composition of middle late eocene salt lakes in the jintan basin of eastern china evidence of marine transgressions abstract abundant continental salt deposits were formed in salt basins in eastern china around the cretaceous tertiary periods however whether these evaporites had a marine or non marine origin remains controversial the jintan basin is located between south china and north china and has a series of very thick relatively pure salt deposits such that data from the salt deposits in the jintan basin could provide new evidence of marine transgression the large scale of these salt deposits implies the supplies of marine transgression primary fluid inclusions in the halite deposits of the jintan basin have recorded the composition of the evaporated salt lake water the br contents in halite range from 2 to 16 ppm and clearly higher than inland non marine salt deposits in the yunying depression jianghan basin south china the 37cl values of marine salt deposits across different geological eras range from 1 to 1 the 37cl values from halite in the jintan basin range from 0 66 to 0 23 close to zero indicating a possible marine origin our analyses from fluid inclusions in halite show k varies from 0 7 to 15 8 g l mg from 1 1 to 3 1 g l sulfate ion from 3 7 to 27 7 g l in the samples the composition of fluid inclusions in halite from a sample in the lower part of the halite section in the jintan basin is very similar to marine seawater on janecke diagram the 34s of anhydrite deposits 26 32 to 26 51 are also very similar to contemporary seawater thus the evidence indicates the jintan basin was supplied sporadically by marine transgressions

salinity history of the earth s early ocean it is commonly thought that the oceans are becoming saltier with time as sodium and chlorine are weathered out of continental rocks and transported to the sea here we argue that the salinity of the early ocean was 1 5 to 2 times the modern value and that it did not decline significantly until surprisingly late in the earth s history if correct this theory could help explain why the evolution of higher life took so long

el nino evolution during the holocene revealed by a biomarker rain gauge in the galapagos islands abstract the el nino southern oscillation enso represents the largest perturbation to the climate system on an inter annual time scale but its evolution since the end of the last ice age remains debated due to the lack of unambiguous enso records lasting longer than a few centuries changes in the concentration and hydrogen isotope ratio of lipids produced by the green alga botryococcus braunii which blooms during el nino rains in the galapagos islands indicate that the early holocene 9200 5600 yr bp was characterized by alternating extremes in the intensity and or frequency of el nino events that lasted a century or more our data from the core of the enso region thus calls into question earlier studies that reported a lack of el nino activity in the early holocene in agreement with other proxy evidence from the tropical pacific the mid holocene 5600 3500 yr bp was a time of consistently weak el nino activity as were the early middle ages 1000 1500 yr bp el nino activity was moderate to high during the remainder of the last 3500 years periods of strong or frequent el nino tended to occur during peaks in solar activity and during extended droughts in the united states great plains linked to la nina these changing modes of enso activity at millennial and multi centennial timescales may have been caused by variations in the seasonal receipts of solar radiation associated with the precession of the equinoxes and or changes in solar activity respectively

a new discovery of early cretaceous wealden amber from the isle of wight a new discovery of in situ amber is reported from the southwest coast of the isle of wight the productive site is located within the wealden marls wessex formation generally regarded to be of earliest barremian early cretaceous age also making this amber amongst some of the oldest known occurrences in the world amber globules can be found within two thin black lignite horizons which form a channel lag deposit exposed in the cliffssoutheast of chilton chine examination of plant material above and below this site by other workers combined with infrared spectra of the amber in this study implies a coniferous possibly taxodiaceous origin for this resin palaeoenviron mental interpretation of the chilton chine site suggests that the amber was exuded locally and in some cases the globules have beenpartly replaced by iron pyrite

louann salt geochemistry gulf of mexico sedimentary basin u s a a preliminary synthesis abstract samples of jurassic salt and anhydrite were obtained from throughout the gulf of mexico sedimentary basin salt samples have been analyzed for bromide content and 87 sr 86 sr of anhydrite inclusions and anhydrite for 87 sr 86 sr most samples of diapiric salt contain 87 sr 86 sr ratios are commonly radiogenic relative to the ratio in presumed coeval jurassic callovian seawater both these observations suggest that during deformation salt undergoes extensive rock water interaction losing bromide to the reacting brines and incorporating radiogenic sr similar behavior of anhydrite during deformation with respect to sr is also observed samples of deeply buried salt exhibit bromide concentrations consistent with the precipitation of marine halite but include several samples with extremely high values few 87 sr 86 sr ratios however seem to be characteristic of coeval callovian seawater samples with normal bromide content but radiogenic sr suggest primary deposition from or recrystallization in the presence of radiogenic fluids with marine like bromide content samples with extremely high bromide content and radiogenic sr values suggest recrystallization in fluids with elevated bromide content due to loss of bittern phases or extensive rock water interaction of bedded salt during deep burial the data suggest a dynamic system in which physical modification of evaporites during deformation and deep burial is accompanied by chemical modification

dolomitization history and porosity evolution of a giant deeply buried ediacaran gas field sichuan basin china abstract the deeply buried 7 km upper ediacaran sinian dengying formation ca 551 1 541 ma in the sichuan basin china is the largest precambrian dolostone gas reservoir worldwide gas exploration from the dengying formation however is hampered by a limited understanding of its complex dolomitization history and porosity evolution new petrological geochemical and petrophysical analyses were performed and are discussed here to develop a better understanding of the formation s complexities microbialite dolo grainstone and crystalline dolostone lithologies from the platform margin have high primary porosities relative to dolo mudstone and less common microbialite lithologies from the low energy platform interior spatially variable primary porosity was subsequently overprinted by meteoric dissolution and dolomitization often inducing secondary porosity the various forms of dolomitization sabkha reflux and burial dolomitization and cementation increased the resistivity of these rocks to chemical and physical compaction and porosity destruction in the deep burial domain medium to coarse crystalline dolomite cements and saddle dolomite precipitated at fluid temperatures of 120 160 c and 160 220 c respectively the significance of deep burial dissolution is critically discussed and constrained by i corrosion of late diagenetic minerals ii pores cross cutting or forming around stylolites and iii the occurrence of solid bitumen in the center of secondary pores vuggy inter and intracrystalline pores developed during a late and deep burial stage and comprise ca 20 of the overall dengying reservoir porosity mechanisms which induced corrosion at this burial stage include hydrothermal pulses and thermochemical sulfate reduction similar to many carbonate reservoirs in the phanerozoic this study documents that the platform margin has better porosities and higher gas production compared to the platform interior due to its specific carbonate rock properties and diagenesis data shown here document the complex multiphase dolomitization history and high potential for gas production from deeply buried precambrian dolostone reservoirs

high archean climatic temperature inferred from oxygen isotope geochemistry of cherts in the 3 5 ga swaziland supergroup south africa new and compiled oxygen isotope data combined with the results of geological and sedimentological studies demonstrate that enclaves of synsedimentary to very early diagenetic cherts are widely preserved in the 3 5 3 2 ga swaziland supergroup barberton greenstone belt south africa the low 1 8 o values of these cherts indicate extremely high ocean temperatures of 55 85 c previously the large depletion in 1 8 o shown by all barberton cherts relative to their phanerozoic counterparts has been attributed to low 1 8 o in archean oceans chert formation during late diagenesis wholesale loss of 1 8 o during alteration and or regional silicification of sediments around hot springs these alternative explanations are not compatible with the new results cherts in the onverwacht group display an isotopic stratigraphy that is inversely repeated in conglomerates in the overlying fig tree and moodies groups demonstrating that the chert 8 0 o values were fixed prior to archean uplift and erosion which started at 3 26 ga the maximum 1 8 o value in barberton cherts 22 is lower than the minimum values 23 in phanerozoic bedded cherts precluding late diagenesis as the explanation of the overall low 1 8 o values regional metamorphic hydrothermal or long term resetting of original 1 8 o values is also precluded by preservation of 1 8 o values across different metamorphic grades and by systematic 1 8 o differences among interbedded chert types stratigraphic units and conglomerate clasts the 7 1 8 o variation of these archean cherts is similar to that of phanerozoic deep sea cherts formed when opal converted to microquartz during burial but the actual archean values are 10 lower marine opal was apparently converted to microquartz during burial to depths of 1 km cherts with 1 8 o 15 reflect conversion during deepest burial or in local areas of enhanced geothermal gradient and or hydrothermal activity cherts with higher 1 8 o values formed during early diagenesis and indicate an extremely hot archean ocean and surface environment

climate change and cultural response around 4000 cal yr b p in the western part of chinese loess plateau new data suggest that dramatic environmental change in the western loess plateau of china corresponded with substantial changes in human demography ca 4000 cal yr b p these data demonstrate that a rapid climatic transition from wet to dry led to an ecologically devastated period between 4090 and 3600 cal yr b p the sudden reduction in the number of archaeological sites during this period namely a reduction in the total number of sites and a contraction of the areal distribution of sites points to declining agricultural productivity associated with widespread aridification beginning at 4000 cal yr b p 2005 published by university of washington

early to mid holocene lake high stand sediments at lake donggi cona northeastern tibetan plateau china lake high stand sediments are found in three onshore terraces at lake donggi cona northeastern tibetan plateau and reveal characteristics of hydrological changes on lake shorelines triggered by climate change geomorphological processes and neo tectonic movements the terraces consist of fluvial alluvial to littoral lacustrine facies end member modeling of grain size distributions allowed quantification of sediment transport processes and relative lake levels during times of deposition radiocarbon dating revealed higher than modern lake levels during the early and mid holocene lake levels follow the trend of asian monsoon dynamics and are modified by local non climatic drivers site specific impacts explain fluctuations during the initial lake level rise 11 cal ka bp maximum lake extension reached 9 2 cal ka bp at 16 5 m above present lake level a p l l littoral and lacustrine sediment deposition paused during a phase of fluvial activity and post depositional cryoturbations at 8 5 cal ka bp when the lake level fell to 8 m a p l l after a second maximum at 7 5 cal ka bp lake level declined slightly at 6 8 cal ka bp probably due to a non climatic pulse that caused lake opening the level remained high until a transition towards drier conditions 4 7 cal ka bp though discontinuous high stand sediments provide a unique high resolution archive

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

el nino as a mediator of the solar influence on climate 1 using a climate model of intermediate complexity we simulate the response of the el nino southern oscillation enso system to solar and orbital forcing over the holocene solar forcing is reconstructed from radiocarbon production rate data using various scaling factors to account for the conflicting estimates of solar irradiance variability as estimates of the difference since the maunder minimum range from 0 05 to 0 5 of the solar constant we consider these two extreme scenarios along with the intermediate case of 0 2 we show that for large or moderate forcings the low pass filtered east west sea surface temperature gradient along the equator responds almost linearly to irradiance forcing with a short phase lag about a decade wavelet analysis shows a statistically significant enhancement of the century to millennial scale enso variability for even a moderate irradiance forcing in contrast the 0 05 case displays no such enhancement orbitally driven insolation forcing is found to produce a long term increase of enso variability from the early holocene onward in accordance with previous findings when both forcings are combined the superposition is approximately linear in the strong scaling case overall the sea surface temperature response is of the magnitude required and is persistent enough to induce important climatic perturbations worldwide the results suggest that enso may plausibly have acted as a mediator between the sun and the earth s climate a comparison to key holocene climate records from the northern hemisphere subtropics and midlatitudes shows support for this hypothesis

atmospheric gas in modern and ancient halite fluid inclusions a screening protocol abstract halite possesses great potential for hosting and storing information vital to the reconstruction of earth s ancient climate seawater chemistry and evolving atmosphere here we propose a screening protocol that not only distinguishes between primary and secondary halite but also identifies fluid inclusions that carry original gas trapped during the primary crystallization process an integrated multi analytical protocol is presented for sample preparation petrographic evaluation analytical measurements and distinguishing original gases and contents from contaminants the screening protocol starts with the visual inspection of halite for primary chevron and hopper features and or milky appearance then petrography is used to distinguish between primary and secondary diagenetic crystal fabrics and inclusions the trace element and isotope geochemistry speak directly to the composition of the depositional and or diagenetic fluids and to the formation in marine non marine or diagenetic settings furthermore rare earth elements and redox sensitive elements may address the redox conditions of the salt pan flat brines whereas microthermometry helps characterize the depositional diagenetic environment s temperature finally gas extracted by quadrupole mass spectrometer from gas bubbles in fluid inclusions is screened with concomitant ch4 co2 and ar contents to distinguish and quantify organic matter decomposition contributions and with 40ar 36ar to monitor modern atmospheric gas diffusion leakage issues and thus contamination of the primary gas contents our test case shows that halite collected from cores is well suited in maintaining its original mineralogical texture chemistry and gas content our integrated screening protocol suggests that the 815 myr old halite from the tonian browne formation of the officer basin australia formed under atmospheric conditions of about 10 9 po2 back calculation or 9 6 po2 mean calculation the coeval neoproterozoic gypsum collected in outcrop from minto inlet victoria island canada underwent some mineralogical alteration however experiments suggest that depositional gypsum from outcrop core may have potential of retaining vestiges of original gas in fluid inclusions

palaeoecology of late cretaceous polar vegetation preserved in the hansen point volcanics nw ellesmere island canada abstract mesozoic polar forests represent an extinct biome subject to a polar light regime and elevated atmospheric co2 levels in this paper new cretaceous fossil plant assemblages are reported from nw ellesmere island canada at a paleolatitude of 75 n these occur in a campanian maastrichtian aged interval of the hansen point volcanics a unit interpreted as a coastal plain peat mire complex within an active volcanic setting studies of palynomorphs sterile and fertile foliage and wood indicate that mire environments were dominated by amber producing taxodiaceous conifers with other conifers ginkgos cycads angiosperms ferns lycopsids and bryophytes occurring in subordinate numbers leaf physiognomic studies imply that most vegetation was deciduous occurrence of traumatic rings in the woods together with a high year to year variability in ring width indicates disturbed growing conditions possibly linked to a combination of frosts volcanic eruptions and flooding abundant charcoal remains indicate that an additional important disturbance process was wildfire results of this study compare closely with those from coeval circum arctic fossil sites and augment our knowledge of the community scale ecology of the cretaceous polar biome

linkages between climate fire and vegetation in southwest china during the last 18 5ka based on a sedimentary record of black carbon and its isotopic composition abstract fires are sensitive to climate changes and in addition they have a major influence on the global carbon cycle land surface properties and chemical composition of the atmosphere which in turn can affect the climate system projecting the impacts of future climate changes on fire mediated biogeochemical processes requires understanding of how various climatic factors influence regional fire regimes however long term variations in fire activity and their controls are poorly known in this study we report the concentration of black carbon bc and its isotopic composition 13cbc in an upland lake sediment core from southwest china in order to elucidate linkages between changes in fire regime climate and vegetation over the past 18 5 ka the results show that the sedimentary bc content recorded variations in fire activity and exhibits a close negative correlation with the amount of precipitation delivered by the indian summer monsoon ism during heinrich event 1 18 5 15 0 cal ka bp the younger dryas 12 8 11 1 cal ka bp and the mid to late holocene the weakening of the ism led to greatly increased fire activity in southwest china in the last 1 0 ka the bc record may have been affected by human activity in the catchment which may have caused an increased influx of minerogenic material to the lake thereby diluting the sedimentary bc concentration the general trend of changing vegetation compositions inferred from the 13cbc values also tracks the variations of the ism suggesting a change from mixed c3 c4 plant ecosystems during the last glacial maximum to c3 plant dominated forest during the holocene however the abundance of c4 plants may be overestimated during the bolling allerod warm interval and the early holocene due to the fact that fires were probably limited to the savanna ecosystem in the valleys and low lying basins

first report of amber with spider webs and microbial inclusions from the earliest cretaceous c 140 ma of hastings sussex abstract early cretaceous amber resins with macroscopic inclusions are extremely rare as are ambers with inclusions from the parent plant here we report earliest cretaceous amber resins found within alluvial soils of the ashdown formation near hastings in sussex in contrast to younger cretaceous examples this hastings amber was arguably deposited shortly before the emergence of the earliest flowering plant communities c 140 ma bp preliminary studies reveal plentiful organic inclusions including vascular tissues tracheid cells and putative resin ducts of the parent coniferous trees we also report remarkably preserved soil microbes including structures comparable with actinobacterial colonies putative fungal or cyanobacterial filaments and the earliest examples of spider silk webs the last includes threads that are twisted paired and coated with sticky fluid droplets comparable with those of araneoid spider webs studied by us in modern cherry tree resins together these hastings amber inclusions became entombed within resins that seeped through the charred bark of coniferous trees subjected to severe fire damage whose logs were then swept onto fluvial wetlands by floods embalming resins of this kind may have evolved to combat damage associated with insects fungi and widespread forest fires

stable carbon isotopes of c3 plant resins and ambers record changes in atmospheric oxygen since the triassic estimating the partial pressure of atmospheric oxygen po2 in the geological past has been challenging because of the lack of reliable proxies here we develop a technique to estimate paleo po2 using the stable carbon isotope composition d 13 c of plant resins including amber copal and resinite from a wide range of localities and ages triassic to modern plant resins are particularly suitable as proxies because their highly cross linked terpenoid structures allow the preservation of pristine d 13 cs ignatures over geological timescales the distribution of d 13 c values of modern resins n 126 indicates that a resin producing plant families generally have a similar fractionation behavior during resin biosynthesis and b the fractionation observed in resins is similar to that of bulk plant matter resins exhibit a natural variability in d 13 c of around 8 d 13 cr ange 31 to 23 m ean 27 which is caused by local environmental and ecological factors e g water availability water composition light exposure temperature nutrient availability to minimize the effects of local conditions and to determine long term changes in the d 13 co f resins we used mean d 13 c values d 13 c resin for each geological resin deposit fossil resins n 412 are generally enriched in 13 c compared to their modern counterparts with shifts in d 13 c resin of up to 6 these isotopic shifts follow distinctive trends through time which are unrelated to post depositional processes including polymerization and diagenesis the most enriched fossil resin samples with a d 13 c resin between 22 and 21 formed during the triassic the mid cretaceous and the early eocene experimental evidence and theoretical considerations suggest that neither change in pco2 nor in the d 13 c of atmospheric co2 can account for the observed shifts in d 13 c resin the fractionation of 13 c in resin producing plants d 13 c instead is primarily influenced by atmospheric po2 with more fractionation occurring at higher po2 the enriched d 13 c resin values suggest that atmospheric po2 during most of the mesozoic and cenozoic was considerably lower po2 10 20 than today po2 21 in addition a correlation between the d 13 c resin and the marine d 18 o record implies that po2 pco2 and global temperatures were inversely linked which suggests that intervals of low po2 were generally accompanied by high pco2 and elevated global temperatures intervals with the lowest inferred po2 including the mid cretaceous and the early eocene were preceded by large scale volcanism during the emplacement of large igneous provinces lips this suggests that the influx of mantle derived volcanic co2 triggered an initial phase of warming which led to an increase in oxidative weathering thereby further increasing greenhouse forcing this process resulted in the rapid decline of atmospheric po2 during the mid cretaceous and the early eocene greenhouse periods after the cessation in lip volcanism and the decrease in oxidative weathering rates atmospheric po2 levels continuously increased over tens of millions of years whereas co2 levels and temperatures continuously declined these findings suggest that atmospheric po2 had a considerable impact on the evolution of the climate on earth and that the d 13 c of fossil resins can be used as a novel tool to assess the changes of atmospheric compositions since the emergence of resin producing plants in the paleozoic

the paleoenvironmental evolution of the cambrian longwangmiao formation stage 4 toyonian on the yangtze platform south china petrographic and geochemical constrains abstract during the cambrian period stage 4 biodiversity and biomass declined rapidly and globally in an event known as the botomian toyonian crisis to gain a better understanding of the paleoenvironment in south china during this stage we present and interpret complex multi parameter carbonate analyses petrography carbon and oxygen isotopic composition and major trace and rare earth elements from the toyonian longwangmiao formation in the bandenggou section the longwangmiao formation comprises primarily carbonate deposits with massive detrital mineral occurrences in its lower middle sequence principal component analysis of the minerals and oxides leads to the definition of two intervals i and ii interval i is composed mainly of dolostones interbedded with sandstones and contains exceedingly high amounts of terrestrial original minerals and oxides as well as high ree y th and sc concentrations interval ii which is composed primarily of limestones has trace amounts of terrestrial original minerals and oxides and low ree y th and sc concentrations the 13c and 18o values show a significant positive shift from interval i to interval ii after eliminating the effects of diagenesis contributions through the analyses of diagenesis sensitive indexes 18o values mgo cao mn sr and fe sr ratios and the correlations of 13c 18o 18o eu eu eu eu ce ce and eu eu feo the sr and na concentrations of calcites in interval i are extremely high exceeding even the corresponding ranges of marine aragonites while calcites from interval ii have low sr and na concentrations that are within the range of marine low mg calcite however both show strong positive correlations between ca sr ca na and sr na the different calcite elemental behaviors in intervals i and ii suggest different carbonate precursors associated with seawater temperature and climate furthermore the sr ca ratios are negatively correlated with 13c and 18o values and the 13c values also negatively correlated with sio2 content these features indicate a significant change in the depositional environment during the cambrian toyonian stage from an early restricted marine environment under a warm and arid climate with massive terrestrial influxes to a later relatively open marine environment under a cool and humid climate with negligible terrestrial influxes this shift likely resulted in the observed changes in biomass and biodiversity

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

ediacaran seawater temperature evidence from inclusions of sinian halite abstract seawater temperatures throughout earth s history have been suggested to illustrate a long term cooling trend from nearly 70 c at 3500 ma to around 20 c at 800 ma the terminal neoproterozoic prior to the cambrian explosion is a key interval in evolutionary history as complex multicellularity appeared with the advent of the ediacara fauna these organisms were likely the first that required higher levels of atmospheric and dissolved marine oxygen for their sustainability it is known that most modern macroinvertebrates are intolerant of temperatures in excess of 45 c perhaps more importantly these high seawater temperatures limit the potential of dissolved oxygen and therefore become an integral part of this evolutionary story previously our understanding of seawater temperature during the terminal neoproterozoic comes only from 18 o 16 o and 30 si 28 si ratios ascertained from a limited number of cherts isotopic ratio methods for assessing seawater temperatures are inherently indirect and have a wide range of oscillation however maximum homogenization temperatures th max of primary fluid inclusions in halite provide a direct means of assessing brine temperature and have been shown to correlate well with average maximum air temperatures the oldest halites date to the neoproterozoic lower paleozoic 700 500 ma and ediacaran representatives can be found in sichuan province china which do preserve primary fluid inclusions for analysis via cooling nucleation methods we utilized halite samples from the changning 2 well correlative to the dengying formation 551 542 ma to provide a direct assessment of terminal neoproterozoic seawater temperature our measurements indicate that seawater temperatures where these halites formed are highly similar to tropical phanerozoic seawater temperature estimates from compiled paleotemperature data the decline in seawater temperatures over the course of the proterozoic accompanied by the reduction of seawater salinity with the sequestration of salt in massive halite deposits in the neoproterozoic allowed the ocean system to accumulate more dissolved oxygen and potentially paved the way for the evolutionary innovation of complex multicellularity

coupled alteration of hydrothermal fluids and thermal sulfate reduction tsr in ancient dolomite reservoirs an example from sinian dengying formation in sichuan basin southern china abstract to better understand the fluid activities and their roles in the formation of petroleum reservoirs dolomite was thoroughly studied in the ancient sinian dengying formation in sichuan basin southern china the high homogenization temperatures above 190 c of fluid inclusions positive eu anomaly and o and sr isotopic values of coarse crystalline pore filling dolomite fd in dissolution pore spaces have suggested that the fds are of hydrothermal origin there are also other minerals pyrite organic compounds pyrobitumen and gas components h 2 s co 2 and ch 4 in pore spaces the sulfur isotope compositions of pyrite and h 2 s along with the carbon isotopes of co 2 have shown the involvement of thermochemical sulfate reduction tsr hydrothermal activities during burial diagenesis of the dengying formation provided high temperature environment necessary for tsr to proceed the presence of co 2 and h 2 s in both processes enhanced fluid acidities and consequently porosity and permeability of the dengying formation emplacement of petroleum and acidic fluids helped to maintain pre existing reservoir spaces during deep burial stage overall the coupled hydrothermal activities and tsr provided favorable environments to allow for maintaining high quality reservoirs

choosing the best ancient analogue for projected future temperatures a case using data from fluid inclusions of middle late eocene halites abstract after the paleocene eocene thermal maximum petm global temperature and co2 levels decreased concurrently in the middle late eocene using different approaches estimated co2 levels of the middle late eocene are very similar to the 1000 ppm co2 level projected for the next 100 years as a result of increasing greenhouse gas concentrations the average global temperature is projected to increase from 1 4 to 5 8 c by 2100 relative to 2001 levels thus the middle late eocene may be the best ancient analogue for a future with increased temperatures due to burning of fossil fuels in order to explore the sensitivity range of global annual temperature with respect to co2 concentration exact atmospheric co2 concentrations and air temperatures of ancient analogs must be known previous palynological studies provide only indirect estimates of temperature however the homogenization temperature of fluid inclusions in halites obtained by the cooling nucleation method can provide the exact temperature of saline lake water which is similar to overlying air temperature in shallow lakes in this paper we measured the range of homogenization temperatures from 5 8 to 43 3 c of fluid inclusions in middle late eocene halites of the yunying depression central china the maximum homogenization temperature of fluid inclusions thmax in these middle late eocene halites is 4 6 c higher than the modern extreme highest temperature 38 7 c recorded for this area

ti content in huguangyan maar lake sediment as a proxy for monsoon induced vegetation density in the holocene the provenance of element ti in huguangyan maar lake hgy sediment has been under debate since yancheva et al 2007a proposed its eolian source from the chinese loessplateau clp and applied it as a proxy for asian wintermonsoon we performed a comprehensive study on ti carryingminerals and ti uxes in lake sediments wall rocks andloess from the clp here we show that the chemicalcompositions and morphological features of magnetite the most important ti carrier in hgy surface sediments are identical to those in wall rocks around the lake butsubstantially different from those in clp loess samples ourcalculated modern eolian ti ux from the clp is negligiblecompared to the average total ti ux to hgy and ti uxfrom catchment erosion can provide enough ti indicating tiin hgy sediment are predominantly from wall rock erosion inverse correlation between total organic carbon toc vegetation density and ti ca ratio terrestrial input in theholocene suggests monsoon induced vegetation densitypredominates over runoff in controlling ti input to hgy s ratio represents toc directly mediated reductive diagenesisof iron oxides magnetite preservation rather than anoxic oxic condition at the bottom water induced by wintermonsoon our record shows a decreased vegetation density increased ti input and weakened reductive diagenesisthrough the holocene driven by a weakened summermonsoon

extending the database of permian palaeo wildfire on gondwana charcoal remains from the rio do rasto formation parana basin middle permian rio grande do sul state brazil abstract macroscopic charcoal has been recovered from a bonebed from the barro alto outcrop middle permian guadalupian rio do rasto formation in the southernmost part of the parana basin brazil during this time a global biotic crisis was taking place and changes in the palaeofloristic composition can be observed records of palaeowildfires from the guadalupian period are scarce on a global scale in the parana basin low plant diversity compared to the entirety of gondwana persists and just a few plant bearing localities have so far been described from the northern part of the basin in the studied locality macroscopic charcoal could be detected in an outcropping bonebed and the occurrence of palaeo wildfires was confirmed besides representing the first palaeobotanical data for the guadalupian of the southern part of the parana basin the charcoal remains analyzed here are also a significant record of the local environmental conditions during the increase in aridity observed during the guadalupian and lopingian in gondwana this contributes to the understanding of regional changes that took place during this interval

a 13 000 year record of environmental magnetic variations in the lake and peat deposits from the chandra valley lahaul implications to holocene monsoonal variability in the nw himalaya abstract an 13 000 year old record of in situ peat bog and lacustrine sediments from a post glacial lake in the chandra valley of the lahaul himalaya is studied to generate the record of environmental magnetic signatures in response to indian summer monsoon ism variability in the nw himalaya the chronology of studied chandra peat trench cpt profile is based on 9 ams 14c calibrated dates cal yr bp the piece wise linear regression analysis of age depth model indicates non linear sedimentation with higher rates from 4142 cal yr bp to the present and lower accumulation during 12 880 4142 cal yr bp the mineral magnetism showed three dominant assemblages of magnetic minerals with varying concentrations in peat lake sediment sequence i e 1 mixed ferri and antiferromagnetic minerals between 12 880 and 11 019 cal yr bp 2 dominant antiferromagnetic mineralogy from 11 019 to 3172 cal yr bp and 3 significantly increased concentrations of mixed ferri and antiferromagnetic minerals from 3172 cal yr bp to the present with characteristically increased ferrimagnetic concentrations after 2032 cal yr bp the characteristic increase in antiferromagnetic mineral concentration accompanied by decreased ferrimagnetic concentration from 10 398 to 5770 cal yr bp suggest possible oxidation of magnetite to hematite under warmer climate conditions and corresponds to increased ism intensity during early to mid holocene warm wet climate in the nw himalaya the distinctly increased concentration of antiferromagnetic minerals from 6732 to 5770 cal yr bp indicates mid holocene climate optimum hco in the lahaul himalaya the strengthening and weakening of ism recorded in environmental magnetic signatures during 1260 852 cal yr bp 690 1098 ad and between 852 and 239 cal yr bp 1098 1711 ad corresponds to medieval warm period mwp and little ice age lia events respectively

field and laboratory tests for recognition of ediacaran paleosols abstract not a single paleosol had been described from rocks of ediacaran age until 2011 but 354 ediacaran paleosols have been described by 20 different authors since then some of these newly recognized paleosols have proven controversial so this paper reviews 20 distinct tests to determine whether a particular ediacaran bed could be a paleosol or not one problem has been that ediacaran paleosols are not precisely like modern soils because they lack root traces a diagnostic feature of silurian and geologically younger paleosols the principal problem for recognition of some ediacaran paleosols is the occurrence in them of megafossils assumed to have been marine although most of these fossils remain problematic for both biological and ecological affinities not all the tests discussed here are diagnostic of paleosols some are ranked permissive or persuasive permissive conditions for paleosols include ripple marks hummocky bedding pyritic limestones acritarchs or thalloid fossils low strontium isotopic ratios high 26 mg ratios and red color persuasive tests include loessites tsunamites desert playa minerals low boron content high 10 b isotopic ratios high carbon sulfur ratios and very low total reactive iron ratios diagnostic tests include matrix supported lapilli or crystal tuff parent materials ice wedges and other cryoturbation sepic birefringence fabrics evaporitic sand crystals and negative geochemical strain and mass transfer and highly correlated 13 c and 18 o like other geological periods the ediacaran is known from a variety of marine and non marine paleoenvironments

a petrographic and geochemical study of carbonate and silica phases from the ediacaran doushantuo formation in the three gorges area of south china implications for diagenetic conditions abstract the carbonate of the ediacaran doushantuo formation contains various silica phases in the three gorges area of south china to better understand the diagenetic conditions under which these silica phases formed we carried out a petrographic and geochemical study of the silica phases and the coadjacent carbonate phases at the xiaofenghe section xfh in the three gorges area of south china five types of silica phases can be distinguished based on petrographic characteristics s1 and s2 are composed of microcrystalline quartz in chert nodules and disseminated in the host dolostone respectively s3 is composed of the megaquartz while s4 and s5 are microcrystalline quartz and fibrous silica respectively both replacing calcite cement six distinct types of carbonate can be recognized including the host matrix carbonate c1 sparry calcite nodules c2 calcite around chert nodules c3 dispersed calcite cement within chert nodules c4 fine micropeloidal calcite cements c5 and calcite veins c6 sedimentary structures suggest that formation of the s1 through s5 silica phases and c2 through c5 carbonate phases occurred during early burial diagenesis and therefore their formation recorded early diagenetic conditions assuming that ediacaran surface seawater temperature ranged from 28 to 39 c surface seawater 18o values can be calculated based on the oxygen isotopic composition of the host dolostone matrix c1 which range from 6 to 0 4 to 0 and 2 to 0 for the d2 d3 and d4 subunits of the doushantuo formation respectively based on the 18o values of chert nodules and beds mainly phase s1 diagenetic temperatures can be constrained to between 27 and 60 c under such low diagenetic temperatures the primary geochemical signatures of the host dolostone such as ree y patterns 13ccarb and 34spy values are likely to be preserved those silica phases without evidence of contamination of continental silicate detritus show characteristic ree y patterns with minor light ree depletions positive la eu and gd anomalies negative ce anomalies and slightly super chondritic y ho ratios implying that the source of silica may be derived from seawater negative ce anomalies in the silica phases in d2 through d4 subunits indicate that the bottom seawater or early diagenetic porewater was oxic at the time of silica precipitation

the major composition of a middle late eocene salt lake in the yunying depression of jianghan basin of middle china based on analyses of fluid inclusions in halite abstract during the cretaceous tertiary transition in eastern china abundant halites formed in non marine areas many continental salt deposits from inland salt lakes were formed in eastern china in faulted basins as a result of the northward movement and collision of the indo china plate with the eurasian plate including the bohai gulf basin however a marine transgression versus a non marine origin of these evaporites remains to be determined primary fluid inclusions trapped in halite deposits can directly record the composition of evaporated seawater or salt lake water such as those in the cretaceous halite in the khorat plateau laos and thailand area can resolve the origins of the evaporate deposits recent fluid inclusions data in the khorat plateau coincide with the predicted secular variation of seawater and are comparable to other fluid inclusions in cretaceous marine halite indicating these fluid inclusions are directly related to a marine transgression our analyses in this study shows that the average k mg2 and so 4 2 contents are 8 8 5 0 and 6 8 g l respectively in the primary fluid inclusions in halite of middle late eocene from the yunying depression of china these numbers are much less than those in the contemporary spanish primary fluid inclusions in halite precipitated from seawater 16 4 36 3 and 12 5 g l for k mg2 and so 4 2 respectively furthermore br contents of all fluid inclusion samples in halite from the yunying depression are lower than 2 ppm vs 55 58 ppm at the base of spanish contemporary marine halite and their 37cl values range from 0 11 to 2 94 vs 0 09 to 0 24 in sylvite of spanish deposit indicating that the compositions of the middle late eocene brines trapped in halite in the yunying depression of china are very different from those derived from the contemporary seawater and are considered to be resulted from evaporation of an inland saline lake water with little influence of seawater

extremely high temperatures and paleoclimate trends recorded in permian ephemeral lake halite although the late paleozoic deglaciation is arguably one of the best deep time analogs for current and predicted climate change quantitative paleotemperature data from this interval are generally lacking we reconstruct extreme paleoweather conditions and paleoclimate changes from permian nippewalla group probably uppermost leonardian kungurian north america ephemeral lake halite by using fluid inclusion homogenization temperatures to directly measure the water temperature when the halite precipitated in these depositional settings this is an excellent air temperature proxy extremely high temperatures to 73 c and large diurnal temperature ranges are evidenced in the lower nippewalla group suggesting conditions more extreme than anywhere on earth today in contrast the upper nippewalla group was cooler maximum temperature was 43 c and diurnal temperature ranges were smaller though even these conditions are similar to modern extremely hot environments comparison to prior studies suggests that these results may be indicative of regional patterns this study represents the first pre quaternary high resolution quantitative data set of extreme paleoweather and possible paleoclimate trends from fluid inclusions in halite and provides new insight into climate change during the late paleozoic deglaciation

oxygen and hydrogen isotope evidence for a temperate climate 3 42 billion years ago the widely held view that the archaean climate around 3 5 billion years ago was remarkably warm with ocean temperatures perhaps as high as 80 c has been questioned on the grounds that the established method of estimating ancient ocean temperature from the oxygen isotope ratios of sedimentary deposits is subject to significant uncertainty michael hren et al have adopted a different approach to estimating ocean temperature based on an analysis of both oxygen and hydrogen isotopes of 3 4 billion year old buck reef chert sediments from south africa the isotopes sampled are consistent with formation in waters no warmer than about 40 c suggesting that earth s early oceans may have been far cooler than previously thought the study of stable oxygen isotope ratios 18o of precambrian cherts suggests that ocean temperatures during the archaean era about 3 5 billion years ago were between 55 c and 85 c but uncertainty about the 18o of the primitive ocean has led to considerable debate regarding this conclusion here a combined analysis of oxygen and hydrogen istopes sampled from 3 42 billion year old buck reef chert rocks in south africa indicates that the ancient ocean was much cooler than previously thought stable oxygen isotope ratios 18o of precambrian cherts have been used to establish much of our understanding of the early climate history of earth1 2 3 and suggest that ocean temperatures during the archaean era 3 5 billion years ago were between 55 c and 85 c ref 2 but because of uncertainty in the 18o of the primitive ocean there is considerable debate regarding this conclusion examination of modern and ancient cherts indicates that another approach using a combined analysis of 18o and hydrogen isotopes d rather than 18o alone can provide a firmer constraint on formational temperatures without independent knowledge of the isotopic composition of ambient waters4 5 here we show that 18o and d sampled from 3 42 billion year old buck reef chert rocks in south africa are consistent with formation from waters at varied low temperatures the most 18o enriched buck reef chert rocks record the lowest diagenetic temperatures and were formed in equilibrium with waters below 40 c geochemical and sedimentary evidence suggests that the buck reef chert was formed in shallow to deep marine conditions so our results indicate that the palaeoarchaean ocean was isotopically depleted relative to the modern ocean and far cooler 40 c than previously thought2

the mean and annual cycle of upper layer temperature fields in relation to sverdrup dynamics within the gyres of the atlantic ocean using 28 years of expendable bathythermograph data 1967 1994 we describe the mean and annual cycle of the upper ocean temperature fields in the atlantic from 30 s to 50 n in the context of the basin scale wind driven gyres sverdrup stream function field which provide a framework for describing the oceanographic measurements we examine the circulation field implied by the temperature distributions which are used as a proxy for the field of mass similarities between the temperature and stream function fields increase with depth in the lower to subthermocline depths of the tropical and equatorial gyres the zonal currents form a closed circulation a southeastward boundary current is suggested near and below 150 m that provides closure for the tropical gyre and the equatorial gyre axis is southward of that suggested by the stream function field higher in the water column the north equatorial countercurrent necc may be a surface manifestation of the north equatorial undercurrent neuc where the latter can be interpreted as the southern limb of the tropical gyre because there are large vertical shears in the tropics the equatorial gyre is not clearly indicated in the vertically integrated temperature field but appears below about 200 m here the south equatorial undercurrent seuc can be interpreted as the eastward flowing northern limb of the equatorial gyre and is opposite in direction to the westward flowing south equatorial current above both the neuc and seuc are analagous to currents in the pacific that are governed by non sverdrup dynamics despite the shortcomings of the data the mean annual cycle appears to be relatively stable and we have discounted the possibility that in regions where it represents a significant percentage of the total variance it is changing slowly over the 28 years of record the wind forcing fields which undergo large meridional movements 5 6 of latitude during their annual cycle with some exceptions have essentially no counterpart in gyre movements between their seasonal extremes most of the variability associated with the annual cycle is confined to the upper 300 m greatest variability where ranges exceed 6 c occurs in the northwestern atlantic in late winter and early spring during this time of year south of the gulf stream and below about 100 m water temperatures exhibit a systematic phase lag with depth the next largest area of variability where ranges can also exceed 6 c resides in the tropical western basin between the equator and 10 n just below 100 m in the eastern basin ranges decrease and shoal additionally the phase fields are consistent with the intensification and relaxation of the tropical ridge trough system where the necc disappears in march in the west but the necc neuc complex is strongest in september

chemical relationships of ambers using attenuated total reflectance fourier transform infrared spectroscopy amber is known for its remarkably well preserved fossils but the chemical complexity of amber and its history are less well known amber is highly variable in both its physical and chemical properties which are dependent on factors such as the source tree and the diagenetic history amber from a given locality therefore has a unique chemical composition fourier transform infrared ftir spectroscopy is often used to determine the chemical composition of amber and to provide a fingerprint for amber samples we used ftir spectroscopy to analyse samples spanning the time period from the early cretaceous to the oligo miocene from 17 localities in the americas europe and asia we then used cluster analysis to examine the trends in amber chemistry and to increase our understanding of its formation through time a detailed analysis of the clustering followed by modelling of the variables of importance suggested that the exocyclic methylene group content and conformation play a major part in explaining the clustering other variables such as the ester and alkyl contents contribute to identification placed in a broader perspective our study indicates that the dominant factor in clustering is the age of the amber followed by the locality

permian paleoclimate data from fluid inclusions in halite abstract this study has yielded surface water paleotemperatures from primary fluid inclusions in mid permian nippewalla group halite from western kansas a cooling nucleation method is used to generate vapor bubbles in originally all liquid primary inclusions then surface water paleotemperatures are obtained by measuring temperatures of homogenization to liquid homogenization temperatures ranged from 21 c to 50 c and are consistent along individual fluid inclusion assemblages indicating that the fluid inclusions have not been altered by thermal reequilibration homogenization temperatures show a range of up to 26 c from base to top of individual cloudy chevron growth bands petrographic and fluid inclusion evidence indicate that no significant pressure correction is needed for the homogenization temperature data we interpret these homogenization temperatures to represent shallow surface water paleotemperatures the range in temperatures from base to top of single chevron bands may reflect daily temperatures variations these permian surface water temperatures fall within the same range as some modern evaporative surface waters suggesting that this permian environment may have been relatively similar to its modern counterparts shallow surface water temperatures in evaporative settings correspond closely to local air temperatures therefore the permian surface water temperatures determined in this study may be considered proxies for local permian air temperatures

a holocene pollen record from the northwestern himalayan lake tso moriri implications for palaeoclimatic and archaeological research this paper presents a new fossil pollen record from tso moriri 32 54 n 78 19 e 4512 m a s l and seeks to reconstruct changes in mean annual precipitation map during the last 12 000 years this high alpine lake occupies an area of 140 km2 in a glacial tectonic valley in the northwestern himalaya the region has a cold climate with a map 300 mm and open vegetation the hydrology is controlled by the indian summer monsoon ism but winter westerly associated precipitation also affects the regional water balance results indicate that precipitation levels varied significantly during the holocene after a rapid increase in map a phase of maximum humidity was reached between ca 11 and 9 6 cal ka bp followed by a gradual decline in map this trend parallels the reduction in the northern hemisphere summer insolation comparison of different palaeoclimate proxy records reveal evidence for a stronger holocene decrease in precipitation in the northern versus the southern parts of the ism domain the long term trend of ism weakening is overlaid with several short periods of greater dryness which are broadly synchronous with the north atlantic cold spells suggesting reduced amounts of westerly associated winter precipitation compared to the mid and late holocene it appears that westerlies had a greater influence on the western parts of the ism domain during the early holocene during this period the westerly associated summer precipitation belt was positioned at mediterranean latitudes and amplified the ism derived precipitation the tso moriri pollen record and moisture reconstructions also suggest that changes in climatic conditions affected the ancient harappan civilisation which flourished in the greater indus valley from approximately 5 2 to 3 cal ka bp the prolonged holocene trend towards aridity punctuated by an interval of increased dryness between ca 4 5 and 4 3 cal ka bp may have pushed the mature harappan urban settlements between ca 4 5 and 3 9 cal ka bp to develop more efficient agricultural practices to deal with the increasingly acute water shortages the amplified aridity associated with north atlantic cooling between ca 4 and 3 6 and around 3 2 cal ka bp further hindered local agriculture possibly causing the deurbanisation that occurred from ca 3 9 cal ka bp and eventual collapse of the harappan civilisation between ca 3 5 and 3 cal ka bp

quantitative temperature records of mid cretaceous hothouse evidence from halite fluid inclusions abstract quantitative temperature reconstructions for the mid cretaceous are still rare although its typical greenhouse climate is regarded as one of the best analogues for future global warming for the first time mid cretaceous temperatures were quantitatively reconstructed based on homogenization temperatures th of halite fluid inclusions from the lower member of the nong bok formation in the thakhek mining area laos petrological features and primary textures of halite indicate a shallow water setting during halite formation that allows the use of homogenization temperatures as air temperature proxy obtained homogenization temperatures mainly range from 30 to 50 c probably representing local air temperature conditions of laos during the mid cretaceous the determined temperatures are relatively similar to temperatures in many modern and ancient evaporative settings the maximum homogenization temperature th max for the nong bok formation of 62 1 c is significantly higher than existing mid cretaceous paleotemperature records from both continental and marine sediments and comparable with the temperature records from the contemporaneous mengyejing formation of yunnan southern china the correspondence of the temperature records from laos and yunnan implies that very high temperature conditions prevailed in the region our results and other reconstructed very high temperatures from potash deposits e g 59 c for the silurian michigan basin and 58 c for the quaternary lop nur region suggest that extremely high temperatures probably had an important impact on the formation of the large potash deposits of the world however more studies are needed to improve our understanding of the detailed and quantitative relationships between temperature conditions and potash formation

paleobrine temperatures chemistries and paleoenvironments of silurian salina formation f 1 salt michigan basin u s a from petrography and fluid inclusions in halite abstract a 3 7 m stratigraphic section of the silurian salina group f 1 salt detroit salt company mine michigan basin was studied to document the paleodepositional conditions including brine chemistry and temperature of evaporite precipitation sedimentary features including rippled surfaces halite chevrons cumulate halite and dissolution surfaces confirm a shallow water depositional setting penecontemporaneous dissolution surfaces indicate that waters undersaturated with respect to halite were introduced into the michigan basin and that the basin brines were nonstratified during flooding allowing inflow waters to come into contact with halite crystals at the bottom fluid inclusions in primary chevron halite have homogenization temperatures between 5 and 25 c which represent brine temperatures during halite precipitation these temperatures are lower than expected for a marginal marine basin at a subtropical paleolatitude and they suggest a climatic cold spell for a period of thousands of years the major ions in fluid inclusion brines analyzed using the esem x ray eds method have relatively low concentrations of na mg2 and so42 and elevated concentrations of ca2 compared to modern seawater brine inclusion chemistries from the f 1 salt compare closely with the major ion composition of fluid inclusions from other silurian marine halites a 1 a 2 and b evaporites of the salina group and carribuddy group canning basin australia these results indicate a seawater parentage of the michigan basin f 1 salts and that the major ion chemistry of seawater remained more or less constant during the last 15 million years of the silurian detailed documentation of the temperatures brine chemistries and environments of halite deposition is a prerequisite for geobiological study of the entrapment of ancient microbes in salt the results reported here can help pinpoint the timing of entrapment of microorganisms in fluid inclusions in halite and can be used to argue that brine inclusions in the f 1 halites have been isolated and preserved in an unmodified state for more than 400 million years

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

holocene monsoon climate documented by oxygen and carbon isotopes from lake sediments and peat bogs in china a review and synthesis there has been much recent debate about holocene climate variation in the monsoon region of china especially the temporal pattern of variations in precipitation the time transgressive nature of the holocene precipitation maximum and the extent to which variations in regions influenced by the indian summer monsoon ism and the east asian summer monsoon easm have been synchronous we summarize and compare carbonate oxygen isotope records delta o 18 carb from ten lakes within the present day ism region we discuss their paleoclimate significance considering the present day moisture source isotopic composition of precipitation and the hydrological setting the delta o 18 carb records are controlled mainly by the isotopic composition of lake water which in turn is a function of regional precipitation evaporation p e balance and the proportion of precipitation that is monsoon derived we normalized the delta o 18 carb data and used these records to generate an integrated moisture index this index along with oxygen isotope records from speleothems and carbon isotope records delta c 13 org from peats within the monsoon region suggests that holocene climate was broadly synchronous across the monsoon region and within the limits of accuracy of the existing age models provides no strong evidence for previously proposed anti phasing of the ism and the easm stable isotope records from lake sediments and peat bogs have excellent potential for providing high quality paleoclimate data for monsoon asia and complement high resolution speleothem sequences which are only found in certain localities c 2011 elsevier ltd all rights reserved

the plant debris beds of the early cretaceous barremian wessex formation of the isle of wight southern england their genesis and palaeontological significance abstract the early cretaceous barremian wessex formation of the isle of wight primarily represents high sinuosity fluvial but also lacustrine and terrestrial deposition on a low relief floodplain occupying half grabens with active normal faults immediately to the north plant debris beds form a very small proportion of the succession but are the main source of vertebrate fossils including dinosaurs these conspicuous but thin grey units are distributed randomly throughout the wessex formation and are of limited lateral extent the lower part of most plant debris beds comprises a poorly sorted matrix supported conglomerate the upper part of most consists of structureless mudstone which usually grades up into colour mottled but predominantly red and purple floodplain mudstones the plant debris beds contain an unusual mixture of freshwater molluscs diverse aquatic and terrestrial vertebrates and mainly terrestrial plants with a variable quality of preservation we conclude that each plant debris bed represents a locally generated sheetflood which was then transformed on the floodplain into a debris flow by the acquisition of surface material the debris flows surged into and were deposited in depressions on the alluvial plain including abandoned chute and cut off channels oxbows and ponds these units are therefore intrabasinal and interfluvial and the fossils that they contain are locally derived similar deposits of palaeontological significance have not been reported elsewhere in the literature in view of this their origin and sedimentology their palaeontological significance and the taphonomy of the flora and fauna they contain are discussed

first early mesozoic amber in the western hemisphere detrital amber pebbles and granules have been discovered in upper triassic strata on the colorado plateau although amber pre viously has been reported from pennsylvanian jurassic cretaceous and tertiary strata we know of no other reported triassic occurrence in north america or the western hemisphere the newly discovered occurrences of amber are at two localities in the lower part of the petrified forest member of the upper triassic chinle formation in petrified forest national park arizona the paper coals and carbonaceous paper shales containing the amber also contain fossil palynomorph assemblages that indicate a late carnian age for these occurrences

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

holocene variations in the asian monsoon inferred from the geochemistry of lake sediments in central tibet we present a record of monsoon variations for the early and middle holocene that is inferred from the geochemistry of sediment cores from ahung co a lake in central tibet the resolution of this record is better than 50 yr and the age model is derived from radiocarbon ages of terrestrial charcoal which eliminates errors associated with the lake hard water effect we made down core geochemical measurements of carbonate organic carbon c n and 13c of bulk organic matter 13c and 18o of carbonate and dolomite proxy calibration and modern water balance reconstruction show that these are proxies for lake depth and the amount of monsoon precipitation we find that lake level and monsoon precipitation have been decreasing at ahung co since the early holocene 7500 cal yr b p superimposed on this trend are rapid declines in monsoon rainfall at 7000 7500 and 4700 cal yr b p and seven century scale wet dry oscillations the cores do not contain sediment from the last 4000 yr surface sediments from the lake accumulated during the 20th century however from this we argue that lake levels have risen again recently following a late holocene dry period

petrological and geochemical characteristics of the botryoidal dolomite of dengying formation in the yangtze craton south china constraints on terminal ediacaran dolomite seas abstract recent studies suggest that the massive precambrian dolomite successions were likely the products of specific seawater conditions known as dolomite seas however whether these so called dolomite seas existed in the terminal ediacaran ocean has not yet been constrained the widespread botryoidal dolomite with well preserved sedimentary fabrics from the upper ediacaran dengying formation ca 551 to 545 ma south china can be potentially an ideal target to constrain this issue results showed that within the botryoidal dolomite fibrous dolomite cements are the dominant constituent part and either grew upward from microbialite layers or occurred in sheet cracks within the microbialites implying a syn sedimentary diagenesis two different types of fibrous cements are newly redefined fascicular and radial slow dolomite well preserved chemical and cathodoluminescent zonations and length slow optical characters are direct evidence for syn sedimentary primary dolomite precipitation different with the previous alternative interpretations of mimetic dolomitization of aragonite or high mg calcite precursors in contrast microbialite matrix consists of finely crystalline dolomicrite and preserved microbial fabrics reveling an early mimetic dolomitization of aragonitic precursors the dolomite precipitation and mimetic dolomitization likely occurred in coeval seawater or seawater type fluids as indicated by comparable 13c and 87sr 86sr data with global changes in particular the presence of primary dolomite cement precipitates within botryoidal dolomite can reflect that the specific dolomite seas associated with anoxic or even euxinic shallow water conditions inferred by redox sensitive trace elements and rees and increased microbial activity also prevailed in the terminal ediacaran ocean however the occurrence of dolomite seas was not one occasional event but common even if not persistent in the early to terminal neoproterozoic oceans this study helps to improve the understanding of dolomite problem and ubiquitous distribution of precambrian dolomite worldwide

holocene vegetation history precipitation changes and indian summer monsoon evolution documented from sediments of xingyun lake south west china we present a pollen based precipitation reconstruction and multi proxy records from a 485 cm long sequence from a sediment core from xingyun lake yunnan plateau south west china which depicts the evolution of the indian summer monsoon ism during the last 8500 years pollen and other palaeoenvironmental records document several stages of vegetation history and climate change the warmest and wettest climate in the xingyun lake catchment occurred before 5500 cal a bp and subsequently the climate became gradually drier after 2000 cal a bp the regional environmental conditions became unstable and a wet medieval warm period is probably recorded our reconstruction of the ism is similar to that portrayed by holocene speleothem o 18 records from southern china but is distinctly different from the east asian summer monsoon easm evolution which features a mid holocene maximum our results support the hypothesis that the ism and easm evolved asynchronously during the holocene and imply that the chinese speleothem o 18 records from southern china may principally reflect changes in moisture source from the indian monsoon domain and thus record the history of the ism rather than the easm

revised wonoka isotopic anomaly in south australia and late ediacaran mass extinction the global late ediacaran shuram wonoka carbon isotope anomaly has been regarded as the largest and longest known isotopic anomaly in the ocean assuming that all ediacaran carbonate is marine disregarding carbonate in south australia shown here to be palaeosol or palaeokarst the synchronous marine organic carbonate excursion is only 8 for 13 c organic and 6 for 13 c carbonate and lasted less than a million years this revised magnitude and duration is comparable with perturbations across the permian triassic boundary and correlative with a global late ediacaran acritarch mass extinction like permian triassic isotopic excursions the revised organic carbonate wonoka excursion may also have been a greenhouse palaeoclimatic warm spike which terminated valley incision and glacioeustatic drawdown during the mid ediacaran fauquier glaciation and preceded chill of the late ediacaran billy springs glaciation supplementary material measured sections and tables of mineral and grain size proportions major element and stable isotope analyses are available at www geolsoc org uk sup18756

the enigma of neoproterozoic giant ooids fingerprints of extreme climate geologists have documented at least fourteen occurrences of giant ooids a geologically rare type of carbonate allochem in neoproterozoic successions at low paleo latitudes recent experiments a

diatom response to asian monsoon variability during the late glacial to holocene in a small treeline lake sw china analyses of diatoms grain size magnetic susceptibility total organic carbon and total nitrogen were applied to a 9 26 m long sediment core spanning the last 12 2 kyr from a small treeline lake tiancai lake 3898 m a s l in southwest china diatom assemblages are dominated by cyclotella distinguenda aulacoseira species and small fragilarioid taxa all of which are sensitive to changes in water ph and light conditions that are probably related to vegetation development and runoff processes triggered by variations in the asian monsoon high abundances of c distinguenda and pseudostaurosira brevistriata reflected cold and dry climates during the late glacial 12 2 11 4 kyr bp in the early holocene 11 4 9 4 kyr bp a steep decline in c distinguenda and a visible increase in aulacoseira alpigena responded to a strengthening monsoon intensity the persistent increases in a alpigena mirrored strong monsoon intensity in the middle holocene 9 4 4 6 kyr bp after 4 6 kyr bp the reduction of a

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

holocene treeline shifts and monsoon variability in the hengduan mountains southeastern tibetan plateau implications from palynological investigations abstract the upper 8 45 m of a sediment core from lake naleng were analysed for its pollen and charcoal content to detect vegetation climate and human activity changes on the southeastern tibetan plateau tp since the pleistocene holocene transition 11 7 cal kyr bp the application of pollen indicator taxa pollen sums biomisation and multivariate analysis helped to reconstruct environmental conditions during the holocene furthermore 64 surface samples from the southeastern tp and its foreland were analysed to investigate the relationship between modern pollen assemblages and vegetation the modern vegetation was recorded in the surface pollen assemblages by pollen indicator types although sediments also contain pollen spectra extra regional pollen transported from lower vegetation belts which is seen as a consequence of steep elevation gradients at the southeastern margin of the tp the relation between different vegetation belts and temperature from the modern sample sites was used to infer quantitative temperature trends for the holocene record spreading of forests at the beginning of the holocene marks the transition to warmer conditions from 10 7 to 4 4 cal kyr bp open abies betula forests were found at lake naleng probably reflecting a stronger than present summer monsoon temperature range reconstructions suggest a temperature that was about 2 3 c warmer and a treeline position that was 400 600 m higher than today a severe climate deterioration with temperatures about 1 2 c colder than before is documented by a retreating forest between 8 1 and 7 2 cal kyr bp forests retreated while subalpine rhododendron shrubs spread around lake naleng indicating colder conditions with temperatures 1 2 c below early and mid holocene level after 4 4 cal kyr bp the forest decline at 4 4 cal kyr bp is considered to reflect climatic conditions as low concentrations of charcoal particles found in this period exclude human induced fires as reason for the forest retreat however grazing indicators imply human influence on the environment since 3 4 cal kyr bp around lake naleng we therefore consider the rapid treeline shift seen at 3 4 cal kyr bp as partly generated by human activity and partly by climatic conditions

inverse phase oscillations between the east asian and indian ocean summer monsoons during the last 12 000 years and paleo el nino abstract the inverse phase variations between the east asian and indian ocean summer monsoons on the interannual timescale result from the el nino southern oscillation activity in the tropical pacific which potentially provides a new way for studying paleo enso here we reconstruct a 12 000 yr proxy record for the east asian summer monsoon from 13 c time series of the plant cellulose of the hani peat bog in the northeastern china the comparison of it with the peat proxy record of the indian ocean summer monsoon suggests that the el nino conditions are coincident with strong east asian summer monsoons weak indian summer monsoons and drift ice events in the north atlantic at both orbital and millennial time scales the orbital scale inverse phase relationships between the monsoons indicate the occurrence of a long term enso like pattern confirming the sensitivity of the monsoon systems associated with enso to insolation forcing the nine inverse phase variations on the millennial time scales may suggest the nine el nino like patterns superimposing the long term enso like pattern the inverse phase variations between the monsoons also show close correspondence to the drift ice events at high northern latitudes in every case when the abrupt ice rafted debris events occurred in the north atlantic the inverse phase relationship established and the el nino like pattern occurred in the tropical pacific correspondingly the discussions on the influence of ocean thermohaline circulation on these global linkages have been made

paleotemperatures preserved in fluid inclusions in halite a variety of paleoclimate proxy records allow determination of relative warming or cooling however if we are to understand climate change quantification of past temperature fluctuations is essential our research indicates that fluid inclusions in halite can yield homogenization temperatures that record surface brine temperatures at the time of halite precipitation to avoid problems with stretching leaking and initial trapping of air samples with primary single phase liquid fluid inclusions are chilled in a freezer to nucleate vapor bubbles we tested the reliability of this method of obtaining fluid inclusion homogenization temperatures using modern salts precipitated at badwater basin death valley california homogenization temperatures correlate well with measured brine temperatures the same method is applied to fluid inclusions in pleistocene halite from a core taken at the same location in death valley results are at several scales recording diurnal temperature variations seasonal temperature fluctuations and longer term warming and cooling events that correlate with major changes in the sedimentary environment related to climate this technique is uniquely instrumental for paleoclimate studies because it offers actual not just proxy paleotemperature data 27 refs 17 figs

hydrological and ecosystem response to abrupt changes in the indian monsoon during the last glacial as recorded by sediments from xingyun lake yunnan china abstract the indian summer monsoon ism is the major moisture source of precipitation in southwest china and plays an important role in regional environmental change and in economic and social development since abrupt changes of the ism can cause crop failures and flooding that impact the livelihood of a large population however with the exception of speleothem records abrupt changes of the ism during the last glacial are not well documented in terrestrial records here we present a sediment record from xingyun lake in yunnan province southwest china spanning the interval 36 4 ka bp to 13 4 ka bp 1 ka 1000 cal a which documents the occurrence of a series of millennial scale episodes which may reflect the abrupt weakening of the ism seven ams 14c dates from terrestrial wood fragments provide a robust chronology the results demonstrate that increases in the coarse sediment fraction 30 m correspond to increases in the concentration of pediastrum the grain size of magnetic minerals carbonate content and c n ratios which together indicate episodes of low lake level in addition pollen analysis indicates that quercus oak increased and that ferns decreased during intervals of abrupt weakening of the ism indicating a drier environment nine abrupt shifts to a low lake level are documented for the studied interval and three of them are correlative with heinrich events 1 to 3 our study supports the hypothesis that in response to the cold events in the north atlantic associated with massive iceberg influxes and the corresponding slowing down of atlantic meridional overturning circulation the mean latitudinal extent of the itcz shifted southwards as a result of an atmospheric teleconnection there was a corresponding decrease in precipitation associated with ism precipitation which caused reduced fluvial runoff in yunnan

paleotemperatures from fluid inclusions in halite method verification and a 100 000 year paleotemperature record death valley ca abstract maximum homogenization temperatures of fluid inclusions thmax in halite laboratory grown crystals and modern samples death valley ca match maximum brine temperatures during halite precipitation maximum brine temperatures during halite precipitation in death valley late april 1993 34 4 c agree with thmax 34 c and correlate well with average maximum air temperatures in april 31 3 c and may 37 6 c thmax may be used for paleoclimate interpretations based on the close relationship between saline lake temperatures and average air temperatures from modern settings lower homogenization temperatures demonstrably below the temperatures at which halite grew are interpreted to reflect collapse of some fluid inclusion walls due to the pressure difference between the inside and outside of inclusions by only using thmax the problems of anomalously low homogenization temperatures due to possible collapse of fluid inclusions are avoided halite samples from 30 stratigraphic intervals 90 to 0 m 100 to 0 ka core dv93 1 death valley ca were used to measure homogenization temperatures of fluid inclusions virtually all homogenization temperatures from core dv93 1 are below the modern thmax of 34 c halite precipitation late april 1993 lacustrine halites deposited in a perennial saline lake 35 to 10 ka have thmax between 19 c and 30 c which suggests brine temperatures approximately 4 c to 15 c below modern late april values ephemeral saline lake halites precipitated 60 to 35 ka have thmax between 23 c and 28 c 6 to 11 c below modern values the highest thmax value in the 100 ka record up to 35 c is from a halite sample formed approximately 100 ka in a climate regime somewhat colder than the modern

holocene indian summer monsoon variation inferred from geochemical and grain size records from lake ximenglongtan southwestern china abstract identifying holocene indian summer monsoon ism variability and its possible mechanism is critical for predicting future environmental changes in this study we present a well dated ca 9 4 kyr geochemical and grain size record derived from lake ximenglongtan southwestern china the record depicts the holocene ism evolution and multi decadal to centennial abrupt precipitation change events superimposed on the long term climate changes the results indicate that precipitation was high during the first half of the holocene from ca 9 4 to 4 5 cal kyr b p but decreased over the later holocene on the multi decadal to centennial time scale our results show that a pronounced and prolonged drought event occurred between 7 6 and 7 0 cal kyr b p in addition several other low precipitation events occurred at about 8 9 6 3 5 2 4 2 3 7 2 5 and 1 7 cal kyr b p which correspond well with reported intervals of abrupt ism weakening events our findings suggest that changes in solar activity may have primarily controlled the fluctuations of ism intensity on the multi decadal to centennial time scale cooling of the north atlantic climate and the interactions between tropical ocean and atmosphere may have amplified the solar signal

latest pleistocene and holocene vegetation and climate history inferred from an alpine lacustrine record northwestern yunnan province southwestern china abstract reconstructing past changes of the summer monsoon in southwestern china is key to understanding the paleoclimatic dynamics of the indian summer monsoon southwest monsoon a major tropical system with impacts beyond the region high resolution pollen and conifer stoma data are presented from a sediment core tiancai lake located just below treeline in the hengduan mountains northwestern yunnan province of china these data record changes in vegetation and climate for the latest pleistocene and holocene c the last 12 230 cal yr bp and by comparing these results with the pollen records from the nearby erhai lake and lugu lake a regional climate history in yunnan province can be inferred during the period of 12 230 11 510 cal yr bp open alpine meadow around tiancai lake indicates a relatively cold and dry climate corresponding to the younger dryas cold event yd between 11 510 and 10 000 cal yr bp the vegetation types around tiancai lake changed into picea and abies forest and alpine rhododendron shrubland reflecting increases in the temperature and humidity from 10 000 to 6100 cal yr bp tsuga forest expanded persistently toward tiancai lake indicating further climate changed towards warmer and wetter conditions between 6100 and 3410 cal yr bp tsuga forest was the dominant vegetation type nearest to tiancai lake denoting warm and humid climatic conditions corresponding to the holocene climatic optimum in the northwestern yunnan province tsuga forest in mountains around lugu lake shrank quickly at 3410 cal yr bp reflecting significant decline of humidity since 2930 cal yr bp tsuga forest around tiancai lake shrank gradually indicating a fluctuating decrease of temperature these climatic changes reflect changes of the southwest monsoon namely warm and humid climate indicating strong southwest monsoon cold and dry climate denoting weak southwest monsoon