare the coastline predictions to evidence for shellfish exploitation through time both tests suggest our model is relatively robust we then widen our paleoscape model to most of the cape region and compare the predictions of this broadened model to evidence from blombos cave

88 sr 86 sr fractionation and calcite accumulation rate in the sea of galilee abstract this study used the sea of galilee lake kinneret northern israel as a natural laboratory to investigate the fractionation of the stable sr isotope ratio 88 sr 86 sr during precipitation of inorganic primary calcite from the lake s water it was found that the absolute value of the 88 sr 86 sr fractionation factor 88 86 sr increases as a function of calcite accumulation rate 88 86 sr 0 05 to 0 042 log r mol m 2 d 1 where r is the accumulation rate furthermore the 87 sr 86 sr and 88 sr 86 sr ratios in the freshwater and brines that enter the lake were used to calculate the contributions of these sources to the lake sr budget the 87 sr 86 sr and 88 sr 86 sr ratios were measured in primary calcite aragonite shells of live melanopsis lake water and various water sources to the lake while the lake s 87 sr 86 sr ratios are determined by the mixture of freshwater of the jordan river and saline springs the 88 sr 86 sr ratios of the lake reflect a more complex mass balance that includes the effect of isotopic fractionation associated with the precipitation of primary calcite data analysis suggests that long term accumulation of inorganic calcite depleted in the heavy isotope 88 sr results in an increase of the 88 86 sr value of the lake water by 0 05 in contrast to the primary inorganic calcite biogenic aragonite of the melanopsis shells show a rather constant 88 sr 86 sr water caco 3 fractionation of 88 86 sr 0 21 similar 88 86 sr values were reported for the precipitation of coralline and inorganic aragonite from seawater and the precipitation of inorganic calcite from various continental waters the 88 86 sr value of inorganic calcite is modulated by the rate of carbonate precipitation as noted above and shown by precipitation experiments massive precipitation of primary calcite with a wide spread of accumulation rates occurs during the spring phytoplankton bloom in lake kinneret the bloom dictates the degree of calcite saturation in the lake and hence the stable sr isotopic composition of the precipitating calcite the correlation between 88 sr 86 sr and the calcite accumulation rate can be therefore used as a tool to reconstruct environmental and ecological variations in the historical lake by analyzing the 88 sr 86 sr ratio in the primary caco 3 recovered from the lake s sedimentary archives

sea land oxygen isotopic relationships from planktonic foraminifera and speleothems in the eastern mediterranean region and their implication for paleorainfall during interglacial intervals the oxygen and carbon stable isotope compositions of cave speleothems provide a powerful method for understanding continental climate change here we examine the question of the regionality of this isotopic record and its linkage with the marine isotopic record in the eastern mediterranean em region the study presents a new accurately dated 250 kyr 18o and 13c record determined from speleothems of the peqiin cave northern israel its comparison with the continuous 185 kyr isotopic record of the soreq cave speleothems from central israel reveals striking similarities thus a strong regional climatic signal brought about by variations in temperature and rainfall amount is reflected in both cave records low 18o minima in the peqiin profile for the last 250 to 185 kyr period interglacial marine isotopic stage 7 match the timing of sapropels 9 to 7 and are indicative of high rainfall in the em region at these times the combined soreq and peqiin 18o record for the last 250 kyr excellently matches the published globigerinoides ruber g ruber marine 18o record for the em sea with the isotopic compositional difference g ruber speleothems remaining relatively constant at 5 6 0 7 thus establishing for the first time a robust exploitable link between the land and the marine isotopic records the correspondence of low 18o speleothem values and high cave water stands with low g ruber 18o values during interglacial sapropel events indicates that these periods were characterized by enhanced rainfall in the em land and sea regions by use of sea surface temperatures derived from alkenone data as a proxy for land temperatures at the soreq cave we calculate the paleorainfall 18o values and its amounts maximum rainfall and lowest temperature conditions occurred at the beginning of the sapropel events and were followed by decrease in rainfall and increase in temperatures leading to arid conditions the record for the last 7000 yr shows a trend toward increasing aridity and agrees well with climatic and archeological data from north africa and the middle east

accuracy and precision of 88sr 86sr and 87sr 86sr measurements by mc icpms compromised by high barium concentrations barite baso4 is a widely distributed mineral that incorporates strontium sr during formation mass dependent fractionation of sr isotopes occurs during abiotic precipitation of barite and formation of barite associated with biological processes e g bacterial sulfide oxidation sr isotopes in barite can provide provenance information as well as potentially reconstruct sample formation conditions e g saturation state temperature biotic versus abiotic incomplete separation of ba from sr has complicated measurements of sr isotopes by mc icpms in this study we tested the effects of ba in sr sample solutions and modified extraction chromatography of sr using eichrom sr spec eichrom technologies llc usa resin to enable rapid accurate and precise measurements of 88sr 86sr and 87sr 86sr ratios from ba rich matrices sr isotope ratios of sample solutions doped with ba were statistically indistinguishable from ba free sample solutions below 1 ppm ba deviations in both 87sr 86sr and 88 86sr occurred above 1 ppm ba an updated extraction chromatography method tested with barite and ba doped seawater produces sr sample solutions containing 10 100 ppb levels of ba the practice of zr spiking for external mass discrimination correction of 88sr 86sr ratios was also evaluated and it was confirmed that variable zr levels do not have adverse effects on the accuracy and precision of 87sr 86sr ratios in the zr concentration range required to produce accurate 88 86sr values

geodynamic evolution of the continental allochthonous terrane cat of the braganca nappe complex ne portugal the braganca massif in particular its continental allochthonous terrane cat is a keystone in the comprehension of the pre variscan and variscan geodynamic evolution of the eurasian plate in particular of the high grade metamorphic evolution the braganca cat comprises three types of granulites recording quite distinct metamorphic histories and paragneisses with enclosed eclogite boudins it has undergone five characterizable main deformation phases during two orogenic cycles separated by the extensive intrusion of mafic ultramafic layered bodies types 2 and 3 granulites into a pervasively deformed granulitic lower continental crust type 1 granulites geochronological data obtained on high grade metamorphic rocks from braganca and other similar rocks in the variscan fold belt have been typically interpreted in two different ways polycyclical evolution precambrian and paleozoic variscan or monocyclical evolution variscan this second hypothesis is in clear contradiction with field evidence with tectonometamorphic data and even with some geochronological data as shown in this article thus we suggest that the tectonometamorphic evolution of the braganca cat and by comparison of other similar cat in the variscan fold belt took place during two orogenic cycles one precambrian grenvillian pan african cadomian and another one paleozoic variscan

coupled δ44 40ca δ88 86sr and 87sr 86sr geochemistry across the end permian mass extinction event abstract we report high resolution high precision 44 40ca 88 86sr and 87sr 86sr records spanning the permian triassic boundary ptb from the meishan and dajiang carbonate successions in south china the goal of the study was to understand the behavior of ca and sr isotopes during a time period in earth history characterized by severe biological and environmental perturbations including a major mass extinction flood basalt volcanism ocean acidification and sea level fluctuations dajiang displays negative 44 40ca and 88 86sr excursions and invariant 87sr 86sr ratios in the

characterizing nutrient pathways in quebec canada vineyards insight from stable and radiogenic strontium isotopes abstract soils are a crucial interface of earth s critical zone responsible for the biogeochemical cycling of mineral nutrients while the sources of essential nutrients such as ca and sr in plants have been widely studied the processes by which these nutrients are transferred from the soil to the plants is less clear we present new evidence for systematic nutrient fractionation between soils grapes and wines from five vineyards from the quebec terroir canada using the novel stable sr 88 86sr isotope system we coupled this approach with traditional radiogenic 87sr 86sr measurements on the same samples bulk soils labile fraction of these soils whole grapes and wines from five vineyards from the quebec terroir canada to ensure that variations in 88 86sr values were provoked by processes involved in sr transfer instead of mixing between different sources the 88 86sr values generally decrease from the bulk to the labile fractions of the soils to the grapes a decrease in the difference between the soil fractions 88 86srbulk labile with increasing 88 86sr values in the labile fraction is interpreted to reflect increasing pedogenic mineral precipitation and higher soil fertility the depleted 88 86sr values of the grapes are consistent with a preferential uptake of lighter isotopes by plants this effect is magnified in soils showing higher secondary mineral precipitation an increase in the 88 86sr values from the grapes to the wines reflects the separation of the skin seeds and the juice pulp enriched in 88sr in the winemaking process this mixing relationship is supported by a correlation between the sr concentrations and the 88 86sr values of the wines and grapes these findings suggest promising new applications of stable sr isotopes values for studying soil fertility and the impact of nutrient availability for plant growth in agricultural ecosystems as well as the impact of the maceration processes in the production of wine the overall similarity of 87sr 86sr ratios of the labile soil fractions grapes and wines from the same vineyard support the hypothesis of a same sr source from the soil solution to its transfer to the grape and wine and confirm the potential of the 87sr 86sr ratios as a proxy for geographic provenance of wine however slightly lower 87sr 86sr ratios in the grape pulps by 0 00040 on average compared to the skins and seeds suggest that the sources of nutrients available for plant uptake vary during the vegetative cycle the grape seeds and skins formed in the early growth cycle are characterized by rapid growth due to enhanced rhizosphere activity enhanced mineral dissolution providing higher nutrient levels the enhanced mineral solubility results in higher 87sr 86sr ratios in the skin and seeds derived from enhanced dissolution of 87sr enriched silicate minerals in contrast the pulp develops later in the growth cycle when rhizosphere activity and mineral solubility is reduced resulting in a lesser contribution from silicate minerals and thus reflect a higher proportion of dissolved carbonate contributing to the lower 87sr 86sr ratios of the pulps

rheological and tectonic modeling of salt provinces abstract technological improvements and a more rigorous research approach have led the petroleum industry to renew and expand its interest in physical modeling of faulting associated with halokinesis salt tectonics and the formation of structural hydrocarbon traps can be reproduced in models using viscous polymers for the substratum and frictional plastic granular materials for the overburden the fault patterns simulated in these dynamically scaled models are remarkably similar to those in depth converted seismic sections scale models are therefore useful for generating new concepts and for reconstructing the structural evolution of hydrocarbon traps although even unsealed models may help generating ideas the full transfer of quantitative data requires that models be dynamically scaled to their natural prototypes previously published scaling theory for salt tectonics has erroneously assumed fluid behaviour of the overburden this paper provides a sound scaling approach for geological deformations involving brittle overburdens on ductile substrata rheological data from overburden rocks and salt are compiled and compared to model rheologies using dimensions of laboratory analogs and other intrinsic material properties scaling approaches are compared and rules are formulated for achieving dynamic similarity in models of salt tectonics including those with synkinematic sedimentation

conodont apatite δ88 86sr and δ44 40ca compositions and implications for the evolution of palaeozoic to early mesozoic seawater abstract we present high precision tims double spike stable isotope measurements of both 44 40 ca and 88 86 sr together with radiogenic 87 sr 86 sr ratios determined from conodont apatite these data represent five intervals ranging from the early ordovician to late triassic the conodont 44 40 ca values relative to nist 915a range from 0 47 to 0 15 with an apparent shift to more positive values between the early silurian and late devonian early carboniferous similar to the brachiopod based marine 44 40 ca record farkas et al 2007a we calculated a 44 40 ca seawater bio apatite fractionation factor of about 1 9 which allowed us to reconstruct a palaeo seawater 44 40 ca record from bio apatites despite a slightly positive offset of about 0 2 to 0 5 the 44 40 ca record obtained from bio apatites is consistent with the previously reported 44 40 ca seawater record inferred from carbonates we find that unlike the carbonate 44 40 ca records the 88 86 sr measurements from conodont apatite show unexpectedly large variations up to 1 with ratios ranging from 0 6 to 0 3 these reconnaissance data reveal a reasonable correlation between 88 86 sr and radiogenic 87 sr 86 sr r 2 0 60 n 13 p 0 002 suggesting that the controls from differential weathering regimes and or continental crustal compositions buffered ancient seawater compositions

strontium stable isotopes fractionate in the soil environments abstract this study shows that the stable isotopic composition of strontium the 88sr 86sr ratio expressed as 88 86sr value relative to the nbs987 standard varies significantly in sedimentary terrestrial environments the abundances of 86sr 88sr isotopes were analyzed by mc icp ms nu plasma all studied rocks and waters show 88 86sr values that are distinctly different from the measured nbs987 standard yielding 0 01 0 05 all errors are reported as 2 modern corals from the northern gulf of aqaba red sea yielded significantly different value than seawater 88 86sr 0 22 0 07 compared to 0 35 0 06 respectively in an excellent correlation with the 88 86sr analyses reported by fietzke and eisenhauer fietzke j eisenhauer a 2006 determination of temperature dependent stable strontium isotopes 88sr 86sr fractionation via bracketing standard mc icp ms geochm geophys geosyst 7 no 8 on other coral samples all carbonate samples that originated in the marine environment corals porites and acropora from the northern gulf of aqaba cretaceous limestone and runoff from the judea mountains as well as lacustrine evaporitic aragonite dead sea and red sea and atlantic seawater yield an average 88 86sr value of 0 26 0 1 on the other hand secondary materials products of chemical weathering from the terrestrial environment of the judea mountain such as terra rossa soil and speleothem calcite that derives its sr from the above lying soil yielded significantly lower 88 86sr value of 0 17 0 06 this indicates that strontium isotopes fractionate in the soil environment calling for a possible development of strontium isotopes as a tracer for processes of chemical weathering and pedogenesis

basin development by relaxation of a buckled elastic layer insights from laboratory experiments abstract contrary to the classical modes of basin formation based on far field stresses here we report on a new mechanism of basin generation by near field internal stresses based on scaled laboratory experiments basins forming atop a relaxing buckled elastic layer following a far field compressional event this investigation builds on the works by marques and podladchikov 2009 buckling of elastic layer between viscous and brittle layers and marques and mandal 2016 relaxation of elastic buckles in a viscous medium but the objective is different it is basin formation by relaxation of a buckled elastic layer sandwiched between viscous below and brittle above layers when the model is horizontally constrained two types of basins can form by the growth of amplitude and wavelength due to elastic relaxation of the buckles only vertical motion allowed narrow basins atop the growing antiforms outer arc extension and deep basins in the sinking synforms if horizontal extension is allowed then relaxation is not solely by increase in amplitude and wavelength it is also by horizontal relaxation i e the edges of the elastic layer can move towards the walls so producing model scale extension which widens the basins by extension in the brittle layer an increase in the thickness of the brittle layer makes it stronger and so hampers basin formation the new model can be used to explain the formation of post orogenic basins by near field stresses without recourse to the classical mechanism of extension produced by whole plate tensional far field stresses

the sahara east mediterranean dust and climate connection revealed by strontium and uranium isotopes in a jerusalem speleothem this paper explores the potential of sr and u isotope systems in speleothems as tracers of eolian dust transport and hydrological conditions the study focuses on a speleothem from jerusalem spanning the past 220 kyr this speleothem provides a precisely dated record of dust flux from the sahara to the east mediterranean enhanced dust flux and terra rossa soil development are reflected by elevated 87sr 86sr ratios in the speleothem 0 7082 0 7086 while lower 87sr 86sr ratios 0 7078 indicate higher contribution of the local bedrock due to low dust flux and low soil accumulation the strontium isotope system in the speleothem is a robust monitor of the sahara monsoon modulated climate since dust uptake is related to development or reduction in vegetation cover of sahara soil the 234u 238u activity ratios in the speleothem range between 1 12 and 1 0 the high activity values may indicate selective removal of 234u from the soil while the low values converge to the bedrock the migration of 234u to the cave reflects mainly the regional hydrological conditions that are modulated by the north atlantic mediterranean climate system thus the speleothem provides a combined record of the monsoon north atlantic climatic systems long term stability in glacial 87sr 86sr ratios 0 7083 0 0001 over the past 220 kyr suggests an overall similarity in eolian dust sources and uniformity in the synoptic conditions that dominate the dust storm tracks during glacial periods

enrichment of 88 sr in continental waters due to calcium carbonate precipitation abstract 88 86sr data published over the last few years suggest that continental waters are enriched with 88sr as compared to the rocks in their drainage basins in an attempt to understand this phenomenon this study established the fractionation in the 88sr 86sr ratio during precipitation of continental carbonates i e carbonates precipitated on land from surface pedogenic or ground waters and evaluated the contribution of this process to the 88sr enrichment in rivers for this stable and radiogenic sr isotopes 88sr 87sr and 86sr were measured in calcite samples and their precipitating waters collected in various continental environments such as soil cave streams and groundwater the results indicate that continental carbonates are 88sr depleted relative to their precipitating waters placing them as one of the most 88sr depleted reservoirs on earth the average difference in 88 86sr values between waters and solid caco3 tufas or speleothems that they precipitate is carb water 0 218 0 014 1sd an even larger fractionation e carb water 0 285 0 02 was measured in groundwater with particularly high carbonate alkalinity and high carbonate precipitation rate that depleted 65 of the sr in the groundwater resulting in substantial 88sr enrichment in the residual dissolved sr sr 88 86 0 656 results also suggest that pedogenic carbonate precipitation in soil profile removes 50 85 of the sr from the recharging soil water thereby increasing the 88 86sr value of the soil water from 0 18 to 0 3 0 6 similar 88sr enrichment was observed in drip water from a karst cave a maximum removal flux of sr into continental carbonates of about 20 gmol sr y 1 is required to yield the reported 88sr enrichment in global rivers sr 88 86 0 32 relative to their rock sources when using the fractionation factor derived in this study carb water 0 218 and the published 88 86sr composition of marine carbonates of 0 16 this surprisingly large flux requires that 40 of the originally weathered sr should co precipitate with continental carbonates this calculation may suggest that caco3 precipitation is a significant mechanism in the continental sr cycle it is possible however that other mechanisms such as sr uptake by plants or incongruent weathering of silicates could also contribute to the riverine 88sr enrichment alternatively the average 88 86sr value of marine carbonate rock sections undergoing weathering is higher than suggested in current literature it is concluded that additional 88 86sr data on marine carbonate rock sections should be collected to resolve the enigma of the high value of riverine 88 86sr

spatial variations of sr nd isotopic ratios mineralogical and elemental compositions of cryoconite in an alaskan glacier to understand the geological origins of minerals in cryoconite and the nutrients sources for microbes on glaciers we analyzed the sr nd isotopic ratios of the four mineral fractions in cryoconites including saline carbonate phosphate silicate and the organic fraction obtained from gulkana glacier in alaska the isotopes in the silicate mineral fraction exhibited spatial variation within the glacier 87sr 86sr 0 704533 0 709563 end 0 16 0 to 0 5 which can be explained by the different mixing ratios of the two distinct sources one of the sources is lateral and terminal moraines or soil and the other is the medial moraine of the glacier the minerals in the cryoconite at the lower sites in the glacier are likely derived from the former source whereas those at the upper sites are from latter sources the mineralogical and elemental compositions also support mixing of the silicate minerals from the two local sources the sr isotopic ratios of the organic fraction also showed spatial variation on the glacier in the middle sites a trend similar to those of the phosphate fraction the results suggest that the organic matter is mostly the byproducts of microbes using the phosphate minerals as a nutrient source

control of folding by gravity and matrix thickness implications for large scale folding 1 we show that folding of a non newtonian layer resting on a homogeneous newtonian matrix with finite thickness under influence of gravity can occur by three modes 1 matrix controlled folding dependent on the effective viscosity contrast between layer and matrix 2 gravity controlled folding dependent on the argand number the ratio of the stress caused by gravity to the stress caused by shortening and 3 detachment folding dependent on the ratio of matrix thickness to layer thickness we construct a phase diagram that defines the transitions between each of the three folding modes our priority is transparency of the analytical derivations e g thin plate versus thick plate approximations which permits complete classification of the folding modes involving a minimum number of dimensionless parameters accuracy and sensitivity of the analytical results to model assumptions are investigated in particular depth dependence of matrix rheology is only important for folding over a narrow range of material parameters in contrast strong depth dependence of the viscosity of the folding layer limits applicability of ductile rheology and leads to a viscoelastic transition our theory is applied to estimate the effective thickness of the folded central asian upper crust using the ratio of topographic wavelength to moho depth phase diagrams based on geometrical parameters show that gravity does not significantly control folding in the jura and the zagros mountains but does control folding in central asia applicability conditions of viscous and thin sheet models for large scale lithospheric deformation derived in terms of the argand number have implications for the plate like style of planetary tectonics

collapse of a hercynian tibetan plateau into a late palaeozoic european basin and range province the large width the importance of crustal shortening and the likelihood of thick crust in the late palaeozoic hercynian or variscan belt of southern europe suggest a tectonic evolution analogous to the evolution of the tibetan plateau and its neighbouring himalaya1 and of the altiplano and other high plateaux of the andes here we extend dewey and burke s analogy1 of the hercynian chain with tibet to include the subsequent stage of pervasive normal faulting and crustal extension and thinning which characterize the active tectonics of tibet parts of the high andes and the basin and range province of western north america it appears that normal faulting and rifting also characterize the late palaeozoic tectonic activity of the hercynian chain

radiogenic and stable strontium isotopes in provenance studies a review and first results on archaeological wood from shipwrecks abstract different approaches are used to study wood provenance but most of them are based on tracers in wood that are generally controlled by climatic factors the strontium isotopic ratio 87 sr 86 sr in trees and soils is related to the signature of the local bedrock despite being used in diverse archaeological studies sr isotopes have rarely been used to trace the provenance of archaeological wood and especially wood from shipwrecks in addition recent analytical advances have allowed the detection of mass dependent fractionation of sr isotopes during biogeochemical processes as reflected in the variation of 88 86 sr values between different environmental materials the 88 86 sr values could be used in conjunction with the 87 sr 86 sr isotope ratio to improve constraints on the sources of sr in the archaeological materials being studied this paper discusses the potential and limitations of using both of these sr isotope ratios to trace the provenance of wood from shipwrecks we review the 87 sr 86 sr and 88 86 sr variations in rocks waters soils plants and other living organisms and discuss how to determine the local sr isotopic signature of potential sites we also compile a list of known wood post mortem modifications in seawater possible implications in terms of the modification of the original sr isotope ratios of wood during storage in seawater are illustrated through preliminary observations this paper points out some limitations and perspectives for using sr isotopes in provenancing wood from shipwrecks and suggests future research to test and apply this approach for tracing the origin of archaeological wood

high temperature strontium stable isotope behaviour in the early solar system and planetary bodies abstract this study presents comprehensive strontium stable isotope 88sr 86sr data measured by multiple collector inductively coupled plasma mass spectrometry mc icp ms for a suite of carbonaceous chondrites differentiated meteorites lunar martian and terrestrial samples carbonaceous chondrites comprise a mixture of refractory inclusions and chondrules that have light 88sr values between 0 35 to 0 05 and matrix material that possesses a heavy 88sr composition of 0 65 confirming the results of earlier studies consequently bulk carbonaceous chondrites are relatively heterogeneous in composition ranging from 0 12 to 0 35 most likely reflecting clast matrix variability the light 88sr compositions of the refractory inclusions are consistent with mass dependent fractionation of other refractory elements ca and eu and are most likely produced by non equilibrium fractionation undercooling in the nebula gas during condensation of hibonite from the solar nebula simon and depaolo 2010 stable calcium isotopic composition of meteorites and rocky planets earth planet sci lett 289 457 466 carbonaceous chondrites angrites and martian meteorites have indistinguishable compositions at the level of analytical uncertainty of this study however statistical analysis indicates that melts derived from the earth s mantle have heavier 88sr values than bulk carbonaceous chondrites and martian meteorites but compositions indistinguishable from eucrites 88sr 0 26 0 12 moreover terrestrial basalts and andesites have restricted 88sr values 0 30 0 07 suggesting that mantle melting delivers rather homogenous melts to the earth s surface with respect to 88sr in contrast glasses from evolved terrestrial rocks and lunar basalts extend to very light 88sr values 0 20 the sr stable isotope composition covaries with europium anomaly eu eu as an index of plagioclase fractionation and 88sr can be successfully modelled by the heavy isotopes of sr being preferentially partitioned into plagioclase with a fractionation factor of 1 0007 for 88sr 86sr our results demonstrate that sr stable isotopes may be significantly fractionated at high temperatures and their measurement can provide insights into planetary evolution and magmatic processes

strontium isotopic chemical and sedimentological evidence for the evolution of lake lisan and the dead sea precise strontium isotope ratios combined with chemical analyses and sedimentological information are used to monitor the water sources and the evolution of the dead sea and its late pleistocene precursor lake lisan 70 18 kyr b p the materials analyzed include bulk aragonite water leached soluble salts and residual aragonite and gypsum from the lisan formation in the perazim valley near the sw shore of the dead sea the residual aragonite and the associated soluble salts display systematic fluctuations in 17sr86sr ratios between 0 70803 and 0 70806 and from 0 70805 to 0 70807 respectively in individual soluble salt residual aragonite pairs the soluble salt displays a higher 87sr86sr ratio gypsum samples yield 17sr86sr ratios similar to the soluble salts from adjacent layers in the section this shows that in individual samples the source of sr in aragonite was distinct from that in soluble salts and the gypsum the sterility of the lisan sediments their strictly nonbioturbated fine lamination and their high content of chloride salts indicate that lake lisan was a saline or even hypersaline water body in the absence of alternative sources of hco3 and s042 the abundance of primary aragonite and gypsum in the lisan column reflects an import of very large volumes of freshwater into the otherwise saline lake resulting in a density stratification of this water body the history of the upper water layer and that of the lower brine is reflected in the chemical and strontium isotope composition of the aragonite and in that of the associated soluble salts and in the gypsum samples respectively whereas the bicarbonate and much of the ca2 required for aragonite crystallization were supplied by the freshwater the complementary ca2 and sr 2 were added by the lower brine the upper water layer of lake lisan acted as a so42 capacitor during the lake s rise periods it was removed therefrom as prominent gypsum beds upon climatic induced drier period mixing or even complete overturn of the lake the evolution of lake lisan took place between two distinct modes the first was characterized by an extensive supply of freshwater and resulted in a rise of the lake s level a density layered structure and precipitation of aragonite the second mode was marked by a diminishing freshwater input resulting in mixing or complete overturn of its water and precipitation of gypsum these two modes reflect the climatic evolution of the region in the late pleistocene which fluctuated between drier and wetter periods the transition to the holocene is accompanied by the dry up of lake lisan and its contraction to the present dead sea

calcium isotopes in the marine environment and the oceanic calcium cycle abstract a systematic investigation of 44 ca 40 ca ratios in the oceanic ca cycle indicates that the average ca isotopic composition of input and output are quite different suggesting that the present ocean is not in a steady state our data show that sea water has uniform 44 ca 40 ca as expected from the long residence time of ca in the oceans it also exhibits the heaviest isotopic composition among all samples measured consistent with recent results by skulan et al 1997 and must be maintained at this value by strong biogenic isotope fractionation during the precipitation of caco 3 our measurements show that the riverine input is variable the most radiogenic river waters we have measured lowest 44 ca 40 ca are from ganges tributaries which also have high 87 sr 86 sr although there does not appear to be a systematic correlation between ca and sr isotopic compositions based on available data there is also significant isotopic variability among samples of caco 3 precipitated from the present ocean with coccolith oozes showing the most highly fractionated isotopic values relative to seawater among foraminifera ca isotopes exhibit species dependent fractionation effects but also appear to display systematic temperature dependent fractionation within inidividual species

reassessing the stable δ88 86sr and radiogenic 87sr 86sr strontium isotopic composition of marine inputs the stable strontium isotope system 88 86sr has recently been suggested to be a suitable proxy for determining variations in the strength of the marine carbonate system the principal output flux of oceanic sr however in order to be able to interpret carbonate driven variations in 88 86srseawater a robust understanding of 88 86srinput is required surprisingly only a limited amount of 88 86sr data currently exists for rivers and hydrothermal fluids thus this study assesses the variability of 88 86sr and 87sr 86sr in global rivers hydrothermal fluids and porewaters as well as minor marine sr sources such as continental dust rainwater and glacial ice our analyses broadly confirm the findings of krabbenhoft et al 2010 and reveal flux weighted 88 86srriverine and 87sr 86srriverine compositions of 0 32 and 0 71299 respectively the hydrothermal fluids analysed in this study are consistent with an end member 88 86srhydrothermal composition that is the same as the oceanic crust at 0 24 although three samples that display 88 86sr compositions offset from the seawater hydrothermal mixing trend suggest that the precipitation of alteration phases such as anhydrite may drive 88 86srhydrothermal to higher values porewater fluids obtained from sediment cores in the atlantic and pacific oceans have 88 86sr compositions within error of seawater 0 39 implying that the diagenetic flux of sr may not significantly affect the 88 86sr composition of seawater continental loess samples have 88 86sr compositions that are consistently lighter than or equal to terrestrial silicates with their tendency to lower values thought to reflect the preferential removal of heavier sr isotopes into solution during weathering finally rainwater and glacial ice samples have 88 86sr compositions that are also isotopically lighter than their associated water sources a factor that may be attributed to interaction with isotopically light loess and additional sr contributions from the bedrock together the principal marine inputs define flux weighted oceanic 88 86srinput and 87sr 86srinput compositions of 0 32 and 0 71161 these values are consistent with an elevated supply of riverine sr to the oceans due to increased post glacial weathering but require the enhanced weathering of exposed carbonate shelves during glacial periods or significant changes in the rate of carbonate burial to match observed changes in the 87sr 86sr ratio of seawater our results confirm that providing a diagenetically robust proxy can be found the 88 86sr and 87sr 86sr isotope systems should provide a useful proxy for investigating changes in the marine carbonate system through time

diagenesis in live corals from the gulf of aqaba i the effect on paleo oceanography tracers abstract the effect of early diagenesis on trace element abundance in coral skeleton was studied in live coral heads porites from the nature reserve reef nrr elat gulf of aqaba northern red sea petrography of the corals shows diagenetic features of dissolution recrystallization and secondary aragonite precipitation pore filling which are most extensive in the oldest part of the coral coral porewaters were extracted with a special setup and were analyzed for chemical composition the total alkalinity and sr deficit in pore water as compared to reef water is consistent with both precipitation of secondary aragonite and recrystallization of primary skeleton the present rate constant of pore filling by secondary aragonite was estimated by a water replacement experiment to be 0 0015 y 1 which equals to pore filling rate of 1 5 0 3 kg aragonite per year the corals show clear seasonal fluctuations in sr ca ratios that are interpreted as reflecting changes in sea surface temperature sst yet the secondary aragonite is characterized by a significantly higher sr ca ratio than the average ratio in primary aragonite thus measuring a mixed sample of pristine and secondary aragonite may produce erroneous about 2 c lower sst estimates by the sr ca thermometers it appears that the sr ca ratio a major proxy for paleo environmental marine studies is sensitive to subtle pore filling and replacement of the original coral matrix by secondary aragonite in the marine environment

buckling folds of a single layer embedded in matrix theoretical solutions and characteristics in addition to the conventionally known buckling fold which has a basic fold form comprising of single frequency and non decaying amplitudes folds with other fold forms having dual frequencies or decaying amplitudes also exist in nature this research explores whether these three types of buckling folds which have been found in elastic material still exist for visco elastic or pure viscous materials analytical solutions of the fold forms for visco elastic and pure viscous materials are accordingly proposed the theoretical solutions were then examined by conditions including extremely fast or slow strain rates the results reveal the following physical characteristics of buckling fold 1 for the studied materials all three types of fold forms are possible 2 although pure viscous material itself is strain rate dependent a strain rate does not influence the fold form for a viscous layer embedded in viscous matrix 3 given the same competence contrast both the elastic and the viscous materials have the same wavelength versus the lateral shortening relationship and 4 two measures iv and ie representing the effect of strain rate on folding characterized with a range from 0 to 1 are proposed for strain rate dependent cases 2008 elsevier ltd all rights reserved

structural softening of the lithosphere structural softening is a decrease in the amount of stress needed to deform the lithosphere at a particular rate because of its structural reorganization while all true rheological properties remain constant structural softening is fundamentally different than material softening where the decrease in stress is generated by a change in rheological properties with progressive deformation such as grain size reduction resulting from large shearing strain we study structural softening generated by folding of the crust mantle boundary which is a structural instability that inevitably develops during compression of the mechanically layered lithosphere for ductile rheologies the stress decrease represents a decrease of the effective lithospheric viscosity which is proportional to the ratio of stress to lithospheric shortening strain rate we present analytical and numerical results quantifying the decrease in stress and effective viscosity that occur during shortening at a constant rate the decrease in effective viscosity can be up to 10 fold

the late variscan fault network in central northern portugal nw iberia a re evaluation abstract the fault network in central northern portugal especially the fault system with mean strike n25 has been used to help deduce the late palaeozoic dynamics of western europe on the other hand the n80 strike slip fault system was recognized in previous works as late variscan and left lateral but was scarcely mapped and its importance neglected this study shows that the n25 faults were dextral in the late stages of the variscan orogeny and sinistral during the alpine cycle due to pervasive reactivation fault rocks and intrusions are clearly different according to age mostly high temperature quartz infillings but locally muscovite tourmaline and aplite dykes in late variscan times and low temperature cataclasites fault gouges and mesozoic mafic dykes in younger alpine times we dated dextral n45 segments of the n25 fault system because they are less prone to reactivation by the nnw sse alpine compression and can thus preserve the variscan record we used k ar in muscovite concentrates and obtained a minimum age of the analysed faults of ca 312 ma which sets a lower limit to the so called late variscan wrench faulting period the present study shows that the n80 fault set is pervasive and sinistral in central northern portugal and therefore that it only admits one brittle dextral conjugate the n25 fault system both were generated by a maximum compressive stress bearing between n50 and n55 in azimuth we did not find evidence of a variscan sinistral strike slip movement in the n25 fault system and therefore this kinematics is believed to represent only the displacements accommodated during the alpine cycle

strontium isotopes trace biological activity in the critical zone along a climate and vegetation gradient abstract weathering and ecosystem nutrition are intimately linked through the supply of fresh mineral nutrients from regolith and bedrock the geogenic nutrient pathway however the prominence of this link is dependent on the efficiency of nutrient recycling from plant litter the organic nutrient cycle isotope ratios of strontium sr an element that behaves similarly to ca in ecosystems confer two types of information radiogenic sr isotopes inform as to the sources of sr and the degree of weathering while stable sr isotopes constrain partitioning between compartments of the critical zone bedrock water secondary solids and plants to date however neither the reactions nor the mass balance between compartments that fractionate sr isotopes nor the fractionation factors involved are well understood here we present geochemical budgets of sr using radiogenic and stable sr isotopes and ca sr ratios at four sites along a substantial climate and primary production gradient in the coastal mountains of chile we found that sr release through weathering is isotopically congruent and released sr is not strongly isotopically fractionated either during secondary mineral formation or transfer into the exchangeable pool despite this the 88sr 86sr ratio of bio available sr which should reflect the ratio of dissolved sr is higher than that of rock and regolith we propose that this offset is caused by plants while 88sr 86sr in plant organs at the four study sites systematically increased from roots towards their leaves whole plant sr isotope compositions indicate preferential uptake of light sr into plants with a fractionation of up to 0 3 relative to the bio available pool despite this strong biological fractionation 88sr 86sr ratios in bio available sr do not covary with biomass production across our study sites because with greater plant growth sr is recycled more times after release by weathering an isotope neutral process rather the loss of sr from the ecosystem in solid organic material sets the isotope ratio of dissolved or bio available sr organic solids thus appear to constitute a significant export path of elements released during weathering with the removal of solid plant debris reducing the recycling factor of sr and possibly that of other mineral nutrients too

insights into combined radiogenic and stable strontium isotopes as tracers for weathering processes in subglacial environments this study reports stable and radiogenic strontium isotope behaviour in the dissolved load and suspended sediments from the subglacial outflow of the lemon creek glacier juneau ice field alaska over a single melt season in situ measurements discharge total alkalinity ph and conductivity are combined with elemental concentrations x ray diffraction xrd analysis and radiogenic strontium isotope measurements to interpret the variations observed in stable strontium isotopic ratios the stable sr isotope composition 88sr 86sr ratio expressed as 88 86sr of the dissolved load averages 0 31 0 05 and is heavier than both the suspended sediment 0 18 0 03 as well as local bedrocks 0 20 to 0 26 we attribute the enrichment of heavier isotopes in the dissolved load to the uptake of lighter sr isotopes by secondary weathering minerals driving the dissolved load to heavier values x ray diffraction xrd analysis confirms the presence of clays in the suspended sediments and thermodynamic modelling suggests the presence of iron oxy hydroxide phases although it is not possible to completely rule out the effect of dissolution of primary minerals in controlling sr isotopic compositions of the dissolved load our data indicate that the extent of secondary mineral formation likely plays a significant role the preferential weathering of minerals such as biotite consistent with the mineralogical assemblages found in the suspended sediments as well as the potential presence of radiogenic calcites from metacarbonates derived from the yukon tanana terrain may be driving the small seasonal shifts in 87sr 86sr of the dissolved load to more radiogenic compositions from 87sr 86sr dl 0 71048 to 0 710647 using the combination of stable and radiogenic strontium isotopes to investigate weathering processes shows that radiogenic sr isotopes provide information regarding weathering of primary phases while the stable sr isotope data appear to record information regarding the extent of secondary mineral formation where secondary minerals incorporate the light isotopes driving the dissolved load to heavy values

strontium isotope fractionation of planktic foraminifera and inorganic calcite we have investigated the strontium isotope fractionation 88 86srcarb aq between inorganic calcite and aqueous sr2 ions by precipitation experiments at a constant temperature of 25 c and precipitation rates r ranging from 102 3 to 104 2 mol m2 h strontium isotope ratios were measured using the 87sr 84sr double spike technique it was found that strontium isotope fractionation in these calcites is strongly dependent on the precipitation rate view the mathml source the measured 88 86sr values are significantly correlated with previously measured 44 40ca and sr ca values of the same calcite samples 88 86srcarb aq 0 18 44 40cacarb aq 0 01 view the mathml source the slope of 88sr 86sr versus 44ca 40ca fractionation is 0 18 0 04 and compatible with a kinetic fractionation during dehydration of the strontium and calcium ions but not with isotope fractionation in a diffusive boundary layer using published equilibrium 44 40cacarb aq and view the mathml source values we estimate the equilibrium isotope fractionation of strontium to be very close to zero 88 86sreq carb aq 0 01 0 06 this estimate is confirmed by strontium isotope values of natural inorganic calcites that precipitated very slowly in basalts of the ocean crust the results from the inorganic calcites are used to explain strontium isotope fractionation of planktic foraminifera specimens of two warm water species globigerinoides ruber and globigerinoides sacculifer were picked from the holocene section of a caribbean sediment core we found no significant difference in 88 86sr between the two species in addition g ruber specimens from marine isotope stage 2 in the same core show 88 86sr values identical to the holocene specimens the strontium isotopes of both foraminifera species are strongly fractionated 88 86srcarb aq 0 248 0 005 when compared to published data of other major marine calcifiers applying the results from the inorganic precipitation experiments we find that the strong foraminiferal strontium isotope fractionation can be explained by calcification in a largely open system at high precipitation rates comparable in magnitude to rates known from scleractinian reef corals this interpretation is in good agreement with the kinetic calcification model for planktic foraminifera by kisakurek et al 2011 which was based on calcium isotopes and elemental sr ca ratios

diagenetic effects on the distribution of uranium in live and holocene corals from the gulf of aqaba abstract we investigated the effects of diagenetic alteration dissolution secondary aragonite precipitation and pore filling on the distribution of u in live and holocene coral skeletons for this we drilled into large porites lutea coral heads growing in the nature reserve reef nrr northern gulf of aqaba a site close to the marine biology laboratory elat israel and sampled the core material and porewater from the drill hole in addition we sampled holocene corals and beachrock aragonite cements from a pit opened in a reef buried under the laboratory grounds we measured the concentration and isotopic composition of u in the coral skeletal aragonite aragonite cements coral porewater and open nrr and gulf of aqaba waters uranium concentration in secondary aragonite filling the skeletal pores is significantly higher than in primary biogenic aragonite 17 3 0 6 compared to 11 9 0 3 nmol g 1 respectively this concentration difference reflects the closed system incorporation of uranyl tri carbonate into biogenic aragonite with a u ca bulk distribution coefficient kd of unity versus the open system incorporation into secondary aragonite with kd of 2 4 the implication of this result is that continuous precipitation of secondary aragonite over 1000 yr of reef submergence would reduce the coral porosity by 5 and can produce an apparent lowering of the calculated u ca sst by 1 c and apparent age rejuvenation effect of 7 with no measurable effect on the calculated initial u isotopic composition all modern and some holocene corals with and without aragonite cement from elat yielded uniform 234u 144 5 similar to the gulf of aqaba and modern ocean values elevated 234u values of 180 were measured only in mid holocene corals 5000 yr from the buried reef the values can reflect the interaction of the coral skeleton with 234u enriched ground seawater that washes the adjacent granitic basement rocks we conclude that pore filling by secondary aragonite during reef submergence can produce small but measurable effects on the u ca thermometry and the u th ages this emphasizes the critical importance of using pristine corals where the original mineralogy and porosity are preserved in paleooceanographic tracing and dating

constraining the marine strontium budget with natural strontium isotope fractionations 87sr 86sr δ88 86sr of carbonates hydrothermal solutions and river waters we present strontium sr isotope ratios that unlike traditional 87sr 86sr data are not normalized to a fixed 88sr 86sr ratio of 8 375209 defined as 88 86sr 0 relative to nist srm 987 instead we correct for isotope fractionation during mass spectrometry with a 87sr 84sr double spike this technique yields two independent ratios for 87sr 86sr and 88sr 86sr that are reported as 87sr 86sr and 88 86sr respectively the difference between the traditional radiogenic 87sr 86sr normalized to 88sr 86sr 8 375209 and the new 87sr 86sr values reflect natural mass dependent isotope fractionation in order to constrain glacial interglacial changes in the marine sr budget we compare the isotope composition of modern seawater 87sr 86sr 88 86sr seawater and modern marine biogenic carbonates 87sr 86sr 88 86sr carbonates with the corresponding values of river waters 87sr 86sr 88 86sr river and hydrothermal solutions 87sr 86sr 88 86sr hydend in a triple isotope plot the measured 87sr 86sr 88 86sr river values of selected rivers that together account for not vert similar18 of the global sr discharge yield a sr flux weighted mean of 0 7114 8 0 315 8 the average 87sr 86sr 88 86sr hydend values for hydrothermal solutions from the atlantic ocean are 0 7045 5 0 27 3 in contrast the 87sr 86sr 88 86sr carbonates values representing the marine sr output are 0 70926 2 0 21 2 we estimate the modern sr isotope composition of the sources at 0 7106 8 0 310 8 the difference between the estimated 87sr 86sr 88 86sr input and 87sr 86sr 88 86sr output values reflects isotope disequilibrium with respect to sr inputs and outputs in contrast to the modern ocean isotope equilibrium between inputs and outputs during the last glacial maximum 10 30 ka before present can be explained by invoking three times higher sr inputs from a uniquely glacial source weathering of shelf carbonates exposed at low sea levels our data are also consistent with the weathering peak hypothesis that invokes enhanced sr inputs resulting from weathering of post glacial exposure of abundant fine grained material

a compilation of western european terrestrial records 60 8 ka bp towards an understanding of latitudinal climatic gradients terrestrial records of past climatic conditions such as lake sediments and speleothems provide data of great importance for understanding environmental changes however unlike marine and ice core records terrestrial palaeodata are often not available in databases or in a format that is easily accessible to the non specialist as a consequence many excellent terrestrial records are unknown to the broader palaeoclimate community and are not included in compilations comparisons or modelling exercises here we present a compilation of western european terrestrial palaeo records covering entirely or partially the 60 8 ka intimate time period the compilation contains 56 natural archives including lake records speleothems ice cores and terrestrial proxies in marine records the compilation is limited to include records of high temporal resolution and or records that provide climate proxies or quantitative reconstructions of environmental parameters such as temperature or precipitation and that are of relevance and interest to a broader community we briefly review the different types of terrestrial archives their respective proxies their interpretation and their application for palaeoclimatic reconstructions we also discuss the importance of independent chronologies and the issue of record synchronization the aim of this exercise is to provide the wider palaeo community with a consistent compilation of high quality terrestrial records to facilitate model data comparisons and to identify key areas of interest for future investigations we use the compilation to investigate western european latitudinal climate gradients during the deglacial period and despite of poorly constrained chronologies for the older records we summarize the main results obtained from nw and sw european terrestrial records before the lgm

petrography strontium barium and uranium concentrations and strontium and uranium isotope ratios in speleothems as palaeoclimatic proxies soreq cave israel the reconstruction of the palaeoclimate of the eastern mediterranean region for the last 60 ka bp is based on the 18o and 13c variations of speleothems from soreq cave israel climatic conditions during most of the time interval between 60 and 17 ka bp the period equivalent to the last glacial were relatively cold and dry while they were warmer and wetter from 17 ka bp to the present at 17 ka bp there was a major climatic change with a sharp increase in annual rainfall and temperature and a very wet period occurring between 8 5 and 7 0 ka bp during the colder and drier period large detritus free preferentially oriented calcite crystals were deposited from slow moving water as a result of a sharp change in the hydrological regime at 17 ka bp fast moving water started entrainment of the soil and carrying detrital material into the cave and the calcite crystals deposited became small and anhedral coinciding with the petrographic and isotopic changes a sharp drop occurred in the concentration

mg isotopic composition of carbonate insight from speleothem formation simultaneous high precision measurement of 24 mg 25 mg and 26 mg isotopic compositions were made by multiple collector inductively coupled mass spectrometry mc icp ms relative to the international standard srm980 data are presented on low mg calcite speleothems and their associated host rocks and waters from four caves one in the french alps and three in israel covering various climate conditions in addition data are presented on three dolostones and three limestones from the himalaya the overall variation is 4 13x and 2 14x in n 26 mg and n 25 mg respectively this is 35 times the uncertainty of the measurements and clearly demonstrates that the terrestrial isotopic composition of mg is not unique each speleothem shows a characteristic range of n 26 mg values that are attributed to the isotopic composition of the local water differences between the isotopic composition of mg in the water dripping from stalactites and that of the modern speleothem are interpreted as being due to mg isotopic fractionation during carbonate precipitation in the temperature range of 4 18 c the low mg calcite is enriched in light isotopes by 1 35x amu and the dependence on temperature has been found to be less than 0 02x amu c despite various geological settings the n 26 mg of the studied dolostones is 2 0 1 2x higher than the n 26 mg of the limestones all together these results suggest a strong mineralogical control and a weak temperature effect on the mg isotopic composition of carbonate a 2002 elsevier science b v all rights reserved

uplift induced residual strain release and late thrusting extension in the anaran mountain front anticline zagros iran abstract in this work we present and discuss the pattern of extensional faults of the anaran anticline lurestan province of the zagros iran one of the most aesthetically appealing mountain front anticlines of the zaros this 100 km long structure is affected by extensional faults occurring in different along strike sectors of the anticline running parallel and oblique to the local trend of the fold hinge line and having displacements of hundreds of metres relationships between fold growth and extensional deformation are investigated by quantitatively analysing the attributes i e curvature elevation and throw across faults of a 3d surface representing the top of the ilam formation results indicate that the main stage of extensional deformation occurred during folding in particular we deduce that extensional faulting was associated with the erosional uplift of the crestal sector of the anticline where exhumation of previously shortened strata implied release of residual compressive strain with consequent annihilation of the horizontal stress component paralleling the tectonic transport direction this determined the onset of a large scale extensional regime at the shallower structural levels of the growing anticline

u th dating of lake lisan late pleistocene dead sea aragonite and implications for glacial east mediterranean climate change u series dating can be an effective means to obtain accurate and precise ages on quaternary carbonates however most samples require a correction for u and th in admixed detritus this complication is often addressed through generation of u th isochrons requiring analyses of several coeval samples in addition presence of water derived hydrogenous th in the carbonate can cause inaccuracies in isochron ages this study reports a high resolution u series chronology of sediments deposited by lake lisan the last glacial precursor of the dead sea the strategy employed combines multiple measurements from a few stratigraphic heights and fewer analyses from many heights in a single described and measured section the resulting chronology is based on ages at 22 heights in a 40 m thick section covering the interval of 70 14 calendar ka bp the effects of admixed detritus are evaluated using trace elements nearly pure aragonite samples indicated by very low abundances of insoluble elements such as nb and zr were found to contain hydrogenous th which causes the uncorrected u 230th age of a modern sample to be 2 5 ka nevertheless accurate ages have been obtained by correcting for the detrital and aqueous interferences the resulting ages are in stratigraphic order and their accuracy is evidenced by consistency of lisan formation u series and 14c ages with the coral based calendar radiocarbon age calibration the u th ages provide a context to unravel the limnological history of lake lisan boundaries between the lower middle and upper stratigraphic units correspond to the mis 4 3 and 3 2 transitions respectively during mis 2 and 4 the lake generally showed a stable two layer configuration and a positive fresh water balance reflected by deposition of laminated aragonite detritus dry intervals during mis 2 and 4 are indicated by thick gypsum layers and an inferred depositional hiatus which are temporally associated with heinrich events h1 at 17 ka and h6 at 65 ka respectively during mis 3 the lake level was unstable with intermittent dry periods indicated by abundant clastic layers and a significant hiatus between 43 49 ka clastic layers are associated with dansgaard oeschger events during mis 3 and indicate lake level declines during abrupt northern hemisphere warmings overall the climate of the eastern mediterranean region shows a strong linkage to the northern hemisphere climate with increasing lake size and stability during cold periods and fluctuations and dessication during warmings and heinrich events

unexpected calcium sources in deep soil layers in low fertility forest soils identified by strontium isotopes lorraine plateau eastern france forest ecosystems are often found on acid soils where calcium availability depends on two main inputs atmospheric deposition and the weathering of soil minerals and on the biological cycling of nutrients in the context of global change decreasing atmospheric inputs increasing biomass exportation climate change it is important to determine calcium sources to the ecosystem and tree nutrition to better understand how forest ecosystems will respond to these changes over time the aim of this study was to study and compare ca pools and cycling in two mature forest ecosystems clermont en argonne and azerailles developed on two contrasting polycyclic soils lorraine plateau eastern france and identify the ca sources contributing to ecosystem functioning at both sites soil ca pools were measured atmospheric deposition of ca was monitored from bulk precipitation and throughfall chemistry ca biological cycling was assessed by measuring litterfall and by a litter decomposition experiment strontium 87sr 86sr isotope data in the soil profile fine roots exchangeable pool bulk soil was used to estimate the distribution of sr and ca uptake in the soil profile and the relative contribution of mineral weathering in the soil layers to total ecosystems inputs despite important differences in ca availability in the topsoil between both sites tree growth and nutrition indicators showed no significant difference this discrepancy is not explained by the biological cycling of ca but may be partly explained by higher ca deposition at the ca poorer site strontium isotope data enabled to show important differences of ca sources for tree uptake at the ca poorer site deep soil layers 105 cm potentially represent from 32 to 100 of total sr uptake at the ca richer site results suggest that uptake is more evenly distributed in the soil profile sr isotope data coupled with a modeling approach suggest that two different mineral sources exist in the soil profile a radiogenic sr source in the topsoil 87sr 86sr 0 717 and a less radiogenic source in depth 87sr 86sr 0 717 the deep mineral source may represent from 40 to 86 of total sr inputs at the poorer site and from 25 to 86 at the richer site the origin of this deep strontium source is unclear but soil mineralogy suggests an allochthonous origin we hypothesize that this deep source originates from capillary rise of the groundwater aquifer this nutrient input to forest ecosystems is not commonly taken into account but may strongly participate in maintaining the chemical fertility of soils over time

millennial scale climate oscillations recorded in the lower danube loess over the last glacial period abstract in this study we provide a correlative age model for last glacial loess at the rasova valea cu pietre site in the lower danube region based on the correlation of palaeoenvironmental proxies to independently dated palaeoclimate archives luminescence dating and independent age control provided by the geochemically confirmed presence of the campanian ignimbrite ci tephra the ci tephra originating in the phlegrean fields of southern italy has been dated elsewhere by 40ar 39ar to 39 40 ka bp and is frequently found in the lower danube loess as such the ci tephra represents a valuable temporal and stratigraphic maker across loess deposits in the region our age model facilitates high resolution correlation of palaeoenvironmental features observed at rasova to palaeoclimate archives in greenland and the black sea mediterranean area we observe semi cyclic behaviour of the frequency dependent magnetic susceptibility throughout the profile which we ascribe to millennial scale climate variability also observed elsewhere in the black sea region this is the first study to clearly identify millennial scale climate variability over the holocene and last glacial in the lower danube loess proxy variability in the holocene indicates continuous aeolian sedimentation through this epoch

evidence for mass dependent isotopic fractionation of strontium in a glaciated granitic watershed abstract the stable isotope composition of strontium expressed as 88 86sr may provide important constraints on the global exogenic strontium cycle here we present 88 86sr values and 87sr 86sr ratios for granitoid rocks a 150 yr soil chronosequence formed from these rocks surface waters and plants in a small glaciated watershed in the central swiss alps incipient chemical weathering in this young system whether of inorganic or biological origin has no resolvable effect on the 87sr 86sr ratios and 88 86sr values of bulk soils which remain indistinguishable from bedrock in terms of sr isotopic composition although due in part to the chemical heterogeneity of the forefield the lack of a resolvable difference between soil and bedrock isotopic composition indicates that these soils have thus far witnessed minimal net loss of sr a low degree of chemical weathering is also implied by bulk soil chemistry the isotopic composition of sr in streamwater is more radiogenic than median soil reflecting the preferential weathering of biotite in the catchment streamwater 88 86sr values however are indistinguishable from bulk soil 88 86sr values implying that no resolvable fractionation of sr isotopes takes place during release to the weathering flux in the damma forefield analyses of plant tissue reveal that plants rhododendron and vaccinium preferentially assimilate the lighter isotopes of sr such that their 88 86sr values are significantly lower than those of the soils in which they grow additionally 88 86sr values of foliar and floral tissues are lower than those of roots contrary to observations for ca for which sr is often used as an analogue in weathering studies we suggest that processes that discriminate against sr in favour of ca due to the different nutritional requirement of plants for these two elements are responsible for the observed contrast

seasonal changes in the radiogenic and stable strontium isotopic composition of xijiang river water implications for chemical weathering seasonal changes in strontium sr isotopic systematics in large rivers can effectively track temporal variations in regional chemical weathering and help to better constrain the sr isotopic budget of global oceans however such records are scarce here we present a year long time series of both radiogenic and stable sr isotope measurements 87sr 86sr and 88sr from river water at guiping in the middle reaches of the xijiang river south china temporal changes in chemical weathering in the drainage basin were investigated by recording seasonal changes in the composition of both sr isotopes and major ions in the river water river water 87sr 86sr values range from 0 708487 to 0 710336 with most values being 0 7092 are generally accompanied by high rb sr ratios and low ph and 13c of dissolved inorganic carbo dic and occur during periods of large river flux this indicates that the contribution to the chemistry of river water from the weathering of silicate rocks is enhanced during rainy seasons seasonal variation in river water 88sr is large from 0 147 to 0 661 with higher 88sr values generally corresponding to higher 87sr 86sr values again low 88sr values 0 3 suggest a dominant contribution from the weathering of carbonate rocks whereas the high 88sr values may represent a contribution from intensive weathering of silicate rocks using the time series data we estimated the flux weighted averages of sr concentration 87sr 86sr and 88sr for the xijiang river to be 1 00 mol l 0 70960 and 0 38 respectively the sr concentration and 87sr 86sr results are close to previous estimates while the 88sr value is amongst the highest recorded for the large rivers of the world and is close to that of seawater our results indicate that large rivers draining through tropical sub tropical regions could play an important role in regulating the stable sr isotopic budget of global oceans

a thin elastic core can control large scale patterns of lithosphere shortening abstract peak lithospheric strength should reside in the rocks that under the applied stress cannot either creep due to low temperature or break due to high confining pressure the greatest resistance comes from dry olivine pyroxene rich upper mantle lowermost crust at moho conditions 400 600 c and 1 gpa we have conducted laboratory experiments to investigate the importance of the unbreakable core of the lithosphere in between its brittle and ductile parts and conclude that it can control the large scale lithospheric deformation pattern under shortening regardless of the thickness of the unbreakable core it acts as a restraining layer that is easily flexed but is unstretchable this eliminates large scale brittle faulting or homogeneous thickening as available shortening modes and results in irregular wrinkling of the unbreakable layer we discuss geodynamic implications of our laboratory experiments and advocate studies of large scale buckling of the lithosphere as a relevant shortening mode

biological control of calcium isotopic abundances in the global calcium cycle measurements of 44ca 40ca expressed as 44ca were made on igneous rocks and on shell and bone material from modern organisms to investigate the magnitude and origins of calcium isotopic fractionation in nature the results document a span of 4 in 44ca measured with the double spike technique to a precision of 0 15 volcanic rocks including basalt and rhyolite show little variability and cluster near 44ca 0 0 2 systematic analysis of biological samples indicates that biological processing of calcium discriminates against heavy isotopes and that biological fractionation is the primary generator of calcium isotopic fractionation in nature preliminary data suggest that calcium becomes isotopically lighter as it moves through food chains calcium carbonate shells of marine microorganisms and deep sea carbonate ooze have 44ca about 1 0 lower than seawater this fractionation causes seawater to be enriched in heavy calcium 44ca 0 9 relative to igneous rocks marine organisms consequently are isotopically heavier than their terrestrial counterparts at similar trophic level the calcium isotopic composition of living and fossil organisms may record information on diet and environment

the middle devonian basins of western norway sedimentary response to large scale transtensional tectonics abstract the devonian basins of western norway were formed during late to post orogenic extension of overthickened caledonian crust the basins are situated in the hanging wall of the extensional nordfjord sogn detachment zone nsdz and display extensional half graben geometries in sections parallel to the local direction of principal extension based on overall facies configurations paleocurrent patterns and intrabasinal structures we infer an anticlockwise rotation of the syndepositional extension direction from nw se in the south solund basin to wsw ene in the north hornelen basin the axes of folds that are roughly parallel to the local extension direction are rotated correspondingly the kvamshesten basin is located between the solund and hornelen basins sedimentological and structural data show evidence of an early southeastwards tilt direction followed by a more eastwards tilt and associated e w flowing paleodrainage correspondingly nw se trending folds and reverse faults are superposed by e w trending ones at low to intermediate stratigraphic levels the variations in apparent tilt direction for the basins together with variations in intrabasinal structure is interpreted to reflect an anticlockwise rotation of the regional syndepositional strain field the above observations and inferences indicate that the devonian basins in western norway formed in a strain field dominated by regional transtension accommodated by extension along the nsdz and sinistral strike slip along orogen parallel shear zones and faults to the north of the basins alternatively nw directed extension preceded the introduction of a sinistral strike slip component the models are in accordance with recent work carried out in the footwall of the nsdz and illustrates the tectono sedimentary response to a complex interplay between extension and strike slip that appears to have been fundamental in the late stage disintegration of the caledonian orogen

rheology of plasticine used as rock analogue the impact of temperature composition and strain abstract uniaxial compression tests have been carried out to determine the temperature dependent rheology of plasticine commonly used for tectonic modelling the original plasticine types kolb brown beck s orange beck s green weible special soft are characterized by strain rate softening with power law exponents n and apparent viscosities ranging from 5 8 to 7 3 and 3 4 10 5 to 2 2 10 7 pa s respectively if e 10 4 10 3 s 1 and t 25 c beck s orange shows steady state creep whereas the other types show strain hardening the activation energy determined for 20 c t 35 c is ranging from 323 34 to 488 22 kj mol 1 a rise in temperature results in linear decreases of n and and a reduction in the degree of strain hardening steady state creep and major changes in n and have further been observed at decreasing filler matrix ratios the latter being obtained by adding oil to the original plasticine the new results suggest that plasticine can be used to model the deformation of natural rocks undergoing dislocation creep various rock analogues with strain hardening or steady state creep and prescribed stress exponents ranging from 3 4 to 12 3 can be easily produced by changing the temperature and or the filler matrix ratio of commercial plasticine types