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

neogene tectonic rotation of the santa ynez range western transverse ranges california suggested by paleomagnetic investigation of the monterey formation a paleomagnetic investigation was conducted on dolomite beds in the middle and upper miocene monterey formation in order to determine the timing and amount of post early miocene tectonic rotation experienced by the santa ynez range part of the western transverse ranges province of california five stratigraphic sections of the monterey formation exposed along the coastline west of santa barbara were extensively sampled the sections were correlated using tuff beds and ages were assigned to each dolomite bed on the basis of magnetostratigraphy and diatom biostratigraphy the dolomite beds possess stable primary remanent magnetic directions which pass fold tests and reversal tests and show a consistent decrease in magnetic declination with decreasing age rocks 14 8 to 15 8 m y old have a mean magnetic declination of 92 7 whereas rocks 8 to 11 m y old have a mean magnetic declination of 36 7 the consistent upsection decrease in magnetic declination within these stratigraphic sections is attributed to a rapid 56 10 clockwise rotation of the entire santa ynez range between 15 2 0 1 and 10 1 m y b p the mean magnetic declination of 36 7 in rocks 8 to 11 m y old is probably due to continued clockwise rotation of the santa ynez range during the plio pleistocene an early miocene palinspastic reconstruction is proposed in which the area of the presently east west trending santa ynez range is restored to an initially north south orientation

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

constraining pathways of microbial mediation for carbonate concretions of the miocene monterey formation using carbonate associated sulfate abstract carbonate concretions can form as a result of organic matter degradation within sediments however the ability to determine specific processes and timing relationships to particular concretions has remained elusive previously employed proxies e g carbon and oxygen isotopes cannot uniquely distinguish among diagenetic alkalinity sources generated by microbial oxidation of organic matter using oxygen nitrate metal oxides and sulfate as electron acceptors in addition to degradation by thermal decarboxylation here we employ concentrations of carbonate associated sulfate cas and 34scas along with more traditional approaches to determine the specific nature of concretion authigenesis within the miocene monterey formation integrated geochemical analyses reveal that at least three specific organo diagenetic reaction pathways can be tied to concretion formation and that these reactions are largely sample site specific one calcitic concretion from the phosphatic shale member at naples beach yields 34scas values near miocene seawater sulfate 22 vcdt abundant cas ca 1000 ppm depleted 13ccarb 11 vpdb and very low concentrations of fe ca 700 ppm and mn ca 15 ppm characteristics most consistent with shallow formation in association with organic matter degradation by nitrate iron oxides and or minor sulfate reduction cemented concretionary layers of the phosphatic shale member at shell beach display elevated 34scas up to 37 cas concentrations of 600 ppm mildly depleted 13ccarb 6 moderate amounts of mn ca 250 ppm and relatively low fe ca 1700 ppm indicative of formation in sediments dominated by sulfate reduction finally concretions within a siliceous host at montana de oro and naples beach show minimal cas concentrations positive 13c values and the highest concentrations of fe ca 11 300 ppm and mn ca 440 ppm consistent with formation in sediments experiencing methanogenesis in a highly reducing environment this study highlights the promise in combining cas analysis with more traditional techniques to differentiate among diagenetic reactions as preserved in the geologic record and shows potential for unraveling subsurface biospheric processes in ancient samples with a high degree of specificity

the impact of hydrodynamics authigenesis and basin morphology on sediment accumulation in an upwelling environment the miocene monterey formation at shell beach and mussel rock pismo and santa maria basins central california u s a abstract in the sections at shell beach pismo basin and mussel rock santa maria basin both along the central california coast the miocene monterey formation is composed of laminated biosiliceous organic rich and phosphate rich sediments which are intercalated with carbonates and volcanogenic deposits the presence of small and large scale scours conglomerates gravity flow deposits slumps and condensed intervals reveals the importance of sediment reworking which is related to the presence of bottom currents the general morphology of the basins and recurrent high energy events of likely seismic origin the lithologies reflect strong upwelling enhanced primary productivity and the presence of an oxygen minimum zone which is indicated by ubiquitous lamination a general absence of bioturbation with the rare exception of traces related to the gravity flow displacement of trace makers high pyrite mo and u concentrations and molar ratios of total organic carbon and organic phosphorus toc p org of up to 2000 oxygen depletion was particularly severe during the early langhian and the late serravallian and early tortonian and favored the preservation of organic matter episodes of deposition of organic rich sediment were followed by longer phases of subdued sediment accumulation and early diagenetic phosphogenesis which resulted in the formation of a low porosity less permeable lid in the near surface sediments that assisted in preserving organic matter phosphogenesis occurred throughout the time interval considered approximately 17 5 6 5 ma and phosphate rich sediments formed especially during periods of sedimentary condensation in the langhian and earliest serravallian and the latest tortonian and early messinian a comparison of temporal trends in the type and quantity of deposited sediments between the two sections at shell beach and mussel rock and three sections of the santa barbara basin el capitan state beach naples beach and haskell beach confirms that towards the top of the monterey formation sediments become enriched in biosilica in all three basins the transition into this lithology occurred diachronously during the serravallian in the pismo and santa maria basins and tortonian in the santa barbara basin and was probably related to a diachronous shift to more intense upwelling in all three basins a phase of important condensation and phosphogenesis terminated monterey type sedimentation during the latest tortonian and early messinian in both the santa maria and santa barbara basins the uniform expression of this phase is interpreted as the result of improved connections between the two basins

reconstructing in situ vegetation dynamics using carbon isotopic composition of biopolymeric residues in the central chinese loess plateau abstract carbon isotopic compositions of total organic carbon toc or leaf waxes in soils have been used to reconstruct past changes in the relative abundance of c 3 and c 4 plants however toc contains organic matter of different source organisms plants animals fungi bacteria etc and its isotopic ratios could be modified during diagenesis since different organic fractions e g carbohydrates proteins lipids etc have different isotopic ratios and degradation rates leaf waxes on the other hand are transported by wind and hence represent vegetation input from a large geographic area we report in this paper a new approach to extract in situ paleovegetation information from late quaternary paleosols by determining carbon isotopic compositions of biomarkers derived from aliphatic bio and geopolymers of plant origin we show that c 9 to c 17 n alkenes derived from aliphatic bio and geopolymers are the dominant compounds released by flash pyrolysis of insoluble organic matter isolated from the late quaternary paleosols in the chinese loess plateau because the aliphatic polymeric substances are mainly derived from plant leaves bark and roots the isotopic signatures of these alkenes determined using pyrolysis gas chromatography isotopic ratio mass spectrometry reflect in situ vegetation changes our down core 13 c data from the xifeng loess paleosol profile show significant coherence among biopolymer derived n alkenes leaf wax n alkanes and toc for the past 40 kyr however the different amplitudes of the temporal isotopic changes among these data sets are indicative of variability in in situ and regional vegetation dynamics organic sources and effect of diagenesis our data also imply that below ground biomass is a major source of soil organic matter in the central china loess sediment

carbon isotopic compositions of long chain n alkanes in the japan sea sediments implications for paleoenvironmental changes over the past 85 kyr abstract carbon isotopic compositions of long chain n alkanes in cores kh 79 3 c 3 and l 3 taken from the oki ridge 37 04 n 134 42 e water depth 935 m in the japan sea were measured by gas chromatography isotope ratio mass spectrometry fluctuations in the carbon isotopic composition of terrestrially derived material as determined from 13 c n alkane weighted average of 13 c values for higher plant derived n c29 and n c31 alkanes range from 29 1 to 32 1 for the past 85 kyr in core kh 79 3 c 3 13 c n alkane values in colder climates 18 o stages 2 and 4 are depleted in 13 c by approximately 1 relative to those in warmer climates stages 1 3 and 5 1 this suggests that the temporal variations of the 13 c values for higher plant derived n alkanes exhibit a close relationship with glacial interglacial cycles the results over the past 30 kyr 14 c age reveal that the 13 c n alkane values shifted abruptly from 31 1 0 5 to 29 9 0 4 at around 10 kyr b p with the isotopic values remaining relatively constant thereafter this positive 1 2 shift in 13 c n alkane values can be attributed to one or both of the following factors i enhancement of primary productivity on land and ii change in vegetational types e g c4 c3 plants ratios and or changes in the species of c3 plants

multiple expansions of c4 plant biomass in east asia since 7 ma coupled with strengthened monsoon circulation the expansion of plants using the c4 photosynthetic pathway is one of the most prominent changes in the global ecosystem during the cenozoic era a significant late miocene expansion is well documented however the existence and cause of subsequent expansions are still not clear owing in part to the lack of long continuous climate vegetation records here we present two high resolution carbon isotope time series covering the past 7 m y derived from eolian deposits on the chinese loess plateau the data indicate three intervals of significant c4 plant expansions within the semiarid monsoonal region of east asia ca 2 9 2 7 ma 1 3 0 9 ma and 0 6 ma present these expansions covary with strengthened east asian summer monsoon circulation we conclude that in east asia large scale late miocene c4 c3 vegetation changes in semiarid areas have been primarily driven by warm seasonal precipitation and temperature variations associated with changes in monsoon circulation

climate change in southern illinois usa based on the age and δ13c of organic matter in cave sediments abstract matrix supported diamicton and uniform to laminated silty fine grained sediment deposited from about 42 500 to 27 600 cal yr b p under slackwater conditions nearly filled two caves in southwestern illinois at some point most of the sediment was flushed from the caves and from about 22 700 to 4000 cal yr b p floods deposited a drape of sandy and silty sediment on remnant slackwater successions cobbly alluvium and bedrock especially from 7700 to 4000 cal yr b p clay mineral analyses of the slackwater cave sediment reveal a provenance of chiefly petersburg silt a smectite and illite rich proglacial lacustrine unit present in the overlying illinois episode glacial succession today remnants of the ancient subterranean slackwater deposits nearly fill several secondary passages and in at least two locations cover a cobble mantled strath terrace 1 3 to 1 5 m above active stream channels slumping and sinkhole formation appear to have been important mechanisms for deposition of the ancient subterranean deposits slumping of these surficial deposits and associated vegetation can occur along the flanks of sinkholes in addition to sinkhole formation and enter caves however the finer organics some of them comminuted during transport into the caves become part of the cave alluvium this finer organic fraction is the modern analog of the humified organic matter disseminated in slackwater sediment dated in this investigation by radiocarbon methods twenty four 14c ages on humified organic matter provide chronologic control the 13c values of the organic matter reflect the proportion of c4 type to c3 type vegetation growing in and around swallets and sinkholes at the time of redeposition drought tolerant c4 type vegetation was more prevalent relative to c3 type vegetation from 42 500 to 31 200 cal yr b p compared to conditions from 28 800 cal yr b p to the present the 13c values are consistent with the results from other investigations of speleothems and organic matter from loessial paleosols

the influence of bacterial activity on phosphorite formation in the miocene monterey formation california abstract authigenic phosphorites from the miocene monterey formation california including an autochthonous phosphatic laminite were analyzed for molecular biomarkers element content and sulfur isotopic composition of associated pyrite and sulfate to evaluate the role of bacterial activity in the precipitation of phosphate minerals the phosphorites formed in a depositional environment typified by upwelling with dynamic bottom currents and hardground formation pyrite enclosed in the phosphorites shows 34 s values as low as 36 5 vcdt which is consistent with bacterial sulfate reduction in a three step extraction phosphorite dissolution extraction procedure molecular fossils of sulfate reducing bacteria di o alkyl glycerol ethers and short chain branched fatty acids i and ai c 15 0 i and ai c 17 0 and 10mec 16 0 were preferentially released from the mineral lattice this suggests that the molecular fossils were tightly bound to carbonate fluorapatite indicating that sulfate reducing bacteria were involved in mineral formation a close association of sulfate reducing bacteria with large sulfide oxidizing bacteria which was previously suggested to favor carbonate fluorapatite precipitation could neither be confirmed nor excluded for the miocene monterey formation phosphorites

climatic and environmental controls on the variation of c3 and c4 plant abundances in central florida for the past 62 000 years lake tulane provides one of the few continental sediment records beyond the late glacial period 15 000 cal years b p for eastern north america its continuous organic rich sediment has yielded pollen assemblages that date back 62 000 years here we report the first organic geochemical characterization of the sediment core from lake tulane based on compound specific carbon isotopic analyses of higher plant leaf waxes our millennium resolution carbon isotope data allow us to quantitatively assess the variations in the relative abundances of c3 and c4 plants in central florida under contrasting climate conditions and different atmospheric pco2 levels during the last glacial interglacial cycle specifically our results indicate large changes in the relative abundance of c3 and c4 plants with 40 higher input from c4 plants during the last glacial maximum lgm than during the holocene during the last glacial period c4 plant abundance decreased dramatically during the pine phases when precipitation increased indicating that increasing precipitation overrode the impact of low atmospheric pco2 leading to expansions of c3 plants our results provide new insights on the forcing mechanisms and first quantitative estimates on the c3 and c4 plant variation in central florida for the last 62 000 cal years d 2005 elsevier b v all rights reserved

continental weathering and redox conditions during the early toarcian oceanic anoxic event in the northwestern tethys insight from the posidonia shale section in the swiss jura mountains abstract the geochemistry and mineralogy of organic rich sediments of the rietheim succession in northern switzerland were studied to evaluate the main impacts of the early toarcian oceanic anoxic event t oae 183 ma ago on the depositional environment in the nw tethys ocean the geochemical data obtained notably 13corg 13ccaco3 rock eval pyrolysis toccff support the hypothesis that the negative c isotope excursion at the onset of the t oae mainly reflects a major perturbation in the global carbon cycle rather than local environmental changes e g basinal restriction productivity rock eval pyrolysis and 13corg 15ntotal crossplots indicate that the organic matter was primarily of marine origin during the t oae and deposited in an epicontinental sea setting detrital proxies notably detritus index siliciclastic balance and ln al2o3 na2o suggest that the elevated pco2 levels and greenhouse climate prevailing during the t oae induced significant acceleration of the hydrologic cycle and an increase in continental chemical weathering rates redox sensitive proxies relative pyrite contents organic and sulfide balances v v ni ratios trace elements enrichment factors trace element toc co variation patterns and toc ptotal molar ratios indicate that the rietheim posidonia shale sediments accumulated under oxic to dysoxic bottom water conditions with more reducing conditions during the t oae anoxic and possibly euxinic these changes in redox conditions were probably induced by substantial thermohaline stratification driven by enhanced freshwater input and the recurrent influx of brackish arctic seawater into the nw tethys through the viking corridor in agreement with previous sedimentological and geochemical evidences from the nw tethys ocean in the studied succession such conditions were perhaps also responsible for sequestration of most of the regenerated p in the deeper water column by adsorption and or co precipitation into authigenic phases overall the major palaeoenvironmental changes documented in this study provide a robust example of earth s possible responses to the rapid onset of extreme greenhouse conditions

elemental anomalies at the cretaceous tertiary boundary woodside creek new zealand iridium and 26 other elements were determined in shale from the cretaceous tertiary boundary at the locus classicus for iridium anomalies at woodside creek new zealand iridium gold copper cobalt chromium nickel arsenic molybdenum and iron were enriched in the basal 2 millimeters of the 8 millimeter shale parting as compared with the rest of the stratigraphic column no other shale partings in the column had anomalous concentrations of any element when the data were expressed on a carbonate free basis the boundary material showed striking compositional similarities with the stevns klint danish boundary shale elemental concentrations were in general much higher in the new zealand material than in nonboundary shales from elsewhere in the world the high concentration of iridium 153 nanograms per gram in the basal layer of the boundary together with the enrichment of other siderophile elements supports the idea of an extraterrestrial source for much of the material the iridium gold ratio of 2 1 is also in accordance with such a source the iridium content of the basal layer is higher than for any other marine boundary shale obtained on land the integrated iridium value is 187 nanograms per square centimeter of boundary surface

oxygen isotope record of sea level and climate variations in the sulu sea over the past 150 000 years the sulu sea is located in the warm pool of the western pacific ocean where mean annual temperatures are the highest of anywhere on earth because this large heat source supplies the atmosphere with a significant portion of its water vapour and latent heat understanding the climate history of the region is important for reconstructing global palaeoclimate and for predicting future climate change changes in the oxygen isotope composition of planktonic foraminifera from sulu sea sediments have previously been shown to reflect changes in the planetary ice volume at glacial interglacial and millenial timeseales and such records have been obtained for the late pleistocene epoch and the last deglaciation1 3 here i present results that extend the millenial time resolution record back to 150 000 years before present on timescales of around 10 000 years the sulu sea oxygen isotope record matches changes in sea level deduced from coral terraces on the huon peninsula4 this is particularly the case during isotope stage 3 an interglacial period 23 000 to 58 000 years ago where the sulu sea oxygen isotope record deviates from the specmap deep ocean oxygen isotope record5 thus these results support the idea4 6 that there were higher sea levels and less continental ice during stage 3 than the specmap record implies and that sea level during this interglacial was just 40 50 metres below present levels the subsequent rate of increase in continental ice volume during the return to full glacial conditions was correspondingly faster than previously thought

lower temperature as the main cause of c4 plant declines during the glacial periods on the chinese loess plateau abstract the distribution of c3 and c4 plants changed in regionally contrasting ways during the last glacial period c4 plant expansion in low latitude africa and america coincided with c4 plant decreases in mesoamerica and the us great plains this c4 plant expansion has been attributed to lower pco2 and increased aridity and the decline in c4 plants is believed to have been caused by increased winter precipitation and lower temperatures however it is still difficult to generalize whether pco2 temperature or aridity was mainly responsible for c3 vs c4 vegetation changes during glacial periods paleoclimate conditions on the chinese loess plateau clp offer opportunities to further evaluate the role of temperature in the c3 vs c4 competition detailed climate records have shown that the clp region was drier and colder during glacial periods with aridity favoring c4 expansion and lower temperatures favoring c3 expansion here we present two high resolution compound specific carbon isotope records of n alkanes from the clp as vegetation biomarkers to estimate the relative abundance of c4 plants during the last two glacial interglacial transitions more negative 13c values during the glacial periods from two clp sites clearly show that in contrast with low latitude sites c4 plants declined this decrease in c4 abundance was caused by lower temperature despite the lower pco2 and increased aridity on the clp during glacial time

new chronology and organic matter paleoclimatic significance of nusloch loess sequence rhine valley germany due to its high accumulation rate the loess sequence of nu loch rhine valley germany is well suited to a high resolution study of continental paleoenvironmental changes over the last climatic cycle for northwestern europe as carbon isotope ratios of plants depend on environmental variations c of loess derived organic matter constitute reliable paleoclimatic proxies we present here a new chronology of nu loch loess sequence based on several c and tl dates our data show high correlations with global climate e ects vostok co or semi global gisp2 o and thus o er in this way a new approach to establish accurate chronologies in continental sequences furthermore using a deconvolution of the c signal would provide a quantitative proxy of moisture supply and permit paleoprecipitation reconstructions 2000 elsevier science ltd and inqua all rights reserved

long term vegetation change and controlling factors in donghae area korea over the past 40 000years abstract determining the effect of climate change since the last glacial maximum lgm in the east sea sea of japan coastal region of korea has been difficult owing to a dearth of suitable paleoclimate proxies a 40 000 year carbon isotope 13c record from cave deposits collected from cheongok cave korea reveals both long term change and superimposed shorter term isotopic excursions the 13c value of the sedimentary organic matter a proxy for past vegetation change varied from 25 to 21 with lower values during the lgm and higher values during the holocene a pattern that is generally consistent with trends in total organic carbon content toc and magnetic susceptibility from the lgm to the late holocene the c4 plant abundance mainly grasses estimated using a simple binary mixing model increased from 15 to 45 this long term change resembles trends in biogenic opal production in the east sea sea surface temperature and global sea level more than it does asian summer monsoon strength long term changes in c4 plant abundance in eastern coastal areas of korea over the last 40 000 years were probably affected most strongly by sea level driven ocean circulation changes in the east sea coupled with continental ice volume changes low pco2 during the lgm was not sufficient to cause the expansion of c4 plant coverage without favorable climatic conditions

c4 plant productivity and climate co2 variations in south central texas during the late quaternary abstract a continuous record of organic carbon 13c from a buried soil sequence in south central texas demonstrates 1 strong coupling between marine and adjacent continental ecosystems in the late pleistocene as a result of glacial meltwater entering the gulf of mexico and 2 ecosystem decoupling in the holocene associated with a reduction of meltwater and a shift in global circulation patterns in the late pleistocene reduction in c4 plant productivity correlates with two well documented glacial meltwater pulses 15 000 and 12 000 14c yr b p indicating a cooler than present adjacent continental environment increased c4 production between 11 000 and 10 000 14c yr b p suggests that the younger dryas was a warm interval responding to the diversion of glacial meltwater away from the mississippi river with waning meltwater flow c4 productivity generally increased throughout the holocene culminating in peak warm intervals at 5000 and 2000 14c yr b p shifts in the abundances of c3 c4 plants through the late quaternary show no correlation to ecophysiological responses to atmospheric co2 concentration

δ13c of loess organic matter as a potential proxy for paleoprecipitation paleoprecipitation reconstructions on the basis of pollen are well known but they do not provide high temporal resolution for glacial periods high resolution paleoprecipitation reconstructions for the last glaciation based on the isotopic record organic matter in loess from nussloch rhine valley germany are consistent with paleoprecipitation inferred from peat in the same area using an independant method thus 13c of loess organic matter can be used as a proxy for paleoprecipitation

middle to late miocene stepwise climate cooling evidence from a high resolution deep water isotope curve spanning 8 million years 1 we present high resolution 2 3 kyr benthic foraminiferal stable isotopes in a continuous well preserved sedimentary archive from the west pacific ocean ocean drilling program site 1146 which track climate evolution in unprecedented resolution over the period 12 9 to 8 4 ma we developed an astronomically tuned chronology over this interval and integrated our new records with published isotope data from the same location to reconstruct long term climate and ocean circulation development between 16 4 and 8 4 ma this extended perspective reveals that the long eccentricity 400 kyr cycle is prominently encoded in the 13c signal over most of the record reflecting long term fluctuations in the carbon cycle the 18o signal closely follows variations in short eccentricity 100 kyr and obliquity 41 kyr in particular the obliquity cycle is prominent from 14 6 to 14 1 ma and from 9 8 to 9 2 ma when high amplitude variability in obliquity is congruent with low amplitude variability in short eccentricity the 18o curve is additionally characterized by a series of incremental steps at 14 6 13 9 13 1 10 6 9 9 and 9 0 ma which we attribute to progressive deep water cooling and or glaciation episodes following the end of the miocene climatic optimum on the basis of 18o amplitudes we find that climate variability decreased substantially after 13 ma except for a remarkable warming episode at 10 8 10 7 ma at peak insolation during eccentricity maxima 100 and 400 kyr this transient warming associated with a massive negative carbon isotope shift is reminiscent of intense global warming events at eccentricity maxima during the miocene climatic optimum

the history and variability of the east asian paleomonsoon climate abstract changes in the east asian paleomonsoon reflect interactions between the global atmosphere ocean land and ice systems and are also an expression of their combined effect within the boundary conditions imposed by the east asian continent and solar radiation the history of the east asian monsoon is an alternation between dominance by the dry cold winter and warm humid summer monsoons high resolution eolian sequences preserved in the chinese loess plateau reveal that the east asian monsoon may have commenced at least 7 2 ma ago they also provide evidence indicating that the pulsed uplift of the tibetan plateau at about 3 4 and 7 2 ma may have played an important role in inducing climate change the palaeoclimatic records of the last glacial cycle show high frequency variability on time scales of 1000 year or even shorter and instability of the east asian paleomonsoon system the high frequency variability could be due to a non linear response to orbital forcing or a result of the coupling processes between different components of the global system cold air activity in northern high latitudes the trans equatorial air streams from the southern hemisphere and possibly enso may have played an important role in east asian monsoon variability the synchroneity of all the palaeoclimatic events along the polar equator polar pep transect is still an open question correlation of limited palaeoclimatic records for the last 30 kyr obtained from east asia and australia suggests that the trans equatorial air streams driven by the monsoon and trade winds may have had an influence on opposite hemispheres

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

grain size of quartz as an indicator of winter monsoon strength on the loess plateau of central china during the last 130 000 yr the chinese loess paleosol sequence constitutes an important record of variations in asian monsoon climate over the past 2 4 myr magnetic susceptibility of loess and paleosols has been used as a proxy for summer monsoon intensity while median grain size has been regarded as a measure of the strength of winter monsoon winds that were responsible for most of the dust transport however median grain size is only an approximate index of winter monsoon strength because both paleosols and loess have been modified to various degrees by weathering processes that have produced pedogenic clay the quartz component of loess and paleosols is largely unaffected by weathering processes and therefore constitutes a more reliable proxy index of monsoon wind strength median grain size qmd and maximum grain size qmax values of monomineralic quartz isolated from the loess paleosol section at luochuan in the central loess plateau are characterized by two main intervals during the last ca 130 000 yr when these parameters were significantly greater than 9 and 85 m respectively and three main intervals when they were lower the data imply that the winter monsoon weakened during the intervals with low qmd and qmax values which coincide with marine oxygen isotope stages 5 3 and 1 and was strongest ca 67 000 and 20 000 yr ago during isotope stages 4 and 2 however both quartz grainsize records display second order high frequency high amplitude variations which are lacking in the magnetic susceptibility record that imply rapid and significant changes in atmospheric conditions that affect dust transport and deposition

variations in temperature and salinity of the surface water above the middle okinawa trough during the past 37 kyr abstract east china sea ecs is an important climate modulator of east asia in the last glacial period the global sea level the path and strength of the kuroshio current experienced great changes combined with the variable volume of fresh run off input they made the hydrographic situation in the ecs quite different from nowadays based on high resolution alkenone sea surface temperature sst and oxygen isotope composition of planktonic foraminifera globigerinoides sacculifer we reconstructed paleo sea surface salinity sss of a long piston core dgks9604 retrieved from the middle okinawa trough of the eastern ecs the 18o and sst records display significant variations with global ice volume synchrony of the millennial scale climate events like yd and heinrich events of core dgks9604 to the ice core from the northern high latitudes and the synchroneity of deglacial warming with the bolling allerod warming suggests a strong coupling of the sst variations in the marginal pacific ocean to the climate of the north atlantic most likely through the asian monsoon atmospheric circulation the ecs documents lowest sst 22 c at 26 cal kyr bp and 3 c sst difference between the full glaciation 26 to 19 cal kyr bp and mid to late holocene 6 cal kyr bp present the overall long term hydrographic variations in the middle okinawa trough are controlled by temporal and spatial variations in i the intensity and position of the kuroshio current ii intensity of the asian summer monsoon and iii sea level fluctuations coupled with ecs topography saline surface water dominated over the middle okinawa trough during early pre glaciation 37 to 31 cal kyr bp last deglaciation 19 to 11 6 cal kyr bp and mid to late holocene 6 cal kyr bp present whilst freshened surface water prevailed during the late pre glaciation 31 to 26 cal kyr bp full glaciation 26 to 19 cal kyr bp and early holocene 11 6 to 6 cal kyr bp

high resolution multi proxy climate records from chinese loess evidence for rapid climatic changes over the last 75 kyr the loess paleosol sequence in loess layer l1 malan loess is investigated in three regions of the western chinese loess plateau nine pedogenic layers are found in l1 and three proxy climate indices magnetic susceptibility ms grain size gs and caco3 content are measured at intervals of 0 2 kyr in order to recover records of monsoon climate variations time series of ms gs and caco3 content document the high resolution history of summer and winter monsoon climate variations over the last 75 kyr the records show a high degree of similarity to the warm interstadials recorded in ice cores from greenland and the antarctic and with heinrich events in the north atlantic during the last glacial cycle bond cycles are also recorded by the chinese loess records overall our results indicate that numerous rapid changes in climate occurred in china during the last glacial cycle but that the range of climate variations was smaller than recorded in greenland

summer monsoon intensity controls c4 c3 plant abundance during the last 35 ka in the chinese loess plateau carbon isotope evidence from bulk organic matter and individual leaf waxes the natural abundance of c3 and c4 plants is affected by multiple environmental factors including temperature moisture balance and atmospheric pco2 the relative importance of these factors is a subject of considerable debate and may vary in different natural ecosystems previous studies generally focus on single loess sequences in the chinese loess plateau and conflicting conclusions on c4 c3 have been reached when studying carbon isotope ratios in carbonate and organic matter in this paper we report a comprehensive carbon isotopic characterization of total organic carbon toc and individual higher plant leaf waxes from five loess sequences spanning the last 35 ka from the chinese loess plateau clp the five coring sites encompass large gradients of annual mean temperature 9 2 13 9 c and precipitation 402 673 mm allowing us to assess the controlling mechanisms on c4 c3 plant ratios glacial interglacial sequences provide carbon isotope data for comparison with other climatic and environmental proxies such as lithology and magnetic susceptibility our results demonstrate that increased c4 c3 ratios are positively correlated with higher temperature and increased summer rainfall which characterize stronger summer monsoon in all five sites we conclude c4 abundance increases from the last glacial to the holocene in response to greater monsoon activity and that the c4 expression is suppressed in the cold and drier intervals

archaeal lipids in neogene dolomites monterey and sisquoc formations california planktic versus benthic archaeal sources abstract the distribution of archaeal lipids including archaeol and glycerol dibiphytanyl glycerol tetraethers gdgts in dolomite concretions and surrounding sediment from the monterey formation miocene and the sisquoc formation miocene pliocene were examined to distinguish planktic from benthic contributions for this purpose dolomites with positive 13 c values 7 to 13 were chosen such highly positive values point to pronounced methanogenesis of benthic archaea in the sedimentary column at first glance distributions and relative abundances of gdgts in both dolomites and background sediment were similar resembling patterns of marine planktic crenarchaea a contribution of benthic euryarchaea to the gdgt pool became evident only from variations in the 13 c values of different biphytanes obtained after ether cleavage of gdgts whereas bi and tricyclic biphytanes had an isotopic signal typical of planktic archaea 13 c 23 6 to 20 5 and 23 4 to 21 2 respectively for both dolomite and background sediment acyclic and monocyclic biphytanes showed lower values for dolomite samples 25 1 to 22 6 and 27 6 to 24 7 respectively indicating a contribution of lipids from benthic archaea the isoprenoid diether archaeol 13 c 23 9 to 22 9 assigned to euryarchaea was only detected in dolomite samples also reflecting additional input from sedimentary archaea probably autotrophic methanogens the occurrence of lipids derived from methanogenic archaea agrees with the strong 13 c enrichment of dolomites and with mineral formation taking place in the zone of archaeal methanogenesis this implies that the lipid biomarker inventory of sedimentary strata needs to be interpreted carefully as it is often not straightforward to discriminate between input from the water column and sedimentary microbial activity

late holocene environmental reconstruction using cave sediments from belize cave sediments collected from reflection cave on the vaca plateau belize show variations in the 13 c values of their fulvic acids fas which indicate periods of vegetation change caused by climatic and maya influences during the late holocene the 13 c values range from 27 11 to 21 52 a shift of 5 59 which suggests fluctuating contributions of c3 and c4 plants throughout the last 2 5 ka with c4 plant input reflecting periods of maya agriculture maya activity in the study area occurred at different intensities from 2600 cal yr bp until 1500 cal yr bp after which agricultural practices waned as the maya depopulated the area these changes in plant assemblages were in response to changes in available water resources with increased aridity leading to the eventual abandonment of agricultural areas the ix chel archaeological site located in the study area is a highland site that would have been among the first agricultural settlements to be affected during periods of aridity during these periods minimal water resources would have been available in this highly karstified well drained area and supplemental groundwater extraction would have been difficult due to the extreme depth of the water table 2007 university of washington all rights reserved

climatic stages recorded in sediments of the gunang cave south korea abstract this paper presents and analyses lithological stratigraphic and geochronological data on the gunang cave which is an important archaeological site in south korea it discusses problems of the age and origin of its sedimentary sequence which consists of clastics and hardpan speleothems the sediments compose a 4 m thick lens near the cave entrance the lens formed during the middle late pleistocene and holocene according to 14 c and u th dating the changes of cave environments are reconstructed based on sedimentological palynological mineralogical magnetic and geochemical data the clastic sediment unit consists of roof fallen limestone debris cemented by fine grained matrix the matrix is dominated by silt 80 which aeolian component is 60 65 the amount of the wind blown component is persistent throughout the clastic layers suggesting a relatively stable depositional process in dry environment in contrast three lime cemented hardpans formed in a wet environment of groundwater seepage the revised age model suggests that the hardpans formed in early mis1 mis 5 5 and mis 7 and therefore correspond to the wetness maximums of these warm stages

δ13c variations of loess organic matter as a record of the vegetation response to climatic changes during the weichselian this paper presents high resolution records of 13 c 12 c ratios of organic matter from two loess sequences in northwestern europe our analysis is the first attempt to use organic matter 13 c as a record of the response of vegetation to climatic variations in an area where climatic changes were not strong enough to induce a radical change in vegetation cover over the last climatic cycle the vegetation of the rhine valley showed a strong predominance of c3 plants thus the small 13 c variations with an amplitude of only 1 5 to 3 are interpreted as corresponding to fluctuations in water supply and atmospheric co 2 concentration variations rather than to the ratio of c4 to c3 vegetation furthermore loess sequences accumulated at high rates and allow high correlation with climatic proxy data like the greenland ice sheet project 2 gisp2 18 o and the variations in co 2 concentration recorded in the vostok ice core the 13 c constitutes a reliable and complementary proxy to study small climatic stresses endured by vegetation during the weichselian in northwestern europe moreover by using absolute age control and correlations between global vostok co 2 or semi global gisp2 18 o climate effects 13 c values of organic matter in loess sequences offer a new tool to establish a refined chronology in continental sequences

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

a sedimentological model of organic matter preservation and phosphogenesis in the miocene monterey formation at haskells beach goleta central california abstract at haskells beach west of santa barbara ca u s a the upper part of the miocene monterey formation is predominantly composed of organic rich mudstone which is interstratified with phosphatic laminae and lenses minor lithologies consist of dolomite volcanic ash porcelanite chert and condensed phosphate these sediments date from the end of the serravallian and almost the entire tortonian 11 05 7 85 ma based on calcareous nannofossils and the 13 c org record which correlates well with the global record sediments have total organic carbon values between 2 75 and 9 15 wt average value 6 48 wt n 61 rock eval analyses show the dominance of type ii kerogen the sediment accumulation rate varied between 5 9 and 84 7 m ma correspondingly organic carbon accumulation rates range between 0 08 and 1 43 g cm 2 ky average value 0 48 g cm 2 ky total phosphorus contents in the organic rich mudstone vary between 0 001 and 3 48 wt and c org p org ratios show high values of up to 4727 average value 2232 whereas c org p total values are low up to 185 average value 52 this indicates that early diagenetic organic matter degradation was a source of phosphate in phosphogenesis in addition other sources of phosphate were necessary in order to explain the abundance of phosphate relative to organic matter such as the transfer of dissolved inorganic phosphate into the sediments slumps angular unconformities erosive surfaces reworked clasts and nodules and condensed phosphatic layers suggest that hydrodynamic conditions were important and likely variable leading to frequent erosion and sediment reworking under these circumstances organic matter was predominantly delivered during gravity flow events which were followed by longer periods of low sediment accumulation and phosphogenesis of the uppermost sediment layer associated pore occlusion by phosphate minerals may have considerably enhanced the preservation of organic matter during the early late miocene a progressive change is observed from the mixed accumulation of organic phosphate biosilica and carbonate sediments to the predominant accumulation of biosilica rich sediments this change is related to more intense upwelling a shift of the upwelling center to the californian coastline and a leveling out of basin topography leading to a more even spread of biosilica

pollen record of the mid to late holocene centennial climate change on the east coast of south korea and its influential factors abstract to understand historical climate change in western pacific coastal areas a sediment core soj 2 from the stable sedimentary environment of the songjiho lagoon on the east coast of south korea was obtained for centennial resolution palynological analysis the ages of the soj 2 core is well controlled by carbon 14 dating with high resolution accelerator mass spectrometry ams and the results indicated a general warm to cold climate trend from the mid holocene to the present which can be divided into two different stages a warmer stage between 6842 and 1297 cal yr bp and a colder stage from 1297 cal yr bp to the present with fluctuations during these stages the climate was wetter from 6842 to 6227 cal yr bp and 4520 to 1297 cal yr bp and was drier from 6227 to 4520 cal yr bp the climate changed to cold and dry during the period from 1297 425 cal yr bp the impact of human activity on the climate began at approximately 1297 cal yr bp and became pronounced starting in 425 cal yr bp the general cooling trend may represent a response to decreasing solar insolation however the relative dryness or wetness of the climate may have been co determined by westerlies and the east asian summer monsoon easm the climate had a teleconnection with the north atlantic region resulting from changes in solar activity nevertheless ei nino southern oscillation enso activity played an important role in impacting the easm changes in western pacific coastal areas

benthic phosphorus regeneration net primary production and ocean anoxia a model of the coupled marine biogeochemical cycles of carbon and phosphorus we examine the relationships between ocean ventilation primary production water column anoxia and benthic regeneration of phosphorus using a mass balance model of the coupled marine biogeochemical cycles of carbon c and phosphorus p the elemental cycles are coupled via the redfield c p ratio of marine phytoplankton and the c p ratio of organic matter preserved in marine sediments the model assumes that on geologic timescales net primary production in the oceans is limited by the upwelling of dissolved phosphorus to the photic zone the model incorporates the dependence on bottom water oxygenation of the regeneration of nutrient phosphorus from particulate matter deposited at the water sediment interface evidence from marine and lacustrine settings modern and ancient demonstrates that sedimentary burial of phosphorus associated with organic matter and ferric oxyhydroxides decreases when bottom water anoxia dysoxia expands steady state simulations show that a reduction in the rate of thermohaline circulation or a decrease of the oxygen content of downwelling water masses intensifies water column anoxia dysoxia and at the same time increases surface water productivity the first effect reflects the declining supply of oxygen to the deeper parts of the ocean the second effect is caused by the enhanced benthic regeneration of phosphorus from organic matter and ferric oxyhydroxides sedimentary burial of organic carbon and authigenic calcium phosphate mineral francolite on the other hand is promoted by reduced ocean ventilation according to the model global scale anoxia dysoxia leads to a more efficient recycling of reactive phosphorus within the ocean system consequently higher rates of primary production and organic carbon burial can be achieved even when the continental supply of reactive phosphorus to the oceans remains unchanged

alkenone temperature estimates for the east sea during the last 190 000 years abstract the late quaternary records of alkenone based sea surface temperature sst from a core located in the western margin of the east sea japan sea showed that the estimated temperature fluctuated greatly the variability being consistent with orbital scale global climate records during the period of marine isotope stage mis 6 the alkenone temperatures were low 7 10 c whereas during mis 5 5 the temperature increased rapidly up to 21 c during the entire period of mis 5 the temperature decreased from 21 c to 13 c then the temperature fluctuated between 10 c and 15 c during miss 4 and 3 after that it continued to fluctuate between 15 c and 17 c variation in the east sea sst is considered to be closely related to changes in the east asian monsoon system and seawater transport by the tsushima warm current the glacial surface cooling could be associated with the strong winter monsoon and or weakened summer monsoon in east asia during the glacial period when the sea level was low the influx of warm water was restricted and this might have enhanced the lowering of the surface temperature these conditions most likely caused significant changes in surface water circulation a basin scale cyclonic gyre might have occurred in the east sea without the development of the subpolar front during the interglacial period the surface warming seems to be related to the intensified summer monsoon system the high stand of the sea level and climate change most likely caused the development of cyclonic and anti cyclonic gyres in the north and south respectively and the subpolar front in the central part of the sea

climatically driven glacial interglacial variations in c3 and c4 plant proportions on the chinese loess plateau high resolution 13c records of bulk organic matter om from three loess paleosol successions from the central chinese loess plateau document systematic fluctuations in c3 and c4 plant abundance for certain intervals during the past 620 k y measured 13c values of om in paleosols are less negative by 0 5 4 and total organic carbon toc contents are higher by up to 0 5 wt relative to corresponding values in loess deposits the 13com and toc decrease from peak values in paleosols progressively into overlying and underlying loess deposits integrated 13com toc and magnetic susceptibility rec ords indicate an increase in c4 vegetation to 50 during peak paleosol formation and a decrease in c4 vegetation to 30 during loess deposition for three of the past glacial interglacial cycles these results indicate that c4 plant abundance declined during glacials in this mid latitude region driven primarily by a shift to enhanced winter precipitation and lower temperatures and further contribute to the rapidly growing body of evidence that low p co2 during pleistocene glacials was insufficient to trigger c4 plant expansion without coincident favorable climatic conditions

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds

chert spheroids of the monterey formation california usa early diagenetic structures of bedded siliceous deposits chert spheroids are distinctive early diagenetic features that occur in bedded siliceous deposits spanning the phanerozoic these features are distinct in structure and genesis from similar concentrically banded wood grain or onion skin chert nodules from carbonate successions in the miocene monterey formation of california usa chert spheroids are irregular concentrically banded nodules which formed by a unique version of brittle differential compaction that results from the contrasting physical properties of chert and diatomite during shortening there is brittle fracture of diatomite around and horizontally away from the convex surface of strain resistant chert nodules unlike most older siliceous deposits the monterey formation still preserves all stages of silica diagenesis thus retaining textural mineralogical and geochemical features key to unravelling the origin of chert spheroids and other enigmatic chert structures chert spheroids found in opal a diatomite form individual nodules composed of alternating bands of impure opal ct chert and pure opal ct or chalcedony with increased burial diagenesis surrounding diatomite transforms to bedded porcelanite or chert and spheroids no longer form discrete nodules yet still display characteristic concentric bands of pure and impure microcrystalline quartz and chalcedony petrographic observations show that the purer silica bands are composed of void filling cement that precipitated in curved dilational fractures and do not reflect geochemical growth banding in the manner of liesegang phenomena invoked to explain concentrically banded chert nodules in limestone chertification of bedded siliceous sediment can occur more shallowly 100 m and rapidly 1 myr than the bulk silica phase transitions forming porcelanite or siliceous shale in the monterey formation and other hemipelagic pelagic siliceous deposits early diagenesis is indicated by physical properties deformational style and oxygen isotopic composition of chert spheroids early formed cherts formed by pore filling impregnation of the purest primary diatomaceous beds along permeable fractures and in calcareous siliceous strata