planktonic foraminiferal mg ca as a proxy for past oceanic temperatures a methodological overview and data compilation for the last glacial maximum as part of the multi proxy approach for the reconstruction of the glacial ocean margo incentive published and unpublished temperature reconstructions for the last glacial maximum lgm based on planktonic foraminiferal mg ca ratios have been synthesised and made available in an online database development and applications of mg ca thermometry are described in order to illustrate the current state of the method various attempts to calibrate foraminiferal mg ca ratios with temperature including culture trap and core top approaches have given very consistent results although differences in methodological techniques can produce offsets between laboratories which need to be assessed and accounted for where possible dissolution of foraminiferal calcite at the sea floor generally causes a lowering of mg ca ratios this effect requires further study in order to account and potentially correct for it if dissolution has occurred mg ca thermometry has advantages over other paleotemperature proxies including its use to investigate changes in the oxygen isotopic composition of seawater and the ability to reconstruct changes in the thermal structure of the water column by use of multiple species from different depth and or seasonal habitats presently available data are somewhat limited to low latitudes where they give fairly consistent values for the temperature difference between late holocene and the lgm 2 3 5 c data from higher latitudes are more sparse and suggest there may be complicating factors when comparing between multi proxy reconstructions

climate instability during the last interglacial period recorded in the grip ice core isotope and chemical analyses of the grip ice core from summit central greenland reveal that climate in greenland during the last interglacial period was characterized by a series of severe cold periods which began extremely rapidly and lasted from decades to centuries as the last interglacial seems to have been slightly warmer than the present one its unstable climate raises questions about the effects of future global warming

accelerator mass spectrometer ages for the younger dryas event in atlantic canada abstract in atlantic canada bulk sediment dates for the onset of a late glacial cooling widely regarded as the younger dryas event are highly variable ranging from 14 300 270 to 10 800 100 yr b p we present the first accelerator mass spectrometer ams 14c dates from atlantic canada at or close to the boundaries of this event from six sites in new brunswick and nova scotia the mean of five dates places the onset of this cooling at ca 10 770 yr b p the inclusion of a sixth perhaps anomalously old date changes the mean to 10 880 yr b p the termination averages three dates ca 10 000 yr b p these dates place the timing of the younger dryas event in atlantic canada closer in line with the traditional chronozone boundaries of 11 000 and 10 000 yr b p in northwest europe

an approach to improve rayleigh wave ellipticity estimates from seismic noise application to the los angeles basin s u m m a r y we present an approach for seismic noise which improves rayleigh wave ellipticity estimates by reducing the influences from body waves and love waves the method requires three component seismographs and uses the phase shift information between the vertical and horizontal components we select data that show the phase shift of about 90 in order to separate rayleigh waves from body waves and love waves in comparison to the usual h v approach the estimates for rayleigh wave ellipticity are systematically different by about 20 per cent because the existence of s waves and love waves systematically increases horizontal amplitudes the differences in the inverted s wave velocity structure reach up to about 20 per cent in the upper 20 km the method is limited to a relatively low frequency range below 0 3 hz as the 90 phase shift peaks become difficult to identify above 0 3 hz despite this limitation in the frequency range this approach can improve the s wave velocity structure in the upper 5 10 km which should lead to a better prediction of long period ground motions for periods of about 5 10 s an improved prediction of such long period ground motion is important for hazard mitigation in the world s metropolitan areas with high rise buildings this approach is applied to the structure in the broader los angeles basin in southern california and improvement of the reference velocity structure in the upper 5 10 km is demonstrated

methodology of the last climatic cycle reconstruction in france from pollen data abstract a numerical method has been devised to reconstruct the climate of the last climatic cycle from pollen data reliable annual reconstructions have been published recently for the two french long sequences of la grande pile and les echets covering the last 140 millennia this paper gives more details on the method used it proposes new reconstructions based on an extended modern pollen data base these reconstructions are consistent with the previous ones especially detailed information is obtained on the seasonal characteristics of climate computations of gcm on the climate variations from 125 kyr to 115 kyr b p are confirmed for western europe the insolation variations have induced at that time a decrease of seasonality accompanied by an increased cyclonic activity in winter this has been the beginning of the first ice growth after the last interglacial other glacier growth phases are detected at the end of substage 5c and particularly at the end of substage 5a

inversion of complex body waves we have developed a method that inverts seismic body waves to determine the mechanism and rupture pattern of earthquakes the rupture pattern is represented as a sequence of subevents distributed on the fault plane this method is an extension of our earlier method in which the subevent mechanisms were fixed in the new method the subevent mechanisms are determined from the data and are allowed to vary during the sequence when subevent mechanisms are allowed to vary however the inversion often becomes unstable because of the complex trade offs between the mechanism the timing and the location of the subevents many different subevent sequences can explain the same data equally well and it is important to determine the range of allowable solutions some constraints must be imposed on the solution to stabilize the inversion we have developed a procedure to explore the range of allowable solutions and appropriate constraints in this procedure a network of grid points is constructed on the i plane where and i are respectively the onset time and the distance from the epicenter of a subevent the best fit subevent is determined at all grid points then the correlation is computed between the synthetic waveform for each subevent and the observed waveform the correlation as a function of and i and the best fit mechanisms computed at each i grid point depict the character of allowable solutions and facilitate a decision on the appropriate constraints to be imposed on the solution the method is illustrated using the data for the 1976 guatemala earthquake

transdimensional inversion of scattered body waves for 1d s wave velocity structure application to the tengchong volcanic area southwestern china abstract inversion of receiver functions is commonly used to recover the s wave velocity structure beneath seismic stations traditional approaches are based on deconvolved waveforms where the horizontal component of p wave seismograms is deconvolved by the vertical component deconvolution of noisy seismograms is a numerically unstable process that needs to be stabilized by regularization parameters this biases noise statistics making it difficult to estimate uncertainties in observed receiver functions for bayesian inference this study proposes a method to directly invert observed radial waveforms and to better account for data noise in a bayesian formulation we illustrate its feasibility with two synthetic tests having different types of noises added to seismograms then a real site application is performed to obtain the 1 d s wave velocity structure beneath a seismic station located in the tengchong volcanic area southwestern china surface wave dispersion measurements spanning periods from 8 to 65 s are jointly inverted with p waveforms the results show a complex s wave velocity structure as two low velocity zones are observed in the crust and uppermost mantle suggesting the existence of magma chambers or zones of partial melt the upper magma chambers may be the heart source that cause the thermal activity on the surface

2000 year environmental history of a karstic lake in the mediterranean pre pyrenees the estanya lakes spain abstract the sediment record of the estanya lakes pre pyrenees spain indicates that this region was intensely affected by land use during the middle and modern ages which contrasts with the present day poor socioeconomic development of the region the correlation between sediment and biotic data and well known historical events suggests a reliable history of environmental changes in this area during the last 2000 years changes in lake level were mainly controlled by climatic factors whereas properties such as lithology organic carbon ostracods and pollen content are mainly associated with lake management and land use major sedimentological changes resulted from the use of the lake for hemp retting at the start of the xivth century subsequent depopulation of the area in the xxth century led to the progressive recovery of the lacustrine ecosystem

climatic change on the iberian peninsula recorded in a 30 000 yr pollen record from lake banyoles the banyoles lacustrine sequence shows that the vegetational history of the northeastern iberian peninsula during the last 30 000 yr follows the north atlantic pattern of climatic oscillations the banyoles pollen diagram supported by two calibrated 14c dates and nine u th dates shows a clear interstadial event between 30 000 and 27 000 yr b p a pleniglacial period with minor oscillations that ended abruptly ca 14 420 410 yr b p and a late glacial sequence that records the classical stages described in northern europe the bolling allerod interstade the younger dryas event at 12 000 yr b p u series age and a short warming phase between the younger dryas and the last cold event dated at 11 000 yr b p u series age

abrupt changes of temperature and water chemistry in the late pleistocene and early holocene black sea new mg ca sr ca and published stable oxygen isotope and 87sr 86sr data obtained on ostracods from gravity cores located on the northwestern black sea slope were used to infer changes in the black sea hydrology and water chemistry for the period between 30 to 8 ka b p calibrated radiocarbon years the period prior to 16 5 ka b p was characterized by stable conditions in all records until a distinct drop in 18o values combined with a sharp increase in 87sr 86sr occurred between 16 5 and 14 8 ka b p this event is attributed to an increased runoff from the northern drainage area of the black sea between heinrich event 1 and the onset of the bolling warm period while the mg ca and sr ca records remained rather unaffected by this inflow they show an abrupt rise with the onset of the bolling allerod warm period this rise was caused by calcite precipitation in the surface water which led to a sudden increase of the sr ca and mg ca ratios of the black sea water the stable oxygen isotopes also start to increase around 15 ka b p although in a more gradual manner due to isotopically enriched meteoric precipitation while sr ca remains constant during the following interval of the younger dryas cold period a decrease in the mg ca ratio implies that the intermediate water masses of the black sea temporarily cooled by 1 2 c during the younger dryas the 87sr 86sr values drop after the cessation of the water inflow at 15 ka b p to a lower level until the younger dryas where they reach values similar to those observed during the last glacial maximum this might point to a potential outflow to the mediterranean sea via the sea of marmara during this period the inflow of mediterranean water started around 9 3 ka b p which is clearly detectable in the abruptly increasing mg ca sr ca and 87sr 86sr values the accompanying increase in the 18o record is less pronounced and would fit to an inflow lasting 100 a

a 13 000 year climate record from western tibet although the tibetan plateau is important in influencing the atmospheric circulation of the northern hemisphere1 3 there are only a few continuous palaeoclimate records available and these are limited to the plateau s northeastern margin4 6 here we present a 13 000 yr record from sumxi co western tibet constructed from both lake core and shoreline studies which shows that conditions in the early middle holocene were warmer and wetter than at present these results confirm model predictions of an intensified monsoon over the region at 9 000 yr bp owing to an orbitally induced increase in summer insolation7 8 we also find evidence for warm humid pulses at 12 500 and 10 000 yr bp in phase with the steps of the last deglaciation and for a return to cold dry conditions at 11 10 000 yr bp none of which can be explained by orbital variations the existence of the cold episode confirms that the cooling associated with the younger dry as event occurred in continental china6 9 and provides further evidence of the global nature of this event10

climatic transfer function from quaternary molluscs in european loess deposits abstract correspondence and multiple regression analysis of terrestrial molluscs in the loess sections of achenheim alsace france has permitted the reconstruction of climatic variations during the last three glacial interglacial cycles back to 339 000 yr b p the sequence has been dated according to the specmap chronology of imbrie et al 1984 and the fossil faunas have been calibrated in relation to recent assemblages sampled in defined ecological conditions in sweden and france transfer functions that relate the abundances of different species to climate allow the reconstruction of temperature and precipitation estimates for the coldest february and warmest august months in present day alsace were obtained and variations in temperature between 13 and 2 c in winter and 10 and 17 c in summer were determined these results are consistent with those yielded by transfer functions using other continental fossils estimates differ for past precipitation summer precipitation is always less than present with values between 50 and 78 mm while modern august values are 76 mm higher winter estimates are always higher than the present mean between 76 and 33 mm while the recent february value is 34 mm comparisons between cycles show that the climatic patterns described for one cycle cannot be strictly applied to the others comparisons have been made with the pollen stratigraphy of la grande pile the nearest quantified sequence to achenheim and with some atlantic cores in order to study the magnitude of deviations from modern mean values of the climatic parameters

crustal structure beneath portugal from teleseismic rayleigh wave ellipticity up until now portugal lacked a countrywide shear velocity model sampling short length scale crustal structure which limits interpretations of seismicity and tectonics and predictions of strong ground motion in turn such interpretations and predictions are important to help mitigate risk of destruction from future large on and offshore earthquakes similar to those that portugal has experienced in the past e g the mw 8 5 8 7 tsunamigenic event in 1755 in this study we measured teleseismic rayleigh wave ellipticity rwe from 33 permanent and temporary seismic stations in portugal with wave periods between 15 s and 60 s and inverted it for 1 d models of shear wave velocity vs structure beneath each station using a fully non linear monte carlo method because rwe is strongly sensitive to the uppermost few kilometres of the crust both rwe measurements and vs models are spatially correlated with surface geology in portugal for instance we find that sedimentary basins produced by rifting that had begun in the mesozoic such as the lusitanian basin lb and the lower tagus sado basin ltsb are characterised by higher rwe lower vs interestingly we observe similar rwe and vs values in the interior of the central iberian zone ciz which is a metamorphic belt of paleozoic age together with reduced crustal thickness previously estimated for the same parts of the ciz this suggests that the ciz might have experienced an episode of extension possibly simultaneous to mesozoic rifting the galicia tras os montes zone gtmz that has undergone polyphased deformation since the paleozoic is characterised by the lowest rwe highest vs in portugal ossa morena zone and the south portuguese zone exhibit intermediate vs values when compared to that of basins and the gtmz our crustal vs model can be used to provide new insights into the tectonics seismicity and strong ground motion in portugal

the arid humid transition in the sahara and the sahel during the last deglaciation at the time of the last glacial maximum the sahara and sahel regions of north africa were extremely dry new records of rainfall show that during the subsequent deglaciation the transition from arid to humid conditions in these regions occurred synchronously in two main steps comparison with other records of palaeoclimate in europe and the north atlantic ocean shows that certain common factors controlled changes in ocean and atmosphere dynamics during the deglaciation

the holocene and upper pleistocene pollen record from padul granada spain a new study two borings were made at the site of padul granada pollen analysis of 200 spectra from two successive sequences 14 8 and 8 m deep enables a description of the vegetational and climatic history of this region the most southern one in europe from early wurmian times the chronology is supported by twenty one 14c dates original equivalents are found for the great european prewurm interstadials a markedly arid though thermically not extreme episode exactly equivalent to stage 4 of the marine isotopic stratigraphy closes this relatively temperate period the middle part of the last glacial shows climatic fluctuations that are poorly characterized as is often the case in europe for this period a long section very probably corresponding to the complete last pleniglacial does not show any climatic amelioration towards 15 000 yr b p a change in the diagram is noted that can only be interpreted as reflecting a larger expansion of a regional steppe cover this event also reported on three occasions in southeast france marks the beginning of the oldest dryas the climatic amelioration of ca 13 000 yr b p is far more pronounced here than anywhere else in europe whereas that at 10 000 yr b p is not so clearly marked this unexpected result may be accounted for by the fact that padul is the first continental site so far south and so near pleniglacial refuges to be known on the other hand this result is consistent with what is known from oceanic isotopic stratigraphy a quite new late glacial and holocene vegetational history is revealed characterized by the early appearance and dominance of quercus ilex oak forests of a southern type and the early occurrence of quercus suber and olea it is the first account of a complete history of the postglacial reafforestation in a region with a modern semi arid mediterranean climate from the palaeoclimatic point of view it shows that the hot and humid holocene optimum was attained slightly before 8000 yr b p and that the holocene climatic fluctuations were of but small amplitude

deep crustal structure of the indian shield from joint inversion of p wave receiver functions and rayleigh wave group velocities implications for precambrian crustal evolution 1 the s wave velocity structure of the crust and uppermost mantle of the indian shield has been investigated by jointly inverting p wave receiver functions and rayleigh wave group velocities at 38 broadband stations in the subcontinent the indian shield is an amalgamation of several terranes of archean and proterozoic age that were partly flooded by deccan trap volcanism during cenozoic times and that make up a natural laboratory for assessing models of precambrian crustal evolution our results reveal significant variations in crustal thickness and deep crustal velocities 45 50 km thick under the archean west dharwar craton and southern granulite terrane with lower crustal velocities around 4 1 km s 32 35 km thick beneath the archean east dharwar and bundelkhand cratons with lower crustal velocities around 3 8 3 9 km s 50 65 km thick under the proterozoic bhandara craton with lower crustal velocities around 4 2 4 3 km s and 55 km thick under the proterozoic aravalli delhi belt with lower crustal velocities around 4 2 km s s velocities in the 4 1 4 3 km s range in the deep crust can be attributed to mafic lithologies suggesting there has been no secular change in the precambrian evolution of the south indian shield moreover pervasive mafic dike swarming throughout the indian shield suggests that the layer of mafic cumulates is 2 5 1 6 ga old and that it delaminated from some archean terranes our interpretation is that mafic underplating of the terranes making up the indian shield occurred in proterozoic times and that a refractory root developed under the archean terranes after the proterozoic event

climatic and limnological changes associated with the younger dryas in atlantic canada pollen diatom and chironomid fossils from the sediments of a core from brier island bog lake nova scotia were studied in an attempt to relate changes in microfossil composition to a climatic cooling in atlantic canada correlative with the european younger dryas ca 10 to 11 ka our paleolimnological data were then compared to similar types of data from splan pond new brunswick to determine if there were any significant differences between a coastal and a more inland site nonarboreal pollen was dominant throughout the brier island core and the interval 10 0 11 0 ka did not show the typical decline in picea and increases in tundra like vegetation characteristic of many sites in atlantic canada however the limnological indicators did undergo marked changes in taxon composition the chironomid assemblage was initially dominated by shallow water warm adapted chironomid taxa followed by abundant sergentia a cold stenotherm during 10 11 ka sergentia disappeared in the post younger dryas interval and the warm adapted genera resumed dominance chironomid inferred paleotemperature reconstructions revealed that at both brier island bog lake and splan pond summer surface water temperatures dropped abruptly to between 13 and 17 c during the 10 11 ka interval suggesting that a cooler climate was present in atlantic canada correlative with the european younger dryas diatom assemblage changes during the same period corroborate the occurrence of limnological fluctuations

ams radiocarbon dating and varve chronology of lake soppensee 6000 to 12000 14c years bp for the extension of the radiocarbon calibration curve beyond 10000 14c y bp laminated sediment from lake soppensee central switzerland was dated the radiocarbon time scale was obtained using accelerator mass spectrometry ams dating of terrestrial macrofossils selected from the soppensee sediment because of an unlaminated sediment section during the younger dryas 10000 11000 14c y bp the absolute time scale based on counting annual layers varves had to be corrected for missing varves the soppensee radiocarbon verve chronology covers the time period from 6000 to 12000 14c y bp on the radiocarbon time scale and 7000 to 13000 calendar y bp on the absolute time scale the good agreement with the tree ring curve in the interval from 7000 to 11450 cal y bp cal y indicates calendar year proves the annual character of the laminations the ash layer of the vasset killian tephra massif central france is dated at 8230 140 14c y bp and 9407 44 cal y bp the boundaries of the younger dryas biozone are placed at 10986 69 cal y bp younger dryas preboreal and 1212 86 cal y bp allerod younger dryas on the absolute time scale the absolute age of the laacher see tephra layer dated with the radiocarbon method at 10 800 to 11200 14c y bp is estimated at 12350 135 cal y bp the oldest radiocarbon age of 14190 120 14c y bp was obtained on macrofossils of pioneer vegetation which were found in the lowermost part of the sediment profile for the late glacial the offset between the radiocarbon 10000 12000 14c y bp and the absolute time scale 11400 13000 cal y bp in the soppensee chronology is not greater than 1000 years which differs from the trend of the u th radiocarbon curve derived from corals

quantifying species environment relationships in non marine ostracoda for ecological and palaeoecological studies examples using iberian data abstract with current concerns over issues such as global warming the use of palaeoecological data to reconstruct past environments has gained a special significance but much of the work on ostracod ecology and paleoecology has been qualitative in nature or on a site specific rather than integrated regional basis furthermore ostracod ecological relationships are complex with each species occupying a multidimensional niche and a range of statistical techniques can be employed to establish the significance of different environmental variables on species distribution we employ logistic regression lr and canonical correspondence analysis cca to define ostracod species niches and assemblage response to environmental gradients using a modern dataset of 465 ostracod samples from the eastern iberian peninsula in addition to these ecological analyses we develop ostracod based transfer functions for the quantitative reconstruction of past environmental change from a modern regional data set of non marine ostracod and limnological data by means of weighted averaging wa regression and calibration examples cited are primarily from modern and fossil ostracod samples from iberian water bodies our results suggest that water chemistry solute composition and concentration and temperature are the factors to which non marine ostracod species respond in a more clear and consistent way species environment relationships modelled using the transfer function approach of wa are strong for the above mentioned variables and therefore these models may be of great help in palaeoenvironmental reconstructions

a 220 ka palaeoenvironmental reconstruction of the fuentillejo maar lake record central spain using biomarker analysis abstract the sedimentary record of the volcanic lake known as the fuentillejo maar central spain offers the opportunity to determine the palaeoenvironmental evolution of the central southern part of the iberian peninsula during the middle and upper pleistocene a total of 439 samples from the upper 88 m of a ca 142 m long core spanning the last ca 355 ka were examined the interval corresponds to the last 220 ka of the record high n alkane cpi values and the presence of sulfur revealed that little diagenetic signal attenuation or modification had occurred a number of n alkane based indices e g predominant n alkane acl paq and tar hc ratios and the proportion of c 27 c 29 and c 31 n alkanes with respect to the summed c 27 c 29 c 31 alkanes showed changing conditions in the organic matter input to the maar lake over time with episodes involving a major input of terrestrial vegetation alternating with others in which algae or a mixed input of terrestrial plants aquatic macrophytes and algae occurred the proportions of c 27 c 29 and c 31 were useful for reconstructing the palaeoenvironmental evolution of the basin as they allowed assignment of several dry intervals during which grasses developed while during humid phases trees expanded at the expense of grasses in general we found good correspondence between these episodes and the climatic cycles observed in 18 o records from ices cores in greenland and antarctica as well as from marine cores thus we conclude that global palaeoclimatological changes were recorded in the maar record likewise heinrich events appeared to be reflected in the n alkane indices this was confirmed by single spectral analysis and cross spectral analysis with the insolation curve on 21 july at a latitude of 65 n the approach revealed that the cycles interpreted in the fuentillejo record 103 41 23 and 19 ka showed evidence of orbital influence related to the astronomical cycles of the eccentricity variation in the earth s orbit the earth s obliquity oscillation and the precession variation milankovitch theory

inversion of the hz ratio of microseisms for s wave velocity in the crust summary s wave velocity in the shallow crust is an important controlling parameter for ground motion amplification it is a key parameter for prediction of ground motion and thus for earthquake hazard mitigation in general shallow s wave velocity structure has often been obtained from phase velocity of microtremors and microseisms we present a new approach which directly inverts the ratio of horizontal to vertical amplitudes of microseisms which is referred to as the hz ratio in this paper our approach consists of i isolation of rayleigh wave dominant portions in seismograms by using the 90 degree phase shift between horizontal and vertical component ii measurement of the hz ratios as a function of frequency and iii iterative inversion for s wave velocity structure in the crust depth sensitivity kernels of the hz ratios for density p wave velocity and s wave velocity are derived by a numerical method examples of the application of this method to data in southern california show that the hz ratio data require modification of the standard seismic velocity model in this region southern california earthquake center community velocity model 3 0 or scec cvm in the upper 10 15 km the derived models show amplification of incident sh waves by factors of 2 8 relative to the prediction by the scec cvm the proposed approach has promise for applications to other regions in the world because microseisms are observed everywhere in the world the method may become even more powerful if it is combined with phase velocity data

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

karstification without carbonic acid bedrock dissolution by gypsum driven dedolomitization aggressive karstification can take place where dolomite and gypsum are in contact with the same aquifer gypsum dissolution drives the precipitation of calcite thus consuming carbonate ions released by dolomite lake banyoles in northeastern spain is a karst lake supplied by sublacustrine springs and karstic collapse is occurring in the immediate vicinity of the lake lake water is dominated by mg ca and so 4 hco 3 and is supersaturated with calcite that is actively accumulating in lake sediments water chemistry sulfur isotope composition local stratigraphy and mass balance modelling suggest that the primary karst forming process at at lake banyoles is dedolomitization of basement rocks driven by gypsum dissolution karstification takes place along the subsurface contact between the gypsiferous beuda formation and the dolomitic perafita formation this process is here recognized for the first time to cause karstification on a large scale this is significant because it proceeds without the addition of soil generated carbonic acid gypsum driven dedolomitization may be responsible for other karstic systems heretofore attributed to soil generated carbonic acid

mg ca and sr ca of ostracod valves from living species of lake geneva abstract the mg ca and sr ca ratios of living ostracods belonging to 15 different species and sampled monthly over a one year cycle at five sites 2 5 13 33 and 70 m water depths in western lake geneva switzerland are compared to the oxygen and carbon isotope compositions measured on the same samples as well as to the temperature and chemical composition of the water 18 o h2o 13 c dic mg ca h2o and sr ca h2o at the time of ostracod calcification the results indicate that trace element incorporation varied at the species level mainly because of the ecological and biological differences between the different species life cycle micro habitat preference biomineralisation processes and the control thereof on trace element incorporation of the ostracods in littoral zones the mg ca and sr ca of ostracod valves increase as temperature and mg ca and sr ca of water increase during spring and summer hence reflecting mainly seasonal variations however given that for lake geneva the mg ca and sr ca of water also vary with temperature it is not possible to distinguish the effects of temperature from those of changes in chemical composition of water on the trace element content in ostracod valves results support that both water temperature and water mg ca and sr ca ratios control the final trace element content of cyprididae valves in contrast the trace element content of species living in deeper zones of the basin is influenced by variations in the chemical composition of the pore water for the infaunal species trace element content measured for these specimens cannot therefore be used to reconstruct the compositions of the water lake bottom in addition incorporation of mg and sr into the shell differs from one family sub family or even species to the other this suggests that the distinctive mg and sr partition coefficients for the analysed taxa result from different valve calcification strategies that may be phylogenetic

shear wave velocity structure in the northern basin and range province from the combined analysis of receiver functions and surface waves a new method based on the joint inversion of receiver functions and surface wave phase velocities results in well determined shear velocity structures that are consistent with the compressional wave structure gravity heat flow and elevation data in the northern basin and range this new inversion method takes advantage of average velocity information present in the surface wave method and differential velocity information contained in the receiver function method thus min imizing the nonuniqueness problem that results from the velocity depth trade off an unusually thick 38 kin and relatively faster crust and upper mantle are found in central and eastern nevada compared to the thin 28 to 34 km and slower crust and upper mantle of the western basin and range we interpret the regions of thicker and faster crust and upper mantle as zones that have undergone less cenozoic ex tension relative to the surrounding regions to the west and north the thick crust and consequently greater depth to the dense mantle material is consistent with the gravity low pattern in central and eastern nevada simple gravity modeling shows both local and regional isostatic compensation occur within 40 km of the surface indicating a near classical airy type of compensation in the province we analyze in detail the shear wave s wave velocity model derived from the receiver functions at station bmn and compressional wave p wave velocity models derived from the 1986 passcal experiment in northwestern nevada the most interesting feature of these models is the presence of negative velocity gradients in the s wave model with no corresponding velocity decrease in the p wave models between depths of 10 and 24 km this combined velocity model may be explained by high pore fluid pressures at these depths this model favors a layered fluid porosity model proposed in the literature to explain extensive middle to lower crust conti nental seismic reflections and high electrical conductivity an upper mantle grada tional low velocity zone is present between 32 and 38 km in the s wave model this upper mantle shear wave low velocity zone is consistent with partial melt which may be the source material for magmatic underplating in this region

evidence from western north america for rapid shifts in climate during the last glacial maximum the estancia basin in southwestern united states contains evidence for strong and rapid pulsations in the supply of moisture brought into the region during the last ice age the pulses were recorded during episodes of stream discharge that spread plumes of fresh water laden with quartz sand over the saline lake the largest pulses in stream discharge lasted only a few decades were organized into cycles that were spaced approximately 200 to 250 and 2000 years apart and were of sufficient magnitude to freshen and maintain the lake at its maximum recorded elevation

receiver functions for the tien shan analog broadband network contrasts in the evolution of structures across the talasso fergana fault we determined the structure of the crust beneath the central and western tien shan by analyzing broadband 1 20 s analog seismograms of converted p sv phases generated by earthquakes at teleseismic distances and recorded by 14 seismograph stations the one dimensional structures that best explain the waveforms reveal pronounced differences in crustal velocities east and west of the talasso fergana fault specifically the transition zone between the crust and the mantle east of the fault is about 2 times broader than that west of the fault also velocities at depths between 10 and 35 km are about 10 lower in the east although the depth range of these lower velocities is not well resolved the talasso fergana fault is an important boundary for other observables in addition to the structural discontinuities observed at the surface the areas east of the talasso fergana fault are associated with abnormally low mantle velocities outcrops of basalt low q and short wavelength variations in anisotropy integrating these observations we interpret the broad mantle gradient as being due to vertical intrusions of mantle material into the lower crust likewise the low velocities in the midcrust could be thermally induced or due to the introduction of magmatically derived fluids the gross contrast in structure east and west of the talasso fergana fault could reflect a contrast in the dynamics of mountain building in these two regions we postulate that while crustal shortening is the dominant mechanism controlling topography west of the talasso fergana fault vertical uplift caused by a mass deficiency in the upper mantle may contribute significantly to the generation and maintenance of the high elevations east of the fault

strontium content of ostracods indicates lacustrine palaeosalinity individual non marine ostracod valves contain sr in proportion to the sr content of their host lake water two commonly coexisting large planktonic species mytilocypris praenuncia and australocypris robusta have a sr distribution coefficient kd sr ca of 0 082 which is independent of temperature in the range 10 18 c if the relationship between salinity and the sr content of a hydrologically simple lake is known palaeosalinities can be calculated from fossil ostracods we present here palaeosalinities for the past 10 000 yr for lake keilambete victoria calculated from ostracod sr ca of fossil material which are in striking agreement with independent interpretations of palaeosalinity the range of salinity spans 14 95 we also show that a reliable quantitative continuous indicator of lacustrine palaeosalinity is important for the elucidation of continental palaeoenvironments for palaeoclimatology and archaeology and ocean continent climatic correlations and interactions

magnesium content of non marine ostracod shells a new palaeosalinometer and palaeothermometer abstract ostracods are microcrustaceans with calcitic carapaces each consisting of two valves or shells that grow by moulting and regeneration of sequentially larger valves up to nine times before reaching maturity the mg content of these valves is species dependent and is a function of their growth stage and the temperature salinity mg content and mg ca ratio of their host water newly formed partly calcified valves of the non marine nektic ostracod mytilocypris henricae have high mg contents 100 000 ppm mg in caco3 at individual shell weights of 2 g this relative mg content decreases as calcification proceeds until shell weights exceed 120 g whereupon the mg content is constant and useful as an indicator of the ostracod s environment mg ca ratios in individual ostracod valves from several species of the genera mytilocypris and australocypris from culture experiments and a series of australian lakes indicate that the valve s mg content increases as a function of increasing temperature and salinity within the range 11 25 c and for waters containing 24 2325 ppm mg the molar mg ca ratio in these ostracods fully calcified valves increases by 0 0015 or 370 ppm mg in caco3 per 1 c and per change of 125 ppm mg in solution for most mainland australian lakes a change in water composition of 125 ppm mg corresponds to a change of 3 5 in salinity for a given mg content of a lake the mg ca ratio of the water may vary within the range of common lacustrine values without significantly affecting mg uptake in the ostracod valves these relationships can provide palaeosalinities and or palaeotemperatures for ostracods recovered from continental sediments for mg partitioning an increase in temperature and salinity produce increased mg content in ostracods whereas for 18o fractionation in biogenic calcite an increase in temperature produces a decrease in 18o of the ostracod and an increase in salinity leads to an increase in 18o of the ostracod thus a combination of 18o and mg measurements on non marine ostracods should enable unique resolution of palaeotemperature and palaeosalinity variations

solution collapse depressions and suspensates in the limnocrenic lake of banyoles ne spain a high resolution seismic reflection survey in the banyoles limnocrenic solution lake allowed penetration of dense suspensates occupying cone like bottom depressions of different size the depressions result from the dissolution and collapse of underlying eocene calcareous and gypsiferous materials over which lacustrine sediments of varying thicknesses have accumulated the suspensates occupying the depressions present three main types of seismic signatures stratified semistratified and transparent the densities of the suspensates and the water depths of their tops which fluctuate continuously vary from one depression to another the maximum seismically recorded suspensate thickness is 44 m morphological and structural features seismic characters and variable degrees of hydraulic activity point to the existence of different stages of maturity in the lake bottom depressions this work brings new insight on the dynamics and evolution of limnocrenic solution lakes

joint inversion of body wave receiver function and rayleigh wave ellipticity abstract in recent years surface wave dispersion has been used to image lithospheric structure jointly with receiver function or rayleigh wave ellipticity because surface wave dispersion is the total propagation effect of the travel path the joint inversion relies on dense seismic arrays or high seismicity to obtain local velocity structure however both receiver function and rayleigh wave ellipticity are single station measurements with localized sensitivities and could be combined for joint inversion naturally in this article we explored the feasibility of the joint inversion of rayleigh wave ellipticity and receiver function we performed sensitivity tests with forward modeling and found that the receiver function is sensitive to sharp velocity interfaces but shows weak sensitivity to long wavelength structure almost complementary to rayleigh wave ellipticity therefore joint inversion with two single station measurements provides tighter constraints on the velocity structure beneath the seismic station a joint inversion algorithm based on the fast simulated annealing method is developed to invert rayleigh wave ellipticity and receiver function for the lithospheric structure application of the algorithm to the indian craton and the williston basin in the united states demonstrates its effectiveness in reducing the nonuniqueness of the inversion however the joint inversion may fail to resolve the average crustal velocity suggesting the need to combine surface wave dispersion or other type of observations receiver function and rayleigh wave ellipticity to more accurately resolve the velocity structure

interhemispheric atlantic seesaw response during the last deglaciation the asynchronous relationship between millennial scale temperature changes over greenland and antarctica during the last glacial period has led to the notion of a bipolar seesaw which acts to redistribute heat depending on the state of meridional overturning circulation within the atlantic ocean here we present new records from the south atlantic that show rapid changes during the last deglaciation that were instantaneous within dating uncertainty and of opposite sign to those observed in the north atlantic our results demonstrate a direct link between the abrupt changes associated with variations in the atlantic meridional overturning circulation and the more gradual adjustments characteristic of the southern ocean these results emphasize the importance of the southern ocean for the development and transmission of millennial scale climate variability and highlight its role in deglacial climate change and the associated rise in atmospheric carbon dioxide

surface wave array tomography in se tibet from ambient seismic noise and two station analysis i phase velocity maps summary empirical green s functions egfs between pairs of seismographs can be estimated from the time derivative of the long time cross correlation of ambient seismic noise these egfs reveal velocity dispersion at relatively short periods which can be used to resolve structures in the crust and uppermost mantle better than with traditional surface wave tomography we combine rayleigh wave dispersion estimates from egfs and from traditional two station ts analysis into a new approach to surface wave array tomography with data from dense receiver arrays we illustrate the methodology with continuous broad band recordings from a temporary seismographic network on the southeastern part of the tibetan plateau in sichuan and yunnan provinces sw china the egfs are robust under temporal changes in regional seismicity and the use of either ambient noise approximated by records without signal from events with magnitude mb 5 or 4 or surface wave coda produces similar results the egfs do not strongly depend on the presence of large earthquakes but they are not reciprocal for stations aligned in the n s direction this directionality reflects the paucity of seismicity to the north of the array using a far field representation of the surface wave green s function and an image transformation technique we infer from the egfs the rayleigh wave phase velocity dispersion in the period band from 10 30 s a classical ts approach is used to determine rayleigh wave phase velocity dispersion between 20 120 s together they constrain phase velocity variations for t 10 120 s which can be used to study the structure from the crust to the upper mantle beneath se tibet short and intermediate period 10 80 s phase velocities are prominently low suggesting that the crust and upper mantle beneath se tibet is characterized by slow shear wave propagation

variability in ostracod partition coefficients d sr and d mg implications for lacustrine palaeoenvironmental reconstructions living and sub recent ostracods were collected from four lakes and foul springs located in belgium france and spain characterized by low water mg ca ratios from 0 08 to 0 65 valves of ostracods belonging to cyprideis torosa candona neglecta c marchica and c candida have been extensively analysed for their magnesium and strontium contents with respect to calcium comparisons of these results are made using the same elements from the waters in which the ostracod valves calcified our results offer new and somewhat different interpretations with respect to the uptake of mg and sr in the calcitic ostracod valves these findings include the following 1 the partition coefficient l sr for ostracods belonging to the same genus candona is not a constant the observed variability in d sr values could be due to the rare of biological calcification although more investigations are necessary to assess the influence of this factor it is possible that some taxa grouped under the genus candona belong to a different genus 2 even at the species level cyprideis torosa the ostracod d sr cannot be considered to be constant at low water mg ca ratio 0 65 our d sr value for c torosa is higher than those determined by others for c torosa calcified in evolved marine water 3 the mg ca ratio of the water appears as a major factor influencing d mg for ostracods for low water mg ca values similar to 2 d mg drastically increases this phenomenon is also effective for inorganic calcite implying a non biologic effect that could be linked to mg2 adsorption consequently large variations in me content of fossil ostracod valves from selected lacustrine sequences with expected low water mg ca similar to 2 can be due to small variations in water mg ca c 1998 elsevier science b v all rights reserved

the continental tree ring record absolute chronology 14c calibration and climatic change at 11 ka abstract tree ring chronologies are unique archives for various parameters indicating climatic change the wood structure of trees deposited in river gravel below the water table is well preserved even after several millennia and it provides information on a time scale of solar years during the past 25 years in the hohenheim tree ring laboratory long tree ring chronologies have been constructed now reaching back to 11 400 yr dendro b p in this contribution we demonstrate the evidence for climatic change in the early holocene which can be obtained both from botanical properties e g parameters of ring growth and from the isotopic information recorded in tree rings

the zh ratio method for long period seismic data inversion for s wave velocity structure summary the particle motion of surface waves in addition to phase and group velocities can provide useful information fors wave velocity structure in the crust and upper mantle in this study we applied a new method to retrieve velocity structure using the zh ratio the ratio between vertical and horizontal surface amplitudes of rayleigh waves analysing data from the geoscope network we measured the zh ratios for frequencies between 0 004 and 0 05 hz period between 20 and 250 s and inverted them for s wave velocity structure beneath each station our analysis showed that the resolving power of the zh ratio is limited and final solutions display dependence on starting models in particular the depth of the moho in the starting model is important in order to get reliable results thus initial models for the inversion need to be carefully constructed we chose prem and crust2 0 in this study as a starting model for all but one station ech the eigenvalue analysis of the least squares problem that arises for each step of the iterative process shows a few dominant eigenvalues which explains the cause of the inversion s initial model dependence however the zh ratio is unique in having high sensitivity to near surface structure and thus provides complementary information to phase and group velocities application of this method to geoscope data suggest that low velocity zones may exist beneath some stations near hotspots our tests with different starting models show that the models with low velocity anomalies fit better to the zh ratio data such low velocity zones are seen near hawaii station kip crozet island crzf and djibuti atd but not near reunion island rer it is also found near echery ech which is in a geothermal area however this method has a tendency to produce spurious low velocity zones and resolution of the low velocity zones requires further careful study we also performed simultaneous inversions for volumetric perturbation and discontinuitydepth perturbation while its formulation and inversion were straightforward there seemed to be a difficult trade off problem between volumetric perturbation and discontinuity depth perturbation

glacial to interglacial vegetation changes in the northern and southern pyrenees deglaciation vegetation cover and chronology abstract new palynological investigations have been carried out in the southern northern and mediterranean part of the pyrenean chain pollen percentage and concentration diagrams are compared for a period including the end of the glacial period the late glacial and postglacial periods from the new results and from comparisons with previous published data the steppe and semi desert vegetation of the end of the last glacial period are described as well as the plant communities of the period 15 13 ka a dry climate was responsible for the early glacial retreat before 30 ka deglaciation was continuous up to about 15 14 ka without any readvance around 20 18 ka different aspects of the late glacial vegetation are studied and the first stages of the postglacial are described the younger dryas event is found everywhere but particularly clearly in the mediterranean area the most important 14 c dates are discussed and a plateau of 14 c ages is clearly visible around 10 000 bp

holocene palaeohydrology of lake titicaca estimated from an ostracod based transfer function lacustrine deposits of holocene age 8000 14c yr bp present were studied in lake titicaca bolivia ostracod assemblages were identified in six cores taken in the three basins which today form lake titicaca factorial correspondence and multiple linear regression analysis of the ostracods have permitted the reconstruction of 1 lake level 2 water salinity and 3 water mg ca ratio variations palaeolake levels indicate a complex evolution of the three basins with some major phases after a flooding at about 8000 yr 14c bp the lake level fluctuated around a mean position until 3900 14c yr bp when a second rise took place it seems however that the present day lake level was not reached until after 680 yr 14c bp some major dry events are also recorded at about 5300 14c yr bp and 2300 14c yr bp the lake titicaca data are consistent with other records from south america and also seem to reflect some world wide events

the zh ratio method for long period seismic data sensitivity kernels and observational techniques summary amplitude ratio between vertical and horizontal components of rayleigh waves is controlled by structure beneath a seismic station this ratio measured as a function of frequency has been extensively analysed for shallow crustal structure study in earthquake engineering and applied seismology this quantity termed the zh ratio in this paper may be useful for deep earth structure study and its feasibility for the frequency range between 0 004 and 0 05 hz period 20 250 s is explored in this paper for depth sensitivity kernels we demonstrate that a numerical approach is practical and provides sufficient accuracy for structural inversion depth extent of sensitivity kernels are about half of depth extent in phase velocity kernels indicating that the zh ratio is useful for studying the lithospheric structure two observational approaches for measurement of the zh ratio are presented the first approach uses simple envelope amplitude ratio and the second approach uses waveform correlation technique between vertical and horizontal components the zh ratio data alone only constrains structure beneath seismic stations but recent densification of seismic networks may make it possible to extend the analysis to regional scale structure a greater opportunity may exist in combination of the zh ratio method and the phase and group velocity measurements

the climate in western europe during the last glacial interglacial cycle derived from pollen and insect remains using the pollen sequence of la grande pile xx france we review problems with the application of transfer functions in paleoclimatic reconstructions one of them is to find modern analogues for the herbaceous vegetation of the cold periods we propose a method to distinguish between steppes and tundra vegetations for which the moderns are only partial analogues of the glacial periods another method to solve these problems is based on constraining by insect remains the two methods provide coherent reconstructions the results are also compared with other paleodata there is a good correlation with the six cold heinrich events between 70 and 15 ka b p a cooling event during the eemian period marked by high percentages of taxas at about 125 ka b p needs still to be correlated with high resolution ocean and ice cores

joint inversion of rayleigh wave phase velocity and ellipticity using usarray constraining velocity and density structure in the upper crust rayleigh wave ellipticity or h v ratio observed on the surface is particularly sensitive to shallow earth structure in this study we jointly invert measurements of rayleigh wave h v ratio and phase velocity between 24 100 and 8 100 sec period respectively for crust and upper mantle structure beneath more than 1000 usarray stations covering the western united states upper crustal structure in particular is better constrained by the joint inversion compared to inversions based on phase velocities alone in addition to imaging vs structure we show that the joint inversion can be used to constrain vp vs and density in the upper crust new images of uppermost crustal structure 3 km depth are in excellent agreement with known surface features with pronounced low vs low density and high vp vs anomalies imaged in the locations of several major sedimentary basins including the williston powder river green river denver and san juan basins these results demonstrate not only the consistency of broadband h v ratios and phase velocity measurements but also that their complementary sensitivities have the potential to resolve density and vp vs variations

receiver function tomography of the central tien shan abstract to obtain an image of the deep structure of the tien shan in central asia we invert p and s receiver functions jointly for almost 40 local broad band seismograph stations the inversion is performed using a simulated annealing technique the combined inversion is an improvement on earlier studies where p and s receiver functions were inverted separately using this approach we deal with structural imaging problems that are usually investigated with teleseismic body wave and surface wave tomography techniques we demonstrate that the uppermost mantle in the north of the central tien shan is composed of a high velocity lid a few tens of kilometers thick above a pronounced low velocity zone the crustal structure in this region provides evidence of magmatic underplating these features are likely related to a small plume that is manifested by basaltic eruptions of cretaceous paleogene age the low velocity layer is also found in a southeast trending corridor which may correspond to the bachu uplift in the tarim basin crustal thickness beneath the orogen varies from about 45 to about 70 km the smallest values most likely inherited from the pre orogenic era are found in a neighborhood of the talas fergana fault similar values are characteristic of the kazakh shield in the north and the tarim basin in the south the largest values are found beneath the bounding ranges we infer that uplift of the central tien shan is unlikely to be caused by crustal shortening alone

a wave equation migration method for receiver function imaging 2 application to the japan subduction zone 1 the newly developed wave equation poststack depth migration method for receiver function imaging is applied to study the subsurface structures of the japan subduction zone using the fundamental research on earthquakes and earth s interior anomalies freesia broadband data three profiles are chosen in the subsurface imaging two in northeast ne japan to study the subducting pacific plate and one in southwest sw japan to study the philippine sea plate the descending pacific plate in ne japan is well imaged within a depth range of 50 150 km the slab image exhibits a little more steeply dipping angle 32 in the south than in the north 27 although the general characteristics between the two profiles in ne japan are similar the imaged philippine sea plate in eastern sw japan in contrast exhibits a much shallower subduction angle 19 and is only identifiable at the uppermost depths of no more than 60 km synthetic tests indicate that the top 150 km of the migrated images of the pacific plate is well resolved by our seismic data but the resolution of deep part of the slab images becomes poor due to the limited data coverage synthetic tests also suggest that the breakdown of the philippine sea plate at shallow depths reflects the real structural features of the subduction zone rather than caused by insufficient coverage of data comparative studies on both synthetics and real data images show the possibility of retrieval of fine scale structures from high frequency contributions if high frequency noise can be effectively suppressed and a small bin size can be used in future studies the derived slab geometry and image feature also appear to have relatively weak dependence on overlying velocity structure the observed seismicity in the region confirms the geometries inferred from the migrated images for both subducting plates moreover the deep extent of the pacific plate image and the shallow breakdown of the philippine sea plate image are observed to correlate well with the depth extent of the seismicity beneath ne and sw japan such a correlation supports the inference that the specific appearance of slabs and intermediate depth earthquakes are a consequence of temperature dependent dehydration induced metamorphism occurring in the hydrated descending oceanic crust

lithosphere of the dharwar craton by joint inversion of p and s receiver functions summary the archean dharwar craton in south india is known for long time to be different from most other cratons specifically at station hyderabad hyb the ps converted phases from the 410and 660 km mantle discontinuities arrive up to 2 s later than in other cratons of comparable age which implies lower upper mantle velocities to resolve the unique lithosphere asthenosphere system of the dharwar craton we inverted jointly p and s receiver functions and teleseismic p and s traveltime residuals at 10 seismograph stations this method operates in the same depth range as long period surface waves but differs by much higher lateral and radial resolution we observe striking differences in crustal structures between the eastern and western dharwar craton edc and wdc respectively crustal thickness is of around 31 km with predominantly felsic velocities in the edc and of around 55 km with predominantly mafic velocities in the wdc in the mantle we observe significant variations in the p velocity with depth practically without accompanying variations in the s velocity in the mantle s velocity there are azimuthdependent indications of the hales discontinuity at a depth of 100 km the most conspicuous feature of our models is the lack of the high velocity mantle keel with the s velocity of 4 7 km s 1 typical of other archean cratons the s velocity in our models is close to 4 5 km s 1 from the moho to a depth of 250 km there are indications of a similar upper mantle structure in the northeast of the indian craton and of a partial recovery of the normal shield structure in the northwest a division between the high s velocity western tibet and low s velocity eastern tibet may be related to a similar division between the northeastern and northwestern indian craton

3 d crustal structure of the western united states application of rayleigh wave ellipticity extracted from noise cross correlations we present a new 3 d seismic model of the western united states crust derived from a joint inversion of rayleigh wave phase velocity and ellipticity measurements using periods from 8 to 100 s improved constraints on upper crustal structure result from use of short period rayleigh wave ellipticity or rayleigh wave h v horizontal to vertical amplitude ratios measurements determined using multicomponent ambient noise cross correlations to retain the amplitude ratio information between vertical and horizontal components for each station we perform daily noise pre processing temporal normalization and spectrum whitening simultaneously for all three components for each station pair amplitude measurements between cross correlations of different components radial radial radial vertical vertical radial and vertical vertical are then used to determine the rayleigh wave h v ratios at the two station locations we use all earthscope usarray tranportable array data available between 2007 january and 2011 june to determine the rayleigh wave h v ratios and their uncertainties at all station locations and construct new rayleigh wave h v ratio maps in the western united states between periods of 8 and 24 s combined with previous longer period earthquake rayleigh wave h v ratio measurements and rayleigh wave phase velocity measurements from both ambient noise and earthquakes we invert for a new 3 d crustal and upper mantle model in the western united states correlation between the inverted model and known geological features at all depths suggests good resolution in five crustal layers use of short period rayleigh wave h v ratio measurements based on noise cross correlation enables resolution of distinct near surface features such as the columbia river basalt flows which overlie a thick sedimentary basin

efficient calculation of differential seismograms for lithospheric receiver functions summary a new technique for computing differential seismograms for crustal and upper mantle response to a teleseismic wave receiver functions is developed using the matrix formalism of kennett the work was motivated by the difficulty of modelling teleseismic sv waves and has also proven useful for modelling teleseismic p waves this efficient method for calculating differential seismograms is based on three separate methods for computing synthetic seismograms two of the synthetic seismogram methods save intermediate results then the remaining synthetic seismogram algorithm uses the stored results in an efficient calculation of a new synthetic seismogram for a perturbed velocity model these developments have led to a faster for a 30 layer model a 90 per cent reduction in computation time and more accurate linearized inversion scheme for the determination of velocity models using teleseismic waves

vegetation dynamics and climate during the deglaciation in the south adriatic basin from a marine record the pollen record of a marine core in the south adriatic basin that is radiometrically dated and correlated to the global climate variation by the oxygen isotope curve documents the vegetation changes which occurred around that basin since 17 ka thousands year bp during the end of the last glacial maximum at 16 7 15 ka the altitudinal range is occupied at low and high elevations by a desert and a semi desert dominated by the shrubby sage brush artemisia and at middle elevation by a grass steppe with stands of pine trees where soil conditions are favourable during the deglaciation between 15 and 10 ka a steppe forest with a succession of deciduous trees appears at middle elevation within the grass steppe but its development is interrupted by a set back a re expansion of the semi desert which is coeval with the younger dryas of higher european latitude the holocene is identified by the spread of the mixed deciduous and mediterranean forests which culminates between 8 6 and 6 ka during the end of the boreal and the atlantic chronozones while the most recent sapropel is formed in the deep marine basins of the eastern mediterranean including the south adriatic one between the cold and arid glacial maximum and the warmest and wettest climate optimum during the atlantic chronozone this vegetation dynamics is constrained by the availability of moisture at low elevation by temperature at high elevation and by a combination of both at middle elevation

paleoecology of limnic ostracodes a review of some major topics abstract the paleoecology of limnic ostracodes is reviewd in the context of the evolution of their environment in order to understand why there is a rich ostracode fossil record we examine data such as the quantitative and qualitative distribution of living ostracode species and ostracode assemblages ways of describing and limitations importance of biological and physico chemical factors for the local accumulation of high numbers of ostracodes and diversified assemblages is emphasized we discuss the limits of extrapolations of information from ecology to paleocology we stress how paleontological knowledge can be applied to neontological studies the possibility of using holocene ostracodes as indicators of morphometric changes of lakes temperature salinity eutrophication and as a criterion of meromictic conditions is demonstrated relationships between ostracodes and the chemical environment and particularly the morphological response of the carapace are considered e g diversity and qualitative composition of assemblages and chemical stability types of carapace mineralization and ornamentation and chemistry of bottom waters these ideas developed from studies on recent material are tested for limnic cenozoic faunas in the mesozoic the main questions arising from the study of nonmarine ostracodes deal with the possible evaluation of paleosalinities in marginal lagoonal environments purbeck wealden and with evaluation of depth and hydrochemical and paleoclimatological regime in truly lacustrine intracratonic basins some peculiarities of paleozoic nonmarine ostracode assemblages are described the paleoecological cause of changes in diversity of several ostracode groups in the carboniferous and permian is emphasized

irregular glacial interstadials recorded in a new greenland ice core the greenland ice sheet offers the most favourable conditions in the northern hemisphere for obtaining high resolution continuous time series of climate related parameters profiles of 18o 16o ratio along three previous deep greenland ice cores1 3 seemed to reveal irregular but well defined episodes of relatively mild climate conditions interstadials during the mid and late parts of the last glaciation but there has been some doubt as to whether the shifts in oxygen isotope ratio were genuine representations of changes in climate rather than artefacts due to disturbed stratification here we present results from a new deep ice core drilled at the summit of the greenland ice sheet where the depositional environ ment and the flow pattern of the ice are close to ideal for core recovery and analysis the results reproduce the previous findings to such a degree that the existence of the interstadial episodes can no longer be in doubt according to a preliminary timescale based on stratigraphic studies the interstadials lasted from 500 to 2 000 years and their irregular occurrence suggests complexity in the behaviour of the north atlantic ocean circulation

combined receiver function and surface wave phase velocity inversion using a niching genetic algorithm application to patagonia a combined inversion of body wave receiver functions and rayleigh wave phase velocities using a niching genetic algorithm nga increases the unique ness of the solution over separate inversions and also facilitates explicit parameteri zation of layer thickness in the model space this parameterization requires fewer layers and a priori constraints for modeling more complex structures than traditional linearized inversion ngas solve for a suite of locally optimal solutions in addition to isolating the globally optimal solution by using an evolutionary paradigm this nonlinear examination of the error space provides an opportunity to examine trade off within the model space the method when applied to synthetic data locates interfaces within 2 km of the test structure and identifies appropriate structure and velocity applying this method to data from a deployment of five broadband stations in chilean patagonia yields a regional model of crustal structure that is consistent with the geological history of the region sediment thickness is inversely proportional to crustal thickness with sediment thicknesses reaching more than 4 km where the crustal thickness thins to 28 km this is consistent with previous geological studies which suggests that the rocas verdes basin in western patagonia formed by crustal thinning isostatic compensation and subsequent sedimentation

mid pliocene deep sea bottom water temperatures based on ostracode mg ca ratios abstract we studied magnesium calcium mg ca ratios in shells of the deep sea ostracode genus krithe from a short interval in the middle pliocene between 3 29 and 2 97 ma using deep sea drilling sites in the north and south atlantic in order to estimate bottom water temperatures bwt during a period of climatic warmth results from dsdp and odp sites 552a 610a 607 658a 659a 661a and 704 for the period ma reveal both depth and latitudinal gradients of mean mg ca values shallower sites 552a 610a and 607 have higher mean mg ca ratios 10 3 9 7 10 1 mmol mol than deeper sites 661a 6 3 mmol mol and high latitude north atlantic sites 552a 610a 607 have higher mg ca ratios than low latitude 658a 9 8 mmol mol 659a 7 7 mmol mol 661a 6 3 mmol mol and southern ocean 704 8 0 mmol mol sites converting mg ca ratios into estimated temperatures using the calibration of dwyer et al 1995 dwyer g s cronin t m baker p a raymo m e buzas j s correge t 1995 north atlantic deepwater temperature change during late pliocene and late quaternary climatic cycles science 270 1347 1351 suggests that mean middle pliocene bottom water temperatures at the study sites in the deep atlantic were about the same as modern temperatures however brief pulses of elevated bwt occurred several times between 3 29 and 2 97 ma in both the north and south atlantic ocean suggesting short term changes in deep ocean circulation

a receiver function perspective of the dharwar craton india crustal structure summary teleseismic data from six broad band stations on the south indian shield have been analysed primarily to examine the differences in the crustal structure between the eastern and western units of the archaean dharwar craton sv receiver functions for these stations have been computed and modelled down to the moho level in terms of poisson s ratio and shear wave velocities results show that the crust for the entire dharwar craton is mainly simple and has a low about 0 25 poisson ratio it is usually thinner and less complex than the adjacent proterozoic crust however the western dharwar craton crust thickness 41 km with a gradational moho boundary is substantially 7 km thicker than its eastern counterpart thickness 34 km no substantial differences in average crustal s velocities 3 6 3 8 km s 1 were found the eastern dharwar crust below the proterozoic cuddapah basin was also found to have remained relatively simple and undisturbed the continental margin to the west of the dharwar craton appears to have shifted further west off the coast where a possible west coast fault has down thrown a continental crustal block under the seas the crust constituting the deccan volcanic province in the western indian shield is found to be similar to that of the eastern dharwar craton the crust underneath the neighbouring godavari graben is significantly different from the dharwar crust and resembles that of a typical rift valley

a high resolution palaeoclimatic record for the last 27 500 years in tropical west africa from the carbon and nitrogen isotopic composition of lacustrine organic matter variations in the carbon and nitrogen isotopic composition of bulk organic matter in the sediments of lake bosumtwi ghana reflect climatically induced changes to the lake and the catchment flora cores spanning the last 27 5 kyr of sedimentation in the lake show large oscillations in 13corg pdb and 15norg air the late pleistocene record is particularly detailed showing changes of ca 20 in carbon and ca 10 in nitrogen isotopic compositions these variations are of complex origin although different in magnitude major isotopic excursions in the two records are generally in phase and reveal the occurrence of two major dry intervals at and immediately following the last glacial maximum the allerod younger dryas period also seems to have been marked by generally dry conditions in this part of tropical west africa nitrogen isotopic evidence suggests that during the period 9 2 3 2 kyr the lake had an extremely stable water column probably due to the absence of a windy or cool dry season or both regular circulation of the water column recommenced during the late holocene and has persisted until the present day

oxygen isotope records and salinity changes in the northeastern atlantic ocean during the last 18 000 years a comparison of the deglaciation 18o record of northeastern atlantic core su 81 18 with that calculated by adding the 18o changes due to sea surface temperature and ice volume variations shows that planktonic foraminifera have also recorded seawater 18o changes due to salinity local advection and evaporation precipitation e p changes using a simple ocean box model of meltwater dilution during the deglaciation we show that sea surface salinity covaried with temperature despite the injection of meltwater associated with the climate warming sea surface salinity was high when sea surface water was warm and low during cold events this implies that the combined effect of local e p changes and northward advection of saline subtropical water were the main factor responsible for the surface water salinity variations in the northeastern atlantic ocean during the last 18 000 years

a stable isotope tree ring timescale of the late glacial holocene boundary late glacial and holocene tree ring chronologies like deep sea sediments or polar ice cores contain information about past environments changes in tree ring growth rates can be related to past climate anomalies and changes in the isotope composition of tree ring cellulose reflect changes in the composition of the atmosphere and the hydrosphere we have established a 9 928 year absolutely dated dendrochronological record of holocene oak quercus robur quercus petraea and a 1 604 year floating late glacial and early holocene chronology of pine pinus sylvestris from subfossil tree remnants deposited in alluvial terraces of south central european rivers the pine sequence provides records of dendro dated 14c 13c and 2h patterns for the late younger dryas and the entire preboreal 10 100 9 000 yr bp through the use of dendrochronology radiocarbon age calibration and stable isotope analysis we suggest that the late glacial holocene transition may be identified and dated by 13c and 2h tree ring chronologies

paleosalinity from trace metals in fossil ostracodes compared with observational records at devils lake north dakota usa abstract the chemistry of closed basin lakes responds directly to the hydrologic budget through evaporative concentration of dissolved salts and the sediments of these basins contain several excellent fossil and geochemical proxies for past changes in water chemistry and salinity the trace metal content of ostracode shells among the most promising of these paleosalinity methods is further explored in this study of mg and sr partitioning in candona rawsoni a widespread ostracode of the north american great plains the molar distribution coefficients kd mg and kd sr for this species k d mg ca caco 3 0 004 mg 2 ca 2 h 2 o 9 68 10 5 t c k d sr sr ca caco 3 sr 2 ca 2 h 2 oz 0 406 are determined from laboratory experiments in which c rawsoni are cultured under controlled temperatures and salinities our formulation of kd mg contains a correction term for excess mg that is incorporated into the shell during early calcification the accuracy of the distribution coefficients is tested against field collections of live ostracodes from a suite of 12 dakota lakes the kd inferred values for mg2 ca2 h2o and sr2 ca2 h2o are in close accord with the same ratios measured in the lakes a comparison of ostracode reconstructed and historically measured salinities for devils lake north dakota shows good agreement within the salinity range preferred by c rawsoni 1 10 0 although salinity excursions beyond this optimum are poorly represented in the sedimentary record in most lakes salinity is more readily inferred from mg ca h2o than sr ca h2o because sr solubility is a complex function of several carbonate phases as shown for devils lake sr ca h2o may not vary systematically with the salinity of some brines

joint analysis of teleseismic receiver functions and surface wave dispersion using the genetic algorithm teleseismic p wave receiver function data and rayleigh wave phase velocity measurements are combined using the genetic algorithm a global optimi zation technique to model crustal structure in southern korea the two datasets complement each other because receiver functions are sensitive to shear wave ve locity contrasts in layered structures while surface wave dispersion is sensitive to averages of shear wave velocities the genetic algorithm is more useful than line arized inversion in regions where there is little a priori information about local velocity structure because it is not sensitive to the initial model the stability and variability of resulting crustal model parameters are quantified by using a monte carlo technique in specifying a suite of initial models depths to the moho discon tinuity in southern korea were estimated to be 29 30 km for stations near the western coast and 33 36 km for inland stations a well resolved crustal low velocity zone was inferred for some stations

global nature of the younger dryas cooling event inferred from oxygen isotope data from sulu sea cores the younger dryas an approximately 1 000 year long return to near glacial conditions interrupted the glacial holocene climate transition during which most of the northern hemisphere ice sheets melted evidence for the younger dryas event has been found mainly in sediments from the north atlantic ocean and northwest europe and this has led to the idea that the event was caused by an injection of meltwater into the north atlantic ocean1 3 this model however has been recently questioned in the light of coral reef data on the rate of sea level changes during this transition4 here we present high resolution oxygen isotope records from benthic and planktonic foraminifera from two radiocarbon dated cores in the sulu sea showing that the younger dry as occurred synchronously in the surface and deep waters of the sulu sea and the northern atlantic ocean by combining our results with other palaeoclimate data we suggest that the younger dry as event was a global phenomenon and we believe it to have been caused by low atmospheric co2concentrations

tentative palaeoclimatic reconstruction linking pollen and sedimentology in la grande pile vosges france quantitative values of palaeotemperature and palaeoprecipitation were reconstructed from pollen record in la grande pile guiot et al 1989 some weaknesses appear in the reconstruction particularly for the cold periods and for the periods of deglaciation from sedimentological data i e organic carbon content periglacial loess content and smectite content it is attempted to refine the palaeoclimate reconstruction more accurate values are calculated between the upper and the lower limits of the pollen data during the deltao 18 stages 4 and 2 of the last glacial cycle the climate was the coldest and the driest it was less cold and more humid during the stage 3

seismic evidence for an ancient rift beneath the cumberland plateau tennessee a detailed analysis of broadband teleseismic p waveforms broadband receiver functions developed from teleseismic p waveforms recorded on the midperiod passband of regional seismic test network station rscp are inverted for vertical velocity structure beneath the cumberland plateau tennessee the detailed broadband receiver functions are obtained by stacking source equalizd horizontal components of teleseismic p waveforms the resulting receiver functions are most sensitive to the shear velocity structure near the station a time domain inversion routine utilizes the radial receiver function to determine this structure assuming a crustal model parameterized by many thin flat lying homogeneous layers lateral changes in structure are identified by examining azimuthal variations in the vertical structure the results reveal significant rapid lateral changes in the midcrustal structure beneath the station that are interpreted in relation to the origin of the east continent gravity high located northeast of rscp the results from events arriving from the northeast show a high velocity midcrustal layer not present in results from the southeast azimuth this velocity structure can be shown to support the idea that this feature is part of a keweenawan rift system another interesting feature of the derived velocity models is the indication that the crust mantle boundary beneath the cumberland plateau is a thick probably laminated transition zonemore between the depths of 40 and 55 km a result consistent with interpretations of early refraction work in the area less

quantification of paleotemperature changes during isotopic stage 2 in the la draga continental sequence ne spain based on the mg ca ratio of freshwater ostracods past summer temperature changes are quantified from the la draga sequence banyoles ne spain during stage 2 24 10 ka bp using trace element content in lacustrine ostracod valves the high resolution results from this new method are compared to summer paleotemperature reconstructions from sequences from the north atlantic area providing a discussion about the magnitudes of some temperature changes in ne spain and offshore portugal the coldest part of stage 2 is not documented at the classical date of similar to 18 c 14 ka bp similar to 21 5 calendar ka bp but rather occurred later date of ca 17 15 ka cal bp in the north atlantic area the onset of the bolling allerod interstadials was relatively synchroneous at similar to 14 6 ka cal bp although the magnitude of the bolling allerod improvement was more important in the southern area than in the northern area the duration of the younger dryas is discussed even if different durations are reported from calendar ages it seems that the summer temperature cooling of the younger dryas was similar around the north atlantic area c 1996 elsevier science ltd

sedimentary geochemical and hydrological history of lake kinneret during the past 28 000 years abstract the sedimentary geochemical and hydrological history of lake kinneret sea of galilee is reconstructed for the past 28 kyrs based on three sedimentary cores drilled at the lake and a trench dug at the shore of the prehistorical ohalo ii site during the past 28 kyrs either laminated or massive fine grained sediments were deposited in the lake comprising primary calcites and fine grain detritus sr ca mg ca 87sr 86sr ratios and 18o values of live and fossil ostracod shells cyprideis torosa and primary calcites together with xrd grain size and carbonate content analyses indicate contribution of the following types of waters to the lake 1 jordan river 2 regional runoff and 3 ca chloride brines currently comprises the tiberias spa brine during the last glacial period 28 24 ka the lake rose to its highest stand of 170 m below sea level bsl expanding over the kinnarot basin and converging with the southern hypersaline lake lisan at that time waters were mainly supplied to the lake by the jordan river and regional runoff with enhanced contribution of the dead sea ca chloride brine primary calcites were precipitated from the lake s solution forming sequences of laminated sediments on the lake s floor at 24 22 ka coinciding with heinrich event h2 at the north atlantic the lake retreated below the modern level of 214 m bsl depositing mainly flood related sediments at its margins the lake slightly rose during the younger dryas and subsequently declined towards the modern level with decreasing contributions of the jordan river waters brines and regional runoff reflecting a continuous aridification of the region during the holocene

application of very fast simulated annealing to the determination of the crustal structure beneath tibet summary the simulated annealing method has recently been applied to several multiparameter optimization problems including those of geophysical inversion a new variant of simulated annealing called very fast simulated annealing vfsa overcomes some of the drawbacks of a conventional simulated annealing it has been found to be a practical tool for geophysical inversion sen stoffa 1995 the method is particularly useful for non linear problems with multiple parameters where a grid search method is prohibitively expensive here we have applied vfsa to retrieve the crustal structure beneath seismic stations in tibet using teleseismic body waveform data our approach is to compare the radial component records with generalized ray synthetics directly in the time domain for any given crustal structure we have formulated a direct relationship between the radial and the vertical component signal so that we can generate synthetic radial component data from recorded vertical component seismograms zhao frohlich 1996 we have tested the vfsa inversion algorithm using synthetics and confirmed that it works very well i e it finds solutions very close to the true solution using the algorithm we have determined the crustal structures beneath 11 stations in tibet from south to north the total crustal thickness is quite uniform our tectonic interpretation of these crustal models is that they may represent crust from the eurasian plate injected beneath the crust of the converging indian plate certain features of the models are consistent with the presence of a small convection cell or plume beneath north central tibet as suggested by molnar 1990

multi isotopic age assessment of dirty speleothem calcite an example from altamira cave spain the dating of dirty speleothem calcite of late pleistocene or holocene age can be problematic this is notably the case with the 14 c method due to uncertainties in the initial 14 c activity of the cave co2 and withth e 230 th 234 u method due to either low u contents in the authigenic calcite and or to the presence of heterogeneous detrital particles containing high concentrations of u and thseries isotopes frequently out of secular equilibrium in this study of a b60 cm thick flowstone sealing archaeological remains of the magdalenian period in the altamira cave nw spain we used a combination of isotopic approaches and analytical techniques to confront dating methods and finally tried to validate chronological interpretations based on stable isotope paleoclimate constraints u series data indicate the presence of a relatively important and heterogeneous detrital fraction resulting in 232 th 230 th mass ratios generally too high 0 1 0 25 10 6 to allow precise tims measurements mc icp ms measurements provided more reliable results and allowed the calculation of 230 th 234 u isochron ages of 11 870 8 ka in the upper part of the flowstone and of b22 ka in the lower part of it in view of the calibrated 14 c ages of these layers b13 and b15 ka bp respectively the isochron age of the lower unit of the flowstone seems erroneous suggesting the presence of an isotopically heterogeneous contaminating fraction in this layer 226 ra 230 thratio measurements indicate near secular equilibrium conditions seriate stable isotope measurements indicate calcite precipitation in isotopic equilibrium with ambient waters they suggest that flowstone deposition ended at the very onset of the younger dryas this transition seems to have occurred here at 11 870 8 72s ka based on th u isochron and 10 770 08 71s uncalibrated 14 c kiloyears the 14 c activity for the cave co2 seems to have been near that of atmospheric co2 during the precipitation interval it is concluded that the 14 c data provide here relatively reliable ages in spite of the fact that they partly fall into a period characterized by 14 c plateau effects but that other isotopic data revealed essential in validating them

retreat velocity of the north atlantic polar front during the last deglaciation determined by 14 c accelerator mass spectrometry the glacial oscillations which dominate the quaternary global climate are closely related to changes in incoming solar radiation but the details of palaeoclimatic spectra suggest that other parameters usually referred to as feedback have significantly increased the climatic response to extraterrestrial forcing1 the last deglaciation appears to be one of the more characteristic examples of nonlinearity because its abruptness strongly contrasts with the smooth shape of the associated solar radiation maximum dated at 11 000 yr bp in addition the presence of the younger dryas cold event concomitant with the solar radiation maximum could be interpreted as a transitory phenomenon caused by the rapid meltwater influx linked to the first phase of the ice sheet s disintegration2 3 here using accelerator mass spectrometry we date precisely the movements of the polar front during the whole period of glacial retreat 15 000 8 000 yr bp our results show that the polar front has moved between 35 n and 55 n in 1 000 yr for the earliest retreat 12 500 12 000 bp and moved almost instantaneously that is 400 yr during the two abrupt climatic changes associated with the younger dry as cold event

ambient noise rayleigh wave tomography of new zealand summary we present the first new zealand wide study of surface wave dispersion using ambient noise observed at 42 broad band stations in the national seismic network geonet and the global seismic network gsn year long vertical component time series recorded between 2005 april 1 and 2006 march 31 have been correlated with one another to yield estimated fundamental mode rayleigh wave green s functions we filter these green s functions to compute rayleigh wave group dispersion curves at periods of 5 50 s using a phase matched filter frequency time analysis technique the uncertainties of the measurements are estimated based on the temporal variation of the dispersion curves revealed by 12 overlapping 3 month stacks after selecting the highest quality dispersion curve measurements we compute group velocity maps from 7 to 25 s period these maps and 1 d shear wave velocity models at four selected locations exhibit clear correlations with major geological structures including the taranaki and canterbury basins the hikurangi accretionary prism and previously reported basement terrane boundaries

seismic properties of the central indian shield we use broadband seismic data at hyderabad to investigate average crustal properties of the central indian shield crustal receiver functions p to sv conversions based on data of excellent quality and azimuthal coverage show essentially no signal on the transverse component indicating laterally homogeneous structures near this station a joint analysis of receiver functions and the dispersion of fundamental mode rayleigh waves result in a simple model for the shear wave speed v s with a moderate gradient of 0 010 0 028 km sec km in the crust the moho is sharp with a contrast of approximately 0 7 km sec in v s across a small thickness of only 0 4 km measured from the middle of the moho region the crust is 30 34 km thick with an average v s of 3 58 0 10 km sec by modeling the timing and waveforms of sp and sspmp phases sv to p conversions we estimate the average crustal poisson9s ratio to be 0 26 0 01 this value is comparable to that found in the tanzanian craton which is also of archean age both values being somewhat lower than the global average of 0 29 0 02 for shield regions that include both proterozoic and archean crust a low poisson9s ratio and a slow v s in the crust indicate that on average archean crust beneath the central indian shield is intermediate to felsic in composition somewhat less mafic than globally averaged precambrian crust

a multistep approach for joint modeling of surface wave dispersion and teleseismic receiver functions implications for lithospheric structure of the arabian peninsula 1 we present a multiple step procedure for joint modeling of surface wave group velocity dispersion curves and teleseismic receiver functions for lithospheric velocity structure the method relies on an initial grid search for a simple crustal structure followed by a formal iterative inversion an additional grid search for shear wave velocity in the mantle and finally forward modeling of transverse isotropy to resolve love rayleigh surface wave dispersion discrepancy it considers longer period surface wave group velocity swgv dispersion allowing for the resolution of deeper structure compared to previous joint inversions the grid search for simple crustal structure is facilitated using a library of precomputed receiver functions and swgv dispersion curves the iterative inversion improves fit to the data by increasing the number of layers in the crust when necessary in order to fit the swgv for periods greater than about 50 s we perform a grid search over mantle velocities including the mantle lid and low velocity zone keeping the crustal structure fixed to the values from the previous step in some cases a clear love rayleigh discrepancy prevents a simultaneous fit of the group velocities with an isotropic model the love rayleigh discrepancy can be resolved by allowing shear wave transverse isotropy with a vertical symmetry axis vsh vsv differences in the uppermost mantle the method is applied to 10 stations in the arabian peninsula sampling various tectonic environments including active continental rifting and stable regions the resulting shear velocity models confirm rapid crustal thinning of the arabian shield toward the red sea however we do not find strong evidence for crustal thickening toward the arabian platform our results suggest that the mantle lithosphere thickness varies regionally but that the mantle shear velocities beneath the arabian shield and red sea coast are generally anomalously low furthermore our results indicate the presence of strong polarization anisotropy up to about 10 in the lithospheric upper mantle in the vicinity of as well as farther away from the red sea our modeling yields vsv vsh in the southwestern part of the arabian peninsula consistent with vertical flow and vsh vsv in the northwestern part of the arabian peninsula and the continental interior consistent with horizontal flow indicating that the mantle flow pattern is not uniform along the axis of the red sea

δ18o and δ13c of cyprideis torosa from coastal lakes modern systematics and down core interpretation abstract stable isotope analyses of ostracod shells are a commonly used proxy for palaeoenvironmental reconstruction although the fundamental controls on isotope composition of ostracod shells are well understood and in some instances quantifiable the paleoclimatic and palaeoenvironmental interpretation of records from lake sediments depends strongly on the characteristics of individual lakes including the climatic setting depth volume hydrology aquatic vegetation and catchment properties this is particularly important for coastal lakes where physio chemical variations may occur on diurnal timescales here we combine variations in 18owater 18oostracod and 13costracod hourly water temperature and mg caostracod inferred water temperatures constraining calcification temperature to improve palaeoenvironmental interpretation and provide insights into lake carbon cycle the dataset improves understanding of complex coastal lake site systematics and downcore interpretation of stable isotopes from c torosa a geographically widespread brackish water ostracod the 18oostracod values show a complex relationship with temperature and suggest in most circumstances that 18owater is the dominant control on 18oostracod during times of fresher water 13costracod increases suggesting increasing aquatic productivity above a certain 18owater threshold however aquatic productivity begins to decline the interpretation of 13costracod in some coastal lakes may therefore be dependent on understanding of the range of expected 18owater due to short term diurnal to seasonal variations that cause large ranges in 18owater and 18oostracod stable isotope analyses of c torosa should be 1 undertaken on multiple single shells 2 where carapaces are preserved paired with trace element ca analyses on the same individual and 3 undertaken alongside a study of the modern lake system