climate instability during the last interglacial period recorded in the grip ice core isotope and chemical analyses of the grip ice core from summit central greenland reveal that climate in greenland during the last interglacial period was characterized by a series of severe cold periods which began extremely rapidly and lasted from decades to centuries as the last interglacial seems to have been slightly warmer than the present one its unstable climate raises questions about the effects of future global warming

spatial and temporal variation of geochemical properties and paleoceanographic implications in the south korea plateau east sea during the late quaternary geochemical opal total organic carbon toc and caco3 analyses of three sediment cores from the south korea plateau in the east sea japan sea revealed that the late quaternary 190 kyr bp to the present paleoceanographic conditions are characterized by the orbital variations of geochemical properties that have recorded the changes of surface and bottom water conditions chronostratigraphy of the sediment cores was accomplished by the direct correlation of l values to the well dated core md01 2407 in oki ridge supplement to the ams 14c dates well known lithostratigraphic and tephrostratigraphic markers biogenic opal concentrations are high during marine isotope stage mis 1 and mis 5 5 and low during the glacial period suggesting that diatom production was enhanced during the warm period when the surface water exchange between the east sea and adjacent marginal seas was active in contrast glacial opal paleoproductivity appears to have been depressed probably because of insufficient nutrient availability resulting from limited vertical ventilation overall toc contents follow the orbital variations high during the interglacial and relatively low during the glacial time however high resolution toc fluctuations are independent of opal concentration which may be attributed more to the preservation of organic matter rather than to the surface water production the high toc contents in the thin dark mud i e tl layers may be due to the enhanced surface water production as well as the intensified bottom water anoxia on the other hand high caco3 contents associated with the tl layers during the glacial and stadial period may be attributed to the reduced dissolution the temporal variations of these geochemical properties are likely to follow the global orbital cycles indicating the significant changes of surface and bottom water properties due to the eustatic sea level fluctuations between the interglacial and glacial period the comparable values of these geochemical properties among the sediment cores suggest that the spatial paleoceanographic conditions in the south korea plateau were consistent and uniform during the late quaternary in spite of a little local discrepancy in amounts of properties and timing of events

environmental conditions for the presence of magnetofossils in the last glacial maximum inferred from magnetic parameters of sediments from the ulleung basin east sea abstract magnetic characterization of sediments from the ulleung basin in the east sea japan sea was carried out to decipher changes in environmental conditions over the last 39 000 years magnetic susceptibility intensities of natural remanent magnetization nrm anhysteretic remanent magnetization arm partial arm parm and saturation isothermal remanent magnetization sirm were measured for selected samples irm acquisition hysteresis and first order reversal curve forc measurements were made the ratios of rock magnetic parameters such as arm sirm arm and s ratio were determined to identify magnetic grain size and mineralogical variations along with electron microscope observations of magnetic mineral extracts down core variations in rock magnetic parameters for the 5 21 m long sediment core reveal distinct intervals with different grain size concentration and composition of magnetic minerals the uppermost portion and the high magnetic intensity zone hiz in marine isotope stage mis 2 are characterized by higher concentrations of fine grained magnetite whereas the mis 1 and 3 intervals contain lower concentrations of coarser grained magnetic minerals with increasing influence of hematite and or iron sulphide minerals the hiz interval is inferred to contain high occurrences of fine grained bacterial magnetosomes based on geochemical proxies east sea conditions for the hiz interval coincident with the last glacial maximum lgm can be summarized as having low total organic carbon toc enhanced eolian contributions from terrestrial organic particles and iron bearing minerals under the influence of an intensified east asian winter monsoon along with iron reducing but not sulphidic conditions that favoured growth and preservation of magnetotactic bacteria the delicate balance between reductive dissolution of magnetofossils under sulphidic conditions and production and preservation of magnetotactic bacteria in overlying iron reducing sediments for the hiz interval is responsible for the resultant abundance variations of magnetosomes in the studied sediments

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

late glacial stage and holocene tropical ice core records from huascaran peru two ice cores from the col of huascaran in the north central andes of peru contain a paleoclimatic history extending well into the wisconsinan wurm glacial stage and include evidence of the younger dryas cool phase glacial stage conditions at high elevations in the tropics appear to have been as much as 8 to 12 c cooler than today the atmosphere contained about 200 times as much dust and the amazon basin forest cover may have been much less extensive differences in both the oxygen isotope ratio 18o 8 per mil and the deuterium excess 4 5 per mil from the late glacial stage to the holocene are comparable with polar ice core records these data imply that the tropical atlantic was possibly 5 to 6 c cooler during the late glacial stage that the climate was warmest from 8400 to 5200 years before present and that it cooled gradually culminating with the little ice age 200 to 500 years before present a strong warming has dominated the last two centuries

orbital and millennial scale paleoceanographic changes in the north eastern japan basin east sea japan sea during the late quaternary two gravity sediment cores gh99 1239 and gh99 1246 obtained from the north eastern japan basin in the east sea japan sea were analyzed for the orbital and millennial scale paleoceanographic changes chronostrati graphically core gh99 1239 represents a continuous sedimentary record since 32 ka based on correlation of distinct lithological markers i e dark layer or tl layer with those in core gh98 1232 collected nearby for core gh99 1246 the age model is constructed through correlation of lightness l values and tephra aso 4 and toya layers with those in the well dated oki ridge core md01 2407 indicating about 134 ka of sedimentation since the latest marine isotope stage mis 6 new geochemical data from both cores corroborate orbital scale paleoceanographic variation such that surface water productivity represented by biogenic opal and total organic carbon toc contents increased during mis 1 and mis 5 caco3 contents do not show such distinct glacial interglacial cycles but were influenced by dissolution and preservation rather than foraminiferal production during the glacial periods when sea ice was prevalent surface water productivity was low and bottom water conditions became anoxic as indicated by high total sulfur ts contents and high mo concentrations the geochemical data further document millennial scale paleoceanographic variability corresponding to a series of thin tl layers in response to dansgaard oeschger cycles but irrespective of the glacial or interglacial periods in particular thin tl layers formed during mis 3 are characterized by less toc about 1 and ts about 0 4 contents and lower mo about 5 p p m concentration whereas those during mis 4 and mis 5 exhibit more toc up to 4 and ts up to 5 contents and higher mo up to 120 p p m concentration such a discrepancy is attributed to different degree of surface water productivity and of bottom water oxygenation which is closely related to the sea level position and extent of ventilation flux of the east china sea coastal water controlled by millennial scale paleoclimatic events is the most critical factor in deciding the properties of tl layers in the north eastern japan basin our results strongly confirm that tl layers in the japan basin also validate the unique feature of basin wide paleoceano graphic signals in the east sea japan sea copyright 2011 john wiley sons ltd

the fecal pellet fraction of biogeochemical particle fluxes to the deep sea fecal pellets produced by suspension feeding crustacean zooplankton specifically copepods and euphausids have frequently been cited as an important mode of large particle transport in the open ocean the objectives of the present study were to determine the various biogeochemical fluxes provided by pelagic crustacean fecal pellets to examine such fluxes as a function of depth and variable levels of surface water productivity and to assess the overall fecal pellet contribution to oceanic particle fluxes as measured with sediment traps pellet subsamples were obtained from particulate samples collected at depths between 389 and 5068 m by moored parflux sediment traps deployed for up to 12 months at three tropical subtropical open ocean localities the sites were located over the east hawaii abyssal plain p site over the demerara abyssal plain e site and in the pacific panama basin pb site fecal pellet flux and chemical composition were found to vary significantly on a geographic scale as a function of productivity levels in the surface waters the total carbonate organic carbon opaline silica and lithogenic fluxes provided by pellets at the oligotrophic p1site were 1 2 orders of magnitude less than that measured at the eutrophic station in panama basin the pellet data show that contrary to previous assumptions these biogenic aggregates are responsible for no more than 5 of the total mass flux of oceanic particulate material despite the fact that at all trap depths large numbers of intact pellets were collected which displayed minimal effects of dissolution and microbial degradation fecal pellets contributed an average of only 1 10 0 5 5 1 3 and 0 5 4 to the total measured mass fluxes of organic carbonate opaline silica and lithogenic material respectively however the pellets showed elevated c n ratios 9 14 as well as high organic content representing up to 50 of the individual pellet weight suggesting that they constitute an important source of organic carbon for the deep sea benthos rapid remineralization of the organic rich pellets must occur at the deep sea sediment water interface as these biogenic aggregates were completely absent from all site core tops

ocean chemistry during glacial time abstract measurements of co2 to air ratios in the gas trapped in bubbles in ice of glacial age suggest that the co2 content of the atmosphere was considerably lower during peak glacial time than during holocene time the purpose of this paper is to show that such a change must in all likelihood be the result of alterations in the nutrient element chemistry of sea water two possible scenarios are presented one involves alternate storage and erosion of phosphorous leaving residues from shelf sediments the other involves changes in the c p ratio in the organic debris falling to the deep sea means of verifying the nutrient cycle hypothesis are also given it is shown that the 13c record as we know it in planktonic and benthic foraminifera the oxygen record as inferred from benthic foraminifera species distributions and the early post glacial caco3 preservation event as recorded by aragonitic pteropods are consistent with both of the hypotheses presented only if an early post glacial spike in the 13c record for planktonic shells could be found would it be possible to eliminate one of these hypotheses i e that involving shelf storage the implications of these nutrient hypotheses to climate theory are as follows if shelf storage is responsible for the glacial to interglacial co2 increase then the co2 change must be considered an amplifier of some primary cause the reason is that sea level changes are needed to drive deposition on and erosion from the shelves on the other hand if changes in the c p ratio for falling debris are responsible then the co2 change could either be an amplifier or a primary cause for the major glacial to interglacial climatic cycle the latter is possible as self sustained oscillations in ocean chemistry might be driven by interactions between ocean ecology and ocean nutrient chemistry

minor elements in quaternary sediment from the sea of japan a record of surface water productivity and intermediate water redox conditions sediment of quaternary age from oki ridge 903 m depth in the sea of japan 3500 m deep records six episodes of high accumulation rates of cd cr cu mo ni u v and zn the high rates correspond to periods of sulfate reduction in the water column at the intermediate depth of oki ridge the intervening low values correspond to periods of denitrification and oxygen respiration the maxima have a period of 41 k y the youngest having an age of 1 10 ma the 41 k y cycle is similar to the cycle of 18 o values of open ocean plankton of the same age the similarity between the cycles of minor element accumulation in sea of japan sediment and 18 o values of atlantic ocean foraminifera indicates that redox changes in the water column of the sea of japan during the quaternary forced by major shifts in water column advection and minor shifts in photic zone productivity reflect global events

late pleistocene continental climate and oceanic variability recorded in northwest pacific sediments core v21 146 provides a continuous record of northwest pacific pelagic sedimentation spanning the past 530 000 years downcore variations of 18o from benthic foraminiferal calcite were correlated to the specmap record to provide an age model for late pleistocene paleoclimatic and paleoceanographic variation fluxes of caco3 and eolian material have been determined by combining information about linear sedimentation rates bulk densities and component percentages the mass accumulation rate mar of caco3 varies from 58 to 1435 mg cm kyr 1 and exhibits the pacific ocean pattern of higher accumulation associated with glacial periods for the younger portion of the record however the pattern of caco3 accumulation appears to shift during the mid brunhes so that prior to 350 000 years ago it exhibits an opposite pattern of greater accumulation during interglacial periods the flux of eolian dust is a proxy measure of the source area aridity and correlates well to the loess soil stratigraphy in china dust fluxes range from 43 to 718 mg cm kyr 1 and are greater by a factor of about 4 during glacial times cross spectral analysis of the eolian flux and oxygen isotope records shows an inphase and coherent relationship at each of the major orbital periodicities of 100 41 and 19 kyr eolian grain sizes generally used as a proxy record of wind intensity range from 8 4 2 9 m to 6 2 13 6 m a change in grain size variability occurs near about 300 ka such that the older portion is characterized by lower frequency and higher amplitude fluctuations than the younger portion power spectra for the eolian grain size record show dominant peaks at 100 and 50 kyr and a broad 25 35 kyr peak but coherency to the oxygen isotope curve at only the 100 and 33 kyr periodicities the phase relationship for eccentricity between the eolian grain size and 18o records suggests that at the 100 kyr frequency the smallest grain sizes are associated with glacial conditions

characterization of airborne carbonate over a site near asian dust source regions during spring 2002 and its climatic and environmental significance 1 during spring 2002 three dust storm events were monitored by filter sampling in xi an near an asian dust source region of northwest china the carbonate co32 fraction was determined by sample acidification and thermal evolution the co32 accounted for 8 0 0 8 of particles with aerodynamic diameter 2 5 m pm2 5 during dust storms and 4 7 3 0 of pm2 5 between storms the ratios of calcium to carbonate carbon were consistent with those of calcite caco3 the 13c and 18o abundances in dust storm samples were 2 7 0 7 and 5 8 1 5 which differed from 8 3 1 9 for 13c and 10 8 2 0 for 18o during normal conditions the 13c is positively correlated with 18o values r 0 78 this first measurement of isotopic abundance in asian dust indicates the potential to quantify its contribution at distant locations using receptor models by increasing the alkalinity of ocean water in the pacific ocean and buffering the atmospheric acidity of east asia the large amounts of airborne co32 as high as 44 8 tg yr 1 entrained by asian dust may provide an important atmospheric alkaline carbon reservoir for large scale climatic and environmental changes

has the atmospheric supply of dissolved calcite dust to seawater influenced the evolution of marine 87sr 86sr ratios over the past 2 5 million years 1 by analyzing the geochemistry of chinese loess this study examines if the flux of calcite dust from the chinese loess plateau to the north pacific influenced the evolution of marine 87sr 86sr ratios between 2 5 million years ago ma and the present calcite comprises 10 wt of chinese loess and contains 1 104 nmol of sr g with an 87sr 86sr ratio of 0 711 a compilation of literature data suggests that the calcite dust flux emanating from eastern asia has averaged either 2 1013 or 1 1014 g yr since the onset of northern hemisphere cooling 2 5 ma the factor of 5 difference between the estimates reflects discrepancies inherent to methods for determining dust fluxes to seawater at present these discrepancies remain unresolved calcite dust is completely dissolved during transport in the atmosphere and ocean thus the marine sr input from eolian calcite dissolution has averaged either 2 108 or 1 109 mol yr a mass balance model demonstrates that the lower estimate has very little influence on seawater 87sr 86sr ratios whereas the higher estimate has possibly elevated seawater 87sr 86sr ratios by 18 since 2 5 ma when combined with previously reported effects of northern hemisphere glaciation on the riverine sr flux this shift is sufficient to reproduce the entire plio pleistocene marine sr record while more research is required to constrain dust flux estimates these findings suggest that the atmospheric supply of eolian calcite to seawater may represent a previously overlooked process linking climate change to the marine sr cycle

deglacial sea level record from tahiti corals and the timing of global meltwater discharge the timing of the last deglaciation is important to our understanding of the dynamics of large ice sheets1 and their effects on the earth s surface2 3 moreover the disappearance of the glacial ice sheets was responsible for dramatic increases in freshwater fluxes to the oceans which probably disturbed the ocean s thermohaline circulation and hence global climate4 7 sea level increases bear witness to the melting of continental ice sheets but only two such records from barbados8 9 and new guinea10 11 corals have been accurately dated but these corals overlie active subduction zones where tectonic movements are large and often discontinuous especially in new guinea so the apparent sea level records may be contaminated by a complex tectonic component here we date fossil corals from tahiti which is far from plate boundaries and thus is likely to be tectonically relatively stable and remote from the locations of large former ice sheets the resulting record indicates a large sea level jump shortly before 13 800 calendar years bp which corresponds to meltwater pulse 1a in the barbados coral records8 9 the timing of this event is more accurately constrained in the tahiti record revealing that the meltwater pulse coincides with a short and intense climate cooling event12 15 that followed the initiation of the bolling allerod warm period12 16 but preceded the younger dryas cold event by about 1 000 years

late pleistocene dark laminated mud layers from the korea plateau western east sea japan sea and their paleoceanographic implications abstract a variety of approaches were applied to a 11 1 m long sediment core ebp 4 from the korea plateau one of the bathymetric highs in the western part of the east sea japan sea to understand late pleistocene paleoenvironmental change the chronostratigraphy of the core was established using a radiocarbon age dark laminated mud dlm layers with known ages the oxygen isotope 18 o curve of planktonic foraminifera biogenic opal and total organic carbon toc contents downcore changes in the carbon nitrogen c n ratio as well as their isotopic ratio 13 c and 15 n in organic matter although interrupted by several pumice lapilli layers the core bottom represents marine isotope stage mis 8 and spans more than 250 kyr of paleoceanographic history of the western east sea japan sea paleoenvironmental conditions during mis 2 and mis 6 are clearly distinguishable represented by the negative shift of 18 o values of planktonic foraminifera resulting from surface water freshening due to basin isolation caused by eustatic sea level lowering the corresponding dark laminated mud dlm i ii a ii b and iii layers formed during glacial maxima are characterized by strong mo and total sulfur ts enrichment in anoxic conditions which indicates a stagnant and strongly stratified water column structure biogenic opal contents can be a useful indicator to confirm the chronostratigraphic assessment and can also identify periods of high surface water productivity in the east sea japan sea particularly during interglacial times in contrast glacial paleoproductivity might be low compared to the interglacial because of insufficient nutrient availability resulting from limited vertical ventilation the 13 c and 15 n values of sedimentary organic matter also emphasize increased terrestrial input during the glacial maxima exhibiting highly depleted 13 c and 15 n values in all dlm layers sea level induced paleoenvironmental changes associated with glacial interglacial variations are identified from the korea plateau confirming these events occurred throughout the whole east sea japan sea

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

high resolution holocene and late glacial atmospheric co2 record variability tied to changes in thermohaline circulation here we present results from a new method for detecting changes in atmospheric co2 based on 13c analyses of selected peat components from a peat core in southern south america the paleo co2 record has decadal resolution spanning the last 14 000 radiocarbon years and compares well with antarctic ice core co2 data sharp peaks in co2 are detected during the late glacial specifically at 10 200 11 600 and 12 900 years b p when compared to two deep sea records interpreted to reflect changes in thermohaline circulation these co2 pulses appear to relate to degassing events of the ocean associated with reinitiation of the thermohaline circulation occurring at this time concomitant decreases in atmospheric 14c during the late glacial are also consistent with a deep oceanic carbon source for the large atmospheric pulses in co2 results from a simple three box model indicate that the magnitude of the co2 released during these degassing events is compatible with our observations the rate of degassing however is much slower than that observed in the paleo co2 record two broad holocene co2 excursions are also identified with peaks at 4 200 and 7 700 years b p the driving mechanism behind these excursions appears to be different than those in the late glacial

glacial interglacial co2 change the iron hypothesis several explanations for the 200 to 280 ppm glacial interglacial change in atmospheric co2 concentrations deal with variations in southern ocean phytoplankton productivity and the related use or nonuse of major plant nutrients an hypothesis is presented herein in which arguments are made that new productivity in today s southern ocean 7 4 1013g yr 1 is limited by iron deficiency and hence the phytoplankton are unable to take advantage of the excess surface nitrate phosphate that if used could result in total southern ocean new production of 2 3 1015 g c yr 1 as a consequence of fe limited new productivity holocene interglacial co2 levels preindustrial are as high as they were during the last interglacial 280 ppm in contrast atmospheric dust fe supplies were 50 times higher during the last glacial maximum lgm because of this fe enrichment phytoplankton growth may have been greatly enhanced larger amounts of upwelled nutrients may have been used and the resulting stimulation of new productivity may have contributed to the lgm drawdown of atmospheric co2 to levels of less than 200 ppm background information and arguments in support of this hypothesis are presented

middle ordovician chazy group cavity dwelling boring sponges microcavities in lower middle ordovician bryozoan mounds from the laval formation chazy group near montreal quebec contain evidence that endolithic boring sponges were present ramose borings with scalloped walls and swellings resembling endolithic sponge galleries faceted carbonate grains similar to modern sponge chips and siliceous spicules both in situ on the cavity wall or roof and in the sediment all point to the activities of endolithic sponges in the hard substrate of the wall and roof coelobiontic cavity dwelling endolithic sponges therefore infested cavities in skeletal mounds and reefs in the middle ordovician and appear to have exploited the cavity habitat very soon after the appearance of metazoan skeletal reefs in the ordovician

glacial and interglacial wind regimes over the eastern subtropical atlantic and north west africa analysis of aeolo marine dust deposits in the subtropical eastern atlantic enables the strength of the major wind patterns during the late quaternary to be evaluated and gives an insight into the climate of north africa

increased negative anomalies of sedimentary organic matter δ13c and δ15n values in the east sea sea of japan during the full glaciation of the late quaternary abstract glacio eustatic sea level fluctuations and subsequent paleoceanographic changes in the east sea sea of japan have been identified by unique sedimentary features and their geochemical properties throughout the late quaternary sediments these events were synchronous basin wide the effect of sea level change in the east sea is fundamental to the anoxia of bottom water resulting from the stagnant strongly stratified water column with limited ventilation during the glacial periods the four sediment cores collected from the japan basin yamato basin and korea plateau in the east sea showed extraordinarily co varied 1 3 c and 15 n values of sedimentary organic matter representing distinct negative anomalies of both isotopes for the thick dark laminated mud layers formed during full glaciations mis 2 and mis 6 of the late quaternary the most plausible cause to induce such peculiar isotope variations is the enhanced contribution of terrestrial organic detritus in addition to the anoxic diagenetic condition in the bottom water during the glacial times both of which are characterized by relatively low 13 c and 15 n values the aeolian contribution of terrigenous particles in the form of kosa supplied from inland china was intensified in the east sea during the last glacial maximum during the glacial periods the anoxic decay of sedimentary organic matter may lead not only to the reduction of 13 c values attributed to the selective preservation of 13 c depleted organic compounds but also to the decrease of 15 n values due to the addition of 15 n depleted organic matter by using soluble nitrogenous compounds and the bacterial growth adding 15 n depleted biomass to the residual materials thus the results argue against the utility of 1 3 c and 15 n values of sedimentary organic matter as a proxy of paleoproductivity and atmospheric p co 2 levels in a marginal sea environment such as the east sea

global variations of surface ocean productivity in low and mid latitudes influence on co2 reservoirs of the deep ocean and atmosphere during the last 21 000 years based on detailed reconstructions of global distribution patterns both paleoproductivity and the benthic 13c record of co2 which is dissolved in the deep ocean strongly differed between the last glacial maximum and the holocene with the onset of termination i about 15 000 years ago the new export production of low and mid latitude upwelling cells started to decline by more than 2 4 gt carbon year this reduction is regarded as a main factor leading to both the simultaneous rise in atmospheric co2 as recorded in ice cores and with a slight delay of more than 1000 years to a large scale gradual co2 depletion of the deep ocean by about 650 gt c this estimate is based on an average increase in benthic 13c by 0 4 0 5 the decrease in new production also matches a clear 13c depletion of organic matter possibly recording an end of extreme nutrient utilization in upwelling cells as shown by sarnthein et al 1987 the productivity reversal appears to be triggered by a rapid reduction in the strength of meridional trades which in turn was linked via a shrinking extent of sea ice to a massive increase in high latitude insolation i e to orbital forcing as primary cause

upper silurian lithistid sponge reefs on somerset island arctic canada the upper ludlow douro formation contains the first reported silurian sponge reefs these relatively small 5 35 m diameter mound shaped structures contain on average 35 lithistid demosponges reefs are surrounded by irregular haloes of crinoid debris abundance and diversity of all fossil groups decreases away from the reefs each reef is underlain by a lens of crinoid wackestone to grainstone rich in crinoid holdfasts trepostomate bryozoans solenoporacean algae and rhynchonellid brachiopods are locally common the bulk of each reef consists of lime mudstone with abundant lithistid sponges this is capped by a thin layer of wackestone with abundant tabulate and rugose corals and fewer lithistid sponges calcareous algae trepostomate bryozoans and stromatoporoids this zonation in which a sponge colonization community was replaced by a coral diversification community is similar to that reported from some middle ordovician upper jurassic and holocene sponge reefs the douro sponge reefs were relatively low structures with about 3 m maximum topographic relief they grew on a broad carbonate platform probably in warm tranquil turbid waters of normal or near normal marine salinity periodic influxes of terrigenous mud adversely affected reef size and caused biotic changes some of the reef lime mud was derived from non reef sources but significant quantities were also produced on the reefs reefs underwent synsedimentary lithification bioerosion and minor storm erosion fabrics and compositions of sparry calcite in cavities record three generations of meteoric cementation originally siliceous spicules of the lithistid sponges were dissolved and the moulds later filled with sparry calcite early dissolution of siliceous spicules is common in reef environments and may have caused fossil sponges to be under represented in ancient reefs

pleistocene climates in china dated by magnetic susceptibility the magnetic susceptibility of loess and interbedded soils in central china varies with the degree of pedogenesis and serves as a proxy measure of climate the concentration of magnetic minerals in the sediment is inversely proportional to sedimentation rates throughout the brunhes epoch susceptibility measurements combined with the reversal stratigraphy provide a time scale that is independent of astronomic chronology on this scale the susceptibility record closely parallels the oxygen isotope fluctuations in deep sea sediments suggesting a close interdependence of the chinese dust falls the volume of land based ice and global climate

paleoclimatic significance of eolian carbonates supplied to the japan sea during the last glacial maximum laminated sediments deposited under anoxic bottom waters in the japan sea during the last glacial maximum lgm contain extremely well preserved calcareous microfossils and eolian carbonates the radiocarbon age difference between bulk sediment and monospecific planktonic foraminifera in discrete laminae from a core in the southern japan sea implies that 40 of the total carbonates in the sediments at the lgm are of eolian origin extrapolation of this result yields a rate of supply of eolian carbonates of 2800 tons d 1 to the entire japan sea during the lgm the climatic significance of this flux potentially lies in its broader geographic extension particularly in the interaction of the carbonate bearing dust with shallow corrosive north pacific waters and with rain in the atmosphere by increasing the alkalinity of such waters and by enhancing the biological pump the dust flux could have increased co2 absorption by both the ocean and rain during the lgm

a direct link between the china loess and marine δ 18 o records aeolian flux to the north pacific most studies of quaternary climates conducted during the past 150 years have focused on glacial sequences and for the past 25 years marine sediments have provided significant further understanding of glacial and interglacial palaeoclimates an important goal of palaeoclimatology however to link the well known detailed continental records to marine records of similar resolution has yet to be realized the classic loess sequences of china provide an apparently continuous record of continental climate over the past 2 4 million years1 2 the oxygen isotope 18o timescale developed from the marine record3 gives us a global chrono stratigraphy of late pleistocene climates previously it has been suggested in studies of the aeolian component in pelagic sediments that it may be possible to link these two records directly by finding a suitable core from the north west pacific downwind from china4 5 here we report the results of such an effort for core v21 146 fig 1 and tie the last 500 000 years of the chinese loess soil sequence directly to the 18o timescale and in so doing refine the dating of regional loess and soil horizons

the cause of the glacial to interglacial atmospheric co2 change a polar alkalinity hypothesis in an attempt to create a scenario for the cause of the glacial to interglacial co2 change recorded in air trapped in polar ice we call on an increase in the alkalinity of polar surface waters in this way we circumvent a major deficiency of the polar nutrient scenarios of sarmiento and toggweiler 1984 siegenthaler and wenk 1984 and knox and mcelroy 1984 namely our scenario does not require a drop in the nutrient content of polar surface waters in conformity with the demonstration by boyle 1988a b that the cadmium content of planktonic foraminifera from polar regions did not decrease from late glacial to holocene time the rise in alkalinity required by our model is a natural consequence of the demise during glacial time of north atlantic deep water as a major force in ocean circulation and of the nutrient maximum deepening of boyle 1988b rather than being original our hypothesis builds on the concept basic to the polar nutrient hypotheses namely that the co2 partial pressure in polar waters controls that for both the atmosphere and warm surface ocean it also requires the alkalinity increase in surface waters produced by boyle s nutrient deepening

the sequence of events surrounding termination ii and their implications for the cause of glacial interglacial co2 changes events surrounding termination ii as preserved in the vostok ice core provide a number of clues about the mechanisms controlling glacial to interglacial climate change antarctic temperature and the atmosphere s co2 content increased together over a period of 8000 years this increase is bounded by a drop in dust flux at its onset and by a drop in the 18o of trapped air at its finish a similar lag between dust flux and foraminiferal 18o is seen in a southern ocean marine record suggesting that the 18o in air trapped in vostok ice is a valid proxy for ice volume the synchronous change of atmospheric co2 and southern hemisphere temperature thus preceded the melting of the northern hemisphere ice sheets this observation coupled with the fact that nutrient reorganization in the north atlantic occurs with or after the sea level rise eliminates many scenarios proposed to explain the co2 rise including those which rely on sea level change conveyor related nutrient redistribution or north atlantic cooling southern ocean scenarios become the front runners but the most popular mechanism iron fertilization has two problems in explaining the co2 rise before termination ii first much of the dust demise occurs prior to the change in co2 so if iron is the villain a threshold value of its supply must be called upon above which productivity does not continue to increase second the co2 rise continues for some 4 5 kyr after the dust flux has fallen to close to zero these problems may be solved if the increased iron supply in dust caused higher rates of nitrogen fixation during the glacial periods in this case the residence time of oceanic nitrate of a few thousand years would enable decreasing productivity to be a global rather than a local phenomenon and would explain the slow rampup of atmospheric co2

anatomy of an upper silurian transgressive regressive cycle prince of wales island arctic canada the ludlovian pridolian cape storm douro and somerset island formations on eastern prince of wales island form a transgressive regressive succession that developed on the western flank of the active boothia horst sedimentation took place in a series of fault bounded subbasins that were at different times characterized by abundant microbolites rhodolites brachiopods and organisms that produced a diverse array of ichnofossils integration of paleoecological information from this succession provides a multifaceted paleoecological model which can be applied to similar lithologically monotonous successions throughout the world three main factors controlled the distribution of biota through the transgressive regressive cycle the most obvious factor was ever changing depositional settings caused by progressive rise and fall in sea level superimposed on this general pattern however was the influence of water circulation and the influx of detrital quartz from the boothia horst the microbolites and

eolian evidence for spatial variability of late quaternary climates in tropical africa abstract study of the eolian fraction of late quaternary sediments from the tropical atlantic reveals that two modes of long term climate variability have existed in tropical africa during the last 150 000 yr tropical northwest africa i e the southwestern sahara and sahel was driest during glaciations and stades but wetter than at present during interglaciations and interstades this may be a response to ice sheets at higher latitudes via equatorward displacement of the westerlies and the subtropical high in contrast central equatorial africa southeast of the sahara was most arid during interstades and times of ice growth and most humid during deglaciation wet periods in this area correspond to insolation maxima in northern hemisphere summer a 23 000 yr precessional rhythm is suggested supporting a direct link between african monsoon intensity and orbitally modulated insolation the late holocene is the only time observed when both areas are arid during an interglacial episode this may reflect in part anthropogenic disturbance of late holocene climates

instability of bottom water redox conditions during accumulation of quaternary sediment in the japan sea the concentrations of cd cr cu mo ni sb u v and zn were measured in early quaternary sediment 1 32 to 1 08 ma from the oki ridge in the japan sea the elements were partitioned between a detrital fraction composed of terrigenous and volcaniclastic aluminosilicate debris and a marine fraction composed of biogenic and hydrogenous debris derived from seawater the most important factors controlling minor element accumulation rates in the marine fraction were 1 primary productivity in the photic zone which largely controlled the flux of particulate organic matter bound minor elements settling through the water column and onto the seafloor and 2 bottom water redox which determined the suite of elements that accumulated directly from seawater this marine fraction of minor elements on oki ridge recorded six periods of high minor element abundance assuming a constant bulk sediment accumulation rate each period lasted roughly 5 000 to 10 000 years with a 41 000 year cycle accumulation rates of individual elements such as cd mo and u suggest sulfate reducing conditions were established in the bottom water during the 10 000 year periods accumulation rates of cr and v during the intervening periods are indicative of less reducing denitrifying conditions interelement ratios for example cu mo v cr and sb mo further reflect bottom water instability such that bottom water redox actually varied from sulfate reducing to denitrifying during the periods of highest minor element accumulation rates it varied from denitrifying to oxidizing during the intervening periods sediment lithology supports these interpretations of the minor element distributions the sediment is finely laminated for several of the periods represented by cd mo and u maxima and weakly laminated to bioturbated for the intervening periods the geochemistry of this sediment demonstrates the unambiguous signal of mo principally but of several other minor elements as well in recording sulfate reducing conditions in bottom water the forcing function that altered their accumulation that is that altered primary productivity and bottom water redox conditions is problematic currently held opinion suggests that o2 depletion was most strongly developed during glacial advances low sea level during such times is interpreted to have enhanced primary productivity and restricted bottom water advection

record of volcanism since 7000 b c from the gisp2 greenland ice core and implications for the volcano climate system sulfate concentrations from continuous biyearly sampling of the gisp2 greenland ice core provide a record of potential climate forcing volcanism since 7000 b c although 85 percent of the events recorded over the last 2000 years were matched to documented volcanic eruptions only about 30 percent of the events from 1 to 7000 b c were matched to such events several historic eruptions may have been greater sulfur producers than previously thought there are three times as many events from 5000 to 7000 b c as over the last two millennia with sulfate deposition equal to or up to five times that of the largest known historical eruptions this increased volcanism in the early holocene may have contributed to climatic cooling

untangling intricate microbial sponge frameworks the contributions of sponges to early ordovician reefs abstract the early ordovician witnessed an increased influence of skeletal organisms on the construction of microbial dominant reefs which preceded the middle to late ordovician expansion of skeletal dominant reefs skeletal frameworks of early ordovician reefs built by stromatoporoids bryozoans pelmatozoans and calathiids have recently been reported in this study we document the occurrence of localized archaeoscyphia frameworks and additional unidentified non anthaspidellid spiculate sponges that played diverse roles in the construction of microbial siliceous sponge reefs preserved in the early ordovician dumugol formation korea which have not been previously described in coeval reefs elsewhere two types of boundstone textures are recognized microbial dominated boundstone and sponge microbial boundstone microbialites were primarily responsible for reef construction making up about one third of reefs both as framework builders and as encrusters of other reef components the archaeoscyphia and spiculate sponges contributed in various ways to reef development archaeoscyphia constituting about one fourth of the dumugol reefs mainly constructed sponge microbial boundstone together with encrusting microbialites clusters of archaeoscyphia individuals sporadically formed centimeter sized sponge framestone 3 of reefs with primary cryptic spaces spiculate sponges 4 of reefs a previously unknown component of early ordovician reefs also played diverse roles such as encrusting other constituents dwelling in cryptic spaces stabilizing reef flank sediments and even building frameworks such framework building siliceous sponges together with previously reported skeletal frameworks in other early ordovician reefs reflect an early phase of the transition from microbial to skeletal dominated reefs in the early paleozoic

a 1 0 myr record of glacial north atlantic intermediate water variability from odp site 982 in the northeast atlantic changes in the intermediate water structure of the north atlantic were reconstructed using benthic foraminiferal 13c at ocean drilling program odp site 982 for the past 1 0 myr during most terminations of the late pleistocene melting of icebergs and low salinity surface waters caused production of glacial north atlantic intermediate water to cease resulting in decreased ventilation of the middepth north atlantic poor ventilation of intermediate water masses lasted well into some interglacial stages until upper north atlantic deep water nadw production resumed under full interglacial conditions the magnitude of benthic 13c minima and ice rafted debris maxima at terminations at site 982 generally match the degree of glacial suppression of nadw inferred from site 607 these processes may be related and controlled by the spatial and seasonal extent of sea ice cover during glaciations in the nordic seas

alternative modes of quaternary pelagic biosiliceous and carbonate sedimentation a perspective from the east sea japan sea abstract six piston cores 95pc 1 mb97pc 19 ty99 pc18 95pc 3 95pc 4 and 96ebp 4 from the east sea japan sea were examined to assess the fluctuations in carbonate and biogenic silica sedimentation data from four of these cores 95pc 1 mb97pc 19 ty99 pc18 and 96ebp 4 collected from depths above the present carbonate compensation depth ccd clearly show that carbonate content increased during glacial periods and decreased during interglacial periods whereas biogenic silica content shows the opposite pattern the two cores collected below the ccd also show glacial interglacial variations in carbonate and biogenic opal contents with patterns similar to the cores collected above the ccd this study provides strong evidence for cyclic variations of biogenic components corresponding to interglacial glacial cycles even though variations in carbonate and opal contents seem to be affected by dissolution and dilution the inverse correlation between carbonate and biogenic silica contents suggests that two mutually exclusive oceanic modes affected the biogenic sedimentation these modes may have resulted from sea level changes that led to water column stratification during glacial low stands and breakdown of water column stratification and consequent active vertical mixing during interglacial high stands

is there a component of pleistocene co2 change associated with carbonate dissolution cycles the only processes which could have decreased atmospheric co2 during glacial climates without appreciably changing the carbon isotope distribution in the sea appear to be 1 dissolved calcium carbonate input to the ocean e g coral reef buildup and erosion 2 the ocean solubility pump due to changes in surface temperature or air sea exchange or 3 decreased biological production of calcium carbonate it is assumed here that one of these mechanisms caused part of the atmospheric co2 changes recorded in the 200 kyr long vostok ice core two residual co2 records are generated by scaling the 13c difference between planktonic and benthic foraminifera in marine sediment cores to 82 ppm co2 per 1 increase in 13c and subtracting from this the measured co2 concentration in the ice core both residual co2 records exhibit two broad maximums between about 20 50 ka and 140 200 ka indicating that during these times about 40 ppm of the co2 decrease from interglacial levels cannot be explained by the interaction of the ocean s biological and vertical mixing cycles the shape of the residual co2 curve is similar qualitatively to the variation of calcium carbonate in central equatorial pacific sediments during this time period which would imply that changes in dissolved carbonate input to the ocean contributed the added component of co2 change however recent models of atmospheric co2 change in response to changing alkaline input to the ocean exhibit about a 25 to 35 ppm decrease per 1013 mol yr 1 increase in dissolved caco3 input if compensation for the changing input is occurring mostly within an area of about 40 106 km below the lysocline in the indo pacific the change in carbonate accumulation rate corresponding to a 40 ppm co2 change would be a minimum of 3 mg cm 2 yr 1 this can be compared to glacial increases of 0 5 to 1 0 mg cm 2 yr 1 during the last 200 kyr in central equatorial pacific sediments thus the added glacial accumulation of carbonate does not seem to match quantitatively with the 40 ppm amplitude of the residual co2 signal leading one to suspect that solubility plays a greater role than expected on the basis of a 2 c cooler surface ocean

multiple late quaternary episodes of exceptional diatom production in the gulf of alaska abstract hole 887b of the ocean drilling program odp comprises a 44 m 750 kyr long continuous section recovered from the patton murray rise an elevated plateau that is largely isolated from turbidite deposition the patton murray area is centered under the alaska gyre a region characterized by the domal upwelling of nutrient rich waters marked increases in productivity and rapid settling of biogenic matter are suggested throughout the section by the episodic accumulation of diatomaceous oozes up to 1 m thick that are accompanied by barium enrichments significant 13corg maxima in the major diatomaceous bands suggest that mixed layer co2 aq may have been drawn down significantly during some of the productivity events the episodes of enhanced productivity at site 887 occur synchronously with short lived minima in planktonic foram 18o suggesting a direct link to low salinity or less likely warming events in the gulf of alaska there is no obvious explanation for the events but they may be related to seasonal incursions of meltwater from alaska we speculate that episodic input of meltwater or dust borne iron from asian or alaskan sources may have promoted the extraordinary diatom production events recorded in the sedimentary record

microparticle concentration variations linked with climatic change evidence from polar ice cores the microparticle concentrations in three deep ice cores reveal a substantial increase in the concentration of insoluble particles in the global atmosphere during the latter part of the last major glaciation the ratio of the average particle concentration in the late glacial strata to that in the holocene strata is 6 1 for the core from dome c antarctica 3 1 for the core from byrd station antarctica and 12 1 for the core from camp century greenland whether this temporal correlation between increased atmospheric particle load and the lower surface temperatures is directly causal is unknown however the variations in these two parameters must be satisfactorily resolved in any successful hypothesis that addresses the causes of climatic change

sr isotopic and elemental characteristics of calcites in the chinese deserts implications for eolian sr transport and seawater sr evolution abstract calcite content sr concentrations and isotopes of calcites in the chinese deserts are systematically studied in this paper calcite contents which are calculated according to acid soluble ca contents in the deserts are generally higher in the sandy deserts than in the sandy lands and decrease roughly from northwest to northeast of china acid soluble sr is well correlated with calcite in the chinese deserts implying acid soluble sr comes mainly from the calcite dissolution sr concentrations in calcites calculated on the basis of calcite contents and acid soluble sr concentrations in the deserts have an inverse relation to calcite contents essentially mirroring the degree of sr substitution for ca in the calcite development desert calcites have regional variations in sr isotopic ratios calcite sr isotopic ratios depend on geological settings and chemical weathering the badain jaran and tengger deserts are probably affected by additional factors such as the remote groundwater cycle or overturning of underlying sand deposits only four deserts taklimakan qaidam badain jaran and tengger appear to be potential sources of eolian deposits in the chinese loess plateau clp isotopic signatures of calcite sr and silicate nd further indicate that the tengger desert was not an important source for eolian deposits in the clp eolian calcite was probably enriched due to wind sorting from the potential sources to the clp and suffered weathering leaching after it accumulated in the clp sr isotopic compositions and ca sr molar ratios of calcites are different between the deserts and the lingtai profile due to the integrated effect of wind sorting and weathering leaching it is essential to calculate accurately the 87sr 86sr ratio and sr concentration of eolian calcite entering the oceans according to geochemical data of the chinese deserts because of the importance of the chinese deserts in the global dust cycle the calculated sr concentration and 87sr 86sr ratio of eolian calcite entering the north pacific ocean are 11 75 mol g and 0 71032 respectively the calculated values in this study are close to the recommended values by jacobson jacobson a d 2004 has the atmospheric supply of dissolved calcite dust to seawater influenced the evolution of marine 87sr 86sr ratios over the past 2 5 million years geochem geophys geosyst 5 12 1 9 q12002 doi 10 1029 2004gc000750 using the same model as that of jacobson 2004 the effect of asia dust on the evolution of seawater sr isotopes is evaluated 87sr 86sr seawater increases by 0 3 10 5 if the lower dust flux of 2 34 108 mol sr yr is used in the model suggesting the little effect of asian dust on the seawater sr record in the quaternary the increase in 87sr 86sr seawater is 1 5 10 5 if the higher value of 1 17 109 mol sr yr is used as observed in the quaternary sr record these results further support the suggestions of jacobson 2004

lower cambrian cavity dwelling endolithic boring sponges in the lower cambrian forteau formation middle bonnia olenellus zone of southern labrador cavities in archaeocyath patch reefs contain preserved coelobiontic endolithic sponges scallops and carbonate chips produced by sponge boring spicules and preserved endolithic sponge body fossils all point to the presence of endolithic sponges in lower cambrian reef cavities the oldest previously described endolithic sponges are early ordovician in age and the oldest previously known reef interior bioerosion is middle ordovician in age the presence of endolithic sponges in reef cavities of the forteau formation therefore extends both the record of endolithic sponges and of reef interior bioerosion from the ordovician to the upper lower cambrian

a study of variations in the horizontal to vertical lg amplitude ratio in the eastern united states abstract three component short period data on lg in the eastern united states show unusually large regional variations in the average value of the ratio of the largest horizontal h to the largest vertical z component of ground motion this ratio is found to have a value of about 3 or larger for most sites in the central platform and the coastal plains regions and less than 2 for the hard rock sites in the appalachian mountains region large values of h z in the region of coastal plains sediments can be explained as being due to the presence of low velocity overburden but such an explanation is probably not valid for sites in the central platform region large variations in h z from one site to another are of special importance in earthquake engineering since most damage to structures is generally caused by the horizontal components of ground motion

chronostratigraphy and paleoceanography of a piston core ebp 3 from the south korea plateau in the east sea japan sea abstract a piston core ebp 3 collected from the south korea plateau in the east sea japan sea preserved typical alternations of thick dark laminated mud layers and bioturbated hemipelagic mud layers but included several intercalated volcanic lapilli layers the age estimate of core ebp 3 was aided by correlation of biostratigraphic radiolarian data the abundance of microfossils warm water radiolarians and geochemical properties caco 3 with the proxies of the well dated core md01 2407 obtained from the oki ridge a part from the marine isotope stage mis 11 to mis 9 in the middle of core ebp 3 was missing presumably because of erosion following the abrupt deposition of a volcanic lapilli layer despite some uncertainty the age estimate of core ebp 3 revealed that the lower part of core ebp 3 represents mis 13 as was also evident from a comparison with the oxygen isotope stratigraphy downcore biogenic opal and caco 3 variations in core ebp 3 exhibited less distinct orbital scale cyclic changes than cores from other areas in the east sea japan sea however differences in features were discernible between mis 2 and mis 12 in terms of their lithology and caco 3 constituent although both periods were characterized by relatively high levels of caco 3 about 30 for mis 2 and about 50 for mis 12 mis 2 preserved a typical thick dark laminated mud layer whereas mis 12 preserved a distinctly light mud layer with thin parallel laminations this difference of the lithologic facies between mis 2 and mis 12 highlighted a discrepancy among the major constituents indicating that planktonic foraminifera were dominant in mis 2 whereas coccolithophores were dominant in mis 12 our results suggest that the thinly laminated light mud layer which is characterized by a high caco 3 content primarily composed of coccolithophores in mis 12 can be used as a reliable time marker for the establishment of chronostratigraphy in the east sea

asian provenance of glacial dust stage 2 in the greenland ice sheet project 2 ice core summit greenland samples of dust from the greenland ice sheet project 2 gisp2 ice core summit greenland dated within marine isotope stage 2 between 23 340 and 26 180 calendar years b p around the time of the coldest local last glacial temperatures have been analyzed to determine their provenance to accomplish this we have compared them with approximately coeval aeolian sediments mostly loesses sampled in possible source areas psas from around the northern hemisphere the 5 m grain size fraction of these samples was analyzed on the basis that it corresponds to the atmospheric dust component of that time and locale which was sufficiently fine grained to be transported over long distances on the basis of comparison of the clay mineralogy and sr nd and pb isotope composition with ice dust and psas and assuming that we have sampled the most important psas we have determined that the probable source area of these gisp2 dusts was in eastern asia the dust was not derived from either the midcontinental united states or the sahara two more proximal areas that have been suggested as potential sources based on atmospheric circulation modeling except for a brief period during an interstadial when dust transport was exceptionally low for glacial times and had a mineralogical composition indicative of a slightly more southern provenance the source area of the dust did not change significantly during times of variably higher fluxes of dust with larger mean grain size or lower fluxes of dust with smaller mean grain size this includes the high dust period that correlates with the heinrich 2 period of major iceberg discharge into the north atlantic variable wind strengths must therefore be invoked to account for these abrupt and significant changes in dust flux and grain size

fe speciation and fe al ratio in the sediments of southeastern arabian sea as an indicator of climate change aluminum titanium and iron are the major lithogeneous contributors to the marine sediment and their abundance varies strikingly with the intensity of monsoonal precipitation al and ti concentration in a sediment core sk 129 gc 05 from southeastern arabian sea exhibit very strong positive correlation r 0 92 n 140 suggesting their lithogenous association whereas ti and fe does not correlate so strongly r 0 44 this suggests that part of fe is present as structurally unsupported and is evident by two fold increased fe al ratio 0 87 average compared to upper continental crust 0 44 the presence of structurally unsupported fe is confirmed by the sequential leaching of fe which is associated with different fractions such as exchangeable 0 98 carbonate 1 98 fe mn oxide 30 8 organic carbon 4 7 and biogenic opal 11 4 which together constitutes nearly 50 of the bulk fe content there is a good correlation between time series fe al and differential solar insolation suggesting warmer and humid climatic condition resulting intense weathering of hinterland rocks associated with increased monsoonal precipitation probably decoupled soluble fe and its transportation to southeastern arabian sea

different nature of glacial caco3 constituents between mis 2 and mis 12 in the east sea japan sea and its paleoceanographic implication two piston cores pc 05 and pc 08 were collected on the yamato rise in the east sea japan sea during the kr07 12 cruise both cores showed typical alternations of light high l and dark low l layers which are characteristic in the hemi pelagic sediment deposited in the deep part of the east sea japan sea a composite core was achieved with the successful replacement of almost half of the upper part of core pc 05 by the entirety of core pc 08 based on the co equivalence of l values and the dark layers because an interval 170 cm 410 cm of core pc 05 was considerably disturbed due to fluidization during the core execution chronostratigraphy of the composite core was constructed by the direct comparison of l values to the well dated core md01 2407 that was obtained in the oki ridge the lower bottom of the composite core extended to marine isotope stage mis 14 based on the age estimate by lr04 stacks downcore opal variation of the composite core exhibited the distinct orbital scale cyclic changes high during the interglacial and low during the glacial periods however downcore caco3 variation showed no corresponding orbital scale cyclic change between glacial and interglacial periods some intervals of both periods were high in caco3 content frequent and large fluctuations in caco3 content seemed to be more related to the presence of dark layers containing thin lamination tl within the glacial and interglacial intervals it is worthy to note that mis 2 and mis 12 are characterized by distinctly high caco3 content showing up to 18 and 73 respectively among the glacial periods furthermore in terms of lithology mis 2 was characterized by a thick dark layer low l values with tl whereas mis 12 preserved the distinctly light layer high l values with parallel laminations another remarkable dissimilarity between mis 2 and mis 12 was the nature of their caco3 constituent the caco3 constituent of mis 2 consisted of mostly planktonic foraminifera whereas that of mis 12 was mostly dump of coccolithophorids regardless the presence of planktonic foraminifera the distinctness of the caco3 constituents between mis 2 and mis 12 indicates that the preservation of caco3 contents was different temporarily during the glacial periods in the east sea japan sea enhanced caco3 preservation in mis 2 is attributed primarily to less dissolution during the sinking through the water column or at the seafloor but increased caco3 preservation in mis 12 is mainly due to the high primary production in the surface water with respect to the different function of the biological pump which controls co2 cycles the east sea japan sea clearly experienced carbonate ocean like state during mis 12 despite normally silica ocean like state

palaeoclimatic records of the loess palaeosol sequences of the chinese loess plateau whether during past climate stages or into a progressively warming world changes in precipitation constitute a key component of climatic change quantitative proxies for palaeo precipitation are relatively rare the magnetic properties of the windblown loess units and interbedded palaeosols of the famous chinese loess plateau provide key palaeo precipitation data for this populous monsoon dominated region the loess palaeosol sediments record rainfall totals directly complementing the oxygen isotope records of chinese speleothems these isotopic records predominantly reflect moisture source and hence large scale atmospheric circulation changes the two major asian monsoon systems appear to display antiphase behaviour dominance of the indian summer monsoon system seems associated with minimum precession maximum northern hemisphere summer heating dominance of the east asian summer monsoons with maximum precession at 2 8 ma more intense development of the east asian winter monsoon initiated major increases in dust deposition rates and formation of relatively unweathered loess layers glacial stage loess units then interleaved with interglacial interstadial stage palaeosols throughout the quaternary period decoupling of the loess palaeosol rainfall records from the chinese cave records of moisture source shows that the indian and east asian monsoon winds were continuously driven by precessional forcing while summer monsoonal rainfall was greatly suppressed during cool glacial stages the timing of these east asian climatic transitions the subsequent intensification of northern hemisphere glaciations and the association between monsoon circulation changes and north atlantic temperatures indicates a possibly leading global role for these monsoonal changes via alterations in the poleward distribution of heat and moisture

late quaternary terrestrial climatic variability recorded in deep sea turbidites along the toyama deep sea channel central japan sea abstract stratigraphic variations of coarse fraction and frequency and thickness of turbidites in three cores collected along the toyama deep sea channel tdsc in the central japan sea show consistent temporal trends with changes in terrestrial climatic records these temporal changes in turbidite deposition may reflect climatic forcing in the sediment source areas for the last 70 ka comparison of temporal changes in turbidite deposition with paleoclimatic and paleoceanographic records in the central japanese mainland and the japan sea revealed the following modes of climatic linkages 1 during the stadials and interstadials of the last glacial period 70 22 ka when the tsushima warm current twc periodically flowed into the japan sea the japanese mainland climate was cold and periodically wet resulting in occasional glacial advances in adjacent mountains turbidite flux increased in the tdsc system during the major glacial advances because of the increased production of coarse debris by glacial processes and high transport potential due to high precipitation 2 during the last glacial maximum 22 18 ka when the japan sea was capped by cold low salinity surface water the terrestrial climate was cold and dry due to low evaporation from the japan sea as a result of low precipitation less coarse debris was transported into deep basins and so during this period the turbidite flux along the tdsc was reduced 3 during the last deglaciation 18 8 ka precipitation in central japan increased due to intensified summer monsoons this resulted in destabilization of mountain slopes and increased transport of detritus to the lowlands and also to the tdsc system 4 after the twc flowed into the japan sea the land climate became warm wet and stable enhanced vegetation and re stabilized mountain slopes have reduced sediment input to the tdsc system since 8 ka

influences of oceanic rheostats and amplifiers on atmospheric co2 content during the late quaternary abstract although a clear explanation has yet to emerge for the observed decline in atmospheric co2 content during glacial episodes numerous hypotheses have been offered selected examples are reviewed or evaluated here a strengthened biological pump resulting from intensified upwelling at low latitudes was suggested early on as a likely direct cause of the glacial co2 drawdown two problems have since arisen with this hypothesis first on some upwelling continental margins for example off california oregon northwestern mexico peru and parts of nw africa organic matter accumulation decreased in some areas markedly during the last glacial maximum lgm second upwelled cool co2 rich water degasses carbon dioxide in warm regions and for a key area such as the modern equatorial pacific to become a net sink for atmospheric co2 rather than a source as it is today the rate of downward organic carbon export must exceed the rate of degassing recent sedimentary carbon and nitrogen isotopic data suggest however that the equatorial pacific has remained a strong co2 source for at least the last 40 000 yr and probably much longer although the direct extraction of carbon from surface waters and burial in the sediments in productive regions now appears unlikely to provide the sought for explanation indirect effects related to export productivity may hold the key these can modulate the chemical character of the ocean so as to increase its uptake of co2 a rheostat effect or they could increase indirectly the nutrient inventory of the sea an amplifier effect for example it is now recognized that denitrification was greatly reduced during glacial maxima in all three principal oxygen minimum zones in the oceans i e the subtropical north and south pacific and the arabian sea the implication is that nitrate the limiting nutrient in the modern ocean must have been more abundant during glacial periods and that this surfeit would have supported increased export production in the meso or oligotrophic areas that are today nitrate limited dust may represent another rheostat increases in atmospheric turbidity during glacials are clearly recorded by ice and marine sediment cores in both hemispheres in addition to fostering enhanced export production by adding needed iron to nitrate rich areas it has been suggested recently that increased dust inputs to nitrate depleted regions during glacials might have encouraged growth of iron hungry n2 fixing cyanobacteria thus alleviating nitrate limitation no sedimentary 15 n data yet exist to support this hypothesis but it remains viable finally regional changes in physical hydrography may have played a major and hitherto underestimated role for example in the glacial southern ocean south of the polar front recent nitrogen isotope and other data imply that the upper water column was well stratified during the lgm by limiting upwelling this would have reduced the ocean atmosphere co2 leak in the area this could have made a significant contribution to the pco2 drawdown

changes in ph in the eastern equatorial pacific across stage 5 6 boundary based on boron isotopes in foraminifera estimates of paleo ph for the eastern equatorial pacific ocean across the oxygen isotopic stage 5 6 boundary have been made based on the boron isotopic composition of planktonic orbulina universa and benthic mixed species foraminifera from core v19 28 the estimated deep ocean ph during the penultimate glacial period was about 0 3 0 1 ph units higher compared to the modern deep ocean this is consistent with previously estimated deep ocean ph changes across the stage l 2 boundary in the western equatorial pacific and tropical atlantic thus arguing against the possibility that the benthic foraminifera analyzed to estimate deep ocean ph changes have been significantly affected by anomalous local environment and or diagenesis the estimated changes in the deep ocean carbonate chemistry require a decoupling of several kilometers between the saturation horizon and the lysocline during the glacial periods though such a decoupling could be achieved by enhanced respiration co2 driven calcite dissolution in sediments during glacial periods it lacks support from the calcite sedimentary records the boron isotopic compositions of planktonic foraminifera on the other hand indicate no significant ph change in the eastern equatorial pacific surface ocean during the glacial interglacial transition this is inconsistent with an expected higher surface ocean ph during the glacial period due to lower atmospheric pco2 and is also in contrast with the previously estimated boron isotope based glacial interglacial ph change of 0 2 0 1 ph units in the western equatorial pacific and tropical atlantic the lack of change in eastern equatorial pacific surface ocean ph between glacial interglacial periods could be attributed to less nutrient utilization efficiency and or enhanced calcite production during glacial periods such a decrease in nutrient utilization efficiency and or increase in calcite production would lead to a greater disequilibrium between the pco2 of eastern equatorial pacific surface ocean and that of the atmosphere making this part of the ocean a greater source of co2 to the atmosphere during glacial periods compared to today

global deep sea burial rate of calcium carbonate during the last glacial maximum global databases concentrations rates in holocene and last glacial of calcium carbonate and mass accumulation maximum sediments were used to estimate the deep sea sedimentary calcium carbonate burial rate during these two time intervals sparse calcite mass accumulation rate data were extrapolated across regions of varying calcium carbonate concentration using a gridded map of calcium carbonate concentrations and the assumption that accumulation of noncarbonate material is uncorrelated with calcite concentration within some geographical region mean noncarbonate accumulation rates were estimated within each of nine regions determined by the distribution and nature of the accumulation rate data for core top sediments data coverage 67 of the high calcite the regions of reasonable encompass 75 sediments globally and within these regions we estimate an accumulation rate of 55 9 3 6x1011 mol yr 1 the same regions cover 48 of glacial high caco3 sediments the smaller fraction is due to a shift of calcite deposition to the poorly sampled south pacific and total 44 1 6 0x1011 mol yr 1 projecting to 100 coverage south and total 44 1 6 0x1011 both estimates yields accumulation estimates of 8 3x1012 mol yr 1 today and 9 2x1012 mol yr 1 during glacial time this is little better than a guess given the incomplete data coverage but it suggests that glacial deep sea calcite burial rate was probably not considerably faster than today in spite of a presumed decreasein shallow water burial during glacial time

preservation of siliceous sponges in the jurassic of southern england and northern france reef forming lithistid sponges in the middle jurassic bathonian of normandy france were lithified on the sea floor by a peloidal cement probably of an original low mg calcite composition precipitated under bacterial influence this early lithification permitted early dissolution of the siliceous skeleton without the collapse or distortion of the resulting moulds these moulds were encrusted and bored this pathway for the fossilization of sponges is shown by other examples of jurassic lithistids and is likely to be widely applicable throughout the fossil record particularly at times during which calcite was the primary marine precipitate

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

isotopic composition and morphology of living globorotalia scitula a new proxy of sub intermediate ocean carbonate chemistry abundance isotopic composition and morphological imprints of the planktonic foraminifera globorotalia scitula brady were closely examined for possible use as a novel reconstruction tool of chemical environments in sub intermediate depth seawater in the past based on the mocnes plankton tow observation of dwelling depths of g scitula and the isotopic compositions together with hydrochemistry data the empirical relations between isotopic disequilibria in carbon 13c 13cg scitula 13cdic and oxygen 18o 18og scitula 18ow isotopes in the carbonate tests and the seawater 18o and 13c of dissolved inorganic carbon dic respectively are introduced the morphological information such as pore density and porosity is also examined for significant relations to carbonate chemistry shell porosity is strongly correlated saturation state of calcite the dissolution of living g scitula tests may promote the observed isotopic differences as well as the increases in porosity 18o of g scitula is found effectively to be linear function of both water temperature and calcite saturation state and thereby temperature equation for g scitula is provided while 13c of g scitula is a linear function of only calcite saturation state the equation was validated by using globorotalia scitula collected by a sediment trap in intermediate water depths satisfactory agreements were found between observed and calculated 18o from the empirical equations based on temperature and hydrochemistry data at sediment trap deployment site indicating that the equation may be useful in paleo environmental reconstruction of sub intermediate water the sediment trap observation further suggests that the abundance of g scitula does not necessarily correspond to surface water productivity and to poc flux but instead it correlates well with the supply of fine organic matter which appears to be a result of water convection thus g scitula may be an unambiguous and excellent paleo environmental recorder for carbonate chemistry and for fine organic matter transport to the depths if isotopic and morphological observations are combined