late pleistocene coastal evolution of san giovanni di sinis west sardinia western mediterranean abstract the upper pleistocene succession of coastal deposits outcropping at san giovanni di sinis west sardinia has been studied since the 1960s however the absence of consistent radiometric ages has allowed the production of competing stratigraphic subdivisions of these deposits with different isotopic stage ois mis attributions the succession is composed of sandy to gravelly shallow marine coastal aeolian and alluvial fan plain deposits facies analysis and log correlations show the presence of three unconformities t1 t2 t3 always overlain by shallow marine deposits cutting through the substrate alluvial fan or aeolian sediments we have collected three samples for optically stimulated luminescence osl dating at the top of each shallow marine deposit the succession is composed of four unconformity bounded units u1 u2 u3 u4 and the new osl dates indicate the presence of three different sea level highstands the first unit u1 which is composed of shallow marine to aeolian deposits and overlies transgressive surface t1 is related to a marine transgression during ois 7 186 13 ky unit 2 is composed of continental deposits and formed during ois 6 unit 3 represents ois 5 and overlies a transgressive surface t2 more precisely subunit u3a is related to ois 5e 120 10 ky eu tyrrhenian or eemian sensu strictu and is characterized by shallow marine to aeolian deposits developed during both transgressive and highstand phases the following bay deposits of subunit 3b are associated with ois 5c 100 5 ky and record a second transgressive event t3 and highstand phase occurred during the neo tyrrhenian the succession of san giovanni di sinis ends with continental deposits of unit 4 associated to a sea level fall that took place at the beginning of the last glacial phase ois 4

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

8000 years of environmental evolution of barrier lagoon systems emplaced in coastal embayments nw iberia the rocky and indented coast of nw iberia is characterized by the presence of highly valuable and vulnerable small and shallow barrier lagoon systems structurally controlled the case study was se

sulfate oxygen 17 anomaly in an oligocene ash bed in mid north america was it the dry fogs 1 the oxygen and sulfur isotope compositions of sulfate particularly the oxygen 17 anomaly provide clues to the origin of sulfate we report a variable oxygen 17 anomaly for water and acid leached sulfate from an oligocene volcanic ash bed in the northern high plains u s a we find no sulfate o 17 anomaly however in freshly collected ashes from recent eruptions around the world the oligocene paleoclimatic and sedimentary evidence argues against a hyperarid condition in the high plains thus a long term background atmospheric sulfate accumulation is less likely the origin combining sulfur isotope data we suggest that the anomalous sulfate was associated with volcanic eruptions in the west but was not directly carried by ash falls extreme dry fog sulfate haze events resulting from tropospheric oxidation of volcanic sulfur gases might provide a viable explanation for the sulfates in the ash bed that carry the oxygen 17 anomaly

sequence stratigraphy of carbonate evaporite basins models and application to the upper permian zechstein of northeast england and adjoining north sea the successions of carbonate evaporite basins which are periodically cut off from the world ocean are considered in terms of their sequence stratigraphy two basin types are distinguished those where incomplete drawdown takes place and those showing complete drawdown and wholesale basin desiccation it is argued that following relative sea level falls sequences begin with the evaporites precipitated as marginal lowstand gypsum wedges in the first basin type and as lowstand basin centre halite fills in the second the evaporites pass up into carbonate sediments which are mainly deposited on shallow water platforms around the basin during transgressive and highstand systems tracts the concepts and models developed are applied to the zechstein upper permian strata of northeast england and adjoining north sea seven sequences are proposed with some containing thin parasequences the sequence approach to carbonate evaporite basins which considers both basin margin and basin centre facies gives a more encompassing perspective of sedimentation than the traditional cycle concept with its emphasis on the basin centre

the impact of north atlantic storminess on western european coasts a review abstract instrumental and documentary records of storminess along the atlantic coast of western europe show that storm activity exhibits strong spatial and temporal variability at annual and decadal scales there is evidence of periods of increased storminess during the little ice age lia ad 1570 1990 and archival records show that these periods are also associated with sand movement in coastal areas independent evidence of sand movement during the lia is derived from dating the coastal sand deposits using luminescence or radiocarbon methods the holocene record of sand drift in western europe includes episodes corresponding to periods of northern hemisphere cooling particularly at 8 2 ka and provides the additional evidence that these periods like the lia were also stormy

a calendar age estimate of the younger dryas holocene boundary at krakenes western norway the younger dryas holocene transition yd h in the sediments of krakenes lake western norway is well marked both lithologically and palaeobiologically at 756 5 cm in the investigated core a ser

quartz osl dating of loess deposits since the late glacial in the southeast of caspian sea abstract here we present loess deposits since the late glacial dated by osl technique in the southeast of the caspian sea bordering continents of asia and europe chronology of holocene loess deposits are rarely reported in eastern europe and western asia especially for their spacious mid latitude adjacent region between balkans to the west and pamirs to the east in this study an osl based chronology was developed for loess deposits in northern iranian plateau based on the ybd loess profile which locates close to center of hilly iranian loess plateau in the southeast of the caspian sea and on the northern slope of the alborz mountains the osl characteristics and their reliability were investigated on coarse grained quartz 63 90 m of the profile a preheat plateau test and dose recovery test of which reveal that the lower preheat is suitable for loess equivalent dose determination in the area in addition the sar osl is an appropriate methodology for dating loess deposited since the late glacial in situ with preservation of a complete record of loess accumulation since the late glacial ybd section contains a potentially valuable paleoclimatic record for caspian region and hence the vast transitional region between asia and europe

surface temperature in nw europe during the younger dryas agcm simulation compared with temperature reconstructions during the younger dryas yd the climate in nw europe returned to near glacial conditions to improve our understanding of climate variability during this cold interval we compare an agcm simulation of this climate performed with the echam model with temperature reconstructions for nw europe based on geological and paleoecological records maps for the mean winter summer and annual temperature are presented the simulated winters are consistent with reconstructions in the northern part of the study area a strong deviation is noted in ireland and england where the simulation is too warm by at least 10 c it appears that the n atlantic was cooler than prescribed in the yd simulation including a southward expansion of the sea ice margin the comparison for the summer shows a too warm continental europe in the simulation supposedly these anomalously warm conditions are caused by the agcm s response to the prescribed increased summer insolation the region of maximum summer cooling is similar in both the simulation and reconstruction i e s sweden we suggest that this is due to the local cooling effect of the scandinavian ice sheet compared to the present climate a considerable increase of the annual temperature range is inferred especially for regions close to the atlantic ocean

varve chronology and palynology of the lateglacial in northwest germany from lacustrine sediments of hamelsee in lower saxony abstract the hamelsee is a dolina from a collapse over permian salt that occurred at the end of the pleniglacial it is more than 21 m deep and contains 18 m of lacustrine sediments the lateglacial sediments in the central part of the lake consist of 2 7 m from 15 to 17 7 m of sapropelic and silty muds which are mostly laminated and partly bioturbated minor slumps occur mainly during colder phases the subdivision of the lateglacial is based on pollen zones multidisciplinary studies of the microfacies from thin sections geochemistry pollen analysis and rotifer analysis allow environmental and palaeoclimatological interpretations to be made the biozones of the lateglacial and their boundaries are marked by rapid climatic changes though covering comparatively short periods of time they are not monotonous but characterized by minor internal climatic fluctuations the sediments of the meiendorf and oldest dryas are not laminated the allerod sediment is seasonally varved without interruption and encompasses 625 yr the eruption of the laacher see volcano 12 900 cal bp had an impact on the climate during the following 10 yr the transition from the allerod to the younger dryas took some 50 yr and it occurred 200 yr after the eruption of the laacher see volcano the abrupt change at the end of the lateglacial 11 560 cal bp occurred within less than 10 yr however many proxies reacted with a time lapse of 15 to 30 yr

deformation structures and an alteration zone linked to deposition of volcanogenic sulphate in an ancient playa oligocene of nebraska usa historic sulphur rich volcanic eruptions have altered global climate for as much as five years and much larger events are known from the geologic record at scotts bluff nebraska early oligocene strata of the lower arikaree group contain a tephra bed with abundant calcite pseudomorphs after gypsum previous work has shown sulphate from the pseudomorphs in this tephra bears a high 17 o anomaly indicative of oxidation of sulphur gases by ozone or hydrogen peroxide in the atmosphere possible sources of the tephra were caldera eruptions at about 28 ma in the san juan volcanic field of southwestern colorado 500 km sw of the study site and the eastern great basin 1000 km wsw the present sedimentological study shows that tephra and volcanogenic sulphate were deposited and preserved within a small surfacedischarging playa that developed on the irregular upper surface of aeolian siltstones of the subjacent white river group sulphate solutions including perhaps sulphuric acid percolated downward within the vadose zone dissolving early formed smectite cement within underlying volcaniclastic sandstones reddening these rocks along an irregular alteration front preserved fine scale stratification within the sandstones precludes the possibility that reddening took place during pedogenesis displacive growth of gypsum at the playa centre folded tephra beds and forced tephra into underlying sandstones forming elongate cones the large mass fraction of gypsum now replaced by calcite in the playa sediments suggests a huge long distance delivery of sulphate aerosols some of the sulphate and tephra may have come from the same eruption or the fine grained tephra may simply have aided preservation of dry fog sulphate derived from an unrelated effusive eruption of lava

deglacial meltwater discharge north atlantic deep circulation and abrupt climate change high resolution paleogeochemical data from the north atlantic ocean indicate that in the interval 15 000 to 10 000 14c years before present b p north atlantic deep water nadw production was decreased or eliminated four times at about 14 500 and probably older 13 500 12 000 and 10 500 years b p each of these changes occurred at the same time as abrupt events of meltwater discharge to the surface ocean inferred from oxygen isotope studies of planktonic foraminifera and from glacial geological studies on land in addition each of these times may be associated with brief episodes of cooler climate in the north atlantic region the best example of which is the younger dryas cooling of 10 500 years ago these results support models linking meltwater discharge decreased nadw production and decreased north atlantic heat flux

quartz as a natural luminescence dosimeter abstract luminescence from quartz is commonly used in retrospective dosimetry in particular for the dating of archaeological materials and sediments from the quaternary period the phenomenon of luminescence is related to the interaction of natural radiation with mineral grains by the activation of and subsequent trapping of electrons at defects within the quartz lattice the latent luminescence signal i e the trapped electrons is released when the grains are exposed to stimulation energy in the form of light or heat despite the fact that quartz is most nominally pure sio2 the mineral forms in several different geological settings i e under different pressure and temperature conditions the luminescence emitted from quartz is complex and shows a variety of different components with diverse physical properties this complexity is explained by the variety of defects in quartz that are either intrinsic e g si and o vacancies or related to impurity atoms e g al or ti the concentration of impurity related defects is dependent on the conditions of mineral formation or subsequent alteration experimental data have shown that the luminescence properties of quartz are highly variable with geological source and vary even at a grain to grain level within a sediment as a consequence caution is needed when making any general statements about the luminescence properties of quartz when using luminescence measurements as a dating technique it is necessary to adjust the measurement procedures for each geological provenance furthermore some quartz has luminescence properties that make it problematic or even unsuitable for certain applications these problems can arise from low and changing luminescence sensitivity thermal transfer of trapped electrons thermal instability of the trapped electrons and low saturation dose reviewing the present knowledge reveals that insufficient information is available either to unambiguously link distinctive lattice defects with characteristic luminescence components or even to explain problems observed in application studies by potential dynamics of the defects within the crystal this paper gives some ideas on how future research could utilise innovative analytical tools to identify or map the distribution of lattice defects and how practitioners could relate lattice defects to measured luminescence properties of quartz

can glacial shearing of sediment reset the signal used for luminescence dating abstract understanding the geomorphology left by waxing and waning of former glaciers and ice sheets during the late quaternary has been the focus of much research this has been hampered by the difficulty in dating such features luminescence has the potential to be applied to glacial sediments but requires signal resetting prior to burial in order to provide accurate ages this paper explores the possibility that rather than relying on light to reset the luminescence signal glacial processes underneath ice might cause resetting experiments were conducted on a ring shear machine set up to replicate subglacial conditions and simulate the shearing that can occur within subglacial sediments luminescence measurement at the single grain level indicates that a number albeit small of zero dosed grains were produced and that these increased in abundance with distance travelled within the shearing zone observed changes in grain shape characteristics with increasing shear distance indicate the presence of localised high pressure grain to grain stresses caused by grain bridges this appears to explain why some grains became zeroed whilst others retained their palaeodose based on the observed experimental trend it is thought that localised grain stress is a viable luminescence resetting mechanism as such relatively short shearing distances might be sufficient to reset a small proportion of the luminescence signal within subglacial sediments dating of previously avoided subglacial sediments may therefore be possible

the δ18o record along the greenland ice core project deep ice core and the problem of possible eemian climatic instability over 70 000 samples from the 3029 m long greenland ice core project grip ice core drilled on the top of the greenland ice sheet summit have been analyzed for 8o a highly detailed and continuous 8o profile has thus been obtained and is discussed in terms of past temperatures in greenland we also discuss a three core stacked annual 8o profile for the past 917 years the short term 50 years variability of the annual 8o signal is found to be 1 in the holocene and estimates for the coldest parts of the last glacial are 3 or higher these data also provide insights into possible disturbances of the stratigraphic layering in the core which seems to be sound down to the onset of the eemian spectral analysis of highly detailed sequences of the profile helps determine the smoothing of the 8o signal which for the holocene ice is found to be considerably stronger than expected we suggest this is due to a process involving diffusion of water molecules along crystal boundaries in the recrystallizing ice matrix deconvolution techniques were employed for restoring with great confidence the highly attenuated annual 8o signal in the holocene we confirm earlier findings of dramatic temperature changes in greenland during the last glacial cycle abrupt and strong climatic shifts are also found within the eem sangamon interglaciation which is normally recorded as a period of warm and stable climate in lower latitudes the stratigraphic continuity of the eemian layers is consequently discussed in section 3 of this paper in terms of all pertinent data which we are not able to reconcile

using strontium isotopes to determine the age and origin of gypsum and anhydrite beds the variation of 87sr 86sr in seawater with time can be used to determine the age of calcium sulfate beds precipitated from brine derived from seawater the determination of a marine origin can be established by the consistency of strontium isotope results from samples at different stratigraphic levels in a single gypsum anhydrite bed collected at separated sites the scatter of strontium isotope results in the gypsum anhydrite samples examined here is interpreted to result from the contribution of meteoric strontium to the salina strontium isotope results from three evaporite settings the jurassic todilto formation from new mexico the permian blaine formation from blaine county oklahoma and the permian salado formation from new mexico are used to determine the age and origin of the parent brine for these gypsum anhydrite beds the calcium sulfate beds from each of these formations precipitated from salinas that originated with a marine flooding but show at different times and localities volume do

caliche as a geological repository for atmospheric sulfate 1 recent studies demonstrate that important information on sulfur source oxidation pathway transport pattern and reaction kinetics of atmospheric oxidation of sulfur gases can be uncovered by measuring multiple isotope compositions of the oxidation product secondary atmospheric sulfate sas sas from earth s distant past however is rarely preserved in the rock records because of its high solubility and small quantity we report here from the measurement of 47 modern and fossil caliche samples that caliches contain variable amounts of carbonate associated sulfate cas and the 17o values of the cas range from 0 12 to 2 32 with most values higher than the background value of 0 05 for seawater sulfate indicating the presence of an sas component derived from the oxidation of sulfur gases by atmospheric ozone or related oxidants this study demonstrates that caliche a pedogenic carbonate common in the geologic record could serve as a repository for ancient sas

holocene eolian activation as a proxy for broad scale landscape change on the gila river indian community arizona abstract eolian sediments are common within the middle gila river valley southern arizona and reflect variability in eolian and fluvial processes during the late holocene this study focuses on deciphering the stratigraphic record of eolian deposition and associated luminescence dating of quartz extracts by single aliquot regeneration sar protocols stratigraphic assessment coupled with luminescence ages indicates that there are four broad eolian depositional events at ca 3145 220 yr 1950 1360 yr 800 100 yr and 690 315 yr this nascent chronology correlated with regional archeological evidence and paleoclimate proxy datasets leads to two general conclusions 1 loess deposits transverse dune formation and sand sheet deposition in the late holocene are probably linked to flow variability of the gila river though the last two events are concordant with regional megadroughts and 2 the stability of eolian landforms since the 19th century reflects the lack of eolian sediment supply during a period of fluvial incision resulting in entisol formation on dunes the prime catalyst of eolian activity during the late holocene is inferred to be sediment supply driven by climate periodicity and variable flow within the gila river catchment

origin of the first global meltwater pulse following the last glacial maximum well dated sea level records show that the glacioeustatic rise following the last glacial maximum was characterized by two or possibly three brief intervals of rapid sea level rise separating periods with much lower rates these very high rates of sea level rise indicate periods of exceptionally rapid deglaciation of remaining ice sheets the laurentide ice sheet is commonly targeted as the source of the first and largest of the meltwater pulses mwp ia between 14 200 12 200 14c years b p and 13 700 years ago 11 700 14c years b p in all oceanic records of deglaciation of the former northern hemisphere ice sheets that we review only those from the gulf of mexico and the bermuda rise show evidence of low 18o values at the time of mwp ia identifying the southern laurentide ice sheet as a potential source for mwp ia we question this source for mwp ia however because 1 ice sheet models suggest that this sector of the ice sheet contributed only a fraction 10 of the sea level needed for mwp ia 2 melting this sector of the ice sheet at the necessary rate to explain mwp ia is physically implausible and 3 ocean models predict a much stronger thermohaline response to the inferred freshwater pulse out of the mississippi river into the north atlantic than is recorded this leaves the antarctic ice sheet as the only other ice sheet capable of delivering enough sea level to explain mwp ia but there are currently no well dated high resolution records to document this hypothesis these conclusions suggest that reconstructions of the laurentide ice sheet in the ice 4g model which are constrained to match the sea level record may be too low for time periods younger than 15 000 years ago furthermore 18o records from the gulf of mexico show variable fluxes of meltwater from the southern margin of the laurentide ice sheet which can be traced to the opening and closing of eastward draining glacial lake outlets associated with surging ice sheet behavior these variable fluxes through eastern outlets were apparently sufficient to affect formation of north atlantic deep water thus underscoring the sensitivity of this process to changes in freshwater forcing

an event stratigraphy for the last termination in the north atlantic region based on the greenland ice core record a proposal by the intimate group it is suggested that the grip greenland ice core should constitute the stratotype for the last termination based on the oxygen isotope signal in that core a new event stratigraphy spanning the time interval from ca 22 0 to 11 5 k grip yr bp ca 19 0 10 0 k 14 c yr bp is proposed for the north atlantic region this covers the period from the last glacial maximum through termination 1 of the deep ocean record to the pleistocene holocene boundary and encompasses the last glacial late glacial of the traditional northwest european stratigraphy the isotopic record for this period is divided into two stadial episodes greenland stadials 1 gs 1 and 2 gs 2 and two interstadial events greenland interstadials 1 gi 1 and 2 gi 2 in addition gi 1 and gs 2 are further subdivided into shorter episodes the event stratigraphy is equally applicable to ice core marine and terrestrial records and is considered to be a more appropriate classificatory scheme than the terrestrially based radiocarbon dated chronostratigraphy that has been used hitherto 1998 john wiley sons ltd

middle holocene mobilization of aeolian sand in western upper michigan and the potential relationship with climate and fire a forested dunefield covers the baraga plains in western upper michigan the ages of five dunes from across the dunefield were determined by optically stimulated luminescence osl employing the single aliquot regenerative dose sar method on quartz grains the results indicate that sand mobilization was restricted to the middle holocene at around 7 ka four environmental variables rapid climatic oscillations fire strong winds and a dry climate are invoked as a combined cause of dune formation this study provides further evidence for the wide extent of aeolian activity in the upper midwest of north america during the middle holocene

primary aerosol sea salt and soil dust deposited in greenland ice during the last climatic cycle comparison with east antarctic records ion chromatography data of ca mg cl and ca and coulter counter particle measurements are used to study the cycle of marine and continental primary aerosol reaching greenland in relation to climatic changes over the last 150 kyr a detailed comparison between greenland dome summit and antarctic vostok records provides new insight on a potential link between northern and southern patterns ca is a good indicator of continental input and is mainly emitted as caco3 an attempt is made to estimate the contribution of aluminosilicates using the concentration of insoluble particles greater than 0 5 m in diameter the relative abundance of non sea salt mg and ca and of aluminosilicate shows that the calcium content of continental background aerosol over greenland was much higher during the glacial age the neutralization capacity of carbonaceous aerosol is estimated the inverse relationship between 18o and continental input as well as the response of this input to the rapid climatic variations that have occurred during the second part of the glacial age are discussed in terms of source and transport modification in relation to the presence and the extent of the great laurentide ice cap the corresponding vostok profiles strongly suggest that some of the phenomena observed at high northern latitudes are of global concern the marine component of na nam is a good tracer of sea salt aerosol similarly to continental input it shows an inverse but more linear relationship with 18o the sensitivity of greenland and antarctic marine input to climate variations of small and large amplitude is compared and a corresponding estimation is made for the aeolian contribution the respective influence of atmospheric circulation and the water vapor cycle is discussed the chlorine to marine sodium weight ratio increases with temperature from values very close to the bulk seawater ratio during the last glacial maximum 18 20 kyr b p to values significantly higher during the holocene and warm eemian the corresponding excess of chloride hcl is discussed in terms of atmospheric transport taking into account the role of atmospheric acidity on sea salt fractionation processes owing to postdepositional phenomena similar vostok data must be considered cautiously nevertheless aerosol fractionation seems to have been much more important over the vostok site except during glacial extrema

reconstruction of holocene foreland progradation using optically stimulated luminescence osl dating an example from dungeness uk roberts helen plater a j 2007 reconstruction of holocene foreland progradation using optically stimulated luminescence osl dating an example from dungeness uk the holocene 17 4 pp 495 505 rae2008

widespread middle holocene dune formation in the eastern upper peninsula of michigan and the relationship to climate and outlet controlled lake level dating of five widely spaced noncoastal dunes in eastern upper michigan by optically stimulated luminescence of quartz establishes that eolian sand was last mobilized between ca 7 and 5 5 ka in the region although this interval corresponds to the drier altithermal hypsithermal period climate alone may not have been sufficiently arid to cause dune formation in this area instead it appears that dune formation may also be linked to depressed water tables associated with outlet controlled low levels in lakes michigan and superior following dune stabilization peat began to accumulate in interdune areas ca 4 4 ka

lateglacial calendar year chronology based on annually laminated sediments from lake meerfelder maar germany abstract annually laminated sediments from lake meerfelder maar mfm in the eifel germany provide an independent calendar year timescale for the last glacial interglacial transition changes in varve thickness and varve facies reflect significant environment variations during this period the general micro facies pattern confirms that diatomaceous organic varves are favoured during warm climatic phases while cold periods generate higher allochthonous sediment fluxes an exception is the significant increase in diatom blooms at the beginning of the younger dryas six lateglacial biozones have been defined by litt and stebich quaternary international 1999 the sediment record comprises two tephra layers as chronomarkers the laacher see tephra 12 880 varve years bp is a continent wide correlation horizon while the ulmener maar tephra provides regional chronological links the beginning of the lateglacial warming is dated at 14 450 varve years vyrs bp which is regarded as the minimum age three abrupt cold spells interrupted the lateglacial interstadial at 13 800 vyrs bp oldest dryas 13 540 vyrs bp older dryas and 12 680 vyrs bp younger dryas the oldest dryas 130 years and the older dryas 190 years were rather short while the younger dryas lasted much longer 1090 years the mfm chronology was compared with ice core timescales from gisp2 and grip there is a good agreement between these timescales with the grip model age ss09 providing the best match to the mfm chronology

a mid european decadal isotope climate record from 15 500 to 5000 years b p oxygen isotope ratios of precipitation delta18op inferred from deep lake ostracods from the ammersee southern germany provide a climate record with decadal resolution the record in detail shows many of the rapid climate shifts seen in central greenland ice cores between 15 000 and 5000 years before the present b p negative excursions in the estimated delta18op from both of these records likely reflect short weakenings of the thermohaline circulation caused by episodic discharges of continental freshwater into the north atlantic deviating millennial scale trends however indicate that climate gradients between europe and greenland changed systematically reflecting a gradual rearrangement of north atlantic circulation during deglaciation

luminescence dating of the wabar meteorite craters saudi arabia 1 luminescence dating has been used to find the age of meteorite impact craters at wabar al hadida in saudi arabia the luminescence characteristics of the shocked material were determined using a variety of luminescence dating techniques applied to impactite formed by the meteorite and to the underlying sand the age is found to be 290 38 years a comparison is made with two possible historically recorded ages an impact as young as this has implications for the assessment of hazards from the impact on earth of small meteorites

archean to recent aeolian sand systems and their sedimentary record current understanding and future prospects the sedimentary record of aeolian sand systems extends from the archean to the quaternary yet current understanding of aeolian sedimentary processes and product remains limited most preserved aeolian successions represent inland sand sea or dunefield erg deposits whereas coastal systems are primarily known from the cenozoic the complexity of aeolian sedimentary processes and facies variability are under represented and excessively simplified in current facies models which are not sufficiently refined to reliably account for the complexity inherent in bedform morphology and migratory behaviour and therefore cannot be used to consistently account for and predict the nature of the preserved sedimentary record in terms of formative processes archean and neoproterozoic aeolian successions remain poorly constrained palaeozoic ergs developed and accumulated in relation to the palaeogeographical location of land masses and desert belts during the triassic widespread desert conditions prevailed across much of europe during the jurassic extensive ergs developed in north america and gave rise to anomalously thick aeolian successions cretaceous aeolian successions are widespread in south america africa asia and locally in europe spain and the usa several eocene to pliocene successions represent the direct precursors to the present day systems quaternary systems include major sand seas ergs in low lattitude and mid latitude arid regions pleistocene carbonate and holocene modern siliciclastic coastal systems the sedimentary record of most modern aeolian systems remains largely unknown the majority of palaeoenvironmental reconstructions of aeolian systems envisage transverse dunes whereas successions representing linear and star dunes remain under recognized research questions that remain to be answered include i what factors control the preservation potential of different types of aeolian bedforms and what are the characteristics of the deposits of different bedform types that can be used for effective reconstruction of original bedform morphology ii what specific set of controlling conditions allow for sustained bedform climb versus episodic sequence accumulation and preservation iii can sophisticated four dimensional models be developed for complex patterns of spatial and temporal transition between different mechanisms of accumulation and preservation and iv is it reasonable to assume that the deposits of preserved aeolian successions necessarily represent an unbiased record of the conditions that prevailed during episodes of earth history when large scale aeolian systems were active or has the evidence to support the existence of other major desert basins been lost for many periods throughout earth history

holocene aeolian sand mobilization vegetation history and human impact on the stabilized sand dune area of the southern nyirseg hungary abstract almost 20 of the territory of hungary is covered by stabilized dunes formed during the pleistocene with the climate amelioration during the early holocene the aeolian activity ceased however various environmental and anthropogenic factors could have reactivated the aeolian processes today there is an increasing climatic stress on the dune fields of the carpathian basin which is coupled with inadequate land use it is therefore necessary to determine the timing and circumstances of sand mobilization during the holocene the site of the present study is located in a dune interdune system on the southern part of the nyirseg alluvial fan where periods of holocene aeolian activity and environmental change were investigated using palynological and sedimentological methods optically stimulated luminescence and radiocarbon dating the data achieved show climate driven boreal aeolian activity at approximately 8 2 ka and also demonstrate for the first time that during the atlantic phase 6 4 and 5 3 ka in spite of the relatively humid climate and dense vegetation aeolian activity has taken place induced probably by agricultural practices following subboreal morphological stability aeolian activity occurred several times in the subatlantic phase 2 4 2 2 1 2 0 8 and 0 4 0 1 ka as a result of vegetation changes and human activity

the response of a dune succession from lencois maranhenses ne brazil to climate changes between mis 3 and mis 2 abstract in tropical southern hemisphere south america late quaternary marine core and speleothem records provide different proxies and accurate chronologies correlating millennial scale intervals of increased precipitation with southward shifts of the intertropical convergence zone itcz however the climatic effect of these intervals on coastal landforms is poorly understood here we investigated the response of abrupt and long lasting climate events during the marine isotope stages 3 and 2 in a 13 8 m thick sand succession located in a large scale coastal eolian system the lencois maranhenses dunefield ne brazil where winds and precipitation are anti phased and controlled by the single action of the itcz a chronology of the sediment overburden determined by optically stimulated luminescence osl dating of 14 sediment samples obtained at 1 m intervals showed ages between 132 2 7 0 and 12 9 0 6 thousand years ago in stratigraphic order a multi proxy approach based on grain size surface grain texture heavy minerals thermoluminescence tl sensitivity inorganic geochemistry reflectance and magnetic parameters from 268 sediment samples collected at 5 cm intervals indicated periods of dune building and stabilization significant stabilization periods are synchronous with heinrich stadials 6 4 3 2 and 1 and greenland stadial 4 within age model uncertainties heavy mineral analysis indicated a steady sand source to the dune succession while tl sensitivity analysis of quartz grains showed the input allochthonous sediments during stadials the preservation of peak dune activity during the last glacial maximum is attributed to the enduring precipitation brought by the subsequent heinrich stadial 1 event

comparison of quartz osl protocols using lateglacial and holocene dune sands from brandenburg germany abstract we present the results obtained using various different protocols in the quartz optically stimulated luminescence dating of a late glacial and holocene aeolian dune sequence near eberswalde north of berlin germany the allerod finow palaeosol and the laacher see tephra layer serve as chronostratigraphic markers and further independent age control is provided by eight 14 c ages the application of the single aliquot regenerative dose protocol using blue light stimulation and the multiple aliquot regenerative dose and additive dose protocols using broad band blue and green light stimulation are discussed a comparison of radionuclide analyses using high resolution gamma spectrometry and neutron activation analysis is also presented it is concluded that the two dosimetry methods give indistinguishable results although the gamma spectrometry data are more precise in contrast the single aliquot regenerative dose protocol is between 2 and 10 times more precise than the multiple aliquot protocols and systematic differences in performance are also observed the uncertainties in the dosimetry calculations are the largest contributor to the overall age uncertainties the accuracy of the resulting ages is considered very satisfactory when tested against the independent age controls over the entire age range from the present to 15 ka

optical dating of holocene sediments from a variety of geomorphic settings using single grains of quartz this paper presents an improved method for the optical dating of holocene sediments from a variety of geomorphic settings we have measured the equivalent dose de in individual grains of quartz using green laser light for optical stimulation and have simulated the de distributions for multiple grain synthetic aliquots using the single grain data for 12 samples of known independent age we show that application of a minimum age model to the single grain and small 10 grain aliquot de data provides the most accurate estimate of the burial dose for nine of the samples examined 3 aeolian 5 fluvial and 1 marine the weighted mean de as obtained using the central age model gives rise to burial age overestimates of up to a factor of 10 for these nine samples whether single grains small aliquots or large 100 grain aliquots are used for the other three samples two aeolian and one fluvial application of either the minimum age model or the central age model to the single grain small aliquot and large aliquot de data yields burial ages in accord with the independent age control we infer that these three samples were well bleached at the time of deposition these results show that heterogeneous bleaching of the optical dating signal is commonplace in nature and that aeolian transport offers no guarantee that the sample will be well bleached at the time of deposition we also show that grains sensitive to infrared ir stimulation can give rise to low de values which will result in significant underestimation of the burial dose and hence of the age of deposition we demonstrate that use of a modified single aliquot regenerative dose protocol incorporating ir stimulation prior to green light stimulation deals effectively with contamination by ir sensitive grains we conclude that application of the modified protocol to single grains or small aliquots of quartz using the lowest de population to estimate the burial dose is the best means of obtaining reliable ages for holocene sediments from a wide range of depositional environments d 2003 elsevier b v all rights reserved

anomalous 17o compositions in massive sulphate deposits on the earth the variation of 18o that results from nearly all physical biological and chemical processes on the earth is approximately twice as large as the variation of 17o this so called mass dependent fractionation is well documented in terrestrial minerals1 2 evidence for mass independent fractionation 17o 17o 0 52 18o where deviation from this tight relationship occurs has so far been found only in meteoritic material and a few terrestrial atmospheric substances3 in the rock record it is thought that oxygen isotopes have followed a mass dependent relationship for at least the past 3 7 billion years ref 4 and no exception to this has been encountered for terrestrial solids5 here however we report oxygen isotope values of two massive sulphate mineral deposits which formed in surface environments on the earth but show large isotopic anomalies 17o up to 4 6 these massive sulphate deposits are gypcretes from the central namib desert and the sulphate bearing miocene volcanic ash beds in north america the source of this isotope anomaly might be related to sulphur oxidation reactions in the atmosphere and therefore enable tracing of such oxidation these findings also support the possibility of a chemical origin of variable isotope anomalies on other planets such as mars6

aeolian alluvial interactions at formentera balearic islands western mediterranean the late pleistocence evolution of a costal system abstract this study deals with the sedimentological and stratigraphic description of pleistocene coastal deposits of formentera island that show evidence of interference between processes characteristic of alluvial and aeolian environments here we analyze the sedimentology and stratigraphy of a pleistocene succession located at northeast of formentera and we constrain its chronology by optically stimulated luminescence osl dating main sedimentary facies representing the succession of aeolian alluvial marine and coastal environments are described in this study we conclude that although there were two prevailing environments such as coastal aeolian and alluvial with different processes and resulting forms the interaction resulted in deposits that share characteristics of both environments as well as maintain elements inherited from each environment in terms of sedimentary supply precipitation runoff or aeolian transport these coastal deposits represent a small alluvial apron covering the base of a vertical cliff most of the sediment that composes these deposits is marine bioclastic sand which was transported in the form of coastal dunes during periods of low sea level our results are a useful indicator of the geomorphological processes and changes that occurred during the pleistocene unraveling the environmental evolution and contributing to the growing knowledge on the western mediterranean aeolian alluvial interacting environments

aeolian sand movement and relative sea level rise in ho bugt western denmark during the little ice age this study documents an extensive aeolian sand sheet buried in the salt marshes of the ho bugt embayment in western denmark the extent of the sand sheet was mapped from c 60 cores and sections which were also used to reconstruct late holocene changes in relative sea level based on diatom analyses chronology was provided by optically stimulated luminescence osl and radiocarbon dating our study shows that since 2000 cal yr bp relative sea level in ho bugt has risen by approximately 1 5 m the overall rise was punctuated by two periods with higher than average rates of sea level rise the first between 2000 and 1400 cal yr bp and the second commencing c 500 cal yr bp around 700 cal yr bp the evolution of the skallingen spit may have been responsible for a reduction in the local tidal range and the formation of an extensive black layer in the western part of the embayment osl analyses date the sand sheet to between ad 1460 40 and ad 1550 30 490 40 and 400 30 cal yr bp consistent wi

sulfate in modern playa settings and in ash beds in hyperarid deserts implication for the origin of 17o anomalous sulfate in an oligocene ash bed abstract a large amount of calcite pseudomorphs after gypsum were discovered in a volcanic ash bed and its underlying sand siltstone in the gering formation late oligocene northwestern ne usa the highly positive 17o anomalies in the residual sulfate indicate that the sulfate could only have come from the oxidation of sulfur gases by ozone in the atmosphere we previously proposed that it was most likely the result of an extreme tropospheric sulfate haze dry fog event that was associated with volcanic eruptions in the west to test the dry fog hypothesis we examine here two alternative scenarios that also involve atmospheric sulfate deposition but do not imply a dramatic volcanic and dry fog source 1 is it possible that some playas in arid or semiarid regions accumulate the type of atmospheric sulfate deposits as we see in the mid gering bed by the inflow of surface water or groundwater 2 could a period of hyperaridity and stability during the late oligocene have caused a significant accumulation of atmospheric background sulfate onto the mid gering ash bed surface sulfates from a variety of playa settings were collected and measured for their 17o anomalies the sulfate isotope both o and s and concentration profiles of two volcanic ash beds that are currently exposed in the central atacama desert chile and in taylor valley of the antarctica dry valleys were studied along with their sedimentary features these two ash beds were chosen for comparison because of their significant levels of atmospheric sulfate accumulated during prolonged and hyperarid climatic conditions results showed no or minimal 17o anomalies in any of the playa sulfate samples from around the world and none of the parameters in the mid gering ash profile matches those in either of the two volcanic ash profiles in modern hyperarid settings conclusion the observed 17o anomalous gypsum deposit in the mid gering ash bed is most likely the result of a series of extreme dry fogs that resulted in an intense pulse of atmospheric sulfate deposition to a semiarid playa setting

dating recent colluvial sequences with 210pb and 137cs along an active fault scarp the eliki fault gulf of corinth greece reliable dating is an essential element of palaeoseismological studies yet whilst a suite of geochronological methods can now provide late quaternary age control it remains very difficult to date modern events i e those occurring within the last 150 years this is significant because the starting point for many palaeoseismological investigations is a modern surface rupturing event whose geological effects need to be disentangled in trench stratigraphies from palaeoseismic ruptures two dating methods which in combination can provide robust dating control in recently deposited sediments are the 210pb and 137cs dating methods here we test the applicability of using 210pb and 137cs to date colluvial sediments exposed in three trenches excavated across an earthquake fault the eliki fault gulf of corinth greece which ruptured in an earthquake in 1861 the 210pb and 137cs profiles observed in these colluvial sequences are relatively erratic due to the mixed nature of the sediments i e their deposition in an environment where the supply of slope sediments is driven by seasonal rainfall causing non uniform sediment accretion and sediment reworking in one trench however 210pb dating corroborated by 137cs dating indicates that a proposed post 1861 surface colluvial unit has been deposited over the period 1950 ad present at a rate of ca 9 mm year and overlies a significantly older unit 120 years old the dating control provided here by 210pb and 137cs dating corroborates the published interpretation of the trench stratigraphy and refines the 14c based estimated dates for the upper unit at two other trenches 210pb and 137cs dating only provided minimum ages based on the presence or absence of 210pbexcess and 137cs such approximate ages however may still useful in corroborating interpretations made using the trench stratigraphy or at sites which have long earthquake recurrence intervals determining which earthquake event was responsible for a particular bed offset

reconstruction of holocene coastal foredune progradation using luminescence dating an example from the świna barrier southern baltic sea nw poland abstract two sandy spits on the wina barrier wolin and uznam provide a very detailed succession of holocene coastal foredunes and dunes and are regarded as key sites along the southern baltic sea coast optically stimulated luminescence osl dating is proven to be a powerful tool for the reconstruction of holocene coastal spit evolution and foredune accretion quartz extracted from the coastal sediments in the study area provides excellent properties for osl dating the osl age from the innermost dune indicates that spit development of the wina barrier started immediately after rapid sea level rise of the littorina transgression decelerated at 6 6 ka a significant change in the foredune progradation rate occurred during the late subatlantic transgression at 1 2 ka 800 ad when migration rates decreased from 2 6 0 7 m a 1 to 1 3 0 4 m a 1 progradation accelerated again during the little ice age between 1550 and 1850 ad the systematic dating of 28 samples reveals six hiatuses during foredune succession at 2100 bc 900 bc 200 bc 200 ad 600 ad 1000 ad and 1600 ad the timing of these hiatuses correlates with the phases of transgressive dune development in the surrounding area troszyn and wina and with phases of increased aeolian activity in other parts of north and west europe we conclude that four of these phases of foredune erosion instability and aeolian sediment mobilisation were caused by general climate shifts to cooler and stormier conditions at 2200 bc 900 bc 600 ad and at 1600 ad the latter corresponding to the little ice age the period of increased aeolian activity around 1000 ad is probably to a phase of intensive forest clearance in central europe in contrast the systematic foredune accretion and foredune plain growth correlates to periods of positive sediment budget milder and calmer climate and an intact vegetation cover

optically stimulated luminescence dates for late pleistocene and holocene sediments from norre lyngby northern jutland denmark quartz from late pleistocene marine and freshwater deposits of known 14c age and from a historically dated aeolian deposit has been studied using multiple aliquot and single aliquot protocols comparisons are presented between equivalent doses derived using a multiple aliquot additive dose thermoluminescence approach and three osl protocols single aliquot regeneration and added dose sara mejdahl and botter jensen 1994 single aliquot additive dose murray et al 1997 and single aliquot regenerative dose murray and roberts 1998 dose rates determined by laboratory gamma spectrometry are compared with both field gamma scintillation measurements and laboratory beta thermoluminescence dosimetry measurements the agreement is satisfactory the resulting dates are discussed in terms of absolute chronology and bleaching environment

extreme monsoon aridity episodes recorded in south china during heinrich events geological records of climate change since the last glaciation in south china a core area of the east asian monsoon are key to understanding secular variation in the monsoon system however with the exception of the speleothems records from this area with independent age control are few we investigated aeolian sand deposition on a sand hill on the shore of poyang lake in south china and reconstructed the chronological sequence of aeolian deposition using optically stimulated luminescence osl dating without exception all aeolian sediments were deposited within seven periods that generally match the timing of heinrich events and other cold periods in greenland we argue that aeolian sand accumulation in this region is most likely forced by extreme aridity driven by weakening of the summer monsoon while the characteristics of this deposition are influenced by winter monsoon intensity the monsoon shifts revealed here suggest a possible link between north atlantic cooling and summer monsoon strength in south china and support the intensities of cooling phases recorded in greenland ice cores

late pleistocene carbonate aeolianites on mallorca western mediterranean a luminescence chronology abstract coastal outcrops of upper pleistocene deposits in north eastern mallorca balearic islands spain have been examined and a chronological framework established using optically stimulated luminescence osl dating the outcrops record a complex interaction between aeolian colluvial and alluvial fan deposition that result in a variable stratigraphical architecture dating and facies analysis make it possible to identify four aeolian activity episodes during mis 5c b 4 and 3 and also add to the understanding of the environmental history of north eastern mallorca over the last 100 ka the new data suggest enhanced aeolian transport and dune formation during cold climatic intervals when sea level was low sediment supply exposed marine carbonate sediment was high winter windiness was high and vegetation on coastal plains at a minimum

testing optically stimulated luminescence dating of sand sized quartz and feldspar from fluvial deposits abstract we apply single aliquot optically stimulated luminescence osl dating to quartz and feldspar rich extracts from fluvial channel deposits of the rhine meuse system in the netherlands the time of deposition of these deposits is tightly constrained by radiocarbon dating or historical sources this allows us to compare osl ages obtained on quartz and infrared osl ir osl ages obtained on potassium rich feldspar with independent ages over the range of 0 3 13 ka we show that the quartz osl ages are in good agreement with the expected age using ir osl dating of feldspar we find a slight age overestimate for the youngest sample whereas for older samples the age is significantly underestimated we also apply osl dating to older fluvial and estuarine channel deposits with limited independent chronological constraints comparison of feldspar ir osl ages with the quartz osl ages up to 200 ka shows a clear trend where the former severely underestimates the latter this trend is similar to that found for the samples with independent age control indicating that the feldspar ir osl ages are erroneously young for the entire age range in the youngest samples incomplete resetting of the ir osl signal prior to deposition probably masks the age underestimation we show that the ir osl age underestimation is partly caused by changes in trapping probability due to preheating correction for this phenomenon improves the ir osl ages slightly but does not provide a complete solution to the discrepancy we suggest that in the light of the problems encountered in the ir osl dating of feldspar quartz is the mineral of choice for osl dating of these deposits however feldspar dating should continue to be investigated because it has potential application to longer time scales

a threshold in soil formation at earth s arid hyperarid transition the soils of the atacama desert in northern chile have long been known to contain large quantities of unusual salts yet the processes that form these soils are not yet fully understood we examined the morphology and geochemistry of soils on post miocene fans and stream terraces along a south to north 27 to 24 s rainfall transect that spans the arid to hyperarid transition 21 to 2 mm rain y 1 landform ages are 2 my based on cosmogenic radionuclide concentrations in surface boulders and ar isotopes in interbedded volcanic ash deposits near the driest site indicate a maximum age of 2 1 my a chemical mass balance analysis that explicitly accounts for atmospheric additions was used to quantify net changes in mass and volume as a function of rainfall in the arid 21 mm rain y 1 soil total mass loss to weathering of silicate alluvium and dust 1030 kg m 2 is offset by net addition of salts 170 kg m 2 the most hyperarid soil has accumulated 830 kg m 2 of atmospheric salts including 260 kg sulfate m 2 and 90 kg chloride m 2 resulting in unusually high volumetric expansion 120 for a soil of this age the composition of both airborne particles and atmospheric deposition in passive traps indicates that the geochemistry of the driest soil reflects accumulated atmospheric influxes coupled with limited in soil chemical transformation and loss long term rates of atmospheric solute addition were derived from the ion inventories in the driest soil divided by the landform age and compared to measured contemporary rates with decreasing rainfall the soil salt inventories increase and the retained salts are both more soluble and present at shallower depths all soils generally exhibit vertical variation in their chemistry suggesting slow and stochastic downward water movement and greater climate variability over the past 2 my than is reflected in recent 100 y rainfall averages the geochemistry of these soils shows that the transition from arid to hyperarid rainfall levels marks a fundamental geochemical threshold in wetter soils the rate and character of chemical weathering results in net mass loss and associated volumetric collapse after 105 to 106 years while continuous accumulation of atmospheric solutes in hyperarid soils over similar timescales results in dramatic volumetric expansion the specific geochemistry of hyperarid soils is a function of atmospheric sources and is expected to vary accordingly at other hyperarid sites this work identifies key processes in hyperarid soil formation that are likely to be independent of location and suggests that analogous processes may occur on mars

quantifying sulfate components and their variations in soils of the mcmurdo dry valleys antarctica 1 many soils of the mcmurdo dry valleys mdv antarctica being old hyperarid and frigid have accumulated abundant atmospheric salts over the last several million years this salt repository offers an opportunity to study atmospheric chemistry past and present the origin and transport of ions in soils the weathering activity of soils and postdepositional soil leaching processes within this unique environment in particular soil sulfate in the mdv is known to have multiple origins but the precise proportions of different sulfate components remain elusive here we test a hypothesis that soil sulfate in the mdv is a predictable mixture of three major components sea salt sulfate non sea salt sulfate and background sulfate derived from weathering and volcanic sources that to a large extent varies as a function of elevation and distance from the coast by measuring sulfate s three stable isotope parameters i e 17o 18o and 34s plus estimating independently the end member stable isotope parameters for the three components on the basis of published reports and our measured data we solve explicitly the mixing proportion for each component using a set of three simultaneous linear equations the results from four spatially representative soil profiles show that the sum of such calculated proportions for the three components is very close to unity in most samples suggesting that a simple three component mixing model is a good representation of the soil sulfate budget while significant uncertainties still exist in the isotope compositions of different sulfate end members these data provide important initial constraints on sulfate diversity as well as its spatial and vertical distribution in the mdv

late glacial climatic oscillations as recorded in swiss lake sediments regional pollen assemblage zones for the late glacial period of the swiss plateau are introduced and defined they include four major zones artemisia juniperus hippophae betula pinus paz with several subzones pollen and oxygen isotope analyses on lacustrine sediments from several lakes in the area reveal four distinct phases of climatic oscillation in the time period of 13 000 9500 yr bp the first oscillation termed the aegelsee fluctuation occurs shortly before 12 000 yr bp and varve counts suggest its duration was ca 100 yr it is characterised by a short decrease in the oxygen isotopes as well as a short increase in nap associated with a depression in birch pollen values the second oscillation which occurs in the 18o record shortly before the deposition of the laacher see tephra ca 11 000 yr bp is termed the gerzensee fluctuation it occurs during a pine dominated phase and its vegetational effects cannot be determined palynologically the most prominent regressive phase is the younger dryas biozone ca 10 700 10 000 yr bp characterised by an increase in heliophilous nap and low 18o values the younger dryas biozone can often be subdivided palynologically into two parts a first part rich in grasses and juniper and a second part with higher filipendula and birch values during the preboreal biozone another distinct oscillation is evidenced only in the oxygen isotope ratios comparison of the swiss oxygen isotope profiles with the greenland dye 3 record suggests that not only the three major shifts in the 18o curves but also the minor ones are closely comparable suggesting some common climatic control

luminescence dating of holocene aeolian sand movement thy denmark abstract we report on the application of optically stimulated luminescence dating to an investigation of the frequency of periods of aeolian sand movement and dune formation on the coast of thy holocene aeolian sediments interleaved with peaty palaeosols form some of the most complete successions known in western denmark samples were taken from a coastal exposure and an inland archaeological site dosimetry was based on laboratory gamma spectrometry and quartz luminescence measurements used the single aliquot regenerative dose protocol and 470 30 nm stimulation the sand samples cover an age ranging from about 100 years to 4500 years the youngest dates give us confidence that the material was well bleached at deposition good agreement was obtained with the radiocarbon palaeosol ages we identify three main periods of aeolian sand movement starting at about 4200 2700 and 900 years ago at least during the latter two periods significant aeolian sand movement occurred all three phases of aeolian activity were separated by long periods of stability and soil formation a more recent episode of dune formation restricted to the coast and beginning less than 200 years ago may have been triggered by modern coastal erosion

variations in chemical composition and particle size of dune sediments along the west coast of jutland denmark abstract geochemical and textural variations in frontal dune sediments along the western coast of jutland denmark have been investigated in order to identify possible sediment provinces and transport pathways an understanding of sediment sources and sinks is important for both for an understanding of the nature of sedimentary environments and for applied coastal engineering and management purposes four coastal sectors were identified on the basis of geochemical composition one sector is compositionally different from the other three units having higher concentrations of the trace elements ni cr v sc zn pb ba zr and many rare earth elements dune sediments on this section of coast also have higher al2o3 to k2o ratios and lower al2o3 to fe2o3 ratios reflecting a lower content of feldspar and higher content of heavy minerals it is inferred that different or additional sediment source s have supplied sediment to this section of coast beach nourishment has contributed to the observed compositional differences but previous data obtained from the lodbjerg area indicate that aeolian sands on this section of coast naturally have a relatively high si fe and ti content reflecting high quartz feldspar ratio and relatively high content of heavy minerals compared with those on other sections of the coast frontal dunes along the most northern section show high abundances of k2o rb and ba reflecting a relatively high k feldspar content derived from local sources alongshore trends were also identified in the mean particle size and sorting of the frontal dunes although there is no direct correspondence with the observed geochemical differences three coastal units can be identified on the basis of particle size frontal dune sediments in the middle section are relatively coarser and less well sorted than those to the north and south probably reflecting both the addition of beach nourishment material and greater exposure to strong westerly winds which are a capable of transporting a wide range of particle sizes the three units defined on this basis do not correlate directly with the units defined on the basis of geochemical composition

formation of aeolian dunes on anholt denmark since ad 1560 a record of deforestation and increased storminess abstract sand dunes on the island of anholt denmark in the middle of kattegat form a relatively barren temperate climate aeolian system locally termed the desert the dunes have developed on top of a raised beach ridge system under the influence of dominant winds from westerly directions they are relatively coarse grained with an average mean grain size of 480 m the last phase of aeolian activity and dune formation on anholt started after ad 1560 when the local pine forest was removed historical sources report intense sand mobilization in the 17th century and new optically stimulated luminescence osl dates indicate that dune formation continued until the end of the 19th century this period of sand drift and dune formation took place during the later part of the little ice age which is characterized by increased summer storminess in large parts of nw europe dune stabilization in the beginning of the 20th century probably records a temporary decrease in storminess ground penetrating radar mapping of the internal structures in two dunes in the western part of the desert a parabolic dune and a linear dune indicates the importance of north westerly storm winds during dune formation

sulfate oxygen 17 anomalies in desert varnishes rock varnishes are ubiquitous in arid regions on earth and are believed to be commonly present on mars here we report high water soluble sulfate and nitrate contents in desert varnishes from the death valley region of southwestern u s a and that sulfate in varnishes possess 17o 18o ratios that do not fall on terrestrial mass dependent fractionation line sulfate from wet and dry atmospheric deposition is probably the source of the 17o anomalies the anomalies are only moderately lower than that of aerosol sulfates collected from the greater los angeles area indicating probably more than half of the sulfate in desert varnish is supplied by atmospheric deposition this finding suggests that earth surface environments are constantly accumulating 17o anomalous sulfate from the atmosphere arid and stable conditions facilitate the preservation of these atmospheric signatures this finding also indicates that different 17o 18o ratios found in different components in the martian meteorites may result from atmospheric chemical processes

the termination of the last major phase of aeolian sand movement coastal dunefields denmark optically stimulated luminescence osl dating of sand samples from stabilized or inactive coastal dunes in denmark provides information on the age of the termination phase of the last major aeolian activity period a total of 26 sand samples were taken from four different coastal dunefields around the north sea skagerrak and kattegat coasts of denmark the osl dates indicate that the last major phase of aeolian activity terminated between ad 1860 and 1905 most of the dunes examined in this study were active around 1820 during a period documented to have been very stormy a dune management scheme started around 1792 and this no doubt was a major cause of dunefield stabilization but an overall decline of storminess particularly spring and summer storminess around the end of the 19th century must also have contributed to the increasing inactivity of coastal dunes the new osl dates on aeolian sand movement agree well with historical data and data from topographic maps on dune movement this agreement supports the observation from earlier work that osl dating of recent aeolian sand movement is accurate over the last few decades to centuries copyright 2005 john wiley sons ltd

sudden changes in north atlantic circulation during the last deglaciation sudden changes in the flow of warm atlantic surface waters into the norwegian sea occurred frequently during the last deglaciation typically involving shifts in sea surface temperature of 5 c in fewer than 40 years these led to equally large and rapid changes in atmospheric temperatures and to shifts in atlantic deep thermo haline circulation and ice sheet melting rates

problems and potential of osl dating weichselian and holocene sediments in sweden recent osl dating of various late quaternary deposits in sweden has resulted in several sets of ages that appear inconsistent with geological interpretation they usually overestimate the expected age we explore the problems and potential of osl dating in sweden by analysing quartz osl ages from several known age sites in sweden and by investigating their luminescence properties two difficulties in obtaining accurate and precise ages are incomplete bleaching and low sensitivity quartz incomplete bleaching can give rise to age overestimation but the importance of this effect can be minimised by selecting suitable sediment facies although for some settings unexplained overestimates still remain low quartz osl sensitivity leads to practical problems in measurements and larger uncertainties in dose estimates but not necessarily to systematic age overestimation sites that contain dala sandstone clasts and or sediments that may have had extensive reworking during the quaternary seem to provide high sensitivity quartz we consider such sites to show the most potential for accurate and precise osl dating in sweden

rare sulfur and triple oxygen isotope geochemistry of volcanogenic sulfate aerosols we present analyses of stable isotopic ratios 17 o 16 o 18 o 16 o 34 s 32 s and 33 s 32 s 36 s 32 s in sulfate leached from volcanic ash of a series of well known large and small volcanic eruptions we consider eruptions of mt st helens washington 1980 1 km 3 mt spurr alaska 1953 1 km3 gjalp iceland 1996 1998 1 km 3 pinatubo phillipines 1991 10 km 3 bishop tuff long valley california 0 76 ma 750 km 3 lower bandelier tuff toledo caldera new mexico 1 61 ma 600 km 3 and lava creek and huckleberry ridge tuffs yellowstone wyoming 0 64 ma 1000 km 3 and 2 04 ma 2500 km 3 respectively this list covers much of the diversity of sizes and the character of silicic volcanic eruptions particular emphasis is paid to the lava creek tuff for which we present wide geographic sample coverage this global dataset spans a significant range in 34 s 18 o and 17 o of sulfate 29 30 and 3 3 respectively with oxygen isotopes recording mass independent 17 o 0 2 and sulfur isotopes exhibiting mass dependent behavior products of large eruptions account for most of these isotopic ranges sulfate with 17 o 0 2 is present as 1 10 m gypsum crystals on distal ash particles and records the isotopic signature of stratospheric photochemical reactions sediments that embed ash layers do not contain sulfate or contain little sulfate with 17 o near 0 suggesting that the observed sulfate in ash is of volcanic origin mass dependent fractionation of sulfur isotopic ratios suggests that sulfate forming reactions did not involve photolysis of so2 like that inferred for pre 2 3 ga sulfates from archean sediments or antarctic ice core sulfate associated with few dated eruptions even though the sulfate sulfur isotopic compositions reflect mass dependent processes the products of caldera forming eruptions display a large 34 s range and exhibit fractionation relationships that do not follow the expected equilibrium slopes of 0 515 and 1 90 for 33 s 32 s vs 34 s 32 s and 36 s 32 s vs 34 s 32 s respectively the data presented here are consistent with modification of a chemical mass dependent fractionation of sulfur isotopes in the volcanic plume by either a kinetic gas phase reaction of volcanic so 2 with oh and or a rayleigh processes involving a residual rayleigh reactant volcanic so 2 gas rather than a rayleigh product these results may also imply at least two removal pathways for so 2 in volcanic plumes above zero 17 o values and their positive correlation with 18 o in sulfate can be explained by oxidation by high 18 o and high 17 o compounds such as ozone and radicals such as oh that result from ozone break down large caldera forming eruptions have the highest 17 o values and the largest range of 18 o which can be explained by stratospheric reaction with ozone derived oh radicals these results suggest that massive eruptions are capable of causing a temporary depletion of the ozone layer such depletion may be many times that of the measured 3 8 depletion following 1991 pinatubo eruption if the amount of sulfur dioxide released scales with the amount of ozone depletion

stretching the envelope of past surface environments neoproterozoic glacial lakes from svalbard the oxygen isotope composition of terrestrial sulfate is affected measurably by many earth surface processes during the neoproterozoic severe snowball glaciations would have had an extreme impact on the biosphere and the atmosphere here we report that sulfate extracted from carbonate lenses within a neoproterozoic glacial diamictite suite from svalbard with an age of similar to 635 million years ago falls well outside the currently known natural range of triple oxygen isotope compositions and indicates that the atmosphere had either an exceptionally high atmospheric carbon dioxide concentration or an utterly unfamiliar oxygen cycle during deposition of the diamictites

middle to late pleistocene dunefields in rocky coast settings at cala xuclar eivissa western mediterranean recognition architecture and luminescence chronology abstract this study focuses on cliff front anchored and sand ramp aeolian dune accumulations in cala xuclar eivissa ibiza western mediterranean during different sea level falling stages from middle to late pleistocene times stratigraphic mapping conventional lithostratigraphic logging and osl datings are used to reconstruct dune formation and evolution facies analyses result in the identification of six sedimentary units three of which correspond to dune deposits formed at mis 6 145 ka mis 5d c 100 ka and mis 4 77 73 ka respectively additionally there is a beach deposit at 2 m above present msl which resembles the mis 5a this study concludes that each dune system corresponds to a relatively low sea level stand that exposed enormous amounts of marine carbonate sands that was transported inland by migrating dunes under strong north westerly winds therefore sea level fall and the related sediment supply owe likely to be key factors in the formation of these aeolianites systems

continental biogenic species in the greenland ice core project ice core tracing back the biomass history of the north american continent ammonium nitrate and organic acid records from the greenland ice core project deep ice core are discussed all species have a continental biogenic source that is situated predominantly on the north american continent for species deposited in summit central greenland the record therefore can be used to trace back the biomass history of the north american continent difficulty in the interpretation of these records arises from their unknown transfer behavior in a more alkaline atmosphere which characterizes glacial time periods compared to interglacial stadials this may have implications not only for weak acids such as formate and acetate but also possibly for the transport and incorporation of hno3 into aerosols whereas ammonium is probably not affected by the alkalinity change of the atmosphere our approach is to compare samples with similar h concentrations throughout the record from the records we infer several significant fluctuations in the extent of the laurentide ice sheet during the last glaciation we find evidence against the occurrence of an extensive younger dryas event in north america

reconstruction of the holocene coastal development at fulong beach in north eastern taiwan using optically stimulated luminescence osl dating abstract the fulong beach coastal area represents a unique feature in taiwan comprising a beach only a few kilometres long and dominated by medium and fine grained quartz rich sand located in the estuary of shuangsi river the area is influenced by fluvial marine and aeolian processes which led to the development of coastal parallel dune ridges and a large sand complex to the south of the river during the holocene the island of taiwan is also influenced by tectonic activity with high uplift rates and a substantial number of earthquakes each year furthermore the subtropical climate and the occurrence of monsoon precipitation as well as typhoon events induce high erosion rates in the coastal zone seventeen samples from five sites were taken for grain size analyses and for optically stimulated luminescence osl dating post ir pulsed blue osl signals were measured to determine the depositional ages of the samples a chronological model of holocene coastal evolution of fulong beach and the main controlling factors was established sediment accumulation at fulong beach was initiated around 5130 360 a under sub aquatic conditions followed by beach deposition at around 3450 240 a the deposition of aeolian sediments started at around 3020 180 a and was interrupted by three depositional hiatuses during which palaeosols formed the dune ridges yielded osl ages between 60 20 and 690 70 a which indicate stabilisation of the morphological system of fulong beach only a few hundred years ago based on the new data the holocene uplift rate is 1 9 mm y for the last 3000 years at fulong beach incorporating the effects of holocene sea level fluctuations

the origin and spread of grass dominated ecosystems in the late tertiary of north america preliminary results concerning the evolution of hypsodonty abstract sediment samples were collected in northwestern nebraska from the following lithologic units 1 the upper oligocene monroe creek formation the lower miocene harrison formation and upper harrison beds of the arikaree group and 2 the lower miocene runningwater formation and the dawes clay member box butte formation of the ogallala group the samples were processed using heavy liquid extraction and analyzed for siliceous plant microfossils phytoliths all samples yielded well preserved and diverse assemblages dominated by grass phytoliths but included phytoliths produced by woody and herbaceous dicotyledons palms and sedges the abundance of woody dicotyledons and palms decreased up section the grass assemblages consisted mainly of festucoid c3 phytolith morphotypes an index assessing the amount of tree cover d p the ratio of dicotyledon phytoliths to grass phytoliths was employed to interpret the data according to this analysis there was open c3 dominated grassland in the study area between 25 and 17 ma at least 7 ma before supposed adaptations to grasslands in ungulates hypsodonty originate

middle pleistocene to holocene coastal evolution of nw sardinia mediterranean sea italy abstract the middle pleistocene holocene sardinian stratigraphy has been revised to identify the roles played by sea and climate changes in controlling sedimentation the succession dated through optically stimulated luminescence quartz k feldspar and 14 c the most recent was grouped into eight major stratigraphic units mainly represented by coastal dunes shallow marine and alluvial systems these units range in age from mis 8 300 ka to mis1 6 ka little information is available for the period between mis 8 and 6 the available data however allow some comments on climate changes over the last 125 ka the last interglacial mis 5 is subdivided into five substages e a mis5e eemian is considered the climate optimum of this interglacial sea level was 4 6 m higher than today and climate conditions were warmer and more humid mis 5c is the second high stand peak sea level was about 1 5 m above the modern level and paleoclimatic and paleogeographic conditions were similar to the present during mis 4 at the beginning of the glacial phase a climatic deterioration occurred temperatures dropped by 6c relative to mis 5e in about 5 ka and sea level fell about 60 m this led to a progressive disruption of inland vegetation cover and to repeated valley slope denudation the sea level fall created the accommodation space for fan development in sheltered and cliffed areas where debris flows developed and filled almost completely the terminal parts of the narrow coastal valleys coves in wider areas however coastal dune fields developed contemporaneous presence of alluvial fan and dune systems is associated with the local morphology that could mitigate or amplify moist conditions within a generally arid environment during mis 3 several climate fluctuations occurred wet arid d o h events however the shallow sardinian shelf was continuously sufficiently exposed to become the source area of bioclastic sands these sands were blown inland and formed extensive dunefield systems dunes dominated the west coasts of sardinia under cold and relatively dry conditions in some areas these dunefield systems were eventually almost completely dismantled and reworked into water flow dominated alluvial fans by catastrophic rainfall events thus the local climate quickly switched from arid to humid conditions no record of the last glacial maximum deposits mis 2 was observed along the nw sardinian coast during the holocene transgression mis1 coastal dune systems developed and progressively migrated inland and temperature rose to reach the present day condition

bio and chronostratigraphy of the lateglacial in the eifel region germany abstract in recent years enormous success has been achieved in varve counting of the eifel maar lakes but a detailed correlation with the biostratigraphy has been missing in this paper we present new palynological results of the lateglacial sequences from holzmaar lake and meerfelder maar lake based on annually laminated sediments in particular the meerfelder maar has great potential because in contrast to the holzmaar the sequence between the ulmener maar tephra 11 000 varve years bp and the laacher see tephra 12 880 varve years bp including the younger dryas is undisturbed and complete therefore we currently use the meerfelder maar chronology brauer et al 1999b as an independent varve calendar for the biostratigraphy of the lateglacial the palynological signals of both maar lakes are in good agreement and can easily be correlated with one another and with type sections type regions in northwestern germany and jutland the sequences of the eifel maar lakes have the quality of hypostratotypes with regional biozones based on an absolute time scale

optical dating of young coastal dunes on a decadal time scale we explore the use of quartz optically stimulated luminescence osl dating for reconstructing coastal evolution on a time scale of decades to a few hundred years samples are taken from the accretionary south west coast of texel a barrier island just offshore of the northern netherlands the ages of dune ridges are known from historical sources an excellent chronology with a decadal accuracy exists for the past 260 years osl ages of less than 10 years on the youngest samples indicate that the osl signal of the quartz grains is very well zeroed prior to deposition and burial osl ages of five samples from a 250 year old dune ridge are indistinguishable and the osl ages on 17 out of 20 samples are in excellent agreement with the well known independent age controls our results highlight the potential of osl dating for high resolution reconstruction of coastal evolution over the past few centuries

photonic dating of holocene back barrier coastal dunes northern north carolina usa abstract we have made the first application of luminescence sediment dating methods to coastal dunes from the barrier island system in north carolina as part of a larger study of the timing of activation and stabilization of coastal dunes of northern north carolina and southern virginia that employed ground penetrating radar trenching 14c dating and analysis of soils we applied photonic dating to seven samples from four sites jockeys ridge nags head woods penney hill and run hill we used fine sand sized potassium feldspar from the four samples with sufficient feldspar concentrations and quartz from all samples we applied the multi aliquot infrared stimulated luminescence thermal transfer correction additive dose add and the late light subtraction add methods to the feldspars we applied the single aliquot regenerative dose sar method with 470 nm stimulation to the quartz feldspar thermal transfer age estimates from 5 46 a year to 823 56 a 1 o are typically

absolute dating of the late glacial period in switzerland using annually laminated sediments abstract results of a high resolution late glacial ams 14 c chronology from rotsee central switzerland have given evidence that the atmospheric radiocarbon concentration was not constant between 13 000 and 9500 yr b p this resulted in three marked phases of constant radiocarbon age at 12 700 at 10 000 and at 9500 yr b p new results of a late glacial varve chronology from soppensee central switzerland suggest that the younger two phases of constant 14 c age each had a duration of ca 400 calendar years the length of the late glacial chronozones has been calculated on the basis of these replicate varve counts and a comparison with their estimated duration in radiocarbon years shows that the estimated duration of the chronozones bolling ca 800 calendar yr vs 1000 14 c yr and younger dryas ca 900 calendar yr vs 1000 14 c yr agree with the expected time span whereas the estimated duration of the allerod chronozone ca 400 calendar yr vs 1000 14 c yr is substantially shorter than expected furthermore a tentative comparison of varve ages and 14 c ages suggests that the varve chronology is more than 1000 yr offset toward older ages from the radiocarbon chronology during the late glacial period

land ice teleconnections of cold climatic periods during the last glacial interglacial transition independent calendar year chronologies are a basic requirement for the establishment of high resolution land ice teleconnections the annually laminated meerfelder maar record provides both an independent chronology established by varve counting and high resolution lithological proxy data for the period of the last glacial interglacial transition these data reveal a series of four periods of climatic deterioration coinciding with negative isotopic deviations in the grip record signal thus demonstrating the synchronicity of environment changes in western germany and temperature shifts in greenland the terrestrial data supports a further sub division of the event stratigraphy based on the grip core by introducing the cold event gi 1c2 between 13 500 and 13 400 calendar years bp multiproxy analyses reveal that the environmental response at meerfelder maar was not linear throughout the lateglacial but was modified by local processes a change in the response of the lake environment to climate deterioration was observed during sub stage gi 1b gerzensee oscillation the only event with gradual rather than abrupt transitions the two fold character of the younger dryas as seen in the grip record is more pronounced in the meerfelder maar record this lithological signal occurred with a delay of 60 years to the grip signal and has been linked to a shift in the catchment it is proposed that the trigger for this shift was a trend towards a more humid second half of the younger dryas

deglacial changes in ocean circulation from an extended radiocarbon calibration temporal variations in the atmospheric concentration of radiocarbon sometimes result in radiocarbon based age estimates of biogenic material that do not agree with true calendar age this problem is particularly severe beyond the limit of the high resolution radiocarbon calibration based on tree ring data which stretches back only to1 2 about 11 8 kyr before present bp near the termination of the younger dryas cold period if a wide range of palaeoclimate records are to be exploited for better understanding the rates and patterns of environmental change during the last deglaciation extending the well calibrated radiocarbon timescale back further in time is crucial several studies attempting such an extension using uranium thorium dated corals3 4 5 and laminae counts in varved sediments6 7 8 9 show conflicting results here we use radiocarbon data from varved sediments in the cariaco basin in the southern caribbean sea to construct an accurate and continuous radiocarbon calibration for the period 9 to 14 5 kyr bp nearly 3 000 years beyond the tree ring based calibration a simple model compared to the calculated atmospheric radiocarbon concentration and palaeoclimate data from the same sediment core suggests that north atlantic deep water formation shut down during the younger dryas period but was gradually replaced by an alternative mode of convection possibly via the formation of north atlantic intermediate water

the origin of gypsum in vertisols in new caledonia determined by isotopic characteristics of sulphur abstract gypsum crystals occur in vertisols on the west coast of new caledonia these soils are derived from the weathering of basic rocks that contain no gypsum the sulphur isotopic ratio 34 s 32 s was used as tracer to identify the origin of the gypsum a total of 26 measurements of 34 s were made on gypsum crystals from the vertisols and compared to those of continental sulphates and to marine gypsum in tidal flats the 34 s value of the crystals located in new caledonian vertisols decreases with increasing distance from the coast this suggests that the gypsum in the vertisols comes from two sources an oceanic source where the major part of the sulphur is introduced by atmospheric precipitation and a continental source where sulphides disseminated in various subsurface deposits are oxidized gypsum from atmospheric precipitation penetrates the vertisols through vertical cracks that probably formed in dry seasons during the last glacial period

sand deposition during the last millennium at aberffraw anglesey north wales as determined by osl dating of quartz abstract ground penetrating radar gpr was used to identify sediment units at the terminus of a small dune field at aberffraw nine samples were taken from boreholes sample locations were based on the stratigraphy established by gpr quartz grains were dated using a single aliquot regenerative dose protocol that allows for sensitivity changes sand deposition at llyn coron aberffraw occurred three times in the last 700 years with initial sand movement occurring around 1331 ad when historical documents record sand being mobilised in a strong storm

high resolution lacustrine record of the late glacial holocene transition in central europe abstract in this paper we present the high resolution record of proxy climatic data in central europe during the final stages of the last deglaciation derived from the annually laminated sediments of lake go ciaz central poland the isotopic palynological and other microfossil data confirm sudden changes of climate at the onset and termination of the younger dryas completed within 150 and 70 years respectively in close agreement with the previous estimates derived from the polar ice cores and marine sediments in the upper yd some amelioration of climate took place already about 600 years before the main yd preboreal transition counting of annual varves in the lake sediments allows a direct estimate of the duration of the younger sdryas in central europe it lasted approximately 1640 years substantially longer than suggested by previous estimates derived from laminated lake sediments and glacial varves but agreeing with the radiocarbon calibration data obtained for barbados corals the calendar ages of the boundaries of the yd 12 920 and 11 280 cal bp are tentatively set

a late amazonian alteration layer related to local volcanism on mars hydrated minerals on mars are most commonly found in ancient terrains dating to the first billion years of the planet s evolution here we discuss the identification of a hydrated light toned rock unit present in one chasma of the noctis labyrinthus region stratigraphy and topography show that this alteration layer is part of a thin unit that drapes pre existing bedrock crism spectral data show that the unit contains hydrated minerals indicative of aqueous alteration potential minerals include sulfates such as bassanite caso4 1 2h2o or possibly hydrated chloride salts the proximity of a smooth volcanic plain and the similar crater model age late amazonian 100 myr of this plain and the draping deposits suggest that the alteration layer may be formed by the interaction of water with ash layers deposited during this geologically recent volcanic activity the alteration phases may have formed due to the presence of snow in contact with hot ash or eventually solid gas interactions due to the volcanic activity the relatively young age of the volcanic plain implies that recent alteration processes have occurred on mars in relation with volcanic activity but such local processes do not require conditions different than the current climate

the atmospheric winter circulation during the younger dryas stadial in the atlantic european sector the younger dryas yd stadial signified an interruption of the warming during the transition from the last glacial to the present interglacial the mechanism responsible for this cooling is still uncertain so valuable information concerning climate variability can be obtained by numerical simulation of the yd climate we performed four experiments on the younger dryas climate with the hamburg atmospheric general circulation model here we use the results of these experiments which differed in prescribed boundary conditions to characterize the atmospheric winter circulation during the yd stadial in the north atlantic european sector the 10 year means of the following variables are presented sea level pressure 500 hpa geopotential heights and 200 hpa winds in addition we used daily values to calculate an index to assess the occurrence of blocking and strong zonal flow and to compute storm tracks our results show that the yd cooling in europe was present with a strong and stable westerly circulation without blocking this is in conflict with an earlier study suggesting frequent easterly winds over nw europe in our experiments the sea ice cover in the north atlantic ocean was the crucial factor forcing this specific yd circulation moreover the jet stream over the north atlantic was strengthened considerably causing an enhanced cyclonic activity over the eurasian continent the yd winter circulation was different from the circulation found in most simulation studies on the last glacial maximum since no glacial anticyclones were present and no split of the jet stream occurred

extremely acid permian lakes and ground waters in north america evaporites hosted by red beds red shales and sandstones some 275 265 million years old extend over a large area of the north american mid continent1 they were deposited in non marine saline lakes pans and mud flats2 settings that are typically assumed to have been alkaline here we use laser raman microprobe analyses of fluid inclusions trapped in halites from these permian deposits to argue for the existence of highly acidic ph 1 lakes and ground waters these extremely acidic systems may have extended over an area of 200 000 km2 modern analogues of such systems may be natural acid lake and groundwater systems ph 2 4 in southern australia3 4 5 6 7 8 9 both the ancient and modern acid systems are characterized by closed drainage arid climate low acid neutralizing capacity and the oxidation of minerals such as pyrite to generate acidity the discovery of widespread ancient acid lake and groundwater systems demands a re evaluation of reconstructions of surface conditions of the past and further investigations of the geochemistry and ecology of acid systems in general

non biological fractionation of stable ca isotopes in soils of the atacama desert chile abstract we measured ca stable isotope ratios 44 40 ca in an ancient 2 my hyperarid soil where the primary source of mobile ca is atmospheric deposition most of the ca in the upper meter of this soil 3 5 kmol m 2 is present as sulfates 2 5 kmol m 2 and to a lesser extent carbonates 0 4 kmol m 2 in aqueous extracts of variably hydrated calcium sulfate minerals 44 40 ca e values vs bulk earth increase with depth 1 4 m from a minimum of 1 91 to a maximum of 0 59 the trend in carbonate 44 40 ca in the top six horizons resembles that of sulfate 44 40 ca but with values 0 1 0 6 higher the range of observed ca isotope values in this soil is about half that of 44 40 ca values observed on earth linear correlation among 44 40 ca 34 s and 18 o values indicates either a a simultaneous change in atmospheric input values for all three elements over time or b isotopic fractionation of all three elements during downward transport we present evidence that the latter is the primary cause of the isotopic variation that we observe sulfate 34 s values are positively correlated with sulfate 18 o values r 2 0 78 and negatively correlated with sulfate 44 40 ca e values r 2 0 70 if constant fractionation and conservation of mass with downward transport are assumed these relationships indicate a 44 40 ca fractionation factor of 0 4 in caso 4 the overall depth trend in ca isotopes is reproduced by a model of isotopic fractionation during downward ca transport that considers small and infrequent but regularly recurring rainfall events near surface low ca isotope values are reproduced by a rayleigh model derived from measured ca concentrations and the ca fractionation factor predicted by the relationship with s isotopes this indicates that the primary mechanism of stable isotope fractionation in caso 4 is incremental and effectively irreversible removal of an isotopically enriched dissolved phase by downward transport during small rainfall events

late quaternary eolian sand depositional record for southwestern kansas landscape sensitivity to droughts abstract eolian deposits and landforms are ubiquitous in western kansas particularly south of the arkansas river with the presence of a stabilized dune field stratigraphic studies and associated optical dating reveal a complex depositional history for this dune field spanning the late quaternary the oldest eolian deposits from ca 16 to 12 ka completely or partially bury high terraces with ages of ca 16 and 33 ka it is unknown whether these eolian deposits reflect regional aridity and or a change in sediment availability with the transition of the arkansas river from a single channel to a braided system there is pervasive evidence for episodic eolian erosion and deposition ca 9 8 to 6 3 ka generally coincident with loess deposition on upland surfaces olson c g nettleton w d porter d a brasher b r 1997 middle holocene aeolian activity on the high plains of west central kansas holocene 7 3 255 261 and thus it is inferred to reflect regional aridity sites within the dune field show a sequence of eolian sands and weak buried soils reflecting either dune migration or sand sheet accretion at ca 1490 430 380 320 180 and 70 yr ago which correspond well with continental scale droughts in the tree ring record eolian sand in the arkansas river dune field may be derived principally with variability in fluvial activity and in climate during the late pleistocene to the middle holocene with substantial reactivation of eolian systems during decadal scale drought variability in the past 2000 yr

different sulfate sources and their post depositional migration in atacama soils abstract sulfate is one of the major salts accumulated in the hyperarid atacama desert chile its origin has been attributed to local weathering volcanic source sea salt and atmosphere deposition previous studies concluded that atmospheric sulfate is present in the desert but this term was poorly defined in terms of chemical origin and its contribution to the total sulfate budget in soil is debated the contribution of each potential sulfate source is expected to vary geographically due to different source locations efforts to quantify the contribution from each source have been hampered by the lack of well defined isotopic compositions for its end members in this study we discard the vague term of atmospheric sulfate by recognizing two major sulfate sources on the basis of their formation pathways primary and secondary sulfate primary sulfate including those from rock weathering sea salt and volcanic ash leachates do not have an 17o anomaly secondary sulfate derived from the oxidation of reduced sulfur gases biological or volcanic emissions by atmospheric ozone or hydrogen peroxide however has an 17o anomaly we developed a method to extract water soluble anions sequentially or entirely from bulk soil samples and analyzed the sulfate concentrations and 17o anomalies for four geographically representative soil profiles in the central atacama desert 23 s to 25 5 s we found that sequential sulfate extractions on the same soil sample produce sulfate with decreasing 17o values except for a positive bulge at 20 to 50 cm in depth there is a general increase in the 17o value for total sulfate with soil depth for all the four soil profiles that we examined these findings are consistent with the hypothesis that secondary sulfates 17o anomalous sulfates are more soluble and thus preferentially leached in liquid water than primary sulfate the finding also warns that incomplete sulfate extraction from sulfate rich soils yields unpredictable results we infer a 17o value of 4 6 for secondary sulfate based on data from partial sulfate extraction experiments total contribution of secondary sulfate in the central atacama desert is estimated to range from 9 to 24 with the highest percentage in the central depression

optically stimulated luminescence dating of young sediments a review optically stimulated luminescence osl dating of young 1000 years sediments is used increasingly in a wide variety of late holocene studies as a mean of establishing contemporary sedimentation rates or the timing of sediment deposition this paper provides a summary of the basic principles of osl dating outlines the problems specific to the dating of young material and then uses recent applications to young sediments to illustrate the greatly increased scope and potential of the method in geomorphology and the geology of recent deposits the overall reliability of this new generation of osl ages is examined by comparing where possible osl ages with independent age control it is concluded that the osl ages are accurate in that there is no evidence for systematic over or under estimation it is our conclusion that osl dating should be regarded as a reliable chronological tool for determining the time of deposition of water lain sediments from the coastal zone and aeolian deposits from both coastal and inland environments our conclusion is supported by the growing popularity of osl dating in geomorphology and geology

high resolution sediment and vegetation responses to younger dryas climate change in varved lake sediments from meerfelder maar germany abstract this work focuses on a 1900 year section of varved sediments from lake meerfelder maar mfm extending from the late allerod to the preboreal varve counting provides the chronological framework and determines the length of younger dryas to 1025 1090 years a strong relation between climate change environment response and depositional processes has been found in consequence varve microfacies variations are a sensitive proxy for environment changes these are reflected for example in erosion processes within the lake s catchment minerogenic input and lake productivity diatom blooms the observed varve changes have been quantified by multiproxy analyses of physical and chemical sediment parameters with a resolution of between 8 and 40 years depending on sedimentation rate in addition high resolution palynological investigations provide the biostratigraphical subdivision based on changes in the vegetation occurring during the same time interval varve observations reveal that environment changes at the beginning and the end of the younger dryas occurred within 20 50 years furthermore sediment and vegetation changes were synchronous within the actual precision of the mfm and grip chronologies divergence of only a few decades terrestrial responses in western europe occurred quasi synchronous to temperature changes in greenland

more than ten million years of hyper aridity recorded in the atacama gravels abstract the atacama desert s hyper aridity is closely linked to the development of world class copper and nitrate iodine ores and to regional tectonics and global paleoclimate changes in the cenozoic era the timing when the hyper aridity commenced remains controversial with proposed ages ranging from late oligocene to pleistocene in this study we provide an independent constraint on the initiation of atacama hyper aridity utilizing a 100 m deep profile within the atacama gravels and underneath porphyry copper deposit in spence northern chile the overall high concentration of sulfate up to 10 wt and a multimodal distribution of water soluble salt sulfates chlorides and nitrates indicate multiple generations of sedimentation and salt accumulation events under semi arid to hyper arid climate conditions the multiple sulfate isotope compositions 17o 18o 34s of the upper section 15 0 to 34 5 m are close to those of modern hyperarid surface sulfates while the lower section 34 5 to 65 m displays a depth dependent isotope trend that is best interpreted as marking a period of climate change from semi arid to hyper arid when these data are combined with new chronological 40ar 39ar dates obtained from a volcanic ash layer at depth of 28 0 m our results show that hyper arid condition in the atacama desert was prevailing at least prior to 9 47 ma and may go back as old as the middle miocene

a strontium and sulfur isotopic study of permo triassic evaporites in the northern calcareous alps austria pervasively deformed permian and to a lesser extent triassic evaporites of the northern calcareous alps form a tectonic melange collectively known as alpine haselgebirge isotopic compositions of s and sr and trace element concentrations of sr and ba in ca sulfate minerals were investigated in terms of their stratigraphic and paleoenvironmental significance the majority of the samples yielded 34s values ranging from 9 8 to 13 8 indicating precipitation from late permian seawater with local modifications due to bacterial sulfate reduction bsr 87sr86sr ratios of these samples range widely from 0 7070 to 0 7098 but most samples show sr isotope values between 0 7070 and 0 7074 overlapping with the accepted late permian seawater values comparison of both s and sr isotopic compositions of individual samples reveals distinct trends of isotopic enrichment and depletion that can be linked to early diagenetic bsr mixing with continental surface or groundwaters and burial diagenesis concentrations of sr tend to be lower and ba values show a tendency toward values higher than those reported from marine evaporites implying variable diagenetic alteration triassic evaporites are volumetrically less important in the haselgebirge than their permian counterparts and are characterized by marine upper scythian to lower anisian s and sr isotope values in three localities hitherto unknown inclusions of these triassic evaporites were identified within the haselgebirge melange

mass independent isotopic signatures of volcanic sulfate from three supereruption ash deposits in lake tecopa california abstract hundreds to thousands of megatons of sulfur dioxide released by supereruptions can change chemical and physical properties of the atmosphere and thus induce climate perturbations we present oxygen and sulfur isotope analyses of sulfate in 48 volcanic ash samples and 26 sediment samples from dry lake beds in the tecopa basin california usa these ash layers represent three supereruptions including the 0 64 ma lava creek tuff 2 04 ma huckleberry ridge tuff and 0 76 ma bishop tuff mass independent oxygen signatures 17o up to 2 26 that are present in these ash units and not in associated sediments indicate oxidation of volcanic so2 by mass independent ozone and its products in this study we consider the formation deposition preservation and dilution of mass independent volcanic sulfate mivs using the isotopic compositions of the sulfates we construct a mixing model that demonstrates that the main source of sulfate in lake tecopa is mass dependent sediment derived sulfate mdsds 77 however ash beds still preserve up to 23 of mivs that initially had undiluted 17o value around 8 and 33s as low as 0 35 and 36s up to 1 08 therefore despite potential dilution by mdsds the mivs signatures can be preserved in the geologic record for few million years if deposited as gypsum in arid environments alkaline or saline lake the oxygen and sulfur mass independent signatures of the volcanic sulfates indicate that photolysis and oxidation of volcanic so2 has been achieved in the upper atmosphere since only supervolcanic eruptions were shown to generate massive amount of mass independent sulfate it requires that up to 20 60 of the global ozone layer is consumed as a result of supervolcanic so2 released this may occur as a result of a strong physical and chemical degradation of the tropopause we speculate that the distinction between the high troposphere and the low stratosphere at least locally could be erased by supereruptions and recorded by mivs