middle late permian mass extinction on land the end permian mass extinction has been envisaged as the nadir of biodiversity decline due to increasing volcanic gas emissions over some 9 million years we propose a different tempo and mechanism of extinction because we recognize two separate but geologically abrupt mass extinctions on land one terminating the middle permian guadalupian at 260 4 ma and a later one ending the permian period at 251 ma our evidence comes from new paleobotanical paleopedological and carbon isotopic studies of portal mountain antarctica and comparable studies in the karoo basin south africa extinctions have long been apparent among marine invertebrates at both the end of the guadalupian and end of the permian which were also times of warm wet greenhouse climatic transients marked soil erosion transition from high to low sinuosity and braided streams soil stagnation in wetlands and profound negative carbon isotope anomalies both mass extinctions may have resulted from catastrophic methane outbursts to the atmosphere from coal intruded by feeder dikes to flood basalts such as the end guadalupian emeishan basalt and end permian siberian traps

techniques for determining opal in deep sea sediments a comparison of radiolarian counts and x ray diffraction data abstract detailed records of two estimators of the biogenic silica content of deep sea sediments x ray diffraction analysis opal concentrations and quantitative radiolarians per gram counts from microscope slides were compared in downcore sediments from northwest pacific core rc14 105 to evaluate and to intercalibrate the two techniques both the degree to which the data were similar and the degree to which inferences from the data were similar were considered although both data sets are internally consistent and reflect surface water processes they are not equivalent and there is no way to convert one linearly into the other the numbers of radiolarians per gram of sediment appear to respond to the same factors which control the fluctuations in the radiolarian assemblage distrbutions in the area the opal contents respond to the factors which control the total siliceous productivity of the area

palaeoenvironmental change during the end guadalupian permian mass extinction in sichuan china abstract the end guadalupian mass extinction has been investigated in sichuan province sw china in the south of the province the platform carbonates of the maokou formation are overlain by the emeishan flood basalts a possible factor in the extinction event and in the north of the province the formation is succeeded by shallow marine carbonates of the wuchiaping formation late permian the extinction event is primarily recorded by the loss of fusulinaceans and possibly by species level turnover amongst calcareous algae the high diversity middle permian microfossil assemblages are last seen beneath a surface recording widespread emergence and karstification in northern sichuan emergence occurred early in the capitanian stage and the succeeding strata record restricted hypersaline deposition that preceded the deposition of a thick ash horizon the wangpo bed these mid capitanian arid conditions are replaced by humid conditions towards the end of the stage as indicated by the development of a widespread coal seam in southern sichuan only a thin development of this humid coaly facies is seen developed atop the maokou karstic surface and below the oldest flood basalt the guadalupian interval saw the development of large c isotope excursions in the carbonate record these include a positive then negative swing late in the capitanian and a newly discovered negative spike superimposed on an early capitanian heavy interval this spike may be a global phenomenon but the magnitude 8 may have been exaggerated by an increased contribution from light respired c derived from soils during relative sea level fall a plethora of environmental factors approximately coincide with the extinction event including regression acidic volcanism and flood basalt volcanism making it difficult to unravel the relative significance of each

redox conditions across the g l boundary in south china evidence from pyrite morphology and sulfur isotopic compositions abstract the end guadalupian middle permian mass extinction recorded the disappearance of shelf faunas such as fusulinids small foraminifers brachiopods rugose corals which flourished in the warm shallow marine habitats after the late pennsylvanian early permian glaciation the causes for this mass extinction are still unclear marine anoxia often as a cause for other mass extinctions has been paid less attention in this extinction here we present a comprehensive study including pyrite morphology and sulfur isotopic compositions of pyrite across the guadalupian lopingian middle upper permian g l boundary at tianfengping in northern yangtze platform and at penglaitan in southern yangtze platform in south china our results show that the sulfur isotope ratios of pyrite mainly track the framboid size distributions in these two sections anoxia and intermittent euxinia occur at the g l boundary evidenced by the coincidence between reduction of framboid size and the extremely negative sulfur isotope values of pyrite involving disproportionation and corresponds to the main mass extinction of the end guadalupian suggesting a causal link between them long term dysoxic conditions during the middle capitanian are evidenced by the relative small framboid size and lower sulfur isotope ratios of pyrite and coincide with the first pulse of the end guadalupian mass extinction also suggesting a causal link between them the oxygen depletion conditions in the capitanian during the global sea level falling may be the main cause for the end guadalupian mass extinction

new timing and geochemical constraints on the capitanian middle permian extinction and environmental changes in deep water settings evidence from the lower yangtze region of south china the capitanian guadalupian witnessed one of the major crises of the phanerozoic and like many other extinctions it coincided with the eruption of a large igneous province in this case the emeishan traps of sw china however the timing and causal relationships of this event are in dispute this study concentrates on the deep water chert mudstone strata of the gufeng formation and its transition to the yinping formation at chaohu zircons from tuffs in the uppermost gufeng formation yield a u pb age of 261 6 1 6 ma and comparison with sections around emeishan suggests that the tuffs appeared in the jinogondolella altudaensis conodont zone and persisted to the jinogondolella xuanhanensis zone this coincides with the emeishan eruptions and suggests that the tuffs probably derived from this province mineralogical and geochemical characteristics also show the tuffs are of acid volcanogenic origin and have a geochemical fingerprint of the emeishan large igneous province our dating shows that a crisis amongst radiolarian and a subsequent productivity decline occurred during the middle capitanian prior to the guadalupian lopingian boundary the emeishan eruptions began immediately before this indicating a likely causal relationship between these events major regression and marine anoxia euxinia are two other important extinction relevant environmental changes that occurred during this critical interval

cycles steps and co2 paleoceanography in the united states from 1983 1986 the field of paleoceanography experienced continued growth during the last three years the first international conference on paleoceanography was held in zurich switzerland in july 1983 and a new journal devoted to the topic paleoceanography american geophysical union washington d c began publication in spring 1986 edited by dr james kennett of the university of rhode island nine legs of the r v glomar challenger concentrated upon paleoceanographic topics legs 71 75 in the south atlantic leg 81 in the north atlantic leg 85 in the equatorial pacific leg 86 in the northwest pacific and leg 90 in the southwest pacific several special symposia and conferences resulted in volumes of collected papers dealing with topics such as climate variability hansen and takahashi 1984 the global carbon cycle sundquist and broecker 1985 catastrophes and earth history berggren and van couvering 1984 orbital insolation and periodicity berger et al 1984 and coastal upwelling suess and thiede 1983 some very useful books have been published which summarize existing information on radiolaria anderson 1983 neogene planktonic foraminifera kennett and srinivasan 1983 calcareous nannofossils haq 1983 1984 and biostratigraphy bolli et al 1983

pollen and radiolarian records from deep sea core rc14 103 climatic reconstructions of northeast japan and northwest pacific for the last 90 000 years using modern pollen and radiolarian distributions in sediments from the northwest pacific and seas adjacent to japan to interpret floral and faunal changes in core rc14 103 44 02 n 152 56 e we recognize two major responses of the biota of eastern hokkaido and the northwest pacific to climatic changes since the last interglaciation relatively stable glacial environments 80 000 20 000 yr b p were basically cold and wet 8 c and 1200 mm mean annual temperature and precipitation respectively supporting climax broadleaf deciduous forest with quercus and ulmus zelkova with surface waters in the northwest pacific characterized by warm 1 5 c winter and cold 10 4 14 3 c summer temperatures climatic evidence from rc14 103 shows a high degree of local and regional variation within the context of global climatic change correlative ocean and land records provide the detailed input necessary to assess local regional responses to variations in other key elements i e solar radiation monsoonal variations of the northeast asian climate system

late quaternary atmospheric and oceanographic variations in the western pacific inferred from pollen and radiolarian analyses abstract pollen and radiolarian analyses of sediment from four piston cores located along a south north transect 28 44 n off the east coast of japan yield detailed records of variations in terrestrial and marine climate of this region for the last 140 ka the last interglacial climate of the southern half of japan was characterized by increased temperature and precipitation at least across central japan compared with today off southern japan surface were cooler during summer than at present off central japan both summer and winter sea surface temperatures were cooler than today early glacial 115 71 ka bp climate across central and southern japan alternated between wet and dry warm temperate with surface waters offshore warmer in summer and winter than during the penultimate interglacial temperatures and precipitation in japan reached low levels early during the full glacial phase and remained relatively low throughout much of the full glacial 71 14 ka bp cold sea surface temperatures at all our sites coincided with these cold conditions on land temperatures across much of japan began to increase steadily during the deglacial with surface waters offshore remaining at or near their glacial lows holocene vegetation patterns which continued to reflect an increase in temperature reached a maximum during early to mid holocene surface waters offshore however remained relatively cool during the early holocene with temperature maxima at most western pacific sites occurring in mid to late holocene we propose specific changes in the seasonal positions of atmospheric pressure cells to explain these climate variations that have occurred across the northeast asian northwest pacific region through the most recent interglacial glacial cycle results of this exercise show that there are no major discrepancies between climate reconstructions for mainland japan inferred from pollen and those for the western pacific derived from radiolarians

identification of the guadalupian lopingian boundary in the permian in a bedded chert sequence south china abstract middle upper permian conodont biostratigraphy was examined in a bedded chert section in dachongling area of southeastern guangxi zhuang autonomous region south china four conodont zones were recognized namely jinogondolella granti zone clarkina postbitteri hongshuiensis zone clarkina postbitteri postbitteri zone and clarkina dukouensis zone in ascending order the four conodont zones can be correlated with those recognized previously in bathyal carbonate and lime chert sequences on the basis of the correlation we identified the guadalupian lopingian g l geochronostratigraphic boundary i e the basal boundary of lopingian series in the permian six radiolarian zones were also recognized in the same section namely pseudoalbaillella longtanensis zone pseudoalbaillella globosa zone follicucullus monacanthus zone follicucullus scholasticus zone follicucullus charveti zone and albaillella levis zone in ascending order correlations between radiolarian zones and conodont zones are shown here the ecological evolutionary process of conodonts and radiolarians changed abruptly through the inferred g l geochronostratigraphic boundary besides these a geochemical anomalous zone with the higher ce ce values occurred underlying the g l geochronostratigraphic boundary and petrological diagnoses around the g l boundary changed the abrupt change of ecological evolution in coincidence with the geochemical anomalous zone and change of petrological diagnoses might show the pre lopingian catastrophic event of marine faunas the reason of the event of marine faunas may be that a regression occurred at the end of the guadalupian

climate and environmental changes for the past 44 ka clarified by pollen and algae composition in the ulleung basin east sea japan sea abstract the pollen and algae records derived from core kces 1 in the east sea japan sea reveal vegetation and climate changes during the past 44 ka from 44 to 36 cal ka bp forest vegetation in the coastal regions of ulleung basin was composed predominantly of subalpine conifer forest open grassland covered the exposed continental shelves indicating a cool and dry climate during the period of 36 28 3 cal ka bp a warmer and wetter climate caused the contraction of subalpine conifer forest in the coastal regions of ulleung basin and the expansion of marsh in the exposed continental shelves from 28 3 to 17 6 cal ka bp the sea level decline restricted the herbs pollen originates in the exposed shelf of east china sea and yellow sea inflow into the east sea japan sea and caused the reduction of herbs pollen in the site location during the time interval of 17 6 15 1 cal ka bp a great expansion of subalpine conifer forest can be regarded as the consequence of enhanced east asian winter monsoon eawm the obvious increase in temperate deciduous broadleaved trees spores and algae can be attributable to the rising of sea level and the warming of climate from 15 1 to 12 1 cal ka bp during the period of 12 1 to 5 3 cal ka bp broadleaved taxa increased especially during the time period of 9 5 5 3 cal ka bp evergreen broadleaved trees pollen reach the highest values throughout the core as a result of the holocene climate optimum condition vegetation changes controlled by humid impacts occurred at the late holocene as indicated by an increase in pinus pollen

constraining the cause of the end guadalupian extinction with coupled records of carbon and calcium isotopes abstract a negative c 13 excursion in carbonate sediments near the guadalupian lopingian middle late permian boundary has been interpreted to have resulted from a large carbon cycle disturbance during the end guadalupian extinction event ca 260 ma however the carbon isotope data alone are insufficient to uniquely determine the type and magnitude of perturbation to the global carbon cycle calcium isotopes can be used to further constrain the cause of a carbon isotope excursion because the carbon and calcium cycles are coupled via caco3 burial in this study we present coupled carbon and calcium isotope records from three guadalupian lopingian g l sections in china penglaitan and chaotian and turkey koserelik tepe the c 13 and ca 44 40 records differ among our studied sections and do not co vary in the same manner no section shows c 13 and ca 44 40 changes consistent with massive rapid volcanic co2 emissions or methane clathrate destabilization additionally many sections with large 3 changes in c 13 exhibit o 18 evidence for diagenetic alteration only one section exhibits a large excursion in the ca 44 40 of limestone but the absence of a similar excursion in the ca 44 40 of conodont apatite suggests that the limestone excursion reflects a mineralogical control rather than a perturbation to the global calcium cycle hence we interpret the large isotopic changes observed in some sections to have resulted from local burial conditions or diagenetic effects rather than from a large carbon and calcium cycle disturbance perturbations to the global carbon and calcium cycles across the g l transition were much less intense than the disturbances that occurred across the subsequent permian triassic boundary this finding is consistent with the much smaller magnitude of the end guadalupian extinction relative to the end permian

facies analysis and sea level change at the guadalupian lopingian global stratotype laibin south china and its bearing on the end guadalupian mass extinction abstract the guadalupian lopingian boundary stratotype at penglaitan and the nearby tieqiao section near laibin south china record a series of major environmental changes within the jiangnan basin during a mid permian biotic crisis the sequence stratigraphic petrographic and palaeontological record of these sections has been studied and the associated strontium isotopic fluctuations have been assayed mass extinction of fusulinid foraminifers is most clearly associated in time with onset of volcanism and a relative sea level fall that led to the establishment of mid ramp conditions laibin limestone in settings that were previously dominated by radiolarian mudstones the regression also coincides with a low point of 87 sr 86 sr ratios the lowstand deposits contain mafic scoriaceous grains that record pyroclastic volcanism probably centred in the emeishan flood basalt province 800 km to the west of laibin thus unusually violent eruptions associated with flood basalts in this province may have contributed to the environmental stresses responsible for the extinction event subsequent environmental changes included transgression spread of dysoxic waters indicated by populations of small pyrite framboids and a major negative c isotope excursion all these phenomena have been previously related to the end guadalupian extinction but they in fact post date the crisis because a post extinction fauna of foraminifers is encountered at this time

paleoenvironmental changes in the japan sea during the last 85 000 years five distinct changes in the paleoenvironment of the japan sea within the last 85 000 years are revealed from the sedimentary record of a piston core recovered from the oki ridge changes in both surface and deepwater conditions are registered by changes in lithology calcium carbonate content organic carbon content oxygen and carbon isotope ratios and microfossil assemblages including calcareous nannoplankton diatoms radiolaria and foraminifera between 85 and 27 ka the warm tsushima current did not flow into the japan sea and cold surface water conditions prevailed environments at the seafloor fluctuated between dysaerobic to weakly oxic conditions between 27 and 20 ka freshwater input to the japan sea probably from the huang ho river in china stratified the water column and the severe anoxic conditions eliminated most benthic fauna between 20 and 10 ka the cold oyashio current flowed into the japan sea through the tsugaru strait reestablishing deepwater ventilation shallow water benthic assemblages of the north pacific ocean subsequently colonized the japan sea and occupied the vacant niches of the deep basins between 10 and 8 ka the foraminifer compensation level fcl gradually rose to a depth shallower than 1000 m and bottom conditions changed from dysaerobic to oxic at 10 ka the warm tsushima current started to flow into the japan sea through the tsushima strait to establish the modern oceanographic regime which has existed since 8 ka the eustatic sea level during the last glacial maximum was above the sill depths 130 m of the tsushima and tsugaru straits assuming that tectonic movements at these straits were negligible for the last 20 ka

variability in sulfur isotope records of phanerozoic seawater sulfate the s of seawater sulfate reflects processes operating at the nexus of sulfur carbon and oxygen cycles however knowledge of past seawater sulfate s values must be derived from proxy materials that are impacted differently by depositional and post depositional processes we produced new timeseries estimates for the s value of seawater sulfate by combining 6710 published data from three sedimentary archives marine barite evaporites and carbonate associated sulfate with updated age constraints on the deposits robust features in multiple records capture temporal trends in the s value of seawater and its interplay with other phanerozoic geochemical and stratigraphic trends however high frequency discordances indicate that each record is differentially prone to depositional biases and diagenetic overprints the amount of noise quantified from the variograms of each record increases with age for all s proxies indicating that post depositional processes obscure detailed knowledge of seawater sulfate s s value deeper in time

late pleistocene holocene paleoenvironmental changes inferred from the diatom record of the ulleung basin east sea sea of japan abstract the diatom floral record from two piston cores 00ghp 01 and 00ghp 07 taken from the southwestern margin of the ulleung basin east sea sea of japan reveals a series of well defined changes in glacio eustatic sea level and paleoceanographic conditions during the late pleistocene holocene six assemblage zones and two barren zones in 00ghp 01 and four assemblage zones in 00ghp 07 are erected respectively on the basis of frequency of variations in and occurrences of biostratigraphically significant diatom species all assemblage zones have been strongly influenced by the tsushima warm current twc the twc has an important affect on controlling the distribution and composition of diatom flora which in turn reveal the history of the twc in this area the distribution pattern of diatoms in the diatom assemblages reveals sea surface temperature and salinity affected by the sediments type and terrigenous material input diatom temperature td values show that the site of 00ghp 01 in the ulleung basin has been influenced by a relatively enhanced twc twice during the deposition of lowermost and uppermost intervals a relatively weak twc was recorded in the middle interval since the latest pleistocene the diatom assemblages of 00ghp 07 represent an apparently continuous late quaternary record spanning the last glacial maximum bolling allerod younger dyras and holocene high abundance of a low salinity coastal water diatom paralia sulcata may reflect the influx of the east china sea water through the korean strait to the east sea sea of japan during the last glacial maximum the sea level was low enough that selected basin with shallow sills along the margin of the east sea sea of japan became isolated from the pacific ocean salinity also decreased due to increased freshwater input from rivers draining the surrounding lands the density stratified water column may have prevented vertical mixing and resulted in anoxic bottom water conditions

sea level at the last glacial maximum constrained by oxygen isotopic curves of planktonic foraminifera in the japan sea the japan sea is connected with the okhotsk sea and northwest pacific through three straits viz mamiya tartarskiy soya and tsugaru and with the east china sea through tsushima strait all having sill depths of 3 recorded in the mis 3 4 sections of the studied cores this observation indicates nearly similar surface water conditions in the japan sea during both the previous glacial maxima and hence suggests negligible effect of strait tectonics on the sea level since the last 140 ka low d 18 opf values with small amplitude are also observed at the cold stage mis 6 4 but not observed at another cold stage mis 4 2 this observation suggests that the low salinity surface water in the japan sea started to develop at the sea level between mis 4 2 and 6 4 judging from the cross section of the tsushima strait and the sea floor topography of the east china sea the sea level between mis 4 2 and 6 4 must have been between 90 m and 100 m below the present from a proportional relationship between the standard d 18 o curve lr04 in deep sea cores and globally averaged sea level change the eustatic sea level obtained for the lgm is 120 7 m below the present thus the japan sea in a far field location from the continental ice sheets provides an important clue for estimation of the eustatic sea level at the lgm copyright 2012 john wiley sons ltd

carbon and sulfur isotopic fluctuations associated with the end guadalupian mass extinction in south china abstract concentrations of total organic matter toc carbon isotopic compositions of carbonate and organic matter 13 c carb 13 c org and sulfur isotopic compositions of carbonate associated sulfate 34 s sulfate across the guadalupian lopingian g l boundary were analyzed from identical samples of tieqiao section laibin guangxi province south china the 13 c carb values show a positive excursion from 0 45 to the peak of 3 80 in the laibin limestone member of the maokou formation followed by a drastic drop to 2 60 in the lowest heshan formation then returned to about 1 58 similar to the trends of the 13 c carb values 13 c carb org values also show a positive excursion followed by a sharp negative shift the onset of a major negative carbon isotope excursion postdates the end guadalupian extinction that indicates subsequent severe disturbance of the ocean atmosphere carbon cycle the first biostratigraphic 34 s sulfate values during the g l transition exhibit a remarkable fluctuation a dramatic negative shift followed by a rapid positive shift ranging from 36 88 to 37 41 these sulfate isotopic records suggest that the ocean during the g l transition was strongly stratified forming an unstable chemocline separating oxic shallow water from anoxic euxinic deep water chemocline excursions together with subsequent rapid transgression and oceanic anoxia were likely responsible for the massive diversity decline of the g l biotic crisis

sedimentary evidence for a rapid kilometer scale crustal doming prior to the eruption of the emeishan flood basalts biostratigraphic and sedimentologic investigations in 67 sections have been carried out for the middle permian maokou formation that immediately underlies the emeishan flood basalts in southwest china the results suggest a domal crustal thinning before the emplacement of the emeishan large igneous province variably thinned carbonates in the maokou formation are capped by a subaerial unconformity which is generally manifested by karst paleotopography paleoweathering zone or locally by relict gravels and basal conglomerates provenance analysis indicates that these gravels and conglomerates were mainly derived from the uppermost maokou formation therefore the stratigraphic thinning likely resulted from differential erosion due to regional uplift iso thickness contours of the maokou formation delineate a subcircular uplifted area in accordance with the crustal doming caused by a starting mantle plume as predicted by experimental and numerical modeling the duration of this uplift is estimated to be less than 3 myr and the magnitude of uplift is greater than 1000 m the sedimentary records therefore provide independent supporting evidence for the mantle plume initiation model for the generation of the emeishan flood basalts

short note on petrographically differentiating the anatomical characteristics of saprotrophied and carbonised inertinite group macerals the use of inertinite macerals as palaeoenvironmental and palaeoclimatic indicators is reliant on understanding their origin criteria to distinguish between carbonisation and pyrolysis or saprotrophy resulting from fungal degradation are not always clear without the presence of primary particles in coal such as fungal sclerota hyphae char and fly ash the origin of inertinites is difficult to distinguish this short study provides an insight into basic anatomical characteristics which differentiate saprotrophied and carbonised inertinite group macerals modern plant matter and permian phyterals are compared petrographically to observe changes in the macerals at a cellular level saprotrophic effects include thickening of the cell wall and cellular damage delignification of the cell wall and cross ray piths and the irregular oxidation radiating from xylem tissues these characteristics are not observed in carbonised inertinites that show enlarged ray cells and the shrinking and homogenisation of cell walls the simple differentiation between these characteristics in inertinites can greatly affect the palaeoenvironmental interpretations linked to the presence of inertinites in coal

the carbon isotope excursion on gssp candidate section of lopingian guadalupian boundary an isotopic stratigraphically well documented outcrop in penglaitan guangxi province south china has been proposed as a candidate gssp for the lopingian guadalupian boundary correlatable outcrops from the west wing tieqiao section and east wing penglaitan section of the laibin syncline exhibit synchronous excursions in carbon isotopes the isotopic excursions 13c show the best placement of the boundary may lie at the base of bed 6k which coincides with the clarkina postbitteri conodont zone and with eustatic change 13c increases during the uppermost guadalupian jinogondolella granti conodont zone from the top of 3c to the base of 6i a 13c peak value of 5 is located at the transition between these two conodont zones and is suggested as a proxy for the transition from transgression to regression a gradual depletion of carbon isotopes occurs in the c postbitteri zone from bed 6e to 7b and this gradual 13c excursion also suggests the sequences around the guadalupian lopingian boundary at the candidate section are conformable during the middle later c postbitteri zone a 3 5 dramatic 13c depletion is recorded at the tieqiao section but only a 2 depletion at the deeper facies penglaitan section synchronous with conodont zones that mark eustatic changes

a neogene seawater sulfur isotope age curve from calcareous pelagic microfossils abstract until now our knowledge of the sulfur isotopic composition of seawater through geologic time has depended on stable isotopic analysis of sulfate from evaporites owing to the sporadic occurrence of evaporites through time the secular sulfur isotope age curve contains many gaps with little or no data in order to fill in some of these gaps particularly the neogene we have analyzed the sulfur isotopic composition of carbonate associated sulfate in carbonate tests of planktonic foraminifera other investigators have shown that sulfate may occur in biogenic calcites either lattice bound as micro fluid inclusions in adsorbed phases or as protein polysaccharides whatever the origin the sulfur isotopic composition of this sulfate appears to be representative of that of the water in which the organism lived as shown by results on recent calcareous foraminifera and macrofossils using this approach for study of miocene to recent pelagic marine sediments supplemented by new data for miocene marine evaporites from the gulf of suez we have found that the 34 s of seawater has decreased about 2 5 over the past 25 m y and that most of the decrease has occurred over the past 5 m y parallelling a decrease in the 13 c of dissolved oceanic bicarbonate from the same interval sedimentary redox models based on isotope records suggest that organic carbon and sulfide burial have both decreased over the past 5 m y alternatively an increase in weathering rates over the past 5 m y would not require a decrease in organic carbon or sulfide burial as long as the isotopic effect of the increased river input exceeds the isotopic effect of the burial of the reduced species in either case the net result would be a decrease in atmospheric p o 2

a temporal link between the emeishan large igneous province sw china and the end guadalupian mass extinction abstract previous studies have suggested that there were two mass extinction events in the late permian one that occurred at the permo triassic p t boundary 251 ma and a second smaller mass extinction that occurred 5 8 myr earlier at the end of the guadalupian many workers have argued that there is a causal relationship between large scale volcanic activity and mass extinctions the major mass extinction event at the p t boundary coincides with the outpouring of huge quantities of lava that formed the siberian flood basalt province in russia courtillot et al earth planet sci lett 166 1999 177 195 and wignall earth sci rev 53 2001 1 33 suggested that the earlier late permian mass extinction coincided with the eruption of the lavas that formed the emeishan flood basalt efb province in sw china however the age of eruption of the efb lavas is poorly constrained using the sensitive high resolution ion microprobe to analyze zircons we have established the age of the xinjie intrusion believed to be a feeder to the main phase of efb volcanism to be 259 3 ma hence the formation of the efb is coincident with a proposed extinction event at 256 259 ma this result supports a temporal link between the emeishan large igneous province and the end guadalupian mass extinction

diagenetic controls on the isotopic composition of carbonate associated sulphate in the permian capitan reef complex west texas late palaeozoic age strata from the capitan reef in west texas show facies dependent heterogeneity in the sulphur isotopic composition of carbonate associated sulphate which is trace sulphate incorporated into carbonate minerals that is often used to reconstruct the sulphur isotopic composition of ancient seawater however diagenetic pore fluid processes may influence the sulphur isotopic composition of carbonate associated sulphate these processes variously modify the sulphur isotopic composition of incorporated sulphate from syndepositional seawater in shelf crest outer shelf shelf margin and slope depositional settings this study used a new multicollector inductively coupled plasma mass spectrometry technique to determine the sulphur isotopic composition of samples of individual depositional and diagenetic textures carbonate rocks representing peritidal facies in the yates and tansill formations preserve the sulphur isotopic composition of guadalupian seawater sulphate despite alteration of the carbon and oxygen isotopic compositions by meteoric and dolomitizing diagenetic processes however sulphur isotopic data indicate that limestones deposited in reef and slope facies in the capitan and bell canyon formations largely incorporate sulphate from anoxic marine phreatic pore fluids isotopically modified from seawater by microbial sulphate reduction despite generally preserving the carbon and oxygen isotopic compositions of permian seawater some early and all late meteoric calcite cements have carbonate associated sulphate with sulphur isotopic compositions distinct from that of permian seawater detailed petrographic and sedimentary context for carbonate associated sulphate analyses will allow for improved reconstructions of ancient seawater composition and diagenetic conditions in ancient carbonate platforms the results of this study indicate that carbonate rocks that diagenetically stabilize in high energy environments without pore fluid sulphate gradients can provide a robust archive of ancient seawater s sulphur isotopic composition

global climate perturbations during the permo triassic mass extinctions recorded by continental tetrapods from south africa several studies of the marine sedimentary record have documented the evolution of global climate during the permo triassic mass extinction by contrast the continental records have been less exploited due to the scarcity of continuous sections from the latest permian into the early triassic the south african karoo basin exposes one of the most continuous geological successions of this time interval thus offering the possibility to reconstruct climate variations in southern laurasia from the middle permian to middle triassic interval both air temperature and humidity variations were estimated using stable oxygen 18op and carbon 13cc isotope compositions of vertebrate apatite significant fluctuations in both 18op and 13cc values mimic those of marine records and suggest that stable isotope compositions recorded in vertebrate apatite reflect global climate evolution in terms of air temperature oxygen isotopes show an abrupt increase of about 8 c toward the end of the wuchiapingian this occurred during a slight cooling trend from the capitanian to the permo triassic boundary ptb at the end of the permian an intense and fast warming of 16 c occurred and kept increasing during the olenekian these thermal fluctuations may be related to the emeishan south china and siberian volcanic paroxysms that took place at the end of the capitanian and at the end of the permian respectively vertebrate apatite 13cc partly reflects the important fluctuations of the atmospheric 13c values the differences with marine curves being likely due to the evolution of local humidity both the oxygen and carbon isotope compositions indicate that the ptb was followed by a warm and arid phase that lasted 6 ma before temperatures decreased during the late anisian toward that of the end permian environmental fluctuations occurring around the ptb that affected both continental and marine realms with similar magnitude likely originated from volcanism and methane release

revisiting the origin of organic matter and depositional environment of sediment in the central ulleung basin east sea since the late quaternary abstract by analyzing sedimentary geochemical data from three piston cores in the central ulleung basin east sea we discuss the origin of organic matter and the depositional environment of sediments from marine isotope stage mis 3 to 1 downcore profiles show that the values of toc total organic carbon tn total nitrogen and 13corg are the lowest values during mis 2 and the highest during mis 1 the relationship between toc tn and 13corg shows that most data fall in the region of the marine algae irrespective of mis stage which illustrates that the organic matter has been predominantly produced by a marine source rather than by a terrestrial source since the late quaternary however depleted 13corg values are discretely observed during mis 2 and mis 3 particularly in dark laminated mud dlm which appears to reflect the influence of episodic event by the east asian monsoon rather than the organic matter source changing by lower sea level previous sedimentological studies in the ulleung basin reported that the depositional environment of sediment in mis 2 was more reducing than during mis 1 and mis 3 but our geochemical data do not support this interpretation the abundance of most redox sensitive trace elements e g mn v u and mo has not significantly varied from mis 3 to mis 1 in addition the ratios of redox sensitive trace elements e g ni co v cr v ni u th and v v ni indicate a predominantly oxic or suboxic environment the bottom water condition was similarly oxic to suboxic during times of sediment deposition since the late quaternary the sedimentary layers containing tephra and foraminiferal shell fragments illustrate abnormal element al ratios suggesting that these allochthonous sediment sources are one of important factors controlling the geochemical composition of sediments in the ulleung basin

permian palaeogeographic evolution of the jiangnan basin south china abstract the most striking geographic feature of the permian of south china is the jiangnan basin which intimately reflects the interplay between the yangtze and cathaysia blocks geographic and sedimentological evolution suggests that the jiangnan basin superposed on a precambrian collisonial megasuture and a folded early paleozoic deep basin was an extensional intracratonic basin it opened in the longlinian and became more passive and restricted in the latest maokouan the remarkably similar geographic patterns of the jiangnan basin in the early and late palaeozoic suggest that the yangtze and cathaysia blocks were coherent during the paleozoic

an isotopic study of biogeochemical relationships between carbonates and organic carbon in the greenhorn formation carbon isotopic compositions of total carbonate inoceramid carbonate micritic carbonate secondary cements total organic carbon and geoporphyrins have been measured in 76 different beds within a 17 m interval of a core through the greenhorn formation an interbedded limestone and calcareous shale unit of cretaceous age cenomanian turonian from the western interior seaway of north america results are considered in terms of variations in the processes of primary production which led to the biosynthesis of the molecular precursors of the geoporphyrins and in secondary processes those mediating the transformation of primary organic material into sedimentary total organic carbon it is shown that the porphyrin isotopic record reflects primary isotopic variations more closely than the toc isotopic record and that in these sediments toc is enriched in 13c relative to its primary precursor by 0 6 to 2 8 this enrichment is attributed to isotope effects within the consumer foodweb and is associated with respiratory heterotrophy variations in this secondary enrichment are correlated with variations in the isotopic composition of marine carbonate this correlation is attributed to effects of environmental changes on the marine foodweb these may have included increased atmospheric oxygen associated with the cenomanian turonian oceanic anoxic event the isotopic fractionation associated with fixation of carbon by primary producers is observed to have varied by 1 5 during the interval of deposition it is suggested that this change is due to a variation in the makeup of the community of primary producers and or to a decrease in the atmospheric abundance of co2 during the oceanic anoxic event

abrupt ventilation changes in the japan sea over the last 30 ky evidence from deep dwelling radiolarians abstract the japan sea has its own deep circulation system with its deeper parts occupied by cold and highly oxygenated water formed by winter convection in its northwestern reaches we elucidate the modern depth distribution of radiolarian species and their relation to water masses from the study of plankton tows and surface sediments cycladophora davisiana occurs in a depth interval between 1000 m and 2000 m deep layer of jspw japan sea proper water and actinomma boreale leptoderma group in depths below 2000 m bottom layer of jspw the study of seven sediment cores located in water depths ranging from 807 to 3613 m show that the radiolarian assemblages have varied since 30 cal ka bp indicating changes in water ventilation strength in this marginal sea during the interval from 30 to 17 cal ka bp ventilation was restricted to an intermediate layer beneath the low salinity surface water while the deeper zone was filled with static anoxic water deep ventilation began abruptly at 14 cal ka bp cold and oxygen rich water began to sink into the bottom layer as a result of cold oceanic inflow from the northwestern pacific through the tsugaru strait in the north deep convection activity increased from 13 to 12 cal ka bp which coincides with the younger dryas like cooling event and then stopped at 12 11 5 cal ka bp bottom water ventilation during the holocene has been dependent on high salinity inflow through the tsushima strait in the south and winter cooling in the northwestern part of the japan sea deep water was being actively formed in the early holocene in contrast to the static bottom water this bottom water formation has resulted in relatively constant water composition since 9 cal ka bp with the overall increase in high salinity oceanic water inflow although the latter decreased transiently from 7 to 5 cal ka bp in concert with climatic warming

mass extinctions and sea level changes abstract review of sea level changes during the big five mass extinctions and several lesser extinction events reveals that the majority coincide with large eustatic inflexions the degree of certainty with which these eustatic oscillations are known varies considerably thus the late ordovician and end cretaceous extinctions are associated with unequivocal major regressions demonstrated from numerous widespread regions in contrast the multiple high frequency sea level changes reported for the frasnian famennian crisis based on the supposed depth preferences of conodont taxa have little support from sequence stratigraphic analyses which reveals the interval to be one of highstand the end permian mass extinction has long been related to a severe first order lowstand of sea level newell n d 1967 revolutions in the history of life geol soc am spec pap 89 63 91 based primarily on the widespread absence of latest permian ammonoid markers but field evidence reveals that the interval coincides with a major transgression newell s hypothesis that marine extinctions are related to shelf habitat loss during severe regression remains tenable for the end guadalupian and end triassic extinction events but not for other crises rapid high amplitude regressive transgressive couplets are the most frequently observed eustatic changes at times of mass extinction with the majority of extinctions occurring during the transgressive pulse when anoxic bottom waters often became extensive the ultimate cause of the sea level changes is generally unclear a glacioeustatic driving mechanism can only be convincingly demonstrated for the end ordovician and end devonian events at other times it is speculated that they may relate to the widespread regional doming and subsequent collapse caused by the impingement of superplumes and ultimate eruption on the base of the lithosphere

early holocene climatic instability in japan organic geochemical evidence in sediment cores from lake biwa lake kizaki and the japan sea abstract sediment cores from lake biwa shiga prefecture and lake kizaki nagano prefecture provide evidence of variations in the climate of japan subsequent to the end of the last glacial period concentrations of organic carbon increase in sediments deposited after the pleistocene holocene boundary as wetter climates washed in more soil nutrients and aquatic productivity increased organic matter c n ratios simultaneously decrease indicating smaller proportions of land derived plant matter lake biwa c n ratios and organic carbon isotope ratios fluctuate markedly between 10 and 4 kya suggesting that both delivery of land derived organic matter and production of lake derived organic matter were variable during this period of time similar variability in biotic paleoceanographic indicators has been reported in sediments from the oki ridge in the japan sea and has been interpreted to record early holocene fluctuations in the intensity of the tsushima current such fluctuations in this warm water current are likely to have caused concordant fluctuations in climate on honshu a relationship that explains the variability in rainfall evident in the organic matter of the lake sediments

late pleistocene holocene radiolarian and pollen records from sediments in the sea of okhotsk in two cores with oxygen isotope stratigraphy from the southern okhotsk sea marine pollen and siliceous microfauna record concurrent late glacial through holocene variations in regional terrestrial and marine environments glacial vegetation around the southern okhotsk basin which resembles the present tundra steppe of the northwest coast of this marginal sea yields to spruce dominated boreal forests during the glacial interglacial transition temperate forest components such as oak peak during the mid holocene decreasing oak accompanied by increasing spruce reflects the effect of global cooling on local vegetation during the last 4 kyr although the radiolarian fauna in the okhotsk sea samples is similar to that present in the northwest pacific the dominant species in both regions differ concentrations of radiolarians are low in latest glacial samples with higher concentrations occurring above and below this interval cycladophora davisiana the dominant radiolarian species in the majority of holocene okhotsk sea sediments is present at lower percentages in late glacial samples from our two sites thus this species holocene latest pleistocene abundance pattern in sea of okhotsk sediments is the reverse of that recorded in high latitude open ocean sites the combined marine pollen and radiolarian records indicate changes in the sea of okhotsk s physical oceanographic conditions and surrounding vegetation during the late glacial which were associated with this region s response to global climate change

a negative carbon isotope anomaly associated with the earliest lopingian late permian mass extinction abstract palaeozoic life was severely affected in a pair of mass extinction events at the beginning earliest lopingian 260 million years ago and the end 251 million years ago of the late permian however the biological and geochemical record of the earliest lopingian crisis remains poorly constrained we present analyses of strata in south china showing that a negative anomaly of stable carbon isotope ratios accompanied an abrupt extinction of marine faunas at the beginning of the late permian similar to patterns observed at the end permian and the end cretaceous 65 million years ago extinction events

application of the trace element and isotope geochemistry of strontium to studies of carbonate diagenesis carbonate rocks and natural waters exhibit a wide range in the concentration and isotopic composition of strontium this wide range and the quantifiable covariation of these parameters can provide diagnostic tools for understanding processes of fluid rock interaction careful consideration of the uncertainties associated with trace element partitioning sample heterogeneity and fluid rock interaction mechanisms is required to advance the application of the trace element and isotope geochemistry of strontium to studies of diagenesis goundwater evolution ancient seawater chemistry and isotope stratigraphy a principal uncertainty involved in the application of sr concentration variations to carbonate systems is the large range of experimental and empirical results for trace element partitioning of sr between mineral and solution this variation may be a function of precipitation rate mineral stoichiometry crystal growth mechanism fluid composition and temperature calcite and dolomite in ancient limestones commonly have significantly lower sr concentrations 20 70 p p m than would be expected from published trace element distribution coefficient values and sr ca ratios of most modern sedimentary pore waters this discrepancy probably reflects the uncertainties associated with determining distribution coefficient values as techniques improve for the analytical measurement and theoretical modelling of sr concentration and isotopic variations the petrological analysis of carbonate samples becomes increasingly important the presence of even small percentages of non carbonate phases with high rb concentrations and high 87 sr86 sr values such as clay minerals can have significant effects on the measured 87 sr 86 sr values of carbonate rocks due to the decay of 87rb to 87 sr for example a permian marine limestone with 50 p p m sr and 1 p p m rb will have a present day 87 sr 86 sr value that is 2 10 4 higher than its original value this difference is an order of magnitude greater than the analytical uncertainty and illustrates the importance of assessing the need for and accuracy of such corrections a quantitative evaluation of the effects of water rock interaction on sr concentrations and isotope compositions in carbonates strengthens the application of these geochemical tracers geochemical modelling that combines the use of trace elements and isotopes can be used to distinguish between different mechanisms of water rock interaction including diffusive and advective transport of diagenetic constituents in meteoric pore fluids during the recrystallization of carbonate minerals quantitative modelling may also be used to construct diagnostic fluid rock interaction trends that are independent of distribution coefficient values and to distinguish between mixing of mineral end members and fluid rock interaction

orbital and millennial scale fluctuations in late quaternary marine pollen records from the japan sea quaternary surface water conditions within the japan sea change with eustatic sea level changes and fluctuations in the east asian summer monsoon easm influencing regional climate and vegetation through the delivery of heat and moisture our marine pollen data suggest overall cooling from the last interglacial ca 125 ka to the last glacial maximum lgm a cold climate during marine isotope stage mis 2 gradual warming from 12 ka and rapid warming after 10 ka these stages are concordant with published palaeoceanographic changes in the japan sea during mid mis 5 to mis 3 marine sediments in the japan sea are characterised by fine alternations of dark and light coloured layers that formed under the influence of fluctuations in the easm possibly correlated with dansgaard oeschger cycles during the deposition of dark layers high levels of precipitation are inferred from the abundance of cryptomeria in contrast a cool and dry climate is interpreted for the light layers based on an abundance of subarctic conifer pollen the palaeoclimate of the japan sea region appears to have been influenced by orbital scale changes in global climate and millennial scale fluctuations in the easm copyright 2009 john wiley sons ltd

are late permian carbon isotope excursions of local or of global significance we present a new biostratigraphically calibrated organic and inorganic c isotope record spanning the basal late permian to earliest triassic from southern guizhou nanpanjiang basin south china after fluctuations of a likely diagenetic overprint are removed three negative carbon isotope excursions cies persist these include a short lived cie during the early wuchiapingian a protracted cie ending shortly after the wuchiapingian changhsingian boundary and a third cie straddling the permian triassic boundary comparison of our new c isotope record with others from the same basin suggests that influences of local bathymetry and of the amount of buried terrestrial organic matter are of importance comparison with other coeval time series outside of south china also highlights that only the negative cie at the permian triassic boundary is a global signal these differences can be explained by the different volumes of erupted basalts between the late permian emeishan and the younger siberian large igneous provinces and their distinct eruptive modalities emeishan volcanism was largely submarine implying that sea water was an efficient buffer against atmospheric propagation of volatiles the equatorial position of emeishan was also an additional obstacle for volatiles to reach the stratosphere and benefit from an efficient global distribution consequently the local significance of these cies calls into question global correlations based on c isotope chemostratigraphy during the late permian the timing of the late permian chinese cies is also not reflected in changes in species diversity or ecology unlike the sudden and global permian triassic boundary crisis and subsequent early triassic upheavals

detailed japan sea paleoceanography during the last 25 kyr constraints from ams dating and δ18o of planktonic foraminifera abstract we have reconstructed paleoceanographic changes in the japan sea for the period from the last glacial maximum lgm to the present using expanded paleoclimate proxy records from two cores together with previously published results from three others a suite of new accelerated mass spectrometer ams 14 c dates provides chronologies that differ from earlier age models and suggest correlation between conditions in the japan sea changes in the north pacific and global sea level and climate changes we present evidence that reduced salinity of the japan sea surface water during the late pleistocene was due primarily to the increased importance of the precipitation evaporation balance at a time when lowered sea level had reduced water exchange with the pacific to a few percent of the present value

large perturbations of the carbon and sulfur cycle associated with the late ordovician mass extinction in south china high resolution 13 c data of organic carbon from a continuous section of the late ordovician early silurian reveal two positive 13 c excursions that are associated with the mass extinction in south china the fi rst stratigraphic 34 s measurements on pyrite tied to well established biostratigraphy indicate a large perturbation of the sulfur cycle consistent with major sea level changes related to the glaciation the elevated 34 s values of pyrites and a large short lived negative 34 s excursion of 20 associated with the decay of the glaciation suggest deep water anoxia during the hirnantian stage in contrast to the conventional view that the global oceans were oxygenated we suggest that deep water anoxia may have contributed to the late ordovician mass extinction in south china and possibly elsewhere

methane release from igneous intrusion of coal during late permian extinction events abstract unusually large and locally variable carbon isotope excursions coincident with mass extinctions at the end of the permian period 253 ma and guadalupian epoch 260 ma can be attributed to methane outbursts to the atmosphere methane has isotopic values 13c low enough to reduce to feasible amounts the carbon required for isotopic mass balance the duration of the carbon isotopic excursions and inferred methane releases are here constrained to 10 000 yr by counting annual varves in lake deposits and by estimating peat accumulation rates on paleogeographic maps the most marked carbon isotope excursions form linear arrays back to plausible methane sources end permian siberian traps and longwood bluff intrusions of new zealand and end guadalupian emeishan traps of china intrusion of coal seams by feeder dikes to flood basalts could create successive thermogenic methane outbursts of the observed timing and magnitude but these are unreasonably short times for replenishment of marine or permaf

climatic and oceanographic isotopic signals from the carbonate rock record and their preservation stable isotopic data from marine limestones and their constituent fossils and marine cements can provide quantitative evidence for changes in global climate and ocean circulation oxygen isotopic data can indicate changes in temperature and ocean composition whereas stratigraphic variation in carbon isotope ratios may reflect changes in the carbon cycle that can be linked to changes in oceanic productivity and atmospheric greenhouse gases terrestrial carbonates meteoric cements calcretes and speleothems similarly offer significant potential for understanding the evolution of terrestrial climates by providing evidence for the composition of rainwater and the nature of vegetative cover primary environmental isotopic signals may be obscured by the effects of post depositional diagenetic alteration cementation and replacement reactions can take place in a wide range of diagenetic environments the diagenetic history of an individual limestone is determined by a combination of its mineralogical diagenetic potential and depositional setting together with subsequent changes in relative sea level and burial history carbon isotopic values are less prone to alteration during diagenesis than oxygen values but shifts can be significant where organogenic carbon is incorporated linear covariation of carbon and oxygen values is not a reliable indicator of diagenetic alteration water rock interaction and fluid mixing may produce non linear distributions attempts to determine long term changes in climatic and oceanographie conditions through isotope stratigraphy of shallow water limestones must include an assessment of the diagenetic history of the materials analysed petrographic examination using conventional microscopy backed up where appropriate by cathodoluminescence and scanning electron microscopy together with elemental and strontium isotopic analysis can help to identify the effects of diagenetic alteration where material with a range of different degrees of alteration is preserved in the same sediment it may be possible to compare patterns of isotopic and elemental variation and to attempt to unravel the effects of diagenesis in order to determine primary environmental isotopic signals recent research has shown that these techniques can be successfully employed in both phanerozoic and precambrian sediments

multiple sulfur isotope records at the end guadalupian permian at chaotian china implications for a role of bioturbation in the phanerozoic sulfur cycle abstract a recent study on quadruple sulfur isotopes 32s 33s 34s and 36s of sedimentary pyrite suggested that the end guadalupian extinction was caused by shoaling of the sulfidic deep water this scenario is based on the assumption that sulfur isotopic compositions of pyrite from hosting sediments were controlled by benthos activities thus by the redox conditions of the sedimentary environments nonetheless the relationship between the sulfur isotope records and redox conditions reconstructed from litho and bio facies are poorly known in order to examine the effect of bioturbation in sediments quadruple sulfur isotopic compositions of sedimentary pyrite from the end guadalupian succession in chaotian south china were analyzed black mudstones of deep water facies immediately below the extinction horizon have consistently high 33s values of ca 0 079 clearly suggesting a sulfate reduction in the anoxic water column our new data are consistent with the emergence of a sulfidic deep water mass prior to the end guadalupian extinction the upwelling of the toxic deep water may have contributed to the extinction in contrast shallow marine bioclastic limestones with burrows deposited under oxic conditions have negative 33s values this anomalous isotopic signal indicates the mixing of two distinct types of pyrite one generated during the sulfate reduction in an open system and the other in a closed system we interpret that bioturbation supplied sulfate in the sediments and promoted sulfate reduction and in situ sulfide precipitation within the sediments the negative 33s values of oxic sediments in chaotian are inconsistent with the previous model and demonstrate that the sedimentary sulfur cycle associated with bioturbation was more complicated than previously thought our study also implies that more generally the role of bioturbation in increasing seawater sulfate concentration in the phanerozoic may have been overestimated in the previous studies because bioturbation may have enhanced sulfide burial or sulfur output from the oceans

latest pleistocene and holocene palaeoenvironment of japan and its marginal sea abstract analyses of pollen and radiolarian abundance variations in a deep sea core from the sea of japan indicate that major vegetational changes on mainland japan during the last 80 000 years coincided with events of similar magnitude offshore in the marginal sea on land dry cold temperate conditions alternate with wet cold temperate periods throughout most of the last glacial period 80 000 10 000 yr b p offshore during glacial times of low winter precipitation the radiolarian fauna was dominated by assemblage similar to those present today along the subarctic front and throughout much of the subpolar gyre associated with cold winter and summer sea surface temperatures during most of the high precipitation stadials the dominant radiolarian assemblage was comparable with that existing in today s sea of okhotsk associated with cold winter and cool summer sea surface temperatures on the western coast of honshu warmer temperate conditions throughout the holocene were associated with a marine faunal assemblage similar to that living in waters overlying the core site today radiolarian abundance levels productivity were lower during most of the last glacial period compared to holocene values the presence of radiolaria throughout all but a portion of the early stage of the last glacial interval indicates that although restricted some degree of exchange between the southern sea of japan and north pacific waters took place throughout most of the last glacial period these data place major constraints on local reconstructions of sea level and of climate on the adjacent coast of honshu during this time

orbital and millennial scale changes of radiolarian assemblages during the last 220 kyrs in the japan sea abstract significant abundance changes of seven radiolarian species during the last 220 kyrs in the japan sea are reported herein based on three sediment cores during the interglacial periods warm water species the tetrapyle octacantha group and warmer high nutrient water species lithomelissa setosa occurred commonly which may indicate inflows of the tsushima warm current on the other hand cold water species such as ceratospyris borealis and stylochlamydium venustum dominated the assemblage during the glacial periods when the japan sea was mostly isolated from the adjacent seas due to lower eustatic sea level however at glacial maxima the habitat of s venustum was strongly limited due to low salinity surface waters the abundance of the deep water species cycladophora davisiana seems to have changed significantly possibly related to the intrusion of oxygen and organic materials into deeper waters higher abundances of this species in mis marine isotope stage 1 mis 3 and mis 5c resulted from well ventilated deep water and high organic flux while its low abundance during the glacial maxima and mis 5e was probably caused by oxygen poor deep water millennial scale variations of c davisiana abundance show high abundance at the transition intervals from interstadial to stadial periods of the dansgaard oeschger cycles the disappearance events of lychnocanoma nipponica sakaii and amphimelissa setosa were recognized at 54 ka and 85 ka respectively both of these events in the japan sea can be correlated with those in the north pacific bering sea and sea of okhotsk

stable isotope record implicates aridification without warming during the late capitanian mass extinction abstract the late capitanian mass extinction 260 million years ago represents one of the greatest biotic perturbations of the phanerozoic and was the earliest mass extinction to affect terrestrial tetrapods and ecosystems in the past this extinction has been largely associated with taxonomic loss and ecological restructuring in marine environments but more recently it has also been recognised in terrestrial ecosystems though various environmental mechanisms have been proposed for the former little evidence has yet been presented for the cause of terrestrial extinctions we determined the stable oxygen and carbon isotope compositions of dentine apatite from twenty eight specimens of the dicynodont therapsid diictodon feliceps to investigate the potential role of climate in driving terrestrial tetrapod extinctions studied specimens were recovered from a 270 m stratigraphic interval constraining the peak in tetrapod extinction rates in the uppermost abrahamskraal formation in the well sampled main karoo basin of south africa our results demonstrate a positive excursion of 13c values coinciding with the extinction peak that is followed by a return to pre extinction 13c values suggesting a local increase in aridity at the time of the extinction for the same time interval the 18o values did not demonstrate statistically significant changes suggesting constant temperature in the south african paleoenvironment this unusual increase in aridity but not in temperature has been interpreted as the possible result of orogenesis in the cape fold mountain source along the southern margin of gondwana

sulfur isotopic evidence for chemocline upward excursions during the end permian mass extinction the latest permian was a time of major change in ocean chemistry accompanying the greatest mass extinction of the phanerozoic to examine the nature of these changes samples from two well studied marine sections that span the permian triassic boundary have been analyzed the meishan and shangsi sections located in southern china isotopic analysis of the carbonate associated sulfate in these samples provides a detailed record of several isotopic shifts in 34scas approaching and across the ptb ranging from 30 to 15 vcdt with repeated asynchronous fluctuations at the two locations we interpret the patterns of isotopic shifts in conjunction with other data to indicate a shallow unstable chemocline overlying euxinic deep water which periodically upwelled into the photic zone these chemocline upward excursion events introduced sulfide to the photic zone stimulating a bloom of phototrophic sulfur oxidizing bacteria we hypothesize that elemental sulfur globules produced by these organisms and 34s depleted pyrite produced in the euxinic water column were deposited in the sediment later oxidation led to incorporation as cas this created the large changes to the 34scas observed in the latest permian at these locations

restoration of reef ecosystems following the guadalupian lopingian boundary mass extinction evidence from the laibin area south china abstract the guadalupian lopingian boundary glb also middle late permian boundary mass extinction severely destroyed metazoan reef ecosystems although some studies argued that both biotic and environmental turnover across the glb are not so obvious when compared with prolifically developed reefs in the capitanian the wuchiapingian reef examples appear depauperate and almost 89 of the carbonate production in these bioconstructions was lost here we report a typical sponge reef from the wuchiapingian stage in the tieqiao section central guangxi province south china the tieqiao reef might represent the only example of a wuchiapingian metazoan reef in the eastern palaeo tethys region it provides insight into ecosystem restoration following the glb extinction major constructors of the tieqiao reef are sponges peronidella parauvanella sollasia tabulozoa and amblysiphonella algae anthracoporella archaeolithporella permocalculus gymnocodium and tubiphytes this reef is well constrained as middle late wuchiapingian in age by the clarkina orientalis conodont zone carbonate carbon isotope excursions experienced negative spikes near the glb and multiple perturbations in the early middle wuchiapingian and remained relatively stable during re establishment of metazoan reefs in middle late wuchiapingian conodont oxygen isotopes showed that the sea surface temperature sst was extremely high 30 c during late capitanian time punctuated by a short cooling event and global regression associated with the glb extinction and followed by high sst and rapid rise in sea level in the early wuchiapingian the reemergence of the tieqiao reef coincided with the initial cooling in surface oceans and sea level fall during the middle late wuchiapingian accordingly reef ecosystems experienced a long term depletion worldwide in early middle wuchiapingian time and then recovered 2 5 myr after the glb extinction based on estimate in integration of both conodont biostratigraphy and radiometric ages

volcanism mass extinction and carbon isotope fluctuations in the middle permian of china the 260 million year old emeishan volcanic province of southwest china overlies and is interbedded with middle permian carbonates that contain a record of the guadalupian mass extinction sections in the region thus provide an opportunity to directly monitor the relative timing of extinction and volcanism within the same locations these show that the onset of volcanism was marked by both large phreatomagmatic eruptions and extinctions amongst fusulinacean foraminifers and calcareous algae the temporal coincidence of these two phenomena supports the idea of a cause and effect relationship the crisis predates the onset of a major negative carbon isotope excursion that points to subsequent severe disturbance of the ocean atmosphere carbon cycle

asian aridity and the zonal westerlies late pleistocene and holocene record of eolian deposition in the northwest pacific ocean rea d k and leinen m 1988 asian aridity and the zonal westerlies late pleistocene and holocene record of eolian deposition in the northwest pacific ocean palaeogeogr palaeoclimatol palaeoecol 66 1 8 a 30 000 year record of eolian deposition in the northwestern pacific ocean provides a history of the aridity of the asian source region and information on the changing latitude and intensity of the zonal westerlies the position of the maximum in eolian flux to the deep sea remained unchanged at 38 to 40 n during this entire time period but the dust flux record of aridity is greatest 6000 years ago at the holocene climatic optimum eolian grainsize data indicate that the northern margin of the westerly jet stream retreated northward during the holocene to a poleward extreme at about 6000 years ago and then moved back toward the equator the change in wind intensity across this margin was continually reduced throughout the holocene these sorts of data enhance our understanding of the behavior of the atmosphere during times of climate change and can be used to test computer generated models of past climatic conditions

permo triassic boundary superanoxia and stratified superocean records from lost deep sea pelagic cherts of japan and british columbia canada recorded a long term and worldwide deep sea anoxic oxygen depleted event across the permo triassic or paleozoic and mesozoic boundary 251 2 million years ago the symmetry in lithostratigraphy and redox condition of the boundary sections suggest that the superocean panthalassa became totally stratified for nearly 20 million years across the boundary the timing of onset climax and termination of the oceanic stratification correspond to global biotic events including the end guadalupian decline the end permian extinction and mid triassic recovery

paleo tsushima water and its effect on surface water properties in the east sea during the last glacial maximum revisited abstract the semi enclosed deep marginal east sea is known by limited sill flow and low sea surface salinity during the last glacial maximum lgm when sea level was about 130 m lower than the present level although three straits the tsugaru the soya and the tartar with shallower than 130 m sills were completely closed the korea strait with a maximum sill depth of 140 m seems to have persisted as a partial connection to the east sea allowing a sill flow the volume transport at the korea strait during the lgm is estimated at approximately 0 3 1 1 1012 m3 yr by using bathymetry seismic reflection profiles and current data the low sea surface salinity has been explained by the east china sea coast water ecscw and high precipitation however the existing geological observations indicate that precipitation was reduced in the glacial east sea the high resolution numerical simulation results predict that evaporation 2 16 mm day exceeded precipitation 1 43 mm day further suggesting net evaporation evaporation minus precipitation rates 0 2 1012 m3 yr over the lgm east sea this signifies that the precipitation was not the factor lowering surface paleosalinity and that the paleo tsushima water carried a huge amount of freshwater from the ecscw than previously expected the calculated surplus evaporation 0 2 1012 m3 yr and sill flow 0 3 1 1 1012 m3 yr are not identical but they could be oceanographically considered as similar the comparison between both values implies that most of the throughflow ultimately escaped the east sea through the evaporation process during the lgm the regional sea level in the almost isolated east sea might be largely maintained by a rough balance between incoming throughflow and outgoing evaporation during the lgm the geographic restriction due to lowered sea level and lower surface salinity by limited vertical mixing in the glacial east sea are analogous to modern oceanographic features in the black sea

mineralogical association and physical properties of sediments with palaeoclimatic implications odp site 798b japan sea a comparative study from core and downhole measurements abstract the aim of our approach is to provide a reliable and continuous mineralogical description derived from downhole logs and constrained by core measurements this study focuses on a series of 742 000 year drilled during ocean drilling program odp leg 128 at site 798 on oki ridge japan sea a linear matrix algebraic procedure has been applied to eight logs bulk density neutron porosity natural gamma ray uranium thorium and potassium concentrations photoelectric effect and electrical resistivity to compute the proportions of opal quartz clay minerals illite chlorite kaolinite smectite and water in the sediment similarly a continuous cation exchange capacity cec log is derived from the natural gamma ray cgr a continuous intrinsic formation factor ff which depends on the structure of the pore space is then computed from the cec the log derived mineralogy and cec are compared to laboratory analysis on samples high resolution mineralogy derived from the logs allows recognition of well known episodes of climate evolution development of glaciation and of aeolian processes at 2 5 2 3 ma as well as new insights into climate dynamics occurrences of short warm excursions and of unstable periods periodic oscillations in relation to orbital parameters are also deduced from log derived mineralogy

interpreting carbon isotope excursions carbonates and organic matter abstract variations in the carbon isotopic compositions of marine carbonate and organic carbon provide a record of changes in the fraction of organic carbon buried through time and may provide clues to changes in rates of weathering and sources of organic carbon paired carbonate and organic carbon isotope determinations provide a possibility of interpreting not only changes in the global carbon cycle through time but changes in atmospheric pco2 as well interpretations of these types of data are typically rather qualitative a quantitative basis is required to develop a better understanding of changes in the carbon cycle for this purpose we employ a simple model of the global carbon cycle which is subjected to a number of different perturbations each lasting 500 ky i e much longer than the residence times of carbon and phosphorus in the ocean atmosphere system in addition to standard considerations of carbon mass and isotopic fluxes to the ocean atmosphere system from weathering and volcanism and fluxes of organic carbon and carbonate carbon to sediments the model incorporates sensitivity of the photosynthetic carbon isotope effect to changes in pco2 the inclusion of this parameter leads to unexpected carbon isotope responses to forcing that causes increased rates of organic carbon burial a series of simple to more complex simulations illustrates the significant effects of varying differences between the carbon isotopic composition of sedimented carbonate and organic carbon b with constant b a 50 increase in organic carbon burial produces a parallel increase in carbonate and organic carbon isotopic compositions however the same simulation with b responsive to pco2 changes produces an initial parallel 13 c increase but this is followed by an even greater 13 c enrichment in organic carbon because pco2 falls in response to increased organic carbon burial the counterintuitive overall result of the enhanced organic carbon burial event is that the carbonate carbon isotopic composition actually decreases because of the more substantial increase in 13 c org in addition we illustrate the effects on carbon isotopic compositions of the oceanic inorganic carbon reservoir and buried organic matter of a 50 increase in volcanic co2 outgassing a 50 increase in weathering rate with coupled phosphate and riverine carbon flux responses a 50 decrease in shale associated organic carbon weathering a 50 decrease in silicate weathering rate and the possible effects of the rise in abundance of c4 plants in the late miocene to recent we compare the model simulated carbon isotopic responses for some of these experiments to paired carbonate and organic carbon records to illustrate how these records might be interpreted in light of the model response

sea level surface salinity of the japan sea and the younger dryas event in the northwestern pacific ocean abstract the japan sea was profoundly different during glacial times than today available 18 o evidence indicates that sea surface salinity was lower by several per mil this probably increased the stability of the water column and caused anoxic sedimentary conditions in the deep sea as shown by the absence of benthic microfossils and the presence of laminated sediment these changes are likely related to the effects of late quaternary sea level change on the shallow sills ca 130 m across which the japan sea exchanges with the open ocean the hwang he yellow river has previously been implicated as the source of fresh water to the japan sea during glaciation but the possible roles of the amur river and excess precipitation over evaporation must also be considered ambiguous radiocarbon chronologies for the latest quaternary of japan sea cores do not adequately constrain the timing of salinity lowering previous studies have suggested that lowest sea surface salinity was achieved 27 000 to 20 000 14 c yr b p however if global sea level fall restricted exchange with the open ocean circulation then lowest salinity in the japan sea may have occurred as recently as 15 000 to 20 000 yr ago when sea level was lowest if this alternative is correct then as sea level abruptly rose about 12 000 yr ago relatively fresh water must have been discharged to the open pacific this might have affected the dynamics of outflow local faunal and floral expression of the polar front and stable isotope ratios in foraminifera these environmental changes could be misinterpreted as evidence for the cooling of younger dryas age which has not been identified in nearby terrestrial records