organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

new views of lunar geoscience an introduction and overview beyond the earth the moon is the only planetary body for which we have samples from known locations the analysis of these samples gives us ground truth for numerous remote sensing studies of the physical and chemical properties of the moon and they are invaluable for our fundamental understanding of lunar origin and evolution prior to the return of the apollo 11 samples the moon was thought by many to be a primitive undifferentiated body e g urey 1966 a concept shattered by the data returned from the apollo and luna missions ever since new data have helped to address some of our questions but of course they also produced new questions in this chapter we provide a summary of knowledge about lunar geologic processes and we describe major scientific advancements of the last decade that are mainly related to the most recent lunar missions such as galileo clementine and lunar prospector 1 1 the moon in the planetary context compared to terrestrial planets the moon is unique in terms of its bulk density its size and its origin fig 1 1a c all of which have profound effects on its thermal evolution and the formation of a secondary crust fig 1 1d numerous planetary scientists considered the moon as an endmember among the planetary bodies in our solar system because its lithosphere has been relatively cool rigid and intact throughout most of geological time a one plate planet and its surface has not been affected by plate recycling an atmosphere water or life therefore the moon recorded and preserved evidence for geologic processes that were active over the last 4 4 5 b y and offers us the unique opportunity to look back into geologic times for which evidence on earth has long been erased fig 1 1c d impact cratering an exterior process is considered the most important surface process on the moon internal

variability within a saprolite deposit near quebec city canada samples were collected in two trenches opened in a saprolite developed in a mylonite derived from biotite garnet gneiss near quebec city in order to investigate the spatial variability from the points of view of morphological physical mineralogical and chemical properties phyllosilicate assemblages were a kaolinite b mica c kaolinite mica and d mica interstratified minerals smectite grouping of the samples according to prominent colour in the matrix showed a relation between chroma and kaolinite content total chemical analyses were in good agreement with mineral assemblages the spatial distribution of these assemblages corresponded to the degree of transformation of the gneiss into mylonite

water salinity and productivity recorded by ostracod assemblages and their carbon isotopes since the early holocene at lake qinghai on the northeastern qinghai tibet plateau china abstract lake qinghai the largest saline lake in china is a closed basin lake with a salinity of 16 g l and is situated in the sensitive semi arid zone between the asian monsoon controlled area and the westerly jet stream influenced area with the support of the international continental drilling program icdp lake qinghai was drilled in 2005 using the icdp glad800 drilling system two ostracod species i e limnocythere inopinata and eucypris mareotica were found only in the upper 5 15 m of the drilled core 1f covering 12 ka where the depths of 5 15 to 3 15 m 12 0 7 4 ka are dominated by e mareotica and the depths of 3 15 to 0 m 7 4 ka present are dominated by l inopinata the presence of the ostracod eucypris mareotica was related to the high salinity of the water exceeding 30 g l and the dominant species of ostracod limnocythere inopinata was related to the brackish water 3 16 g l in the lake qinghai area li et al 2010 the changes in the carbon isotope in the modern ostracod shells were related to the water salinity and productivity on the lake bottom in lake qinghai li et al 2012 on this basis this study evaluated the changes in lake salinity and productivity and their relation to climatic change using changes in the relative abundances of ostracod fossil species assemblages and the stable carbon isotope in ostracod shells from core 1f and other published data e g total organic carbon content 13 c toc and ice core 18 o the single occurrence of ostracod eucypris mareotica and the highest average 13 c values 0 2 in their shells indicated that the lake salinity and productivity were very high a phenomenon that was related to the high temperature and low lake level caused by intense evaporation even though the precipitation increased sharply in the early holocene the deceased abundance of ostracod e mareotica and the lowest average 13 c values 2 0 in ostracod shells showed that the lake salinity and productivity decreased because of the increased lake level and decreased temperatures in the middle holocene finally the lake level decreased but the water salinity and the lake productivity gradually increased because of the high e i ratio related to the increased temperature in the late holocene

progressive deformation of feldspar recording low barometry impact processes tenoumer impact structure mauritania the tenoumer impact structure is a small well preserved crater within archean to paleoproterozoic amphibolite gneiss and granite of the reguibat shield north central mauritania the structure is surrounded by a thin ejecta blanket of crystalline blocks granitic gneiss granite and amphibolite and impact melt rocks evidence of shock metamorphism of quartz most notably planar deformation features pdfs occurs exclusively in granitic clasts entrained within small bodies of polymict glass rich breccia impact related deformation features in oligoclase and microcline grains on the other hand occur both within clasts in melt breccia deposits where they co occur with quartz pdfs and also within melt free crystalline ejecta in the absence of co occurring quartz pdfs feldspar deformation features include multiple orientations of pdfs enhanced optical relief of grain components selective disordering of alternate twins inclined lamellae within alternate twins and combinations of these individual textures the distribution of shock features in quartz and feldspar suggests that deformation textures within feldspar can record a wide range of average pressures starting below that required for shock deformation of quartz we suggest that experimental analysis of feldspar behavior combined with detailed mapping of shock metamorphism of feldspar in natural systems may provide critical data to constrain energy dissipation within impact regimes that experienced low average shock pressures

biological nitrate utilization in south siberian lakes baikal and hovsgol during the last glacial period the influence of climate change on primary productivity abstract stable nitrogen isotope ratios 15 n in sediment cores recovered from two siberian lakes baikal and hovsgol are determined in order to evaluate the biologically mediated nitrogen cycle from the last glacial period to the postglacial period the ranges of 15 n values from the two lakes are similar varying from 2 8 to 6 7 the high values of 15 n around 6 during the last glacial maximum lgm 26 5 19 cal ka bp indicate that a larger fraction of the available nitrate in both lakes was utilised by phytoplankton a cool and dry climate during the lgm may have limited the input of terrestrial nitrate resulting in the use of a large fraction of the nitrate and low productivity in both lakes the use of a smaller fraction of the nitrate by phytoplankton in both lakes after the lgm 19 12 cal ka bp is reflected in the lower 15 n values down to 3 0 the increase in summer insolation after the lgm caused increased vertical mixing of the lake water column which transported nitrate upwards from the deeper waters and into the photic zone the reduced rate of nitrogen consumption after the lgm indicates that nitrate was more readily available to phytoplankton at this time and did not limit their activities this change suggests that other factors limited phytoplankton activity during this period at the climatic transition between oxygen isotope stages 2 and 1 around 11 5 cal ka bp the rapid increase in 15 n from 3 0 to 6 0 reflected a rapid increase in nitrate utilization at this transition increases in precipitation and lake levels which were associated with the increased intensity of the east asian monsoon may have brought a large influx of nutrients required by the phytoplankton into the lakes from the watershed this hydrological change led to increased phytoplankton activity in both lakes resulting in increased nitrate consumption the 15 n data obtained here from the sediments of lakes baikal and hovsgol suggest that the nitrogen cycle in the siberian region is strongly linked to hydrological changes across the asian continent which are related to global climate change

crystal structure mosaicity and strain analysis of hawaiian olivines using in situ x ray diffraction deformation of olivine in a volcanic context is poorly constrained although deformed olivine is abundant in some volcanic rocks and its presence is important for the definition of the magmatic history of volcanic edifices such as kilauea volcano hawaii deformed olivines at kilauea originate in the lower crust therefore the classic approaches and interpretations applied to mantle derived olivine are not applicable deformed olivine crystals from kilauea lava samples were examined using an in situ xrd technique our results validate and refine optical observations of olivine deformation we also confirm the presence of deformation and quantify it for olivine crystals of any size even for small crystals 0 15 mm there are significant correlations between deformation intensity strain related mosaicity and olivine composition and crystal size although this technique does not allow the simple estimation of the p t conditions of deformation crystal formation or magmatic history some constraints are provided herein in particular we estimate the threshold degree of mosaicity above which we consider that a crystal underwent deformation in situ xrd is shown to be an easy to use fast low cost non destructive technique and is less ambiguous than optical microscopy for crystals optically exhibiting subgrain formation analysis of asterism by in situ xrd has been used to reconstruct the mosaic spread of the original grain and thus its original strain condition prior to subgrain formation

palaeoclimate interpretation of stable isotope data from lake sediment archives the isotope composition of authigenic and biogenic carbonates and diatom silica are commonly used as palaeoclimate proxies from lake sediments this article reviews the controls on the isotope composition of lacustrine skeletal and non skeletal deposits and illustrates how stable isotope studies contribute to an understanding of changes in temperature precipitation patterns evaporation and the carbon cycle it highlights the differences in the palaeoclimate potential of a wide range of lakes ranging from open to closed lake basins a large number of the case histories but not all are drawn from studies of temperate lakes from europe large closed lake systems in the tropics and elsewhere lose water predominantly through evaporation and contain sediments with variable and generally high 18o values fluctuations in the isotope composition of authigenic or biogenic minerals are mainly a function of long term changes in the precipitation evaporation ratio in contrast small open lakes which have a degree of through flow typically contain sediments with 18o values that vary by no more than a few these variations are generally ascribed to variations in temperature or the isotope composition of precipitation p from which either an annual or seasonally specific signal can be gained these types of lakes are common in northern europe and at high altitudes the interpretation of isotope data from a lacustrine succession requires a knowledge of the local processes that might control and modify the signal their effects need to be quantified and a robust calibration using the modern lake system is necessary to establish the relationship between the measured signal the isotopic composition of the host waters and climate

the sculptured hills of the taurus highlands implications for the relative age of serenitatis basin chronologies and the cratering history of the moon 1 new images from the lunar reconnaissance orbiter camera show the distribution and geological relations of the sculptured hills a geological unit widespread in the highlands between the serenitatis and crisium basins the sculptured hills shows knobby undulating radially textured and plains like morphologies and in many places is indistinguishable from the similarly knobby alpes formation a facies of ejecta from the imbrium basin the new lroc image data show that the sculptured hills in the taurus highlands is imbrium ejecta and not directly related to the formation of the serenitatis basin this occurrence and the geological relations of this unit suggests that the apollo 17 impact melts may not be not samples of the serenitatis basin forming impact leaving their provenance undetermined and origin unexplained if the apollo 17 melt rocks are serenitatis impact melt up to half of the basin and large crater population of the moon was created within a 30 ma interval around 3 8 ga in a global impact cataclysm either interpretation significantly changes our view of the impact process and history of the earth moon system

climate variability on the south eastern tibetan plateau since the lateglacial based on a multiproxy approach from lake naleng comparing pollen and non pollen signals a multi proxy lateglacial environmental record is described from lake naleng 31 10 degrees n 99 75 degrees e 4200 m above sea level situated on south eastern tibetan plateau to gain deeper insights into the hydrological and palaeoclimate development since 17 7 cal ka bp palynological reconstructions of variations in mean annual precipitation map and temperature mat sedimentological data and sediment chemistry including weathering indicators provide a multi faceted picture of local and regional environmental changes since the lateglacial principal component analyses of all parameters provide information on interrelationships between each parameters which help to evaluate their traceability to temperature and precipitation and to estimate their usability as proxy indicators for local and or regional variations during the lateglacial from 17 7 to 14 0 cal ka bp lake naleng experienced cold and dry climate conditions with low biological productivity and supply of unaltered fine grained material due to the high supply of glacier milk during the second half of the lateglacial climate conditions changed abruptly increases in mat from 4 to 2 2 degrees c and map from 500 mm to 820 mm between 14 0 and 13 0 cal ka bp indicate a climate amelioration this time interval can be correlated to the bolling allerod b a warming period in the north atlantic region and is followed by the younger dryas cold reversal indicated by abrupt decreases of mat from 2 2 to 5 degrees c and map from 820 to 650 mm the onset of the holocene at about 11 5 cal ka bp is indicated by rises in reconstructed mat from 5 to about 03 degrees c and map from 600 mm to 950 mm which led to an increased supply of weathered material and higher biological productivity between 5 0 and 3 0 cal ka bp mat increases to about 0 2 degrees c and map rises to maximum values of about 1000 mm followed by slightly decreasing mat and map between 3 0 and 0 cal ka bp the biogeochemical parameters total organic carbon toc c n delta c 13 org and weathering indicators e g the chemical index of alteration cia and sr ba are directly erosion of soils or indirectly changing provenance related to moisture availability on the south eastern tp and shows matching regional climate oscillations since the lateglacial in comparison to other lateglacial records from the tp map reconstructions from lake naleng indicate wetter climate conditions in the south eastern part of the tp and dryer conditions farther away from moisture sources c 2015 elsevier ltd all rights reserved

paleoclimate changes of the last 1000 yr on the eastern qinghai tibetan plateau recorded by elemental isotopic and molecular organic matter proxies in sediment from glacial lake ximencuo abstract total organic carbon corg and nitrogen ntot concentrations and isotope compositions and n alkane and n alkan ol molecular biomarker compositions were measured in two parallel sediment cores from lake ximencuo a typical glacial lake on the eastern qinghai tibetan plateau qtp to reconstruct local climatic variations during the past 1000 yr concentrations of corg and ntot vary similarly with changes in precipitation recorded by tree rings in dulan northeastern qtp indicating their close relation to precipitation carbon preference index cpi values of c22 c33 n alkanes and c22 c28 n alkan 1 ols and average chain length acl values of c27 c33 n alkanes generally negatively correlate with 13corg and 15ntot and also vary comparably with the oxygen isotope temperature record from the dunde ice core northeastern qtp these patterns indicate that high cpi values and negative shifts of the 13corg and 15ntot correspond to warmer conditions that favor the growth of vascular land plants and that lower values and positive shifts correspond to cooler conditions in the lake ximencuo locality this observation contradicts previous interpretations from peat and modern soil studies that conclude that the cpi indices were controlled by microbial degradation under different climate conditions here we propose that the changes of organic matter sources under different climate regimes combined with physiological adjustments of vascular plants to different air temperatures might yield different cpi responses to climate changes in glacial plateau lakes air temperature and precipitation increases and decreases reconstructed in this 1000 yr study were generally independent of each other but they both occurred at centennial or multi centennial scales the interaction between subtropical asian monsoon and mid latitude westerly atmospheric circulation systems probably dominated the local precipitation variations in the lake ximencuo catchment whereas solar insolation volcanism and greenhouse gas variations were likely responsible for the air temperature changes that are recorded in the lake sediments and that are consistent with regional temperature variations in the eastern qtp

late holocene isotope hydrology of lake qinghai ne tibetan plateau effective moisture variability and atmospheric circulation changes a sub centennial resolution record of lacustrine carbonate oxygen isotopes 18oc from the closed basin lake qinghai on the ne tibetan plateau shows pronounced variability over the past 1500 years changes in 18oc in hydrologically closed lakes are often interpreted in terms of changing effective moisture under this interpretation our record would imply increasing effective moisture during the little ice age lia compared to the medieval warm period mwp however independent evidence from other archives strongly suggests the asian summer monsoon was stronger during the mwp and weakened during the lia controls other than effective moisture the balance of water inputs over evaporative loss must therefore have contributed to the 18oc values we propose the lia signal in lake qinghai resulted from a reduction in evaporation caused by colder air temperatures coupled with a decrease in oxygen isotope composition of input waters as a result of an increase in the relative importance of westerly derived precipitation our results caution against simplistic interpretations of carbonate oxygen isotope records from hydrologically closed lakes and suggest all possible controlling factors must be taken into account in order to avoid misleading palaeoclimatic reconstructions

reduced early holocene moisture availability in the bayan har mountains northeastern tibetan plateau inferred from a multi proxy lake record abstract a late glacial and holocene lake sediment record from the northeastern tibetan plateau was investigated using ostracod and geochemical analysis after lake koucha was established about 16 cal ka bp oligohaline conditions gradually converted to mesohaline conditions about 10 cal ka bp clearly suggesting that the water body was a closed basin lake from about 10 cal ka bp the salinity of the lake rose continuously until hyperhaline levels were reached about 7 5 cal ka bp this increase in salinity was accompanied by a falling lake level extreme rainfall and flooding events in a generally dry climate hit the shallow saline lake around 8 5 cal ka bp causing a unique thin gravel containing layer within the continuous fine grained lake sediments the age control of our record does not allow us to correlate this event exactly to the widely recorded 8 2 cal ka bp event however the recovered sediments from lake koucha provide strong evidence that climate changes around 8 5 cal ka bp had significant environmental implications in northeastern tibet after about 7 3 cal ka bp the available moisture significantly increased causing a continuous salinity decline until the present day freshwater conditions of a through flow lake were established about 6 5 cal ka bp in lake koucha this major shift from a shallow saline to a deeper freshwater lake was probably accompanied by a fundamental change from a macrophyte dominated to a phytoplankton dominated lake a slight reduction in available moisture in comparison to the periods before and afterward was recorded between 4 3 and 2 0 cal ka bp in phase with numerous records from monsoonal asia the reconstructed overall change in moisture availability from dry conditions before about 7 3 cal ka bp to wetter conditions afterwards contradicts most palaeoclimate records from the tibetan plateau and its surroundings which show that wetter conditions in the early holocene were replaced by drier and probably cooler conditions in the mid and late holocene however in the semi arid region of lake koucha with a mean annual precipitation of about 500 mm the insolation driven strengthened monsoon in the early holocene may have resulted in a temperature rise and higher evaporation rates which outweighed the increase in precipitation and therefore led to significantly lower moisture availability our record provides further evidence for a regionally non uniform response of the available moisture evolution to the overall monsoonal signal in the holocene climate history of central asia

evaluation of lacustrine organic δ13c as a lake level indicator a case study of lake qinghai and the satellite lakes on the tibetan plateau abstract in recent years the sedimentary 13corg values have been recognized to be indicative of lake level changes in lakes on the tibetan plateau tp however the sensitivity of sedimentary 13corg to lake level changes and the potential relationship between lake level variations and climatic forces are still unknown in this particular region here we systematically evaluate sedimentary 13corg as a proxy of lake level changes in lakes with different sizes on the tp consistent with previous studies the total organic matter of sediments was mainly contributed by aquatic plants in lakes on the tp in the studied lakes sedimentary 13c values mainly reflect lake level changes as the species of aquatic plants with different 13corg values strongly respond to lake level however sedimentary 13c values are much more sensitive to lake level changes in a moderate depth lake 10 m than those in a deep lake 27 m or a shallow lake

shock metamorphism and petrography of the shergotty achondrite the shergotty subsamples 1 and 12 consist of augite and pigeonite 67 5 maskelynite 24 ilmenite and titanomagnetite 2 pyrrhotite 0 4 whitlockite 1 8 apatite 0 1 quartz 0 5 baddeleyite trace fayalite 0 4 mesostasis 3 and shock induced local polymineralic melt products 0 6 the overall modal composition is similar to other shergotty samples except for the rather high whitlockite content the shock effects observed in the mineral constituents include mosaicism deformation bands planar fractures and mechanical twin lamellae in clinopyroxene isotropization of plagioclase with very rare remnants of birefringence planar deformation structures mosaicism and strongly reduced birefringence in quartz mechanical twinning of ilmenite localized in situ melting of neighbouring minerals at the contact of low and high density phases based on the refractive index of maskelynite average 1 5467 with average an content of 49 and the degree of isotropization of the plagioclase an equilibrium shock pressure of 29 1 gpa is derived the inferred post shock temperature is 200 20 c no heating event could have exceeded 400 c duke 1968 local stress and temperature concentrations reach 60 80 gpa and 1600 2000 c the observed shock effects can be explained by a single shock event a second weaker shock event as found by others appears to be highly improbable equilibrium shock pressures and post shock temperatures for the other known shergottites are 31 2 gpa and 220 50 c zagami 43 2 gpa and 400 800 c alha 77005 the pressure estimate for eeta 79001 by lambert 1985 is confirmed 34 1 gpa the post shock temperature is 250 50 c the abundance and textural setting of localized melt products in these meteorites confirm increasing shock pressures in the sequence shergotty zagami eeta 79001 alha 77005 undoubtedly the melts could have been formed by the same single shock which produced the equilibrium shock effects e g maskelynitization in these meteorites the shock induced particle velocities inferred from hugoniot data of basalts are in the 1 5 2 0 km s range for the parental rocks of the shergottites ejection velocities are therefore in the order of 3 4 km s special ejection mechanisms are required in order to exceed the escape velocity of a planet like mars without producing higher degrees of shock e g melting than those observed in the shergottites

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

palaeoclimatic changes in the qinghai lake area during the last 18 000 years abstract multi proxy analysis of a sediment core from qinghai lake including pollen carbonate toc tn and 13 c of organic matter was used to document regional climatic changes during the last 18 000 years climate was very cold and dry before 16 9 cal kyr bp the warm and wet period which began at about 14 1 cal kyr bp culminated at 6 5 cal kyr bp and came to its end at about 4 5 cal kyr bp after that the climate gradually became colder and drier during the transitional period from the late glacial to the holocene the climate fluctuated frequently the short term climatic oscillations including the bolling allerod younger dryas and the cooling event at ca 8 2 cal kyr bp appear to be recorded in the qinghai lake sedimentary record the climatic evolution in the qinghai lake area during the past 18 000 years indicates that solar insolation changes on the ten thousand year scale are the likely driving force of the east asia monsoon

carbon isotopes in surface sediment carbonates of modern lake qinghai qinghai tibet plateau implications for lake evolution in arid areas to further investigate the significance of carbon isotopes of lake carbonates in arid areas we examined the carbon isotopic composition of ostracods bulk carbonate fine grained carbonates and associated water dic dissolved inorganic carbon from lake qinghai and several small lakes and ponds surrounding lake qinghai we obtained three major results 1 the carbon isotopic compositions of ostracods bulk carbonate and fine grained carbonates in the lakes and ponds are clearly correlated with water 13cdic values which vary with water salinity in the lake qinghai area 2 the variation in the 13cdic values of lake water is mainly controlled by co2 exchanges between the atmosphere and lake waters in the lake qinghai area 3 ostracods bulk carbonate and fine grained carbonates show consistent trends of isotopic composition in the study area and the differences in carbon isotopic composition between authigenic carbonates and ostracods may be explained by the differences in carbon isotopic composition between the dic of surface water and that of the water near to the sediment water interface as well as the vital offsets of ostracods our results suggest that variations in the 13c values of carbonates in lake qinghai and other lakes in this arid high altitude area are primarily controlled by the carbon isotope ratios of the lake water dic which in turn are related to water salinity therefore changes in carbonate 13c values may be used to indirectly indicate changes in water salinity in the lake qinghai area

characteristics and significance of two pre late wisconsinan weathering profiles adirondacks usa and miramichi highlands canada abstract the properties of two weathering profiles developed from granitic rocks and covered by deposits of wisconsinan age were studied in order to characterize saprolites and non saprolite residuum of the glaciated area of northeastern north america the warrensburg profile adirondacks new york is more than 9 m thick and formed on a hornblende granitic gneiss total chemical analysis of the sandy saprolite shows slight losses compared to bedrock kaolinite is the main weathering product in the

evaluation of oxygen isotopes in carbonate as an indicator of lake evolution in arid areas the modern qinghai lake qinghai tibet plateau abstract the oxygen isotopic composition of carbonate in lakes has been used as a useful indicator in palaeolimnological research and has made some important contributions to our understanding of lacustrine systems for modern lakes in arid or cold areas however there are few data available to test the effect of lake salinity and temperature on the oxygen isotopic composition of various carbonate sources such as ostracod bulk carbonate and fine grained carbonate for arid high altitude lake qinghai our results suggest that variations in the 18o values of carbonate in lake qinghai are mainly controlled by the oxygen isotope ratio of the lake water changing with water salinity as a secondary effect increasing water depth leads to cooler bottom and surface water which may result in more positive 18o values of ostracod and bulk carbonate

an organic carbon isotopic record of glacial postglacial change in atmospheric pco2 in the sediments of lake biwa japan a 12 m piston core of sediment from lake biwa japan provides a high resolution record of sedimentary organic matter accumulation over the pleistocene holocene transition organic carbon concentrations are generally 1 2 in sediments deposited since 15 kyr ago c n ratios indicate that the organic matter is predominantly from aquatic production a shift in organic carbon isotopic composition from 21 to 25 occurs over the glacial postglacial boundary changes in lake productivity organic matter preservation sources of organic matter and water temperature can be eliminated as probable causes of the observed organic carbon isotopic shift annual overturn of lake waters and rapid dissolution of biogenic carbonates maintain equilibrium between atmospheric co2 and dissolved co2 in this lake the isotopic composition of organic matter buried in the sediments of lake biwa consequently appears to record the shift in atmospheric pco2 from 200 ppm to 280 ppm which occurred at the pleistocene holocene transition

water depth affecting thaumarchaeol production in lake qinghai northeastern qinghai tibetan plateau implications for paleo lake levels and paleoclimate abstract archaeal glycerol dialkyl glycerol tetraethers gdgts are increasingly popular and versatile tool for palaeolimnology studies but their applications in paleohydrology are scarce especially for thaumarchaeol which is specific for the newly proposed phylum thaumarchaeota after investigating our published gdgt data of lake qinghai we found that both the concentration of thaumarchaeol and the relative abundance of thaumarchaeol to total archaeal gdgts thaum in core top sediments increased significantly with increasing water depth r 0 88 and 0 95 respectively with lower concentrations of 5 5 ng g in shallow areas water depth 10 m this is likely because that the producers of thaumarchaeol thaumarchaeota prefer living in the relative deeper zone in lacustrine systems where probably both competition of ammonium the substrate from other microbes and light intensity are low therefore we proposed that thaumarchaeol was mainly produced in situ and changes in thaum might reflect water depth variations in this closed basin lake the application of thaum as a water depth indicator in a holocene sediment sequence of core qh 2011 provided a high resolution relative lake level history of lake qinghai which resembles that inferred from the 13corg value obtained in the same core this supports the use of thaum as an indicator of lake water depth in paleohydrology studies especially for medium lakes moreover the records of the two independent proxies in core qh 2011 confirmed a shallow lake qinghai in the early holocene and a late holocene highstand highlighting the importance of local temperature and evaporation loss in controlling effective moisture in the arid semi arid region

distribution of the c37 tetra unsaturated alkenone in lake qinghai china a potential lake salinity indicator abstract the alkenone unsaturation index u k 37 has been applied to reconstruct past temperature changes in both marine and lacustrine systems however few studies have addressed whether the relative abundance of the c 37 4 alkenone to the total c 37 production c 37 4 can reflect surface salinity changes in lacustrine systems here we present long chain c 37 alkenone distribution patterns in surface sediments from lake qinghai china surface sediments were sampled over a large range of surface salinity changes 1 7 25 g l within lake qinghai and its surrounding lakes while temperature differences at these sampling locations should be relatively small we have found that c 37 4 varies from 15 to 49 as surface salinity decreases we tentatively describe this c 37 4 salinity link with a general linear regression c 37 4 53 4 7 8 1 73 0 45 s n 28 r 2 0 62 although step wise c 37 4 changes in response to salinity variation may exist u k 37 values vary between 0 10 and 0 16 at these sites and the inferred range of lake water temperature changes is 2 3 c suggesting that u k 37 largely reflects temperature signal across a large salinity range consistent with previous findings that u k 37 can indicate temperature changes over a large diversity of environmental settings we have also found that u k 37 values are correlated with salinity changes r 2 0 4 and thus cannot exclude potential temperature effect on c 37 4 and salinity effect on u k 37 in this study however even extreme estimates of temperature differences within the lake are still unable to explain the observed c 37 4 changes we therefore suggest that c 37 4 could be used to infer past lake salinity changes at a regional scale

an overview of the role of weathering in the production of quartz silt abstract quartz silt is a widespread detrital sediment with large aeolian loess and alluvial silt deposits forming important components of many contemporary landscapes despite research findings which indicate that a range of opportunities exist for the comminution of quartz into silt particles within a wide variety of geomorphic environments e g glacial grinding fluvial comminution aeolian abrasion frost weathering salt weathering insolation weathering and deep weathering the glacial aeolian hypothesis has traditionally been favoured as the most likely explanation for loess formation and loess is seen as primarily a quaternary phenomenon as a consequence there has been a tendency to underestimate sediment inputs into loess systems by geomorphological processes operating within pre quaternary environments in particular earth scientists may have considerably underestimated the role of weathering in global silt generation as there are now many references to the existence of a patchy but widespread distribution of pre quaternary weathering profiles across the glacial and periglacial landscapes of the northern hemisphere e g north america british isles north and central europe landscapes within which many of the classical loess deposits are located these observations suggest that weathering profiles may have covered large tracts of the northern hemisphere land surface prior to the quaternary glaciations this in turn may have important implications for quartz silt generation as 1 experimental studies indicate that many weathering processes are capable of generating significant quantities of silt sized debris and 2 particle characteristics displayed by saprolitic material that has developed on quartz rich crystalline source rocks often include significant quantities of either silt sized material or quartz grains that are weakened by weathering derived microfractures thus weathering profiles may represent mines of actual and potential quartz silt available for release into sedimentary systems when these profiles are subsequently reworked by geomorphological processes such as glacial fluvial and aeolian erosion

lake qinghai china closed basin like levels and the oxygen isotope record for ostracoda since the latest pleistocene abstract in 1985 a sino swiss limnogeological expedition to china s largest inland lake recovered seismic profiles and piston cores to help calibrate palaeoclimatic models of monsoon and insolation fluctuations over the northern tibet qinghai plateau since the last glacial maximum lake qinghai a perennial lake with an area of 4278 km2 1985 at 3194 m above sea level receives drainage from 30 000 km2 of catchment near the northwest corner of the plateau the 26 5 m deep terminal lake 1985 with brackish alkaline magnesium sulphate rich waters 14 g 1 1 tds has not overflowed since the last glacial but its levels have responded to climatic and hydrologic changes seismic reflection profiles for the sub bottom sediment structures revealed a complex topography with channels relict terraces tectonic tilting and deformation in deposits buried under a 4 6 m packet of mainly flat bedded sediments from which core samples were recovered the lowermost cored material 14 500 yr b p comprises mainly water lain loess deposited in a smaller flood plain lake of up a few metres depth under cold arid climatic conditions ams radiocarbon dating indicates average sedimentation rates for latest pleistocene and holocene deposits in central basin regions of 0 3 0 5 mm yr 1 the 18o values of fossil ostracod valves provide a record of changes in the isotopic chemistry of the lake waters that can be related to the precipitation evaporation budgets which have controlled the palaeo levels for lake qinghai the precipitation evaporation budget for the lake qinghai region is largely determined by the asian monsoon system the lake qinghai sediment record shows that there was no large influx of glacoer melt waters into the lake basin during the post glacial the regional climate remained arid until at least 12 500 yr b p when an incipient monsoon was possibly initiated river transported silts first reached the basin centre at 11 800 yr b p when the lake depth may have increased to 5 m possibly a monsoonal weakening for several centuries after 10 800 yr b p europe younger dryas caused a further period of aridity at 10 200 yr b p the basin began filling towards modern lake dimensions in response to a permanent strengthening of the asian monsoon substantial lake level rises probably characterised the periods 10 200 9800 9500 8500 8300 7200 yr b p and through perhaps a century at about 6800 yr b p decreasing levels probably characterised the intervening intervals short term lake level fluctuations through the mid holocene climatic optimum were minimal indicating a very stable climatic hydrologic regime an isotopic steady state for the lake waters since 3000 500 yr b p obscures the climatic hydrologic regime dependent 18o gradient but there is little stratigraphic evidence to suggest that the lake level has been significantly below its present level since that time three negative 18o excursions for the lake waters may correspond to known glacier advances on the plateau at 3000 2000 and 1500 yr b p during china s neoglacial

apollo 16 site geology and impact melts implications for the geologic history of the lunar highlands the geology of the apollo 16 site is reconsidered on the basis of data from photogeology geochemical remote sensing and lunar samples the site possesses an upper surface of anorthositic gabbro and related rocks mafic components were deposited as basin ejecta the events involved in its geological evolution were the nectaris impact and the imbrium impact the role of large local craters in the history of the region was to serve as topographic depressions to accumulate basin ejecta the most abundant melt composition at apollo 16 is an aluminous variety of lkfm basalt supplied by the nectaris impact as ejected basin impact melt the mafic lkfm melt may have been supplied by the imbrium impact more aluminous melt groups are probably derived from local small craters the remainder of the deposits in the region are composed of anorthositic clastic debris derived from the nectaris basin the local crustal substrate and imbrium and other basins

micro x ray diffraction assessment of shock stage in enstatite chondrites abstract a new method for assessing the shock stage of enstatite chondrites has been developed using in situ micro x ray diffraction xrd to measure the full width at half maximum fwhm of peak intensity distributed along the direction of the debye rings or chi angle corresponding to individual lattice reflections in two dimensional xrd patterns this xrd technique differs from previous xrd shock characterization methods it does not require single crystals or powders in situ xrd has been applied to polished thin sections and whole rock meteorite samples three frequently observed orthoenstatite reflections were measured 020 610 and 131 these were selected as they did not overlap with diffraction lines from other phases enstatite chondrites are commonly fine grained stained or darkened by weathering shock induced oxidation and metal sulfide inclusions furthermore most e chondrites have little olivine or plagioclase these characteristics inhibit transmitted light petrography nevertheless shock stages have been assigned macalpine hills mac 02837 el3 s3 pecora escarpment pca 91020 el3 s5 mac 02747 el4 s4 thiel mountains til 91714 el5 s2 allan hills alha 81021 el6 s2 elephant moraine eet 87746 eh3 s3 meteorite hills met 00783 eh4 s4 eet 96135 eh4 5 s2 lewis cliff lew 88180 eh5 s2 queen alexandra range que 94204 eh7 s2 lapaz icefield lap 02225 eh impact melt s1 for the six with published shock stages there is agreement with the published classification fwhm plotted against petrographic shock stage demonstrates positive linear correlation fwhm ranges corresponding to shock stages were assigned as follows s1 3 5 s6 not measured slabs of abee eh impact melt breccia and northwest africa nwa 2212 el6 were examined using xrd alone fwhm values place both in the s2 range consistent with literature values micro xrd analysis may be applicable to other shocked orthopyroxene bearing rocks

total organic carbon isotopes a novel proxy of lake level from lake qinghai in the qinghai tibet plateau china abstract the isotopic compositions of total organic carbon toc in lakes have been widely used to interpret paleoclimatic changes and the depositional environments of lake sediments however the main factors that affect the carbon isotopes of toc source of organic material water condition and others may vary in different lake sediment records which have limited the applicability of organic carbon isotopes in explaining biogeochemical and environmental changes in lakes in this study the organic carbon isotopic compositions of aquatic plants and surface sediments from lake qinghai and the living terrestrial plants and surface soils around the lake were systematically investigated to identify the sources of toc in the sediments and the significance of the organic carbon isotopes of sedimentary toc we found that the aquatic plants in the deep water areas 10 m were primarily dominated by cladophora but submerged plants potamogeton and ruppia l are the dominant species in shallow water 13 c org values 33 6 to 28 6 that are caused by c 3 like photosynthesis but the submerged plants have enriched 13 c org values 17 8 to 15 4 that are caused by c 4 like photosynthesis in addition the 13 c org values of cladophora become more negative with increasing water depth because of the slow photosynthetic rate caused by the weak light intensity at depth the isotopic data indicate that the carbon isotopes of organic material in the surface sediments are primarily controlled by the types of aquatic plant and that the 13 c org values of toc can be used to indicate the variation of the water depth lake level the organic carbon isotopic data from the 1f core showed that the water was shallow

biogeochemical and micro facial fingerprints of ecosystem response to rapid late glacial climatic changes in varved sediments of meerfelder maar germany the response of a lacustrine ecosystem to climatic changes from 13 500 to 10 800 bp was studied in a varve dated sediment profile of lake meerfelder maar western germany bulk biogeochemical parameters stable carbon and nitrogen isotopes of sedimentary organic matter and micro facies analysis are used for a detailed investigation of the lake s development from the allerod interstadial al to the younger dryas stadial yd and into the early holocene preboreal varve micro facies reveal rapid changes in composition and seasonal structure of the depositional environment mainly in temporal accordance with changes of terrestrial biozones the respective responses of bulk proxy parameters bi decadal resolution indicate different sensitivities to diverse climatic changes a prominent transition took place within two decades at the al yd boundary 12 690 12 670 bp increased flux of nutrients released from redeposited littoral sediments and shorter yd summer seasons led to an acceleration and concentration of lacustrine primary production with reduced discrimination against 13c high lacustrine primary production was further favored by relatively warm yd summer temperatures at 12 240 varve years bp from 1 year to the next a regular deposition of detrital layers in spring set in which is related to local hydrologic threshold processes amplifying the response to increased snowmelt discharge this distinct change in the middle of the yd is clearly detected by varve micro facies but not equally recorded in organic bulk proxy data especially carbon isotope ratios remain constant and indicate a negligible effect of this process on the productivity of lacustrine algae the yd preboreal transition 11 645 11 585 bp is marked by a characteristic change in micro facies throughout this transition stable carbon isotope ratios strongly decline while the accumulation of opal and organic matter om remained constant this is seen as an increasing importance of spring and autumn for gross primary production at the onset of the holocene

shock barometer using cathodoluminescence of alkali feldspar 1 color cathodoluminescence cl images of unshocked and experimentally shocked sanidine at pressures up to 40 1 gpa showed red violet emission below 20 0 gpa and blue emission above 20 0 gpa the phases in these shock recovered samples were identified as crystalline feldspar for red violet emitting areas and as diaplectic feldspar glass for blue emitting ones by micro raman spectroscopy cl spectra of these shocked sanidine have emissions at 330 380 and 400 420 nm of which intensities increase with an increase in shock pressure similar uv blue emissions were found in alkali feldspar and the glass in martian meteorites and ries crater impactite the deconvolution of these cl spectra provides the emission component at 2 948 ev assigned to shock induced defect center where this intensity correlates linearly with peak shock induced pressure on sanidine with little dependence on composition and structure the correlation gives quantitative values of the shock pressures experienced by the feldspar resulting in estimated shock pressures of martian meteorites and ries crater impactite the cl intensity of feldspar has a potential for a universal shock barometer with high spatial resolution 1 m and in a wide pressure range theoretically 4 5 40 1 gpa this leads to a breakthrough in understanding the impact histories on earth moon and mars

a heterogeneous lunar interior for hydrogen isotopes as revealed by the lunar highlands samples knowing the amount and timing of water incorporation into the moon has fundamental implications for our understanding of how the earth moon system formed water has been detected in lunar samples but its abundance distribution and origin are debated to address these issues we report water concentrations and hydrogen isotope ratios obtained by secondary ion mass spectrometry sims of plagioclase from ferroan anorthosites fans the only available lithology thought to have crystallized directly from the lunar magma ocean lmo the measured water contents are consistent with previous results by fourier transform infrared spectroscopy ftir combined with literature data d values of lunar igneous materials least degassed at the time of their crystallization range from 280 to 310 the latter value being that of fan 60015 corrected for cosmic ray exposure we interpret these results as hydrogen isotopes being fractionated during degassing of molecular hydrogen h 2 in the lmo starting with the magmatic d value of primordial water at the beginning of lmo being about 280 evolving to about 310 at the time of anorthite crystallization i e during the formation of the primary lunar crust the degassing of hydrogen in the lmo is consistent with those of other volatile elements the wide range of d values observed in lunar igneous rocks could be due to either various degrees of mixing of the different mantle end members or from a range of mantle sources that were degassed to different degrees during magma evolution degassing of the lmo is a viable mechanism that resulted in a heterogeneous lunar interior for hydrogen isotopes

chemical weathering studies in relation to geomorphological research in southeastern canada abstract although chemical weathering provides fundamental information relevant to geomorphology the subject has been overlooked during the 20th century in canada this paper provides an overview of the current state of canadian research on chemical weathering in southeastern canada and takes into account three spatial and temporal contexts 1 the formation of bedrock morphology by chemical weathering 2 occurrences characteristics and age of saprolites and 3 contemporary chemical denudation rates long term geomorphological evolution of southeastern canadian landscapes shows that chemical weathering has played an important role an example is taken from the laurentide region of the canadian shield north of montreal quebec the present topography resulted from the stripping of the former weathering mantle and from the probable subsequent modification of the weathering front first by the action of hillslope processes and rivers and then by glaciers before and during plio pleistocene times the present landscape reflects the timing of the formation of erosion surfaces and of the stripping of the paleozoic cover rocks and exposure of the shield since the late seventies several isolated occurrences of saprolite soil profiles have been discovered in eastern canada and prompted a renewal of the study of these materials about the cenozoic evolution of these regions one of the problems in this field of research is the dating of saprolites and their inclusion in a chronostratigraphic framework along with the other cenozoic surficial deposits and landforms because of the multiple factors involved in the development of secondary minerals in saprolites during the course of weathering it is preferable to distinguish the dating of saprolites from the study of their mineralogical and geochemical evolution fortunately several new techniques are becoming available for the absolute dating of surficial deposits and saprolites including the use of cosmogenic radionuclides saprolites provide a strong potential field of research for our understanding of the geological evolution of eastern canada during the cenozoic contemporary weathering and erosion rates are fields of research that have gained increasing interest recently since modeling landscape geochemical response can be applied to various environmental stress situations such as acidification by rain and forest harvesting rock type may be the main factor explaining the large differences between watersheds in fact variability of cation removal in the temperate zone is probably most closely related to flow paths of water investigations at different scales from entire watersheds to slopes to individual pedons highlight the problem in the catamaran brook watershed new brunswick water chemistry is explained by a mix of groundwater and soil solution from the horizons at the base of the floodplain soils geochemical mass balances based on net outputs give little information on the weathering reactions of primary minerals the weathering products or on the nature of the weathering processes that provide the dissolved load of streams mineralogic and petrographic analysis of selected soil pedons are necessary to determine weathering reactions and their role as sources or sinks for bases silica aluminum and iron in the various compartments through which water percolates before it reaches the stream

stable isotopes in bulk carbonates and organic matter in recent sediments of lake qinghai and their climatic implications abstract multi proxy indices on annual decadal scales during the past 600 years were developed from the surface sediments of lake qinghai based on 210pb and 137cs geochronology the 13ccarb 18ocarb and total carbonate content are consistent with one another in trends and their variations have been mainly ascribed to regional temperature it is suggested that the strong evaporation contributes in modifying 18o of lake water and 13c of the dissolved inorganic carbon of the surface water and appears to be responsible for the covariance between 13ccarb and 18ocarb photosynthesis of the aquatic plants appears to have played a significant role in determining 15n of organic matter the discrimination of 14n and 15n during photosynthesis may have triggered a positive linkage between temperatures and 15norg after removal of the stratigraphic trend variations of total organic carbon toc c n ratio and 13corg have been ascribed to local precipitation toc after removal of the stratigraphic trend is positively correlated with the c n ratio r 0 45

toward quantification of strain related mosaicity in shocked lunar and terrestrial plagioclase by in situ micro x ray diffraction studies of shock metamorphism of feldspar typically rely on qualitative petrographic observations which while providing invaluable information can be difficult to interpret shocked feldspars therefore are now being studied in greater detail by various groups using a variety of modern techniques we apply in situ micro x ray diffraction xrd to shocked lunar and terrestrial plagioclase feldspar to contribute to the development of a quantitative scale of shock deformation for the feldspar group andesine and labradorite from the mistastin lake impact structure labrador canada and anorthite from earth s moon returned during the apollo program were examined using optical petrography and assigned to subgroups of the optical shock level classification system of stoffler 1971 two dimensional xrd patterns from the same samples revealed increased peak broadening in the chi dimension due to strain related mosaicity with increased optical signs of deformation measurement of the full width at half maximum along fwhm of these peaks provides a quantitative way to measure strain related mosaicity in plagioclase feldspar as a proxy for shock level