early hydrothermal carbon uptake by the upper oceanic crust insight from in situ u pb dating it is widely thought that continental chemical weathering provides the key feedback that prevents large fluctuations in atmospheric co2 and hence surface temperature on geological time scales however low temperature alteration of the upper oceanic crust in off axis hydrothermal systems provides an alternative feedback mechanism testing the latter hypothesis requires understanding the timing of carbonate mineral formation within the oceanic crust here we report the first radiometric age determinations for calcite formed in the upper oceanic crust in eight locations globally via in situ u pb laser ablation inductively coupled plasma mass spectrometry analysis carbonate formation occurs soon after crustal accretion indicating that changes in global environmental conditions will be recorded in changing alteration characteristics of the upper oceanic crust this adds support to the interpretation that large differences between the hydrothermal carbonate content of late mesozoic and late cenozoic oceanic crust record changes in global environmental conditions in turn this supports a model in which alteration of the upper oceanic crust in off axis hydrothermal systems plays an important role in controlling ocean chemistry and the long term carbon cycle

calcite u pb age of the cretaceous vertebrate bearing bayn shire formation in the eastern gobi desert of mongolia usefulness of caliche for age determination

the upper end of the uk 37 temperature calibration revisited 1 being able to decipher paleo sea surface temperatures for warm oceanic waters is of the utmost importance to further evaluate the role of the tropics in global climate change the uk 37 index is one of such paleothermometers although the warm range of temperatures often poses serious analytical challenges this paper discusses and reviews several important aspects of the uk 37 index calibration for waters warmer than 26 27 c amongst them insights into the possible existence of a limit above which the uk 37 index is not able to accurately record temperature variations are presented some warnings are also given on the misleading practice and expected consequences of reporting uk 37 index values of unity in the cases when abundances of the minor triunsaturated alkenone below detection limit are encountered future directions toward an improved knowledge of the behaviour of the uk 37 calibration for warm waters are suggested

synergies in elemental mobility during weathering of tetrahedrite cu fe zn 12 sb as 4s13 field observations electron microscopy isotopes of cu c o radiometric dating and water geochemistry abstract tetrahedrite cu fe zn 12 sb as 4s13 is commonly present in many ore deposits and may be transferred to mining waste here we describe the behavior of all elements in tetrahedrite during oxidative dissolution in a natural oxidation zone at piesky slovakia this being a long term analogue of weathering of tetrahedrite rich mining wastes electron microprobe work identified initial early advanced and mature stages of weathering the initial stages include formation of secondary covellite and chalcocite the following stages only oxidic products divided into greenish masses and brown veinlets both of them are nanocrystalline mixtures of minerals the masses are cu sb as rich and consist of a nanocrystalline pyrochlore phase the veinlets are fe sb as rich and contain tripuhyite goethite and pyrochlores quantitative elemental budgets show that some elements zn s ni co are rapidly lost whereas others especially cu and as are retained and form copper arsenates in the mature stages of weathering about 10 as and almost 50 of sb are lost during weathering likely released into water some sb is stored in secondary minerals such as camerolaite cualstibite or tripuhyite light carbon isotopic composition 13c down to 11 1 document significant biological contribution for c in the secondary minerals copper isotopes become progressively heavier during weathering from initial 65cu of 2 45 in tetrahedrite up to 4 3 in some azurite samples but 6 3 in covellite and chalcocite documenting cyclic removal of light copper isotopes into covellite and chalcocite the observation of elemental synergies during weathering of tetrahedrite shows that the solubility and mobility of as is controlled by copper arsenates not by iron oxides in an environment rich in tetrahedrite but poor in pyrite antimony another element of environmental concern is mostly released into water and creates low concentration anomalies in stream sediments and soils

an experimental study of strontium and lead diffusion in calcite and implications for carbonate diagenesis and metamorphism chemical diffusion of pb and sr has been measured in natural calcite under anhydrous conditions the source of diffusants for the sr and pb diffusion experiments were srco3 and pbo powders respectively experiments were run in sealed silica capsules containing finely ground calcite to ensure stability of the single crystal samples during diffusion anneals rutherford backscattering spectroscopy rbs was used to measure diffusion profiles the following arrhenius relations were obtained over the temperature range 440 800 c for sr 440 650 for pb dsr 2 1 x 10 13exp 132 6 kj mol 1 rt m2 s 1 dpb 5 8 x 10 15exp 117 9 kj mol 1 rt m2 s 1 diffusion of sr and pb is relatively rapid in comparison to rates for these elements in other minerals but fine scale zoning and isotopic and chemical signatures many be retained in calcites under many conditions if diffusion is the dominant process affecting alteration

a 500 000 year record of indian summer monsoon dynamics recorded by eastern equatorial indian ocean upper water column structure the indian summer monsoon ism is an inter hemispheric and highly variable oceaneatmosphere eland interaction that directly affects the densely populated indian subcontinent here we present new records of palaeoceanographic variability that span the last 500 000 years from the eastern equatorial indian ocean a relatively under sampled area of ism influence we have generated carbon and oxygen stable isotope records from three foraminiferal species from ocean drilling program site 758 5 n 90 e to investigate the oceanographic history of this region we interpret our resultant dd 18 o surface thermocline record of upper water column stratification in the context of past ism variability and compare orbital phase relationships in our site 758 data to other climate and monsoon proxies in the region results suggest that upper water column stratification at site 758 which is dominated by variance at precession and half precession frequencies 23 19 and 11 ka is forced by both local 5 n insolation and ism winds in the precession 23 ka band stratification minima at site 758 lag northern hemisphere summer insolation maxima precession minima by 9 ka which is consistent with arabian sea ism phase estimates and suggests a common wind forcing in both regions this phase implicates a strong sensitivity to both ice volume and southern hemisphere insolation forcing via latent heat export from the southern subtropical indian ocean additionally we find evidence of possible overprinting of millennial scale events during glacial terminations in our stratification record which suggests an influence of remote abrupt climate events on ism dynamics

u pb geochronology of calcite mineralized faults absolute timing of rift related fault events on the northeast atlantic margin constraining the timing of brittle faulting is critical in understanding crustal deformation and fluid flow but many regional scale fault systems lack readily available techniques to provide absolute chronological information calcite mineralization occurs in crustal faults in many geological settings and can be suitable for u pb geochronology this application has remained underutilized because traditional bulk dissolution techniques require uncommonly high u concentration because u and pb are distributed heterogeneously throughout calcite crystals high spatial resolution sampling techniques can target domains with high u and variable u pb ratios here we present a novel application of in situ laser ablation inductively coupled plasma mass spectrometry la icp ms to basaltic fault rock geochronology in the faroe islands northeast atlantic margin faults that are kinematically linked to deformation associated with continental break up were targeted acquired ages for fault events range from mid eocene to mid miocene and are therefore consistently younger than the regional early eocene onset of ocean spreading highlighting protracted brittle deformation within the newly developed continental margin calcite geochronology from la icp ms u pb analysis represents an important and novel method to constrain the absolute timing of fault and fluid flow events

vein calcite dating reveals pyrenean orogen as cause of paleogene deformation in southern england an improved method of u pb dating of vein calcite formed during deformation is used to determine the age and cause of folding along the south coast of england fractures arising from folding of late cretaceous chalk of southern england occurred 34 7 1 7 myr ago underlying jurassic strata have veins within fractures with ages of 55 48 42 39 37 34 31 and 25 ma with 34 31 ma being the tectonic culmination folding was slightly younger than the age of the youngest strata in the overlying solent group suggesting that folding terminated basin sedimentation this age of north south shortening is inconsistent with attribution to intraplate forces from the mainly younger alps but is plausibly a result of the pyrenean orogen which evolved from 50 to 28 myr ago with a late eocene culmination a modified method for carbonate laser ablation inductively coupled plasma mass spectrometry u pb dating is presented that uses measured 232 th and 208 pb as a better monitor of common pb and it has distinct advantages over existing methods initial common lead determined on samples conforms closely to model compositions calculated by earlier workers with free regressions giving the most robust dates the modified method is applicable to structural geology carbonate diagenesis and to dating of carbonate relevant to palaeo environmental and archaeological studies supplementary material details of sample locations and characteristics photographs of sample localities microscopic images of veins details of the experimental procedure and u pb data for all samples and reference materials are available at https doi org 10 6084 m9 figshare c 3997086

derivation of isotope ratios errors and error correlations for u pb geochronology using 205pb 235u 233u spiked isotope dilution thermal ionization mass spectrometric data a comprehensive treatment of the derivation of u pb isotope ratios and their corresponding uncertainties from isotope dilution thermal ionization mass spectrometric measurements is presented standard parametric statistical methods of error propagation are utilized to convolve uncertainties associated with instrumental mass fractionation tracer subtraction blank pb and u subtraction and initial common pb correction derivations include errors and error correlations for total sample u pb and pb isotope ratios including radiogenic and initial common pb for two and three dimensional isochron calculations radiogenic u pb and pb isotope ratios for concordia and radiogenic model age calculations and the propagation of model age errors from radiogenic isotope ratios

an optimized scheme of lettered marine isotope substages for the last 1 0 million years and the climatostratigraphic nature of isotope stages and substages a complete and optimized scheme of lettered marine isotope substages spanning the last 1 0 million years is proposed lettered substages for marine isotope stage mis 5 were explicitly defined by shackleton 1969 but analogous substages before or after mis 5 have not been coherently defined short term discrete events in the isotopic record were defined in the 1980s and given decimal style numbers rather than letters but unlike substages they were neither intended nor suited to identify contiguous intervals of time substages for time outside mis 5 have been lettered or in some cases numbered piecemeal and with conflicting designations we therefore propose a system of lettered substages that is complete without missing substages and optimized to match previous published usage to the maximum extent possible our goal is to provide order and unity to a taxonomy and nomenclature that has developed ad hoc and somewhat chaotically over the decades our system is defined relative to the lr04 stack of marine benthic oxygen isotope records and thus it is grounded in a continuous record responsive largely to changes in ice volume that are inherently global this system is intended specifically for marine oxygen isotope stages but it has relevance also for oxygen isotope stages recognized in time series of non marine oxygen isotope data and more generally for climatic stages which are recognized in time series of non isotopic as well as isotopic data the terms stage and substage in this context are best considered to represent climatostratigraphic units and thus climatic stages and climatic substages because they are recognized from geochemical and sedimentary responses to climate change that may not have been synchronous at global scale

temperature and salinity effects on alkenone ratios measured in surface sediments from the indian ocean abstract we compare alkenone unsaturation ratios measured on recent sediments from the indian ocean 20 n 45 s with modern sea oceanographic parameters for each of the core sites we estimated average seasonal cycles of sea surface temperature sst and salinity which we then weighted with the seasonal productivity cycle derived from chlorophyll satellite imagery the unsaturation index u37k ranges from 0 2 to 1 and correlates with water temperature but not with salinity theu37k versus sst relationship for indian ocean sediments u37k 0 033 sst 0 05 is similar to what has been observed for core tops from the pacific and atlantic oceans and the black sea a global compilation for core tops givesu37k 0 031 t 0 084 r 0 98 which is close to a previously reported calibration based on particulate organic matter from the water column for temperatures between 24 and 29 c however the slope seems to decrease to about 0 02u37k unit c for indian ocean core tops the ratios of total c37alkenones total c38alkenones and the slope of theu37k sst relationship are similar to those previously observed for cultures ofemiliania huxleyibut different from those previously published forgephyrocapsa oceanica eithere huxleyiis a major producer of alkenones in the indian ocean or strains ofg oceanicaliving in the northern indian ocean behave differently from the one cultured in contrast with coccolithophorid assemblages the ratios of c37alkenones to total c38alkenones lack clear geographic pattern in the indian ocean

tilting uplift volcanism and disintegration of the south german block abstract we present a large set of fault slip data together with six u pb ages on calcite vein fillings constraining the kinematics and timing of near surface uppermost 2 3 km of crust faulting of the uplifted south german block in the northern foreland of the nw ward advancing alps the structural data confirm earlier studies showing miocene subhorizontal ne directed extension with shortening mainly being subvertical but also subhorizontally nw oriented the u pb ages are between 15 3 0 2 and 2 3 1 1 ma 2 analytical uncertainty and date kinematically coordinated normal and strike slip faulting in the northern alpine foreland the faults in the south german block have limited strike lengths indicating that they do not cut deeply into the crust however the faults appear to control volcanic centers the melts of which originated at the base of the lithosphere we suggest that the miocene faults could tap the mantle because they reactivated formerly deep seated faults the ages for near surface faulting are coeval with eruption of the urach and hegau volcanics published data suggest that alpine shortening induced large wavelength lithospheric folding in the foreland since 18 16 ma volcanism in the south german block focussed along a lithospheric antiform which is in part superimposed on the foreland bulge of the alps we propose a close link between progressive southward tilting uplift and faulting of the south german block due to lithospheric scale folding and upward flow of the asthenosphere flexure of the lithosphere deep seated volcanism and the nw ward advancing alps

la icp ms u pb geochronology and clumped isotope constraints on the formation and evolution of an ancient dolomite reservoir the middle permian of northwest sichuan basin sw china abstract recent advances in laser ablation inductively coupled plasma mass spectrometry la icp ms in situ u pb radiometric dating and clumped isotope thermometry 47 of carbonate minerals provide potential for refining the fluid flow and diagenetic history of carbonate successions in this study the middle permian dolomites proximal to the longmenshan fold and thrust belt in northwest sichuan basin southwest china were investigated using combined u pb geochronology clumped isotope thermometry and routine isotopic 13c 18o and 87sr 86sr and elemental geochemistry in an attempt to reveal the possible relevance of carbonate diagenesis and porosity evolution to the basin scale tectonic fluid flow events in the framework of absolute time overall formation and evolution of these dolomites temporally correlated well with major tectonic episodes of the longmenshan fold and thrust belt contrary to the previously assumed volcanic related model u pb dating and 47 analyses suggest a mid to late triassic replacive dolomitization event u pb ages of 240 12 ma to 233 8 6 4 ma by a hot 47 temperatures 88 104 c basinal brine which was likely driven by thrust related compression of the longmenshan fold and thrust belt during the triassic replacive dolomitization was immediately followed by cementation of euhedral dolomites u pb age of 228 10 ma and blocky calcites u pb ages of 224 8 1 8 ma to 213 4 3 3 ma precipitated from the basinal brine in the same tectonic regime afterwards there was long term cessation of diagenesis that was coincident with and thus may well be attributed to tectono thermal quiescence during most of the mesozoic era and paleogene finally saddle dolomite cements yield miocene ages u pb ages of 16 40 0 74 ma to 12 3 1 2 ma and precipitated in pre existing vugs representing a hydrothermal fluid flow event 47 temperatures up to 170 c during the reactivation of thrusting in addition similarities in u pb ages and geochemical signatures between host rocks replacive dolomites and the vug lining dolomite cements suggest that most porosity in these dolomite reservoirs was inherited from the precursor limestones which probably experienced meteoric leaching during late permian uplift this study highlights that there are geodynamic controls on fluid flow and consequent diagenetic evolution of carbonates in tectonically active sedimentary basins it illustrates that burial alone in this setting is not a sufficient driver for diagenetic alteration and porosity reduction the combination of u pb radiometric dating clumped isotope thermometry and routine geochemical analyses is a useful approach in refining the diagenetic and porosity evolution history of ancient carbonate successions

tropical sea surface temperatures during the last glacial period a view based on alkenones in indian ocean sediments abstract the quantification of tropical temperatures during the last glacial cycle 0 150 kyr bp is a controversial issue since different proxies seem to provide conflicting informations to obtain a complementary point of view we use the alkenone method to estimate sea surface temperatures and focus our work on deep sea sediments recovered from the tropical indian ocean we present alkenone data obtained in two cores which cover in detail the last deglaciation and in about twenty cores distributed between 20 s and 20 n that were chosen to evaluate the temperature contrast of the last glacial interglacial transition our results indicate that indian ocean tropical temperatures remained an average within 1 5 2 5 c of their present values during the last glaciation at 10 n the last deglaciation is characterized by two warming steps which is similar to the classical deglacial chronology observed in the north atlantic area at 20 s the deglacial warming occurred at ca 15 cal kyr bp lagging significantly 5 4 kyr behind the antarctic warming but in phase with northern hemisphere time series

the precession phase of the boreal summer monsoon as viewed from the eastern mediterranean odp site 968 the astronomical timescale of the eastern mediterranean plio pleistocene builds on tuning of sapropel layers to northern hemisphere summer insolation maxima a 3000 year precession lag has become instrumental in the tuning procedure as radiocarbon dating revealed that the midpoint of the youngest sapropel s1 in the early holocene occurred approximately 3000 years after the insolation maximum the origin of the time lag remains elusive however because sapropels are generally linked to maximum african monsoon intensities and transient climate modeling results indicate an in phase behavior of the african monsoon relative to precession forcing here we present new high resolution records of bulk sediment geochemistry and benthic foraminiferal oxygen isotopes from odp site 968 in the eastern mediterranean we show that the 3000 year precession time lag of the sapropel midpoints is consistent with 1 the global marine isotope chronology 2 maximum monsoonal precipitation conditions in the mediterranean region and china derived from radiometrically dated speleothem records and 3 maximum atmospheric methane concentrations in antarctica ice cores we show that the time lag relates to the occurrence of precession paced north atlantic cold events which systematically delayed the onset of strong boreal summer monsoon intensity our findings may also explain a non stationary behavior of the african monsoon over the past 3 million years due to more frequent and intensive cold events in the late pleistocene

clumped isotope palaeothermometry and la icp ms u pb dating of lava pile hydrothermal calcite veins calcite veins are a common product of hydrothermal fluid circulation clumped isotope palaeothermometry is a promising technique for fingerprinting the temperature of hydrothermal fluids but clumped isotope systematics can be reset at temperatures of ca 100 c to model whether the reconstructed temperatures represent calcite precipitation or closed system resetting the precipitation age must be known la icp ms u pb dating of calcite is a recently developed approach to direct dating of calcite and can provide precipitation ages for modelling clumped isotope systematics in calcite veins in this study clumped isotope and la icp ms u pb calcite analyses were combined in basalt hosted calcite veins from three settings in scotland samples from all three localities yielded precipitation temperatures of ca 75 115 c from clumped isotope analysis but veins from only two of the sites were dateable yielding precipitation ages of 224 8 ma and 291 33 ma 2 modelling from the dated samples enabled confident interpretation that no closed system resetting had occurred in these samples however the lack of a precipitation age from the third location meant that a range of possible thermal histories had to be modelled meaning that confidence that resetting had not occurred was lower this highlights the importance of coupling clumped isotope thermometry and la icp ms u pb calcite dating in determining the temperature of hydrothermal fluids recorded in calcite veins this paired approach is shown to be robust in constraining the timing and precipitation temperature of calcite formation and thus for tracking hydrothermal processes

seismic stratigraphy and depositional signatures of the maldive carbonate system indian ocean abstract as documented by industrial seismic reflection profiles and well data the cenozoic stratigraphic evolution of the maldive carbonate system shows three distinct intervals characterized by their own specific depositional signatures late palaeocene volcanics generated by the reunion hotspot filled deeper pull apart structures and created a flat topography that promoted the onset of the maldive carbonate system in the early eocene some of the initial structural depressions remained as deep internal seaways surrounded by reefal margins until the late oligocene the eocene early oligocene stratigraphic signature is essentially aggradational and corresponds to a transgressive cycle associated with a second order sea level rise in the mid oligocene a major sea level fall exposed the neritic carbonate system and restricted sedimentation to the former deep internal basins during the next transgression a neritic carbonate system re established itself on the newly flooded platform and was finally drowned near the oligocene miocene boundary the main effect of this second order transgressive cycle was the transformation of the central troughs into one single deep basin in the neogene the palaeo maldive inner sea when a reef framework was established in the early miocene near the present location of the platform edge systematic bank margin progradation toward the central inner sea basin became enhanced this neogene progradational phase is explained as the response to a long term sea level fall associated with a second order regressive cycle finally the late pliocene pleistocene depositional signature is mainly aggradational and corresponds to the regional modification from flat topped carbonate banks to atoll physiographies the antecedent karst theory suggests that increased karstification was triggered by high frequency eustatic and climatic changes in the last 3 0 ma

the monsoon imprint during the atypical mis 13 as seen through north and equatorial indian ocean records previous studies have suggested that marine isotope stage mis 13 recognized as atypical in many paleoclimate records is marked by the development of anomalously strong summer monsoons in the northern tropical areas to test this hypothesis we performed a multi proxy study on three marine records from the tropical indian ocean in order to reconstruct and analyse changes in the summer indian monsoon winds and precipitations during mis 13 our data confirm the existence of a low salinity event during mis 13 in the equatorial indian ocean but we argue that this event should not be considered as atypical taking only into account a smaller precession does not make it possible to explain such precipitation episode however when considering also the larger obliquity in a more complete orbitally driven monsoon model one can successfully explain this event in addition our data suggest that intense summer monsoon winds although not atypical in strength prevailed during mis 13 in the western arabian sea these strong monsoon winds transporting important moisture together with the effect of insolation and eurasian ice sheet are likely one of the factors responsible for the intense monsoon precipitation signal recorded in china loess as suggested by model simulations

interglacial hydroclimate in the tropical west pacific through the late pleistocene records of atmospheric carbon dioxide concentration pco 2 and antarctic temperature have revealed an intriguing change in the magnitude of interglacial warmth and pco 2 at around 430 000 years ago 430 ka but the global climate repercussions of this change remain elusive here we present a stalagmite based reconstruction of tropical west pacific hydroclimate from 570 to 210 ka the results suggest similar regional precipitation amounts across the four interglacials contained in the record implying that tropical hydroclimate was insensitive to interglacial differences in pco 2 and high latitude temperature in contrast during glacial terminations drying in the tropical west pacific accompanied cooling events in northern high latitudes therefore the tropical convective heat engine can either stabilize or amplify global climate change depending on the nature of the climate forcing

evolution of the eastern tropical pacific through plio pleistocene glaciation a tropical pacific climate state resembling that of a permanent el nino is hypothesized to have ended as a result of a reorganization of the ocean heat budget 3 million years ago a time when large ice sheets appeared in the high latitudes of the northern hemisphere we report a high resolution alkenone reconstruction of conditions in the heart of the eastern equatorial pacific eep cold tongue that reflects the combined influences of changes in the equatorial thermocline the properties of the thermocline s source waters atmospheric greenhouse gas content and orbital variations on sea surface temperature sst and biological productivity over the past 5 million years our data indicate that the intensification of northern hemisphere glaciation 3 million years ago did not interrupt an almost monotonic cooling of the eep during the plio pleistocene sst and productivity in the eastern tropical pacific varied in phase with global ice volume changes at a dominant 41 000 year obliquity frequency throughout this time changes in the southern hemisphere most likely modulated most of the changes observed

temporal and spatial relations between large scale fault systems evidence from the sinai negev shear zone and the dead sea fault abstract in the major zones of crustal deformation within the arabia sinai nubia plates the interactions between the sinai negev shear zone snsz and the dead sea fault system dsf shed light on the interplay between neighboring large scale fault systems the snsz is composed of several e w to ene wsw trending mainly normal and dextral strike slip faults that are tens to hundreds of kilometers long these faults form a 120 km wide shear zone in the sinai sub plate on reaching the plate bounding dead sea fault system dsf individual lineaments of the snsz are observed in the arabian plate offset left laterally by 105 km which is the total estimated offset of the dsf in this contribution we review the geologic setting of the snsz and its complex relations with the dsf in light of newly obtained age strain analyses for this we use in situ u pb geochronology in conjunction with twin analysis of syn faulting calcite from both systems the results indicate that the deformation along the snsz initiated in the campanian maastrichtian or earlier as the oldest dates are 73 71 ma the main phase of fault activity began in the late oligocene early miocene 27 22 ma as documented by numerous dates that were obtained along several lineaments of the snsz the activity continued until 10 ma after which no direct ages have been obtained the dominant phase of activity along the snsz at 27 22 ma preceded the timing of initiation of lateral faulting along the dsf at 20 18 ma by a few myr for the overlapping period of activity between 20 and 10 ma episodes of fault activity along the snsz followed by episodes of fault activity along the dsf moreover dominant episodes of activity along one fault system were associated with a decrease in activity along the other system the temporal relations between the snsz and dsf highlight the possibility that these fault systems are mechanically interrelated but the exact mechanism for this fault interaction needs further study we consider the paleo strain or paleo stress that control the evolution and style of the snsz and assess them at the central sinai negev region during the cenozoic we show that the formation of new plate boundaries at the region i e the red sea suez rift and the dsf affected the strain field within the snsz the proximity of the two systems indicates that the dsf related stress originated within the snsz and possibly caused structural and style changes in the latter system syn faulting calcite twins analyses within the snsz show pronounced spatial and temporal variations of the principal strain directions between and along individual faults this observation demonstrates that the imposed stress within the central sinai negev were not uniform over time the high angle 70o between the traces of the snsz and the direction of the dsf related maximum shortening likely suppressed the dextral motion along the snsz post 20 ma field evidence u pb dates and recent seismicity shows that the current snsz is a long lived structure that has been active during the miocene alongside the dominantly dsf and may still be sporadically active today

late stage anhydrite gypsum siderite dolomite calcite assemblages record the transition from a deep to a shallow hydrothermal system in the schwarzwald mining district sw germany abstract the majority of hydrothermal vein systems of economic interest occur at relatively shallow crustal levels although many of them formed at significantly greater depths their present position is a consequence of uplift and erosion although many aspects of their formation are well constrained the temporal chemical evolution of such systems during uplift and erosion is still poorly understood these vein minerals comprise calcite dolomite ankerite siderite magnesite anhydrite and gypsum forming the last gangue assemblages in jurassic and tertiary sulphide fluorite quartz barite veins of the schwarzwald mining district sw germany mineral textures of samples from nine localities reveal that in these sequences mineral precipitation follows a recurring pattern early calcite is followed by anhydrite or gypsum siderite and or dolomite this succession may repeat up to three times in situ la icp ms u pb age dating of 15 carbonates from three subsequent generations of the late stage vein assemblage yield robust ages between 20 and 0 6 ma each mineral sequence forms in a distinctive period of about 2 5 ma these ages clearly relate these late stage mineral phases to the youngest geological episode of the schwarzwald which is associated with the cenozoic rhine graben rifting and basement uplift based on thermodynamic modelling the formation of the observed mineral assemblages required an deeply sourced mg fe and so4 rich fluid b which was episodically mixed with a shallow crustal hco3 rich fluid a as a consequence of fluid mixing concentrations of mg fe and so4 temporarily increased and initiated the formation of the observed sulphate carbonate mineral sequences this discontinuous large scale vertical fluid mixing was presumably directly related to episodes of active tectonics associated with the cenozoic strike slip regime of the upper rhine graben analogously episodic fluid mixing is a major key in the formation of older jurassic to early tertiary pb zn fluorite quartz barite assemblages in the same specific vein systems albeit involving different fluid compositions late stage hydrothermal 20 70 c vein assemblages reported in this study record the transition from deep 2 km to very shallow 0 1 km crustal conditions as a consequence of successive uplift increasing proportions of shallower and cooler 50 70 c fluids could take part in such mixing processes associated changes in the fluid composition caused the vein mineralogy to change from sulphide quartz fluorite barite to calcite anhydrite gypsum siderite dolomite as the system passively ascended closer to the surface

atmospheric hydrospheric mechanisms of climate anomalies in the western equatorial indian ocean atmosphere ocean mechanisms of rainfall anomalies at the coast of eastern africa are studied using long term ship observations in the indian ocean surface current measurements subsurface casts upper air analyses by the european centre for medium range weather forecasts rain gauge series in eastern africa and india and an index of the southern oscillation so the high so phase being defined by anomalously high low pressure at tahiti darwin the causalities of precipitation anomalies at the coast of eastern africa differ for the two rainy seasons centered on april may and october november and only the latter is strongly related to the so in the high so phase april may pressure is low over the entire indian ocean domain whereas in october november pressure is high in the west and low in the east concomitantly surface waters are anomalously cold in the west and strong westerlies sweep the equatorial zone of the indian ocean eastern african rainfall anomalies are related to the so through a combination of cooperative mechanisms that function most effectively in the boreal autumn rainy season of eastern africa 1 equatorial westerly winds are conducive to lower tropospheric divergence over equatorial east africa and in the high so phase these are accelerated especially in october november owing to the anomalous eastward pressure gradient 2 the equatorial westerly winds drive the eastward equatorial jet in the upper hydrosphere which entails cold water upwelling in the western extremity of the basin where sea surface temperature further hydrostatically affects the zonal pressure gradient and thus feeds back into the equatorial westerly winds 3 in addition cold water anomalies in the western indian ocean most pronounced in october november during the high so phase also suppress convection 4 in the high so phase the indian summer monsoon tends to be strong leaving behind an anomalously cold western indian ocean which in turn feeds into mechanisms 1 to 3 the eastward equatorial jet thus has a role to play in feedback mechanisms contributing to the anomalies of the boreal autumn rains at the coast of eastern africa

sea surface temperature and productivity records for the past 240 kyr in the arabian sea abstract deep sea sediments of two cores from the western ty93 929 p and the southeastern md900963 arabian sea were used to study the variations of the indian monsoon during previous climatic cycles core ty93 929 p was located between the sw monsoon driven upwelling centres off somalia and oman which are characterized by large seasonal sea surface temperature sst and particle flux changes by contrast core md900963 was situated near the maldives platform an equatorial ocean site with a rather small sst seasonality less than 2 c for both cores we have reconstructed sst variations by means of the unsaturation ratio of c37 alkenones which is compared with the 18o records established on planktonic foraminifera in general the sst records follow the 18o variations with an sst maximum during oxygen isotope stage 5 5 the last interglacial at about 120 130 kyr and a broad sst minimum during isotope stage 4 and 3 3 approximately 40 50 kyr the sst difference between the holocene and the last glacial maximum lgm is of the order of 2 c in both cores the ssts during isotope stage 6 are distinctly higher by 1 2 c than the cold sst minima during the last glacial cycle lgm and stage 3 to reconstruct qualitatively the past productivity variations for the two cores we used the concentrations and fluxes of alkenones and organic carbon together with a productivity index based on coccolith species florisphaera profunda relative abundance within each core there is a general agreement between the different palaeoproductivity proxies in the southeastern arabian sea core md900963 glacial stages correspond to relatively high productivity whereas warm interstadials coincide with low productivity all time series of productivity proxies are dominated by a cyclicity of about 21 23 kyr which corresponds to the insolation precessional cycle a hypothesis could be that the ne monsoon winds were stronger during the glacial stages which induced deepening of the surface mixed layer and injection of nutrients to the euphotic zone by contrast the records are more complicated in the upwelling region of the western arabian sea core ty93 929 p this is partly due to large changes in the sedimentation rates which were higher during specific periods isotope stages 6 5 4 5 2 3 and 2 unlike core md900963 no simple relationship emerges from the comparison between the 18o stratigraphy and productivity records the greater complexity observed for core ty93 929 p could be the result of the superimposition of different patterns of productivity fluctuations for the two monsoon seasons the sw monsoon being enhanced during interglacial periods whereas the ne monsoon was increased during glacial intervals a similar line of reasoning also could help explain the sst records by the superimposition of variations of three components global atmospheric temperature and sw and ne monsoon dynamics

a calcite reference material for la icp ms u pb geochronology u pb dating of calcite is an emerging but rapidly growing field of application in geochronology with great potential to inform problems in landscape basin and mountain belt evolution through age determination of diagenetic cements vein mineralisation and geological formations difficult to date otherwise in this brief we present isotope dilution u pb isotope measurements on a sample of calcite wc 1 that has been and will continue to be used as a reference material for in situ u pb laser ablation inductively coupled plasma mass spectrometry la icp ms dating and which is suitable to be distributed to the geochronological community we present in situ measurements using la icp ms to demonstrate the suitability of wc 1 for use as a u pb dating reference material in spite of it not being isotopically homogeneous the wc 1 calcite sample is 254 4 6 4 ma old and comprised of 85 to 98 radiogenic lead it presents a suitable reference material that can facilitate dating of calcite ranging in age from precambrian to late neogene age

beyond 500ka progress and prospects in the upb chronology of speleothems and their application to studies in palaeoclimate human evolution biodiversity and tectonics abstract this review summarises current research aimed at extending the chronology and thus scientific utility of speleothems beyond the 500 ka limit previously imposed by conventional u th dating methods the u pb decay scheme is familiar to all geoscientists but its application to speleothems is a relatively recent development and one set to revolutionise their use in studies of climate change human evolution and migration biodiversity tectonics and landscape evolution technological advances such as the introduction of multi collector icpms instruments have played a key role in this breakthrough and multiple inter laboratory and inter method comparisons provide evidence that the methodology is now mature and that the ages obtained are robust some impediments remain in particular with respect to corrections for initial isotopic disequilibrium younger samples and the construction of internal chronologies older samples but these are areas of intense research activity and are likely to see significant advances in the near future the coupling of speleothem u pb dating with other nascent technologies offering the prospect of precise palaeotemperature estimation is an exciting development in palaeoclimate science while u pb chronologies of archaeological sites are producing important new insights into human evolution although less well developed at this point the methodology appears equally well suited and significant for future studies of past faunal change and landscape evolution

u pb dating of calcite in ancient carbonates for age estimates of syn to post depositional processes a case study from the upper ediacaran strata of finnmark arctic norway results of in situ u pb dating of calcite spherulites cone in cone cic calcite and calcite fibres from a calcareous concretion of the upper ediacaran of finnmark arctic norway are reported ca

tectonic evolution of the northern oman mountains part of the strait of hormuz syntaxis new structural and paleothermal analyses and u pb dating of synkinematic calcite

from hydroplastic to brittle deformation controls on fluid flow in fold and thrust belts insights from the lower pedraforca thrust sheet se pyrenees abstract we present a multidisciplinary study to decipher the controls of deformation on fluid flow regime in fold and thrust belts using the lower pedraforca thrust sheet in the se pyrenees as an example we integrate field based and petrographic observations and geochemical and geochronological data to differentiate seven types of fractures eight types of calcite cement cc1 to cc8 and two sets of stylolites during the deformation stretching the studied thrust sheet during syn sedimentary hydroplastic normal faulting affecting poorly consolidated upper cretaceous and eocene syn orogenic sediments calcite cement did not precipitate during burial bed parallel stylolites formed and cc1 and cc2 precipitated from formation waters in a closed palaeohydrological system during the layer parallel shortening cc3 precipitated from formation waters 5 4 vsmow with 87sr 86sr ratios of 0 707922 and at 70 c cc4 precipitated from formation waters recording different burial conditions as the up to 4 dispersion in 18o of this cement suggests contrarily during folding and thrusting cc5 to cc7 precipitated in an open palaeohydrological system cc6 precipitated from formation waters 5 vsmow with 87sr 86sr ratios of 0 707817 and at 75 c these fluids carried hydrocarbons and probably interacted with upper triassic evaporites an 87sr 86sr ratio of 0 708230 for cc5 indicates that formation waters also interacted with clays within continental deposits during this period stylolites formed in relation to faulting and previous hydroplastic normal faults reactivated as reverse and strike slip faults allowing fluid flow cc7 precipitated after cc6 also from fluids in isotopic disequilibrium with their adjacent host rock the fluid system continued open during the oligocene when cc8 precipitated in normal faults affecting syn orogenic conglomerates deposited during the reactivation of the lower pedraforca thrust sheet the influence of deformation on fluid flow observed in the lower pedraforca thrust sheet is similar to that observed in other fractured areas worldwide

u pb dating of calcite veins reveals complex stress evolution and thrust sequence in the bighorn basin wyoming usa reply we report u pb absolute ages of calcite cements from a diffuse vein network documented in the bighorn basin wyoming usa where distinct systematic vein sets developed at the front of the thin skinned sevier orogen during laramide layer parallel shortening and during thick skinned laramide thrusting and folding the u pb age distribution illustrates 1 an outward eastward transmission of sevier orogenic stress from 89 7 2 9 ma 2 in the west and from 75 3 2 8 ma in the east and 2 an inward westward development of laramide related fracturing and folding 72 3 0 ma and 45 4 1 8 ma respectively in the east 60 5 4 6 ma and 27 9 1 1 ma respectively in the west which is in accordance with the known sequence of exhumation of the major laramide basement arches our results also show that the stress related to laramide compression first overprinted the stress related to sevier compression in the sedimentary cover around major basement uplifts this study highlights the utility of u pb calcite geochronology as a powerful tool for constraining complex sequences of deformation in orogenic forelands

sea surface temperature productivity and hydrological changes in the northern indian ocean maldives during the interval 575 175 ka mis 14 to 7 abstract the south asian monsoon sam drives seasonal changes in the atmospheric and ocean circulation of the tropical indian ocean affecting precipitation on land and oceanic primary productivity this work examined sediments from the international ocean discover program iodp site u1467 iodp expedition 359 located in the maldives inner sea northern indian ocean at a water depth of 487 m the maldives inner sea is a perfect location to study past changes in tropical climate and ocean circulation related to monsoon dynamics in the equatorial indian ocean this study focuses on the 575 175 ka interval from marine isotope stage mis 14 to 7 an important period for human evolution and dispersal to eurasia we reconstructed sea surface temperature sst based on alkenone unsaturation index u 37 k hydrological changes based on terrestrial input of n alkanes and past surface ocean productivity based on total c37 alkenones concentration the u 37 k sst record shows a difference of about 1 5 c between glacial and interglacial periods clearly showing all stages and substages from mis 14 to 7 and revealing a connection between ice sheets extension and sst at the equatorial region the n alkanes concentration and average chain length index indicate vegetation changes at the indian peninsula with drier conditions generally associated with glacial periods precipitation increases abruptly at the end of terminations lasting for a variable time interval in each interglacial period except for mis 13 however other mechanisms superimposed to the glacial interglacial forcing such as the indian ocean dipole iod mode have been invoked to explain shorter scale variability in precipitation over india the total alkenone concentration record indicates that primary productivity at site u1467 is strongly associated with orbital changes probably related to the summer inter tropical insolation gradient sitig 23n 23s on june 21st high primary productivity occurred during intervals of low sitig which resulted in strong inter monsoon april may and october november indian ocean equatorial westerlies iew and reduced precipitation in the equatorial region this mechanism may also be related to the iod which affects the strength of the iew

orbital and millennial antarctic climate variability over the past 800 000 years a high resolution deuterium profile is now available along the entire european project for ice coring in antarctica dome c ice core extending this climate record back to marine isotope stage 20 2 800 000 years ago experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation we assessed the general correspondence between dansgaard oeschger events and their smoothed antarctic counterparts for this dome c record which reveals the presence of such features with similar amplitudes during previous glacial periods we suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records

u pb calcite age of the late permian castile formation delaware basin a constraint on the age of the permian triassic boundary abstract organic rich calcite laminated with gypsum in the evaporitic non fossiliferous castile formation of the delaware basin southwest usa yields a total pb u isochron age of 251 5 2 8 ma mswd 1 3 the castile formation is almost certainly late permian based on its 87 sr 86 sr value of 0 706923 identical to the distinct minimum in the late permian sr curve in this paper we explore the potential for using u pb calcite ages to date traditionally undatable sections and show how this southern midcontinent usa far west texas and southeast new mexico deposit can be correlated to the type section in china we accept that diagenetic alteration can bias u pb results but the data set we present shows no evidence for such alteration clearly with alteration the age we present would represent a minimum age for the castile formation if the age actually dates the castile formation then it requires the permian triassic boundary to be younger than 251 5 2 8 ma

hydrochronology of a proposed deep geological repository for low and intermediate level nuclear waste in southern ontario from u pb dating of secondary minerals response to silurian and cretaceous events u pb ages have been measured on secondary dolomite and silica cements in cambrian sandstone at the base of an 840 m thick sub horizontally bedded sedimentary sequence beneath the bruce nuclear site

stratigraphic placement and age of modern humans from kibish ethiopia in 1967 the kibish formation in southern ethiopia yielded hominid cranial remains identified as early anatomically modern humans assigned to homo sapiens however the provenance and age of the fossils have been much debated here we confirm that the omo i and omo ii hominid fossils are from similar stratigraphic levels in member i of the kibish formation despite the view that omo i is more modern in appearance than omo ii 40ar 39ar ages on feldspar crystals from pumice clasts within a tuff in member i below the hominid levels place an older limit of 198 14 kyr weighted mean age 196 2 kyr on the hominids a younger age limit of 104 7 kyr is provided by feldspars from pumice clasts in a member iii tuff geological evidence indicates rapid deposition of each member of the kibish formation isotopic ages on the kibish formation correspond to ages of mediterranean sapropels which reflect increased flow of the nile river and necessarily increased flow of the omo river thus the 40ar 39ar age measurements together with the sapropel correlations indicate that the hominid fossils have an age close to the older limit our preferred estimate of the age of the kibish hominids is 195 5 kyr making them the earliest well dated anatomically modern humans yet described

past hot fluid flows in limestones detected by δ47 u pb and not recorded by other geothermometers geothermometers are commonly used to reconstruct the diagenetic and thermal history of rocks however characterizing the timing origin and temperature of paleofluid flow remains challenging because it must be assessed indirectly through the analysis of microscopic cements that precipitate and fill intergranular spaces during fluid circulation here we measure both the clumped isotope 47 temperature and in situ u pb age of individual diagenetic calcite cements within a sedimentary section of the paris basin france whose thermal history has been previously inferred to be 70 c have been measured for calcite cements containing single phase aqueous fluid inclusions challenging the commonly accepted assertion that the absence of nucleation of a vapor phase indicates crystallization at low temperature 70 c we suggest that the kinetics of mineralization events prevented the recording of short lived hot fluid flows by other

directly dating geologic events u pb dating of carbonates 1 carbonates are ubiquitous forming in a variety of settings including caves soils the oceans during burial from hydrothermal fluids and along faults u pb dating of carbonates is applicable to almost the entire geologic time scale with results from pleistocene speleothems showing great promise for dating records 1 ma old here we review studies of u pb dating of carbonates from a range of depositional and diagenetic environments and consider published results with regard to stratigraphic associations and the behavior of u and pb in various fluids we detail the steps required to select suitable samples summarize current laboratory techniques and provide directions for improvement of analytical protocols the u pb dating of carbonates has tremendous potential for dating events of geologic interest and is virtually untapped

quantifying deformation processes in the se pyrenees using u pb dating of fracture filling calcites it is difficult to quantify the timing of the deformation processes in brittle fold thrust belts because minerals suitable for dating and well preserved growth strata sediments are scarce or absent here we quantify the duration of thrust sheet emplacement and shortening rates in the se pyrenean thrust sequence using u pb dating of fracture filling calcites the obtained u pb dates reveal a minimum duration for the emplacement of each thrust unit 18 7 ma for the boixols upper pedraforca 11 6 ma for the lower pedraforca and 14 3 ma for the cadi thrust sheets and show that piggy back thrusting was accompanied by post emplacement deformation of the upper thrust sheets above the lower sheets during their south directed tectonic transport we calculated shortening rates of 0 6 3 1 and 1 1 mm a 1 from the older to younger emplaced thrust sheets our results also reveal the formation of local normal faults during the late oligocene as a result of the late stages of compression and exhumation in the se pyrenees we observed that temperatures 110 c could be a limiting factor when applying the u pb dating method supplementary material u pb analytical results concordia plots and fracture data are available at https doi org 10 6084 m9 figshare c 5078862

high precision u pb zircon age constraints on the guadalupian in west texas usa abstract the guadalupian epoch was characterized by major changes in paleogeography paleoclimate and biodiversity yet the paucity of precise and accurate radioisotopic dates from the guadalupian stages in their type area guadalupe mountains national park in west texas has rendered their calibration inadequate in this study we report high precision u pb zircon geochronology by the ca id tims method from three ash beds 2 internal errors only in the rader member of the bell canyon formation at the back ridge section 262 127 0 097 ma mswd 0 89 n 3 the lower pinery member of the bell canyon formation at the frijole section 264 23 0 13 ma mswd 0 89 n 8 and the basal south wells member of the cherry canyon formation at the monolith canyon section 266 525 0 078 ma mswd 0 62 n 5 the bayesian interpolation statistics method is used to establish an age stratigraphy model that estimates the base of the capitanian to be 264 28 0 16 ma serving as the best age estimate for the capitanian stage at present in addition we review the existing geochronology from the guadalupian series in west texas and seek to propose more precise temporal estimates of guadalupian geological and biological events these data constrain the high frequency sequences of the cherry canyon and bell canyon formations in the guadalupe mountains national park area accordingly the base of the wordian is estimated at 266 9 0 4 ma and the illawarra geomagnetic polarity reversal in west texas at 267 4 0 4 ma to 266 5 0 3 ma the global end guadalupian extinction began in the conodont zone of jinogondolella altudaensis above the base of the reef trail member of the bell canyon formation and might continue to the clarkina postbitteri postbitteri zone in the earliest wuchiapingian the conodonts display a rapid evolutionary rate during this interval this constrains the biotic crisis from ca 260 ma to 259 ma based on our conodont age estimation the emplacement of the emeishan large igneous province elip in south china has been constrained to ca 260 ma to 257 4 ma based on zircon u pb geochronology by the ca id tims method overlapping with the end guadalupian extinction which provides support for the temporal relationship between them additionally the elip persisted into the early wuchiapingian and may have hampered ecosystem restoration during the post extinction interval

methane and the origin of five element veins mineralogy age fluid inclusion chemistry and ore forming processes in the odenwald sw germany abstract five element veins ag bi co ni as have been valuable mineral deposits since medieval times the characteristic occurrence of large aggregates of native metals up to several dm surrounded by a succession of arsenides makes this vein type attractive for mining industry natural history museums and private mineral collectors nevertheless the exact formation process of these specific vein types has not been fully understood this is the first case study applying a new model which includes methane as a reducing agent to two typical examples of such mineralisations from the odenwald sw germany we analysed all mineralogical varieties ag as and bi dominated of the five element veins in the odenwald sw germany in terms of ore textures mineral chemistry fluid inclusion compositions microthermometry and raman spectroscopy stable isotopes c o and s and in situ u pb age dating of calcite and prehnite a variety of ag bi and as dominated native metal arsenide calcite veins sulphide calcite veins and arsenide free ag hg barite veins occurs in the odenwald and has been examined in this study all arsenide veins have in common that up to dm sized often dendritic native metals are overgrown by a succession of arsenides followed by carbonate and finally sulphides the succession of arsenides shows a distinct spatial and temporal chemical trend in their composition this trend evolves from ni to co and finally fe dominated compositions from the core to the rim in contrast spatially closely related ag hg barite veins consist of almost mono mineralic amalgam inter grown with barite in situ u pb age dating of low u calcite and prehnite was applied to constrain the age of hydrothermal mineralisation the results imply that the five element veins formed at 170 180 ma from na ca cl fluids at 290 c salinities of 27 wt and ca ca na of 0 30 to 0 35 in the presence of methane the age data clearly relate the relevant fluid migration to extension and crustal thinning caused by the opening of the north atlantic ternary mixing of a deep seated metal rich basement brine fluid a a sulphide bearing h2s and hs basinal sedimentary brine fluid b and methane dominated fluid gas fluid c induce ore formation mixing of such chemically contrasting fluids results in a strong chemical disequilibrium of the mixed fluid which potentially leads to rapid precipitation of native metals and arsenides with these specific ore textures in contrast sulphide bearing calcite veins formed under similar p t conditions due to mixing of fluid a and b while fluid c was absent additionally u pb analyses of post ore calcite yields ages of 60 ma which indicates that a second calcite formation event is associated with the onset of the upper rhine graben rifting veins with amalgam and barite form as a consequence of post ore oxidation of ag2s at 135 c conspicuously this secondary silver ii has hg contents of up to 30 wt in contrast to hg contents below 1 wt of primary silver i and ag2s the formation of amalgam was most likely related to decrease of the s2 so42 ratio due to cooling of the late hydrothermal fluid resulting in the destabilisation of hg bisulphide complexes in this fluid

dating and characterizing primary gas accumulation in precambrian dolomite reservoirs central sichuan basin china insights from pyrobitumen re os and dolomite u pb geochronology abstract primary gas accumulation with trillions of cubic meters of gas volumes was discovered recently in the precambrian dengying formation of the gaoshiti moxi block central sichuan basin china in this study we investigated the pervasive saddle dolomite cements and solid bitumens within karst vugs in the dengying dolomite reservoirs using laser ablation inductively coupled plasma mass spectrometry la icp ms in situ u pb dating we obtained a high precision absolute age of 259 4 3 0 ma for the saddle dolomite cementation consistent in timing with the eruption of emeishan flood basalts 262 251 ma combined with high homogenization temperatures th and salinities of primary fluid inclusion as well as rare earth element ree compositions we consider that the saddle dolomite precipitation was likely related to hydrothermal activity driven by the emeishan mantle plume the identification of rare surviving oil inclusions and extensive solid bitumens within the dolomite vugs is indicative of the presence of paleo oil reservoirs these bitumens are characterized by high equivalent vitrinite reflectance requ no fluorescence and deformed fibrous textures typical of highly mature pyrobitumens gas geochemistry data indicates that only minor thermochemical sulfate reduction tsr has occurred thus the pyrobitumen was interpreted to result mainly from the thermal cracking of paleo oils and its associated re os isochron age of 154 21 ma representing the timing of dry gas formation petrographical evidence suggests that the paleo oil charge must have taken place after sparry dolomite cementation but prior to pyrobitumen generation this combined with coeval aqueous inclusion th data and published thermal burial models constrains the time of paleo oil emplacement to ca 222 205 ma suggesting an oil filling event related to the indosinian orogeny this study documented the first chronological data constraining the complex evolution history of a petroleum system in one of the oldest primary gas reservoirs in the world

insolation cycles as a major control of equatorial indian ocean primary production analysis of a continuous sedimentary record taken in the maldives indicates that strong primary production fluctuations 70 to 390 grams of carbon per square meter per year have occurred in the equatorial indian ocean during the past 910 000 years the record of primary production is coherent and in phase with the february equatorial insolation whereas it shows diverse phase behavior with 18o depending on the orbital frequency eccentricity obliquity or precession examined these observations imply a direct control of productivity in the equatorial oceanic system by insolation in the equatorial indian ocean productivity is driven by the wind intensity of westerlies which is related to the southern oscillation therefore it is suggested that a precession forcing on the southern oscillation is responsible for the observed paleoproductivity dynamics

influence of the water content on x ray fluorescence core scanning measurements in soft marine sediments the x ray fluorescence xrf core scanner provides bulk sediment chemistry data measured nondestructively at the split core sediment surface although this method is widely accepted there is little known about the effects of physical properties such as density and water content on xrf core scanner data comparison of xrf scanner measurements from the sediment surface and dry powder samples of sediment core geob7920 indicates strongly reduced element intensities for the lighter elements al and si we relate the lower element intensities of the measurements taken at the sediment surface to the amount of water in the sample volume analyzed by the xrf core scanner the heavier elements k ca ti and fe remain relatively unaffected by the variation of any physical property within sediment core geob7920 additionally we successfully use the elemental intensity of cl as a proxy for the seawater content in the sample volume analyzed by the xrf core scanner this enables the establishment of a correction function for the elements al and si that corrects for the radiation absorption of the water content in sediment core geob7920 off cape blanc nw africa

variations of oxygen minimum and primary productivity recorded in sediments of the arabian sea abstract two deep sea sediment cores from the northeastern and the southeastern arabian sea were studied in order to reconstruct the palaeoenvironments of the past glacial cycles core 136kl was recovered from the high productivity area off pakistan within the modern oxygen minimum zone omz by contrast modern primary productivity at the site of md900963 close to maldives is moderate and bottom waters are today well oxygenated for both cores we reconstructed the changes in palaeoproductivity using a set of biomarkers alkenones dinosterol and brassicasterol the main result is that primary productivity is enhanced during glacial stages and lowered during interstadials the proxies associated with productivity show a 23 kyr cyclicity corresponding to the precession related insolation cycle palaeoredox conditions were studied in both cores using a new organic geochemical parameter c35 c31 n alkane ratio developed by analysing surface sediments from a transect across the omz off pakistan the value of this ratio in core 136kl shows many variations during the last 65 kyr indicating that the omz was not stable during this time it disappeared completely during heinrich and the younger dryas events pointing to a connection between global oceanic circulation and the stability of the omz the c35 c31 ratio determined in sediments of core md900963 shows that bottom waters remained rather well oxygenated over the last 330 kyr which is confirmed by comparison with authigenic metal concentrations in the same sediments a zonally averaged circulation biogeochemical ocean model was used to explore how the intermediate indian ocean responds to a freshwater flux anomaly at the surface of the north atlantic as suggested by the geochemical time series both the abundance of southern ocean water and the oxygen concentration are significantly increased in response to this freshwater perturbation

chronologic constraints on hominin dispersal outside africa since 2 48 ma from the zarqa valley jordan abstract recent discoveries constrain the presence of hominins in north africa since ca 2 4 ma and in china since ca 2 1 ma providing a new temporal framework for the earliest migration out of africa no paleolithic sites of such age exist in the levant the natural corridor between africa and asia the dawqara formation in the zarqa valley jordan has been known since the early 1980s because of the presence of artifacts at different stratigraphic levels within its fluvial sediments consisting of choppers cores and flakes although most of the artifacts display signs of transport they bear unambiguous evidence of manufacture and document hominin presence in the zarqa valley during the deposition of dawqara formation based on integrated chronology provided by paleomagnetic 40ar 39ar and u pb dating methods our study shows that the dawqara formation was deposited between 2 52 0 01 ma and the matuyama olduvai geomagnetic reversal 1 95 ma by linear interpolation the artifact bearing stratigraphic levels within the dawqara formation have ages of ca 2 48 ma 2 24 ma 2 16 ma 2 06 ma and 1 95 ma respectively possibly documenting continuous hominin presence in the zarqa valley these new ages for the dawqara assemblage constrain the earliest hominin dispersal out of africa to the beginning of the pleistocene and pre date by ca 300 kyr the hominin occupation of chinese loess plateau

stable carbon cycle climate relationship during the late pleistocene a record of atmospheric carbon dioxide co2 concentrations measured on the epica european project for ice coring in antarctica dome concordia ice core extends the vostok co2 record back to 650 000 years before the present yr b p before 430 000 yr b p partial pressure of atmospheric co2 lies within the range of 260 and 180 parts per million by volume this range is almost 30 smaller than that of the last four glacial cycles however the apparent sensitivity between deuterium and co2 remains stable throughout the six glacial cycles suggesting that the relationship between co2 and antarctic climate remained rather constant over this interval

summer monsoon variations over the last 1 2 ma from the weathering of loess soil sequences in china the loess soil sequence in northern china contains a near continuous record of quaternary paleoclimate magnetic susceptibility and grain size have so far been the only proxies available to address the long term changes of the east asian paleomonsoon extending back to more than one million years in this study the ratio of cbd citrate bicarbonate dithionite extractable free fe2o3 fed a measure of iron liberated by chemical weathering versus the total fe2o3 available fet was measured on samples at 10 cm intervals taken from two loess sections deposited over the last 1 2 ma variations of this index are highly consistent with other pedological indicators but in addition provide a quantitative measurement of the degree of pedogenesis in the loess plateau since chemical weathering in the region mainly depends upon summer precipitation and temperature weathering intensity primarily reflects changes in the east asian summer monsoon the new proxy has been used to document a series of summer monsoon changes of global significance which are not necessarily recorded by magnetic susceptibility

unusual marbles in a non metamorphic succession of the sw alps valdieri italy due to early oligocene hydrothermal flow in the sw alps at the ne margin of the argentera massif the occurrence of isolated bodies of silicate bearing marbles valdieri marble laterally passing to non metamorphic mesozoic limestones of the dauphinois succession appears enigmatic since their origin cannot be related to the regional metamorphism the stratigraphic geometric petrographic and geochemical features of the valdieri marble indicate that it originated from the upflow of hydrothermal fluids which deeply recrystallised the limestone and provoked the abundant neoblastesis of silicate minerals at an estimated crystallisation temperature of ca 350 c this paper provides for the first time an absolute u pb age comprised between 30 and 31 6 ma early oligocene for the valdieri marble which is affected by a syn genetic shear foliation in turn crosscut by the main alpine tectonic foliations the hydrothermal fluids that formed the valdieri marble migrated along low angle shear zones mostly parallel to the sedimentary primary bedding which were downward connected with high angle master faults of the alpine sw transfer a main oligocene early miocene transcurrent shear zone at the southern termination of the western alps the localized heat flow sustaining the hydrothermal system could be related to the early oligocene thermal event well documented by magmatic activity in the western and central alps

nonstationary phase of the plio pleistocene asian monsoon paleoclimate records indicate that the strength of the asian summer monsoon is sensitive to orbital forcing at the obliquity and precession periods 41 000 and 23 000 years respectively and the extent of northern hemisphere glaciation over the past 2 6 million years the timing phase of strong monsoons has changed by 83 degrees in the precession and 124 degrees in the obliquity bands relative to the phase of maximum global ice volume inferred from the marine oxygen isotope record these results suggest that one or both of these systems is nonstationary relative to orbital forcing

improving confidence in ferromanganese crust age models a composite geochemical approach abstract accurate age models for marine ferromanganese fe mn crusts are essential to understand paleoceanographic changes and variations in local environmental factors affecting crust growth rate and their lateral continuity however no absolute method exists for dating these deposits beyond the age of 10 myr which requires the combination of a number of approaches here we present a composite age model for a 15 cm thick fe mn crust sample obtained by unique core drilling using a remotely operated vehicle at a water depth of 1130 m on the summit of tropic seamount in the north east atlantic the age model is based on cross validation of laser ablation u pb dating co chronometry and os isotopes these enable robust calibration of the age depth model using the bayesian statistical modelling of markov chain monte carlo mcmc simulations the results show that this fe mn crust commenced growth in the late cretaceous between 73 and 77 ma and grew at a rate between 1 and 24 mm myr averaging 4 mm myr the phosphatised carbonate substrate capping tropic seamount and underlying most of the fe mn crusts yields a u pb age of 84 4 myr and provides the upper age limit for the model less radiogenic excursions of 188os 187os in the vertical profile through the crust permit the identification of key inflection points in the os isotope seawater curve at the eocene oligocene and cretaceous paleogene transitions growth rates estimated from the empirical co chronometer are combined with the age envelope defined by the os data and used to validate the mcmc simulations the model identifies five hiatuses that occurred during the pliocene 2 5 1 9 5 3 1 7 ma early miocene 16 1 27 2 ma oligocene 29 2 32 1 ma eocene 41 2 52 0 6 ma and the late paleocene 55 1 59 1 4 ma a major phosphatisation event affecting the fe mn core can be dated to the late eocene 38 1 2 ma which coincides with a recorded change in the global oceanic system from warm and sluggish circulation to cold and vigorous thermohaline driven meridional overturn at the onset of antarctic glaciation

a 350 000 year summer monsoon multi proxy stack from the owen ridge northern arabian sea five summer monsoon proxies from the northern arabian sea are combined using stacking and principal components analysis pca to create two very similar multi proxy records of summer monsoon variability the five individual proxies all respond to monsoon variability but are largely independent in terms of the processes that complicate their interpretation as summer monsoon indicators e g preservation dissolution diagenesis sediment reworking as such stacking and pca average out non monsoon variance yielding a more pure monsoon signal these stacked and pca records hereafter summer monsoon stack and summer monsoon factor allow evaluation of relative monsoon strength through time as well as the relative concentration of variance within orbital bands these two parameters are less reliable when estimated from individual proxy records in fact the summer monsoon factor smf accounts for only 33 of the total variance in the five records suggesting that relative amplitude variations in each individual proxy time series are influenced by non monsoon processes the summer monsoon stack sms and smf are spectrally very similar dominated by variance in the 41 k y obliquity and 23 k y precession bands there is very little variance at the 100 k y eccentricity band associated with large scale changes in global ice volume indeed equally strong monsoons occur in both glacial and interglacial intervals within the 23 k y precession cycle monsoon maxima fall at 121 relative to precession minima june 21 perihelion maximum northern hemisphere nh summer insolation this phase falls midway between 18o minima 78 and december 21 perihelion 180 indicating that two mechanisms exert equal influence in determining the timing of strong summer monsoons within the precession band 1 sensible heating of the asian plateau which is maximized at times of ice volume minima 78 and 2 latent heat export from the southern subtropical indian ocean which is maximized at times of december 21 perihelion 180 the seasonal cycle at december 21 perihelion is characterized by warm southern hemisphere sh summers followed by cold sh winters a combination that preconditions the ocean to export latent heat during the boreal summer monsoon season summer monsoon winds transport this latent heat into asia where it is released during precipitation enhancing the asian monsoon low within the 41 k y obliquity cycle monsoon maxima are in phase with obliquity maxima this indicates that two mechanisms quite similar to those in the precession band influence the timing of strong summer monsoons in the obliquity band 1 sensible heating of the asian plateau but with no ice volume delay and 2 latent heat export from the southern subtropical indian ocean which is maximized at times of obliquity maxima again the seasonal cycle at obliquity maximum is characterized by warm sh summers followed by cold sh winters ideal for maximizing latent heat export during the boreal summer monsoon

glacial interglacial water cycle global monsoon and atmospheric methane changes the causes of atmospheric methane ch4 changes are still a major contention in particular with regards to the relative contributions of glacial interglacial cycles monsoons in both hemispheres and the late holocene human intervention here we explore the ch4 signals in the antarctic epica dome c and vostok ice records using the methods of timeseries analyses and correlate them with insolation and geological records to address these issues the results parse out three distinct groups of ch4 signals attributable to different drivers the first group 80 variance well tracking the marine 18o record is attributable to glacial interglacial modulation on the global water cycle with the effects shared by wetlands at all latitudes from monsoonal and non monsoonal regions in both hemispheres the second group 15 variance centered at the 10 kyr semi precession frequency is linkable with insolation driven tropical monsoon changes in both hemispheres the third group 5 variance marked by millennial frequencies is seemingly related with the combined effect of ice volume and bi hemispheric insolation changes at the precession bands these results indicate that bi hemispheric monsoon changes have been a constant driver of atmospheric ch4 this mechanism also partially explains the holocene ch4 reversal since 5 kyr bp besides the human intervention in the light of these results we propose that global monsoon can be regarded as a system consisting of two main integrated components one primarily driven by the oscillations of inter tropical convergence zone itcz in response to the low latitude summer insolation changes anti phase between the two hemispheres i e the itcz monsoon component and another modulated by the glacial interglacial cycles mostly synchronous at the global scale i e the glacial interglacial monsoon component although atmospheric ch4 record integrates all wetland processes including significant non monsoonal contributions it is the only and probably the best proxy available to reflect the past changes of global monsoon however the utility of ch4 as a proxy of monsoon changes at any specific location is compromised by its bi hemispheric nature

an image mapping approach to u pb la icp ms carbonate dating and applications to direct dating of carbonate sedimentation we present a new approach to laser ablation inductively coupled plasma mass spectrometry la icp ms u pb dating of carbonates based on selection and pooling of pixels from 2 d elemental and isotopic ratio maps this image mapping technique is particularly useful for targeting subdomains in samples with complex geological histories key major and trace elements that are sensitive to detrital components postformational fluid ingress mineralogical changes or diagenetic overprinting are measured along with the pb and u isotopic data laser sampling is undertaken along successive linear rasters that are compiled into maps using the monocle add on for iolite with one pixel in the map corresponding to one time slice of the time resolved signal these element element ratio and isotope ratio maps can be overlain over photomicrographs or scanning electron microscopy images to spatially link compositional data to textural and structural features the pixels corresponding to likely homogeneous age domains can be isolated by applying appropriate selection criteria e g th 0 3 ppm mg ca 0 004 and pooled into pseudo analyses using a proxy for the parent daughter ratio e g 207pb 235u 238u 208pb to retrieve the largest possible spread of the data points on isochron diagrams the approach is best suited for analytical setups capable of rapidly or simultaneously scanning over a large mass range and can yield a precision of 1 or better on quadrupole instruments depending on u concentration 238u 204pb and age of the sample the sample specific filtering criteria for selection and rejection of data and their rationale can be reported resulting in more transparency with regard to data processing

mid brunhes strengthening of the indian ocean dipole caused increased equatorial east african and decreased australasian rainfall 1 the tropical indian ocean is an important component of the largest warm pool marked by changes in sea surface temperatures and depths of thermocline and mixed layer in its western and eastern extremities leading to the development of a dipole mode the indian ocean dipole iod a narrow band of westerlies 7 n to 7 s sweep the equatorial indian ocean during the april may and october november transitions between the summer and winter monsoon seasons these indian ocean equatorial westerlies iew are closely related to the iod intensifying the upper ocean eastward equatorial current also known as wyrtki jets the strength of the iod iew determines the moisture content in east africa a major decrease in the strength of the iew strengthening or positive mode of the iod during the mid brunhes epoch 300 250 kyr bp coincides with a wetter equatorial east africa a drier australasia and a stronger indian summer monsoon indicating that the iod iew play a significant role in driving climate change in east africa australasia and south asia

rapid middle eocene temperature change in western north america abstract eocene hyperthermals are among the most enigmatic phenomena of cenozoic climate dynamics these hyperthermals represent temperature extremes superimposed on an already warm eocene climate and dramatically affected the marine and terrestrial biosphere yet our knowledge of temperature and rainfall in continental interiors is still rather limited we present stable isotope 18o and clumped isotope temperature 47 records from a middle eocene 41 to 40 ma high elevation mammal fossil locality in the north american continental interior montana usa 47 paleotemperatures of soil carbonates delineate a rapid 9 11 c temperature excursion in the paleosol record 47 temperatures progressively increase from 23 c 3 c to peak temperatures of 32 c 3 c and subsequently drop by 11 c this hyperthermal event in the middle eocene is accompanied by low 18o values and reduced pedogenic carbonate concentrations in paleosols based on laser ablation u pb geochronology of paleosol carbonates in combination with magnetostratigraphy biostratigraphy stable isotope and 47 evidence we suggest that this pronounced warming event reflects the middle eocene climatic optimum meco in western north america the terrestrial expression of northern hemisphere meco in western north america appears to be characterized by warmer and wetter sub humid conditions compared to the post meco phase large and rapid shifts in 18o values of precipitation and pedogenic caco3 contents parallel temperature changes indicating the profound impact of the meco on atmospheric circulation and rainfall patterns in the western north american continental interior during this transient warming event

halogen and trace element analysis of carbonate veins and fe oxyhydroxide by la icpms implications for seafloor alteration atlantis bank sw indian ridge halogens are critical elements for transporting metals in hydrothermal solution and tracing the sources of fluids and volatiles in subduction zones this study tested the suitability of la icpms for simultaneous measurement of cl br and i with selected trace elements in altered gabbros recovered from the atlantis bank core complex close to the sw indian ridge the aim was to better understand the causes of i enrichment in low temperature carbonate and fe oxyhydroxide alteration which is intensely developed in core recovered from between 100 and 600 mbsf down hole u1473a drilled during expedition 360 of the international ocean discovery program iodp the analysis of reference materials including scapolites durango apatite usgs and nist reference glasses and volcanic glasses demonstrate cl br and i can be measured in most minerals but accuracy is limited by matrix dependent laser backgrounds false signals of cl br and i generated during sample ablation silicate reference glasses define reproducible laser backgrounds of 320 g g cl and 1 7 g g br that point to limits of quantification of 200 g g cl and 1 g g br in silicate glasses after correction for laser backgrounds in contrast laser backgrounds are much lower and possibly negligible for carbonate suggesting limits of quantification as low as 50 g g cl and 0 1 g g for br dependent on instrument sensitivity laser backgrounds for i varied between minerals and analytical sessions there was no laser background for i in apatite and under favourable conditions silicate glasses have laser backgrounds of 1 g g in addition to the laser backgrounds we report a correction for interference of doubly charged rare earth elements on br measurement which significantly improves data quality for some samples the atlantis bank alteration minerals investigated include calcite veins and fe oxyhydroxide which is intermixed with and cut by veinlets of calcite and smectite the fe oxyhydroxide contains 100 s 1000s g g cl 10s g g br and 5 30 g g i and it is strongly enriched in other trace elements including b and as most calcite veins contain 100 200 g g cl 0 4 0 9 g g br and 5 26 g g i among the halogens i is uniquely correlated with divalent cations in calcite including mg and sr consistent with its incorporation into the carbonate lattice as iodate in most cases smectite contains less i than coexisting calcite or fe oxyhydroxide but three smectite grains in one sample are exceptionally enriched with 150 240 g g i the in situ analyses support the attribution of exceptional iodine enrichment of atlantis bank lithologies to preferential adsorption of iodate over halides by fe oxyhydroxides and subsequent remobilisation with preferential fixing of iodate in carbonate dominated alteration the data demonstrate the utility of la icpms for in situ halogen studies iodine in carbonate veins can provide information about fluid oxidation state and fluid rock reaction history however further work is required to test if cl and br in carbonate can provide information about fluid sources

δ18o δ13c trace elements and ree in situ measurements coupled with u pb ages to reconstruct the diagenesis of upper triassic atoll type carbonates from the panthalassa ocean abstract owing to their isolated oceanic setting atoll type carbonates are well suited for documenting carbonate deposition and diagenesis in oceanic environments away from continental influence the atoll type dalnegorsk limestone taukha terrane russian far east deposited in the gigantic but poorly documented panthalassa ocean preserves a complete record of the diagenetic evolution of an upper triassic system out of the tethyan domain to study the diagenesis of this carbonate system we developed a novel analytical workflow combining cathodoluminescence petrography with high resolution analyses of environmental proxies in calcitic cements 18o 13c reey trace and minor major elements and in situ u pb dating of calcite cements to precisely reconstruct the chronology of the diagenetic events we combined these lines of evidence to establish a model of atoll evolution from deposition to dismantling based on 10 identified diagenetic episodes the dalnegorsk limestone records emergence at the norian rhaetian transition marked by meteoric and evaporitic cements followed by dismantling of the atoll edges after drawning in the early jurassic neomorphism of calcitic shells occurred at the onset of calcitic sea conditions during the toarcian bajocian the limestone was thoroughly cemented during the middle late jurassic and accreted within the taukha terrane during the late jurassic early cretaceous accretion resulted in fracturing brecciation and recrystallisation of the dalnegorsk limestone this model is potentially applicable to any similar atoll system irrespective of age the evidence presented here extends our knowledge of late triassic environments in the panthalassa ocean and more generally our understandingg of mid oceanic limestone formation and evolution

a 225 kyr record of dust supply paleoproductivity and the oxygen minimum zone from the murray ridge northern arabian sea abstract analysis of a 15 m long sediment core recovered from the murray ridge northern arabian sea reveals a 225 000 year record of climate induced variations in surface water productivity mid water ventilation and dust input in the northern arabian sea productivity and dust input records closely resemble those from the owen ridge and oman margin also the phase lag of 10 kyr between maximum productivity and precession minimum is in phase with the summer monsoon upwelling record from the owen ridge and the oman margin this implies that the productivity variations in the northern arabian sea during the last 225 kyr are primarily controlled by changes in the indian ocean summer monsoon the winter monsoon obviously played a minor role in the productivity history of the northern arabian sea another result from this study is that the mg al record from the murray ridge nicely documents the post glacial flooding of the persian gulf which is the main glacial source for dolomite dust in this region finally it is concluded that the intensity of the omz co varies with surface water productivity being weak during periods of reduced summer monsoon especially during glacial periods

mantle and crustal sources of magmatic activity of klyuchevskoy and surrounding volcanoes in kamchatka inferred from earthquake tomography

iberian margin sea surface temperature during mis 15 to 9 580 300 ka glacial suborbital variability versus interglacial stability 1 past sea surface water conditions of the western iberian margin were reconstructed based on biomarker analyses of a marine deep sea core md03 2699 from the estremadura spur north off lisbon providing new insights into orbital and suborbital scale climate variability between marine isotope stage mis 15 to mis 9 580 to 300 ka we use biomarker based proxy records such as the alkenone unsaturated index to estimate sea surface temperature sst the total alkenone concentration to reconstruct phytoplankton productivity and terrestrial biomarkers to evaluate the continental input the results extend the existing biomarker record namely the sst for the iberian margin back to the sixth climatic cycle 580 ka a general trend of stable interglacials contrasts with glacial periods and glacial inceptions which are marked by high frequency variability thus several short lived climatic coolings were identified by large sst decreases the occurrence of ice rafted detritus and high percentages of the tetraunsaturated alkenone c37 4 some of these events were extremely cold and similar in their general trends to the well known heinrich events of the last glaciation we identified eight heinrich type events between 580 and 300 ka the general deglaciation pattern detected between mis 15 and mis 9 is similar in their general trends to that characterizing the more recent climatic cycles i e marked by two coolings separated by a short warming episode which may reflect the southward northward and southward migration of the polar front

u pb dating of cements in mesozoic ammonites dating sedimentary carbonates using the u pb method can help improve the phanerozoic timescale using a novel combination of laser ablation multi collector inductively coupled plasma mass spectrometry la mc icp ms and thermal ionization multi collector mass spectrometry tims u pb numerical ages were obtained on early diagenetic calcite cements in jurassic ammonites in which concentrations of u range from 0 47 to 5 3 ppm the calcite cements of two ammonites is1 and is2 from the uppermost bifrons zone of the toarcian 179 180ma of the uk gave tims normalized la u pb dates of 164 9 5 3 ma and 166 7 4 8ma respectively normalizing la icp mc ms data to an in house calcite standard gave a more precise date of 165 5 3 3 ma for is1 cement an unzoned ammonite ss2 of bajocian age 168 170 ma yield a tims normalized la u pb age of 158 8 4 3 ma for its early diagenetic cement both the combined la mc icp ms and tims approach and the use of a calcite laser ablation standard can result in accurate ages of cements with uncertainties of 2 3 2 the later however is more efficient and precise these u pb dates of cements are 10 to 20 myr younger than the numerical ages of the biostratigraphic intervals from which the ammonites derive the u pb dates are taken to represent the time at which the aragonite shell of the ammonite inverted to calcite and released its u to precipitate in a late diagenetic alteration of early diagenetic fringing cements concentrations of u and pb in a range of other pristine biogenic carbonateswere found too low u b 0 01 ppm for meaningful dating using laser ablation method

timing kinematics and displacement of the taltal fault system northern chile implications for the cretaceous tectonic evolution of the andean margin

improving paleohydrological and diagenetic reconstructions in calcite veins and breccia of a sedimentary basin by combining δ47 temperature δ18owater and u pb age abstract in sedimentary basins the precise temperature and timing at which relatively shallow

interglacial intensity in the north atlantic over the last 800 000 years investigating the complexity of the mid brunhes event the mid brunhes event mbe represents a step like increase between marine isotope stages mis 13 11 in the intensity of interglacial warmth a transect of palaeoclimatic records in the north atlantic from 40 n to the nordic seas indicates strong differences in the expression of the mbe within this region between 40 and 56 n sea surface and air temperature records suggest that all interglacials of the past 800 000 years were characterized by similar levels of warmth so there is no evidence for an mbe in these latitudes of the north atlantic north of 56 n there is increasing evidence for interglacials mis 19 13 being cold relative to mis 11 1 as most records of long term interglacial diversity suggest the mbe is a global event the north atlantic is clearly anomalous furthermore the strong spatial difference in temperature conditions during interglacials mis 19 13 in the north atlantic means that the temperature gradient across this region would have been enhanced in fact effectively doubled in magnitude during this interval copyright 2013 john wiley sons ltd

controls on the east asian monsoon during the last glacial cycle based on comparison between hulu cave and polar ice core records previous studies have suggested a sound chronological correlation between the hulu cave record east asian monsoon and greenland ice core records which implies a dominant control of northern hemisphere climate processes on monsoon intensity we present an objective straightforward statistical evaluation that challenges this generally accepted paradigm for sub orbital variability we propose a more flexible global interpretation which takes into account a broad range of variability in the signal structures in the hulu cave and polar ice core records rather than a limited number of major transitions our analysis employs the layer counted greenland ice core chronology 2005 gicc05 which was developed for greenland records and has since been applied via methane synchronisation to the high resolution 18oice series from epica dronning maud land edml the gicc05 chronology allows these ice core records to be compared to the u th dated hulu cave record within relatively narrow 3 bounds of age uncertainty following previous suggestions our proposed interpretation suggests that the east asian monsoon is influenced by a combination of northern hemisphere pull which is more intense during boreal warm periods and southern hemisphere push which is more intense monsoon during austral cold periods our analysis strongly suggests a dominant control on millennial scale monsoon variability by southern hemisphere climate changes during glacial times when the monsoon is weak overall and control by northern hemisphere climate changes during deglacial and interglacial times when the monsoon is strong the deduced temporally variable relationship with southern hemisphere climate records offers a statistically more plausible reason for the apparent coincidence of major east asian monsoon transitions with northern hemisphere dansgaard oeschger do climate events during glacial times than the traditional a priori interpretation of strict northern hemisphere control

progressive reactivation of the volcanic plumbing system beneath tolbachik volcano kamchatka russia revealed by long period seismicity abstract after lying dormant for 36 yr the tolbachik volcano of the klyuchevskoy group started to erupt on 27 november 2012 we investigate the preparatory phase of this eruption via a statistical analysis of the temporal behavior of long period lp earthquakes that occurred beneath this volcanic system the lp seismicity occurs close to the surface beneath the main volcanic edifices and at 30 km depth in the vicinity of a deep magmatic reservoir the deep lp earthquakes and those beneath the klyuchevskoy volcano occur quasi periodically while the lp earthquakes beneath tolbachik are clustered in time as the seismicity rate increased beneath tolbachik days before the eruption the level of the time clustering decreased we interpret this as a manifestation of the evolution of the volcano plumbing system we suggest that when a plumbing system awakes after quiescence multiple cracks and channels are reactivated simultaneously and their interaction results in the strong time clustering of lp earthquakes with time this network of channels and cracks evolves into a more stable state with an overall increased permeability where fluids flow uninhibited throughout the plumbing system except for a few remaining impediments that continue to generate seismic radiation the inter seismic source interaction and the level of earthquake time clustering in this latter state is weak this scenario suggests that the observed evolution of the statistical behavior of the shallow lp seismicity beneath tolbachik is an indicator of the reactivation and consolidation of the near surface plumbing system prior to the tolbachik eruption the parts of the plumbing system above the deep magmatic reservoir and beneath the klyuchevskoy volcano remain in nearly permanent activity as demonstrated by the continuous occurrence of the deep lp earthquakes and very frequent klyuchevskoy eruptions this implies that these parts of the plumbing system remain in a stable permeable state and contain a few weakly interacting seismogenic sources our results provide new constraints on future mechanical models of the magmatic plumbing systems and demonstrate that the level of time clustering of lp earthquakes can be a useful parameter to infer information about the state of the plumbing system

molecular proxies for paleoclimatology we summarize the applications of molecular proxies in paleoclimatology marine molecular records especially are proving to be of value but certain environmentally persistent compounds can also be measured in lake sediments loess deposits and ice cores the fundamentals of this approach are the molecular parameters the compound abundances and carbon hydrogen nitrogen and oxygen isotopic contents which can be derived by the analysis of sediment extracts these afford proxy measures which can be interpreted in terms of the conditions which control climate and also reflect its operation we discuss two types of proxy those of terrigenous and those of aquatic origin and exemplify their application in the study of marine sediments through the medium of ten case studies based in the atlantic mediterranean and pacific oceans and in antarctica the studies are mainly for periods in the present the holocene and particularly the last glacial interglacial but they also include one study from the cretaceous the terrigenous proxies which are measures of continental vegetation are based on higher plant leaf wax compounds i e long chain circa c30 hydrocarbons alcohols and acids they register the relative contributions of c3 vs c4 type plants to the vegetation in the source areas the two marine proxies are measures of sea surface temperatures sst the longer established one u37k is based on the relative abundances of c37 alkenones photosynthesized by unicellular algae members of the haptophyta the newest proxy tex86 is based on c86 glycerol tetraethers gdgts synthesized in the water column by some of the archaeal microbiota the crenarchaeota

emissions of trace elements during the 2012 2013 effusive eruption of tolbachik volcano kamchatka enrichment factors partition coefficients and aerosol contribution abstract gases and aerosols from the 2012 13 effusive eruption of tolbachik basaltic volcano kamchatka were sampled in february and may 2013 from a lava tube window located 300 m from the eruptive crater temperature at the sampling point was 1060 1070 c the chemical and isotopic compositions of the sampled gases 92 4 h 2 o 3 5 co 2 2 3 so 2 on average d from 25 0 to 38 6 correspond to a typical volcanic arc gas without dilution by meteoric or hydrothermal water halogen contents in the gases 1 37 hcl 0 5 hf were higher than average arc values the total amount of analyzed metallic and metalloid trace elements in the gas exceeded 665 ppm six most abundant trace elements k 250 ppm na 220 ppm si 74 ppm br 48 ppm cu 21 ppm and fe 12 ppm accounted for 95 of the total content of trace elements in the gas the gases contained 24 ppb re 12 ppb ag 4 9 ppb au and 0 45 ppb pt refractory rock forming elements mg al ca and some other elements such as ba and th were transported mainly in the form of silicate microspheres and altered rock particles the concentrations of metals in the eruptive tolbachik gases are higher than the corresponding concentrations in high temperature fumaroles worldwide although the mutual ratios of the elements are approximately the same the gas magma partition coefficients of eleven elements exceed unity including the non metals f s cl br as se and te and the rare metals cd re tl and bi despite the relatively low concentrations of trace elements in the volcanic gases at the highest temperatures superficial magma degassing provides information on the sources and sinks of metals

monitoring of the volcanic rock compositions during the 2012 2013 fissure eruption at tolbachik volcano kamchatka abstract here we present the results from monitoring of the composition of rocks produced during the 2012 2013 fissure eruption at tolbachik volcano fte major and trace element concentrations in 75 samples are reported products of this eruption are represented by high alumina basaltic trachyandesites with higher alkalis and titanium contents than in all previously studied rocks of the tolbachik monogenetic volcanic field rocks erupted during the first three days 27 30 november from the northern also called menyailov group of vents are the most silica and alkali rich sio2 concentrations up to 55 35 wt and k2o up to 2 67 wt from december onwards when the eruptive activity switched from the menyailov vents to the southern naboko group of vents silica content dropped by 2 wt concentrations of mgo feo tio2 and mg increased and k2o and na2o concentrations and k2o mgo ratio decreased for the rest of the eruption the compositions of rocks remained constant and homogeneous no systematic compositional differences between lava bombs and scoria samples are evident trace element distributions in the rocks of the menyailov and naboko vent lavas are relatively uniform menyailov lavas have slightly higher th nb hf y and hree concentrations than the naboko vent lavas at more or less constant element ratios we explain the initial change in geochemistry by tapping of a slightly cooler and fractionated 3 mt and 8 cpx upper part of the magma storage zone before the main storage area began to feed the eruption thermodynamic constraints show that apparent liquidus temperatures varied from 1142 c to 1151 c and thermodynamic modeling shows that variations in compositions are consistent with a high degree of low pressure 100 300 mpa nominally anhydrous fractionation of a parent melt compositionally similar to the 1975 northern breakthrough high mg basalt geochemistry petrological observations and modeling are in agreement with the newly erupted material being derived from remnant high al magma from the 1975 76 southern breakthrough eruption with only slight amounts of cooling less than 1 c per year during the intervening 36 years

tropical ocean temperatures over the past 3 5 million years determining the timing and amplitude of tropical sea surface temperature sst change is an important part of solving the puzzle of the plio pleistocene ice ages alkenone based tropical sst records from the major ocean basins show coherent glacial interglacial temperature changes of 1 to 3 c that align with but slightly lead global changes in ice volume and deep ocean temperature over the past 3 5 million years tropical temperatures became tightly coupled with benthic 18o and orbital forcing after 2 7 million years we interpret the similarity of tropical sst changes in dynamically dissimilar regions to reflect top down forcing through the atmosphere the inception of a strong carbon dioxide greenhouse gas feedback and amplification of orbital forcing at 2 7 million years ago connected the fate of northern hemisphere ice sheets with global ocean temperatures since that time

la mc icp ms u pb dating of low u garnets reveals multiple episodes of skarn formation in the volcanic hosted iron mineralization system awulale belt central asia volcanic hosted iron deposits of the eastern awulale metallogenetic belt in central asia possess a reserve of over 1 2 billion tons of iron ores and constitute one of the most important basements for high grade iron resources in china skarns are widespread in these deposits and closely associated with iron mineralization the ages of these skarns are unclear and their genesis remains debated preventing further investigation into their metallogenic processes we focused on garnets in nine ore bearing skarns from three large scale iron deposits chagangnuoer dunde and beizhan in the eastern awulale belt u pb dating was conducted on these garnets using our in house reference material the taochong garnet tc 13 pb pb isochron age 126 2 23 ma initial pb 207 pb 206 ratio 0 845 0 022 laser ablation multicollector inductively coupled plasma mass spectrometry la mc icp ms was employed in the garnet u pb dating and high precision u pb ages 03 1 6 were obtained highlighting the advantages of la mc icp ms in dating low u minerals the garnet u pb ages of the nine skarn samples fall into three groups i e 329 0 5 1 326 3 3 ma two samples 316 3 2 9 311 2 2 4 ma six samples and 295 6 1 0 ma one sample implying three episodes of skarn alteration in the volcanic hosted iron mineralization system the first and second episodes of skarns formed as a result of contact metasomatism between coeval volcanic rocks and limestone and they have economically important iron mineralization the third was likely caused by a local postcollision granitic intrusion but its metallogenic potential deserves further assessment

orbital scale timing and mechanisms driving late pleistocene indo asian summer monsoons reinterpreting cave speleothem δ18o 1 southeast china cave 18o often interpreted as a pure east asian summer monsoon proxy lags maximum northern hemisphere summer insolation by 2 9 0 3 kyrs at the precession cycle the arabian sea summer monsoon stack lags by 8 1 kyr consistent with 13 other indian and east asian summer monsoon proxies from marine lake and terrestrial archives this 5 kyr phase difference cannot be attributed to age control inadequacies in the marine chronology it requires reconciliation in the context of proxy interpretation both of these lags are incompatible with a direct response to northern hemisphere summer insolation implicating additional forcing mechanisms analysis of heterodynes in the cave 18o spectrum demonstrates that variance contained in the arabian sea summer monsoon proxies also resides in the cave 18o record this variance is subtracted from the cave 18o record yielding a residual that is highly coherent and in phase with precession minima reflecting the impact of winter temperature change on cave 18o meteorological precipitation under cold conditions thus we argue that the timing of light cave 18o peaks cannot be interpreted as reflecting the timing of strong summer monsoons alone the 2 9 kyr precession band phase lag of cave 18o reflects the combined influence of summer monsoon forcing with a phase lag of 8 kyrs relative to precession minima and winter temperature forcing that is in phase with precession minima this interpretation is consistent with modern seasonality in the amount and isotopic composition of rainfall in southeast china

structural evolution of continental and marine permian rock salt of the north german basin constraints from microfabrics geochemistry and u pb ages analyzing the dynamics of microstructural response on natural deformation in rock salt we present microfabric ebsd geochemical and u pb data obtained from permian salt formations of the kiel honigsee salt wall in northern germany the samples were recovered from deep drillings which penetrated through an overturned rock salt sequence of both rotliegend and zechstein deposits the bromide concentration in halite indicates a continental and marine origin for the rotliegend and zechstein deposits respectively despite intense deformation relics of early diagenetic fabrics are still preserved deformation of the impure rotliegend rock salt was accommodated by pressure solution and hydrofracturing as is indicated by the microfabrics and bromide concentration in halite fractures in siliciclastic domains were filled with fibrous halite and deformed by subgrain rotation recrystallization sgr fluid rich zechstein rock salt on the other hand was deformed by formation of subgrains and grain boundary migration gbm the distribution of mineral phases and fluids had a significant impact on the fabric evolution and on strain localization u pb dating of carbonate phases of the rotliegend sequence yielded permian depositional ages and jurassic to cretaceous deformation ages the latter related to diapiric ascent the combination of results traces a dynamic evolution of the rock fabric inside the diapir structure driven by locally active deformation processes that can be correlated with early stages of halite deposition and diagenesis and syntectonic fabric reorganization related to diapirism in an extensional setting

high latitude influence on the eastern equatorial pacific climate in the early pleistocene epoch many records of tropical sea surface temperature and marine productivity exhibit cycles of 23 kyr orbital precession and 100 kyr during the past 0 5 myr refs 1 5 whereas high latitude sea surface temperature records display much more pronounced obliquity cycles at a period of about 41 kyr ref 6 little is known however about tropical climate variability before the mid pleistocene transition about 900 kyr ago which marks the change from a climate dominated by 41 kyr cycles7 when ice age cycles and high latitude sea surface temperature variations were dictated by changes in the earth s obliquity8 9 to the more recent 100 kyr cycles of ice ages here we analyse alkenones from marine sediments in the eastern equatorial pacific ocean to reconstruct sea surface temperatures and marine productivity over the past 1 8 myr we find that both records are dominated by the 41 kyr obliquity cycles between 1 8 and 1 2 myr ago with a relatively small contribution from orbital precession and that early pleistocene sea surface temperatures varied in the opposite sense to local annual insolation in the eastern equatorial pacific ocean we conclude that during the early pleistocene epoch climate variability at our study site must have been determined by high latitude processes that were driven by orbital obliquity forcing

deep and shallow long period volcanic seismicity linked by fluid pressure transfer volcanic long period earthquakes are attributed to pressure fluctuations that result from unsteady mass transport in the plumbing system of volcanoes whereas most of the long period seismicity is located close to the surface the volcanic deep long period earthquakes that occur in the lower crust and uppermost mantle reflect the activity in the deep parts of magmatic systems here we present observations of long period earthquakes that occurred in 2011 2012 within the klyuchevskoy volcano group in kamchatka russia we show two distinct groups of long period sources events that occurred just below the active volcanoes and deep long period events at depths of 30 km in the vicinity of a deep magmatic reservoir we report systematic increases of the long period seismicity levels prior to volcanic eruptions with the initial activation of the deep long period sources that reflects pressurization of the deep reservoir and consequent transfer of the activity towards the surface the relatively fast migration of the long period activity suggests that a hydraulic connection is maintained between deep and shallow magmatic reservoirs the reported observations provide evidence for the pre eruptive reload of the shallow magmatic reservoirs from depth and suggest that the deep long period earthquakes could be used as a reliable early precursor of eruptions shallow volcanic earthquakes can aid eruption forecasts analysis of seismicity beneath the klyuchevskoy volcano group in russia reveals much deeper magma induced earthquakes that may serve as an early eruption indicator