a comparison of methods for evaluating soil redistribution in the severely eroded stavropol region southern european russia abstract in this paper we combined several erosion assessment methods to construct a sediment budget describing soil redistribution and sediment delivery within a study area containing grassed upper slopes a large arable field of 1 3 km2 with a semipermanent rill and ephemeral gully network and a downslope buffer zone of a grassed dry valley balka bank with depositional fans the study site is in the stavropol upland one of the most severely eroded intensively cultivated areas of european russia the methods include two variations of the soil survey approach a proportional 137cs conversion model a mass balance 137cs conversion model a 137cs based tracer budget direct measurement of gully volume by theodolite examination of 137cs depth profiles and a version of the usle model modified and calibrated for russian conditions our results highlight the importance of i comparing such techniques ii validating the results from them and iii the value of combining the outputs of different measurement methods in particular the soil survey approach was able to separate the influence of sheet and linear erosion the proportional 137cs and mass balance 137cs models estimated similar soil redistribution rates 5 5 0 8 and 5 3 0 8 kg m 2 year 1 respectively and were improved when combined with direct measurements of gully volumes rates and locations of sediment redeposition within sinks such as grassed valley banks were best evaluated by combining 137cs depth profile analysis and conversion models with soil profile descriptions there was good agreement between the soil survey and the 137cs tracing combined with gully volume measurement approaches average erosion rates estimated using the russian version of the usle model were lower by a factor of six compared to the physically based approaches it may have been successful in assessing water erosion rates within inter rill areas and the discrepancy may provide insight into the contribution of tillage erosion we conclude that the usle model should be used only in combination with other techniques on arable fields where intensive rill erosion ephemeral gullying and mechanical translocation of soil take place

vegetation history climate change and human activities over the last 6200 years on the liupan mountains in the southwestern loess plateau in central china abstract fossil pollen data from tianchi lake on the liupan mountains in the loess plateau in china were used to investigate the interplay of climate change vegetation history and human activities the chronology of an 11 m long sediment core was controlled by 19 accelerator mass spectrometry radiocarbon dates on terrestrial plant macrofossils the pollen record shows a long term change from a closed canopy forest to open landscape over the last 6200 years from mixed deciduous coniferous forest dominated by betula quercus picea and pinus at 6200 2900 cal yr bp to transitional steppe forest co dominated by trees betula picea and pinus and herbs mostly artemisia at 2900 1100 cal yr bp and to open landscape dominated by artemisia and poaceae after 1100 cal yr bp this general pattern of vegetation change indicates a drying climate trend consistent with other independent climate records mostly from the monsoon region that show a weakening summer monsoon since the mid holocene the gradual increase in both poaceae pollen and microscopic charcoal since about 2000 cal yr bp and a sharp increase in poaceae but a decrease in charcoal at 1000 cal yr bp indicate two phases of human impacts on vegetation the results from pollen and charcoal analysis together with archaeological and historical evidence suggest that human activities over the last 2000 years have significantly accelerated deforestation that was initiated by a drying climate since the mid holocene

himalayan forelands palaeontological evidence for oligocene detrital deposits in the bugti hills balochistan pakistan in the southwestern sulaiman geological province balochistan pakistan terrestrial detri tal facies from the bugti hills region have yielded the richest tertiary vertebrate faunas to be found in asia thus far new fossils from five successive and distinct bone beds bridge the supposed oligocene sedimentary hiatus within the sulaiman geological province the lowermost continental levels of the previously described miocene chitarwata formation known as the bugti member are oligocene in age in the bugti area neither a mixture of heterochronic faunal elements nor endemism of any fauna is evident in this area additional microfaunal material from the bugti member constrains an oligocene age for the lower chitarwata formation in zinda pir northeast of the bugti hills this oligocene transition between the marine kirthar eocene and continental siwalik miocene deposits consists of a regressive fluvio deltaic system occupying a vast floodplain it represents an early stage molasse in the palaeo indus basin which drained western orogenic highlands resulting from the colli sion between the indian and eurasian plates

soil erosion in relation to climate change and vegetation cover over the past 2000 years as inferred from the tianchi lake in the chinese loess plateau abstract understanding the response of past soil erosion to climate change and human disturbances is quite essential for managing and preventing soil erosion in the future here we report a high resolution soil erosion sequence during the past 2000 years based on grain size data from a sediment core gs07a in tianchi lake in the chinese loess plateau these grain size data are analysed by end member modelling and further deciphered by detailed modern investigations of surface sediments surface soils and modern dust samples aided by published grain size distribution characteristics of different depositional provenances and processes six strong soil erosion periods including more than 20 serious soil erosion events are inferred at 150 300 ce 450 750 ce 900 1100 ce 1200 1400 ce 1650 1800 ce and 1950 2000 ce these soil erosion records correspond well with intensive flood events in downstream rivers and the neighbouring longxi area documented from the historical literature suggesting that regional high intensity rainfall or flood events are the main cause of soil erosion vegetation cover in the catchment also influenced soil erosion light vegetation cover aggravated soil erosion even in the periods with a low frequency of flooding while heavy cover reduced soil erosion even in the periods with a high frequency of flooding our results highlight the role of sustainable land use and vegetation restoration around the catchment in controlling soil erosion in the chinese loess plateau

the paleoclimatic record provided by eolian deposition in the deep sea the geologic history of wind the mineral component of pelagic sediment is brought to the deep sea by transport in the wind extraction and analysis of this dust allows estimation of the past aridity of the eolian source region via flux determinations and of the intensity of the transporting winds from grain size data these two parameters the grain size and mass flux of dust vary independently there are three significant sources of modern dust eastern and central asia northwest africa and arabia all in the northern hemisphere as the rainfall associated with the intertropical convergence zone is an effective barrier to southerly transport of dust the northern hemisphere is an order of magnitude more dusty than is the southern an asymmetry that has characterized most of the cenozoic eolian flux data show that most of the northern hemisphere was more arid during glacial maxima with 3 to 5 times as much dust transported during glacial stages than during interglacials only northwestern south america varied in the opposite sense the periodicity of quaternary variation in both eolian flux and eolian grain size data is strongly influenced by the milankovitch cycles of orbital variability wind intensities vary on a shorter time scale than the general 100 kyr cycles of glaciation and general aridity eolian grain sizes display forcing at precessional 19 and 23 kyr tilt 41 kyr and at approximately 30 kyr periodicities as a result the generalization that winds are uniformly stronger during glacial times is not valid whole cenozoic records show that the largest change in dust flux an order of magnitude increase occurred in the northern hemisphere and reflects continental drying associated with the late pliocene onset of northern hemisphere glaciation southern hemisphere eolian records show no sign of paleoclimatic changes in the late pliocene the most important change in cenozoic atmospheric circulation was a severalfold reduction in wind intensity that occurred at the time of the paleocene eocene boundary before then latest cretaceous and paleocene winds were essentially as strong as those of the late cenozoic this shift appears to be one of several climatic responses to a change in the nature and amount of global heat transport at about 55 ma

provenance of cenozoic sedimentary rocks from the sulaiman fold and thrust belt pakistan implications for the palaeogeography of the indus drainage system abstract the provenance of middle eocene to early miocene sedimentary rocks cropping out in the sulaiman fold and thrust belt has been determined examining the mineralogy bulk rock major and trace elements and nd sr isotopes the older 50 30 ma deposits are characterized by a mixed orogenic provenance with a major contribution from the karakorum and the tethyan belt c 80 as the 50 30 ma deposits have a provenance distinct from that of coeval subathu khojak and ghazij shallow marine formations of india and pakistan we propose that they were deposited as a distinct delta system that once fed the palaeo indus fan we document a major change in provenance that occurred before the early late oligocene transition at c 30 ma this change in provenance is marked by the appearance of chlorite and monazite and a shift toward more radiogenic nd sr isotopic compositions we interpret this change as the result of the exhumation and erosion of the proto higher himalaya the 30 15 ma sampled rocks are characterized by a major contribution from the tethyan belt and the higher himalayan crystallines 70 90 and a subordinate contribution 10 30 from the karakorum ophiolitic suture and trans himalaya as the end 0 values of our 30 15 ma samples are similar to those of the palaeo indus fan deposits we suggest that the 30 15 ma sedimentary rocks of the sulaiman fold and thrust belt were the fluvial onshore record of the indus fan other coeval deposits of india and pakistan recorded similar increasing exhumation of the higher himalaya range so that we postulate that these sedimentary rocks all derived from the palaeo indus drainage basin this would suggest that the modern indus drainage basin is no younger than 30 ma

influence of the temperature of co2 rich springs on their aluminium and rare earth element contents abstract in a set of thermomineral waters of about constant major element composition al fe and rare earth element ree concentrations are strongly dependent on the spring temperature al and ree concentrations are not affected by co2 degassing at the outflow of the waters al concentrations vary by one order of magnitude between the coldest and the hottest waters this change in total concentration is related to a change in the speciation fluoride complexes mainly alf03 are the dominant species in cold waters hydroxide or fluoro hydroxide complexes are more important at higher temperature ree patterns vary smoothly as a function of the atomic number from a regular decrease for the hottest water ce yb 30 to a large increase from ce to dy followed by a slight decrease from dy to yb for the coldest waters ce yb 0 3 ce dy 0 15

evaluating the hydrological component of the new catchment scale sediment delivery model lapsus d abstract physically based catchment scale sediment delivery models have become increasingly complex sophisticated and are suitable for a diverse range of environmental contexts however in their attempts to best represent the physical processes of erosion and deposition these models require large and detailed input datasets when such data are unavailable annual sediment yield models are relied upon however in this class of models widely available data such as daily precipitation and discharge are disregarded resulting in a reduction in temporal accuracy to fill this scientific and management gap the landscape evolution model lapsus was adapted lapsus d for a meso scale catchment to model sediment yield on a daily resolution the water balance component within the model enables the calibration of the model in terms of water discharge with measured daily discharge at the outlet this methodology is especially important when modeling sediment yield from catchments which are ungaged catchments in terms of sediment but where hydrological data are available as the simulation of sediment yield was the main objective of the study the calibration focused on peak discharge the focus on peak discharge provides insight into the capability of the model to generate route and deliver sediment at the outlet of a meso scale catchment lapsus d has daily temporal resolution and requires a 10 to 30 m pixel size dem soil map land use map and daily hydrological records precipitation and discharge in this paper we present the first assessment of the hydrological model performance and an analysis of the sensitivity of the model to input parameters our study site is a 23 km2 catchment in upper nysa szalona southwest poland with temperate climate results show that the model can reliably predict peak discharge which is expected in future studies to allow reliable estimates of sediment transport capacity redistribution and yield

elemental fractionation in lavas during post eruptive degassing evidence from trachytic lavas rishiri volcano japan abstract trachytic lavas of rishiri volcano northern japan show a peculiar geochemical variation across lava flow units samples collected systematically in a vertical cross section from a lava flow unit with a thickness of about 20 m are nearly homogeneous in major element compositions however some trace elements including li b and cs are considerably depleted in samples collected from the main part of the flow unit compared to those obtained from the surface of the lava flow clinker layer in particular cs content of the main flow unit is as low as 30 of the clinker layer 11b 10b ratios of samples from the main flow unit are also slightly lower than those of the clinker samples and the isotope compositions positively correlate with boron concentrations these geochemical variations cannot be explained by magmatic processes in magma chambers post eruptive weathering or alteration process rather we infer these systematics resulted from escape of these elements from the lava flow unit during post eruptive degassing vapor phases in which li b and cs dissolved are suggested to have been transported through veins formed in the main flow unit as fractures due to slight shearing along the flow planes after lava emplacement in the tanetomi lava only rocks of the clinker layer preserve original composition of magmas although they are porous and brownish due to extensive oxidization on the other hand rocks of the main flow unit do not retain original magma compositions although they are dense and grayish and seem to be much fresher compared to the clinkers a similar geochemical modification of lavas can occur in other volcanic systems especially for lavas consisting of relatively thick flow units

stratigraphic relations and lithologic variations in the jemez volcanic field new mexico over 100 radiometric dates and recent detailed geologic mapping allow some refinements of the stratigraphic relations of major units and generalization of temporal lithologic variations in the jemez volcanic field volcanism had begun in the area by about 16 5 ma with episodic eruptions of alkaline basalts by 13 ma alkaline volcanism had been replaced with eruptions of more voluminous olivine tholeiite high silica rhyolite derived from melts of lower crust also was erupting by about 13 ma basalt and high silica rhyolite continued to be erupted until about 7 and 6 ma respectively but effusions of dominantly andesitic differentiates of basalt that began as early as about 12 ma volumetrically overshadowed all other eruptive products between 10 and 7 ma from 7 to 3 ma the dominant erupted lithology was dacite which appears to have been generated by mixing of magmas whose compositions are approximated by earlier andesites and high silica rhyolites less than 4 3 ma volcanism was dominated by eruption of rhyolitic tuffs field relations geochemistry and dates specifically indicate the following with regards to stratigraphie relations 1 distinctions among basalt of chamisa mesa paliza canyon formation basalts and lobato basalt for other than geographic reasons are artificial basaltic volcanism was continuous in volcanic field from 13 to 7 ma 2 canovas canyon and bearhead rhyolites form a continuum of high silica rhyolite volcanism from 13 to 6 ma 3 hypabyssal and volcanic rocks of the cochiti mining district probably represent the exhumed interior of a keres group volcano s 4 temporal overlaps exist among the major stratigraphie groups which may imply some genetic relations and 5 the tewa group formation cerro rubio quartz latite may more appropriately be considered part of the tschicoma formation of the polvadera group preliminary analysis of hydrothermal alteration in the context of the volcanic stratigraphy suggests at least three distinct hydrothermal events have occurred in the volcanic field s history

uranium and rare earth elements in co2 rich waters from vals les bains france abstract waters from springs at vals les bains result from the mixing of a co2 rich highly mineralized water with dilute shallow subsurface water total content of dissolved species vary from 5 mmol 1 to 100 mmol 1 for many elements mixing of these waters is non linear non conservative and further water rock reactions take place the ph is controlled by co2 outgassing redox conditions are controlled by both the iron hydroxide siderite buffer and the introduction of oxygen with shallow subsurface waters among the major elements concentrations of ca mg mn fe are related to mixing co2 outgassing and carbonate precipitation uranium shows a complex behaviour controlled by carbonate complexing redox conditions mixing of waters and leaching from the rocks the 234 u 238 u activity ratio is near secular equilibrium in the more dilute waters dissolved rare earth element ree patterns are almost flat with a slight negative eu anomaly in the concentrated waters heavy rare earth elements gd yb hree are strongly enriched relative to light rare earth elements ce eu lree we relate the enrichment in hree to water chemistry and to complexing with carbonate species

an interpretation of the alteration assemblages at sulphur springs valles caldera new mexico sulphur springs located near the western edge of the valles caldera north central new mexico is the only vapor dominated surface manifestation of any significance found in the valles the percolating acid sulfate waters and fumarolic gases have leached and oxidized the country rock near the hot springs to a bleached wasteland the near surface mineral assemblages at 90 c are restricted to one and two phases occurring in contact with a variety of solutions and gases the conditions of local equilibrium at 90 g are approximately halotrichite alunogen log fo2 45 log fs2 12 ph 0 3 szomolnokite pyrite log fo2 46 log fs2 16 ph 0 8 alunite log fo2 50 log fs2 10 ph 1 2 kaolinite sulphur log fo2 53 log fs2 10 ph 1 2 log ak 0 0012 m log asio2 0 0033 m and pyrite log fo2 60 log fs2 19 ph 4 3 this study has demonstrated that local equilibrium is closely approached even under the low temperature and pressure conditions found near the surface

the behavior of rare earth elements in seawater precise determination of variations in the north pacific water column abstract we present new highly precise and accurate data for ten rare earth elements rees in two water column profiles and in bottom waters from three additional localities in the north pacific our results presented here and in an earlier publication indicate that the water column in the western north pacific is stratified with respect to the isotopic composition of nd as well as nd la sm nd and er la both the nd isotopic and the ree data show that ree transport is strongly influenced by horizontal advection even in the sluggish circulation of the pacific in general rees increase in concentration with depth at mid latitude they reach a maximum concentration at about 3000 m and then decrease to the bottom at high latitude heavy rees reach a maximum concentration near 3000 m whereas light rees continue to increase in concentration with depth the deep water maximum and bottom water depletion is interpreted as an advective feature resulting from the flow of a lower concentration of rees in antarctic bottom water under a higher concentration of rees in the north pacific concentrations of rees do not show a linear relationship with those of si indicating that the ree cycle is not directly coupled to that of the si cycle ree element ratios i e nd la correlate with hydrographie properties which suggests that major features of the ree patterns may be conserved during lateral transport comparison of our ree data to those in previously published reports on pacific seawater shows that the identification of ree distributions affected by advection is only made possible by the high precision analysis we developed for this study the ce concentration we observe is relatively constant over 200 4500 m depth at both sites where we have complete profiles this unique constancy of ce is in contrast to the contiguous rees la and nd which show substantial concentration variations with depth

basalts from mururoa fangataufa and gambier islands french polynesia geochemical dependence on the age of the lithosphere abstract basaltic volcanics from mururoa fangataufa and gambier islands which belong to the pitcairn island chain have been studied for trace elements and sr nd and pb isotopic composition while the trace element ratios remain constant the 87 sr 86 sr ratios range from 0 70292 to 0 70367 143 nd 144 nd ranges from 0 51303 to 0 51288 and the 206 pb 204 pb isotopic composition ranges from 18 99 to 19 62 these values which are clearly distinct from those of pitcairn basalts vary according to distance from the present hot spot and are correlated with the age of the underlying lithosphere it is suggested that the basalts studied were produced by variable degrees of partial melting from an oceanic lithospheric plate metasomatized by prior passage over the easter hot spot

chemical evolution of rare earth elements fractionation between colloidal and solution phases of filtered river water abstract within the dissolved fraction of connecticut river water there is large scale fractionation of rare earth elements between colloidal and solution phases colloidal particles carry a large part of the dissolved ree pool filtration through filters with progressively smaller pore size 0 45 0 22 and 0 025 m results in filtrates with lower absolute concentrations of ree and more fractionated compositions with decreasing pore size the filtrates have shale normalized abundances which become systematically more depleted in the lree relative to the hree hence both the solution and colloidal phases are significantly fractionated with respect to the dissolved fraction these conclusions are consistent with previous studies of ree in rivers estuaries and soils and with surface solution speciation models colloids play an important role in the aquatic geochemistry of rare earth elements they are responsible for the fractionation of ree during the estuarine removal of ree the removal of suspended and colloidal particles from river water leaves the solution phase of river water with compositions of ree as evolved as those of surface seawater hence the evolution of the composition of ree in river water and seawater is significantly influenced by colloid formation during chemical weathering on the continents

impact of monsoonal climatic change on holocene overbank flooding along sushui river middle reach of the yellow river china abstract in the semiarid loess regions slackwater deposition of overbank flooding over the piedmont alluvial plains was episodic and alternated with dust accumulation and soil formation throughout the holocene the records of past hydrological events are therefore preserved within the architecture of loess and soils and are protected from subsequent erosion and destruction several holocene loess soil sequences with the deposits of overbank flooding over the semiarid piedmont alluvial plains in the southeast part of the middle reaches of the yellow river drainage basin were investigated by field observation osl and c14 dating measurement of magnetic susceptibility particle size distribution and chemical elements this enables the reconstruction of a complete catalog of holocene overbank flooding events at a watershed scale and an investigation of hydrological response to monsoonal climatic change as well during the holocene there are six episodes of overbank flooding recorded over the alluvial plain the first occurred at 11 500 11 000 a bp i e the onset of the holocene the second took place at 9500 8500 a bp immediately before the mid holocene climatic optimum after an extended geomorphic stability and soil formation the third overbank flooding episode came at about 3620 3520 a bp i e the late stage of the mid holocene climatic optimum and the floodwater inundated and devastated a bronze age town of the xia culture built on the alluvial plain and therefore the town was abandoned for a period of ca 100 years during the late holocene the alluvial plain experienced three episodes of overbank flooding at 2420 2170 1860 1700 and 680 100 a bp respectively the occurrence of these overbank flooding episodes corresponds to the anomalous change in monsoonal climate in the middle reaches of the yellow river drainage basin when rapid climate change or climatic decline occurs during at least the last four episodes both extreme floods and droughts occurred and climate departed from its normal condition which was defined as a balanced change between the northwestern continental monsoon and southeastern maritime monsoon over time great floods occurred as a result of extreme rainstorms in summers caused by rare intensive meridianal airflows involving northwestward moving tropical cyclone systems from the pacific these results could be applied to improve our understanding of high resolution climatic change and of hydrological response to climatic change in the semiarid zones

lithofacies depositional environments regional biostratigraphy and age of the chitarwata formation in the bugti hills balochistan pakistan abstract the oligocene early miocene chitarwata formation records a critical interval of terrestrial sedimentation that predates the siwalik deposits on the potwar plateau of north central pakistan this oligocene early miocene time interval has long been considered as lacking in the entire indo pakistan region the chitarwata formation is widely exposed in the sulaiman range but has never been described in detail in the sulaiman lobe where the famous fossiliferous strata called bugti bone beds have been known for over a century and half the chitarwata formation represents coastal delta at the base and plain and fluvial environments at the top lithofacies and sedimentary structures of the chitarwata formation in the bugti area are described in detail and show a clearly distinct lithologic pattern different from that reported from the zinda pir area the chitarwata formation also records an important transition in the evolution of the drainage systems in the area during the late paleogene and early neogene this transition from the west flowing paleo indus fluvial system to the development of the ancestral indus drainage system may explain the numerous hiatuses that characterize the chitarwata formation the abundance of fossil mammals from the chitarwata and overlying vihowa formation in the bugti hills provides critical biochronologic information that sheds new light on biostratigraphic correlation with the zinda pir area and for the entire sulaiman range

characterisation of transport processes and sedimentary deposits by statistical end member mixing analysis of terrestrial sediments in the donggi cona lake catchment ne tibetan plateau abstract unmixing of grain size distributions with multivariate statistical analysis gives indications of the main sediment transport processes and related environmental conditions in an area we performed end member mixing analysis emma of sedimentological data from 912 terrestrial sediment samples collected in the donggi cona catchment north eastern tibetan plateau up to the present this is the largest sedimentological dataset on the tibetan plateau emma resulted in the characterisation of three end members that explain 88 of the variance within the dataset the end members all represent aeolian deposits the first end member em 1 represents very fine dune sediments that were deflated from a former lake system em 2 represents medium sand deposits that were blown out from playa and alluvial fan sediments em 3 represents fine loess like sediments mainly found at higher elevations different transformations adding of a fourth end member and adding of up to 200 loess samples do not change the composition of the end members demonstrating the robustness of the model emma allows the synchronous interpretation of very large datasets resulting in a general characterisation of sediment transport in a particular area performing emma on the dataset demonstrates the importance of aeolian transport in this part of the world

holocene erosion triggered by climate change in the central loess plateau of china abstract understanding changes in holocene erosion is essential for predicting soil erosion in the future however the quantitative response of natural erosion to holocene climate change is limited for the loess plateau of china in this study two soil profiles were investigated on the luochuan and yanchang sites in the central loess plateau of china and four climate indicators i e magnetic susceptibility calcium carbonate content total organic carbon content and clay content

alteration of basaltic glasses from north central british columbia canada abstract evidence of palagonitization glass replacement by poorly crystallized clay like material is seen on all glasses studied from three pleistocene subglacial volcanoes in north central british columbia canada samples from foreset breccias of tuya butte are more highly palagonitized than those from the tephra cones of ash mountain and southern tuya extensive palagonitization is generally associated with authigenic mineralization clays zeolites palagonite composition varies widely relative to glass composition and palagonite can be broadly categorized as either high al or low al depending on whether al was retained or lost to aqueous solutions during palagonitization the lowest al palagonites are those from the foreset breccias of tuya butte loss of al during palagonitization is related to closed system alteration including precipitation of aluminosilicate authigenic cements low initial ph is suggested for al depletion consistent with the behavior of ni co and cr which are retained in high al and depleted in low al palagonite microenvironment appears to be more influential than macroenvironment in determining the composition of palagonite palagonite rinds are compositionally zoned generally becoming progressively higher in al and ca and lower in fe and mg towards the innermost later formed portions of the rinds this apparently reflects changing solution composition increasing ph with time compositional zoning does not change the overall stoichiometry of palagonite which resembles smectite clay mineral paragenesis is related to the ca content of the palagonite with partial replacement of palagonite by smectite fe saponite occurring when ca is retained in the rind this replacement phenomenon occurs prior to zeolitization no such replacement clay occurs with low ca palagonite but a late stage nontronite film overgrows zeolite phillipsite is the first zeolite formed followed by chabazite analcime and calcite occur in the most highly palagonitized samples mass balance considerations indicate higher mass loss where palagonitization has not proceeded to the point where zeolite solubility limits were attained in the local solution zeolites occur in closed system conditions low flow rates where little net system mass loss or gain has occurred the colloidal nature of palagonite allows the effective adsorption of rb cs sr ba and rees

hydrothermal iron rich deposits from the teahitia mehitia and macdonald hot spot areas southwest pacific abstract during cruise so 47 of r v sonne iron oxyhydroxide crusts of restricted extent were recovered from teahitia and moua pihaa seamounts in the teahitia mehetia hot spot area and from macdonald seamount in the macdonald hot spot area the crusts show complex layering and incorporate volcanic ash layers they consist of goethite feldspar and pyroxene and display low contents of transition elements apart from fe it is believed that the crusts were deposited from relatively low temperature hydrothermal fluids these low temperatures preclude the formation of sulphide deposits the type of hydrothermal mineral recovered may be a function of the thermal regime of the system and the elevation which controls the pressure of the venting fluids the shallower depths of these seamounts compared to the axes of mid ocean ridges may therefore be responsible for the style of mineralization initially magmatic vapours migrating upwards through the hot spot volcano are thought to be absorbed into seawater at comparatively shallow levels to deposit sulphide minerals within the volcanic pile the fe oxyhydroxide deposits are the residual low temperature deposits formed when the spent hydrothermal fluid reached the crest of the seamount these deposits therefore differ fundamentally from those found at the crest of mid ocean ridges where sulphide mounds are deposited directly upon interaction of the boiling hydrothermal fluid with seawater the discovery of hydrothermal iron oxyhydroxide crusts in these two hot spot areas is only the second such finding after loihi seamount southeast of hawaii

faunal turnovers of palaeogene mammals from the mongolian plateau most orders and many families of modern mammals were established during the palaeogene mammalian evolution during this period of time has been correlated with global climatic events1 2 3 4 although the timing mode and scale of such a climate evolution link remain debatable1 5 6 the palaeogene global climate was step punctuated by a warming across the palaeocene eocene boundary about 55 myr ago and a cool off throughout the late eocene and early oligocene epochs1 2 7 8 9 10 the most severe cooling was at 33 5 myr slightly after the eocene oligocene boundary and was characterized by a drop in the mean annual temperature and by changes in vegetation from eocene dense forests to oligocene more open country5 here we analyse 33 palaeogene mammal faunas from the mongolian plateau of china and mongolia there is a distinct pattern of faunal turnovers perissodactyl dominant faunas of the eocene were abruptly replaced by rodent lagomorph dominant faunas of the oligocene we interpret the turnovers as having been effected by global climatic shifts and name the prominent biotic reorganization across the eocene oligocene boundary the mongolian remodelling which correlates to the european grande coupure

evidence of an early alteration process driven by magmatic fluid in mururoa volcano evidence for a deuteric alteration process induced by a magmatic fluid has been found in the feeder zone of the mururoa volcano french polynesia within the dikes where basaltic glass does not show any evidence of pervasive alteration vesicles are filled with dioctahedral smectites and calcite while olivine phenocrysts are replaced by dioctahedral smectites ankerite and calcite the 13c signature of carbonates the carbon and h2o content of the whole rocks and their impoverishment in deuterium are compatible with the presence of magmatic co2 during the crystallization of intruding lavas and exclude contamination by seawater mass balance calculations on selected thin sections photographs of partly filled up vesicles and replaced olivine crystals constrain assuming a closed system interaction the chemical composition of the initial fluid and the respective amounts of the initial solid phases involved in the alteration process thermodynamic modelings using the eq3 6 software package correctly predict the mineralogic chemical and isotopic exchanges accompanying alteration thus validating the closed system assumption the model which allows prediction of the influence of co2 on the alteration products shows that above a 0 25 co2 mole fraction in the initial fluid the alteration is entirely controlled by the chemical composition of the initial solid phases the presence of co2 implies the precipitation of dioctahedral smectites and carbonates instead of the magnesian smectites commonly observed in co2 free systems the mururoa feeder zone shows alteration features typical of a closed system interaction between the basaltic rock and a magmatic fluid in which seawater did not take part

eocene krabi basin southern thailand paleontology and magnetostratigraphy we present the magnetostratigraphy of the late eocene krabi section from the krabi basin thailand the investigated section is about 105 m thick and consists of red and yellow siltstones sandstones gray claystones lignites and limestones we collected 86 samples at 43 different stratigraphic levels from the 105 m thick section the samples yielded a paleomagnetic direction and paleomagnetic analyses give favorable demagnetization behaviors two magnetic components can be isolated rock magnetic experiments show that the natural remanent magnetization generally results from the presence of titanomagnetite the first component has roughly the direction of the present day field the second component displays only reversed polarity with a mean direction declination 192 34 inclination 15 5 n 71 95 4 7 k 14 after bedding correction mammalian biostratigraphy indicates a late eocene age correlation to the geomagnetic polarity time scale relies on biostratigraphic data previously proposed for the fauna found in the same section these correlations have been achieved by comparing variations in the sedimentation rate derived from the alternative correlation the proposed correlation puts the krabi section in chron c12r or chron c13r this suggests sedimentation rates of 4 9 and 9 4 cm k y respectively this correlation suggests that the krabi section is older than 31 ma and younger than 34 ma

changes in erosion patterns during the holocene in a currently treeless subalpine catchment inferred from lake sediment geochemistry lake anterne 2063 m a s l nw french alps the role of climate and human activities a high resolution sedimentological and geochemical study was performed on a 20 m long core from the alpine lake anterne 2063 m a s l nw french alps spanning the last 10 ka sedimentation is mainly of minerogenic origin the organic matter quantity toc as well as its quality hydrogen hi and oxygen oi indices both indicate the progressive onset and subsequent stabilization of vegetation cover in the catchment from 9950 to 5550 cal bp during this phase the pedogenic process of carbonate dissolution is marked by a decrease in the calcium content in the sediment record between 7850 and 5550 cal bp very low manganese concentrations suggest anoxic conditions in the bottom water of lake anterne these are caused by a relatively high organic matter terrestrial and lacustrine content a low flood frequency and longer summer stratification triggered by warmer conditions from 5550 cal bp a decrease in toc stabilization of hi and higher sedimentation rates together reflect increased erosion rates of leptosols and developed soils probably due to a colder and wetter climate then three periods of important soil destabilization are marked by an increased frequency and thickness of flood deposits during the bronze age and by increases in topsoil erosion relative to leptosols hi increases during the late iron age roman period and the medieval periods these periods are also characterized by higher sedimentation rates according to palynological data human impact deforestation and or pasturing activity probably triggered these periods of increased soil erosion

lithostratigraphy of the state 2 14 borehole salton sea scientific drilling project sedimentary rocks from the california state 2 14 research borehole of the salton sea scientific drilling project located in the imperial valley of southern california were deposited in the continental basin of the salton trough lacustrine shale and siltstone are the dominant lithologies sandstones were deposited in lake margin meander channel fill and lacustrine delta environments framework modal clast compositions of the sandstones indicate a dominant colorado river provenance rare pebbly mudstones were deposited as storm induced debris flows primary depositional structures in the sediments are commonly disrupted by seismic disturbances nonmarine gastropods and ostrocods are relatively uncommon and occurrences of stratabound sulfides suggest periods of brackish water conditions bedded anhydrite and centimeter scale mudcracks record intervals of dessication the state 2 14 sedimentary rocks are interpreted as the basinward facies of the borrego and brawley formations which range from pliocene to pleistocene in age

an experimental investigation of high temperature interactions between seawater and rhyolite andesite basalt and peridotite natural seawater was allowed to react with rhyolite andesite basalt and peridotite at 200 500 c and 1 000 bars at water rock mass ratios of 5 and 50 in order to investigate the effects of rock type water rock ratio and temperature on solution chemistry and alteration mineralogy the results indicate that interactions of seawater with various igneous rocks are similar in the production of a hydrous mg silicate and anhydrite as major alteration products fluids involved in the interactions lose mg to alteration phases while leaching fe mn and si from the rocks the ph of the solutions is primarily controlled by mg oh silicate formation and therefore varies with mg and si concentration of the system other reactions which involve mg such as mg ca exchange or which produce free h cause major differences in fluid chemistry between different seawater rock systems high water rock ratio systems 50 1 are generally more acidic and more efficient in leaching than low ratio systems 5 1 due to relatively more seawater mg available for mgsilicate production the experiments show that large scale seawater rock interaction could exert considerable control on the chemistry of seawater as well as producing large bodies of altered rock with associated ore deposits

rare earth element systematics in hydrothermal fluids abstract rare earth element concentrations have been measured in hydrothermal solutions from geothermal fields in italy dominica valles caldera salton sea and the mid atlantic ridge the measured abundances show that hydrothermal activity is not expected to affect the ree balance of either continental or oceanic rocks the ree enrichment of the solutions increases when the ph decreases high temperature solutions 230 c percolating through different rock types may show similar ree patterns

a review of fossil rhinoceroses from the neogene of myanmar with description of new specimens from the irrawaddy sediments abstract four genera and one indeterminate genus total eight species of fossil rhinoceroses mammalia perissodactyla rhinocerotidae are recognized from the neogene of central myanmar in the early miocene most area of central myanmar were under the shallow marine condition and no rhinocerotid remain has been documented yet during the middle to late miocene the rhinocerotid remains are commonly found and are represented by diceratherium naricum brachypotherium perimense brachypotherium fatehjangense and an indeterminate rhinocerotid in the latest miocene these archaic rhinoceroses became extinct in the late neogene the extant genera rhinoceros late miocene to pleistocene and dicerorhinus plio pleistocene first appeared in myanmar they appear to have dispersed to the island southeast asia from the continental asia during the early pleistocene to middle pleistocene when the eustatic sea level became low remarkably

chemical evolution of mid ocean ridge hot springs abstract chemical analyses yielding elemental concentrations of major and minor elements of four hot springs on the east pacific rise at 21 n and 10 hot springs from the southern trough of the guaymas basin gulf of california provide a basis for thermodynamic modeling of conductive cooling of the hydrothermal endmembers mixing of the hydrothermal endmember with seawater and reaction of an epr type fluid with sediment of bulk chemical composition corresponding to unaltered sediment from dsdp hole 477 in the guaymas basin results of the calculations indicate that conductive cooling of endmember fluids within closed chimneys and conduits accounts for the solution composition of one vent on the east pacific rise and several vents in guaymas basin mixing of the hydrothermal fluids with seawater yields a prediction of mineral assemblages closely approximating those observed in samples of chimneys from the east pacific rise and drill cores in guaymas basin the hypothesis that guaymas basin hydrothermal fluids result from interaction of an epr type fluid with sediment cover in guaymas basin is supported by calculations which predict an increase in ph to a value similar to guaymas basin fluids an order of magnitude decrease in metal concentrations and an excellent agreement between predicted mineral assemblages as a function of extent of interaction with sediment and observed mineral assemblage distribution with depth

behavior of rare earth elements in groundwater during flow and mixing in fractured rock aquifers an example from the dandenong ranges southeast australia a previously defined flow system is used to investigate ree behavior at different stages along groundwater flow paths in fractured basalt and sedimentary aquifers results from this study indicate that ree concentrations and patterns predominantly reflect different types and rates of reactions taking place to those controlling major ion chemistry in areas where recharge is through sediments ree concentrations are high nd 8 62 31 61 ng l and localised processes such as source heterogeneity control ree patterns and concentrations increased concentrations of rees in these groundwaters where ph 6 1 is a result of early stage ree mobilisation in the flow system in contrast where groundwater recharges through basalt ree concentrations are low nd 2 40 4 75 ng l and ree concentrations are relatively constant along groundwater flow paths indicating steady state conditions groundwater from both the sediment and basalt aquifer systems flows into the local discharge area in contrast to tds contents and major ion ratios groundwater from the discharge area has ree concentrations nd 1 84 4 18 ng l and patterns that reflect a larger component of flow from the basalt aquifer lower ree concentrations of groundwater from the regional sedimentary aquifer may result from progressive ree sorption or co precipitation as indicated by an increase in y ho cl cn ratios and hree enrichment for groundwater with ph not vert similar 7 1 due to greater abundances of hree vs lree dicarbonato complexes

low temperature alteration of basalt by interstitial seawater mururoa french polynesia chemical and isotopic analysis of interstitial fluids and secondary phases in two drill cores from the volcanic pile of the mururoa atoll french polynesia permits documentation of the lowtemperature alteration by seawater of basalt and secondary minerals as a function of rock water ratio r w up to 110 g l as r w increases in this system up to 70 g l the interstitial waters exhibit an almost total removal of mg and k a net decrease of ph and eh a marked enrichment in ca sr and si and depletion of 18o and d with further increases in r w above 70 g l a reversal of mg ca exchange is observed mg accumulates in the fluid while ca is removed in addition the enrichment of 18o and d is also observed in the fluids at these high r w these chemical and isotopic reversals are shown to result from the transformation of early precipitated mg rich saponite into ca na saponite chemical and isotopic reactions take place at two separate solid solution interfaces 1 1 an interface at the surface of the fresh basalt that leads to the formation of a hydrated amorphous layer which progressively crystallizes into clay and 2 2 a second interface between the interstitial bulk fluid and the resultant clay layer consequently geochemical codes which fail to account for both aqueous diffusion in altered layers and the existence of multiple reaction interfaces cannot accurately describe alteration at high rock water ratios

hydrothermal alteration in oceanic ridge volcanics a detailed study at the galapagos fossil hydrothermal field abstract the galapagos fossil hydrothermal field is composed of altered oceanic crust and extinct hydrothermal vents within the eastern galapagos rift between 85 49 w and 85 55 w the discharge zone of the hydrothermal system is revealed along scarps thus providing an opportunity to examine the uppermost mineralized and highly altered interior parts of the crust altered rocks collected in situ by the submersible alvin show complex concentric alteration zones microsamples of individual zones have been analysed for major minor trace elements and strontium isotopes in order to describe the complex compositional details of the hydrothermal alteration interlayered chlorite smectite and chlorite with disequilibrium compositions dominate the secondary mineralogy as replacement phases of primary glass and acicular pyroxene phenocrysts and matrix grains of plagioclase are unaffected during alteration using a modification of the gresens equation we demonstrate that the trivalent rare earth elements rees are relatively immobile and calculate degrees of enrichment and depletion in other elements strontium isotopic ratios increase as sr concentrations decrease from least altered cores to most altered rims and cross cutting veins in individual samples and can be modeled by open system behaviour under low fluid rock ratio

lithostratigraphy and vertebrate biostratigraphy of the early miocene himalayan foreland zinda pir dome pakistan abstract deposits in the sulaiman foothills and zinda pir dome in west central pakistan provide new insight into the critical early miocene record of himalayan foreland sedimentation and paleobiology the chitarwata formation which underlies the vihowa formation in the sulaiman foothills predates the siwalik deposits on the potwar plateau of north central pakistan and provides a record of mammals spanning the interval between the early miocene bugti fauna and middle miocene to pleistocene siwalik faunas siwalik deposits on the potwar plateau are no older than middle miocene they represent fluvial environments in contrast the chitarwata and lower vihowa formations in the zinda pir dome represent coastal delta plain and fluvial environments respectively biostratigraphic information from the chitarwata formation coupled with paleomagnetic data reported by friedman et al 1992 from coincident strata suggest that coastal environments persisted in the area of the sulaiman foothills until about 18 6 ma when they were replaced by fluvial environments probably representing the ancestral indus river system apparently during the early miocene when sediments of the chitarwata formation were accumulating on the western portion of the himalayan foreland basin much of the area of the potwar plateau to the north was being eroded the overlying vihowa formation along with the relatively contemporaneous kamlial formation on the potwar plateau represent the appearance of widespread terrestrial sedimentation in the himalayan foreland basin

hydrothermal minerals and alteration rates at surtsey volcano iceland the volcanic island surtsey off the south coast of iceland was created by volcanic activity in 1963 1967 core from a 181 m deep hole extending 123 m below sea level shows the results of 12 yr of hydrothermal alteration of basaltic tephra the primary cause of heating of the tephra and of development of the hydrothermal system was the intrusion of dikes below sea level at present the hottest part of the hole at a maximum temperature of 150 c is cooling at 0 9 c per year palagonitization of sideromelane glass a dominant constituent of the tephra is an important alteration process that is strongly temperature dependent the rate doubling for every 12 c increase at 60 c 90 is palagonitized above 120 c olivine crystals are replaced on their edges by nontronite the thickness of clay doubles for each 8 c increase ten hydrothermal minerals have crystallized in the tephra at 25 to 150 c the dominant species are smectite nontronite analcite phillipsite and tobermorite the primary clay species of palagonite is probably nontronite other minerals are halite opal calcite chabazite xonotlite anhydrite and gypsum no major differences in mineral occurrence are noted above and below sea level but phillipsite and tobermorite tend to grow larger below sea level even at the same temperature analcite appears at lower temperature 55 c above sea level than below sea level 75 c anhydrite is most abundant deep in the hole where inflowing cool sea water precipitated sulfate due to reduced sulfate solubility at higher temperatures

drilling the snake pit hydrothermal sulfide deposit on the mid atlantic ridge lat 23 sup 0 22 n a major high temperature hydrothermal area has been discovered in the mid atlantic ridge rift valley about 25 km south of the kane fracture zone the vent field consists of a wide area 40 000 m sup 2 of dark hydrothermal deposits numerous sulfide chimneys and mounds some up to 11 m high and high temperature black smoker vents ten shallow holes the first ever drilled in an active submarine hydrothermal area recovered friable unconsolidated fe cu fe and zn sulfides and several large fragments of massive sulfide mainly chalcopyrite from the locally thick 13 m hydrothermal deposits the vents are also associated with an unusual biological community of smaller more mobile organisms than reported from the east pacific rise

extraordinary floods related to the climatic event at 4200 a bp on the qishuihe river middle reaches of the yellow river china abstract palaeo hydrological study was carried out in the qishuihe river valley in the middle reaches of the yellow river several bedsets of flood slackwater deposit were identified in the holocene loess soil sequences on the riverbanks they were differentiated from aeolian loess and soils by the parallel and waving beddings and the distinctive stratigraphic breaks separating individual palaeoflood events chronology of the flood events was established by osl dating checked by archaeological identification of the anthropogenic remains retrieved from the sequences the results show that successive floods occurred between 4300 and 4000 a bp in association with the abrupt climatic event of 4200 a bp these overbank floods had the riverbank settlement inundated repeatedly another series of extraordinary floods occurred between 3200 and 3000 a bp when monsoonal climate shifted from the mid holocene climatic optimum toward late holocene dry conditions the climatic event of 4200 a bp and the climatic decline at 3100 a bp were believed to be characterized by droughts previously this work provides solid evidence that both severe droughts and extreme floods were parts of the climatic variability during abrupt climatic event and climatic decline in the semi arid to sub humid zones over the world

trace element mobility during sub seafloor alteration of basaltic glass from ocean drilling program site 953 off gran canaria trace element concentrations of altered basaltic glass shards layer silicates and zeolites in volcaniclastic sediments drilled in the volcanic apron northeast of gran canaria during ocean drilling program odp leg 157 document variable element mobilities during low temperature alteration processes in a marine environment clay minerals saponite montmorillonite smectite replacing volcanic glass particles are enriched in transition metals and rare earth elements ree the degree of retention of ree within the alteration products of the basaltic glass is correlated with the field strength of the cations the high field strength elements are preferentially retained or enriched in the alteration products by sorption through clay minerals most trace elements are enriched in a boundary layer close to the interface mineral altered glass this boundary layer has a key function for the physico chemical conditions of the subsequent alteration process by providing a large reactive surface and by lowering the fluid permeability the release of most elements is buffered by incorporation into secondary precipitates sodium rich zeolites phillipsite fe and mn oxides as shown by calculated distribution coefficients between altered glasses and authigenic minerals chemical fluxes change from an open to a closed system behavior during prograde low temperature alteration of volcaniclastic sediments with no significant trace metal flux from the sediment to the water column

geochemical and petrographic characteristics of impactites and cretaceous target rocks from the yaxcopoil 1 borehole chicxulub impact structure mexico implications for target composition we present major and trace element data as well as petrographic observations for impactites suevitic groundmass bulk suevite and melt rock particles and target lithologies including cretaceous anhydrite dolomite argillaceous limestone and oil shale from the yaxcopoil 1 borehole chixculub impact structure the suevitic groundmass and bulk suevite have similar compositions largely representing mixtures of carbonate and silicate components the latter are dominated by melt rock particles trace element data indicate that dolomitic rocks represented a significant target component that became incorporated into the suevites in contrast major elements indicate a strong calcitic component in the impactites the siliceous end member requires a mafic component in order to explain the low sio2 content multicomponent mixing of various target rocks the high alteration state and dilution by carbonate complicate the determination of primary melt particle compositions however two overlapping compositional groups can be discerned a high ba low ta group and a high fe high zn and high hf group cretaceous dolomitic rocks argillaceous limestone and shale are typically enriched in u as br and sb whereas anhydrite contains high sr contents the oil shale samples have abundances that are similar to the north american shale composite nasc but with a comparatively high u content clastic sedimentary rocks are characterized by relatively high th hf zr as and sb abundances petrographic observations indicate that the cretaceous rocks in the yaxcopoil 1 drill core likely register a multistage deformation history that spans the period from pre to post impact contrary to previous studies that claimed evidence for the presence of impact melt breccia injection veins we have found no evidence in our samples from a depth of 1347 1348 m for the presence of melt breccia we favor that clastic veinlets occur in a sheared and altered zone that underwent intense diagenetic overprint prior to the impact event

hydrothermal alteration at mururoa atoll french polynesia abstract petrological study of altered aerial basaltic flows submarine pillow lavas and oceanitic basalts of a rift zone sampled in two drill cores in the mururoa atoll viviane 1000 m depth fuchsia 550 m depth shows that during hydrothermal alteration processes the secondary clay minerals evolve the following three different trends controlled by permeability of the rocks and by rock fluid interaction mg saponite al saponite and al montmorillonite in the basaltic pillow lavas first celadonite saponite assemblage crystallizes in fresh glass rich rocks in altered and brecciated rocks the latter mineral assemblage is followed by fe saponite and mg saponite in breccias the glass is replaced by fe saponite the residual voids are sealed by zeolites mainly phillipsite apophyllite or gypsum indicating an upper temperature limit of 65 c in the aerial basaltic flows massive rocks are affected by celadonite and random mixed layer chlorite saponite crystallizations in the strongly altered rocks veined or brecciated the primary minerals and glass are partly replaced by al saponites and locally by chabazite the same al saponite fills up the veins and constitutes the major part of the cement as rock fluid interaction increases the si al and ca content in the solution increases inducing the late precipitation of aluminous smectite and chabazite in the oceanitic basalts sampled in the rift zone massive rocks are affected by crystallization of secondary clay minerals which is governed by local equilibrium femg clay minerals talc mg saponite celadonite partly replace the olivine phenocrysts and al saponite replaces the glass in veined and brecciated rocks the paragenesis is dioctahedral al smectite silica amorphous for a temperature range 2 content in the solution

alteration in the irdp drill hole compared with other drill holes in iceland the overall alteration pattern in the drill hole at reydarfjordur is very similar to alteration patterns observed in icelandic geothermal areas and in low grade metamorphosed basalts in deep crustal sections elsewhere in iceland however more detail is obtained by the study of the irdp drill core than by study of drill cuttings sampled in previous drill holes in iceland a comparatively high fossil thermal gradient is obtained at reydarfjordur by a combination of mineral stability data and the observed occurence of secondary minerals this high gradient is consistent with the measured dike dilation at the drill site and the location of the drill site adjacent to a central volcano

intra tooth study of modern rhinoceros enamel δ18o is the difference between phosphate and carbonate δ18o a sound diagenetic test abstract the carbonate and phosphate oxygen isotopic difference 18 o c p has been suggested as a test for diagenetic alteration of isotope values in fossil apatite samples the generally accepted 18 o c p value for well preserved enamel is 9 only a few studies have focussed on the potential natural variability of this difference in modern and fossil mammal teeth the aim of this study is to document the value of the carbonate phosphate oxygen isotopic fractionation factor co3 po4 at an intra tooth level we measured the enamel phosphate and carbonate oxygen isotopic compositions of two upper molars m1 and m2 of rhinoceros unicornis following a sequence from the apex to the cervix of the crown the average co3 po4 is 1 0082 0 0007 the mean value of the 18 o c p difference is 8 4 0 7 close to the literature values given for other species however we also show that the values of the 18 o c p difference for r unicornis upper molars can vary on a 2 range in the same tooth we develop a physiological model to explain the origin of inter species and intra tooth 18 o c p difference and to understand their implications on the status of 18 o c p as a tool for identifying diagenesis the results imply that by increasing the dataset of phosphate and carbonate oxygen isotopic composition for modern mammal species we will be able to define a maximal and precise envelope corresponding to the well preserved samples and to check a possible species dependence on the 18 o c 18 o p relationship

flood stratigraphies in lake sediments a review abstract records of the frequency and magnitude of floods are needed on centennial or millennial timescales to place increases in their occurrence and intensity into a longer term context than is available from gauged river flow and historical records recent research has highlighted the potential for lake sediment sequences to act as a relatively untapped archive of high magnitude floods over these longer timescales abyssal lake sediments can record past floods in the form of coarser grained laminations that reflect the capacity for river flows with greater hydrodynamic energy to transport larger particles into the lake this paper presents a framework for investigating flood stratigraphies in lakes by reviewing the conditioning mechanisms in the lake and catchment outlining the key analytical techniques used to recover flood records and highlighting the importance of appropriate field site and methodology selection the processes of sediment movement from watershed to lake bed are complex meaning relationships between measureable sedimentary characteristics and associated river discharge are not always clear stratigraphical palaeoflood records are all affected to some degree by catchment conditioning fluvial connectivity sequencing of high flows delta dynamics as well as within lake processes including river plume dispersal sediment focussing re suspension and trapping efficiency with regard to analytical techniques the potential for direct e g laser granulometry and indirect e g geochemical elemental ratios measurements of particle size to reflect variations in river discharge is confirmed we recommend care when interpreting fine resolution geochemical data acquired via micro scale x ray fluorescence xrf core scanning due to variable down core water and organic matter content altering x ray attenuation we also recommend accounting for changes in sediment supply through time as new or differing sources of sediment release may affect the hydrodynamic relationship between particle size and or geochemistry with stream power where these processes are considered and suitable dating control is obtained discrete historical floods can be identified and characterised using palaeolimnological evidence we outline a protocol for selecting suitable lakes and coring sites that integrates environmental setting sediment transfer processes and depositional mechanisms to act as a rapid reference for future research into lacustrine palaeoflood records we also present an interpretational protocol illustrating the analytical techniques available to palaeoflood researchers to demonstrate their utility we review five case studies of palaeoflood reconstructions from lakes in geographically varied regions these show how lakes of different sizes and geomorphological contexts can produce comprehensive palaeoflood records these were achieved by consistently applying site validated direct and proxy grain size measurements well established chronologies validation of the proxy process interpretation and calibration of the palaeoflood record against instrumental or historical records

late quaternary dust flow on the chinese loess plateau abstract the dust flux of over 25 g cm2 103yr was reached in the central part of the chinese loess plateau during the last glacial maximum this is more than three times higher than during the last interglacial and early glacial time the grain size of the pleniglacial dust reached a peak shortly after 20 000 years ago and testifies to the occurrence of strong winds and frequent dust storms

element redistribution during hydrothermal alteration of rhyolite in an active geothermal system yellowstone drill cores y 7 and y 8 abstract hydrothermal alteration of the 0 54 ma biscuit basin rhyolite flow in yellowstone drill cores y 7 and y 8 has involved significant changes in ti normalized whole rock concentrations of li mg ca na k mn rb sr sb cs ba and u whereas such changes have generally not occurred for al fe sc co y zr ree hf ta and th the relatively mobile elements have been redistributed over distances from 2 5 cm to more than 10 100 m and are associated mainly with zeolites and clays in thoroughly altered samples average whole rock changes in ti normalized mass range from about 0 5 17 g kg 9 49 for major elements and 0 1 280 mg kg 19 4260 for minor and trace elements compositional changes correlate with hydrothermal mineralogy the relatively immobile elements have been redistributed over a distance of at least 10 100 m but less than 2 5 cm and are associated mainly with clays in thoroughly altered samples addition of sio2 ranges from 110 890 g kg in samples where porosity has been thoroughly sealed by silica deposition thermal water is not in oxygen isotopic equilibrium with any primary or secondary phases analyzed except calcite modest depletions of 18o 1 2 due to exchange with thermal water apparently have occurred in y 8 plagioclase and obsidian oxygen isotope ratios in obsidian replacing smectite and in veinlet celadonite and cristobalite suggest that these phases precipitated from water locally enriched in 18o up to 8 heavier than present thermal water the minimum integrated water rock mass ratio in y 7 and y 8 is 103 104 assuming advective transport

behaviour of rare earth elements during seawater basalt interactions in the mururoa massif abstract the rare earth elements ree were analysed in the interstitial fluids in the basalts and in the alteration products clays and zeolites of mururoa atoll volcanic rocks french polynesia in order to investigate ree behaviour during seawater basalt interactions at low temperature the ree distribution coefficients between fluids and secondary products were calculated using the eq3 6 geochemical code the reversible irreversible character of the ree entrapment in secondary products was tested the ree concentrations in the clays are close to that of basalt the concentrations in zeolites are 10 times lower comparison of measured and modeled concentrations in solutions favours the irreversible incorporation assumption the affinity of the ree for the secondary products is shown to be high the calculated distribution coefficients range from 3 105 for lu and eu to 107 for ce in clays and from 104 to 7 105 in zeolites the distribution coefficients exhibit a progressive decrease from la to lu this behaviour is related to the greater stability of hree complexes relative to lree complexes in solution under reducing conditions in the interstitial fluids eh down to 500 mv eu undergoes reduction to the mobile eu ii this enhanced mobility is reflected by eu distribution coefficient being lower than those of adjacent ree the distribution coefficient of ce is higher as ce is trivalent in the fluids fractionation from the other trivalent ree was unexpected the calculated distribution coefficients of ree are lower in zeolites than in clays and this can be related to the spatial distribution and paragenesis of the secondary phases the dissolution of the basalt promotes the precipitation of clays at the basalt fluid interface and of zeolites in the bulk solution the ree released by dissolution are incorporated into the clays and further uptake occurs in zeolites for the ree left in solution

a model for linking grain size component to lake level status of a modern clastic lake abstract grain size distributions of fluvial eolian and marine sediments were explicated decades ago for lake sediments however there is still great uncertainty in explaining the genesis of grain size components due to the inherent complexity of their polymodal distributions in this study the grain size components of the surface sediments of daihai lake inner mongolia were partitioned using a lognormal distribution function and the relationship between the identity of each component and the specific sedimentary environment was investigated the data indicate that the modern clastic sediments of daihai lake contain five distinct unimodal grain size distributions representing five grain size components each of the components retains its identity including modal size manner of transportation and environment of deposition although the relative percentage varies with the hydraulic condition throughout the lake these components are specified from fine to coarse modes as long term suspension clay offshore suspension fine silt and medium to coarse silt and nearshore suspension fine sand and saltation medium sand the percentage of the components interpreted as an indication of nearshore environments displays a negative correlation with water depth across the modern lakebed suggesting a model for linking the nearshore components in sediment cores to the lake level status in the geological past the model was applied to a sediment core from the lake where high percentages of the nearshore components in the core sediments were correlated with low regional precipitations reconstructed on the pollen profile of the same core the coincidences between two independent proxies do not only demonstrate the validity of lognormal distribution function in partitioning polymodal sediments but also reveals the potential of the grain size component lake level status model for lake s paleohydrological reconstruction

unmixing grain size distributions in lake sediments a new method of endmember modeling using hierarchical clustering the grain size distribution gsd of sediments provides information on sediment provenance transport processes and the sedimentary environment although a wide range of statistical parameters have been applied to summarize gsds most are directed at only parts of the distribution which limits the amount of environmental information that can be retrieved endmember modeling provides a flexible method for unmixing gsds however the calculation of the exact number of endmembers and geologically meaningful endmember spectra remain unresolved using existing modeling methods here we present the methodology hierarchical clustering endmember modeling analysis cemma for unmixing the gsds of sediments within the cemma framework the number of endmembers can be inferred from agglomeration coefficients and the grain size spectra of endmembers are defined on the basis of the average distance between the samples in the clusters after objectively defining grain size endmembers we use a least squares algorithm to calculate the fractions of each gsd endmember that contributes to individual samples to test the cemma method we use a grain size data set from a sediment core from wulungu lake in the junggar basin in china and find that application of the cemma methodology yields geologically and mathematically meaningful results we conclude that cemma is a rapid and flexible approach for analyzing the gsds of sediments

comparison of laser grain size analysis with pipette and sieve analysis a solution for the underestimation of the clay fraction classically the grain size of soil and sediment samples is determined by the sieve method for the coarse fractions and by the pipette method based on the stokes sedimentation rates for the fine fractions results from the two methods are compared with results from laser diffraction size analysis which is based on the forward scattering of monochromatic coherent light from a point of view of laboratory efficiency the laser sizing technique is far superior accuracy and reproducibility are shown by measurements on certified materials it appears that laser grain size measurements of certified materials correspond very well with the certificated measurements tests were also done on a set of randomly selected sediments of fluvial aeolian and lacustrine origin except for the 2 m clay fraction there is a coarsening of the mean diameter of one to two size classes 0 25 caused by the non sphericity of the particles the platy form of the clay particles induces considerable differences eight size classes between pipette and laser measurements the 2 m grain size defined by the pipette method corresponds with a grain size of 8 m defined by the laser particle sizer for the studied sediments using a higher grain size level for the clay fraction when laser analysis is applied enables workers in the geological and environmental field to compare classical pipette analysis with a laser sizing technique

intracaldera volcanic activity toledo caldera and embayment jemez mountains new mexico the toledo caldera was formed at 1 47 0 06 ma during the catastrophic eruption of the lower member bandelier tuff the caldera was obscured at 1 12 0 03 ma during eruption of the equally voluminous upper member of the bandelier tuff that led to formation of the valles caldera earlier workers interpreted a 9 km diameter embayment located ne of the valles caldera toledo embayment to be a remnant of the toledo caldera drill hole data and new k ar dates of toledo intracaldera domes redefine the position of toledo caldera nearly coincident with and of the same dimensions as the younger valles caldera the toledo embayment may be of tectonic origin or a small tschicoma volcanic center caldera this interpretation is consistent with distribution of the lower member of the bandelier tuff and with several other field and drilling related observations explosive activity associated with cerro toledo rhyolite domes is recorded in tuff deposits located between the lower and upper members of the bandelier tuff on the northeast flank of the jemez mountains recorded in the tuff deposits are seven cycles of explosive activity most cycles consist of phreatomagmatic tuffs that grade upward into plinian pumice beds a separate deposit of the same age and consisting of pyroclastic surges and flows is associated with rabbit mountain located on the southeast rim of the valles toledo caldera complex these are the surface expression of what may be a thicker more voluminous intracaldera tuff sequence the combined deposits of the lower and upper members of the bandelier tuff toledo and valles intracaldera sediments tuffs and dome lavas form what we interpret to be a wedge shaped caldera fill this sequence is confirmed by deep drill holes and gravity surveys this fill accumulated in depressions formed during precaldera rifting and episodes of caldera collapse we interpret the toledo valles caldera complex to be a pair of nearly coincident trapdoor calderas with the hinge on the west side and thick caldera fill in the east

differentiating marine vs hydrothermal processes in devonian carbonatemounds using rare earth elements kess kess mounds anti atlas morocco abstract petrological and geochemical analyses were carried out on early devonian kess kess mound limestones of the seheb el rhassel group exposed in the hamar laghdad ridge tafilalt platform eastern anti atlas morocco in order to evaluate marine vs hydrothermal processes for the origin of the mounds hydrothermal fluid circulation affected limestone deposition resulting in the formation of a plumbing system preserved in the mound facies and inter mound facies as cavities veins and dykes shale normalized rare earth element ree patterns for limestones display pronounced light ree depletion compared to middle ree average prsn dysn 0 46 and heavy ree average prsn ybsn 0 55 a super chondritic y ho ratio up to 87 and positive la anomaly consistent with precipitation from normal marine seawater within our data set the ce anomaly as well as u and other trace element concentrations vary with facies providing evidence for variable redox conditions the presence of positive ce anomaly in carbonates of the plumbing system is consistent with precipitation under anoxic condition samples from mound facies and quartz veinlets in the upper part of the group show ree patterns consistent with precipitation from hydrothermal fluids early devonian hypothetical seawater ree patterns were calculated from samples showing normal marine ree patterns i e inter mound facies and from samples with weaker marine signature i e fossiliferous mound limestones and plumbing system deposits hypothetical patterns are slightly enriched in ree compared to modern open ocean seawater this study reveals that ree analysis is a powerful tool for understanding polygenetic carbonate systems it sheds light into the genesis of the kess kess mounds by reconstructing fluid pathways and palaeo redox conditions

a strontium isotope study of the vc 1 core hole and associated hydrothermal fluids and rocks from valles caldera jemez mountains new mexico chemical and strontium isotopic analyses have been performed on 10 geothermal waters from the valles caldera jemez mountain region as well as 10 rock samples collected in the vc 1 scientific core hole the 87sr 86sr values of other rocks sampled in the jemez mountains have also been used in this study to understand relations between the fluids and rocks of the volcanically driven geothermal system and the lateral outflow plume discharging down the jemez fault zone the strontium content of groundwater is linked to the host rock composition the aquifer temperature and therefore the solubility of sr containing minerals low sr concentrations in the fluid are found with a high temperature and or volcanic host rocks whereas high sr concentrations are characteristic of a low temperature and or a paleozoic sedimentary aquifer important variations of the 87sr 86sr value in hydrothermal waters 0 70842 0 72193 are related to chemical composition sr content and host rocks for vc 1 core samples the sr isotopic ratios are also markedly variable 0 70459 0 75686 low for the quaternary volcanics and high for the paleozoic sedimentary rocks the same observation is made for other jemez mountains rocks 0 70465 0 8163 with in addition high 87sr 86sr values for precambrian crystalline rocks a good correspondence is generally found between the waters and the reservoir rocks studied here which indicates that isotopic equilibrium is rapidly attained the following suite of hydraulically related fluids displays a progressive enrichment in radiogenic strontium baca wells 87sr 86sr 0 7084 0 7094 vc 1 core hole at 483 m 0 7152 0 7154 main jemez spring 0 7217 and soda dam 0 7219 this trend is associated with flow through paleozoic rocks and with the length of the flow path from the center of valles caldera primary geothermal fluids toward san diego canyon along the jemez fault zone derivative waters

major and trace element compositions of melt particles and associated phases from the yaxcopoil 1 drill core chicxulub impact structure mexico melt particles found at various depths in impactites from the yaxcopoil 1 borehole into the chicxulub impact structure yucatan have been analyzed for their major and trace element abundances a total of 176 electron microprobe and 45 la icp ms analyses from eight different melt particles were investigated the main purpose of this work was to constrain the compositions of precursor materials and secondary alteration characteristics of these melt particles individual melt particles are highly heterogeneous which makes compositional categorization extremely difficult melt particles from the uppermost part of the impactite sequence are ca and na depleted and show negative ce anomalies which is likely a result of seawater interaction various compositional groupings of melt particles are determined with ternary and binary element ratio plots involving major and trace elements this helps distinguish the degree of alteration versus primary heterogeneity of melt phases comparison of the trace element ratios sc zr y zr ba zr ba rb and sr rb with compositions of known target rocks provides some constraints on protolith compositions however the melt compositions analyzed exceed the known compositional diversity of possible target rocks normalized ree patterns are unique for each melt particle likely reflecting precursor mineral or rock compositions the various discrimination techniques indicate that the highly variable compositions are the products of melting of individual minerals or of mixtures of several minerals small angular shards that are particularly abundant in units 2 and 3 represent rapidly quenched melts whereas larger particles 0 5 mm that contain microlites and have fluidal schlieric textures cooled over a protracted period angular shard like particles with microlites in unit 5 likely crystallized below the glass transition temperature or underwent fragmentation during or after deposition

the phlegraean fields structural evolution volcanic history and eruptive mechanisms abstract the main event within the volcanic history of the phlegraean fields was the eruption about 35 000 years ago of a huge alkali trachytic ignimbrite 80 km 3 dre followed by caldera collapse the pre caldera activity evidence from geothermal wells and surface outcrops changed from submarine to subaerial shortly before the ignimbrite eruption the caldera was subsequently invaded by the sea and became progressively filled with tuffites and subordinate submarine flows in its northern half the last submarine explosive activity dates back to 12000 10500 yr with the eruption of mostly hydroplinian yellow tuffs recent mostly subaerial activity consists of a series of explosive eruptions whose volume decreases with time until the last eruption of mt nuovo in 1538 a d two peaks in recent activity occur at 10000 8000 and 4700 3000 years ago during post caldera activity eruptive vents migrated from the caldera rim toward the center where there are two distinct zones of recent vents minor collapses occurred within the caldera after the main eruptions often they are eccentric to the vent and displaced toward the caldera center phlegraean explosive activity is characterized by water magma interaction eruptive events without a hydromagmatic component are extremely rare in most cases the evolved trachytic magmas interacted with surface water either the sea or intracaldera lakes however there is evidence of interaction of magma with deep seated aquifers for some plinian events explosivity i e the efficiency of the transformation of thermal into kinetic energy during magma water interaction is largely controlled by the primary fragmentation of the magmatic melt

reflections of the geological characteristics of cyprus in soil rare earth element patterns abstract rare earth elements rees are used as indicators or proxies for a range of geological and mineralogical processes due to their unique geochemical characteristics total and aqua regia extractable concentrations of rees and 57 other elements have been determined for 5350 soil samples as part of the high sampling density geochemical atlas of cyprus the bedrock geology of cyprus is dominated by the sequence of ultramafic to mafic units formed at a spreading ridge and subsequently obducted to form the troodos ophiolite to and the surrounding carbonate rich circum troodos sedimentary sequence ctss deposited in environments ranging from deep marine to sub aerial total and aqua regia extractable ree patterns are similar for each element and are largely controlled by parent lithology soil to rock ree ratios are generally elevated in the to units 4 for lrees and 1 5 3 for hrees due to loss of more mobile elements during weathering but are close to 1 in the ctss units hrees are more elevated than lrees in soils derived from to units with upper continental crust normalised patterns indicating the main source to be pyroxenes and zircon trace element trends indicate rees in the ctss were largely derived from detrital material shedding off the to and deposited in progressively shallowing basins under largely anoxic conditions absence of ce4 anomalies with a minor contribution from seawater via adsorption onto secondary fe mn oxides or co precipitation with carbonates heavy mineral associated elements such as zr and th display a relative consistent ratio in the ctss soils peak hree concentrations occur in the mafic cumulates and intrusives where the median laucc ybucc is 0 12 whereas in ctss units the lrees are more elevated with a median laucc ybucc 0 7 due to the strong lithogeochemical controls soil ree spatial patterns reflect even subtle mineralogical variations within the various to units the location of major transform faults and other structures and areas that have been affected by hydrothermal alteration

tem study of the alteration of interstitial glass in morb by inorganic processes abstract scanning electron microscopy sem and transmission electron microscopy tem observations on a suite of mid ocean ridge basalts morb reveal abundant interstitial glass which differs in occurrence and composition from basaltic glass at pillow rims interstitial glass consists dominantly of sio2 and al2o3 and is depleted in other cations representing a highly differentiated residual material low temperature alteration by seawater solutions results in the formation of saponite mg rich variety of smectite replacing the interstitial glass the si al ratio of this saponite reflects that of the source glass chemical changes during this transition differ from those resulting from alteration of basaltic or rhyolitic glass alteration of interstitial glass results in uptake of mg and fe and loss of si and al but there is little or no leaching of alkalis this reflects a strong control on chemical reactions by solution composition high na and mg concentrations of seawater fluids in contrast to basaltic glass at pillow rims our observations do not reveal microbial activities in the alteration of interstitial glass

trace elements and ree geochemistry of middle devonian carbonate mounds maider basin eastern anti atlas morocco implications for early diagenetic processes abstract trace and rare earth elements rees have proven their utility as tools for assessing the genesis and early diagenesis of widespread geological bodies such as carbonate mounds whose genetic processes are not yet fully understood carbonates from the middle devonian conical mud mounds of the maider basin eastern anti atlas morocco have been analysed for their ree and trace element distribution collectively the carbonates from the maider basin mud mounds appear to display coherent ree patterns three different geochemical patterns possibly related with three different diagenetic events include i dyke fills with a normal marine ree pattern probably precipitated in equilibrium with seawater ii mound micrite with a particular enrichment of overall ree contents and variable ce anomaly probably related to variation of ph increase of alkalinity or dissolution remineralization of organic matter during early diagenesis and iii haematite rich vein fills precipitated from venting fluids of probable hydrothermal origin our results reinforce the hypothesis that these mounds were probably affected by an early diagenesis induced by microbial activity and triggered by abundance of dispersed organic matter whilst venting may have affected the mounds during a later diagenetic phase

europium redox equilibria in aqueous solution thermochemical data and recent advances in theoretical aqueous solution chemistry enable prediction of the relative stabilities of aqueous eu2 and eu3 over a wide range of temperatures and pressures at low temperatures near earth surface conditions the aqueous geochemistry of europium should be dominated by the trivalent state except possibly in the most reducing alkaline pore waters of anoxic marine sediments however at temperatures greater than about 250 c and elevated pressures divalent europium should predominate even with significant amounts of complexing trivalent europium is not stable at elevated temperatures and pressures consequently under most hydrothermal and metamorphic conditions europium in aqueous solution should be divalent at intermediate temperatures around 100 c significant activities of both eu2 and eu3 and related complexes can occur in aqueous solutions depending on the oxidation state and the ph of the solutions and the activities of potential ligands such as sulfate carbonate and chloride the predicted stability of divalent europium in aqueous solution at elevated temperatures is consistent with the large positive europium anomalies in rare earth element patterns of high temperature barites of hydrothermal and metamorphic origin reported by guichard et al 5 and with the observed depletion of europium as a result of high temperature sericitization of feldspar bearing assemblages discovered by alderton et al 1 it is suggested that significant fractionation of europium relative to the other rare earth elements may take place during high temperature hydrothermal alteration processes such as in the mid oceanic ridge systems because of the expected stability of divalent europium during these processes

new remains of the baluchithere paraceratherium bugtiense pilgrim 1910 from the late latest oligocene of the bugti hills balochistan pakistan new dental and postcranial remains referred to the giant rhinocerotoid paraceratherium bugtiense are described originating from its type locality lundo chur in eastern balochistan pakistan probable sexual dimorphism is revealed on the lower incisors the manus was tridactyl with a reduced fifth metacarpal the stratigraphic range of both p bugtiense and the amynodontid cadurcotherium indicum extends from the early early oligocene to the late latest oligocene in the bugti hills q 2004 published by elsevier ltd

lake bourget regional erosion patterns reconstruction reveals holocene nw european alps soil evolution and paleohydrology abstract two well dated ca holocene long sedimentary sequences from deepest parts of lake bourget provide new insights onto the evolution of erosion patterns at a regional scale in nw european alps the combination of high resolution geochemistry xrf core scanning calibrated by 150 punctual measurements and isotope geochemistry nd of the terrigenous fraction permitted the reconstruction not only of the intensity but also the type physical erosion vs chemical weathering and the location prealpine massifs vs high crystalline massifs of dominant erosion processes those data point the persistency of weak erosion fluxes from 9600 to 5500 cal bp due both to a dry climate and the growing sheltering effect of soils that rapidly progressed between 9600 and 8000 cal bp soils then reached a steady state before being destabilised around 4400 cal bp probably in response to human impact the human impact then reached a sufficient intensity to change erosion patterns at a regional scale but did not result in a significant increase of the regional terrigenous flux the following enhancement of erosion processes occurred around 2700 cal bp it was first paced by changing climatic conditions but probably reinforced by human impact during late iron age antiquity period over the long term trend the lake bourget record pinpoints an evolution of paleohydrological conditions in the alps dominated by dry conditions from 9500 to 4400 cal bp and a subsequent drift toward wetter conditions that culminated during the so called little ice age ca 1350 1900 ad in such a context the current dry conditions in european alps appear out of trend at high resolution 17 periods of enhanced hydrological activity highlight the rapid climatic changes that are typical of the holocene

petrology of the volcanic bedrock of mururoa atoll tuamotu archipelago french polynesia abstract the south pacific atoll of mururoa is located in the southeastern part of the tuamotu archipelago it is about 28 km long and represents the emergent part of a 60 km long submarine plateau this atoll is composed of submarine volcanic rocks resting on oceanic crust then above subaerial volcanic rocks and finally a coral coating about 300 m thick the volcanic rocks are markedly alkaline and this alkaline magmatic trend evolved by fractional crystallization from nepheline normative 10 wt basalts to quartz normative 5 wt trachyte fractionation of phlogopite played a significant role in this evolution the basic lavas contain olivine spinel magnetite ilmenite clinopyroxene and plagioclase phenocrysts rare feldspathoids occur in the groundmass of the hawaiites two trends can be distinguished the first one characterized by the presence of mica plagioclase and ilmenite has evolved under high p h 2 o the second characterized by amphibole richterite and arfvedsonite aegirine alkali feldspar and magnetite has evolved under lower p h 2 o and silica activity but higher f o 2 thermodynamic conditions of crystallization at depth deduced from olivine liquid plagioclase liquid and magnetite ilmenite equilibria are high temperature 1100 to 1200 c medium water pressure 1 to 1 5 kbar and medium to low oxygen fugacity 10 10 bar the mururoa magmas may have issued from fissures along the australes fault it may not result from the activity of the hot spot situated east of pitcairn island considered as responsible for the volcanism of others islands of the tuamotu archipelago fangataufa gambier pitcairn

muddled or mixed inferring palaeoclimate from size distributions of deep sea clastics abstract one of the outstanding problems of palaeoclimate reconstruction from physico chemical properties of terrigenous deep sea sediments stems from the fact that most basin fills are mixtures of sediment populations derived from different sources and transported to the site of deposition by different mechanisms conventional approaches to palaeoclimate reconstruction from deep sea sediments do not distinguish between provenance and dispersal related variations and therefore often fail to recognise the true significance of variations in sediment properties we formulate a set of requirements that each proposed palaeo environmental indicator should fulfil and focus on the intrinsic coupling between grain size and chemical composition a critical review of past achievements in grain size analysis serves to introduce a conceptual model of spatio temporal grain size variation based on dynamic populations each dynamic population results from a characteristic combination of production and transport mechanisms that corresponds to a distinct subpopulation in the data analysed the mathematical statistical representation of the conceptual model can be obtained by means of the end member modelling algorithm emma applications of the model to several ocean basins are discussed as well as methods to examine the validity of grain size based palaeoclimate reconstructions palaeoclimate reconstructions of a high and low latitude basin illustrate the common degree of complexity of deep sea grain size records

biogeography and migration routes of large mammal faunas in south east asia during the late middle pleistocene focus on the fossil and extant faunas from thailand abstract thailand has long held a key position in south east asia because of its location at the boundary of the indochinese and sundaic provinces the major biogeographical regions of south east asia these provinces are distinct climatically floristically and faunistically the present day limit between them is located at the kra isthmus in peninsular thailand previous studies of the javanese large mammal fossil faunas and the recent study of fossil large mammal faunas from thailand strengthen the hypothesis of a continental migration route in contrast with the insular hypothesis via taiwan and the philippines during the late middle late pleistocene period thailand was even part of this migration route during the glacial periods the faunal exchanges were favored by the emersion of a huge continental shelf called sundaland south east asian continental area connected to borneo and indonesia islands by land bridges when the sea level was low no geological biogeographical or paleobiogeographical evidence supports the hypothesis of a migration route via taiwan and the philippines analysis of the extant and late middle pleistocene large mammal faunas carnivora primates proboscidea and ungulata points out the antiquity of the indochinese and sundaic provinces this idea is also supported by the fact that mainland faunas already displayed modern character whereas the javanese faunas were mainly composed of endemic forms however the occurrence of the extinct species elephas namadicus found in a malaysian site tambun indicates that the limit between the two provinces if not close to the present place was located more southward than today possibly in peninsular malaysia it is also confirmed by the presence of northern species such as ailuropoda melanoleuca baconi and crocuta crocuta ultima in late middle pleistocene sites of thailand in fact because of climatic cooling that occurred in the northern hemisphere during the pleistocene the northern faunas had to move southward to our knowledge the hypothesis of the antiquity of the south east asian provinces with a boundary south of the present day one is mentioned here for the first time previous biogeographical studies were based mainly on insular data from the philippine archipelago geological and mainly present day zoogeographical data but also from indonesia and borneo paleontological data however the recent discovery of thai large mammal faunas from late middle pleistocene allows to bridge the gap in the fossil record between the northern faunas of south east asia and the southern ones these thai faunas are characterized mainly by extant forms but some are today absent from the thai territory ailuropoda melanoleuca crocuta crocuta pongo pygmaeus sus cf barbatus rhinoceros cf unicornis cervus eldii

late holocene indian summer monsoon precipitation history at lake lugu northwestern yunnan province southwestern china abstract knowledge of late holocene precipitation variability in the northwestern yunnan province is important for understanding the indian summer monsoon ism dynamics in this study we present a proxy record of the ism precipitation history at lake lugu covering the last 2 900 years based on grain size and carbon nitrogen c n ratio in the northwestern yunnan province the results show centennial variations in ism precipitation with two remarkably dry intervals from 750 to 1167 ad and from 1733 ad to the present and two relatively wet intervals from 898 bc to 750 ad and from 1167 to 1733 ad a comparison between the record at lake lugu and the pollen record at lake erhai both in the northwestern yunnan province suggests that dry climate conditions prevailed during the medieval warm period mwp and over the last 100 200 years whereas relatively humid conditions prevailed during the little ice age lia these characteristics are generally similar to those of the climate patterns in extensive areas dominated by the ism e g southwestern southern china southeastern southern tibetan plateau northeastern india himalayas southern oman and equatorial eastern africa but anti phased with the climate patterns in the wide areas dominated by the east asian summer monsoon easm e g northern northeastern china and north central japan we speculate that both the variations in the sea surface temperature sst over the tropical indo pacific ocean the ocean atmosphere coupling processes and the migration of the mean position of the intertropical convergence zone itcz should be responsible for the hydroclimatic contrasts over the asian summer monsoon asm region on centennial timescales during the last 2 000 years

ferruginous and manganiferous haloes around massive sulphide deposits of the urals proximal brecciform ferruginous and manganiferous rocks related to vms deposits of the urals are subdivided into jasperites gossanites and umbers in addition to thin bedded jaspers and cherts the coherence of host rock composition and mn fe fertility of the sediments have been established fe poor pink hematitic and gray sulphidic chert are typical of the felsic class of vms deposits in contrast the contents of fe vary from high to moderate in ferruginous rocks enclosed in basaltic units associate with vms deposits fe and mn rich ferruginous rocks and umbers occur in association with limestones and calcareous sedimentary rocks in both types of volcanic sequences a common feature of jasperites and umbers is the abundance of replacement textures of hyaloclastites and carbonates by hematite and silica in addition replacement of clastic sulphides by hematite and magnetite is a characteristic genetic feature of gossanites all of these sedimentary rocks are accompanied by pseudomorphs of hematite and quartz formed after bacterial filaments the abundance of replacement textures are supportive of the halmyrolysis model in addition to hydrothermal sedimentary and sub seafloor hydrothermal replacement theories study of chemical zonation of altered hyaloclasts shows depletion of their rims not only in mobile na k mg but also in immobile al ti and ree whereas si and fe are concentrated in situ the halmyrolysis model presented here involving organic rich calcareous hyaloclastic sediments resolves the problem of subtraction of al ti ree and other elements which are commonly immobile under hydrothermal conditions the evolution of the halmyrolysis process from acidic reducing to alkaline oxidized conditions infers a possible range in transformation from fe ii mg smectites to fe silicates and fe si oxides as precursors of brecciform jasperite and thin bedded jasper the higher acidic initial stage of gossanite formation seems to be required for oxidation of organic matter and or pyrite the acidic condition facilitates the temporal preservation of immobile elements al ti ree in immature chlorite hematite gossanites another peculiarity of the gossanite forming processes is the likely sorption of p u and v by iron hydroxides displacing sulphides the general evolution of all ferruginous sediments results in complete fe 2 oxidation and silicification accompanied by subtraction of other elements the vertical diagenetic differentiation leads to concentration of mn carbonates silicates and oxyhydroxides into the tops of jasperite and gossanite layers mn oxyhydroxides scavenge positively charged hydrated cations like co and ni near vent bacterial communities may activate the processes of volcanic glass and sulphide degradation the proposed processes of halmyrolysis followed by silicification in situ may resolve the enigma of silica rich sediment formation in a silica undersaturated ocean the discrimination between gossanite and jasperite is useful for elaboration of new criteria for local exploration of vms and mn deposits halo dispersion of gossanites covering an area about two to three times that of the massive sulphide deposit is a good vector for ore body discovery proximal gossanites can be differentiated from jasperites by presence of relic sulphide clasts or elevated contents of chalcophile elements cu fe zn pb bi te as sb ba noble metals au ag and distinct ree patterns with la and eu positive anomalies the development of halmyrolysis and biomineralization models merit further elaboration and testing in on going research in order to add or revise theories of iron and manganese deposit formation 2012 elsevier b v

an end member algorithm for deciphering modern detrital processes from lake sediments of lake donggi cona ne tibetan plateau china abstract deciphering significant sedimentological processes from a set of sediment samples is an important step in reconstructing environmental changes one approach going beyond classical methods is the unmixing of grain size distributions this paper presents a flexible end member modelling algorithm that is based on eigenspace analysis and considers inherent uncertainties it has been applied to the detrital grain size components of lacustrine surface sediment samples of lake donggi cona qinghai province china it allows up to five grain size end members to be characterised and quantified in an optimal model an end member with a major mode in the clay domain accounts for 34 of variance within the grain size data set it may represent sedimentation of suspension load from linear and laminar runoff during heavy precipitation events in summer three end members in the fine sand to medium silt domains make up 60 of lacustrine sedimentation they may represent local to remote aeolian processes that peak in wintertime a multimodal end member explaining the remaining 6 of variance may represent further fluvial and littoral dynamics or random fluctuations and measurement errors several model runs of different scaling and numbers of end members provided a suitable way to determine uncertainties inherent to the model a comparison of 12 different model runs and their respective uncertainties yielded a distinct model of robust end members the clay and medium silt end members are robust features of detrital sedimentation within lake donggi cona they alone explain 54 4 of total variance in the data however no spatial pattern or relation to water depth is found for any of the grain size end members thus when past detrital sedimentation at lake donggi cona is reconstructed a special focus should be on the robust features attributed to aeolian and suspension related sedimentation processes as well as on effective sediment mixing processes impeding a distinct correlation between grain size and spatial attributes further applications of the end member modelling algorithm to other depositional environments are encouraged to demonstrate its universal applicability

early rhinocerotids mammalia perissodactyla from south asia and a review of the holarctic paleogene rhinocerotid record the earliest rhinocerotids from south asia are identified on the basis of few dental remains originating from the late eocene of thailand wai lek mine krabi basin and the early oligocene of pakistan paali nala c2 bugti hills once synthesized the holarctic paleogene rhinocerotid record points out a westward diachronism of rhinocerotid first appearance data from north america to europe via asia throughout mid cenozoic times the faunal similarity among mammal localities from the late eocene and early oligocene of peninsular thailand southern china and pakistan suggests the existence of a single south asian paleoprovince during this interval and the persistence of a tropical subtropical climate substantial faunal changes recorded in eastern balochistan reveal a significant climatic deterioration from the middle part of the oligocene neither provinciality nor endemism is noticeable for rhinocerotoid taxa recognized in the oligocene of the indian subcontinent neither the himalayas nor the tibet plateau was a paleogeographic barrier for large mammals during this interval resume les plus anciens rhinocerotides d asie du sud sont identifies gr ce a quelques restes dentaires provenant de l eocene superieur de thailande mine de wai lek bassin de krabi et de l oligocene inferieur du pakistan paali nala c2 collines bugti la synthese du registre fossile paleogene holarctique des rhinocerotides revele un net diachronisme des premieres apparitions de rhinocerotides depuis l est amerique du nord vers l ouest asie puis europe au cours du cenozoique moyen la similarite des communautes de mammiferes entre les localites de l eocene superieur et de l oligocene inferieur de thailande peninsulaire de chine du sud et du pakistan suggere l existence d une seule paleoprovince sud asiatique pendant la periode consideree sous un climat tropical a subtropical les changements fauniques enregistres au balouchistan oriental revelent une deterioration climatique significative a partir du milieu de l oligocene aucun indice de provincialisme ou d endemisme n est releve pour les rhinocerotoides oligocenes du sous continent indien ni les himalayas ni le plateau du tibet ne constituaient a l epoque une barriere paleogeographique pour les grands mammiferes

the ree content of some hydrothermal fluids ree concentrations were determined in solutions from submarine hydrothermal vents on the east pacific rise and for the first time from continental geothermal fields in tibet and bulgaria they indicate that in hydrothermal systems ree are immobile at temperatures below 350 c and for water rock ratios of 105 nd values of submarine solutions and anhydrites 4 7 to 6 2 suggests recharge on the sedimentcovered flanks of the ridge carbonate anions as measured by alkalinity appear to increase the solubility of heavy ree somewhat but not to the extent that substantial amounts of ree could be driven out from rocks by hydrothermal activity

effect of orogeny plate motion and land sea distribution on eurasian climate change over the past 30 million years the eurasian climates of today 10 million and 3o million years ago are simulated using an atmospheric general circulation model that incorporates realistic continental geography and epicontinental sea distributions the resulting climates compare well with various palaeoclimate records the retreat of the paratethys an epicontinental sea shifts the central asian climate from temperate to continental conditions and plays as important a role as uplift of the himalayan tibetan plateau in driving the asian monsoon changes

manganese geochemistry near high temperature vents in the mid atlantic ridge rift valley in july 1985 the first high temperature hydrothermal vents ever discovered on the mar were found at 26 n tag a transponder navigated survey of a 4 8 km area was begun when on board measurements of manganese revealed concentrated hydrothermal plumes in the water column comparable in size and intensity to those found over geothermal fields on the epr these plumes also possess anomalously high light scattering properties and anomalously warm potential temperatures using relay transponder navigation with a rosette ctd system it was possible to sample bottom waters with temperature anomalies of several decidegrees samples collected near vent orifices possessed silica anomalies of up to 17 m and dissolved manganese anomalies as large as 360 nmol kg these manganese and silica anomalies are linearly related and predict amn si ratio of 20 mmol mol for these mar vent fluids a value essentially identical to that measured in 350 c fluid from the epr at 21 n the distribution of temperature anomalies in the water column over this area requires the presence of more than one active vent site a rough estimate of the convective heat loss from this section of the mar based on z profiles is 1 2 108 cal s which is similar to the heat loss estimated for the vent field on the epr at 21 n

grain size distribution function of polymodal sediments in hydraulic and aeolian environments and numerical partitioning of the sedimentary components most continental sediments are polymodal composed of overlapping components of which the grain size generally obeys some type of natural distribution the grain size components and their function types can be determined from frequency and cumulative curve plots in order to define the function formula of the grain size distribution the function parameters can be estimated by fitting a defined function formula to the measured grain size data of the sample which simultaneously achieves numerical partitioning of the sedimentary components genetic analysis of grain size components of hydraulic and aeolian sediments demonstrates the following environmental implications fluvial sediment is composed of isolated saltation and suspension components the sediments in closed lake basins are dominated by a suspension silt clay component with a small proportion of saltation sand the fine sand component makes up the majority of desert sand overlapping with a small proportion of fine dust aeolian loess is composed of two overlapping components a short suspension time silt component and a long suspension time fine component aeolian material in the north pacific deep sea sediments is dominated by long suspension time fine dust the fine component in aeolian sediments shows a consistent grain size distribution and genetic connection from the desert sand loess of northern china to the north pacific ocean which is mainly transported by westerly winds and is dispersed in the atmosphere forming a background dust c 2002 elsevier science b v all rights reserved

effects of vegetation type on soil resistance to erosion relationship between aggregate stability and shear strength article i nfo soil water erosion and shallow landslides depend on aggregate stability and soil shear strength we investigated the effect of vegetation on both soil aggregate stability and shear strength through direct shear tests in former croplands converted to vegetated erosion protection areas within the context of china s sloping land conversion programme four treatments were analysed in plots comprised of i 4 year old crop trees vernicia fordii where understory vegetation was removed ii v fordii and the dominant understory species artemisia codonocephala iii only a codonocephala and iv no vegetation soil samples were taken at depths of 0 5 cm and 45 50 cm root length density rld in five diameter classes was measured soil organic carbon soc hot water extractable carbon hwec texture and fe and al oxides were also measured we found that mean weight diameter after slow wetting mwdsw in the a horizon was significantly greater 0 94 1 01 mm when a codonocephala was present compared to plots without a codonocephala 0 57 0 59 mm soc and rld in the smallest diameter class b0 5 mm were the variables which best explained variability in mwdsw a significant positive linear relationship existed between mwdsw and soil cohesion but not with internal angle of friction as herbaceous vegetation was more efficient than trees in improving aggregate stability this result suggests that the mechanisms involved include modifications of the cohesive forces between soil particles adjacent to plant roots and located in the enriched in soc rhizosphere thus also affecting shear strength of the corresponding soil volume thus vegetation stabilised soil under different hierarchical levels of aggregate organisation i e intra and inter aggregate our results have implications for the efficacy of techniques used in land conversion programs dedicated to control of soil erosion and shallow landslides we suggest that mixtures of different plant functional types would improve soil conservation on slopes by reducing both surface water erosion and shallow substrate mass movement planting trees for cropping or logging and removing understory vegetation is most likely detrimental to soil conservation

pakistan mammal tooth stable isotopes show paleoclimatic and paleoenvironmental changes since the early oligocene abstract this research presents an isotopic study of three large mammal groups elephantoid proboscideans hyracodontid and rhinocerotid rhinocerotoids equids of the hipparion group from the bugti hills sequence eastern balochistan pakistan combined with published data from the miocene siwalik group northern central pakistan these two exceptional fossil records from pakistan provide an unambiguous source of biotic information from the early oligocene up to the late miocene the 13 c c and 18 o c results from the same herbivore groups show several significant variations in environmental and climatic conditions throughout the 30 to 7 5 myr period in this region first from 30 to 22 myr the environment is characterized by a relatively dry but dense forest existing under a temperate to subtropical climate with a more closed tropical environment at 23 myr oligocene 18 o of the terrestrial herbivore teeth agrees with the marine foraminifera 18 o and mg ca trends suggesting that the pakistan region was affected by global climate rather than regional conditions after 22 myr the 18 o c mammal enamel results show a long term decreasing trend until 15 myr toward a wetter environment with the appearance of tropical forests in response to the probable onset of the asian monsoon this is a period of high tectonic activity with the india asia collision leading to uplift of the tibetan plateau and shrinkage of the epicontinental paratethys sea this activity modified the land sea distribution and the thermal contrast between ocean and continent the driving force of the monsoon climate the middle miocene environment in pakistan experienced moist conditions under an intense monsoon system with relatively closed rainforest after 12 myr the 18 o c enamel values record a positive shift until 9 3 myr toward a drier environment with an increase of seasonality as suggested by higher 18 o c variability after 9 3 myr these late miocene drier climatic conditions and the asian monsoon intensification could potentially favour the c 4 photosynthetic pathway and hence the development of grassland to the detriment of subtropical forests resulting in the higher enamel 13 c values recorded after 9 3 myr

chemistry of thermal springs in the larderello travale geothermal region southern tuscany italy abstract thirty two thermal spring eleven cold spring and six steam condensates in the larderello travale geothermal region have been studied from a geochemical point of view the aim of this work was to delineate the relation between the chemical composition of the natural thermal manifestations and the thermal anomaly which is among the best known in the world the larderello spring both hot and cold are characterized by low salinity total dissolved solids generally lower than 1000 mg kg and alkaline earth bicarbonate composition in contrast an alkaline earth sulfate composition characterizes the thermal springs of the travale area this difference is due to the fact that the underground pathways of the larderello hot springs are only in shallow flyschoid caprock formations whereas at travale the paths are longer and in carbonate anhydritic mesozoic rocks which constitute the main reservoir formations in both the larderello and travale areas the thermal character of larderello springs is therefore mainly due to rock conduction whereas in travale it is mostly due to inflows of hot fluid phases from the geothermal reservoir comparison between ammonia li and b in fluid phases both steam condensates and hot springs in the larderello area suggests that in some of them their temperatures might be partly due to direct vapor inflows

the temporal evolution of fluid flow through the tahiti barrier reef traced by sr isotopes and pore water chemistry abstract the internal fluid circulation of the tahiti barrier reef has been studied with sr isotopes and pore water chemistry the study is based on 15 sample series recovered over 2 years from a 150 m deep core drilled through the entire barrier reef down to the volcanic basement temperature data suggest that the interstitial fluids originate from seawater that penetrated the volcanic basement to at least 200 m depth on the ocean sided slope below the barrier reef subsequently the fluids migrated upward driven by buoyancy through the entire reef chemical evolution of the interstitial fluids is mainly controlled by basalt seawater interaction and by admixture of seawater from the open ocean during upward migration these processes are monitored with 87sr 86sr isotope ratios h4sio4 concentrations and alkalinity to give a picture of the evolution of interstitial fluid flow over 2 years the results indicate that the internal circulation patterns change through time the modifications concern mainly the residence time of the fluids within the volcanics and the intensity and localization of lateral seawater admixture within the karstified pleistocene reef