late palaeocene early eocene dinoflagellate cysts from the turgay strait kazakhstan correlations across ancient seaways abstract the results of a quantitative palynological analysis emphasizing organic walled dinoflagellate cysts dinocysts of palaeocene eocene deposits exposed in the sokolovsky quarry turgay trough northern kazakhstan are presented here located in the ancient turgay strait a former seaway presumed to have connected the tethyan and boreal oceans and seas in the early palaeogene the sokolovsky quarry outcrop occupies a key position for the analysis of connections between these realms in general the dinocyst succession of sokolovsky closely resembles coeval arctic ocean north sea basin counterparts only in one interval endemic and or possibly tethyan species co occur the successive dinocyst assemblages allow recognition of the late palaeocene early eocene p5a p5b p6a p6b and e2 zones established in the north sea basin the succession is interpreted to represent parts of several third order sea level cycles correlative with those recognised in the north sea basin detailed comparison with similar studies from southeastern england allows the recognition of parts of third order cycles thanetian 1 tht 1 2 4 5 and ypresian ypr 3 in addition two important stratigraphic gaps within the palaeocene eocene succession are recognised possibly reflecting times of sea level lowering these gaps are inferred from 1 the absence of a complete p5b p6a transition 2 the absence of zone e1 and 3 bio sequence stratigraphy combined results indicate that the turgay strait flooded from the north between 57 8 and 57 1 ma cycles tht 1 and 2 in part with a minor missing section during the second phase of turgay flooding 56 4 55 3 ma evidence may be taken to indicate increased influence from the tethyan ocean and or warmer conditions deposits reflecting the late palaeocene thermal maximum associated with this interval are present at sokolovsky quarry this interval is marked by abundant apectodinium spp including a augustum and organic rich layers a third flooding is correlative to the london clay transgression from 54 5 ma from our study no decisive evidence has become available that confirms that a connection between the arctic and tethyan oceans via the turgay strait in the early palaeogene existed nevertheless during intervals of major sea level fall the turgay strait depression may be regarded to have been an important feature for migrating terrestrial biota four new wetzeliellioid taxa apectodinium sp a apectodinium sp b wilsonidium sp a and wilsonidium sp b are described from the palaeocene part of the section

towards radiocarbon calibration beyond 28 ka using speleothems from the bahamas we present a new speleothem record of atmospheric 14c between 28 and 44 ka that offers considerable promise for resolving some of the uncertainty associated with existing radiocarbon calibration curves for this time period the record is based on a comprehensive suite of ams 14c ages using new low blank protocols and u th ages using high precision mc icpms procedures atmospheric 14c was calculated by correcting 14c ages with a constant dead carbon fraction dcf of 22 7 5 9 based on a comparison of stalagmite 14c ages with the intcal04 reimer et al 2004 calibration curve between 15 and 11 ka the new 14c speleothem record shows similar structure and amplitude to that derived from cariaco basin foraminifera hughen et al 2004 2006 and the match is further improved if the latter is tied to the most recent greenland ice core chronology svensson et al 2008 these data are however in conflict with a previously published 14c data set for a stalagmite record from the bahamas gb 89 24 1 beck et al 2001 which likely suffered from 14c analytical blank subtraction issues in the older part of the record the new bahamas speleothem 14c data do not show the extreme shifts between 44 and 40 ka reported in the previous study beck et al 2001 causes for the observed structure in derived atmospheric 14c variation based on the new speleothem data are investigated with a suite of simulations using an earth system model of intermediate complexity data model comparison indicates that major fluctuations in atmospheric 14c during marine isotope stage 3 is primarily a function of changes in geomagnetic field intensity although ocean atmosphere system reorganisation also played a supporting role

constraints on the timing of explosive volcanism at aso and aira calderas japan between 50 and 30 ka new insights from the lake suigetsu sedimentary record sg14 core

atmospheric radiocarbon calibration to 45 000 yr b p late glacial fluctuations and cosmogenic isotope production more than 250 carbon 14 accelerator mass spectrometry dates of terrestrial macrofossils from annually laminated sediments from lake suigetsu japan provide a first atmospheric calibration for almost the total range of the radiocarbon method 45 000 years before the present the results confirm the recently revised floating german pine chronology and are consistent with data from european and marine varved sediments and combined uranium thorium and carbon 14 dating of corals up to the last glacial maximum the data during the glacial show large fluctuations in the atmospheric carbon 14 content related to changes in global environment and in cosmogenic isotope production

export of nutrient rich northern component water preceded early oligocene antarctic glaciation the onset of the north atlantic deep water formation is thought to have coincided with antarctic ice sheet growth about 34 million years ago ma however this timing is debated in part due to questions over the geochemical signature of the ancient northern component water ncw formed in the deep north atlantic here we present detailed geochemical records from north atlantic sediment cores located close to sites of deep water formation we find that prior to 36 ma the northwestern atlantic was stratified with nutrient rich low salinity bottom waters this restricted basin transitioned into a conduit for ncw that began flowing southwards approximately one million years before the initial antarctic glaciation the probable trigger was tectonic adjustments in subarctic seas that enabled an increased exchange across the greenland scotland ridge the increasing surface salinity and density strengthened the production of ncw the late eocene deep water mass differed in its carbon isotopic signature from modern values as a result of the leakage of fossil carbon from the arctic ocean export of this nutrient laden water provided a transient pulse of co2 to the earth system which perhaps caused short term warming whereas the long term effect of enhanced ncw formation was a greater northward heat transport that cooled antarctica

lateglacial calendar year chronology based on annually laminated sediments from lake meerfelder maar germany abstract annually laminated sediments from lake meerfelder maar mfm in the eifel germany provide an independent calendar year timescale for the last glacial interglacial transition changes in varve thickness and varve facies reflect significant environment variations during this period the general micro facies pattern confirms that diatomaceous organic varves are favoured during warm climatic phases while cold periods generate higher allochthonous sediment fluxes an exception is the significant increase in diatom blooms at the beginning of the younger dryas six lateglacial biozones have been defined by litt and stebich quaternary international 1999 the sediment record comprises two tephra layers as chronomarkers the laacher see tephra 12 880 varve years bp is a continent wide correlation horizon while the ulmener maar tephra provides regional chronological links the beginning of the lateglacial warming is dated at 14 450 varve years vyrs bp which is regarded as the minimum age three abrupt cold spells interrupted the lateglacial interstadial at 13 800 vyrs bp oldest dryas 13 540 vyrs bp older dryas and 12 680 vyrs bp younger dryas the oldest dryas 130 years and the older dryas 190 years were rather short while the younger dryas lasted much longer 1090 years the mfm chronology was compared with ice core timescales from gisp2 and grip there is a good agreement between these timescales with the grip model age ss09 providing the best match to the mfm chronology

paleogene paleoceanography of the arctic ocean is constrained by the middle or late eocene age of usgs core fl 422 evidence from silicoflagellates arctic ocean core fl 422 has been of central importance in arctic tectonics and paleoceanography because it provides the sole evidence for early cenozoic marine conditions in the arctic the presence of several eocene and eocene or oligocene guide species of silicoflagellates in samples from this core shows that it is no older than middle eocene and is not paleocene as previously reported there is no evidence of any paleocene 54 to 65 ma siliceous microfossils from core fl 422 paleoceanographic inferences conerning the cretaceous tertiary boundary and the timing of silica deposition in the arctic have been erroneous because of unsupported biostratigraphic correlations

identification and correlation of visible tephras in the lake suigetsu sg06 sedimentary archive japan chronostratigraphic markers for synchronising of east asian west pacific palaeoclimatic records across the last 150 ka abstract the lake suigetsu sg06 sedimentary archive from honshu island central japan provides a high resolution palaeoenvironmental record including a detailed record of explosive volcanism from japan and south korea thirty visible tephra are recorded within the 73 m long sg06 core which spans the last 150 ka here we describe and characterise these tephras based on major element glass composition which is useful for the identification and correlation of these tephras and the age models of the records in which they are found utilising the large number of radiocarbon measurements n 600 from terrestrial plant macrofossils in the lake suigetsu sg06 record we are able to provide precise and accurate ages for the tephras from eruptions within the last 50 ka glass compositional data of some of the largest eruptions from japan k ah at aso 4 aso a aso d and ata sampled at proximal outcrops are also presented these data show that the major element glass chemistry is distinctive for many of the visible sg06 tephra units and allows some of the layers to be correlated to known eruptions from volcanoes in japan and south korea namely k ah sg06 0967 u oki sg06 1288 at sg06 2650 aso 4 sg06 4963 sg06 4979 k tz sg06 5181 aso abcd sg06 5287 and ata sg06 5181 the following ages were obtained for the sg06 tephra units 3 966 4 064 cal ka bp 95 4 probability range for the sg06 0588 tephra 10 242 10 329 cal ka bp 95 4 probability range for sg06 1293 19 487 112 sg06 2012 ka bp 2 for sg06 1965 28 425 194 sg06 2012 ka bp 2 for sg06 2504 28 848 196 sg06 2012 ka bp 2 for sg06 2534 29 765 190 sg06 2012 ka bp 2 for sg06 2601 29 775 191 sg06 2012 ka bp 2 for sg06 2602 43 713 156 sg06 2012 ka bp 2 for sg06 3485 46 364 202 sg06 2012 ka bp 2 for sg06 3668 49 974 337 sg06 2012 ka bp 2 for sg06 3912 50 929 378 sg06 2012 ka bp 2 for sg06 3974 and improved ages for two of the most important tephra markers across japan the k ah 7 165 7 303 cal ka bp at 95 4 probability range sg06 0967 and at tephra 30 009 189 sg06 2012 ka bp at 2 sg06 2650

evidence from shark teeth for a brackish arctic ocean in the eocene greenhouse temperatures are rising at an unprecedented rate in the arctic and affecting the sensitive hydrological cycle with increased freshwater inputs to the marine environment a deep time analogue often used to understand and predict the environmental and ecological impacts of global warming is the early middle eocene greenhouse ca 53 38 ma although the terrestrial arctic during this interval is well documented marine records are rare and largely based on one central arctic ocean site at lomonosov ridge here we estimate a mean paleosalinity of 12 7 psu for coastal waters of the western arctic ocean by incorporating 18 o co 3 values of shark teeth with estimates of eocene arctic paleotemperature and freshwater 18 o values into a salinity model this paleosalinity is substantially lower than estimates by others for the eocene central arctic ocean 21 25 psu and today9s arctic ocean 32 35 psu our results provide the first eocene salinity estimate for the western arctic ocean and when considered with prior results from lomonosov ridge suggest a reduced surface salinity but larger salinity gradient 10 psu across the eocene arctic ocean during the early middle eocene greenhouse from an ecologic perspective while today9s lamniform sharks are largely intolerant of low salinity eocene species were abundant in the brackish arctic ocean suggesting that past environmental tolerances were much greater than today

benthic foraminiferal δ18o in the ocean s temperature salinity density field constraints on ice age thermohaline circulation benthic 18o data from 95 core sites are used to infer possible temperature salinity t s fields of the atlantic and pacific oceans at the last glacial maximum lgm a constraint of stable density stratification yields logically consistent scenarios for both t and s the solutions are not unique but are useful as a thinking tool using geosecs data we solve for the modem relationship between 18owater w and salinity in the deep sea w smow 1 529 s 53 18 as a starting point we assume that the slope of this equation applies to lgm conditions and predict 18ocalcite c gradients in equilibrium with probable t s fields of lgm deep and bottom waters benthic foraminiferal 18o data from the deep pacific 2 4 km depth and the bottom atlantic 4 km depth are 0 1 0 2 lower than from the deep atlantic 2 4 km depth at the lgm if the modern w s slope applies atlantic deep and bottom waters were more dense than pacific deep waters this assumption would imply bottom waters both fresher s 0 5 and colder t 3 c than overlying deep waters in conflict with other data suggesting ice age deep water much colder than at present it is also possible that the observed c gradients are an artifact of laboratory intercalibration if atlantic deep and bottom water c values were similar to deep pacific values this would be consistent with the hypothesis of a stronger southern ocean versus north atlantic source for deep ocean ventilation at the lgm taking the observed gradients at face value however a solution could be that the lgm w s slope in deep and bottom waters was higher than at present conceivably because of a stronger contribution of salt to the deep ocean via more intense sea ice freezing this would allow pacific deep waters and atlantic bottom waters to have a common source again in the antarctic both would be more dense than atlantic deep waters even though the deep waters were much colder than at present to better constrain these inferences drawn from the spatial distribution of benthic 18o we must reduce scatter in the 18o data with more high quality measurements in high sedimentation rate cores this is especially true at bottom water sites also we must intercalibrate mass spectrometers at different isotope laboratories more accurately to insure our isotope data are compatible

chemistry microstructure petrology and diagenetic model of jurassic dinosaur bones dinosaur national monument utah abstract the fossil bone mineral in dinosaurs from the morrison formation is well crystallized stoichiometric francolite the closely packed subparallel francolite crystals have equidimensional cross sections mostly 10 40 nm wide in contrast crystallites in unaltered mammal bone tissue are poorly crystallized nonstoichiometric carbonate hydroxyapatite a few nanometers thick and plate rod or needle shaped the diagenetic francolite crystals are elongated in the c axis direction as are bone tissue crystallites along permeable cracks francolite crystals grew to 250 nm wide compared to unaltered crystallites in mammal bones the francolite has higher concentrations of ba ce cr f la mn ni pb rb sr th u v and y and perhaps zr na and mg are lower in concentration diagene ic francolite grew from groundwater enriched in ions from silicic ashes in the brushy basin member and from dissolution of bone tissue crystallites after burial francolite grew on crystallite seeds filling the space formerly occupied by collagen perhaps half the tissue volume and dissolved crystallites the micron scale structures such as haversian canals and laminae are preserved because the diagenetic francolite retains the orientations of the seeds the laminae 1 10 m thick commonly preserve an orthogonal plywood structure the diagenetic growth of francolite during this type of bone fossilization implies that oxygen isotopic ratios measured in dinosaur bones even those that appear fresh and unaltered may dominantly reflect groundwater temperature rather than dinosaur body temperature trace element concentrations in the francolite may reflect groundwater composition rather than dinosaur diet pore filling cements precipitated in the sands and bones at shallow burial depths as evidenced by the 35 52 minus cement porosities of the sandstones and numerous uncompacted oversize pores filled by cements gypsum and calcite were precipitated from shallow alkaline groundwater as the groundwater became increasingly dominated by ions from silicic ash argentite chalcopyrite native gold native silver tiemannite and uraninite replaced areas of bone a few microns to tens of microns in size along cracks a thin chlorite crust commonly mantled francolite crystals along bone cracks and lined openings in bones and sandstones pervasive precipitation of a chalcedony crust followed with pseudomorphs of chalcedony after gypsum in larger cancellous openings the remaining space was fi led by the various forms of silica the bones are brown due to goethite filled cracks that cut pore filling minerals

how wet was the arctic eocene rain forest estimates of precipitation from paleogene arctic macrofloras the eocene was the warmest part of the cenozoic when warm climates extended into the arctic and substantive paleobotanical evidence indicates broadleaf and coniferous polar forests paleontological temperature proxies provide a basis for understanding arctic early paleogene climates however there is a lack of corresponding proxy data on precipitation both leaf physiognomic analysis and quantitative analysis of nearest living relatives of an arctic macroflora indicate upper microthermal to lower mesothermal moist climates mean annual temperature 13 15 c cold month mean temperature 4 c mean annual precipitation 120 cm yr for axel heiberg island in the middle eocene leaf size analysis of paleocene and eocene arctic floras demonstrates high precipitation for the paleogene western and eastern arctic the predicted enormous volume of freshwater entering the arctic ocean as a result of northward drainage of a significant region of the northern hemisphere under a high precipitation regime would have strongly affected arctic ocean salinity potentially supporting arctic ocean azolla blooms high paleogene precipitation around the arctic basin is consistent with high atmospheric humidity which would have contributed significantly to polar and global eocene warming

freshwater balance and the sources of deep and bottom waters in the arctic ocean inferred from the distribution of h218o data from sections across the eurasian basin of the arctic ocean occupied in 1987 and 1991 are used to derive information on the freshwater balance of the arctic ocean and on sources of the deep waters of the nansen amundsen and makarov basins using salinity h218o and mass balances we estimate the river runoff and the sea ice melt water fractions contained in the upper waters of the arctic ocean and infer pathways of the river runoff signal from the shelf seas across the central arctic ocean to fram strait the average mean residence time of the river runoff fraction contained in the arctic ocean halocline is determined to be about 11 to 14 years pacific water entering through bering strait is traced using silicate and its influence on the halocline waters of the canadian basin is estimated water column inventories of river runoff and sea ice melt water are calculated for a section just north of fram strait and implications of these inventories for sea ice export through fram strait are discussed comparison of the 18o 16o ratios of shelf water atlantic water and the deep waters of the arctic ocean indicate that the sources of the deep and bottom waters of the eurasian basin are located in the barents and kara seas

salinity of the eocene arctic ocean from oxygen isotope analysis of fish bone carbonate stable isotope analysis was performed on the structural carbonate of fish bone apatite from early and early middle eocene samples 55 to 45 ma recently recovered from the lomonosov ridge by integrated ocean drilling program expedition 302 the arctic coring expedition the 18o values of the eocene samples ranged from 6 84 to 2 96 vienna peedee belemnite with a mean value of 4 89 compared to 2 77 for a miocene sample in the overlying section an average salinity of 21 to 25 was calculated for the eocene arctic compared to 35 for the miocene with lower salinities during the paleocene eocene thermal maximum the azolla event at 48 7 ma and a third previously unidentified event at 47 6 ma at the azolla event where the organic carbon content of the sediment reaches a maximum a positive 13c excursion was observed indicating unusually high productivity in the surface waters

climate system transition from glacial to interglacial state around the beginning of the last termination evidence from a centennial to millennial scale climate rhythm a periodic variation on a centennial to millennial scale was observed in the manganese and iron contents of lake suigetsu sediments in japan dating from 19 0 to 5 7 cal kyr b p calibrated thousand years before present the increased manganese and iron contents which mainly indicate the relative abundance of siderite result from a greater vertical circulation in the lake during a cold period with a higher mass of manganese and iron oxide being precipitated the cold periods inferred from the increased manganese and iron contents coincide with the timing of ice rafting debris ird events in the north atlantic which span from the last termination to the holocene suggesting that the climate shift was hemispheric or probably global in nature the manganese variation resembles the residual atmospheric 14c production 14c data of the holocene that reflect variation in solar activity and its periodicities correspond with those of solar related climate changes from paleoproxy records in the north atlantic and east asia from the last cold stage to the holocene in particular the mn variation was larger in amplitude and shorter in timescale during the last cold stage when compared with those during the last termination and the holocene thereby possibly showing a significant difference in climate response to solar irradiance the transition of the climate system from a glacial to an interglacial state corresponds to the beginning of the last termination

humidity estimate for the middle eocene arctic rain forest the exquisite preservation of fossilized metasequoia trees that grew near 808n latitude during the middle eocene ca 45 ma in nunavut canada allowed for dd and d 18 o analyses of cellulose techniques previously restricted to wood 30 000 yr old from the isotopic results we determined that the middle eocene arctic atmosphere contained 23 the water found in the region s atmosphere today this water vapor contributed to a middle eocene greenhouse effect that insulated the polar region during dark polar winters

high resolution records of location and stratigraphic provenance from the rare earth element composition of fossil bones abstract bone apatite acts as a natural timed sampling device scavenging trace elements from local pore waters over timescales of ca 1 50 ka the rare earth element ree and u th composition of fossil bones reflects associated pore water compositions during the period of recrystallisation the ree composition of fossil bones is controlled by partitioning of ree between pore waters and particle surfaces and the ree composition of fossil bones reflects the ree composition of pore waters which vary spatially and temporally light ree are preferentially sorped onto particle surfaces thus the high la yb values seen in many bones from coastal marine and aeolian environments are best explained by release of ree from light ree enriched particles to local pore waters and subsequent immobilisation in recrystallising bones the ree compositions of bones recovered from pedogenically altered diatomite sediments of the olorgesailie formation of southern kenya vary over spatial scales of less than 10 m location accounts for 48 of the observed variation in bone chemistry and bones recovered from eight discrete excavations within the same time equivalent stratigraphic layer can be assigned to their excavation location with 70 accuracy based on a discriminant analysis of ree u and th composition despite this within layer variation bones recovered from different stratigraphic horizons within the olorgesailie formation can also be distinguished on the basis of their trace element composition bones recovered from four stratigraphic horizons spanning ca 0 5 million years were assigned to their correct stratigraphic layer with 90 accuracy where sedimentological conditions are favourable the trace element composition of fossil bone may be used to test stratigraphic provenance and burial location in excavated bone with a temporal resolution of

tracking aquatic change using chlorin specific carbon and nitrogen isotopes the last glacial interglacial transition at lake suigetsu japan joint carbon and nitrogen isotope measurements were made from chlorins chlorophyll a phaeophytin a and pyrophaeophytin a extracted from the last glacial interglacial transition sediments of lake suigetsu central japan these data highlight both the potential and difficulty of using chlorin specific isotopes to track aquatic change from lake sediments 13c and 15n of the three chlorins show coherent patterns with time supporting the theory that phaeophytin a and pyrophaeophytin a are early diagenetic products of chlorophyll a and that despite this transition their isotopic signatures remain intact however our data suggest that the isotopic composition of phaeophytin a and pyrophaeophytin a can be imprecise proxies for the isotope composition of chlorophyll a possibly owing to the complex array of factors which affect the synthesis transformation and sedimentation of these phaeopigments in nature the total accumulation of organic matter in lake suigetsu appears to be controlled by the balance of allocthonous and authocthonous material as reflected by the c n ratio however both bulk organic and chlorin specific 13c show similar changes suggesting that the first order variability in bulk organic 13c reflects aquatic change by contrast there is no similarity between chlorin and bulk 15n suggesting that interpretation of bulk 15n in this setting is compromised by diagenetic alteration the isotopic composition of chlorins are interpreted to reflect the response of aquatic primary productivity to post glacial environmental change however further research into the synthesis and transformation of chlorins in the modern environment is required in order to facilitate a more rigorous approach to interpreting isotope ratios in chlorins extracted from sediments

late paleocene arctic coastal climate inferred from molluscan stable and radiogenic isotope ratios abstract characterizing polar climates during past warm intervals is important for understanding greenhouse climate dynamics because high latitude surface temperatures and precipitation patterns are extremely sensitive to global climatic conditions model data comparisons of high latitude climates during past warm intervals cretaceous eocene pliocene are currently at odds specifically simulations of past warm climates produce polar regions characterized by sub freezing temperatures and significant seasonality whereas limited fossil proxy data indicate higher mean annual temperatures and low seasonality i e an equable climate we have constructed a data set to infer northern hemisphere polar marine temperatures during the late paleocene seasonal and mean annual temperature and the oxygen isotopic composition of precipitation are reconstructed for an arctic coastal setting during the thanetian 57 58 ma using fossil shell stable isotope profiles we estimate that coastal water temperatures varied between 10 and 15 c during the seasons of growth presumably spring summer and fall these findings support paleontological evidence implying northern hemisphere polar climates were seasonally warm during the late paleocene in addition estuarine fossil oxygen isotope profiles show periodic excursions to low values as low as 19 vpdb which indicate seasonal pulses of isotopically depleted freshwater

eocene continental climates and latitudinal temperature gradients global climate during the mesozoic and early cenozoic is thought to have been warmer than at present but there is debate about winter temperatures paleontological data indicate mild temperatures even at high latitudes and in mid latitude continental interiors whereas computer simulations of continental paleoclimates produce winter temperatures closer to modern levels foliar physiognomy and floristic composition of 23 eocene floras from the interior of north america and australia indicate cold month means generally 2 c even where the mean annual temperature mat was

an empirical method to predict sediment grain size from inorganic geochemical measurements grain size is one of the most fundamental properties of sediments it is frequently used in paleoclimate paleoceanographic and paleoenvironmental research as a proxy for river discharge current and wind strength and to identify mass flow deposits measuring grain size is however time consuming and destructive given the strong influence of grain size on sediment inorganic geochemistry single element variations measured by for example x ray fluorescence core scanning are increasingly used to estimate grain size variations at high resolution in sediment cores this approach is however limited to a narrow grain size range since individual elements only monotonically relate to grain size over a narrow size range here we present a simple code free multielement method based on partial least squares regression to predict sediment mean grain size from inorganic geochemical data over the range of sizes commonly encountered in sedimentary basins clay to sand the method was first tested using river sediment samples separated in 11 grain size fractions and it was later successfully applied to two sediment cores from the chilean fjords our method only requires measuring grain size on a limited number around 10 of selected training samples and it allows to predict mean grain size at x ray fluorescence core scanner resolution this method has the potential to be applied to any lake or marine sediment core provided sediment provenance weathering and diagenesis remain relatively stable through time and we anticipate that it will result in a significant increase in the resolution of sediment proxy records of climate and environmental change plain language summary sediment grain size is one of the best indicators of past transport conditions here we present a method to predict mean sediment grain size from inorganic geochemical measurements this method can be applied to geochemical measurements obtained by x ray fluorescence core scanning to generate grain size profiles quickly and at high resolution and we anticipate that it will result in much improved paleoclimate and paleoenvironmental reconstructions

a siliceous microfossil view of middle eocene arctic paleoenvironments a window of biosilica production and preservation integrated ocean drilling program iodp expedition 302 the arctic coring expedition acex unearthed the most significant find of paleogene siliceous microfossils in nearly 2 decades 100 m of early middle eocene organic rich finely laminated sediments contain abundant marine and freshwater siliceous microfossils allowing intriguing insights into central arctic paleoenvironments during the start of cenozoic cooling largely endemic assemblages of marine diatoms and ebridians are preserved along with very high abundances of chrysophyte cysts the endogenously formed resting stage of freshwater algae an overall brackish environment is invoked but variations in group dominance suggest episodic changes in salinity stratification and trophic status with the backing of inorganic geochemistry we synthesize the sediment characteristics by hypothesizing an environmental model for the cooccurrence of these diverse siliceous microfossil groups we also report on initial insights into the composition of some of the laminations which may help explain the formation of this rich sediment archive

dinosaur bones fossils or pseudomorphs the pitfalls of physiology reconstruction from apatitic fossils abstract a prerequisite to any attempt to reconstruct thermophysiology of ancient animals through analysis of stable isotopes of oxygen is the assumption that apatitic fossils are isotopically unaltered parts of their original skeletons we suggest that sufficient evidence is available to seriously question this assumption because living bones contain about 1 3 by weight of organic matrix mass balance considerations show that at least half of an apatitic fossil must be new material added post mortem furthermore living apatitic skeletons contain almost no rare earth elements and uranium whereas apatitic fossils bear high concentrations of these elements additionally we found that while in living fish correlation between 18o of oxygen in the phosphate and that in the carbonate of apatite is poor these two values are linearly correlated in fossil fish this suggests diagenetic recrystallization has taken place perfect preservation of micro textures such as haversian canals does not prove the pristine condition of a fossil some of the most beautifully preserved fossils are highly silicified most apatitic fossils probably are pseudomorphs replacing original skeletal elements whereas distribution of stable isotopes of oxygen in fossils might provide information about their burial environment it could be misleading in attempts to interpret the organisms physiology this cautionary note is supported by the similarity of 18op in bones of coexisting fossil fish dinosaurs and various other reptiles at different latitudes the overlap of predicted 18op values in fish and mammals living in contact with the same environmental water also weakens the hope that ectotherms can be distinguished from endotherms by the isotopic composition of oxygen in their bones and teeth

climate sensitivity to arctic seaway restriction during the early paleogene abstract the opening and closing of ocean gateways affects the global distribution of heat salt and moisture potentially driving climatic change on regional to global scales between 65 and 45 million years ago ma during the early paleogene exchange between the arctic and global oceans occurred through two narrow and shallow seaways the greenland norway seaway and the turgai strait sediments from the arctic ocean suggest that during this interval the surface ocean was warm brackish and episodically enabled the freshwater fern azolla to bloom the precise mechanisms responsible for the development of these conditions in the paleogene arctic remain uncertain here we show results from an isotope enabled atmosphere ocean general circulation model which indicate that northern hemisphere climate would have been very sensitive to the degree of oceanic exchange through the arctic seaways we also present modelled estimates of seawater and calcite 18o for the paleogene by restricting these seaways we simulate freshening of the surface arctic ocean to 6 psu and warming of sea surface temperatures by 2 c in the north atlantic and 5 10 c in the labrador sea our results may help explain the occurrence of low salinity tolerant taxa in the arctic ocean during the eocene and provide a mechanism for enhanced warmth in the north western atlantic we propose that the formation of a volcanic land bridge between greenland and europe could have caused increased ocean convection and warming of intermediate waters in the atlantic if true this result is consistent with the theory that bathymetry changes may have caused thermal destabilisation of methane clathrates and supports a tectonic trigger hypothesis for the paleocene eocene thermal maximum petm

east asian monsoon variability between 15 000 and 2000 cal yr bp recorded in varved sediments of lake sihailongwan northeastern china long gang volcanic field a palaeohydrological reconstruction on decadal scale for the period 15000 2000 cal yr bp based on calculated net accumulation rates for biogenic silica f bsio2 and additional proxies sedimentol

a younger dryas varve chronology from the rehwiese palaeolake record in ne germany abstract the first 1400 year floating varve chronology for north eastern germany covering the late allerod to the early holocene has been established by microscopic varve counts from the rehwiese palaeolake sediment record the laacher see tephra lst at the base of the studied interval forms the tephrochronological anchor point the fine laminations were examined using a combination of micro facies and xrf analyses and are typical of calcite varves which in this case provide mainly a warm season signal two varve types with different sub layer structures have been distinguished i complex varves consisting of up to four seasonal sub layers formed during the allerod and early holocene periods and ii simple two sub layer type varves only occurring during the younger dryas the precision of the chronology has been improved by varve to varve comparison of two independently analyzed sediment profiles based on well defined micro marker layers this has enabled both 1 the precise location of single missing varves in one of the sediment profiles and 2 the verification of varve interpolation in disturbed varve intervals in the parallel core inter annual and decadal scale variability in sediment deposition processes were traced by multi proxy data series including seasonal layer thickness high resolution element scans and total organic and inorganic carbon data at a five varve resolution these data support the idea of a two phase younger dryas with the first interval 12 675 12 275 varve years bp characterised by a still significant but gradually decreasing warm season calcite precipitation and a second phase 12 275 11 690 varve years bp with only weak calcite precipitation detailed correlation of these two phases with the meerfelder maar record based on the lst isochrone and independent varve counts provides clues about regional differences and seasonal aspects of yd climate change along a transect from a location proximal to the north atlantic in the west to a more continental site in the east

an extended and revised lake suigetsu varve chronology from 50 to 10 ka bp based on detailed sediment micro facies analyses abstract lake suigetsu japan is a key site for radiocarbon 14c calibration and palaeo environmental reconstruction in east asia here we present a description of the sediment micro facies which in combination with a new approach to varve interpolation allows construction of a revised varve based chronology that extends the previous 2012 varve based chronology by 10 ka back to 50 ka bp challenges in varve counting and interpolation which were previously discussed in detail only for the last glacial interglacial transition are described here back to 50 ka bp furthermore the relative merits of varve counting by xrf scanning and by thin section microscopy are discussed facies analysis reveals four facies zones their transitions driven by both local and climatic controls the lamination quality of the sediment is highly variable and varve interpolation reveals that in the analysed time interval on average only 50 of the annual cycles are represented by seasonal layers in the remaining years seasonal layers are indistinguishable i e either did not form or were not preserved for varve interpolation an advanced version of the varve interpolation program was used which enabled the construction of the longest purely varve dated chronology published despite long intervals of poor lamination quality the calculated interpolation uncertainty is 8 9 and 4 6 which is well within expectations considering the high degree of interpolation and the length of the record

pollen event stratigraphy of the varved sediment of lake suigetsu central japan from 15 701 to 10 217 sg vyr bp suigetsu varve years before present description interpretation and correlation with other regions high resolution pollen data average interval between samples 15 years are reported on part of a varved sediment core from lake suigetsu japan spanning the interval 15 701 to 10 217 sg vyr bp suigetsu varve years before present this new record is compared with a previously proposed event stratigraphy based on pollen based reconstructed changes of mean annual temperature the deglacial climate history reconstructed at lake suigetsu resembles that observed in the north atlantic although the major boundaries of pollen zones are asynchronous with those in the north atlantic event stratigraphy by several centuries the onset of the late glacial interstadial occurred earlier in japan than in the north atlantic this demonstrates that the climate in japan was closely linked to the low latitude pacific sea surface temperatures that first reacted to orbital forcing conversely the onset of the subsequent cold reversal phase in japan lagged that of the north atlantic younger dryas by several centuries the duration of this cold phase was about the same as the younger dryas event but the amplitude was much reduced 4 2 c in mean annual temperature these findings support the hypothesis that this pan hemispheric cooling event was triggered by north atlantic forcing most probably by a meltwater pulse and an associated change in the north atlantic thermohaline circulation however the mechanism which transmitted the change in the north atlantic to the far east is unknown

carbon and nitrogen isotope excursions in mid pleistocene sapropels from the tyrrhenian basin evidence for climate induced increases in microbial primary production the modern mediterranean sea is oligotrophic yet its sediment record contains layers of organic carbon rich sapropels at 21 ky precessional spacing that imply periods of elevated paleoproductivity that approached the high productivities of modern upwelling systems resolution to this paradox is provided by lines of evidence suggesting that the mode of primary productivity changed from one dominated by algae to one during times of sapropel deposition in which photosynthetic bacteria were important we have made a high resolution comparison of the organic carbon and nitrogen isotopic compositions of three sapropels and their background sediments in a 3 m sequence that corresponds to 1001 to 946 ka organic 13c values systematically increase from 26 to 21 and 15n values systematically decrease from 4 to 0 as organic carbon mass accumulation rates increase in the sapropel layers the increase in carbon isotope values mirrors the increases in primary productivity and associated organic matter export indicated by the increased mass accumulation rates the decrease in nitrogen isotope values implies major contributions of nitrogen fixing cyanobacteria to the total marine productivity the precessional minima with which sapropels coincide were times of wetter climate that stratified the surface mediterranean sea increased delivery of soil derived phosphorus and evidently amplified microbial primary production our high resolution study reveals several relatively rapid excursions into and out of the high productivity mode that suggest that sapropel deposition was a climate sensitive surface driven phenomenon that was not accompanied by basin wide stagnation

seasonally specific responses of the east asian monsoon to deglacial climate changes the deglacial meltwater pulse in the north atlantic that induced the younger dryas event also prompted climate cooling in east asian monsoon regions such as japan and coastal mid latitude china however very little is understood about the mechanism that can transmit changes in the north atlantic to the far east here we show that the shutdown of the north atlantic thermohaline circulation brought about significantly lower temperatures and higher precipitation in the japanese winter whereas the change in the japanese summer climate was considerably smaller the cooling of the siberian air mass seems to have caused an increased pressure gradient between siberia and the west pacific in winter intensifying the winter monsoon the mongolian high pressure system and the westerly jet stream played an important role in the teleconnection in contrast the warming at the onset of the late glacial interstadial gi 1 bolling allerod in the west pacific did not have season specific features implying that the principal driving mechanism of this warming event may lie in a pan hemispheric or global factor such as insolation changes

composition and consequences of the intcal20 radiocarbon calibration curve radiocarbon calibration is necessary to correct for variations in atmospheric radiocarbon over time the intcal working group has developed an updated and extended radiocarbon calibration curve intcal20 for northern hemisphere terrestrial samples from 0 to 55 000 cal yr bp this paper summarizes the new datasets changes to existing datasets and the statistical method used for constructing the new curve examples of the effect of the new calibration curve compared to intcal13 for hypothetical radiocarbon ages are given for the recent holocene the effect is minimal but for older radiocarbon ages the shift in calibrated ages can be up to several hundred years with the potential for multiple calibrated age ranges in periods with higher resolution data in addition the intcal20 curve is used to recalibrate the radiocarbon ages for the glaciation of the puget lowland and to recalculate the advance rate the ice may have reached its maximum position a few hundred years earlier using the new calibration curve the calculated advance rate is virtually unchanged from the prior estimate

eocene silicoflagellate and ebridian paleoceanography in the central arctic ocean the silicoflagellate and ebridian assemblages in early middle eocene arctic cores obtained by iodp expedition 302 acex were studied in order to decipher the paleoceanography of the upper water column the assemblages in lithologic unit 2 49 7 45 1 ma one of the biosiliceous intervals were usually endemic as compared to the assemblages that occurred outside of the arctic ocean the presence of these endemic assemblages is probably due to a unique environmental setting controlled by the degree of mixing between the low salinity arctic waters and relatively high salinity waters supplied from outside the arctic ocean such as the atlantic and possibly the western siberian sea using the basin to basin fractionation model the early middle eocene arctic ocean corresponds to an estuarine circulation type which includes the modern day black sea the abundant down core occurrence of ebridians strongly suggests the past presence of low salinity waters and may indicate that low oxygen concentrations prevailed in the euphotic layer on the basis of the ecology of the modern ebridian hermesinum adriaticum

the role of sea ice and other fresh water in the arctic circulation salinity stratification is critical to the vertical circulation of the high latitude ocean we here examine the control of the vertical circulation in the northern seas and the potential for altering it by considering the budgets and storage of fresh water in the arctic ocean and in the convective regions to the south we find that the present day greenland and iceland seas and probably also the labrador sea are rather delicately poised with respect to their ability to sustain convection small variations in the fresh water supplied to the convective gyres from the arctic ocean via the east greenland current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past the north atlantic salinity anomaly of the 1960s and 1970s is a recent example it must have had its origin in an increased fresh water discharge from the arctic ocean similarly the freshening and cooling of the deep north atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the arctic ocean into the convective gyres finally we note that because of the temperature dependence of compressibility a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean

visions of ice sheets in a greenhouse world abstract backstripped eustatic estimates from new jersey and the russian platform show large 25 m and rapid 18 o record highlights the enigma this was the warmest interval of the past 200 my yet it was bracketed by two inferred eustatic falls of 25 m that were associated with two large 0 75 deep sea 18 o increases 92 93 ma mid turonian and 96 ma mid cenomanian we reconcile records of warm high latitudes with glacioeustasy by proposing that late cretaceous early eocene ice sheets generally reached maximum volumes of 8 12 10 6 km 3 20 30 m glacioeustatic equivalent but did not reach the antarctic coast hence coastal antarctica hence deep water remained relatively warm even though there were significant changes in sea level as the result of glaciation unlike the oligocene and younger icehouse world these ice sheets only existed during short intervals of peak milankovitch insolation leaving antarctica ice free during much of the greenhouse late cretaceous to middle eocene these results highlight the need to re evaluate the paradigm that polar ice sheets did not exist during times of warm high latitude climates

the blast in the past the rapidity and amount of carbon being released through human agency have been thought to be unprecedented not so it emerges from the evidence of anomalies in the ratios of carbon isotopes in an ocean core it seems that around 55 million years ago there was an equivalently swift and massive blast of carbon into the ocean and atmosphere the source was probably methane hydrates that are usually locked up in huge deposits on continental shelves

testing for ice sheets during the mid cretaceous greenhouse using glassy foraminiferal calcite from the mid cenomanian tropics on demerara rise the mid cretaceous is widely considered the archetypal ice free greenhouse interval in earth history with a thermal maximum around cenomanian turonian boundary time ca 90 ma however contemporaneous glaciations have been hypothesized based on sequence stratigraphic evidence for rapid sea level oscillation and oxygen isotope excursions in records generated from carbonates of questionable preservation and or of low resolution we present new oxygen isotope records for the mid cenomanian demerara rise that are of much higher resolution than previously available taken from both planktic and benthic foraminifers and utilizing only extremely well preserved glassy foraminifers our records show no evidence of glaciation calling into question the hypothesized ice sheets and rendering the origin of inferred rapid sea level oscillations enigmatic simple mass balance calculations demonstrate that this cretaceous sea level paradox is unlikely to be explained by hidden ice sheets existing below the limit of 18 o detection

characteristics of sedimentary varve chronologies a review abstract we constructed a varve data base vdb to study the worldwide distribution of varved sediment records and the fidelity of their varve chronologies clusters of lakes with varved sediments exist in central north america in the canadian arctic and in northern and central europe among the 108 sites included in the vdb varved records are typically 200 500 cm long and cover a period of 1000 2000 years their varve chronologies are often based on counting of annual layers from fresh sediment surfaces and photographs or from epoxy embedded sediment blocks and thin sections the vdb indicates that chronological errors associated with counting sedimentary varves fall generally between 1 and 3 but only 57 of published records are providing quantitative error estimations for their chronologies with a careful documentation of varves and by applying radiometric dating methods to surface sediments as well as using historical events as time markers there is the potential of having centennial long varved records with a very precise age depth control however it is unrealistic to expect errors significantly below 1 from several millennia long sections we found no indication that varve chronologies would have been substantially more accurate and precise in some parts of the world than in others or statistically dependent on varve thickness or temporal extension of a varved sequence according to the vdb close to 90 of the published varve chronologies have been cross checked with some independent dating methods

the early miocene onset of a ventilated circulation regime in the arctic ocean deep water formation in the northern north atlantic ocean and the arctic ocean is a key driver of the global thermohaline circulation and hence also of global climate1 deciphering the history of the circulation regime in the arctic ocean has long been prevented by the lack of data from cores of cenozoic sediments from the arctic s deep sea floor similarly the timing of the opening of a connection between the northern north atlantic and the arctic ocean permitting deep water exchange has been poorly constrained this situation changed when the first drill cores were recovered from the central arctic ocean2 here we use these cores to show that the transition from poorly oxygenated to fully oxygenated ventilated conditions in the arctic ocean occurred during the later part of early miocene times we attribute this pronounced change in ventilation regime to the opening of the fram strait a palaeo geographic and palaeo bathymetric reconstruction of the arctic ocean together with a physical oceanographic analysis of the evolving strait and sill conditions in the fram strait suggests that the arctic ocean went from an oxygen poor lake stage to a transitional estuarine sea phase with variable ventilation and finally to the fully ventilated ocean phase 17 5 myr ago the timing of this palaeo oceanographic change coincides with the onset of the middle miocene climatic optimum3 although it remains unclear if there is a causal relationship between these two events

sudden spreading of corrosive bottom water during the palaeocene eocene thermal maximum the palaeocene eocene thermal maximum was associated with warming and seafloor carbonate dissolution numerical simulations suggest that the spread of deep corrosive water from the north atlantic can explain the observed dissolution patterns

ocean and climate response to north atlantic seaway changes at the onset of long term eocene cooling abstract around the early middle eocene boundary the first occurrence of contourite drift sediments and widespread deep ocean erosion indicate changes in the north atlantic ocean circulation interestingly these changes coincide with the first steps of cenozoic cooling from the paleogene greenhouse climate towards the modern icehouse the cause for this ocean circulation reorganization is poorly understood since modern water mass tracers may have worked fundamentally different in the past and the paleoceanographic proxy record is limited in both time and space as a result it is challenging to reliably reconstruct the climatic and tectonic boundary conditions e g atmospheric greenhouse gas concentration and the depth and geometry of developing and closing passages between ocean basins in this study we attempt to identify thresholds in tectonic gateway passages and atmospheric co2 concentration using the fully coupled earth system model cosmos indeed the simulation of earth s past climates can unravel the physical processes driving deep water formation in a greenhouse world specifically we use cosmos to evaluate the impact of changes in the north atlantic gateways at the early middle eocene boundary on the north atlantic deep western boundary currents under low obliquity configuration we find that northern component waters start to form when the greenland scotland ridge reaches a threshold depth of deeper than 200 m while the arctic ocean is still shut off from the north atlantic in this scenario the relatively deep greenland scotland ridge allows for sufficient inflow of warm salty atlantic surface waters into the nordic seas to initiate convection during winter cooling opening the seaway towards the arctic leads to a cessation of northern component water formation as it allows for inflow of brackish surface waters into the northern nordic seas hindering northern component water formation

the paleocene eocene thermal maximum how much carbon is enough the paleocene eocene thermal maximum petm 55 53 million years before present was an abrupt warming event that involved profound changes in the carbon cycle and led to major perturbations of marine and terrestrial ecosystems the petm was triggered by the release of a massive amount of carbon and thus the event provides an analog for future climate and environmental changes given the current anthropogenic co2 emissions previous attempts to constrain the amount of carbon released have produced widely diverging results between 2000 and 10 000 gigatons carbon gtc here we use the uvic earth system climate model in conjunction with a recently published compilation of petm temperatures to constrain the initial atmospheric co2 concentration as well as the total mass of carbon released during the event thirty six simulations were initialized with varying ocean alkalinity river runoff and ocean sediment cover simulating various combinations of pre petm co2 levels 840 1680 and 2520 ppm and total carbon releases 3000 4500 7000 and 10 000 gtc we find that both the 840 ppm plus 7000 gtc and 1680 ppm plus 7000 10 000 gtc scenarios agree best with temperature reconstructions bottom waters outside the arctic and north atlantic oceans remain well oxygenated in all of our simulations while the recovery time and rates are highly dependent on ocean alkalinity and sediment cover the maximum temperature anomaly used here to constrain the amount of carbon released is less dependent on this slow acting feedback

diffusion of rare earth elements in fish teeth from deep sea sediments the distribution of rare earth elements rees in biogenic phosphate phases in sediments such as the remains of fish teeth has been proposed as an indicator of the depositional environment in the water column recording for example palaeo redox conditions1 and isotope geochemical2 5 and hydrothermal6 7 processes enrichment of these phases in rees takes place only during early diagenesis8 9 for which reason the ree signal has often been assumed to represent the unfractionated record of ree distribution in the water column overlying the sediment surface1 4 5 10 here we report on studies of ree zoning in fish teeth from pacific sediments from which we extract a ree diffusion coefficient of 70 mm2 myr 1 this value suggests that diffusion of rees from sea water into the fish teeth before burial is too slow to produce the enrichments observed instead the ree distributions must derive from the surrounding sediment pore fluids the use of these distributions as palaeoceanographic indicators is therefore called into question

stable isotope chemistry of fossil bone as a new paleoclimate indicator abstract during fossilization bone is thought to recrystallize and alter chemically on timescales of kyr to a few tens of kyr i e similar to the timescale for formation of soils therefore c and o isotope compositions of bone apatite should correlate with trends in soil water composition and aridity and serve as paleoclimate indicators this hypothesis was tested by analyzing c and o isotope compositions of the co 3 component of fossil bone apatite from mid oligocene through late pleistocene units in oregon and western idaho including the john day 19 4 30 0 ma mascall 15 2 15 8 ma and rattlesnake 7 2 7 8 ma formations whose paleosol sequences have been studied in detail and the juntura 10 11 ma hagerman 3 2 ma and fossil lake 18 o values provide a baseline of meteoric water compositions stable isotope compositions of bone co 3 do change in response to broad climatic trends but show poor correlation with compositions of corresponding paleosol co 3 at specific horizons instead compositional deviations between bone and paleosol co 3 correlate with compositional deviations with the next higher paleosol this suggests that the timescale for fossilization exceeds one paleosol cycle based on stratigraphic evidence and simple alteration models fossilization timescales are estimated at 20 50 kyr indicating that bone co 3 will prove most useful for sequences spanning 100 kyr c isotopes show negative and strong positive deviations during wet and dry climates respectively and short term trends correspond well with changes in aridity within the mascall and rattlesnake formations as inferred from paleosols a proposed correction to 18 o values based on 13 c anomalies implies a small 1 5 increase in meteoric water 18 o during the late oligocene global warming event consistent with a minimum temperature increase of 4 c a strong inferred decrease in 18 o of 4 5 after 7 ma closely parallels compositional changes in tooth enamel and reflects a doubling in the height of the cascade range

a high resolution record of atmospheric 14c based on hulu cave speleothem h82 abstract the development of a calibration of atmospheric radiocarbon 14c is a significant scientific goal because it provides the means to link the numerous 14c dated paleoclimate records to a common timescale with absolutely dated records and thereby improve our understanding the relationships between the carbon cycle and climate change currently few calibration datasets that directly sample the atmospheric 14c reservoir are available beyond the end of the dendro dated holocene tree ring record at 12 6 kyr bp before 1950 ad in the absence of suitable true atmospheric records 14c calibrations beyond this age limit are based largely on marine data that are complicated by the marine reservoir effect which may have varied over the glacial cycle in this paper we present a high resolution record of u th series and 14c measurements from hulu cave speleothem h82 spanning 10 6 26 8 kyr bp corrections for detrital 230th are negligible and the contribution of 14c free geologic carbon to the speleothem calcite is small 5 6 and is stable across major climate shifts the time series provides a 16 kyr record of atmospheric 14c as well as an updated age model for the existing hulu cave 18o record the 14c data are in good overall agreement with existing marine and terrestrial 14c records but comparisons with the cariaco basin marine 14c record through the deglacial interval reveal that the cariaco reservoir age appears to have varied during parts of the younger dryas and heinrich stadial 1 cold events this highlights the importance of developing extended high resolution marine and terrestrial 14c records as a means of detecting changes in ocean circulation over the glacial cycle

event layers in the japanese lake suigetsu sg06 sediment core description interpretation and climatic implications event layers in lake sediments are indicators of past extreme events mostly the results of floods or earthquakes detailed characterisation of the layers allows the discrimination of the sedimentation processes involved such as surface runoff landslides or subaqueous slope failures these processes can then be interpreted in terms of their triggering mechanisms here we present a 40 ka event layer chronology from lake suigetsu japan the event layers were characterised using a multi proxy approach employing light microscopy and xrf for microfacies analysis the vast majority of event layers in lake suigetsu was produced by flood events 362 out of 369 allowing the construction of the first long term quantitative with respect to recurrence and well dated flood chronology from the region the flood layer frequency shows a high variability over the last 40 ka and it appears that extreme precipitation events were decoupled from the average long term precipitation for instance the flood layer frequency is highest in the glacial at around 25 ka bp at which time japan was experiencing a generally cold and dry climate other cold episodes such as heinrich event 1 or the late glacial stadial show a low flood layer frequency both observations together exclude a simple straightforward relationship with average precipitation and temperature we argue that especially during glacial times changes in typhoon genesis typhoon tracks are the most likely control on the flood layer frequency rather than changes in the monsoon front or snow melts spectral analysis of the flood chronology revealed periodic variations on centennial and millennial time scales with 220 yr 450 yr and a 2000 yr cyclicity most pronounced however the flood layer frequency appears to have not only been influenced by climate changes but also by changes in erosion rates due to for instance earthquakes

late cretaceous climate in the canadian arctic multi proxy constraints from devon island abstract arctic climate in the late cretaceous has long been recognized to have been warm and wet relative to the present but quantitative assessments of paleoclimate have been challenging due in part to disagreements between proxies in marine and terrestrial environments this study provides a first multiproxy evaluation of late cretaceous 93 90 ma to 73 72 ma paleoclimate and paleohydrology from devon island in the canadian high arctic modern location 76 17 n 91 12 w late cretaceous location 71 30 n 24 30 w surface temperatures are reconstructed at 12 6 to 20 6 c for the ocean and 11 7 to 16 9 c over land using glycerol dialkyl glycerol tetraether gdgt based proxies measured from marine tex86 and terrestrial samples mbt 5me these proxies are likely skewed toward warm month temperatures based on novel analysis and interpretation of biomarkers in sediment and co occurring marine vertebrate coprolites the hydrogen isotopic composition 2h of precipitation is constrained to have varied from 123 to 82 vsmow using evidence from n alkanes likely derived from higher plants 18o of shelfal marine surface water is constrained to have been between 10 5 to 3 4 using phosphate oxygen isotopes of marine vertebrate teeth and coprolites from these marine salinity is modeled to have varied from 10 psu and 30 psu indicative of periodic freshwater influx these estimates indicate that large marine vertebrates lived and fed at least intermittently in near shore brackish waters finally the arctic was similarly warm in both the late cretaceous and paleocene eocene but the late cretaceous isotopic composition of precipitation at devon island was enriched in the heavy isotope of hydrogen by up to 60 to 70 relative to arctic eocene sites the combination of techniques used here reduces uncertainties related to the application of proxies to an environment without a modern analogue providing novel paleoclimatic constraints on the late cretaceous arctic region

a complete terrestrial radiocarbon record for 11 2 to 52 8 kyr b p radiocarbon 14c provides a way to date material that contains carbon with an age up to 50 000 years and is also an important tracer of the global carbon cycle however the lack of a comprehensive record reflecting atmospheric 14c prior to 12 5 thousand years before the present kyr b p has limited the application of radiocarbon dating of samples from the last glacial period here we report 14c results from lake suigetsu japan 35 35 n 135 53 e which provide a comprehensive record of terrestrial radiocarbon to the present limit of the 14c method the time scale we present in this work allows direct comparison of lake suigetsu paleoclimatic data with other terrestrial climatic records and gives information on the connection between global atmospheric and regional marine radiocarbon levels

skeletal and dermal armor reconstruction of euoplocephalus tutus ornithischia ankylosauridae from the late cretaceous oldman formation of alberta previously life reconstructions of ankylosaurid dinosaurs are incorrect in that they show uniformly shaped keeled plates arranged in neat longitudinal and transverse rows and large spines projecting laterally from the flanks of the body articulated armor of euoplocephalus tutus previously described as the types scolosaurus cutleri nopsca and dyoplosaurus acutosquameus parks from the late cretaceous oldman formation shows that armor shape and size varied considerably along neck back and tail an attempt is made to reconstruct the skeleton and arrangement of the dermal armor of euoplocephalus

environmental responses to lateglacial climatic fluctuations recorded in the sediments of pre alpine lake mondsee northeastern alps investigation of the sedimentary record of pre alpine lake mondsee upper austria focused on the environmental reaction to rapid lateglacial climatic changes results of this study reveal complex proxy responses that are variable in time and influenced by the long term evolution of the lake and its catchment a new field sampling approach facilitated continuous and precisely controlled parallel sampling at decadal to sub annual resolution for mu xrf element scanning carbon geochemistry stable isotope measurements on ostracods pollen analyses and large scale thin sections for microfacies analysis the holocene chronology is established through microscopic varve counting and supported by accelerator mass spectrometric 14 c dating of terrestrial plant macrofossils whereas the lateglacial age model is based on delta 18 o wiggle matching with the greenland ngrip record using the gicc05 chronology microfacies analysis enables the detection of subtle salimentological changes proving that depositional processes even in rather large lake systems are highly sensitive to climate forcing comparing periods of major warming at the onset of the lateglacial and holocene and of major cooling at the onset of the younger dryas reveals differences in proxy responses reflecting threshold effects and ecosystem inertia temperature increase vegetation recovery decrease of detrital flux and intensification of biochemical calcite precipitation at the onset of the holocene took place with only decadal leads and lags over a ca 100 a period whereas the spread of woodlands and the reduction of detrital flux lagged the warming at the onset of the lateglacial interstadial by ca 500 750a cooling at the onset of the younger dryas is reflected by the simultaneous reaction of delta 18 o and vegetation but sedimentological changes reduction of endogenic calcite content increase in detrital flux were delayed by about 150 300 a three short term lateglacial cold intervals corresponding to greenland isotope substages gl 1d gl 1c2 and gl 1b also show complex proxy responses that vary in time copyright c 2011 john wiley sons ltd

evolution of early cenozoic marine temperatures the equator to high southern latitude sea surface and vertical temperature gradients are reconstructed from oxygen isotope values of planktonic and benthic foraminifers for the following five time intervals late paleocene early eocene early middle eocene late eocene and early oligocene paleotemperatures are calculated using standard oxygen isotope temperature equations with adjustments to account for 1 variations in sea water 18o related to changes in global ice volume over time and 2 latitudinal gradients in surface water 18o these reconstructions indicate that sea surface temperatures sst of the southern oceans in the early eocene were as high as 15 c whereas temperatures during the late paleocene and early middle eocene reached maximum levels of 10 12 c by the late eocene and early oligocene high latitude sst had declined to 6 and 4 c respectively for most of the early paleogene low latitude sub tropical temperatures remained constant and well within the range of holocene temperatures 24 ndash 25 c but by the late eocene and early oligocene declined to values in the range of 18 to 22 c the late paleogene apparent decline in tropical temperatures however might be artificial because of dissolution of near surface foraminifera tests which biased sediment assemblages toward deeper dwelling foraminifera moreover according to recent plate reconstructions it appears that the majority of sites upon which the late eocene and early oligocene tropical temperatures were previously established were located either in or near regions likely to have been influenced by upwelling global deepwater temperature on average paralleled southern ocean sst for most of the paleogene we speculate based on the overall timing and character of marine sea surface temperature variation during the paleogene that some combination of both higher levels of greenhouse gases and increased heat transport was responsible for the exceptional high latitude warmth of the early eocene

effect of the deepening of the tasman gateway on the global ocean 1 we examine the effect of the deepening of the tasman seaway at the end of the eocene in a climate model with realistic late eocene bathymetry and winds for this we have constructed an eocene numerical model based on the university of victoria climate model with wind forcing derived from a fully coupled eocene simulation the model climate state is characterized by an oceanic meridional overturning circulation moc involving southern hemisphere sinking and a northward atmospheric moisture transport across the equator the deepening of the tasman seaway in the presence of an open drake passage and the associated establishment of the antarctic circumpolar current acc have a limited climatic impact on antarctica nonetheless the antarctic deep sinking regions cool sufficiently to lead to a global deep ocean cooling of 3 c no initiation of northern component water is found indicating that this may require the development of a more mature acc previous studies suggest that the ross sea gyre cools the east coast of australia and expected the deepening of the tasman seaway to lead to a warming east of australia due to the introduction of warmer water from the australo antarctic gulf we here find that this warming is limited to close to the australian coast and that widespread cooling prevails further off shore

late paleocene arctic ocean shallow marine temperatures from mollusc stable isotopes late paleocene high latitude 80 n arctic ocean shallow marine temperatures are estimated from molluscan 18o time series sampling of individual growth increments of two specimens of the bivalve camptochlamys alaskensis provides a high resolution record of shell stable isotope composition the heavy carbon isotopic values of the specimens support a late paleocene age for the youngest marine beds of the prince creek formation exposed near ocean point alaska the oxygen isotopic composition of regional freshwater runoff is estimated from the mean 18o value of two freshwater bivalves collected from approximately coeval fluviatile beds over a 30 34 range of salinity values assumed to represent the tolerance of c alaskensis the mean annual shallow marine temperature recorded by these individuals is between 11 and 22 c these values could represent maximum estimates of the mean annual temperature because of a possible warm month bias imposed on the average 18o value by slowing or cessation of growth in winter months the amplitude of the molluscan 18o time series probably records most of the seasonality in shallow marine temperature the annual temperature range indicated is approximately 6 c suggesting very moderate high latitude marine temperature seasonality during the late paleocene on the basis of analogy with modern chlamys species c alaskensis probably inhabited water depths of 30 50 m the seasonal temperature range derived from 18o is therefore likely to be damped relative to the full range of annual sea surface temperatures high resolution sampling of molluscan shell material across inferred growth bands represents an important proxy record of seasonality of marine and freshwater conditions applicable at any latitude if applied to other regions and time periods the approach used here would contribute substantially to the paleoclimate record of seasonality

identification of the changbaishan millennium b tm eruption deposit in the lake suigetsu sg06 sedimentary archive japan synchronisation of hemispheric wide palaeoclimate archives the b tm tephra dispersed during the highly explosive changbaishan millennium eruption ca 940 950 ce and a key marker layer within the greenland ice cores has now been identified in the lake suigetsu sg06 sedimentary sequence central japan the major element geochemistry of the volcanic glasses within this tephra layer are compared to a new glass dataset from the distal type locality tomakomai port hokkaido and other published millennium eruption b tm deposits to verify this correlation the discovery of the b tm tephra in the lake suigetsu record provides to date the most southerly identification of this ash and crucially the first direct tie point between this high resolution mid latitude palaeoclimate archive and the greenland ice cores these findings present significant encouragement for on going research into the tephrostratigraphy of east asia focusing on the identification of widely dispersed tephra layers which can facilitate the synchronisation of disparate palaeoclimate archives and thus enable the assessment of spatio temporal variations in past climatic change

a molybdenum isotope record of eocene thermal maximum 2 implications for global ocean redox during the early eocene during the early eocene a series of short term global warming events hyperthermals occurred in response to the rapid release of carbon into the oceans and atmosphere in order to investigate the response of ocean redox to global warming we have determined the molybdenum isotope compositions 98 95 mo of samples spanning one such hyperthermal eocene thermal maximum 2 etm 2 54 1ma from integrated ocean drilling program expedition 302 site m0004a in the arctic ocean the highest 98 95 mo in our sample set 2 00 0 11 corresponds to the development of local euxinia at site m0004a during the peak of etm 2 which we interpret as recording the global seawater 98 95 mo at that time the etm 2 seawater 98 95 mo is indistinguishable from a recent estimate of seawater 98 95 mo from an earlier hyperthermal paleocene eocene thermal maximum petm 55 9ma 98 95 mo 2 08 0 11 it is argued that the similarity in seawater 98 95 mo during etm 2 and the petm was caused by the development of transient euxinia in the arctic ocean during each hyperthermal that allowed sediments accumulating in this basin to capture the long term 98 95 mo of early eocene seawater our new data therefore place a minimum constraint on the magnitude of transient global seafloor deoxygenation during early eocene hyperthermals

8786sr phytoplankton and the nature of the late cretaceous and early cenozoic arctic ocean abstract the arctic ocean s link to the lower latitude world ocean during the late cretaceous and early cenozoic is puzzling the tectonic development of the arctic ocean evidently included termination of the pacific arctic connection late in the cretaceous and the atlantic link was not significant until at least the eocene yet during the late cretaceous arctic ocean mollusks indicate that there was no more than partial restriction and late cretaceous and middle eocene phytoplankton species are the same in both the arctic and world ocean sr isotope ratios of fish associated with the phytoplankton are higher than that accepted as the world ocean s ratios for any time during this interval yet these high ratios do not indicate an isolated arctic basin the arctic was linked with the world ocean and the best evidence for this is the phytoplankton similarity but the location of the marine connection remains enigmatic

episodic fresh surface waters in the eocene arctic ocean it has been suggested on the basis of modern hydrology and fully coupled palaeoclimate simulations that the warm greenhouse conditions that characterized the early palaeogene period 55 45 myr ago probably induced an intensified hydrological cycle with precipitation exceeding evaporation at high latitudes little field evidence however has been available to constrain oceanic conditions in the arctic during this period here we analyse palaeogene sediments obtained during the arctic coring expedition showing that large quantities of the free floating fern azolla grew and reproduced in the arctic ocean by the onset of the middle eocene epoch approximately 50 myr ago the azolla and accompanying abundant freshwater organic and siliceous microfossils indicate an episodic freshening of arctic surface waters during an approximately 800 000 year interval the abundant remains of azolla that characterize basal middle eocene marine deposits of all nordic seas probably represent transported assemblages resulting from freshwater spills from the arctic ocean that reached as far south as the north sea the termination of the azolla phase in the arctic coincides with a local sea surface temperature rise from approximately 10 degrees c to 13 degrees c pointing to simultaneous increases in salt and heat supply owing to the influx of waters from adjacent oceans we suggest that onset and termination of the azolla phase depended on the degree of oceanic exchange between arctic ocean and adjacent seas

quantitative pollen based climate reconstruction in central japan application to surface and late quaternary spectra abstract climate reconstruction in japan by the best modern analogues method was tested with 285 surface pollen spectra and then applied to the 47 000 years pollen profile from lake mikata central japan both pollen taxa percentages and plant functional type affinity scores were used in the reconstruction of six climate variables the reconstructed values were compared with the estimated modern climate at each surface pollen site in order to evaluate the accuracy of the pollen based reconstruction the reconstruction of thermal parameters is very reliable correlation coefficient r between 0 86 and 0 89 the reconstruction of annual precipitation is less accurate r 0 7 we also proposed a new technique to calibrate reconstructed values into both probability distribution and or confidence regions of observed values the specialized programs for this calibration polcalib and polhist are available at qsr website http www elsevier nl locate quascirev the reconstruction of the late quaternary climate changes around lake mikata shows that the summer and winter temperatures were 5 c lower than present around 40 uncal kyr bp reached a minimum around 20 uncal kyr bp 10 c lower than present and became similar to present day at 8 uncal kyr bp the estimates for annual precipitation show that it was driest around 20 uncal kyr bp

could changing ocean circulation have destabilized methane hydrate at the paleocene eocene boundary 1 during the paleocene eocene thermal maximum petm 55 ma marine and terrestrial carbon isotope values exhibit a negative shift of at least 2 5 indicative of massive destabilization of marine methane hydrates releasing 2000 gigatons of methane carbon the cause of the hydrate destabilization is unknown but has been speculated to be warming due to a change from high latitude to low latitude deepwater formation here we present results from a numerical ocean model indicating that a sudden switch of deepwater formation from southern to northern high latitudes caused middepth and deep ocean warming of 3 5 c the switch is caused by a slow increase in the intensity of the atmospheric hydrologic cycle as expected under increasing temperatures and consistent with petm sedimentary evidence deepened subtropical subduction prior to the thermohaline circulation switch causes warming of 1 4 c in limited areas at thermocline through upper intermediate depths which could destabilize methane hydrates gradually and at progressively greater depths warming accompanying a south to north switch in deepwater formation would produce sufficient warming to destabilize seafloor gas hydrates over most of the world ocean to a water depth of at least 1900 m

onset and termination of the late glacial climate reversal in the high resolution diatom and sedimentary records from the annually laminated sg06 core from lake suigetsu japan high resolution diatom sediment and pollen analyses of two sections from the annually laminated sg06 core from lake suigetsu were used to study the onset and termination of the late glacial climate reversal in central japan its broadly recognised counterpart is the younger dryas or greenland stadial 1 ca 12 85 11 65 cal kyr bp based on the ngrip ice core records our study suggests that accumulation of the analysed late glacial sediments occurred in a deep and relatively cold water meso eutrophic lake with a strong mixing regime and relatively high silica content combining these results together with available pollen based environmental reconstructions we suggest that climate cooling together with an intensified winter monsoon and thicker snow cover could influence changes in regional vegetation sedimentation processes and trophic status of the lake during the transition from the last interstadial to stadial around lake suigetsu a decrease in total pollen concentration and increase in fagus pollen percentage indicate local vegetation stress disturbances and suggest that cooling started at least 2 3 decades prior to the major shift in the inorganic sediment accumulation of detrital layers and in diatom assemblages change from aulacoseira ambigua to aulacoseira subarctica dominance which took about 10 years the transition from the last stadial to the holocene again shows that vegetation in the lake catchment area reacted first to the regional climate change i e to the weakening of the winter monsoon and decrease in winter snow accumulation the increase in the vegetation cover density and reduced volume of surface runoff associated with the decrease in melt water supply is likely responsible for the reduced soil erosion activity which caused the cessation in detrital layer accumulation and consequent decrease in the amount of nutrients brought to the lake and lowering of the water nutrient status the latter process finally influenced changes in the diatom assemblages including the return to dominance of a subarctica ca 30 years after the virtual disappearance of detrital layers from the sediment our results demonstrate the rapid response of the lake suigetsu system to the global cooling and subsequent warming and allow clear definition of the onset and termination of the late glacial climate reversal despite the fact that the lake system shows a more abrupt shift from the warm to cold and cold to warm environments than terrestrial records of vegetation demonstrate we do not see any delayed response of local vegetation to the climate change this last conclusion is of particular importance for application of the sg06 pollen record for quantitative climate reconstruction

annually dated late weichselian continental paleoclimate record from the eifel germany a record extending back to 23 220 calendar yr b p was obtained from varved sediments from lake holzmaar germany by applying multiple dating methods and interlake comparison with meerfelder maar variations in the weichselian inorganic carbon content resulting from intensified eolian activities coincide with proxy parameters of dust accumulation in greenland the timing for the end of the last glacial maximum at holzmaar agrees with the greenland ice sheet project gisp2 data but suggests dating discrepancies with the greenland ice core project data grip assuming that periods of maximum dust deposition in the eifel and greenland coincide with ice advances in northeastern germany the holzmaar record provides a means of dating three late weichselian terminal moraines

paleoenvironmental implications of cenozoic sediments from the central arctic ocean iodp expedition 302 using inorganic geochemistry 1 integrated ocean drilling program iodp expedition 302 arctic coring expedition acex recovered a unique sediment record from the central arctic ocean revealing that this region underwent major environmental fluctuations since the late cretaceous major and trace element composition of 1 300 samples were determined using x ray fluorescence xrf the results show significant compositional variability of the sediments with depth that can be attributed to changes in a provenance and pathways of detrital material b paleoenvironmental conditions and depositional processes and c diagenetic overprint of the primary record in addition to existing lithological units we introduce new geochemical units for a more process related approach interpreting the acex record in detail via the geochemical signature of siberian flood basalts we are able to reconstruct the discontinuous rifting and deepening of the central lomonosov ridge during the paleogene accompanied by changing current regimes and the onset of sea ice eocene biosiliceous sedimentation took place in a relatively shallow setting under predominantly anoxic bottom water conditions causing a positive anoxia productivity feedback although water column stratification was repeatedly interrupted by ventilation events anoxic to sulfidic conditions were even more extreme after biosilica production ceased and significant amounts of pyrite were deposited on the lomonosov ridge especially in organic matter rich paleogene deposits diagenetic processes obscured the paleoenvironmental signals fundamental environmental changes occurred in the middle eocene but geochemical and micropaleontological proxies point not to the identical sediment depth after approximately 26 ma of non deposition or erosion the middle miocene record shows the transition to dominantly oxic bottom water conditions although suboxic diagenesis seemingly affected these deposits

synchronous radiocarbon and climate shifts during the last deglaciation radiocarbon data from the cariaco basin provide calibration of the carbon 14 time scale across the period of deglaciation 15 000 to 10 000 years ago with resolution available previously only from holocene tree rings reconstructed changes in atmospheric carbon 14 are larger than previously thought with the largest change occurring simultaneously with the sudden climatic cooling of the younger dryas event carbon 14 and published beryllium 10 data together suggest that concurrent climate and carbon 14 changes were predominantly the result of abrupt shifts in deep ocean ventilation

cenozoic deep sea temperatures and global ice volumes from mg ca in benthic foraminiferal calcite a deep sea temperature record for the past 50 million years has been produced from the magnesium calcium ratio mg ca in benthic foraminiferal calcite the record is strikingly similar in form to the corresponding benthic oxygen isotope 18o record and defines an overall cooling of about 12 c in the deep oceans with four main cooling periods used in conjunction with the benthic 18o record the magnesium temperature record indicates that the first major accumulation of antarctic ice occurred rapidly in the earliest oligocene 34 million years ago and was not accompanied by a decrease in deep sea temperatures

sg06 a fully continuous and varved sediment core from lake suigetsu japan stratigraphy and potential for improving the radiocarbon calibration model and understanding of late quaternary climate changes abstract the high potential of the varved sediments of lake suigetsu central japan to provide a purely terrestrial radiocarbon calibration model and a chronology of palaeoclimatic changes has been widely recognised for the last two decades however this potential has not been fully realised since the only available long sediment core from the lake sg93 was extracted from a single bore hole and was therefore interrupted by gaps of unknown duration between successive core sections in the summer of 2006 a new sediment core sg06 was recovered from the lake four separate boreholes were drilled and the parallel sets of cores recovered were found to overlap completely without gaps between segments this new record provides the ability to test existing atmospheric radiocarbon calibration models as well as to assess the scale of inter regional leads and lags in palaeoclimatic changes over the last glacial interglacial cycle multi disciplinary analyses from sg06 are still ongoing but a reliable description of the sedimentary sequence needs to be provided to the wider science community before major outputs from the project are released thereby allowing fully informed critical evaluation of all subsequent releases of data based on the sg06 record in this paper we report key litho stratigraphic information concerning the sg06 sediment core highlighting changes in the clarity of annual laminations varves with depth and possible implications for the mechanism of the climate change we also discuss the potential of the sg06 record to meet the fundamental goals of the inqua intimate project