modification and preservation of environmental signals in speleothems speleothems are primarily studied in order to generate archives of climatic change and results have led to significant advances in identifying and dating major shifts in the climate system however the climatological meaning of many speleothem records cannot be interpreted unequivocally this is particularly so for more subtle shifts and shorter time periods but the use of multiple proxies and improving understanding of formation mechanisms offers a clear way forward

holocene climate variability archived in the puruogangri ice cap on the central tibetan plateau two ice cores 118 4 and 214 7 m in length were collected in 2000 from the puruogangri ice cap in the center of the tibetan plateau tp in a joint us chinese collaborative project these cores yield paleoclimatic and environmental records extending through the middle holocene and complement previous ice core histories from the dunde and guliya ice caps in northeast and northwest tibet respectively and dasuopu glacier in the himalaya the high resolution puruogangri climate record since ad 1600 details regional temperature and moisture variability the post 1920 period is characterized by above average annual net balance contemporaneous with the greatest 18 o enrichment of the last 400 years consistent with the isotopically inferred warming observed in other tp ice core records on longer timescales the aerosol history reveals large and abrupt events one of which is dated 4 7 kyr bp and occurs close to the time of a drought that extended throughout the tropics and may have been associated with centuries long weakening of the asian indian african monsoon system the puruogangri climate history combined with the other tp ice core records has the potential to provide valuable information on variations in the strength of the monsoon across the tp during the holocene

speleothem architectural analysis integrated approach for stalagmite based paleoclimate research this work was supported by the r d i program of spain cgl2013 43257 r and the universidad complutense de madrid research group 910198

a high resolution proxy record of rainfall and enso since ad 1550 from layering in stalagmites from anjohibe cave madagascar two stalagmites from anjohibe cave have annual layers made up of inclusion rich calcite over inclusion free calcite or of darker aragonite over clear aragonite geochemical evidence indicates that the basal units are deposited slowly in the wet season and the upper units more rapidly in the dry season for the period with rainfall and temperature data ad 1951 1992 layer thickness correlates well with the southern oscillation index soi as well as rainfall water surplus and actual evapotranspiration aet at nearby majunga com parison of the layer record for one stalagmite with 1866 1994 soi data indicates that layer thickness correlates best with the frequency and intensity of warm low phase so el nino events not with average soi conditions in addition the 415 year layer thickness time series from that speleothem agrees remarkably well with historical records of el nino frequency with galapagos ecuador coral records of sea surface temperature in the eastern pacific and with accumulation

seismic attenuation structure of the seattle basin washington state from explosive source refraction data we used waveform data from the 1999 ships seismic hazard inves tigation of puget sound seismic refraction experiment to constrain the attenuation structure of the seattle basin washington state we inverted the spectral amplitudes of compressional and shear wave arrivals for source spectra site responses and one and two dimensional q 1 models at frequencies between 1 and 40 hz for p waves and 1 and 10 hz for s waves we also obtained q 1 models from t values calculated from the spectral slopes of p waves between 10 and 40 hz one dimen sional inversions show that qp at the surface is 22 at 1 hz 130 at 5 hz and 390 at 20 hz the corresponding values at 18 km depth are 100 440 and 1900 qs at the surface is 16 and 160 at 1 hz and 8 hz respectively increasing to 80 and 500 at 18 km depth the t inversion yields a qp model that is consistent with the amplitude inversions at 20 and 30 hz the basin geometry is clearly resolved in thet inversion but the amplitude inversions only imaged the basin structure after removing anom alously high amplitude shots near seattle when these shots are removed we infer that q 1 values may be 30 higher in the center of the basin than the one dimensional models predict we infer that seismic attenuation in the seattle basin will significantly reduce ground motions at frequencies at and above 1 hz partially countering amplification effects within the basin

intra and inter annual growth rate of modern stalagmites we measure the factors that determine growth rate temperature drip rate calcium ion concentration for 31 waters that feed stalagmites within six cave systems throughout europe water samples were collected at a frequency of at least 1 month to permit the modelling of both inter and intra annual growth rate variations utilising the theory of wolfgang dreybrodt chem geol 29 1980 89 105 chem geol 32 1981 237 245 dreybrodt w 1988 processes in karst systems springer verlag berlin 288 pp inter annual growth rates were measured using the stalagmites that were associated with the analysed water samples growth rate was determined from annual lamina counting specific time markers within the stalagmites and location of bomb 14c when compared to theoretically predicted values a good agreement between theoretical and measured stalagmite growth rates is observed r2 0 69 when compared to site climate and geochemical parameters a good correlation is observed between measured growth rate and mean annual temperature for five sites r2 0 63 and dripwater calcium content r2 0 61 but not drip rate r2 0 09 the good correlation with both calcium and temperature is due to soil co2 production being primarily determined by surface temperature and soil moisture however when we compare our data to that in the grotte de clamouse a site that has little soil cover we observe that the growth rate temperature relationship breaks down due to either the lack of soil co2 production or prior calcite precipitation intra annual data demonstrates that maximum growth rate occurs when calcium concentrations are high and that this occurs under different seasons depending on the hydrology of each site our results demonstrate a stronger dependence of intra annual stalagmite growth rate on dissolved calcium ion concentrations than drip rate for the range of drip rates investigated here 0 01 t 2drip s 1 but for lower drip rates this factor becomes important in controlling growth rate we suggest that for well monitored and understood sites stalagmite growth rate variations can provide useful information for palaeoclimate reconstruction

is chinese stalagmite δ 18 o solely controlled by the indian summer monsoon as a unique continental archive speleothem has been widely used in reconstructing paleoclimate change however the interpretation of chinese speleothems 18o has remained a subject of debate recently a community atmosphere model version 3 cam3 study indicated that the stalagmite 18o from eastern china reflected the indian summer monsoon ism intensity rather than the east asian summer monsoon easm intensity during heinrich events here we present a high resolution speleothem 18o record from xianglong cave in shaanxi province china covering the period of 25 5 10 9 ka bp the xl15 record shows similar variations with ice core record from greenland and other climate records from china and india on millennial scale including heinrich 2 h2 heinrich 1 h1 bolling allerod ba and younger dryas yd events supporting the connection between the asian monsoon and northern high latitude climate the 18o amplitude of our record is larger than or similar to the stalagmite 18o records from india during these events in addition differences of stalagmite 18o in eastern china and the ism region were observed on glacial interglacial as well as decadal timescales that means the ism is not the sole controlling factor of chinese stalagmite 18o during heinrich events when subtracting the indian stalagmite 18o series from our xl15 record during h1 period we found a significant negative correlation with sea surface temperature sst record of western pacific warm pool wpwp consequently our study suggests that the chinese stalagmite 18o is controlled by both the ism and easm on orbital millennial and decadal timescales

solid pole tide in global gps and superconducting gravimeter observations signal retrieval and inference for mantle anelasticity abstract the mantle anelasticity plays an important role in earth s interior dynamics here we seek to determine the lower mantle anelasticity through the solution of the complex love numbers at the chandler wobble period the love numbers h 21 l 21 21 and k 21 are obtained in the frequency domain by dividing off the observed polar motion or more specifically the pole tide potential from the observed gps 3 d displacement field and sg gravity variation the latter signals are obtained through the array processing method of ose optimal sequence estimation that results in greatly enhanced signals to be extracted from global array data the resultant love number estimates h 21 0 6248 5 e 4 0 013 5 e 3 i l 21 0 0904 8 e 4 0 0008 2 e 3 i 21 1 156 2 e 3 0 003 1 e 3 i and k 21 0 3125 2 e 3 0 0069 3 e 3 i are thus well constrained in comparison to past estimates that vary considerably they further lead to estimates of the corresponding mantle anelastic parameters f r and f i which in turn determines under the single absorption band assumption the dispersion exponent of 0 21 0 02 with respect to the reference frequency of 5 mhz we believe our estimate is robust and hence can better constrain the mantle anelasticity and attenuation models of the earth interior

investigation for anisotropic attenuation in the pacific summary anisotropic attenuation arises through preferential orientation of dislocations crystals and scattering bodies as seismic energy loss is an exponential function of distance whereas traveltime is a linear function attenuation anisotropy is potentially as important as velocity anisotropy in an examination for anisotropic attenuation oceanic s waves so were analysed from 10 earthquakes near hokkaido japan which were recorded naturally rotated into sv and sh components of motion at the hig borehole seismometer in the northwest pacific oss iv some evidence for velocity polarization anisotropy is seen the observed sv sh amplitude ratios which vary from 1 2 to 2 limit the possible contribution of scattering between orthogonal components of motion the effect of local scattering of sv into sh and vice versa which contaminates the measurement can be estimated from observed transverse energy on p waves in the frequency band with a good signal to noise ratio 3 to 20 hz the so phases have propagated about 900 6000 wavelengths spectral ratios of sv over sh are formed for each event frequency independent source propagation and receiver effects are removed by normalizing the spectra the normalized spectral ratios are then stacked the resultant stacked data are essentially flat varying by less than 15 per cent about their geometric mean with no frequency dependent trend the results are consistent with q values of sv polarized shear waves within 5 per cent of those for sh polarized shear waves

a 780 year annually resolved record of indian ocean monsoon precipitation from a speleothem from south oman 1 meteorological records of monsoon rainfall in the indian ocean are generally less than 100 years long the relative brevity of these records makes it difficult to investigate monsoon variation on decadal and centennial timescales to determine what factors influence the intensity of rainfall on these timescales or to place possible changes in the twentieth century into a broader historical context development of a geologic proxy for rainfall that records annual variation in the monsoon over much longer time periods than are covered by instrumental records would be a significant step forward we have developed an annually resolved record of monsoon rainfall variation for the past 780 years based on annual layer thickness and stable isotope analyses of a laminated stalagmite from southern arabia our results show that monsoon variation over the past century is not outside of the range of the past 800 years decreasing monsoon rainfall over the past century is related to increasing sea surface temperature in the indian ocean spectral analyses of the record are dominated by cycles that are similar to those observed in records of solar activity on centurial timescales decadal to interannual cycles in the record appear to originate in the tropical pacific ocean index terms 3344 meteorology and atmospheric dynamics paleoclimatology 3354 meteorology and atmospheric dynamics precipitation 1854 1620 global change climate dynamics 3309 1699 global change general or miscellaneous keywords monsoon paleoclimate rainfall indian ocean speleothem oxygen isotopes

lateral velocity variations in southern california i results for the upper crust from pg waves the plate boundary and major crustal blocks in southern california are imaged by a tomographic backprojection of the pg first arrivals recorded by the southern california array the method formulated specifically for local earthquake arrival times is a fast iterative alternative to direct least squares techniques with it we solve the combined problem of determining refractor velocity perturbations and source and station delays resolution and variance are found empirically by using synthetic examples a map showing lateral velocity variations at a depth of approximately 10 km is presented the results show a strong correlation with surface tectonic features clear velocity contrasts exist across the san andreas the san jacinto and the garlock faults the mojave region has the slowest velocities while the peninsula ranges have the highest the san jacinto block has velocities intermediate between mojave and peninsula range velocities and also has early station delays this may indicate that the san jacinto block has overridden mojave material on a shallow detachment surface no velocity variations are found associated with the transverse ranges which we interpret to mean that the surface batholithic rocks in this area do not extend to pg depths

a thousand year speleothem proxy record of north atlantic climate from scotland luminescent organic matter in stalagmites may form annual bands allowing growth rate to be precisely determined stalagmite growth rate is controlled by precipitation so annual bands can be used to derive long precipitation records a continuously banded stalagmite from a cave in nw scotland was used to provide a 1100 year high resolution record of precipitation the location of the cave means that precipitation is closely linked to the north atlantic oscillation for which a record is also derived this suggests that changes in the north atlantic oscillation state was an important control on european climate over the past millennium

amino acid racemization geochronology of reworked quaternary mollusks on u s atlantic coast beaches implications for chronostratigraphy taphonomy and coastal sediment transport approximately 200 shells primarily mercenaria from 21 beach sites between new jersey and florida have been analyzed for the extent of racemization epimerization of their fossilized amino acids the greatest concentration of sites is in north carolina in regions least affected by human modification of natural beach sediment transport processes these results can be used to estimate the frequency of age mixing of pleistocene shell material in holocene depositional environments selected shells have also been dated by 14c conventional and or ams to provide direct calibration of the amino acid epimerization ratios shell taphonomic characteristics particularly color can be qualitatively related to apparent ages data for shell fragmentation combined with amino acid age estimates provide insights into probable transport distances of reworked shells shells with apparent pleistocene ages have epimerization values equivalent to those seen in onshore exposures of pleistocene coastal units amino acid epimerization measurements are a comparatively rapid and inexpensive chronologic tool for use in taphonomic and sediment shell transport studies paired amino acid 14c analyses on single shells provide insights into geochemical alteration of shells and permit modelling of the residence time of shells on beaches greater numbers of analyses at each site are needed before statistically valid estimates of age mixing can be obtained but the apparent distribution of pleistocene shells on atlantic coast beaches appears to be related to the distribution of pleistocene units in the shoreface and inner shelf and the thickness of holocene sedimentary cover in specific areas these observations provide useful criteria for the evaluation of possible age mixing of shells collected at outcrops of pleistocene units in the coastal plain

carbon and oxygen isotope study of the active water carbonate system in a karstic mediterranean cave implications for paleoclimate research in semiarid regions abstract in a semiarid climatic zone such as the eastern mediterranean region annual rainfall variations and fractionation processes in the epikarst zone exert a profound influence on the isotopic compositions of waters seeping into a cave consequently the isotopic compositions of speleothems depositing from cave waters may show complex variations that need to be understood if they are to be exploited for paleoclimate studies this is confirmed by a four year study of the active carbonate water system in the soreq cave israel the 18o smow values of cave waters range from 6 3 to 3 5 the highest 18o values occur at the end of the dry season in waters dripping from stalactites and reflect evaporation processes in the epikarst zone whereas the lowest values occur in rapidly dripping fast drip waters at the peak of the rainy seasons however even fast drip waters are about 1 5 heavier than the rainfall above the cave which is taken to reflect the mixing of fresh with residual evaporated water in the epikarst zone 13c pdb values of dissolved inorganic carbon dic vary from 15 6 to 5 4 with fast drip waters having lower 13c values mostly 15 6 to 12 and higher dic concentrations relative to pool and stalactite drip water the low 13c values of fast drip waters and their supersaturation with respect to calcium carbonate indicates that the seepage waters have dissolved both soil co2 derived from overlying c3 type vegetation and marine dolomite host rock the 18o pdb values of various types of present day low magnesium calcite lmc speleothems range from 6 5 to 4 3 and 13c values from 13 to 5 5 and are not correlated with speleothem type an analysis of 18o values of present day calcite rafts and pool waters shows that they form in oxygen isotope equilibrium similarly the measured ranges of 13c and 18o values for all types of present day speleothems are consistent with equilibrium deposition at cave temperatures the 13c 18o range of contemporary lmc thus reflects the variations in temperatures and isotopic compositions of the presentday cave waters the 10 variation in the 13c values in waters can be modeled by a simple rayleigh calculation of the carbon isotope fractionation accompanying co2 degassing and carbonate precipitation these variations may obscure the differences in the carbon isotopic composition of speleothems that could arise when vegetation cover changes from c3 to c4 type plants this consideration emphasizes that it is necessary to characterize the full range of 13c values associated with contemporaneous speleothems in order to clarify the effects of degassing from those due to differing vegetation types isotopic studies of a number of different types of fossil lmc speleothems show many of them to exhibit isotopic trends that are similar to those of present day lmc but others show both higher and lower 18o ranges in particular the higher 18o range has been shown by independent age measurements to be associated with a period of drier conditions the results of the study thus indicate that it is necessary to work on a well calibrated cave system in semiarid climates and that the fossil speleothem record should be obtained from different types of contemporaneous deposit in order to fully characterize the 18o 13c range representative of any given climatic period

cyclic rapid warming on centennial scale revealed by a 2650 year stalagmite record of warm season temperature 1 a 2650 year bc665 ad1985 warm season mjja may june july august temperature reconstruction is derived from a correlation between thickness variations in annual layers of a stalagmite from shihua cave beijing china and instrumental meteorological records observations of soil co2 and drip water suggest that the temperature signal is amplified by the soil organism co2 system and recorded by the annual layer series our reconstruction reveals that centennial scale rapid warming occurred repeatedly following multicentenial cooling trends during the last millennia these results correlate with different records from the northern hemisphere indicating that the periodic alternation between cool and warm periods on a sub millennial scale had a sub hemispherical influence

reconstruction of late holocene autumn winter precipitation variability in sw romania from a high resolution speleothem trace element record abstract we present the first high resolution trace element mg ca sr ca ba ca record from a stalagmite in southwestern romania covering the last 3 6 ka which provides the potential for quantitative climate reconstruction precise age control is based on three independent dating methods in particular for the last 250 yr where chemical lamina counting is combined with the identification of the 20th century radiocarbon bomb peak and 230th u dating long term cave monitoring and model simulations of drip water and speleothem elemental variability indicate that precipitation related processes are the main drivers of speleothem mg ca ratios calibration against instrumental climate data shows a significant anti correlation of speleothem mg ca ratios with autumn winter october to march precipitation r 0 61 p during the late holocene our data suggest a heterogeneous pattern of past regional winter hydroclimate in the carpathian balkan realm along with intermittent weakening of the dominant influence of north atlantic forcing in agreement with other regional paleo hydrological reconstructions the observed variability reveals periodically occurring strong nw se hydro climate gradients we hypothesize that this pattern is caused by shifts of the eastern edge of the area of influence of the nao across central eastern europe due to the confluence of north atlantic forcing and other climatic features such as the east atlantic western russia eawr pattern

taphonomic trade offs in tropical marine death assemblages differential time averaging shell loss and probable bias in siliciclastic vs carbonate facies radiocarbon calibrated amino acid racemization ages of individually dated bivalve mollusk shells from caribbean reef nonreefal carbonate and siliciclastic sediments in panama indicate that siliciclastic sands and muds contain significantly older shells median 375 yr range up to 5400 yr than nearby carbonate seafloors median 72 yr range up to 2900 yr maximum shell ages differ significantly at p 0 02 using extreme value statistics the implied difference in shell loss rates is contrary to physicochemical expectations but is consistent with observed differences in shell condition greater bioerosion and dissolution in carbonates higher rates of shell loss in carbonate sediments should lead to greater compositional bias in surviving skeletal material resulting in taphonomic trade offs less time averaging but probably higher taxonomic bias in pure carbonate sediments and lower bias but greater time averaging in siliciclastic sediments from humid weathered accretionary arc terrains which are a widespread setting of tropical sedimentation

aminochronology and time averaging of quaternary land snail assemblages from colluvial deposits in the madeira archipelago portugal understanding the properties of time averaging age mixing in a stratigraphic layer is essential for properly interpreting the paleofauna preserved in the geologic record this work assesses the age and quantifies the scale and structure of time averaging of land snail rich colluvial sediments from the madeira archipelago portugal by dating individual shells using amino acid racemization calibrated with graphite target and carbonate target accelerator mass spectrometry radiocarbon methods gastropod shells of actinella nitidiuscula were collected from seven sites on the volcanic islands of bugio and deserta grande desertas islands where snail shells are abundant and well preserved in quaternary colluvial deposits results show that the shells ranged in age from modern to 48 cal ka bp calibrated radiocarbon age covering the last glacial and present interglacial periods snail shells retrieved from two of the colluvial sites exhibit multimillennial age mixing 6 ka which significantly exceeds the analytical error from dating methods and calibration the observed multimillennial mixing of these assemblages should be taking into consideration in upcoming paleoenvironmental and paleoecological studies in the region the extent of age mixing may also inform about the time span of colluvial deposition which can be useful in future geomorphological studies in addition this study presents the first carbonate target radiocarbon results for land snail shells and suggests that this novel rapid and more affordable dating method offers reliable age estimates for small land snail shells younger than 20 cal ka bp

a critical review of mid to late holocene sea level fluctuations on the eastern brazilian coastline abstract the eastern coast of brazil is 7000 km long and has been the subject of systematic paleo sea level investigations for more than 35 years more than 1000 samples have been radiocarbon dated and paleo sea level trends have been determined for 14 coastal sectors these trends have in common a mid holocene sea level maximum pmt above present sea level and a subsequent fall to the present time the time and elevation of the pmt the time when relative sea level rose above present mean sea level and the nature of late holocene sea level fall can however differ significantly discrepancies are observed not only between neighboring coastal sectors but also between different studies in a same coastal sector this paper discusses all the key radiocarbon dated samples used to establish regional trends in relative sea level on the eastern coast of brazil it is concluded that although many of the key sea level indicators are imprecise in time and space there is widespread evidence 30 of the data set for a progressive decline possibly with uneven rates of relative sea level since the end of the pmt

drought reconstructions for the continental united states abstract the development of a 2 lat 3 long grid of summer drought reconstructions for the continental united states estimated from a dense network of annual tree ring chronologies is described the drought metric used is the palmer drought severity index pdsi the number of grid points is 154 and the reconstructions cover the common period 1700 1978 in producing this grid an automated gridpoint regression method called point by point regression was developed and tested in so doing a near optimal global solution was found for its implementation the reconstructions have been thoroughly tested for validity using pdsi data not used in regression modeling in general most of the gridpoint estimates of drought pass the verification tests used in addition the spatial features of drought in the united states have been faithfully recorded in the reconstructions even though the method of reconstruction is not explicitly spatial in its design the drought reconstructions show that the 1930s dust bow

late holocene annual growth in three alpine stalagmites records the influence of solar activity and the north atlantic oscillation on winter climate annual growth rates and the ratio of dark to light colored calcite within single annual laminae in three contemporaneously deposited holocene speleothems from grotta di ernesto an alpine cave in northern italy respond to changes in surface temperature rather than precipitation based on monitoring of present day calcite growth and correlation with instrumental data for surface climatic conditions we interpret a higher ratio of dark to light colored calcite and the simultaneous thinning of annual laminae as indicative of colder than present winters such dark and thin laminae occur in those parts of the three stalagmites deposited from ad 1650 to 1713 and from ad 1798 to 1840 as reconstructed through lamina counting these periods correspond to the well known maunder and dalton minima of solar activity an 11 yr cyclicity in growth rate coupled with reduced calcite deposition during the historic minima of solar activity is indicative of a solar influence on lamina thickness spectral analysis of the lamina thickness data also suggests that the north atlantic oscillation variability influenced winter temperatures based on the present day controls on cave calcite formation we infer that high frequency changes in solar activity modulated the seasonal duration of soil co2 production

testing theoretically predicted stalagmite growth rate with recent annually laminated samples implications for past stalagmite deposition annually laminated stalagmites deposited over the last 30 160 years are analysed to determine their growth rate three natural and artificial cave sites in england france and belgium were chosen for their wide range of variability in growth rate determining variables and multiple samples were taken from each site the annual nature of laminae deposition within the stalagmite calcite was confirmed by comparison to the date of cave void opening 14c analyses or by using dated event horizons measured stalagmite growth rate was determined from annual laminae thickness measurements and compared to that theoretically predicted from the chemical kinetics of the calcite precipitation reaction a good agreement is observed between empirical observations and theoretical predictions although two complicating factors variations in calcite porosity and seasonal cessation of the water supply to the samples both affect the growth rate implications for the extraction of palaeoclimate information from stalagmite growth rate are discussed

trace element variations in an annually layered stalagmite as recorders of climatic changes and anthropogenic pollution in central china abstract we analyzed variations in the sr ca ba ca ree ca ree rare earth element zn ca and pb ca ratios preserved in an annually layered stalagmite xl21 from central china the stalagmite record spans the 95 year period ad 1914 2008 the sr ca and ba ca ratios have a significant positive correlation with the stalagmite s growth rate suggesting that they were primarily controlled by growth rate variations variations in ree ca ratios are consistent with local temperature changes suggesting temperature influenced ree concentrations in the stalagmite over decadal to annual timescales higher temperature in this humid area can increase vegetation cover microbial activity and organic decomposition in the soil resulting in enhanced pco2 organic matter concentration and reduced ph and consequently increased ree mobilization from the overlying soil layer and host rock higher temperatures may also increase the natural zn mobilization from the overlying soil mediated by organic matter and consequently may have led to increased zn retention in xl21 an increasing trend is seen in the pb ca ratios from xl21 since 1985 which is consistent with increased lead production in this area and indicates an increase in mine derived lead pollution in the local environment over the past 30 years

warmer or cooler late holocene marine palaeoenvironments interpreting southeast australian and brazilian sea level changes using fixed biological indicators and their δ18o composition abstract relic inter tidal assemblages of sessile organisms which are referred to as fixed biological indicators fbis are shown to be useful proxies for late holocene climatic and environmental changes as well as direct indicators of short term fluctuations in sea level a detailed comparison of change in the inter tidal assemblages of two southern hemisphere sites at comparable latitudes port hacking new south wales south east australia and the laguna imbituba region of southern brazil indicates periods of marked similarities in the timing and nature of changes at 5200 3800 cal years bp and differences after 2400 cal years bp there is sufficient concurrence of cooling phases and falling sea levels to strongly suggest that in some cases global rather than regional forcing factors are at work the value of inter tidal organisms as indicators of changed environments is developed by identifying the past and present distributions of the common marker species tubeworms barnacles and mussels the 18 o content of these extant specimens at port hacking confirmed changes in ocean water temperature and associated sea level behaviour corresponding to invasion or extinction of temperature sensitive species a similar pattern is repeated although in a less marked fashion in the laguna imbituba region of southern brazil

shelf break upwelling driven by brazil current cyclonic meanders analysis of hydrographic data and results of numerical modeling show the occurrence of upwelling associated with the cyclonic meanders of the brazil current in the region known as the southeast brazil bight or santos bight the temperature and salinity distributions collected during summer and winter confirm the idea that meander induced shelf break upwelling plays an important role in the pumping of south atlantic central water from the slope region onto the continental shelf

high precision and high resolution carbonate 230th dating by mc icp ms with sem protocols abstract to facilitate the measurement of u th isotopic compositions suitable for high precision and high resolution 230th dating of coral and speleothem carbonates secondary electron multiplier sem protocol techniques for multicollector inductively coupled plasma mass spectrometry mc icp ms have been developed the instrumental sensitivities are 1 2 with a precision of 1 2 2 for abundance determination of 50 200 fg 234u 1 4 ng 238u or 230th this method features chemistry refinements improvements to procedural and instrumental blanks spectral inference reductions and careful consideration of non linear sem behavior measurement consistency of this mc icp ms combined with previous mass spectrometric results on u th standards and a variety of carbonates demonstrates the validity of the sem protocol method for fossil corals a routine u th isotopic determination at permil level precision requires only 10 50 mg of carbonate as little as 200 mg of young coral with an age of less than 20 yr can be dated with a precision of 0 3 0 8 yr about 20 200 mg speleothem samples with sub ppm to ppm u are required to earn a 5 precision on ages from 5 to 100 kyr requirement of small sample size 10 100s mg carbonate can permit high temporal resolution to date speleothems with slow growth rates i e 1 10 mm kyr this high precision 230th chronology is critical to accurately establish age models date events and splice geochemical proxy time series records from multiple samples in the fields of paleoclimatology and paleoceanography the u th isotopic determination techniques described here can also be applied to different environmental samples such as waters rocks and sediments

challenges and perspectives for large scale temperature reconstructions of the past two millennia knowledge of the temperature variability during the last one to two millennia is important for providing a perspective to present day climate excursions for assessing the sensitivity of the climate to different forcings and for providing a test bed for climate models since systematic instrumental temperature records only extend back to the nineteenth century such knowledge mainly relies on climate sensitive proxy data here we critically assess some of the many challenges related to large scale multiproxy temperature reconstructions we begin with a review of available large scale temperature reconstructions focusing on the differences in low frequency variability and the response to natural forcings such as major volcanic eruptions and changes in total solar irradiance then we discuss different proxy selection strategies review previously used reconstruction methods and discuss their ability to reconstruct the amplitude of the low frequency variability to shed additional light on the challenges of large scale reconstructions we investigate the spatial and temporal correlation structures in the observed temperature field and discuss the implications of these correlation structures regarding the required number and positions of proxies we demonstrate how the unavoidable uncertainty related to noisy proxies will show up as bias and variance in the reconstruction and that the partition between these forms of errors depends on the reconstruction method pseudo proxy experiments are conducted to further discuss the influence of noise and the requirements regarding the geographical location and number of proxies necessary for reliably reconstructing the low frequency variability we conclude with recommendations for future large scale temperature reconstructions

the anelasticity of the mantle the attenuation of seismic waves provides the most direct data regarding the non elastic properties of the earth recent experimental results from body waves surface waves and free oscillations provide estimates of the anelasticity in various regions of the earth results to date show that the upper mantle is more attenuating than the lower mantle the maximum attenuation is in the vicinity of the low velocity zone a rapid increase in attenuation occurs in the vicinity of the c region of the mantle and compressional waves are less attenuated than shear waves a frequency dependence of q has not yet been discovered most laboratory measurements of attenuation have been performed at ultrasonic frequencies on pure specimens of metals glasses plastics and ceramics a general feature of laboratory measurements is an exponential increase of attenuation with temperature on which are superimposed peaks which can be attributed to dislocation or other defect phenomena measurements on natural rocks at atmospheric pressure can be attributed to the presence of cracks the intrinsic attenuation of rocks as a function of temperature and pressure is not known however on other materials grain boundary phenomena dominate at high temperature this can be attributed to increased grain boundary mobility at high temperatures high pressure would be expected to decrease this mobility if attenuation in the mantle is due to an activated process it is probably controlled by the diffusion rate of defects at grain boundaries estimates of attenuation in the lower mantle then yield an estimate of the activation volume of the defects contributing to the loss if the lower mantle is assumed homogeneous the estimated activation volume is a small fraction of the presumed molal volume of materials making up the lower mantle stress induced migration of small point defects is a possible loss mechanism consistent with the observations

interannual variability of the sea surface temperature in the south brazil bight in the austral winter of 1993 during a coroas hydrographic cruise in the south brazil bight sbb an unexpected mass of cold and fresh water was observed on the continental shelf near 23 s subsequent analyses of different data sets suggested that the origin of that water was probably the argentine continental shelf near the rio de la plata mouth in this article a 13 year time series of avhrr sea surface temperature anomalies is analyzed to investigate the occurrence of this phenomenon in other periods the results of these analyses and a good correlation with the southern oscillation index suggest that the penetration of these waters into the sbb occurs in a frequency that may be associated with enso events

ice age terminations 230th dated oxygen isotope records of stalagmites from sanbao cave china characterize asian monsoon am precipitation through the ends of the third and fourthmost recent ice ages as a result am records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments establishing the timing and sequence of major events in all four cases observations are consistent with a classic northern hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets meltwater and icebergs entering the north atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon causing increases in atmospheric co2 and antarctic temperatures that drive the termination in the southern hemisphere increasing co2 and summer insolation drive recession of northern ice sheets with probable positive feedbacks between sea level and co2

summer monsoon precipitation variations in central china over the past 750 years derived from a high resolution absolute dated stalagmite abstract a 2 3 year resolution record of stalagmite oxygen isotope variations from the south flank of the qinling mountains central china has revealed the asian summer monsoon asm precipitation variations in the investigated area over the past 750 years the summer monsoon precipitation gradually increased since 1249 ad reaching its highest values in the period 1535 1685 ad and then decreased with substantial decadal to centennial scale fluctuations the monsoon precipitation increased again between 1920 and 1970 ad three intervals of high monsoon precipitation were identified 1535 1685 ad 1755 1835 ad and 1920 1970 ad three intervals of low precipitation were inferred in 1249 1325 ad 1390 1420 ad and 1890 1915 ad the 18 o composition and lithological features of the stalagmite coincidently indicate a wetter climate during the little ice age lia which is also confirmed by climate records from chinese historical documents within this area a comparison with other high resolution speleothem records indicates regional differences in monsoon precipitation variability from the south to the north of central china in the last 750 years on decadal to centennial scale power spectrum analysis of the 18 o record shows significant 117 8 34 6 14 10 3 and 6 year periodicities these periodicities are widely observed in the climate records from asm controlled areas of china and are consistent with the gleissburg periodicity br ckner periodicity sunspot periodicity of solar activity and el nino southern oscillation enso periodicity these correlations suggest that both solar activity and enso periodicity may have had important influences on asm precipitation in china over the past 750 years

seismic propagation across the east pacific rise finite difference experiments and implications for seismic tomography we use a full waveform acousto elastic finite difference technique to investigate seismic propagation across the east pacific rise at 9 30 n for a two dimensional velocity model based on that proposed by vera and others 1990 the primary feature of the model is an upper crustal low velocity region corresponding to the axial magma chamber which includes a small magma body located 1 6 km beneath the seafloor at the rise axis the high velocity gradients in this region result in a complex pattern of propagation which includes considerable scattering of energy above and below the magma chamber a qualitative comparison of finite difference seismograms with data collected by receivers located 9 km and 20 km off axis during a tomography experiment at 9 30 n shows generally good agreement for paths that cross the rise axis the first arrival in the finite difference solutions diffracts above the magma chamber this phase has a very low amplitude and at larger offsets falls below the ambient noise levels observed during the tomography experiment in such cases the first arrival with significant energy is a diffraction from below the magma chamber a high amplitude moho turning pmp phase which results from the large velocity change across the moho beneath the rise axis is apparent in both the finite difference solutions and the observations ray theoretical calculations of the paths of the diffracted arrivals are very unstable and for the diffractions above the magma chamber no solution can be found with a single precision algorithm synthetic delay time inversions using an approximate ray tracing algorithm demonstrate the importance of ensuring that picked arrival times are assigned to paths that pass to the correct side of the magma body synthetic inversions of spectral estimates of t show that q 1 models are compromised not only if the ray paths are incorrect but also if t estimates include significant contributions from more than one phase deterministic scattering from the magma chamber may contribute noticeably to spectral estimates of t but the results of the finite difference experiments imply that high levels of attenuation observed for phases passing below the magma chamber are predominantly the result of intrinsic attenuation

extension of summer june august temperature records for northern inner mongolia 1715 2008 china using tree rings this paper presents a spatially and temporally improved reconstruction of mean summer june august temperature derived from tree ring width data of dahurian larch larix gmelinii rupr from the northern great xing an mountains northeast china three new chronologies were added to the original 2011 reconstruction and the reconstruction extended back to ad 1715 the reconstruction was generated using a simple linear regression method verified by independent meteorological data and accounts for 47 0 of the actual temperature variance during the common period 1957 2008 the reconstruction captures decadal and century scale regional temperature variability such as cold decades 1940s 1930s 1790s 1950s and 1850s warm decades 2000s 1870s 1750s 1980s and 1840s a cold half century ca 1750 1799 and a warm half century ca 1900 1949 it also reveals slightly higher frequency of cold years 20 4 than warm years 18 0 and a recent warming trend compared to the original 2011 reconstruction this reconstruction has lower inter annual temperature variability high explained variance and high representativeness of regional climate the reconstruction also correlates with the east asian monsoon and the pacific ocean signals and indicates the feasibility of using tree rings from high latitude northeast china to reconstruct summer temperature in permafrost forest environments

seismic attenuation structure of the east pacific rise near 9 30 n we describe a spectral technique to measure the apparent attenuation of compressional waveforms recorded during an active seismic tomography experiment centered at 9 32 n on the east pacific rise over 3500 estimates of t are obtained from 0 4 to 0 7 s long windows aligned with crustal p phases including diffractions above and below a midcrustal magma chamber and moho reflections which cross the rise axis at a range of lower crustal depths we apply a smoothest model inversion algorithm to the t measurements to derive images of apparent crustal q 1 both 20 km off axis and within a 16 16 km area centered on the rise crest the models resolve regions of high attenuation in the uppermost crust and in a low q zone which extends from midcrustal to lower crustal depths beneath the rise axis off axis q values in the upper 1 km average 35 50 while at depths greater than 2 3 km q is at least 500 1000 the high levels of attenuation in the uppermost crust probably result from the combined effect of factional fluid flow and scattering mechanisms within 1 3 km of the rise axis q increases markedly in the uppermost 1 km to about 65 if the increase in attenuation off axis is entirely due to the 300 m increase in the thickness of layer 2a extrusives required by seismic velocity measurements then q in layer 2a must be about 10 20 no measurements of q are obtained in the immediate vicinity of the 1 6 km deep axial magma lens because no wave paths cross the rise axis through this region the diffractions beneath the magma chamber and the moho reflections require a low q region with minimum q values of 20 50 which extends from no more than 2 5 km depth to the base of the crust these values are similar to laboratory measurements of q obtained at solidus temperatures and constrain the low q region to contain no more than a few percent melt the axial magma chamber which comprises a melt lens and an underlying crystal mush zone must be confined to a narrow 1 km thick region through which no rise crossing paths pass inversions for along axis structure in the low q anomaly show a 20 25 increase in attenuation at 2 3 km depth north of 9 34 n but resolve no such trend at 4 6 km depth the along axis variations may reflect the recent history of volcanic eruptions and hydrothermal cooling and do not require systematic along axis variations in magma supply

rapid racemization of aspartic acid in mollusc shells and potential for dating over recent centuries dating of deposits and materials less than 350 years old is hindered by the very poor time resolution of the radiocarbon method over this period1 2 fluctuations in atmospheric 14c levels result in the existence of several possible calendric ages for any given radiocarbon age for terrestrial samples in the marine record these fluctuations are dampened however only a small change in marine radiocarbon ages occurs over this period from ad 1700 to 1950 radiocarbon ages become only 100 yr younger2 consequently age resolution is poor furthermore there is an uncertainty in the amount of the correction for the reservoir effect the apparent radiocarbon age of modern marine carbon typically 400yr which reflects the average residence time of carbon in the oceans amino acid racemization epimerization analysis has been used primarily for dating samples older than the limit of radiocarbon dating 40 000 50 000 yr bp 3 4 here i show that aspartic acid asp in mollusc shells has racemized particularly rapidly over the past few centuries analyses done on land snails from deposits in the negev desert eolianites in madeira cave deposits in jamaica and from museum collections indicate racemization rates of 2 5 per century asp racemization thus provides a means of dating recent faunal assemblages of molluscs and other biogenic carbonates as well as recent terrestrial fluvial and marine sedimentary sequences that contain molluscs

reduced seasonality of holocene climate and pervasive mixing of holocene marine section northeastern gulf of mexico shelf the large porcelaneous foraminifers cyclorbiculina compressa parasorites orbitolitoides and peneroplis proteus are conspicuous in death assemblages from holocene marine sediments of the alabama and florida panhandle shelf the species inhabited the northeastern gulf of mexico in the holocene ca 6 4 1 9 ka but do not live in the region today these foraminifers require warm clear waters and thus are important paleoclimatic and paleoenvironmental indicators they apparently were derived from sublittoral seagrass habitats and indicate reduced seasonality in the region during the middle to late holocene in addition a mixed foraminiferal fauna a hydrodynamically reworked macrofaunal assemblage and stratigraphic disorder in foraminiferal 14 c dates indicate extensive reworking of the entire holocene marine transgressive package evidence that mollusks are indigenous but large foraminifers are transported supports the generalization that out of habitat transport of macrofauna is negligible in most marine settings

sediment mixing and stratigraphic disorder revealed by the age structure of tellina shells in great barrier reef sediment radiocarbon calibrated amino acid racemization ages of 250 individually dated tellina shells from two sediment cores are used to quantify molluscan time averaging with increasing burial depth in the shallow water carbonate lagoon of rib reef central great barrier reef australia the top 20 cm of sediment contain a distinct essentially modern assemblage with a median age of only 5 yr sediment between 20 and 125 cm are age homogeneous and significantly older than the surface sediment median age 189 yr shell age distributions within layers indicate that the top 125 cm of lagoonal sediment is thoroughly mixed on a subcentennial scale shell size is an important correlate of shell half life and an important determinant of the inferred age of sedimentary layers these results illustrate the importance of bioturbation in these environments indicate that age estimates in this depositional setting are sensitive to specimen choice and document a size dependent bias in death assemblage formation

amino acid racemization dating of marine shells a mound of possibilities shell middens are one of the most important and widespread indicators for human exploitation of marine resources and occupation of coastal environments establishing an accurate and reliable chronology for these deposits has fundamental implications for understanding the patterns of human evolution and dispersal this paper explores the potential application of a new methodology of amino acid racemization aar dating of shell middens and describes a simple protocol to test the suitability of different molluscan species this protocol provides a preliminary test for the presence of an intracrystalline fraction of proteins by bleaching experiments and subsequent heating at high temperature checking the closed system behaviour of this fraction during diagenesis only species which pass both tests can be considered suitable for further studies to obtain reliable age information this amino acid geochronological technique is also applied to midden deposits at two latitudinal extremes northern scotland and the southern red sea results obtained in this study indicate that the application of this new method of aar dating of shells has the potential to aid the geochronological investigation of shell mounds in different areas of the world

crosshole seismology and seismic imaging in crystalline rocks a borehole to borehole audiofrequency seismic system using piezoelectric transducers as active elements has been developed and used to investigate crystalline rocks in canada high quality seismograms have been recorded for transmitter receiver distances of up to 230 meters it has been found that both travel times and signal amplitudes provide diagnostic information about rock quality two dimensional images of seismic velocity and transparency distributions between two boreholes derived from observed arrival times and amplitudes by simple back projection tomography reflect lithology and geological structure the results indicate the potential usefulness of crosshole seismic imaging as a tool for rock mass characterization

high resolution record of paleoclimate since the little ice age from the tibetan ice cores climate changes during the little ice age were studied based on oxygen isotope values 18o measured from ice cores recovered on and nearby the qinghai tibetan plateau three cold periods have been identified and are supported by three widely existing moraine ridges formed during the little ice age importantly the amplitude of the three cold periods differ in the cores studied in the dunde ice core the coldest period occurred in the 17th century while it occurred in the 19th century in the guliya ice core all the ice cores recovered from the tibetan plateau and nearby regions show strong climatic warming in the 20th century

three dimensional vp vs variations for the coso region california recent seismological studies of the coso region of southeastern california document both low p wave velocities and abnormal sv attenuation in indian wells valley south of the pleistocene volcanics of the coso range in order to learn more about the physical nature of these colocated anomalies a tomographic inversion for the three dimensional variations of vp vs the ratio of compressional to shear velocity was performed iterative back projection of 2966 shear and compressional wave travel time residuals from local earthquakes recorded on vertical instruments reveals that vp vs is generally high at the surface and decreases systematically to 10 km depth superimposed on this trend are several large anomalies near devil s kitchen in the coso geothermal area vp vs values are very low near the surface consistent with measured values for steam dominated geothermal systems abnormally high values of vp vs are observed in portions of indian wells valley and also below the cactus peak rhyolite dome from 2 to 5 km in depth in indian wells valley the co occurrence of low p velocities low s velocities high vp vs and anomalous sv attenuation are indicative of subsurface partial melt because the inversion is based on vertical data only however the results cannot be considered conclusive only suggestive

reconstruction of the northeast asian monsoon climate history for the past 400 years based on textural carbon and oxygen isotope record of a stalagmite from yongcheon lava tube cave jeju island korea abstract paleoclimatic changes over the past 400 years were investigated based on textural and geochemical characteristics of the yc 2 stalagmite which grew in yongcheon cave lava tube cave on jeju island korea the stalagmite is about 68 mm long and annual growth laminae are distinctively identified the age of the stalagmite was mainly determined by counting annual growth laminae supplemented by other radiometric dating methods and it is estimated that the stalagmite grew at least for ca 242 years including the hiatus this hiatus is located at about 15 mm from the base and is present in the form of one thick brown growth lamina which was formed when the stalagmite stopped to grow texturally the stalagmite can be divided into two phases fluid inclusion poor compact columnar calcite phase a and fluid inclusion rich sparse columnar calcite phase b this textural division is intimately related to the spacing of growth laminae that is phase a is characterized by narrower spacing of growth laminae phase a with narrow spaced growth laminae indicates the slower growth rate due to lower amount of rainfall when northeast asian summer monsoon intensity was relatively lower based on high resolution carbon isotope trend the stalagmite can be divided into three stages stages i ii and iii the relatively more positive carbon isotopic compositions of the stage i 13 c 3 3 0 4 pdb in the lower part indicate that it grew during the little ice age lia under cold and dry climate with less vegetation the stage ii is a transitional period from cold and dry to warm and wet climate with a continuous decrease in carbon isotope values from 0 6 to 9 6 in 13 c this stage shows the gradual weakening of the lia climate carbon isotope trend also suggests that the lia interval was terminated near middle 1870 s around korean peninsula relatively low carbon isotopic compositions during stage iii 13 c 11 0 8 0 in the upper part should indicate that climate was changed to the warm and wet current warm period warming since 1960 can also be recognized complete coincidence between textural data internal calcite texture and growth laminae spacing and high resolution carbon isotope compositions strongly suggests that past climate changes such as monsoonal variations in northeast asia have been clearly recorded in the stalagmite in yongcheon cave

azimuth energy q and temperature variations on p wave amplitudes in the united states mean relative p wave 1 s amplitude characteristics are determined for standardized seismic stations in the united states data are compiled from three azimuths to the north explosions in russia to the northwest earthquakes along the asian pacific arc and to the south southeast earthquakes in south america characteristic receiver amplitudes are found to be azimuthally dependent high amplitude areas occur in the central united states and lowest amplitudes occur along the rocky mountain front range and the rio grande rift zone amplification effects of low velocity sediments are significant in the central united states azimuthal amplitude variations in the eastern united states are consistent with an anomalous attenuating or defocusing body in the lower mantle beneath colombia south america nonazimuthal amplitude studies are tied to the azimuthal data set to increase station amplitude coverage the regional and local stability of amplitudes is analyzed amplitudes are stable with an average variation of a factor of about 1 3 around the regional mean for seismic stations situated on hard bedrock the squared amplitude variations are related to energy variations in the p wave fronts acknowledging the likely importance of elastic focusing defocusing and scattering effects at individual stations variations of anelastic attenuation are derived that are consistent with the observed energy amplitude variations assuming that the variations of anelastic attenuation occur in the upper 400 km of the earth high amplitude stations may be unattenuated low amplitude stations are consistent with q 110 and a mean amplitude implies q 220 240 the range of variation of q is mapped into temperature variations assuming a thermally activated q mechanism and an olivine activation energy for the upper mantle the apparent q variations are consistent with temperature variations of 135 287 c between high and low amplitude seismic station sites geophysical and physiographic correlations with the p wave amplitude variations are discussed accounting for the motion of the north american plate low p wave amplitudes along the rocky mountain front may be related to the uplift of the colorado plateau low amplitudes extending from northern texas to new england lie along the approximate boundary of the continental craton

reworking and discontinuities in holocene sedimentation in the nile delta documentation from amino acid racemization and stable isotopes in mollusk shells abstract the late holocene sedimentary history of the northwestern edge of the nile delta is reconstructed from amino acid racemization radiocarbon and stable isotope analysis of a series of bivalve shells from a core taken at the edge of lake maryut near alexandria amino acid racemization confirmed by radiocarbon and stable isotope analysis indicates that in many parts of the core mixed age mollusk assemblages are present dating of the time of sediment accumulation at various levels in the core is therefore based on the age of the youngest shells which are identified by amino acid racemization analysis lowest d l values ams radiocarbon analysis is used to determine the ages of the shells except for the most recent sediments last 100 yr for which aspartic acid racemization provides more precise ages amino acid racemization analysis of 59 shells from 21 levels in the 4 8 m holocene sequence in the core enabled identification of a large hiatus holocene sedimentation started at ca 2400 bc apparently corresponding to a westward shift of the course of the canopic nile distributary which lies to the east deposition continued at a rate of 1 4 mm per year ceasing at ca 550 bc at which time the canopic nile shifted eastward again and subsequently became defunct a marine connection during this period is indicated by stable isotope values of shells sediment accumulation began again only at the end of the 19th century when a series of irrigation canals was connected to the lake maryut basin stable isotope values indicate a strong freshwater influence deposition has continued to the present at a very high rate 19 mm per year due to supply of sediments by agricultural activity the relative ease with which racemization analyses can be carried out permits detailed analysis of core chronostratigraphy leading to more accurate reconstruction of core chronology hiatuses can be pinpointed and documented and age mixtures can be identified with appropriate individual shells being selected for ams radiocarbon analysis aspartic acid racemization analysis permits dating of samples from the last several hundred years a period for which radiocarbon analyses provide poor precision

the seismic attenuation structure of a fast spreading mid ocean ridge the two dimensional p wave attenuation structure of the axial crust of the east pacific rise was obtained from an inversion of waveform spectra collected during an active source seismic tomography experiment the structure shows that attenuation near the surface is high everywhere but decreases markedly within 1 to 3 kilometers of the rise axis the near axis variation is attributed to the thickening of the surface basalt layer and possibly to in situ changes in porosity related to hydrothermal circulation high attenuation is also observed beneath the rise axis at depths ranging from about 2 kilometers less than 1 kilometer beneath the axial magma lens to the base of the crust the levels of attenuation in this deeper region require at most only a small fraction of partial melt

centennial to decadal scale monsoon precipitation variations in the upper hanjiang river region china over the past 6650 years abstract the upper hanjiang river region is the recharge area of the middle route of south to north water transfer project the region is under construction of the hanjiang weihe river water transfer project in china monsoon precipitation variations in this region are critical to water resource and security of china in this study high resolution monsoon precipitation variations were reconstructed in the upper hanjiang river region over the past 6650 years from 18 o and 13 c records of four stalagmites in xianglong cave the long term increasing trend of stalagmite 18 o record since the middle holocene is consistent with other speleothem records from monsoonal china this trend follows the gradually decreasing northern hemisphere summer insolation which indicates that solar insolation may control the orbital scale east asian summer monsoon easm variations despite the declined easm intensity since the middle holocene local precipitation may not have decreased remarkably as revealed by the 13 c records a series of centennial to decadal scale cyclicity was observed with quasi millennium quasi century 57 36 and 22 year cycles by removing the long term trend of stalagmite 18 o record increased monsoon precipitation during periods of 4390 3800 a bp 3590 2960 a bp 2050 1670 a bp and 1110 790 a bp had caused four super floods in the upper reach of hanjiang river dramatically dry climate existed in this region during the 5 0 ka and 2 8 ka events coinciding with notable droughts in other regions of monsoonal china remarkably intensified and southward westerly jet together with weakened summer monsoon may delay the onset of rainy seasons resulting in synchronous decreasing of monsoon precipitation in china during the two events during the 4 2 ka event and the little ice age the upper hanjiang river region was wet which was similar to the climate conditions in central and southern china but was the opposite of drought observed in northern china we propose that weakened summer monsoon and less strengthened or normal westerly jet may cause rain belt stay longer in the southward region which reduced rainfall in northern china but enhanced it in central and southern china

p wave velocity variations in the coso region california derived from local earthquake travel times inversion of 4036 p wave travel time residuals from 429 local earthquakes using a tomographic scheme provides information about three dimensional upper crustal velocity variations in the indian wells valley coso region of southeastern california the residuals are calculated relative to a coso specific velocity model corrected for station elevation weighted and back projected along their ray paths through models defined with layers of blocks slowness variations in the surface layer reflect local geology including slow velocities for the sedimentary basins of indian wells and rose valleys and relatively fast velocities for the sierra nevada and argus mountains in the depth range of 3 5 km the inversion images an area of reduced compressional velocity in western and northern indian wells valley but finds no major velocity variations beneath the coso volcanic field to the north these results are consistent with a recent study of anomalous shear wave attenuation in the coso region between 5 and 10 km depth low velocity areas 7 slow appear at the southern end of the coso volcanics reaching east to the coso basin numerical tests of the inversion s resolution and sensitivity to noise indicate that these major anomalies are significant and well resolved while other apparent velocity variations in poorly sampled areas are probably artifacts the seismic data alone are not sufficient to uniquely characterize the physical state of these low velocity regions because of the coso region s history of pleistocene bimodal volcanism high heat flow geothermal activity geodetic deformation and seismic activity one possibility is to link the zones of decreased p velocity to contemporary magmatic activity

aspartic acid racemization dating of holocene brachiopods and bivalves from the southern brazilian shelf south atlantic abstract the extent of racemization of aspartic acid asp has been used to estimate the ages of 9 shells of the epifaunal calcitic brachiopod bouchardia rosea and 9 shells of the infaunal aragonitic bivalve semele casali both taxa were collected concurrently from the same sites at depths of 10 m and 30 m off the coast of brazil asp d l values show an excellent correlation with radiocarbon age at both sites and for both taxa r2site 9 b rosea 0 97 r2site 1 b rosea 0 997 r2site 9 s casali 0 9998 r2site 1 s casali 0 93 the asp ratios plotted against reservoir corrected ams radiocarbon ages over the time span of multiple millennia can thus be used to develop reliable and precise geochronologies not only for aragonitic mollusks widely used for dating previously but also for calcitic brachiopods at each collection site bouchardia specimens display consistently higher d l values than specimens of semele thermal differences between sites are also notable and in agreement with theoretical expectations as extents of racemization for both taxa are greater at the warmer shallower site than at the cooler deeper one in late holocene marine settings concurrent time series of aragonitic and calcitic shells can be assembled using asp racemization dating and parallel multi centennial to multi millennial records can be developed simultaneously for multiple biomineral systems

a 53 year seasonally resolved oxygen and carbon isotope record from a modern gibraltar speleothem reconstructed drip water and relationship to local precipitation abstract the response of a climate proxy against measured temperature rainfall and atmospheric circulation patterns at sub annual resolution is the ultimate test of proxy fidelity but very few data exist showing the level of correspondence between speleothem climate proxies and the instrumental climate record cave sites on the gibraltar peninsula provide a unique opportunity to calibrate speleothem climate proxies with the longest known available precipitation isotopes and instrumental records an actively growing speleothem sampled from new st michaels cave in 2004 is composed of paired laminae consisting of light columnar calcite and a darker microsparitic calcite stable isotope analysis of samples micromilled in 100 m steps at the equivalent of bi monthly intervals reveals fabric correlated annual cycles in carbon isotopes oxygen isotopes and trace elements responding to seasonal changes in cave microclimate hydrology and ventilation patterns calcite 13 c values reach a minimum in the light columnar fabric and evidence from trace element behaviour and cave monitoring indicates that this grows under cave winter conditions of highest p co 2 whereas the dark microsparitic calcite characterised by elevated 13 c and 18 o values grows under low summer p co 2 conditions drip water 13 c dic reaches a minimum in march april at which time the attenuated 18 o signal becomes most representative of winter precipitation an age model based on cycle counting and the position of the 14 c bomb carbon spike yields a precisely dated winter oxygen isotope proxy of cave seepage water for comparison with the gnip and instrumental climate record for gibraltar the 18 o characteristics of calcite deposited from drip water representing winter precipitation for each year can be derived from the seasonally resolved record and allows reconstruction of the 18 o drip water representing winter precipitation for each year from 1951 2004 these data show an encouraging level of correspondence r 2 0 47 with the 18 o of rainfall falling each year between october and march and on a decadal scale the 18 o of reconstructed winter drip water mirrors secular change in mean winter temperatures

pervasive autocorrelation of the chemical index of alteration in sedimentary profiles and its palaeoenvironmental implications the chemical index of alteration has been used widely for reconstruction of the palaeoclimate however the mechanisms and environmental factors controlling the chemical index of alteration of sediments are not yet fully understood in this study autocorrelations of the chemical index of alteration in nine sedimentary profiles from both the land and the sea spanning different geological times are discussed the sediments of these profiles have different origins dust fluvial or ocean sediments and are from various climate situations and sedimentary environments autocorrelations of chemical index of alteration series are ubiquitously evident in all profiles it is suggested here that autocorrelations may be caused by post depositional changes such as persistent weathering and diagenesis as a result the chemical index of alteration may not reflect climatic conditions during the time of sediment deposition this study strongly recommends the confirmation of the reliability and veracity of the chemical index of alteration before it is adopted to evaluate the weathering degree of parent rocks and to reconstruct the past climate significant autocorrelations in loess profiles were specifically observed suggesting that the existing understanding of loess deposition in terms of climate conditions requires re examination and that previous reconstructions of rapid climate changes for example in centennial millennial scales should be treated with caution

palaeo climate reconstruction from stable isotope variations in speleothems a review abstract speleothems are now regarded as valuable archives of climatic conditions on the continents offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores they are ideal materials for precise u series dating yielding ages in calendar years thereby circumventing the radiocarbon calibration problems associated with most other continental records stable isotope studies in speleothems have shifted away from attempting to provide palaeo temperature reconstructions to the attainable goal of providing precise estimates for the timing and duration of major o isotope defined climatic events characterised by high signal to noise ratios e g glacial interglacial transitions dansgaard oeschger oscillations the 8200 year event unlike the marine records speleothem data sets are not tuned and their independent chronology offers opportunities to critically assess leads and lags in the climate system that in turn can provide important insights into forcing and feedback mechanisms improved procedures for the extraction and measurement of stable isotope ratios in fluid inclusions trapped in speleothems are likely to provide in the near future a much enhanced basis for the quantitative interpretation of o isotope ratios in speleothem calcite the latter developments open up once again the tantalising prospect of palaeo temperature estimates but more importantly perhaps provide a direct test for a new generation of general circulation models whose hydrological cycles will incorporate the water isotopes the literature is reviewed briefly to provide for the reader a sense of the current state of the art and to provide some pointers for future research directions

climate significance of speleothem δ18o from central china on decadal timescale abstract speleothem based oxygen isotopic sequences have been widely used to reveal regional climatic changes worldwide however the climatic significance of speleothem 18o variations in monsoonal china on decadal to annual timescales remains in debate which limits its application to paleoclimate reconstruction in the world s largest country by population in this study we analyzed a seasonally resolved 18o record of an annually layered stalagmite xl21 whose variability covers a period of 98 years 1912 2009 ad from xianglong cave central china the annual 18o trend shows an inverse relationship with local monsoon precipitation suggesting speleothem 18o variations in this area can reflect monsoon precipitation at least on decadal timescale changes in moisture sources and transport pathways have little effect on the 18o variations in speleothems monsoon precipitation on decadal timescale which may be ascribed to similar distances from this region to the two main moisture sources the bay of bengal and west pacific there is an anti phase relationship between speleothem 18o records from central china and india during the last 98 years which indicates the relationship between indian monsoon intensity and speleothem 18o from central china on short timescales requires further investigation

a continuous multi millennial record of surficial bivalve mollusk shells from the sao paulo bight brazilian shelf abstract to evaluate the potential of using surficial shell accumulations for paleoenvironmental studies an extensive time series of individually dated specimens of the marine infaunal bivalve mollusk semele casali was assembled using amino acid racemization aar ratios n 270 calibrated against radiocarbon ages n 32 the shells were collected from surface sediments at multiple sites across a sediment starved shelf in the shallow sub tropical sao paulo bight sao paulo state brazil the resulting 14 c calibrated aar time series one of the largest aar datasets compiled to date ranges from modern to 10 307 cal yr bp is right skewed and represents a remarkably complete time series the completeness of the holocene record is 66 at 250 yr binning resolution and 81 at 500 yr binning resolution extensive time averaging is observed for all sites across the sampled bathymetric range indicating long water depth invariant survival of carbonate shells at the sediment surface with low net sedimentation rates benthic organisms collected from active depositional surfaces can provide multi millennial time series of biomineral records and serve as a source of geochemical proxy data for reconstructing environmental and climatic trends throughout the holocene at centennial resolution surface sediments can contain time rich shell accumulations that record the entire holocene not just the present

well traveled cockles shell transport during the holocene transgression of the southern north sea radiocarbon dates from 34 shells of the intertidal bivalve cerastoderma edule demonstrate that shells were transported in both landward and seaward directions during the holocene transgression of the southern north sea old shells on the beaches of the east frisian islands of germany document landward transport and young shells in the german bight and dogger bank document seaward transport the area9s sea level curve and the shell ages were used to predict the original depth of each specimen the difference between a specimen9s predicted age and its present depth is a measure of depth displacement depth displacements ranged from 35 to 37 m eight shells remained within 2 5 m of their original depth and roughly equal proportions of the rest moved landward and seaward specimens transported into deeper water are a very small fraction of the shells at that depth whereas specimens transported into shallow water occur alongside abundant indigenous individuals of the same species rare fossils should not be used to estimate paleodepths

anomalous shear wave attenuation in the shallow crust beneath the coso volcanic region california we use seismograms of local earthquakes to image relative shear wave attenuation structure in the shallow crust beneath the region containing the coso volcanic geothermal area of eastern california sv and p wave amplitudes were measured from vertical component seismograms of earthquakes that occurred in the cososouthem sierra nevada region from july 1983 to august 1985 seismograms of 16 small earthquakes show sv amplitudes which are greatly diminished at some azimuths and takeoff angles indicating strong lateral variations in s wave attenuation in the area three dimensional images of the relative s wave attenuation structure are obtained from forward modeling and a back projection inversion of the amplitude data the results indicate regions within a 20 by 30 by 10 km volume of the shallow crust one shallower than 5 km that severely attenuate sv waves passing through them these anomalies lie beneath the indian wells valley 30 km south of the coso volcanic field and are coincident with the epicentral locations of recent earthquake swarms no anomalous attenuation is seen beneath the coso volcanic field above about 5 km depth geologic relations and the coincidence of anomalously slow p wave velocities suggest that the attenuation anomalies may be related to magmatism along the eastern sierra front

applications of stalagmite laminae to paleoclimate reconstructions comparison with dendrochronology climatology abstract laminated stalagmites observed in either ultra violet or visible light or recognized via trace elements are now widely recognized as a common deposition form annually laminated stalagmites should be expected in caves which have an overlying climate that has a strong seasonality similar climate zones to where trees grow with distinct annual rings continuous laminated stalagmite chronologies up to several thousand years should be expected where some mixing of stored water occurs such stalagmites can be used to reconstruct climate particularly through variations in lamina width such climate records would be relatively damped by mixing of event water with stored groundwater constraining the amount of high frequency climate signals contained in the stalagmite but relatively long continuous lamina sequences permit the preservation of low frequency centennial scale climate signals this contrasts with numerous tree ring climate records which are frequently limited in preserving multi centennial trends due to the necessary removal of age related noise from relatively short tree segments laminated stalagmites and tree rings should therefore to some degree provide complementary climate information appropriate methods for compiling stalagmite layer chronologies and climatologies are presented

relative sea level changes in the last 5500 years in southern brazil laguna imbituba region santa catarina state based on vermetid ages abstract twenty six new radiocarbon dates from vermetid shells collected in the southernmost sector of the brazilian rocky coast presented dates ranging from 5410 80 to 190 65 years b p with associated paleosea levels varying from 2 10 m to 0 20 m above present sea level the overall suggested trend of the relative sea level rsl declining until at least 190 years b p is somewhat contradictory to a proposed rsl rise in the last 1000 years in southern brazil the data also seem to undermine a more widely accepted rsl trend that suggests that at least two negative rsl oscillations occurred between 4100 and 3800 years b p and between 3000 and 2700 years b p the maximum elevation of the rsl in the holocene in southern brazil was possibly lower than that observed in most of the brazilian eastern coast discrepancies between ancient sea levels of similar ages are attributed to coincidental methodological problems to imprecisions in determining past relative sea levels and to possible changes in the geomorphology and wave climate close to shore during the last 5000 years a general trend of increasing 18 o with a reduction in age in the studied samples may suggest a gradual reduction of water temperature in the region during the same period

quantitative temperature reconstruction based on growth rate of annually layered stalagmite a case study from central china we used the annual growth rate of a stalagmite xl21 collected from xianglong cave central china to quantitatively reconstruct regional terrestrial temperature changes over the last 95 years 1912 2006 ad based on a significant positive correlation between the growth rate and the observed temperature a transfer function was designed and the temperature from the previous september to may p9 5 was reconstructed with an explained variance of 43 5 our results show an increasing trend in temperature during the last century and especially over the last 30 years the temperature variability from central china recorded here bears a striking similarity to that in the northern hemisphere and also to global trends however the cooling between the 1980s and the early 1990s seen in the stalagmite record which interrupted the warming trend that began in the 1960s is not observed in the mean conditions found in china the northern hemisphere neither globally this methodology for reconstructing historical temperature from stalagmite growth rates overcomes the limitation of the short meteorological observation period and supports the potential of stalagmite lamina climatology

the global attenuation structure of the upper mantle 1 a large data set of fundamental mode rayleigh wave amplitudes is analyzed to derive a new global three dimensional model of shear wave attenuation in the upper mantle the amplitude observations span a range of periods between 50 and 250 s and are derived from earthquakes with mw 6 0 that occurred between 1993 and 2005 four separate factors may influence an amplitude anomaly intrinsic attenuation along the raypath elastic focusing effects along the raypath uncertainties in the strength of excitation and uncertainties in the response at the station in an earlier paper dalton and ekstrom 2006a dependence of the retrieved attenuation structure on these terms was shown to be significant and an approach was developed to invert the amplitudes simultaneously for each term the new three dimensional attenuation model qrfsi12 which is the subject of this paper is derived using this method the model contains large lateral variations in upper mantle attenuation 60 to 100 and exhibits strong agreement with surface tectonic features at depths shallower than 200 km at greater depth qrfsi12 is dominated by high attenuation in the southeastern pacific and eastern africa and low attenuation along many subduction zones in the western pacific resolution tests confirm that the change in pattern of attenuation above and below 200 km depth can be determined with confidence using the fundamental mode data set the new model is highly correlated with global models of shear wave velocity particularly in the uppermost mantle suggesting that the same factors may control both seismic attenuation and velocity in this depth range however forcing the lateral perturbations in attenuation to match those found in global velocity models decreases the data variance reduction which suggests that subtle differences between patterns of attenuation and velocity are robust

stratigraphy and holocene evolution of a regressive barrier in south brazil abstract the paranagua coastal plain is a 600 km 2 barrier system located in south brazil 25 30 s and is largely made up of pleistocene and holocene beach ridges sea level history in the area is characterized by a gradual 3 5 m sea level fall in the last 5000 years several reverse circulation drill logs from the pleistocene and holocene sectors allowed for the definition of a general morphostratigraphic model of the coastal plain which proposes the staking of at least two generations of marine deposits upon continental and paleo estuarine sediments analysis of shallow vibro cores and exposures along back barrier creeks indicates the existence of four transgressive estuarine estuarine channel overwash and flood tidal delta and three regressive beachface nearshore and upper shoreface sedimentary facies in the holocene section of the coastal plain the morphostratigraphy suggests that barrier emplacement took place at the last stages of the post glacial marine transgression when the back barrier estuary was squeezed in between the pleistocene and holocene barriers holocene barrier progradation was significant in both the shore normal and longshore direction and was apparently very swift in the last thousand years corresponding to a period when sea level fell by 1 5 m and when about half of the present barrier volume was accumulated higher progradation rates are ascribed to the arrival of sediment yielded by an active littoral drift system which appears to have eroded large extents of several holocene barriers along 100 km of coastline

paleoclimate reconstruction based on the timing of speleothem growth and oxygen and carbon isotope composition in a cave located in the rain shadow in israel high resolution th 230 u 234 ages and delta 18 o and delta 13 c compositions of speleothems in ma ale efrayirn cave located to the east of the central mountain ridge of israel enable us to examine the nature of the rain shadow aridity during glacial and interglacial intervals speleothem growth occurred during marine glacial isotopic periods with no growth during the two last marine isotope interglacial intervals and during the peak of the last glacial maximum this contrasts with speleothem growth in caves located on the western flank of the central mountain ridge in the eastern mediterranean semiarid climatic zone which continued throughout the last 240 000 yr thus during glacial periods water reached both sides of the central mountain ridge a comparison of the present day rain and cave water isotopic compositions and amounts at the ma ale efrayim cave site with those on the western flank shows that evaporation and higher temperatures on the eastern flank are major influences on isotopic composition and the lack of rainfall the delta 18 o and delta 13 c profiles of the speleothems deposited between 67 000 and 25 000 yr b p match the general trends of the isotopic profiles of soreq cave speleothems suggesting a similar source eastern mediterranean sea and similar climatic conditions thus during glacial periods the desert boundary effectively migrated further south or east from its present day location on the eastern flank whereas interglacial periods appear to have been similar to the present with the desert boundary at the same position the decrease in overall temperature and a consequent reduction in the evaporation to precipitation ratios on the eastern flank are viewed as the major factors controlling the decay of the rain shadow effect during glacial periods c 2003 elsevier science usa all rights reserved

mechanism of anelasticity summary to modem vector processors supercomputers now makes possible extremely large scale seismological computations in which the anelasticity of the earth can be treated in an exact manner for this exact formalism to be physically meaningful it must be shown to be consistent with a convincing physical model of anelasticity such a model is investigated for unsaturated solid earth materials it is a scattering mechanism which is based on the nature of polycrystalline aggregates for transverse waves this linear mechanism of anelasticity is given by

applications of attenuation tomography to imperial valley and coso indian wells region southern california spatial variations in seismic wave attenuation were tomographically imaged from observed s to p wave amplitude ratios in the imperial valley and coso indian wells regions of southern california in the coso indian wells region a highly attenuating body s wave quality factor q 30 coincides with a slow p wave anomaly mapped by walck and clayton 1987 this coincidence suggests the presence of a 3 to 5 km depth magmatic or hydrothermal body in the indian wells region in the imperial alley slow p wave travel time anomalies and highly attenuating s wave anomalies were found in the brawicy seismic zone at a depth of 8 12 kin the effective s wave quality factor is very low q 20 and the p wave velocity is 10 slower than the surrounding area these results suggest either magmatic or hydrothermal intrusions or fractures at depth possibly related to active shear in the brawley seismic zone this attenuation tomographic technique is shown to be useful in delineating the spatial variations in seismic wave attenuation and in estimating the effective seismic quality factor of attenuation anomalies

high frequency seismic attenuation of oceanic p and s waves in the western pacific analyses of oceanic p and s data from an earthquake in the kuril islands which occurred along the trend of a 1500 km long ocean bottom hydrophone array deployment near wake island have yielded constraints on high frequency seismic attenuation in the western pacific spatial attenuation and q were determined for group velocities between 8 2 and 3 0 km s and for frequencies between 2 5 and 22 5 hz there is greater attenuation of oceanic p than oceanic s at all frequencies suggesting either the presence of significant bulk attenuation in the lithosphere or that oceanic p propagates as a leaky mode the apparent attenuation of oceanic p and s is distance dependent with lower attenuation beyond 30 the apparent q of oceanic p increases with frequency as q 0 7 from about 300 at 2 5 hz to 1500 at 17 5 hz the apparent q of oceanic s increases with frequency as q 1 1 from about 400 at 2 5 hz to 3000 at 22 5 hz

quantifying the value of laminated stalagmites for paleoclimate reconstructions 1 from the permian through to the modern day stalagmites are an important archive of environmental change annually laminated stalagmites provide both a precise chronology and a paleoclimate proxy the rate of annual vertical growth of stalagmites is recorded in changes of calcite fabric annual fluxes of fluorescent organic matter or annual variations in trace element composition the processes governing stalagmite growth are the flux of water the co2 saturation of drip water relative to the cave atmosphere and the temperature although these processes are well understood they depend on the specific hydrogeological flow routing of individual stalagmites therefore although past climates are recorded in the vertical growth lamina thickness the climatic signal is perturbed by noise related to local hydrologic factors to separate local from global factors we used geostatistical tools to analyze annual growth rate data from eleven stalagmites located on four continents variogram analyses permit the quantification of the signal content contained within the growth rate records the information content ranges from 23 to 87 analysis of the growth derivative shows a negative correlation at a 1 year lag meaning that acceleration in growth rate tends to be systematically followed by deceleration in growth rate and vice versa we call this behavior flickering growth and argue that it is related to the size of the store feeding the stalagmite variogram analysis and flickering are used to screen which types of signals can potentially be recorded in a given speleothem

the brazilian sea level curves a critical review with emphasis on the curves from the paranaguaand cananeia regions abstract relative sea level curves for the mid to late holocene have been proposed for eight different sectors along the brazilian coast this paper aims to review the data used to construct the curves proposed for two sectors the paranaguaand cananeia regions in southeast brazil more specifically we analyze the palaeo sea level indicators vermetid tubes shells wood fragments and shell midden deposits related to 1 the sea level maximum of the mid holocene and 2 the two secondary oscillations that would have occurred between 4100 3800 years b p and 3000 2700 years b p the sedimentary deposits of the coastal plain as well as vermetid datings suggest a mid holocene sea level maximum between 3 5 and 4 m the great majority of the indicators used to infer the secondary oscillations in previous studies were derived from shell middens besides being unreliable palaeo sea level indicators these data also showed inconsistencies that undermine the existence of such oscillations the plot of all the data derived from vermetid samples found along the brazilian coast also indicate a rather smoother sea level fall in the last 5100 years

trade winds drive pronounced seasonality in carbonate chemistry in a tropical western pacific island cave implications for speleothem paleoclimatology carbon dioxide concentrations in caves are a primary driver of rates of carbonate dissolution and precipitation exerting strong control on speleothem growth rate and geochemistry long term cave monitoring studies in mid latitude caves have observed seasonal variability in cave pco2 whereby airflow is driven by temperature contrasts between the surface and subsurface in tropical settings where diurnal temperature cycles are larger than seasonal temperature cycles it is has been proposed caves will ventilate on daily timescales preventing cave pco2 from increasing substantially above atmospheric pco2 by contrast the relatively small temperature difference between the surface and subsurface may be insufficient to drive complete ventilation of tropical caves here we present results of an 8 year cave monitoring study including observations of cave pco2 and carbonate chemistry at jinapsan cave guam 13 4 n 144 5 e we find that cave pco2 in jinapsan cave is both relatively high and strongly seasonal with cave pco2 ranging from 500 5000 ppm the seasonality of cave pco2 cannot be explained by temperature contrasts instead we find evidence that seasonal trade winds drive cave ventilation and modulate cave pco2 calcite deposition rates at seven drip sites in jinapsan cave are shown to be seasonally variable demonstrating that speleothem growth rates in jinapsan cave are strongly affected by seasonal variations in cave pco2 these results highlight the importance that advection can have on cave ventilation processes and carbonate chemistry seasonality in carbonate chemistry and calcite deposition in this cave effect the interpretation of speleothem based paleoclimate records this article is protected by copyright all rights reserved

cave air control on dripwater geochemistry obir caves austria implications for speleothem deposition in dynamically ventilated caves there are very few process studies that demonstrate the annual variation in cave environments depositing speleothems accordingly we initiated a monitoring program at the obir caves an austrian dripstone cave system characterized by a seasonally changing air flow that results in a predictable pattern of high pco2 during summer and low pco2 in winter although similar seasonal changes in soil pco2 occur they are not directly connected with the changes in the subsurface since the dripwaters are fed from a well mixed source showing little seasonal variation cold season flushing by relatively co2 poor air enhances degassing of co2 in the cave and leads to a high degree of supersaturation of dripwater with regard to calcite forced calcite deposition during the cold season also gives rise to a pronounced pattern of synchronous seasonal variations in electrical conductivity alkalinity ph ca and 13cdic which parallel variations recorded in 13ccave air chemical components unaffected by calcite precipitation e g d 18o sio2 so4 lack a seasonal signal attesting to a long residence in the karst aquifer modeling shows that degassing of co2 from seepage waters results in kinetically enhanced c isotopic fractionation which contrasts with the equilibrium degassing shown from the soreq cave in israel the obir caves may serve as a case example of a dripstone cave whose seepage waters and speleothems show intra annual geochemical variability that is primarily due to chemical modification of the groundwater by a dynamic bidirectional subsurface air circulation

enhanced age resolution of the marine quaternary record in the arctic using aspartic acid racemization dating of bivalve shells abstract aspartic acid asp racemization occurs at a significantly higher rate than isoleucine epimerization and consequently provides better temporal resolution of arctic marine deposits from alaska spitsbergen and baffin island heating experiments at 100 c on the bivalvesmyaandhiatellashow the asp racemization rate decreases with increasing d l values as is typical for biogenic carbonates based on these experimental racemization rates and rates determined from racemization of samples radiocarbon dated to ca 10 000 12 000 yr b p activation energies formyaandhiatellaare estimated to be 30 6 and 30 0 kcal mol respectively for asp racemization and 29 0 and 29 5 for isoleucine epimerization analysis of a time series of plio pleistocenehiatellafrom the north coast of alaska shows that last interglacial mollusks can be readily distinguished from modern samples by asp but not by isoleucine d l asp values indicate a younger age for the fishcreekian transgression than does isoleucine epimerization for spitsbergen d l asp shows a slight age difference ca 12 000 yr between two units of the episode b interstadial and suggests that the age of these units may be closer to 65 000 than to 80 000 yr b p two possible ages suggested by other evidence the age of the loks land interstadial on baffin island is likely to be greater than that indicated by radiocarbon ages within deposits from each region d l asp values are less variable among individual shells than isoleucine epimerization values this may indicate better reliability of asp for geochronology

location and configuration of magma bodies beneath long valley california determined from anomalous earthquake signals recordings of 281 small earthquakes which occurred recently near the southern edge of long valley caldera at depths from 1 to 15 km are used to map the subsurface geometry of shear wave attenuating bodies in the caldera signatures of these events recorded northwest north northeast and east of long valley with ray paths through the caldera are often anomalous in that s wave arrivals have very low amplitudes and high frequency p and s wave energy is missing for the same station event combinations the volcanic and geothermal history of the region suggests that ray paths for these anomalous signals have passed through magma which absorbed much of the s wave energy and also attenuated the higher frequencies with over 1200 normal and anomalous ray paths through the caldera we have located two apparently massive magma bodies in the central and northwest caldera as well as two more dispersed magma areas in the southern caldera and beneath crowley lake the central magma body extends from 4 5 to at least 13 km beneath the surface and the northwest body is as shallow as 5 5 km these two magma bodies are probably connected below about 8 km secondary arrivals seen on select seismograms are tentatively interpreted as reverberations inside the central magma chamber and are consistent with the interpreted lateral extent of the magma the northwest and central magma bodies lie beneath the northwest and southeast corners of the caldera s resurgent dome and probably connect beneath the dome s center also the shallower parts of these magma bodies and the southern anomalous area lie beneath the surface expression of the medial graben faults suggesting that structural features seen at the surface of the valley may be related to magma location at depth