comparison of esr ages of corals from marine terraces with 14c and 230th 234u ages the ages of corals from marine terraces in the ryukyu islands of japan have been determined by electron spin resonance esr esr ages deduced from the total dosage of natural radiation taking the time dependent dose rate due to 238 u series disequilibrium into account agreed fairly well with those determined by 14 c and 230 th 234 u dating the esr age can be extended well beyond the limits of 14 c dating 50 000 years and the 230 th 234 u method 300 000 years to a million years

climatology and latitudinal gradients of quiet time thermospheric neutral winds over millstone hill from fabry perot interferometer measurements 1 midlatitude nighttime thermospheric neutral winds are strongly dependent on season solar activity and latitude we use an extensive database of wind measurements made during 1989 2001 by the millstone hill fabry perot interferometer to study the detailed climatology of quiet time neutral winds near an altitude of 250 km to facilitate the analysis of these data we develop a local time day of year solar flux and latitude dependent empirical model with the latitude dependence obtained by considering north looking and south looking observations separately our results show that the zonal winds are predominantly eastward after dusk and westward before dawn with the strongest eastward winds occurring in the winter and with an east to west transition that occurs earliest in the summer the zonal winds exhibit weak to moderate latitudinal gradients with more westward values to the north the zonal wind magnitudes decrease with increasing solar flux the strongest trends occur during winter the meridional winds are predominantly equatorward in all cases and exhibit strong latitudinal gradients with larger values to the north the maximum nighttime equatorward winds decrease with increasing solar flux except during summer when there is no significant solar activity variation they are largest during the summer except at solar minimum when a semiannual variation is observed and the peak winds occur during the equinoxes earlier studies of midlatitude wind measurements are generally consistent with our data with our results providing a considerably more detailed description of the nighttime wind climatology at midlatitudes

esr dating of pleistocene mammals and marine shells from the coastal plain of rio grande do sul state southern brazil abstract the coastal plain of rio grande do sul state cprs in southern brazil encompasses four barrier lagoon depositional systems formed by marine highstands during the quaternary but the ages of the pleistocene systems older than 125 ka are not precisely known due to the lack of numerical dates in order to refine the chronology of these deposits several fossils of terrestrial mammals collected in the fluvial facies of the lagoon system iii and fossil shells from the marine facies of the barrier system ii exposed in the southern sector of the cprs were subject to dating by electron spin resonance esr the ages of the mammalian remains range from 90 10 to 43 3 ka thus representing the last glacial cycle mis 4 and 3 the mean eu age of the shells is 224 24 6 ka but this value is considered younger than the real age because of excessive uranium uptake observed among the younger shells an estimated mean age of some 235 238 ka would agree with other esr and tl ages obtained for fossils and sediments collected from beds overlying the shells and would be consistent with the sea level highstand at the early mis 7 substage 7e the presence of bivalves and foraminifers that indicate ocean temperatures higher than at present seems to corroborate this estimate given that mis 7e was characterized by hypsithermal conditions

further studies on the use of quartz grains from fault gouges to establish the age of faulting abstract quartz grains were selected from samples of intrafauit material at two outcrop sites of the atotsugawa fault in central japan surface textures of the grains observed by scanning electron microscope were classified into texture groups i iv in the order from a simple feature through increasing undulations to a texture with cavities the defects in the quartz measured by electron spin resonance gave absolute ages using the grains the relative ages by surface texture groups were tentatively correlated to the absolute ages as determined by the electron spin resonance it was disclosed that subgroups ia and ib were stable during the period of 0 9 ma and changed through intermediate subgroup ic in a period ranging from 0 9 to 1 2 ma and then to group ii after 1 2 ma therefore the surface texture groups can change from subgroups ia and ib through intermediate subgroup ic to group ii with increasing age this indicates that the surface texture groups of quartz grains in the fault are effective for dating fault activity concisely

esr dating in quaternary geology abstract electron spin resonance esr a relatively new dating technique was first suggested by zeller et al 1967 zeller 1968 and levy 1968 it has made substantial progress in frequent applications in the last few years esr dating is based on the direct measurement of the amount of radiation induced paramagnetic electrons trapped in crystal defects these free electrons were generated by alpha beta and gamma radiation of natural radioelements e g u th k and have accumulated in the minerals over geologic time the esr age is obtained by dividing the total amount of accumulated radiation dose archaeological dose ad by the dose per year annual dose this review comprises four major parts the principles of the method the determination of the archaeological dose ad the determination of the annual dose and a compilation of datable materials several questions remain the evaluation of the ad the determination of the annual dose and particularly with respect to the nature and stability of the electron traps used for dating

the delicate balance between soil production and erosion and its role on landscape evolution abstract the diversity in landscapes at the earth s surface is the result amongst other things of the balance or imbalance between soil production and erosion while erosion rates are well constrained it is only recently that we have been able to quantify rates of soil production uranium series isotopes have been useful to provide such estimates independently of erosion rates in this study new u series isotope are presented data from weathering profiles developed over andesitic parent rock in puerto rico and granitic bedrock in southeastern australia the site in australia is located on a highland plateau neighbouring a retreating escarpment where soil production rates between 10 and 50 mm kyr have been determined the results show that production rates are invariant in these two regions of australia with values between 15 and 25 mm kyr for the new site andesitic soils show much faster rates about 200 mm kyr overall soil production rates determined with u series isotopes range between 10 and 200 mm kyr this is comparable to erosion rates in soil mantled landscapes but faster than erosion in cratonic areas and slower than in alpine regions and cultivated areas this suggests that soil mantled landscapes maintain soil because they can there is a balance between production and erosion similarly thick weathering profiles develop in cratonic areas because despite slow erosion rates soil production is still significant bare landscapes in alpine regions are probably the result of the inability of soil production to catch up with fast erosion rates although this needs testing by u series isotope studies of these regions finally the range of production rates is up to several orders of magnitude lower than erosion rates in cultivated areas demonstrating quantitatively the fast depletion of soil resources with common agricultural practices

dating of fossil shells with electron spin resonance electron spin resonance esr dating of sea shells has been made using the paramagnetic defects produced by natural radiation the total dose of natural radiation of the materials termed the archaeological dose has been determined from esr signals of defects in sea shells from northern japan whose ages are known from the sediments or from the radioisotope dating an annual dose of about 0 03 0 04 rad yr explains the age of shells from a few thousand to a million years the new method of esr dating will be useful for sediment age determination and for other geological studies

numerical dating of a late quaternary spit shoreline complex at the northern end of silver lake playa mojave desert california a comparison of the applicability of radiocarbon luminescence terrestrial cosmogenic nuclide electron spin resonance u series and amino acid racemization methods a late quaternary spit shoreline complex on the northern shore of pleistocene lake mojave of southeastern california usa was studied with the goal of comparing accelerator mass spectrometry ams radiocarbon luminescence electron spin resonance esr terrestrial cosmogenic radionuclide tcn surface exposure amino acid racemization aar and u series dating methods the pattern of ages obtained by the different methods illustrates the complexity of processes acting in the lakeshore environment and highlights the utility of a multi method approach tcn surface exposure ages mostly 20 30 ka record the initial erosion of shoreline benches whereas radiocarbon ages on shells determined in this and previous studies within the spit supported by aar data record its construction at fluctuating lake levels from 16 to 10 ka luminescence ages on spit sediment 6 7 ka and esr ages on spit shells 4 ka are anomalously young relative to radiocarbon ages of shells within the same deposits the significance of the surprisingly young luminescence ages is not clear the younger esr ages could be a consequence of post mortem enrichment of u in the shells high concentrations of detrital thorium in tufa coating spit gravels inhibited the use of single sample u series dating detailed comparisons such as this provide one of the few means of assessing the accuracy of quaternary dating techniques more such comparisons are needed

the evolution of weathering profiles through time new insights from uranium series isotopes the sustainability of soil is a major issue for society in principle the evolution of soil resources can be constrained by comparing the rates of soil erosion and production cosmogenic isotopes provide one measurement of soil erosion rates they can also be used to estimate soil production rates but only if erosion is assumed to be balanced by production this implies that the evolution of soil resources thinning thickening or constant since soil thickness is assumed to be constant with time here we utilise an independent method to estimate soil production rates using uranium series u series isotopes the study of a site in temperate australia undisturbed by human activity shows that soil production rates inferred from u series isotopes are similar to erosion rates derived from beryllium 10 10be measurements implying that at this site there is no net accumulation or loss of soil saprolite production rates the migration rate of the weathering front into the bedrock are also similar to erosion rates so the thickness of the entire weathering profile is effectively in steady state this study demonstrates that the combination of u series and cosmogenic isotopes can be used to quantitatively assess soil evolution and the development of weathering profiles preliminary observations suggest that the rate of bedrock weathering i e saprolite production in temperate australia is of the same order of magnitude as that inferred for laterites in tropical climates this may suggest that for thick weathering profiles although the extent of weathering strongly differs between temperate and tropical climates the migration of the weathering front into the bedrock occurs at a relatively uniform rate regardless of present day climatic conditions

observations from millstone hill during the geomagnetic disturbances of march and april 1990 the incoherent scatter radars at millstone hill operated continuously during the periods march 16 23 and april 6 12 1990 providing observations of large scale ionospheric structure and dynamics over a large portion of eastern north america major geomagnetic storms occurred during each of these periods with deep nighttime ionospheric troughs and large magnetospheric convection electric fields observed equatorward of millstone the millstone observations provide a comprehensive data set detailing storm induced ionospheric effects over a 35 span of latitude during both of these intervals at the latitude of millstone the ionospheric peak height hmf2 rose above 600 km in the trough on march 22 and 23 and reached 500 km at night on april 11 and 12 increased recombination apparently due to the strong electric fields the temperature dependent recombination rate coefficient and neutral composition changes greatly depleted the f2 region over a wide latitude range during the day on april 10 1990 this resulted in an ionosphere dominated by molecular ions with ionospheric peak heights below 200 km on this day a number of frictional heating events during the disturbed periods are seen from comparison of ion temperature and velocity measurements the most intense event took place near 1200 ut 0715 lmt on april 10 1990 when kp reached 8 at 0110 ut on march 21 line of sight ion velocities in excess of 500 m s 1 were observed at the extreme southern limit of the millstone steerable radar s field of view 40 apex magnetic latitude at an altitude of 700 km these could be due to penetration of magnetospheric electric fields or electric fields associated with ring current shielding in the storm time outer plasmasphere about an hour later ion outflow was observed just equatorward of millstone this is most likely due to heating from a latitudinally confined region of intense westward convection neutral meridional winds above millstone were obtained by three different techniques employing radar and fabry perot measurements the latitude variation of the winds was also estimated from radar measurements of hmf2 and electric fields using the servo model method strong equatorward nighttime neutral wind surges were found during both the march and april disturbances which reached the equatorward limit of the observations at f peak heights

rapid regolith formation over volcanic bedrock and implications for landscape evolution abstract the ability to quantify how fast weathering profiles develop is crucial to assessing soil resource depletion and quantifying how landscapes evolve over millennia uranium series isotopes can be used to determine the age of the weathering front throughout a profile and to infer estimates of regolith production rates because the abundance of u series isotopes in a weathering profile is a function of chemical weathering and time this technique is applied to a weathering profile in puerto rico developed over a volcaniclastic bedrock u series isotope compositions are modelled revealing that it takes 40 60 kyr to develop an 18 m thick profile this is used to estimate an average regolith production rate of 334 46 mm kyr this value is higher by a factor of up to 30 when compared to production rates estimated for weathering profiles developed over granitic or shale lithologies this quantitatively underpins the lithological control on rates of regolith production in a neighbouring watershed but over a granitic bedrock production rates are only 30 40 mm kyr moreover by comparing these results to a compilation of soil erosion rates it is clear that landscapes are controlled by the balance or imbalance between regolith production and erosion soil mantled landscapes are the result of a relative balance between production and erosion whereas in cratonic areas thicker weathering profiles are generated because erosion fails to match regolith production rates

the late pleistocene palaeoenvironmental evolution in northern eurasia through the prism of the mollusc shell based esr dating evidence abstract long term investigations devoted mostly to the eurasian arctic sedimentary deposits have provided dated climatic sequence within the late pleistocene period most of the dates ca 315 were obtained by electron spin resonance esr method on marine mollusc remains taken directly from transgressive marine sedimentary deposits here it is shown that the climatic signature revealed in the studied sedimentary sequences can be compared by proxy and chronologic correlation with the climatic signals recorded in different parts of the continent from deposits of marine freshwater and terrestrial origin the resulting climate chronostratigraphic record allow the last interglacial to be placed approximately between 145 140 ka and 70 ka with concentration of overwhelming majority of the warm climate related dates ca 82 in the second half of marine isotope stage mis 5 in the time range between 110 and 70 ka this evidence coincides with integrative multidisciplinary results derived from the south eastern coast of the gulf of finland they show unambiguously that the second half of the mis 5 sequence at least between ca 94 ka and 71 ka reflects the fully interglacial character of the studied deposits the climate chronostratigraphic record within mis 3 displays a sequence of three successive palaeoenvironmental events 59 0 52 0 ka 47 5 40 0 ka and 32 4 24 8 ka which are interpreted as the consequence of large scale climate amelioration during which marine sedimentation occurred on palaeo shelves what is now dry land the consistency of the parallel comparative dating results obtained in this study by different methods both the numerical and relative exemplify the potential of palaeodosimetric dating methods mainly used in this study mollusc shell based electron spin resonance esr and feldspar based infrared optically stimulated luminescence ir osl to chronologically organize the sequence of the late pleistocene palaeoenvironmental events and to improve understanding of the palaeoenvironmental evolution during this period

evaluation of pleistocene groundwater flow through fractured tuffs using a u series disequilibrium approach pahute mesa nevada usa abstract groundwater flow through fractured felsic tuffs and lavas at the nevada national security site represents the most likely mechanism for transport of radionuclides away from underground nuclear tests at pahute mesa to help evaluate fracture flow and matrix water exchange we have determined u series isotopic compositions on more than 40 drill core samples from 5 boreholes that represent discrete fracture surfaces breccia zones and interiors of unfractured core the u series approach relies on the disruption of radioactive secular equilibrium between isotopes in the uranium series decay chain due to preferential mobilization of 234 u relative to 238 u and u relative to th samples from discrete fractures were obtained by milling fracture surfaces containing thin secondary mineral coatings of clays silica fe mn oxyhydroxides and zeolite intact core interiors and breccia fragments were sampled in bulk in addition profiles of rock matrix extending 15 to 44 mm away from several fractures that show evidence of recent flow were analyzed to investigate the extent of fracture matrix water exchange samples of rock matrix have 234 u 238 u and 230 th 238 u activity ratios ar closest to radioactive secular equilibrium indicating only small amounts of groundwater penetrated unfractured matrix greater u mobility was observed in welded tuff matrix with elevated porosity and in zeolitized bedded tuff samples of brecciated core were also in secular equilibrium implying a lack of long range hydraulic connectivity in these cases samples of discrete fracture surfaces typically but not always were in radioactive disequilibrium many fractures had isotopic compositions plotting near the 230 th 234 u 1 1 line indicating a steady state balance between u input and removal along with radioactive decay numerical simulations of u series isotope evolution indicate that 0 5 to 1 million years are required to reach steady state compositions once attained disequilibrium 234 u 238 u and 230 th 238 u ar values can be maintained indefinitely as long as hydrological and geochemical processes remain stable therefore many pahute mesa fractures represent stable hydrologic pathways over million year timescales a smaller number of samples have non steady state compositions indicating transient conditions in the last several hundred thousand years in these cases u mobility is dominated by overall gains rather than losses of u

short lived u and th isotope distribution in a tropical laterite derived from granite pitinga river basin amazonia brazil application to assessment of weathering rate we have analyzed samples of a 15 m thick profile weathered from the madeira granite located in the pitinga basin river north of manaus in the state of amazonia brazil this profile consists essentially of a yellow red saprolite covered by a soil u and th concentrations are particularly high in the granite 20 and 80 g g respectively normalized element to th concentrations indicate that th is most resistant to chemical weathering except to some extent in the top soil higher concentrations in the saprolite compared to the granite comprise a relative enrichment resulting from a loss of mass the saprolites are initially generated by a descending weathering front which alters the granite to a yellow red saprolite a second front close to the top turns the saprolite into a soil weathering has led to leaching of u the 234u 238u and 230th 238u isotopic ratios are in radioactive disequilibrium numerous nodules are present and apparently started to form at the base of the saprolite these nodules achieve more developed form during their relative ascent until they are reached by the descending top front where they undergo dissolution the th and pb are concentrated in the nodules close to the top front the u being more mobile is strongly leached by the first front and most of the remainder freed by the second engages in a descending flux which supplies the underlying saprolite using the data an attempt is made to model the isotopic distribution in the profile we conclude that the first front has descended at a rate of 5 cm 1000 yt and that the time needed to create the saprolite must have been around 300 000 yr

eustatic sea level and climate changes over the last 600 ka as derived from mollusc based esr chronostratigraphy and pollen evidence in northern eurasia we reconstruct and correlate palaeoclimatic events and deposits from shelf glacial periglacial and extraglacial zones of northern eurasia over the last 600 000 years the chronostratigraphical correlation of identified palaeoenvironmental and sealevel events and corresponding horizons is based on electron spin resonance esr analysis of subfossil mollusc skeletal remains from marine freshwater and acheulian bearing cave site deposits over 230 shell samples from more than 40 sites along the continental margin of eurasian north in the black and caspian sea basins and terrestrial shells from a lower palaeolithic cavesite in the northern caucasus were dated via esr to produce a late quaternary geochronology the pleistocene composite section of the loess palaeosoil formation includes two reference sections likhvin and arapovichi from the centre of the easteuropean plain the palyno chronostratigraphic record is interpreted as the product of six warm climate high sea level events including the current interglacial and six glacial events they are presented either as complete climatic rhythms of glacial and interglacial rank or by considerable portions of climatic phytocoenotic phases constituents of the rhythm the full interglacial conditions are centred at about 580 400 310 220 and between 145 70 calendar ka a broad correspondence between long palynological sequence directly esr dated warm climate related events and other palaeoenvironmental records described in the literature has been noted for 11 upper oxygen isotope stages 11 to 1 the results obtained in this study exemplify the potential of integrated chrono climatostratigraphic sequences in linking marine and terrestrial palaeoclimate records that may eventually span the whole brunhes chron d 2002 elsevier science b v all rights reserved

esr dating of fossil shells in the middle to upper pleistocene strata in japan abstract the accuracy of the esr ages of fossil shells from the boso peninsula ooiso hills and the miyazaki plain in japan in the middle to upper pleistocene were examined the measurement test with a thermoluminescent dosimeter at the sampling point suggests that the dose rate of cosmic rays must be added to the calculated dose rate from chemical analysis the results show that the esr ages are in good agreement with the stratigraphically estimated ages however according to the chemical analysis of the mollusc shell itself several shells give an abnormally high concentration of uranium this may indicate that the shell has absorbed uranium from outside especially in sandy sediments

regolith production rates calculated with uranium series isotopes at susquehanna shale hills critical zone observatory abstract in the critical zone where rocks and life interact bedrock equilibrates to earth surface conditions transforming to regolith the factors that control the rates and mechanisms of formation of regolith defined here as material that can be augered are still not fully understood to quantify regolith formation rates on shale lithology we measured uranium series u series isotopes 238 u 234 u and 230 th in three weathering profiles along a planar hillslope at the susquehanna shale hills observatory ssho in central pennsylvania all regolith samples show significant u series disequilibrium 234 u 238 u and 230 th 238 u activity ratios range from 0 934 to 1 072 and from 0 903 to 1 096 respectively these values display depth trends that are consistent with fractionation of u series isotopes during chemical weathering and element transport i e the relative mobility decreases in the order 234 u 238 u 230 th the activity ratios observed in the regolith samples are explained by i loss of u series isotopes during water rock interactions and ii re deposition of u series isotopes downslope loss of u and th initiates in the meter thick zone of bedrock that cannot be augered but that nonetheless consists of up to 40 clay silt sand inferred to have lost k mg al and fe apparent equivalent regolith production rates calculated with these isotopes for these profiles decrease exponentially from 45 m myr to 17 m myr with increasing regolith thickness from the ridge top to the valley floor with increasing distance from the ridge top toward the valley apparent equivalent regolith residence times increase from 7 kyr to 40 kyr given that the ssho experienced peri glacial climate 15 kyr ago and has a catchment wide averaged erosion rate of 15 m myr as inferred from cosmogenic 10 be we conclude that the hillslope retains regolith formed before the peri glacial period and is not at geomorphologic steady state both chemical weathering reactions of clay minerals and translocation of fine particles colloids are shown to contribute to mass loss of u and th from the regolith consistent with major element data at ssho this research documents a case study where u series isotopes are used to constrain the time scales of chemical weathering and regolith production rates regolith production rates at the ssho should be useful as a reference value for future work at other weathering localities

soil production and hillslope transport in mid latitudes during the last glacial interglacial cycle a combined data and modelling approach in northern ardennes

late quaternary erosion in southeastern australia a field example using cosmogenic nuclides late quaternary rates of apparent soil production bedrock incision and average erosion are determined for the southeastern highlands of australia using in situ produced cosmogenic nuclide concentrations of 10 be and 26 al apparent soil production rates define a steep inverse exponential function of soil depth with a maximum of 143 m ma 1 under zero soil depth there were no observed soil depths between about 25 cm and zero however such that the maximum observed rate is about 50 m ma 1 the bredbo river catchment average erosion rate is 157 1mm a 1 and is similar to the average hillslope erosion rate of 167 1mm a 1 bedrock incision rates average 9 mma 1 and suggest that the higher rates of hillslope erosion may be in response to a pulse of incision perhaps generated by knickpoint propagation bedrock erosion rates inferred froma tor profile average 3 8 mma 1 with higher rates on other more weathered tor tops an aboveground tor profile of nuclide concentrations is consistent with a simple model of rapid stripping of the surrounding saprolite supporting the view that at least one episodic period of increased denudation has affected the landscape evolution of the highlands we test this hypothesis by using a simple landscape evolution model to reasonably predict the spatial variation of soil depth as well as the emergence of tors r 2001 elsevier science ltd and inqua all rights reserved

coupling uranium series and 10be cosmogenic radionuclides to evaluate steady state soil thickness in the betic cordillera abstract on earth the critical zone is the near surface environment where interactions between the atmosphere lithosphere hydrosphere and biosphere take place the development of the regolith mantle is controlled by the downwards propagation of the weathering front into the bedrock and denudation at the surface of the regolith by mass movements water and wind erosion when the removal of surface material is approximately balanced by the production of weatherable material at the bottom of the regolith profile the soil system is assumed to be in steady state although recent literature on chemical weathering often assumes that soils have a steady state thickness the concept has rarely been validated with empirical field data in this study we present and compare analytical data from two independent isotopic techniques in situ produced cosmogenic nuclides and u series disequilibria to constrain soil development under semi arid climatic conditions three soil profiles were sampled across the betic ranges at the ridge crest of zero order catchments with distinct topographic relief hillslope gradient and 10be derived denudation rate soil production rates determined based on u series isotopes 238u 234u 230th and 226ra are of the same order of magnitude as 10be derived denudation rates suggesting steady state soil thickness in two out of three sampling sites our results show the potential of a combined u series disequilibria and in situ 10be isotope approach to evaluate steady state soil thickness our study also illustrates the frontiers in applying u series disequilibria to track soil production in environments characterized by weak soil development

late quaternary multiple incised valley systems an unusually well preserved stratigraphic record of two interglacial valley fill successions from the arno plain northern tuscany italy

the esr age of portlandia arctica shells from glacial deposits of central latvia an answer to a controversy on the age and genesis of their enclosing sediments abstract the occurrence of portlandia arctica shells in glacigenic sediments of central latvia had created a controversy in many publications about 1 their age ranging from the holsteinian to the late weichselian and 2 the genesis of their enclosing sediments glacial glaciomarine or marine our reinvestigation of the main object of controversy the licupe site leads to a conclusion that the sedimentary package of diamictons clays and sands containing portlandia arctica shells and marine microfossils is a large glacial raft that had been transported and deposited by the riga lobe during the weichselian the electron spin resonance esr ages on five sets of portlandia arctica shells from the licupe and daugmales tom ni sites range from 86 0 6 8 to 105 0 9 2 ka bp these esr age determinations and the cool climate indicators of the associated microflora and microfauna suggest that their source sediments probably in the gulf of riga are marine clays of early weichselian age probably correlative to the brorup interstadial in central latvia portlandia arctica shells and their enclosing clay occur resedimented or translocated in glacial deposits during weichselian glacial advances

esr and 230th 234u dating of speleothems from aladaglar mountain range amr in turkey abstract electron spin resonance esr and 230 th 234 u ages of speleothem samples collected from karstic caves located around 3000 m elevation in the aladaglar mountain range amr south central turkey were determined in order to provide new insight and information regarding late pleistocene climate esr ages were validated with the 230 th 234 u ages of test samples the esr ages of 21 different layers of six speleothem samples were found to range mostly between about 59 and 4 ka which cover the marine oxygen isotope stages mis mis 3 to mis 1 among all only six layers appear to have deposited during mis 8 and 5 most of the samples dated were deposited during the late glacial stage mis 2 it appears that a cooler climate with a perennial and steady recharge was more conducive to speleothem development rather than a warmer climate with seasonal recharge in the amr during the late quaternary this argument supports previous findings that suggest a two fold increase in last glacial maximum mean precipitation in turkey with respect to the present value

electron spin resonance esr dating abstract esr dating has been systematically applied in earth sciences and archaeology since 1975 when ikeya dated a stalactite from the akiyoshi cave in japan in the meantime this new technique has been successfully applied to the dating of materials such as speleothems spring deposited travertines mollusc shells corals and tooth enamel the present research focuses on the dating of quartz which allows the age assessment of heated ceramics volcanic rocks intrafault material or windblown sediments esr dating is based on the measurement of the number of paramagnetic centers in a mineral these centers are generated by alpha beta and gamma radiation of the matural radioelements such as u th and k and have accumulated over time two parameters have to be determined the accumulated dose ad and the dose rate d to which the sample was exposed this review comprises three major parts a introduction into esr dating b application of the method and c appendices giving detailed description of dose rate calculation physical basis of electron spin resonance the esr spectrometer and esr lines the major emphasis lies on the outline of the application of esr dating this includes the discussion of the esr signals of the various materials sampling sample preparation and measurement techniques

sedimentary evolution of a late pleistocene temperate red algal reef coralligene on rhodes greece correlation with global sea level fluctuations autochthonous red algal structures known as coralligene de plateau occur in the modern warm temperate mediterranean sea at water depths from 20 to 120 m but fossil counterparts are not so well known this study describes from an uplifted coastal section at plimiri on the island of rhodes a 450 m long by 10 m thick late pleistocene red algal reef coralligene facies interpreted as being a coralligene de plateau and its associated deposits the coralligene facies constructed mainly by lithophyllum and titanoderma sits unconformably upon the plio pleistocene rhodes formation and is overlain by a maerl facies 2 m a mixed siliciclastic carbonate facies 0 2 m and an aeolian sand facies 2 5 m the three calcareous facies of heterozoan character are correlated with established members in the lindos acropolis formation in the north of the island while the aeolian facies is assigned to the new plimiri aeolianite formation the palaeoenvironmental and genetic stratigraphic interpretations of these mixed siliciclastic carbonate temperate water deposits involved consideration of certain characteristics associated with siliciclastic shelf and tropical carbonate shelf models such as vertical grain size trends and the stratigraphic position of zooxanthellate coral growths integration of these results with electron spin resonance dates of bivalve shells indicates that the coralligene facies was deposited during marine isotope stage 6 to 5e transgressive event ca 135 to 120 ka in water depths of 20 to 50 m and the overlying maerl facies was deposited during regression from marine isotope stage 5e to 5d ca 120 to 110 ka at water depths of 25 to 40 m the capping aeolian sand facies involving dual terrestrial subunits is interpreted as having formed during each of the glacial intervals marine isotope stages 4 71 to 59 ka and 2 24 to 12 ka with soil formation during the subsequent interglacial periods of marine isotope stages 3 and 1 respectively accumulation rates of about 0 7 mm year 1 are estimated for the coralligene facies and minimum accumulation rates of 0 2 mm year 1 are estimated for the maerl facies the existence of older red algal reefs in the plimiri region during at least marine isotope stages 7 245 to 186 ka and 9 339 to 303 ka is inferred from the occurrence of reworked coralligene type lithoclasts in the basal part of the section and from the electron spin resonance ages of transported bivalve shells

mobilization and re distribution of major and trace elements during extreme weathering of basalt in hainan island south china major trace and organic elements of a laterite profile developed on neogene basalts in northern hainan island south china were reported in this paper the aim of which was to investigate element mobilization and re distribution during extreme weathering the results indicate that most of the elements have been mobilized and transferred downwards along the profile by aqueous solution organic matter om can significantly improve the transport of insoluble elements among all the elements th is the least mobile as for the general conservative elements during incipient chemical weathering such as fe ti zr hf nb and ta the removals are up to 20 40 in the upper profile however these elements behave as conservatively as th in the lower profile in the middle profile oxic environment occurs accompanied with significant om decomposition the mn and ce transferred downward are readily oxidized into insoluble mn iv and ce iv and precipitate in the oxic front important om decomposition decreases the capacity of transfer of insoluble elements in aqueous solution consequently al significantly precipitates in the oxic front and rees with the exception of ce precipitate largely in the omdepleted layers co and u are also concentrated in the oxic front in association with mn and ce respectively however cr shows a negative correlation with mn because its response to redox condition changes is reversed from that of mn mn oxides hydroxides fe oxides hydroxides and secondary phosphate minerals other than clay minerals are potential hosts for rees except for ce in the profile rees with high concentrations in the profile seem closely associated with mn oxides hydroxides remarkable highly correlated ce and gd anomalies are observed in the profile ce anomalies are caused by ce precipitation in the oxic environment and successive decomposition of organic matter gd anomalies are likely to have resulted from lower stability constants of gd om complexes compared to those of neighboring rees the overall elemental behaviors in this profile suggest that organic matter plays a very important role in the mobilization and re distribution of the elements during extreme weathering

uranium series isotopes in colloids and suspended sediments timescale for sediment production and transport in the murray darling river system abstract we have measured 238u 234u 230th radioactive disequilibria in five size fractions of colloids and suspended sediments for four rivers from the murray darling river basin se australia continuous compositional trends of composition are observed for 234u 238u and 230th 238u activity ratios over the range of size fractions studied they are explained by the variable contribution of two components detrital alumino silicates and organic matter using relationships between activity ratios and the loss on ignition it is possible to estimate the u series isotopic composition of both detrital and organic end members which provide the best estimate for the composition of the true detrital phase i e controlled only by the removal of elements through weathering and the true dissolved phase i e colloid free respectively when performing a single filtration at 0 2 m it appears that size fractions and

the geomagnetic quiet nighttime thermospheric wind pattern over fritz peak observatory during solar cycle minimum and maximum nighttime thermospheric winds and temperatures at f region heights have been measured over fritz peak observatory colorado 39 9 n 105 5 w with a high resolution fabry perot spectrometer from about november 1972 to the present the winds and temperatures are obtained from the doppler shifts and line profiles of the o i 15 867 k 630 nm line emission the data obtained during geomagnetic quiet conditions ap 20 have been separated into two groups representing solar cycle minimum conditions 1972 1977 and solar cycle maximum conditions 1978 1979 the monthly variation of the nighttime zonal and meridional winds are presented for both groups the results show that during solar cycle minimum the zonal winds are predominantly eastward during the winter months at speeds of 50 75 m s 1 and westward during the summer months at speeds of 50 100 m s 1 the meridional winds measured to the north and south of fritz peak observatory are equatorward throughout most of the night at nearly the same speed the equatorward winds in the summer peak near midnight at about 100 150 m s 1 the equatorward winds in the winter also peak near midnight but with smaller speeds 50 75 m s 1 during solar cycle maximum the zonal winds are again predominantly eastward during the winter months reaching peak speeds of 60 75 m s 1 in the early evening hours and decreasing afterward in the summer the winds are eastward during the early evening hours shifting to westward near midnight and increasing to a maximum speed of 75 100 m s 1 in the early morning hours the meridional winds are poleward at 20 m s 1 in the early evening hours shifting to equatorward near 2100 lt and then increasing in magnitude with maximum speeds near or after midnight there is a considerable difference in the speed of the winds measured to the north and south of fritz peak observatory during the summer the equatorward winds measured to the north are 150 175 m s 1 whereas the equatorward winds measured to the south are 50 75 m s 1 during the winter the speeds are smaller 50 75 m s 1 and 25 30 m s 1 to the north and south of the station respectively calculations made with the national center for atmospheric research thermospheric general circulation model for different seasons are in reasonable agreement with the observations during both solar minimum and solar maximum during solar cycle maximum the observed and calculated meridional wind differences to the north and south of fritz peak observatory are attributed to enhanced auroral heating and ion drag associated with magnetospheric convection north of the observatory the equatorward driven winds slow south of fritz peak observatory owing to the diminishing influence of high latitude forcings

chemical mobilizations in laterites evidence from trace elements and 238u 234u 230th disequilibria geochemical and mineralogical investigations including measurements of major and trace elements sr isotope ratios and 238u 234u 230th activity ratios were made on an old african laterite to reconstruct its formation steps and assess recent chemical mobilization the present data support a scenario of discontinuous formation for the laterite with different bedrock weathering conditions during the formation of each unit rather than a scenario of continuous formation absolute accumulation of fe u and lanthanides in the uppermost ferruginous unit suggests an autochthonous origin of this iron cap by leaching of an older overlying profile present chemical distributions of lanthanides as well as of rb k ba and sr within the profile cannot be linked to the mineralogical distribution of both relictual primary and authigenic secondary phases complementary lanthanide patterns indicate that these elements were primarily accumulated in the uppermost ferruginous unit before further remobilization and accumulation in the underlying horizons these redistribution processes may be related to the chemical instability of the ferruginous cap the 238u 234u 230th disequilibria indicate that recent u mobilization occurs in the whole profile and that as for lanthanides there is a vertical redistribution of u from the uppermost ferruginous unit to the underlying horizons moreover these data show that both u losses and gains exist at each level of the profile a simple modeling of this double u mobilization process is proposed to interpret the 238u 234u 230th data differences in the mobilization and fractionation intensities of the u input and removal processes can account for the two evolution trends which distinguish the ferruginous unit from the underlying ones furthermore on the basis of this modeling the profile appears to be in a transient state because of recent changes in the u mobilization conditions which could correspond to major pleistocene climatic variations

soil formation rates on silicate parent material in alpine environments different approaches different results abstract high mountain soils develop in particularly sensitive environments consequently deciphering and predicting what drives the rates of soil formation in such environments are a major challenge in terms of soil production or formation from chemical weathering the predominating perception for high mountain soils and cold environments is often that the chemical weathering portion of soil development is temperature inhibited often to the point of non occurrence several concepts exist to determine long term rates of soil formation and development we present three different approaches 1 quantification of soil formation from minimally eroded soils of known age using chronosequences known surface age and soil thickness sast 2 determination of soil residence times srt and production rates through chemical weathering using un stable isotopes e g 230 th 234 u activity ratios and 3 a steady state approach using cosmogenic isotopes e g 10 be for each method data from different climate zones and particularly from high mountains alpine environment are compared the sast and steady state approach give quite similar results for alpine environments european alps and the wind river range rocky mountains usa using the srt approach soil formation rates in mountain areas but having a temperate climate do not differ greatly from the sast and steady state approaches independent of the chosen approach the results seem moderately comparable soil formation rates in high mountain areas alpine climate range from very low to extremely high values and show a clear decreasing tendency with time very young soils have up to 3 4 orders of magnitude higher rates of development than old soils 10 5 to 10 6 yr this apparently is a result of kinetic limits on weathering in regions having young surfaces and supply limits to weathering on old surfaces due to the requirement for chemical weathering to occur soil production rates cannot be infinitely high consequently a speed limit must exist in the literature this limit has been set at about 320 to 450 t km 2 a our results from the sast approach show however that in alpine areas soil formation easily reaches rates of up to 800 2000 t km 2 a these data are consistent with previous studies in mountain regions demonstrating that particularly young soils intensively weather even under continuous seasonal snowpack and thus that the concept of temperature controlled soil development soil forming intervals in alpine regions must be reconsidered

mean bedrock to saprolite conversion and erosion rates during mountain growth and decline abstract weathering and associated atmospheric co2 consumption are thought to increase during the erosion of uplifting mountain ranges but the effect of enhanced erosion on weathering is still the subject of active debate we explore the possibility that erosion heterogeneity in uplifting landscapes significantly impacts the temporal relationships among mean uplift erosion and weathering using a 3d landscape evolution model applied to a synthetic surface with different uplift and climate scenarios although we do not strictly simulate the weathering outflux of the mountain we analyze the weathering response through the evolution of the mountain mean saprolite production rate and compare it to the mountain mean erosion rate through time the parametrical analysis shows that the temporal relationship between the mean erosion and saprolite production rates depends mainly on the ratio of the maximum saprolite production rate and the uplift rate wm u we explore two end members 1 when wm u 1 which corresponds to mountain ranges under a hot and humid climate the mean erosion and saprolite production rates vary at the same rate during the uplift and after once the uplift is stopped when the uplift is stopped the mean saprolite production increases and then decreases locally at different times this heterogeneity induces an overall decrease in the mean saprolite production rate 2 when wm u

dating and characterization of polymorphic transformation of aragonite to calcite in pleistocene bivalves from rhodes greece by combined shell microstructure stable isotope and electron spin resonance study absolute dating of diagenesis is a challenging yet significant problem reconstructing the depositional and diagenetic history of a late pleistocene coralligene type red algal reef and overlying maerl red algal sand from the plimiri coastal cliff se island of rhodes greece is enabled using a combination of microstructure stable isotope analyses and electron spin resonance of large bivalve shells partially altered by diagenesis these shells consisting of both original shell aragonite and polymorphic transformed rims now consisting of neomorphic spar provide the opportunity to date the primary age when the shells were precipitated as well as the age of their polymorphic transformation the contamination of samples presented a significant problem for interpreting ages based on data from electron spin resonance esr alone however sample contamination was evaluated with quantitative xrd providing the opportunity to apply corrections which increased reliability of the ages the carbon and oxygen stable isotope values and the neomorphic spar microtexture suggested that the polymorphic transformation at plimiri took place in a meteoric environment with a high and increasing fluid rock ratio the electron spin resonance dates combined with the vertical sedimentary evolution allowed to assign the formation of the red algal reef to the marine isotope stages 6 to 5e transgressive event ca 135 to 120 ka and to identify meteoric diagenetic phases during possibly the marine isotope stage 5d and the upper marine isotope stage 5c to lower 3 the use of electron spin resonance dating of neomorphic spar and age correction for sample contamination is presented herein for the first time and the results suggest that it might provide a useful tool to date late pleistocene diagenesis

esr dating evidence for early man at a lower palaeolithic cave site in the northern caucasus as derived from terrestrial mollusc shells eight terrestrial shell samples from recent excavations at treugolnaya triangular cave northern caucasus were analysed by electron spin resonance esr to produce a chronology for the most ancient acheulian bearing layers of the cave site the lifetime of the 2 0012 centre used for dating is about 3 108 at 53c that allows to date the multi level sequence of the cave site at least in the range of the last one million years the dating results obtained suggest that the rst from the bottom archaeological layer 7a is likely to be about 583 000a old and the next 5b is some 393 000 a old these layers can be correlated with oxygen isotope stages 15 and 11 respectively the estimates obtained imply that man presumably reached the northern caucasus at least as early as the beginning of stage 15 i e much earlier than generally recognised the leaving of the cave by ancient man due to development of glacial environment during the subsequent stage s can probably be linked with the penetration of man to the southern areas of the east european plain 2000 elsevier science ltd all rights reserved