characteristics of mud diapirs and mud volcanoes and their relationship to oil and gas migration and accumulation in a marginal basin of the northern south china sea mud diapir and mud volcano have the same formation mechanism and similar development and evolution characteristics but different geological features and forms in this study the development and characteristics of a mud diapir in yinggehai basin northwestern south china sea and a mud volcano in southwest taiwan basin northeastern south china sea were investigated the geochemical characteristics of their associated natural gases were also analyzed the results indicated that the yinggehai basin mud diapir is mainly distributed in the deep and large depression of the central basin and presents five lines in echelon arrangement along a northwest direction its development and evolution characteristics are low density and speed and abnormally high temperature and overpressure in contrast the southwest taiwan basin mud volcano is mainly distributed in a deep water slope area of the south sag and tainan kaohsiung onshore mud volcanoes are mainly distributed along the deep and large fault zone and their morphological characteristics are similar to venting volcanoes the seabed morphology of offshore mud volcano seems similar but current research is still insufficient there are many types of associated hydrocarbon gases in mud diapir and mud volcano but the high maturity coal type hydrocarbon gas is the main one the associated non hydrocarbon gas is rich in co2 and n2 which is mainly derived from a co2 source from inorganic crust the source of both diapir and volcano is thick marine miocene and pliocene age mud with hydrocarbon generating potential the mature hydrocarbon generation mud diapir mud volcano migration and deposition into an appropriate reservoir as well as diapir associated structures constitute a unique oil gas migration and accumulation system which thus adds to our understanding of the distribution of such mud diapir volcano type oil gas reservoir

holocene climatic and environmental changes inferred from midge records diptera chironomidae chaoboridae ceratopogonidae at lake berkut southern kola peninsula russia a radiocarbon dated sediment sequence from lake berkut in the southern part of the kola peninsula northwest russia was investigated by means of midge analysis in order to reconstruct the holocene climatic and environmental history of the region past mean july air temperatures at the study site and hypolimnetic oxygen contents of the lake water were inferred from chironomid based transfer functions the early holocene c 10 100 8400 cal yr bp is characterized by summer temperatures and hypolimnetic oxygen concentrations broadly similar to present day conditions the midge records give evidence of a lake level fall at c 7000 cal yr bp resulting in weakened thermal stratification of the lake water and improvement of the hypolimnetic oxygen conditions after c 4000 cal yr bp midge assemblages suggest a lake level rise related to increased effective moisture a secondary mid holocene climatic optimum with inferred mean july air temperatures of c 12 1 degrees c was recorded between 6000 and 4400 cal yr bp followed by minimum values c 11 3 degrees c between 3500 and 1500 cal yr bp accompanied by the onset of natural acidification of the lake the late holocene midge assemblages suggest weakly acidic conditions low hypolimnetic oxygen contents and a general warming trend during the last c 1500 years although paludification and natural acidification may have influenced the temperature reconstruction at this stage however the modern chironomid inferred mean july air temperature 12 5 degrees c is consistent with meteorological data from a nearby station in general the midge records reflect relatively warm and moist conditions at lake berkut before c 7000 cal yr bp a relatively warm and dry climate at c 7000 4000 cal yr bp and a shift to cooler and wetter climatic conditions in the region after c 4000 cal yr bp less

thermal anomaly profiles inferred from fluid inclusions near extensional and strike slip faults of the liaodong bay subbasin bohai bay basin china implications for fluid flow and the petroleum system abstract different types of faulting may greatly impact the flow of hot fluids and related thermal anomalies which may substantially affect the migration and accumulation of petroleum however little is known about the effects of fault types in this study 64 core samples were collected from localities controlled by extensional and strike slip faults in the liaodong bay subbasin bohai bay basin and fluid inclusions in these samples were used as thermal indicators of paleo fluids the results show strong thermal anomalies near the extensional and strike slip faults due to the flow of hot fluids the highest anomalies were recorded at localities proximal to the faults 134 4 c at a distance of 375 m from an extensional fault and 145 5 c at a distance of 262 5 m from the strike slip fault however these anomalies are all local and decrease with increasing distance from the faults up to a maximum distance of approximately 3000 m compared with those near the strike slip fault the anomalies near the extensional faults decrease more slowly and typically exhibit higher anomalies at similar distances which indicates that the extensional faults are better pathways for the flow of hot fluids the thermal effects of hot fluids have enhanced the maturation of organic matter and shifted the threshold depth for petroleum generation upward by approximately 300 m such effects on source rock maturation decrease with increasing distance from the faults up to a maximum distance of approximately 3000 m most ro values near the extensional faults are clearly higher than those near the strike slip fault thus the extensional faults play a more efficient role in the enhancement of source rock maturation and are interpreted as preferential pathways for the migration of generated hydrocarbons in the liaodong bay subbasin

timing of lateglacial vegetation dynamics and respective palaeoenvironmental conditions in southern estonia evidence from the sediment record of lake nakri this paper investigates a detailed well dated lateglacial floristic colonisation in the eastern baltic area ca 14 000 9000 cal a bp using palynological macrofossil loss on ignition and 14c data during 14 000 13 400 cal a bp primarily treeless pioneer tundra vegetation existed tree birch betula sect albae macro remains and a high tree pollen accumulation rate indicate the presence of forest tundra with birch and possibly pine pinus sylvestris l trees during 13 400 12 850 cal a bp palaeobotanical data indicate that the colonisation and development of forested areas were very rapid arising within a period of less than 50 years thus far there are no indications of conifer macrofossils in estonia to support the presence of coniferous forests in the lateglacial period signs of greenland interstadial 1b cooling during 13 100 cal a bp are distinguishable biostratigraphic evidence indicates that the vegetation was again mostly treeless tundra during the final colder episode of the lateglacial period associated with greenland stadial 1 approximately 12 850 11 650 cal a bp this was followed by onset of the holocene vegetation with the expansion of boreal forests in response to rapid climatic warming copyright 2011 john wiley sons ltd

composition and exhalation flux of gases from mud volcanoes in taiwan many mud volcanoes are distributed along the tectonic sutures in southern taiwan and can be divided into five zones based on their relative positions in different tectonic domains most active mud volcanoes are exhaling methane dominated gases nevertheless some gases show unusual carbon dioxide dominated and or nitrogen excess compositions this implies that there are multiple sources for the gas compositions of mud volcanoes in taiwan

central european vegetation response to abrupt climate change at 8 2 ka oxygen isotope records show a major climatic reversal at 8 2 ka in greenland and europe annually laminated sediments from two lakes in switzerland and germany were sampled contiguously to assess the response of european vegetation to climate change ca 8 2 ka with time resolution and precision comparable to those of the greenland ice cores the pollen assemblages show pronounced and immediate responses 0 20 yr of terrestrial vegetation to the climatic change at 8 2 ka a sudden collapse of corylus avellana hazel was accompanied by the rapid expansion of pinus pine betula birch and tilia linden and by the invasion of fagus silvatica beech and abies alba fir vegetational changes suggest that climatic cooling reduced drought stress allowing more drought sensitive and taller growing species to out compete corylus avellana by forming denser forest canopies climate cooling at 8 2 ka and the immediate reorganization of terrestrial ecosystems has gone unrecognized by previous pollen studies on the basis of our data we conclude that the early holocene high abundance of c avellana in europe was climatically caused and we question the conventional opinion that postglacial expansions of f silvatica and a alba were controlled by low migration rates rather than by climate the close connection between climatic change and vegetational response at a subcontinental scale implies that forecasted global warming may trigger rapid collapses expansions and invasions of tree species

an expanded calibration model for inferring lakewater and air temperatures from fossil chironomid assemblages in northern fennoscandia chironomid temperature inference models based on an expanded data set of surface sediment and limnological data from 53 subarctic lakes in northern fennoscandia have been developed using eight different numerical techniques each based on slightly different underlying statistical models or ecological assumptions the study sites are mostly small shallow bathymetrically simple oligotrophic lakes with a ph range from 5 0 to 7 8 a total organic carbon range from 2 5 to 12 6 mg l 1 a mean july lakewater temperature ranging from 6 1 to 15 4 c and a mean july air temperature ranging from 8 5 to 14 9 c a series of redundancy analyses rda identified sediment organic content maximum lake depth and lakewater temperature as being the most important explanatory variables variance partitioning by partial rdas further suggested that each of these variables accounted for a significant fraction of variance independent from each other different cali bration models were assessed on the basis of their statisti

the nature and hydrogeologic significance of mud diapirs and diatremes for accretionary systems in accretionary wedges often morphologically similar sedimentary intrusions when observed by remote geophysical means may have one of two quite different driving mechanisms and a highly variable significance for the regional hydrogeologic picture for example mud diapirs are driven by buoyancy forces that arise from bulk density contrasts in them mud and pore fluid upwell en masse and fluid migration is a related sometimes important but generally subsidiary process in contrast diatremes contain sediments fluidized during rapid fluid advection and are forcibly and directly driven by the hydrogeologic system the nature of fluid input from local and exotic source regions can therefore strongly affect sedimentary intrusive processes and vice versa this complicates the process of defining the main features of the hydrogeological systems operating in accretionary wedges focused vertical advection through steep sided piercement mud diapirs requires conduit systems otherwise flow will be diffuse and directed more horizontally out of the low permeability mud mass however where the permeability of the overburden is less than that of the diapir the whole diapir may act as a conduit apart from this special case conduits will be associated with highly anisotropic scaly fabrics that can sometimes develop in the marginal shear zone of diapirs scaly fabrics form during deformation and compaction of a mud matrix under conditions of constant or increasing effective stress however the effective stress path can be complex as it is both controlled by the relative rates of upward intrusion and burial by sedimentation and or structural thickening and the hydrogeologic system due to this it appears likely that even in a geographically related group of diapirs effective stress histories will vary widely between intrusions so that some can form advective pathways for fluids and some cannot mixed systems of behavior may also be present with local diatremes developing within diapirs above the terminations of conduit systems and rapidly expanding methane gas pockets the potentially heterogeneous near surface behavior may be why the surface manifestations of sedimentary intrusions are so variable when observed in the field diatremes can also form separately as large primary features above any structural or stratigraphic conduit that rapidly expels water or gas into the base of an unlithified sediment column when active large diatremes require enormous quantities of fluid water or gas to drive them particularly if they are long lived features and hence are a direct indication of at least an episodically vigorous hydrogeologic system

carbon and oxygen isotope composition of carbonate in bulk sediment in the southwest taiwan basin south china sea methane hydrate decomposition history and its link to mud volcano eruption abstract anaerobic oxidation of methane aom coupled with sulfate reduction sr generates authigenic carbonate which has the unique carbon and oxygen isotope composition in sulfate methane transition zone smtz the carbon and oxygen isotope composition of carbonate in sediments which can be used to revel the variable methane flux is affected by the percentage of aom driven carbonate in sediments to investigate the methane hydrate decomposition history in the southwest taiwan basin we analyzed a 13 m long sediment core for grain size carbonate and elemental carbon contents and stable carbon and oxygen isotopes composition of carbonate 13ccarb and 18ocarb the ams 14c dating results and carbonate content reveal that a turbidity current occurred at around 14 ka b p which reversed sediment accumulation between 455 and 885 cm in depth combining the chronological framework and 13ccarb values we identified that the methane hydrate decomposition scale began to decrease at 14 ka b p moreover we discovered that three transiently enhanced methane hydrate decomposition events occurred from then on although the 13ccarb and 18ocarb variability are as expected the low 18ocarb values are inconsistent with the previous theory which favors 18o enriched in aom driven authigenic carbonate thus we suggest that a large amount of 18o depleted water which originally migrated from southwest taiwan island was injected into surface sediment along with the eruption of mud volcanos as the terminal electron accepter of aom sr reaction the exogenous 18o depleted water leads its special oxygen isotope to be inherited by the authigenic aom driven carbonate the proposed theory provides new insights on the authigenic carbonate in methane hydrate area and the association between methane hydrates and mud volcanoes

fluid flow in and around a mud volcano field seaward of the barbados accretionary wedge results from manon cruise a field of mud diapirs and mud volcanoes situated in the barbados trench at 13 50 n and extending along an old oceanic fracture zone mercurus was investigated during the manon cruise using both surface ship and nautile submersible sampling and measurements the entire zone from 13 50 n up to 14 20 n has an anomalously high heat flow which implies that fluids are drained into it from a segment of the accretionary wedge a few hundred kilometers wide two structures interpreted as diatremes atalante and cyclops expell large amounts of water and methane we propose that they were formed from the release of a light fluid when gas hydrates were dissociated in the sediment as the result of the circulation of warm fluid in the area however they expell only a small fraction of the incoming fluid implying that disperse flow is the dominant mode of expulsion in this area the chemoautotrophic communities on the surface of the structures rely mostly on sulfides submersible observations temperature measurements in the sediment and the chemistry of the pore fluid indicate that convection of seawater occurs within the first few meters of sediment through high permeability channels such as cemented carbonate conduits we propose that this convection is driven by the density difference between the pore fluid and seawater but fresh water released by the dissolution of shallow hydrates may also contribute this shallow convection may be a frequent process in cold seep environments

reconstruction of late glacial summer temperatures from chironomid assemblages in lac lautrey jura france a chironomid july air temperature inference model based on chironomid assemblages in the surface sediments of 81 swiss lakes was used to reconstruct late glacial july air temperatures at lac lautrey jura eastern france the transfer function was based on weighted averaging partial least squares wa pls regression and featured a leave one out cross validated coefficient of determination r2 of 0 80 a root mean square error of prediction rmsep of 1 53 c and was applied to a chironomid record consisting of 154 samples covering the late glacial period back to the oldest dryas the model reconstructed july air temperatures of 11 12 c during the oldest dryas increasing temperatures between 14 and 16 5 c during the bolling temperatures around 16 5 17 0 c for most of the allerod temperatures of 14 15 c during the younger dryas and temperatures of ca 16 5 c during the preboreal the lac lautrey record features a two step july air temperature increase after the oldest dryas with an abrupt temperature increase of ca 3 3 5 c at the oldest dryas bolling transition followed by a more gradual warming between ca 14 200 and 13 700 bp the transfer function reconstructs a less rapid cooling at the allerod younger dryas transition than other published records possibly an artefact caused by the poor analogue situation during the earliest younger dryas and an abrupt warming at the younger dryas holocene transition during the allerod two centennial scale 1 5 2 0 c coolings are apparent in the record although chronologically not well constrained the first of these cold events may be synchronous with the beginning of the gerzensee oscillation the second is inferred just before deposition of the laachersee tephra at lac lautrey and is therefore coeval with the end of the gerzensee oscillation in contrast to the greenland oxygen isotope records the lac lautrey palaeotemperature reconstruction lacks a clearly defined greenland interstadial gi event 1d and the decreasing temperature trend during the bolling allerod interstadial copyright 2005 john wiley sons ltd

younger dryas and allerod summer temperatures at gerzensee switzerland inferred from fossil pollen and cladoceran assemblages linear and unimodal based inference models for mean summer temperatures partial least squares weighted averaging and weighted averaging partial least squares models were applied to a high resolution pollen and cladoceran stratigraphy from gerzensee switzerland the time window of investigation included the allerod the younger dryas and the preboreal characteristic major and minor oscillations in the oxygen isotope stratigraphy such as the gerzensee oscillation the onset and end of the younger dryas stadial and the preboreal oscillation were identified by isotope analysis of bulk sediment carbonates of the same core and were used as independent indicators for hemispheric or global scale climatic change in general the pollen inferred mean summer temperature reconstruction using all three inference models follows the oxygen isotope curve more closely than the cladoceran curve the cladoceran inferred reconstruction suggests generally warmer summers than the pollen based reconstructions which may be an effect of terrestrial vegetation not being in equilibrium with climate due to migrational lags during the late glacial and early holocene allerod summer temperatures range between 11 and 12 c based on pollen whereas the cladoceran inferred temperatures lie between 11 and 13 c pollen and cladocera inferred reconstructions both suggest a drop to 9 10 c at the beginning of the younger dryas although the allerod younger dryas transition lasted 150 160 years in the oxygen isotope stratigraphy the pollen inferred cooling took 180 190 years and the cladoceran inferred cooling lasted 250 260 years the pollen inferred summer temperature rise to 11 5 12 c at the transition from the younger dryas to the preboreal preceded the oxygen isotope signal by several decades whereas the cladoceran inferred warming lagged major discrepancies between the pollen and cladoceran inference models are observed for the preboreal where the cladoceran inference model suggests mean summer temperatures of up to 14 15 c both pollen and cladoceran inferred reconstructions suggest a cooling that may be related to the gerzensee oscillation but there is no evidence for a cooling synchronous with the preboreal oscillation as recorded in the oxygen isotope record for the gerzensee oscillation the inferred cooling was ca 1 and 0 5 c based on pollen and cladocera respectively which lies well within the inherent prediction errors of the inference models

quantification of biotic responses to rapid climatic changes around the younger dryas a synthesis to assess the presence or absence of lags in biotic responses to rapid climatic changes we 1 assume that the 18o in biogenically precipitated carbonates record global or hemispheric climatic change at the beginning and at the end of the younger dryas without any lag at our two study sites of gerzensee and leysin switzerland 2 derive a time scale by correlating the 18o record from these two sites with the 18o record of the grip ice core 3 measure 18o records in ostracods and molluscs to check the record in the bulk samples and to detect possible hydrological changes 4 analyse at gerzensee and leysin as well as at two additional sites that lack carbonates and hence a 18o record pollen plant macrofossils chironomids beetles and other insects and cladocera 5 estimate our sampling resolution using the grip time scale for the isotope stratigraphies and the biostratigraphies and 6 summarise the major patterns of compositional change in the biostratigraphies by principal component analysis or correspondence analysis we conclude that at the major climatic shifts at the beginning and end of the younger dryas hardly any biotic lags occur within the sampling resolution of 8 30 years and that upland vegetation responded as fast as aquatic invertebrates we suggest that the minor climatic changes associated with the gerzensee and preboreal oscillations were weakly recorded in the biostratigraphies at the lowland site but were more distinct at higher altitudes individualistic responses of plant and animal species to climatic change may reflect processes in individuals e g productivity and phenology in populations e g population dynamics in spatial distributions e g migrations and in ecosystems e g trophic state we suggest that biotic responses may be telescoped together into relatively short periods 50 to 150 years perhaps disrupting functional interactions among species and thus destabilising ecosystems

a mid european decadal isotope climate record from 15 500 to 5000 years b p oxygen isotope ratios of precipitation delta18op inferred from deep lake ostracods from the ammersee southern germany provide a climate record with decadal resolution the record in detail shows many of the rapid climate shifts seen in central greenland ice cores between 15 000 and 5000 years before the present b p negative excursions in the estimated delta18op from both of these records likely reflect short weakenings of the thermohaline circulation caused by episodic discharges of continental freshwater into the north atlantic deviating millennial scale trends however indicate that climate gradients between europe and greenland changed systematically reflecting a gradual rearrangement of north atlantic circulation during deglaciation

rapid climate change during the weichselian lateglacial in ireland chironomid inferred summer temperatures from fiddaun co galway a lacustrine sediment core from fiddaun western ireland was studied to reconstruct summer temperature changes during the weichselian lateglacial this site is located close to the atlantic ocean and so is potentially sensitive to climatic changes associated with changes in ocean circulation the record comprising the end of the weichselian pleniglacial to the early holocene was analysed for fossil chironomids lithology and oxygen and carbon isotopes in the sedimentary carbonates these proxies clearly show rapid warming at the onset of the lateglacial interstadial relatively high summer temperatures during the interstadial pronounced cooling during the younger dryas and subsequent warming at the transition to the holocene chironomid inferred mean july air temperatures for the interstadial are 12 5 14 5 c 7 5 c for the younger dryas and 15 0 c for the early holocene furthermore this research provides evidence for at least two cold events during the interstadial these more moderate temperature oscillations can be correlated to greenland interstadial events 1b and 1d on the basis of the age depth model for the fiddaun sequence based on multiple proxies the first cold oscillation gi 1d was the more severe of the two in ireland

chironomid inferred late glacial summer air temperatures from lough nadourcan co donegal ireland western ireland located adjacent to the north atlantic and with a strongly oceanic climate is potentially sensitive to rapid and extreme climate change we present the first high resolution chironomid inferred mean july temperature reconstruction for ireland spanning the late glacial and early holocene lgit 15 10 ka bp the reconstruction suggests an initial rapid warming followed by a short cool phase early in the interstadial during the interstadial there are oscillations in the inferred temperatures which may relate to greenland interstadial events gi 1a e the temperature decrease into the stadial occurs in two stages this two stage drop can also be seen in other late glacial chironomid inferred temperature records from the british isles a stepped rise in temperatures into the holocene consistent with present day temperatures in donegal is inferred the results show strong similarities with previously published lgit chironomid inferred temperature reconstructions and with the ngrip oxygen isotope curve which indicates that the oscillations observed in the ngrip record are of hemispherical significance the results also highlight the influence of the north atlantic on the irish climate throughout the lgit copyright 2010 john wiley sons ltd

a late glacial chironomid record from hawes water northwest england this paper presents the results of a high resolution late glacial chironomid stratigraphy from hawes water a small carbonate lake in northern lancashire the samples were from a core taken from the terrestrialised margin of the present lake which represents an intermediate depth between the true littoral and the profundal the chironomid assemblage showed a high degree of sensitivity to both broad scale and short term temperature changes comparison with an existing proxy temperature record 18o for the site confirmed the presence of four temperature inversions within the late glacial interstadial a mean july air temperature inference model derived from acid soft water lakes in norway and svalbard was applied to the data despite the absence of carbonate lakes within the norwegian training set there was a close similarity between trends in estimated july air temperature and the 18o trace with a particularly strong correspondence in the periods of clay deposition this suggests that this model is highly robust the inferred maximum interstadial temperature was 13 4 c dropping initially to 7 5 c in the loch lomond stadial temperatures reach a maximum of nearly 10 c in this period cool for a short period before rising rapidly to 13 2 c at the start of the holocene these temperatures are similar to but slightly higher than those estimated for whitrig bog southeast scotland and lower than those inferred from coleopteran based models for sites in south wales

responses to rapid warming at termination 1a at gerzensee central europe primary succession albedo soils lake development and ecological interactions the transition from the oldest dryas to the bolling around 14 685 cal yr bp was a period of extremely rapid climatic warming from a single core of lake marl taken at gerzensee switzerland we studied the transition in stable isotopes of oxygen and carbon on bulk sediment and charophyte remains as well as on monospecific samples of ostracods after pisidium a in addition pollen chironomids and cladocera were analyzed the 18o record serves as an estimate of mean air temperature and by correlation to the one from ngrip in greenland it provides a timescale the timing of responses the statistically significant zone boundaries of the biostratigraphies are telescoped at the rapid increase of about 3 in 18o at the onset of bolling biotic responses may have occurred within sampling resolution 8 to 16 years although younger zone boundaries are less synchronous gradual and longer lasting responses include complex processes such as primary or secular succession during the late glacial interstadial of bolling and allerod two stronger and two weaker cool phases were found biological processes involved in the responses occurred on levels of individuals e g pollen productivity of populations increases or decreases immigration or extinction and on the ecosystem level species interactions such as facilitation or competition abiotic and biotic interactions include pedogenesis nitrogen fixation nutrient cycling catchment hydrology water chemistry of the lake and albedo controlled by the transition from tundra to forest for the swiss plateau this major change in vegetation induced a change in the mammal fauna which in turn led to changes in the tool making by paleolithic people

detection of gas migration from a deep source by the use of exploration 3d seismic data abstract periods of sustained gas seepage since mid miocene time is indicated in exploration 3d seismic data from the area of the sleipner fields in the north sea buried mounds suspected to be mud volcanoes may have been generated in association with gas migration in mid miocene time minor faults and fractures are present at the same horizon and the mud volcanoes seem to be distributed along some of these seismic chimneys indicate migration of gas from below this level through the faults and fractures and up to the seabed shallow gas accumulations in late pliocene sands above the mud volcanoes may be a result of the gas migration possible buried craters overlying seismic chimneys may have been generated in a period of sustained gas seepage followed by a less active period during which the craters have been buried a large depression at the seabed overlying seismic chimneys indicates a recent period of sustained gas seepage the gas is believed to have migrated from the sleipner gas reservoirs

the amphi atlantic oscillation a proposed late glacial climatic event a contribution to the north atlantic seaboard programme of igcp 253 termination of the pleistocene abstract numerous palaeoclimatic records from europe greenland and the north atlantic ocean provide evidence for a short term cooling event which preceded the younger dryas stadial of ca 11 10 ka bp the discovery of a similar event in eastern north america the killarney oscillation ko raised the possibility of a single pre younger dryas cooling event that affected the entire north atlantic seaboard this paper reviews evidence for the ko and other pre younger dryas events and discusses the basis for their correlation the informal name amphi atlantic oscillation is proposed as a collective term for the ko and events that correlate with it

summer temperature gradients in northwest europe during the lateglacial to early holocene transition 15 8 ka bp inferred from chironomid assemblages abstract we present a series of summer air temperature isotherm maps based on chironomid inferred temperatures from northwest europe covering the lateglacial and early holocene 15 8 ka bp these maps are the first of their kind and use data derived from 22 lateglacial sites and 34 early holocene sites the isotherms are generated by weighted spatial interpolation kriging the major patterns of chironomid inferred summer temperatures are spatially well resolved in both the lateglacial and early holocene the isotherm maps indicate that there was a strong west to east gradient during the lateglacial interstadial gi 1 due to the influence of thermohaline circulation in the regions bordering the north atlantic which diminishes eastwards a strong north to south temperature gradient is also apparent particularly in eastern regions influenced by the extent of the scandinavian ice cap peak temperatures are achieved early in the interstadial in the south of the region but occur towards the end of the interstadial in the north holocene warming varies spatially and temporally and is earliest in the south and east but later in the north and west during the period covered in our study maximum warmth is reached ca 10 ka bp the chironomid based lateglacial isotherm maps are compared with previously published isotherm maps from the same region based on beetle inferred temperatures while the trends shown in the two datasets are similar beetle inferred temperatures are often warmer than chironomid inferred temperatures this is especially marked in gi 1e and may be due to microclimatic effects causing the chironomids to underestimate air temperatures and or the beetles to over estimate air temperatures the spatial coherence between sites in both the lateglacial and early holocene suggest that the chironomid based temperature estimates are largely reliable although data testing suggests that estimates from southern scandinavia may be less reliable perhaps due to high topographical relief influencing local climate more data points are required particularly from northwest scotland southwest england and wales northeast france denmark finland and the baltic states to confirm trends and provide even coverage and a denser network of sites

chironomid inferred air temperatures from lateglacial and holocene sites in north west europe progress and problems abstract non biting midges insecta diptera chironomidae are now widely recognised as powerful biological proxies for inferring past climatic change in this paper the response of chironomid assemblages to lateglacial and holocene climatic change from sites in scotland and norway is discussed analyses have shown that midge assemblages have responded to major and minor climatic fluctuations during the last 15 000 yr such as the aegelsee oscillation gerzensee oscillation and younger dryas in the lateglacial and the thermal optimum little ice age and cooling events at 8 2 and 2 0 cal ka bp in the holocene in an attempt to quantify these and other climatic fluctuations a chironomid mean july air temperature inference model based on a modern calibration set of 109 lakes in norway and svalbard has been developed the 3 component weighted averaging partial least squares inference model performs well with a root mean squared error of prediction of 0 90 c and a maximum bias of 0 59 c both based on leave one out cross validation which is lower than chironomid temperature inference models developed in canada switzerland and finland however while temperature inference models perform well in the lateglacial the more subtle climatic changes of the holocene are more difficult to reconstruct because the likely temperature changes are close to the limits of the prediction errors of the existing models to address this problem future work is required to refine and develop the calibration set by further improving taxonomic resolution by adding more lakes to the calibration set and by investigating the influence of other environmental variables on chironomid distributions and abundances

multiple oscillations during the lateglacial as recorded in a multi proxy high resolution record of the moervaart palaeolake nw belgium this paper presents the results of multi disciplinary research carried out on the deposits of moervaart depression nw belgium one of the largest palaeolakes 25 km2 that existed during the lateglacial interstadial in nw europe the multi proxy study including physical organic matter and calcium carbonate magnetic susceptibility micromorphological botanical pollen macrofossils diatoms zoological ostracods molluscs chironomids and chemical analyses stable carbon and oxygen isotopes has resulted in a detailed reconstruction of the lateglacial landscape as well of the local conditions that prevailed in the lake itself a chronology of the record was provided by radiocarbon dating and comparison with radiocarbon dates of the nearby rieme site these yielded a good match with the regional biostratigraphy during the lateglacial vegetation and geomorphology of the landscape in general changed from a tundra landscape to a boreal forest the vegetation development however was interrupted by a number of cold reversals three centennial scale cold oscillations are present in the record 1 the so called older dryas corresponding to gi 1d in the greenland ice cores 2 a short and pronounced cold event during the early allerod which could be correlated to gi 1c2 and 3 a cooling event during the late allerod probably corresponding to the intra allerod cold period iacp or gi 1b the latter most likely was responsible for the disappearance of the moervaart palaeolake

chironomid inferred late glacial air temperatures at whitrig bog southeast scotland this paper presents the first chironomid inferred mean july air temperature reconstruction for the late glacial in britain the reconstruction suggests that the thermal maximum occurred early in the interstadial with temperatures reaching about 12 degreesc there was then a gradual downward trend to about 11 degreesc punctuated by four distinct cold oscillations of varying intensity at the beginning of the younger dryas mean july temperatures fell to about 7 5 degreesc but gradually increased to about 9 degreesc before a rapid rise at the onset of the holocene the chironomid inferred temperature curve agrees closely both in general trends and in detail with the grip ice core oxygen isotope curve the reconstructed temperatures are 2 4 degreesc lower than coleopteran inferred temperatures but are closer to those inferred from plant macrofossils and glacial equilibrium line altitudes during the younger dryas copyright c 2000 john wiley sons ltd

environmental and climatic changes in the jura mountains eastern france during the lateglacial holocene transition a multi proxy record from lake lautrey this paper presents a multi proxy reconstruction of the climatic and environmental changes during the last glacial interglacial transition as recorded by a sediment sequence from lake lautrey jura eastern france this reconstruction is based on analysis of pollen chironomid organic matter oxygen isotope mineralogical magnetic susceptibility and inferred lake level data at a high temporal resolution the chronology is derived using ams radiocarbon dates the position of the laacher see tephra lst and of correlation between the lautrey and grip oxygen isotope records this data set reveals a detailed sequence of environmental changes in the jura mountains from greenland stadial 2a to the early holocene biotic and abiotic indicators allow the recognition of major abrupt changes associated with the gs 2a gi 1e gi 1a gs 1 and gs 1 preboreal transitions and other minor fluctuations related to the cold events gi 1d gi 1b and the preboreal oscillation pbo they also suggest additional cooling spells at ca 14 550 and 14 350 cal yr bp intra bolling cold periods at ca 13 500 and ca 12 700 cal yr bp just before the gs 1 onset and at ca 11 350 cal yr bp just before the pbo as well as an intriguing brief warming episode within gs 1 at ca 12 080 cal yr bp summer temperature increased by ca 5 c at the start of gi 1e and by 1 5 3 c at the holocene onset while it decreased by ca 3 4 c at the beginning of gs 1 major changes in local hydrology and in seasonality appear to be also associated with the gs 2a gi 1e gi 1a gs 1 and gs 1 preboreal transitions pollen and abiotic indicators suggest a greater sensitivity of the vegetation cover to climatic oscillations during the first part of the lateglacial interstadial than during the second part after ca 13 700 cal yr bp when a closed forest had been restored in this area by contrast the restoration of forest cover took less than 300 yr after the end of gs 1 at the beginning of gi 1e and gs 1 no lag occurs within the sampling resolution of 20 50 yr in the responses of aquatic chironomids and terrestrial pollen ecosystems while at the onset of the holocene the response of the vegetation appears slightly delayed in comparison with that of the chironomid community finally the recognition of two successive tephra layers which were deposited just before the lst at ca 12 950 cal yr bp and which originated from le puy de la nugere massif central france provides an additional tephrochronological tool for correlation between lateglacial european sequences

subdecadal scale vegetation responses to a previously unknown late allerod climate fluctuation and younger dryas cooling at lake meerfelder maar germany lake meerfelder maar mfm is the northernmost western european sediment record with annual laminations across the younger dryas yd and the onset of the yd in the record of mfm has previously been defined as an increase in non arboreal pollen abundance at ca 12 680 varve a bp here we present a palynological record at unprecedented subdecadal resolution for mfm covering the allerod yd transition our results show a fluctuation in pollen accumulation rates pars before the onset of the yd with lower rates between ca 12 725 and 12 685 varve a bp the fluctuation in pars occurs simultaneous with a previously undescribed short fluctuation in sediment composition and varve thickness as well as with changes in biogeochemical proxies the combined evidence indicates signs of climatic instability ca 45 years before the onset of the yd the par records of betula and pinus furthermore show earlier and more abrupt changes at the onset of the yd than the percentage records do finally heliophilous herbaceous taxa show a delayed increase following the onset of the yd of ca 145 years this paper illustrates the potential to identify previously unrecognized climate variability and vegetation change when using subdecadal resolution analyses

a high resolution late glacial isotopic record from hawes water northwest england understanding of the impact of past climate change on the terrestrial environment requires the development of quantitative palaeotemperature indicators that can be readily measured at closely spaced stratigraphic intervals a high resolution oxygen isotopic record from hawes water lancashire uk reveals a degree of climatic instability that is greater than that recognised in previous isotopic studies of sites from the atlantic margin of northwest europe four oscillations in the late glacial interstadial before the onset of the younger dryas stadial are marked by sharp negative excursions in the 18o record of the carbonate sediments and accompanied by marked changes in chironomid populations and the pollen record the oscillations are interpreted as cold events they correlate with events recognised in marine and lacustrine temperature proxy records as well as the isotopic record from the greenland ice cores results suggest that there has been a significant change in lake water composition since the late glacial but it is argued that the hawes water isotopic record constrained by the results of a study of carbonate precipitation in the modern lake provides a quantitative record of late glacial temperature change the 7 c maximum temperature difference inferred from the isotopic data from the interstadial optimum to the younger dryas stadial and the magnitude of individual oscillations compare well with estimates from terrestrial coleopterid and marine diatom sea surface temperature records all are significantly greater than the independently calibrated 4 2 c change documented from a chironomid record from south scotland such differences need to be resolved if the impacts of climatic events are to be fully understood

mud volcanoes the most important pathway for degassing deeply buried sediments abstract this paper discusses the nature of the phenomenon of mud volcanism with respect to degassing of deeply buried sediments mud volcanoes are defined as geological structures and their main elements are described based on the nature of activity mud volcanoes are grouped in to three main types and the relationship between each type and corresponding morphological expression is discussed the presented up to date data of the world geographical distribution of mud volcanoes show that they approximate to 1800 individuals a detail overview of geological environments in which they occur helps to deduce some necessary conditions for mud volcano formation the basic mechanisms of mud volcano formation are discussed specifically the fluid pressure hypothesis and some triggering events are identified the most common investigation approach and some criteria for recognizing of a submarine mud volcano on side scan sonar records and seismic sections are given mud volcanism in the mediterranean ridge an accretionary complex and black sea abyssal plane a back ark basin with tectonic regime of extension are described as case studies to show variety in morphology and common factors in development of mud volcanoes the manifestation of continuous gas migration through mud volcanoes is clarified and the attempt made to quantify the gas release shows that mud volcanoes are one of the significant natural sources of atmospheric methane emitting a total amount of about 10 3 to 12 6 tg annually

early holocene temperature variability inferred from chironomid assemblages at hawes water northwest england this paper presents the first high resolution chironomid inferred mean july air temperature c it reconstruction for the early holocene from england the reconstruction is based on a core recovered from a terrestrialised carbonate bench at hawes water a small hard water lake in northwest england the record shows that temperatures rose rapidly after the younger dryas with temperatures reaching 14 0 c at the beginning of the holocene over millennial timescales the temperature record points to a slight rise in temperatures towards the top of the sequence at around 8000 years before the year 2000 b2k the trend is punctuated by a series of cool oscillations at 11 200 11 400 10 700 10 400 9300 and 8300 b2k and by a short period 11 300 to 10 250 b2k when temperatures were considerably warmer up to 14 9 c the five cool oscillations coincide with temperature reversals found elsewhere in the north atlantic region and in the greenland ice core records these cool events correlate well with both me

lateglacial summer temperatures in the northwest european lowlands a chironomid record from hijkermeer the netherlands lateglacial environments at hijkermeer northwest netherlands were reconstructed by means of chironomid diatom and pollen analyses diatom assemblages indicate that hijkermeer was a shallow oligo to mesotrophic lake during this period pollen assemblages reflect the typical northwest european lateglacial vegetation development and provide an age assessment for the record from the beginning of the older dryas ca 14 000 calibrated 14c yr bp into the early holocene to ca 10 700 calibrated 14c yr bp the chironomid record is characterized by several abrupt shifts between assemblages typically found in mid latitude subalpine to alpine lakes and assemblages typical for lowland environments based on the chironomid record july air temperatures were reconstructed using a chironomid temperature transfer function from central europe mean july air temperatures of ca 14 0 16 0 c are inferred before the older dryas of ca 16 0 16 5 c during most of the allerod of ca 13 5 14 0 c during the younger dryas and of ca 15 5 16 0 c during the early holocene two centennial scale decreases in july air temperature were reconstructed during the lateglacial interstadial which are correlated with greenland interstadial events gi 1d and 1b the results suggest that vegetation changes in the netherlands may have been promoted by the cooler climate during gi 1d immediately preceding the older dryas biozone and gi 1b the hijkermeer chironomid inferred temperature record shows a similar temperature development as the greenland ice core oxygen isotope records for most of the lateglacial and a good agreement with other temperature reconstructions available from the netherlands this suggests that chironomid based temperature reconstruction can be successfully implemented in the northwest european lowlands and that chironomids may provide a useful alternative to oxygen isotopes for correlating european lake sediment records during the lateglacial 2007 elsevier ltd all rights reserved

relations between mud volcanoes thrust deformation slope sedimentation and gas hydrate offshore north panama abstract seamarc ii swath mapping and migrated seismic reflection data show a high concentration of mud volcanoes in the primary sediment depocentre along the lower slope of a thrust belt offshore north panama the mud volcanoes are 0 4 2 0 km wide sonar reflectivity backscattering sediment cores and seismic stratigraphic relations indicate that the depocentre contains thick sequences of basinal turbidites which are ponded between the anticlinal ridges the ridges are composed of the deformed turbidites of the colombian basin and exhibit a strong bottom simulating reflector bsr apparently associated with a gas hydrate layer based on the concentration of mud volcanoes along the crests of the anticlinal ridges in the depocentre and the structural position of the bsr we suggest that folding along the deformation front sediment ponding leading to differential loading methane migration and accumulation in the anticlines and gas hydrate formation are important factors in the development of mud volcanoes in this region

the structure and formation of diapirs in the yinggehai song hong basin south china sea abstract the occurrence of shale diapirs in the yinggehai song hong ygh sh basin is well documented as is their association with big petroleum fields in order to better understand how and why the diapirs form we performed a detailed geophysical analysis using a new regional compilation of high resolution two and three dimensional seismic reflection data as well as drilling data that cover the diapirs in ygh sh basin as many as 18 diapirs were identified and are arranged in six n s striking vertical en echelon zones on seismic reflection sections gas chimney structures diapiric faults and palaeo craters are genetically linked with the process of diapirism here we use geophysical and geological observations to propose a three stage model for diapirism initiation emplacement and collapse during these three stages different diapiric structure styles are formed which we describe in detail these include buried diapirs piercing diapirs and collapsed diapirs we link the diapirism to activity on the offshore continuation of the red river fault as shown on our high resolution seismic reflection data which is also related to a high paleogeothermal gradient caused by crustal thinning we also recognize the role of loading by the very large volume of sediment eroded from the edges of the tibetan plateau and delivered by the red river to the basin

late glacial climatic oscillations as recorded in swiss lake sediments regional pollen assemblage zones for the late glacial period of the swiss plateau are introduced and defined they include four major zones artemisia juniperus hippophae betula pinus paz with several subzones pollen and oxygen isotope analyses on lacustrine sediments from several lakes in the area reveal four distinct phases of climatic oscillation in the time period of 13 000 9500 yr bp the first oscillation termed the aegelsee fluctuation occurs shortly before 12 000 yr bp and varve counts suggest its duration was ca 100 yr it is characterised by a short decrease in the oxygen isotopes as well as a short increase in nap associated with a depression in birch pollen values the second oscillation which occurs in the 18o record shortly before the deposition of the laacher see tephra ca 11 000 yr bp is termed the gerzensee fluctuation it occurs during a pine dominated phase and its vegetational effects cannot be determined palynologically the most prominent regressive phase is the younger dryas biozone ca 10 700 10 000 yr bp characterised by an increase in heliophilous nap and low 18o values the younger dryas biozone can often be subdivided palynologically into two parts a first part rich in grasses and juniper and a second part with higher filipendula and birch values during the preboreal biozone another distinct oscillation is evidenced only in the oxygen isotope ratios comparison of the swiss oxygen isotope profiles with the greenland dye 3 record suggests that not only the three major shifts in the 18o curves but also the minor ones are closely comparable suggesting some common climatic control

oxygen isotope and palaeotemperature records from six greenland ice core stations camp century dye 3 grip gisp2 renland and northgrip oxygen isotope variations spanning the last glacial cycle and the holocene derived from ice core records for six sites in greenland camp century dye 3 grip gisp2 renland and northgrip show strong similarities this suggests that the dominant influence on oxygen isotope variations reflected in the ice sheet records was regional climatic change differences in detail between the records probably reflect the effects of basal deformation in the ice as well as geographical gradients in atmospheric isotope ratios palaeotemperature estimates have been obtained from the records using three approaches i inferences based on the measured relationship between mean annual 18o of snow and of mean annual surface temperature over greenland ii modelled inversion of the borehole temperature profile constrained either by the dated isotopic profile or iii by using monte carlo simulation techniques the third of these approaches was adopted to reconstruct holocene temperature variations for the dye 3 and grip temperature profiles which yields remarkably compatible results a new record of holocene isotope variations obtained from the northgrip ice core matches the grip short term isotope record and also shows similar long term trends to the dye 3 and grip inverted temperature data the northgrip isotope record reflects i a generally stronger isotopic signal than is found in the grip record ii several short lived temperature fluctuations during the first 1500 yr of the holocene iii a marked cold event at ca 8 2 ka the 8 2 ka event iv optimum temperatures for the holocene between ca 8 6 and 4 3 ka a signal that is 0 6 stronger than for the grip profile v a clear signal for the little ice age and vi a clear signal of climate warming during the last century these data suggest that the northgrip stable isotope record responded in a sensitive manner to temperature fluctuations during the holocene copyright 2001 john wiley sons ltd

evidence for externally derived vein forming and mineralising fluids an example from the magdala gold mine stawell victoria australia abstract mineralogical and microfabric studies of the magdala gold deposit together with isotopic and fluid inclusion studies have shown that the mineralising fluid is externally derived the host rocks to the quartz veins do not possess any significant amounts of gold whereas the quartz veins can contain 7 g t gold the walls to the quartz veins possess alteration haloes in the form of stilpnomelane porphyroblasts attesting to the fact that the fluid in the veins was out of equilibrium with the host rocks the distribution of alteration haloes that occur parallel to the quartz vein margins necessitates that a subvertical fluid gradient be more or less constant during the deposition process in order to produce the observed architecture of the alteration haloes quartz lodes possess 18 o values that range from 15 8 to 17 3 per mil while associated host rocks range between 9 7 to 12 per mil in the metabasalts and 10 2 to 14 1 per mil in the volcanogenic and metasedimentary rocks the dissimilarity of 18 o values between host rocks and quartz veins suggests that there has been a high fluid influx in the veins implying external buffering four types of fluid inclusions were distinguished on the basis of spatial arrangement and composition using the laser raman spectroscopy method the salinity of the fluid inclusions range from 0 7 to 8 4 wt nacl equivalent suggesting that gold was deposited due to the influx of different external fluids the association of pyrite arsenopyrite pyrrhotite with gold and with pges suggests that these fluids have a lower crustal origin and may have originated from the upper mantle and mixed with fluids derived from deep seated metasediments

environmental and climate reconstruction of the late glacial holocene transition from a lake sediment sequence in aubrac french massif central chironomid and diatom evidence the analysis of fossil chironomid and diatom assemblages from a sedimentary record from les roustieres peat bog massif central france 1196 m asl allows the reconstruction of past environmental and climate changes during the late glacial and early holocene chironomid assemblages showed that the infilling of the palaeolake had commenced during the oldest dryas gs 2b as suggested by the rapid decrease in chironomid species associated with the cold and deep zone of lakes and by their replacement by littoral and eutrophic taxa quantitative july temperature reconstructions based on the chironomid data suggest that mean july air temperature tjul ranged between 6 degrees c and 11 degrees c at the termination of the oldest dryas period gs 2b climate began to warm at the start of the bolling period gi 1e between 15 000 and 14 800 cal yr bp with a rise in tjul of about 4 degrees c this climate warming is contemporaneous with lake eutrophication as suggested by diatoms and chironomids maximum temperatures of 13 14 degrees c were reached around 13 600 cal yr bp during the allered period gi 1c gi 1a the younger dryas period gs 1 is marked by a return to cold conditions with tjul of about 10 degrees c during a first phase then 13 degrees c in its terminal part a probable increase in the duration of the ice cover may have favoured arctic and alpine diatom species the early holocene climate improvement is marked by a rise in tjul of about 3 degrees c c 2016 elsevier b v all rights reserved

significance of mud volcanism 1 mud volcanism and diapirism have puzzled geoscientists for 2 centuries they have been described onshore and offshore in many places on earth and although they occur in various tectonic settings the majority of the features known to date are located in compressional tectonic scenarios this paper summarizes the main thrusts in mud volcano research as well as the various regions in which mud volcanism has been described mud volcanoes show variable geometry up to tens of kilometers in diameter and several hundred meters in height and a great diversity regarding the origin of the fluid and solid phases gas predominantly methane water and mud may be mobilized at subbottom depth of only a few meters but in places can originate from several kilometers depth with minor crustal or mantle input the possible contribution of mud extrusion to global budgets both from quiescent fluid emission and from the extrusive processes themselves is important in regions where mud volcanoes are abundant such as the collision zones between africa and eurasia fluid flux through mud extrusion exceeds the compaction driven pore fluid expulsion of the accretionary wedge also quiescent degassing of mud volcanoes may contribute significantly to volatile budgets and hence to greenhouse climate

characteristics of gas hydrate occurrences associated with mud diapirism and gas escape structures in the northwestern sea of okhotsk abstract an interpretation of 8450 line km of seismic reflection data acquired during four cruises in the northwestern sea of okhotsk shows widespread occurrence of free gas or gas hydrates in the sediment this occurrence is documented seismically by gas escape structures acoustic blanking and by a bottom simulating reflector bsr gas escape structures and vents are concentrated on the northern sakhalin continental margin here they are associated with local tectonic movements along a n s trending dextral shear system the inessa shear zone mud diapirism is common in the derugin basin where compression dominates this diapirism is probably closely related to the gas accumulations in the sediment below the base of the gas hydrate stability zone bghsz conductive heat flow derived from the bsr depth distribution averages about 30 8 mw m 2 only adjacent to basement highs and around the inessa shear zone do values higher than 80 22 mw m 2 occur these high values are attributed to an elevated geothermal gradient in the tectonically active zone where fluid venting takes place areas of drift sedimentation and mass wasting where sedimentation rates are high are characterised by computed heat flow values below 30 8 mw m 2 however these values must be corrected upwards by 3 20 depending on the sedimentation rate applicable 3 8 100 cm kyr the total amount of methane preserved in the hydrate stability zone hsz and trapped as free gas beneath the bsr is estimated at 17 14 10 12 m 3 for the northwestern sea of okhotsk and 15 12 10 13 m 3 for the entire sea of okhotsk the latter figure represents about 0 8 of the global reservoir of methane gas from hydrates our study documents that the semi enclosed sea of okhotsk offers favourable conditions for the accumulation of gas in its sediments on account of its subarctic climate and the prevailing hydrologic regime these conditions include high primary productivity low bottom water temperatures and high sedimentation rates

late holocene summer temperature reconstruction from chironomid assemblages of lake anterne northern french alps we present a chironomid based reconstruction of late holocene temperature from lake anterne 2060 m a s l in the northern french alps chironomid assemblages were studied in 49 samples along an 8 m long sediment core covering the last 1800 years july air temperatures were inferred using an inference model based on the distribution of chironomid assemblages in 100 swiss lakes the transfer function has a leave one out cross validated coefficient of determination r of 0 88 a root mean square error of prediction rmsep of 1 40 c despite possible biases induced by methodological aspects and the ecological complexity of the chironomid response to both climate and environmental changes the concordance of the lake anterne temperature reconstruction with other alpine records suggests that the transfer function has successfully reconstructed past summer temperature during the last two millennia the twentieth century is the only section of the record which shows a poor agreement with other climate recons

chironomid δ18o as a proxy for past lake water δ18o a lateglacial record from rotsee switzerland abstract we explored whether the stable oxygen isotope composition 18o of fossil chironomid remains can be used to reconstruct past variations in lake water 18o from lateglacial and early holocene sediments from rotsee switzerland a sediment core from the former littoral zone of the lake was examined since it contained both high concentrations of chironomid remains and abundant authigenic carbonates and therefore allowed a direct comparison of chironomid 18o with values measured on bulk carbonates since carbonate particles adhering to chironomid remains potentially affect 18o measurements we tested two methods to chemically remove residual carbonates trials with isotopically heavy and light acid solutions indicated that treatment with hydrochloric acid promoted oxygen exchange between chironomid remains and the water used during pretreatment in contrast a buffered 2 m ammonium chloride nh4cl solution did not seem to affect chironomid 18o to a significant extent fossil chironomid 18o was analyzed for the rotsee record both using standard palaeoecological methods and after pretreatment with nh4cl samples prepared using standard techniques showed a poor correlation with 18o of bulk carbonate r2 0 14 suggesting that carbonate contamination of the chironomid samples obscured the chironomid 18o signature samples pretreated with nh4cl correlated well with bulk carbonate 18o r2 0 67 and successfully tracked the well known lateglacial changes in 18o chironomid 18o indicated depleted lake water 18o during the oldest dryas period the aegelsee and gerzensee oscillations and the younger dryas whereas enriched 18o values were associated with sediments deposited during the lateglacial interstadial and the early holocene differences in the amplitude of variations in bulk carbonate and chironomid 18o are attributed to differential temperature effects on oxygen isotope fractionation during the formation of carbonates and chironomid head capsules or seasonal changes of lake water 18o potentially affecting 18o of these two substances to a different extent our results indicate that chironomid 18o can successfully reconstruct centennial to millennial scale changes in lake water 18o and that the method can be applied to carbonate rich records provided that care is taken to eliminate carbonate contamination from the samples

correlation and synchronisation of lateglacial continental sequences in northern central europe based on annually laminated lacustrine sediments abstract the present study focusses on correlation and synchronisation of weichselian lateglacial varved lake sediments from western germany meerfelder maar eifel region northern germany hamelsee lower saxony central poland lake go ci a z and eastern poland lake perespilno by using varve chronology tephrochronology palynostratigraphy and stable isotopes comparison of the several independent time scales shows that biotic and abiotic parameters respond abruptly and quasi synchronously within the errors of the different chronologies during the younger dryas preboreal transition moreover there is a consensus about the length of the younger dryas cold stage of 1100 1150 varve years in the allerod the prominent laacher see tephra 12 880 varve years bp can be used to fix floating varve chronologies the relative duration of this biozone has been determined in meerfelder maar and hamelsee at between 625 and 670 varve years in the meerfelder maar a combination of continuous varve counting and biostratigraphy has been possible for the almost entire lateglacial the comparison between continental limnic sequences and greenland ice core records should be made on the basis of independent chronologies in both archives it is more practicable to develop regional stratotypes on the continental regions instead of simply using ice cores as stratotypes for the lateglacial for terrestrial european records in this respect annually laminated lacustrine sequences have a great potential

relicts of mud diapirism of the emerged wedge top as an indicator of gas hydrates destabilization in the manila accretionary prism in southern taiwan hengchun peninsula abstract due to oblique collision of the luzon volcanic arc and eurasian passive margin in taiwan we observe southward progression of mountain building processes consequently the southernmost tip of taiwan represents the most recently emerged part of the orogen the hengchun peninsula the area shows evidence of a trench slope basin that emerged in the holocene with landforms that bear submarine characteristics in the late pleistocene lagoonal sediments blanket the basin however the deeper deposits maanshan formation can be found on the surface in several areas we document that the maanshan formation was brought to the surface through upwelling structures mud diapirs as a consequence of fast and overpressured sedimentation from the emerging orogen although fast erosional processes continuously reorganize the new landscape we are able to capture relicts of fast eroding inactive mud volcanoes these unique features are preserved on the surface due to shielding by coral terraces during the shallowing and the lagoonal period of the basin stable carbon 13c and oxygen 18o isotope analysis performed on samples of carbonate blocks of cold vents collected on the outcrops of the maanshan formation confirm classic seep carbonates origins we also identify a mud core anticline below the study area acting as the main source for the mud volcanoes and a possible cause of the uplift of the trench slope basin two multichannel seismic profiles from marine surveys along with a synthesis of several previous surveys helped construct a model of the characteristics of mud diapirism in southeastern offshore taiwan

dongfang 1 1 gas field in the mud diapir belt of the yinggehai basin south china sea abstract the dongfang 1 1 df1 1 mud diapir field is the largest gas field discovered in the yinggehai basin up to now with a proven gas reserve of 99 68 10 9 m 3 the gas pay zones are within the pliocene fine sandstones and siltstones of the littoral and sand bar facies with normal pressure regimes the gases include variable amounts of co 2 and n 2 in addition to hydrocarbon gases the hydrocarbon gases with the exception of biogenic methane and nitrogen originated from the marine source rocks within the overpressured lower to middle miocene strata while co 2 is most likely the product of thermal decomposition of the tertiary calcareous mudstones and pre tertiary carbonates through relatively long distance vertical migration the field has received at least four phases of natural gas charging occurring relatively late most likely during the post pliocene himalayan orogeny diapiric faults act as the main conduit for upward movement of fluids released from the deep high pressure system with abnormally high pressures providing the significant driving force for gas migration because of the episodic nature of the deep high pressured fluid release and the diapir fault activity this shallow diapir gas field is characterized by multiple gas sources and episodic fluid accumulation

new data on the lateglacial period of sw europe a high resolution multiproxy record from laguna de la roya nw iberia high resolution multiproxy analyses were performed on a 128 cm section of organic sediments accumulated in a small mountain lake in nw iberia laguna de la roya 1608 m asl the pollen stratigraphy together with radiocarbon dating provided the basis for a chronology ranging from 15 600 to 10 500 cal yr bp chironomid inferred july air temperatures suggest a temperature range from 7 to 13 c also evidencing two well established cold periods which may be equivalent to the intimate stages gs 2a and gs 1 furthermore a number of short cold events with summer temperatures dropping about 0 5 1 c appear intercalated within the lateglacial interstadial possibly equivalent to the intimate cold events gi 1d gi 1c2 and gi 1b and the early holocene possibly equivalent to the 11 2 k event the temperature variations predicted by our reconstruction allow explaining the changes in local conditions and productivity of the lake inferred from the biological record of the same sediment core furthermore they also agree with the local and regional vegetation dynamics and the main oscillations deduced for the vegetation belts based on its chronology our multiproxy record indicates a similar temperature development in nw iberia as inferred by the greenland 18o record the marine deep sea records off the atlantic iberian margin and other chironomid based lateglacial temperature reconstructions from europe nevertheless the impact of most of the less intense lateglacial early holocene cold events in nw iberia was most probably limited to very sensitive sites that were very close to ecotonal situations particularly our new pollen record indicates that they were represented as three minor environmental crises occurring during the lateglacial interestadial in this area the older dryas event in our usage corresponding to the aegelsee oscillation in central europe and event gi 1d in central greenland has previously been described in this region but its age and duration ca 14 250 14050 cal yr bp is now better constrained the two subsequent stages la roya i ca 13 600 13 400 cal yr bp and la roya ii ca 13 300 12 900 cal yr bp have been described for first time in nw iberia

chironomid based reconstruction of lateglacial summer temperatures from the ech palaeolake record french western pyrenees chironomid head capsules were extracted and identified in 52 samples along a sediment core retrieved from the ech palaeololake 710 m a s l in the west central pyrenees the pollen stratigraphy together with radiocarbon dates provided the basis for the chronology of the record since temperature changes were identified as one of the major determining factors for shifts in the ech chironomid assemblages during the lateglacial july air temperatures were tentatively inferred from the chironomid record using a transfer function based on a combined swiss and norwegian calibration dataset the model reconstructed july air temperatures between 10 and 13 c during the oldest dryas a two step increase in temperatures to 16 and 17 5 c during the first part of the interstadial followed by a decrease to 16 5 c at the end of the interstadial the ech record features three centennial scale 1 5 c coolings during the interstadial inferred temperatures decreased to 15 15 5 c during the younger dryas and reached ca 17 c at the beginning of the holocene the applicability of the combined swiss norwegian transfer function to the pyrenean fossil record was substantiated by the good statistics of the inference and the similar distribution of taxa with respect to temperature in the alps and the pyrenees the reliability of the ech record including its chronology was supported by its good concordance with other previously published chironomid based lateglacial temperature reconstructions from europe and the ngrip 18o record

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

mud diapirism and subcretion in the barbados ridge accretionary complex the role of fluids in accretionary processes mud diapirism has recently been recognized in several modern accretionary wedges it provides an important means of dewatering accretionary wedges and should be regarded as an important process for producing the melanges found in both modern and ancient accretionary terranes mud diapirism affects a large area of the barbados ridge accretionary complex the distribution of the mud diapirs appears to be primarily controlled by the presence of underconsolidated terrigenous submarine fan deposits that are being accreted to the complex the frequency of diapir occurrence decreases northward as the fan becomes thinner mud diapirs are absent from the very eastern most part of the complex formed from sediments accreted at its toe with the exception of a few mud volcanoes on the ocean floor in front of the complex the initiation of diapirism appears to be spatially coincident with the onset of subcretion or underplating of sediment to the base of the complex at a ramp between two levels of decollement it is proposed that the release of mud and pore water from the subcreted sediments is a direct or indirect cause of most of the mud diapirism in the accretionary complex there is a range of diapiric form dependent on the viscosity of the mud from mud volcanoes fed by low viscosity mud to higher viscosity mud ridges the diapirs in the eastern areas of the complex are generally mud volcanoes with narrow conduits feeding a surface mound mud ridges are prominent in the western parts of the complex this is interpreted as reflecting a general westward decrease in the fluid content of the accretionary complex bottom simulating seismic reflectors formed by gas hydrate are commonly developed in the areas of mud volcano occurrences the presence of the hydrate indicates that large volumes of methane are being generated at depth in these regions the generation of methane may be contributing to zones of overpressuring in the wedge methane may also be partly responsible for driving the diapiric material to the surface to form mud volcanoes ridges in the subducting oceanic crust beneath the accretionary complex locally enhance diapirism above their crests and southern flanks faults formed later in the development of the complex are more commonly associated with diapirism than those resulting from accretion at the toe of the wedge these later faults play an important role in controlling the sites of individual mud volcanoes chains of mud volcanoes and mud ridges

the younger dryas cooling in northeast germany summer temperature and environmental changes in the friedlander groβe wiese region a lake sediment record from the friedlander gro e wiese in northeast germany was studied to reconstruct summer temperature changes associated with changes in vegetation development during the weichselian lateglacial the record was analysed for pollen chironomids and oxygen and carbon isotopes of lake marl the combination of radiocarbon dates the presence of the laacher see tephra and correlation of lithological and palynological changes with other records from the region indicated that the record encompassed the allerod to the early holocene pollen assemblages reflect development of birch and later pine dominated forests during the allerod comparable to other sites in the region chironomid inferred mean july air temperatures c it for this period range between 14 0 and 14 8 c a temporary decrease in c it of 1 c a negative shift in the isotope records and a minor decline of birch may correspond to greenland interstadial 1b even though the transition to the younger dryas appears to be affected by reworking and redeposition processes a drop in c it to 11 1 c is reconstructed for the later part of the younger dryas while it appears that pine locally persisted in the region comparison with a nearby pollen record further indicates a local expansion of wetland grasses during this period at the transition to the holocene c it increased to 15 7 c while birch and pine forests re expanded copyright 2012 john wiley sons ltd

geochemistry and accumulation of carbon dioxide gases in china we propose the following identification indicators for co2 of different origins based on data obtained from analyzing the molecular composition of 1198 gas samples the co2 carbon isotope values of 390 samples and the helium isotope composition of 256 samples collected from wells of 16 oil and gas bearing basins and gas seepages in china and reviewing literature on organic and inorganic co2 throughout the world co2 is of organic origin if co2 content 13cco22 is of inorganic origin if dgr13cco2 8 pmil or co2 60 and co2 is of either organic or inorganic origin or a mixtur of organic and inorganic origins if 10 pmil 13cco213cco2 values of organic co2 mainly range from 10 to 22 pmil in tectonically stable oil and gas bearing basins where deep faults and magmatism are undeveloped organic co2 occurs almost exclusively in tectonically active oil and gas bearing basins where active faults and magmatism are present or in areas of modern volcanic activity the dgr13cco2 values of inorganic co2 range from 2 to 8 pmil and are distributed along faults the inorganic co2 with a dgr13cco2 value of 0 3 pmil is of metamorphic origin and that with dgr13cco2 values of 6 2 pmil is mantle derived and of magmatic origin in china the dgr13cco2 values of inorganic co2 gas pools range from 3 41 to 8 44 pmil and the helium ratio r ra is 1 which indicates that these gases are typically derived from the mantle

holocene temperature variations at a high altitude site in the eastern alps a chironomid record from schwarzsee ob solden austria few well dated quantitative holocene temperature reconstructions exist from high altitude sites in the central eastern alps here we present a chironomid based quantitative reconstruction of mean july air temperatures tjuly throughout the holocene for a remote high mountain lake schwarzsee ob solden situated above the treeline at 2796 m a s l in the austrian alps applying a chironomid temperature inference model developed from lakes of the alpine region to a high resolution chironomid record from the lake provides evidence for early holocene ca 10000 8600 cal yr bp tjuly of up to 8 5 c i e 4 c above the modern 1977 2006 mean july temperature the reconstruction reveals the so called 8 2 ka cold event centered at ca 8250 8000 cal yr bp with temperatures ca 3 c below the early holocene thermal maximum rather warm ca 6 c and productive conditions prevailed during ca 7900 4500 cal yr bp the chironomid record suggests a climate transition between ca 5200 and 4500 cal yr bp to cooler tjuly a distinct cooling trend is evident from ca 4500 until ca 2500 cal yr bp thereafter the study site experienced its coldest conditions around 4 c or less throughout the rest of the holocene with the exception of the warming trend during the late 20th century beside other factors the northern hemisphere summer insolation seems to be the major driving force for the long term trends in tjuly at high altitudes in the eastern alps due to the extreme location of the lake and the limited temperature range represented by the applied calibration data set the chironomid based temperature reconstruction fails to track phases of the late holocene climatic history with tjuly cooler than 4 c further chironomid based palaeoclimate model and down core studies are required to address this problem provide more realistic tjuly estimates from undisturbed high altitude lakes in the alps and extract a reliable regional temperature signal

high resolution chironomid inferred temperature history since ad 1580 from varved lake silvaplana switzerland comparison with local and regional reconstructions chironomids were used to reconstruct mean july air temperatures between c ad 1580 and 2001 at lake silvaplana a varved lake located in the engadine eastern swiss alps the goal of this study was to reconstruct temperature changes at near annual resolution and validate the reconstruction by comparison with records based on early instrumental data documentary proxy evidence dendrochronology geochemical biogenic silica bsi and mineralogical data quartz mica ratios at local and regional scales warmer than the climate normal ad 1961 1990 mean july air temperatures were inferred between c ad 1610 and 1662 ad 1710 and 1740 ad 1790 and 1866 ad 1940 and 1960 and ad 1990 and 2001 colder than the climate normal july air temperatures were reconstructed between c ad 1662 and 1710 ad 1740 and 1790 ad 1866 and 1919 and ad 1970 and 1990 the 420 year chironomid inferred mean july air temperature record was significantly p 0 01 related to june september jjas temperatures reconstructed from e

a chironomid based holocene summer air temperature reconstruction from the swiss alps we developed a quantitative chironomid july air temperature inference model based on surface sediments from 81 swiss lakes and applied it to the holocene subfossil chironomid record of hinterburgsee a small subalpine lake in the northern swiss alps present day mean july air temperature of 11 3 c after smoothing to reduce the high between sample variability of inferred temperatures the reconstruction indicates july air temperatures of 10 4 10 9 c at the end of the younger dryas of 11 9 12 8 c during the early and mid holocene 11500 4000 cal bp and slightly lower temperatures of 11 5 12 0 c during the late holocene 3500 1000 cal bp a warming trend inferred for the past millennium is most likely an artifact of human impact on hinterburgsee s chironomid fauna rather than a genuine temperature signal the most prominent climatological events during the holocene were two periods of lower temperatures at c 10700 10500 cal bp and 8200 7700 cal bp and an abrupt shift to a cooler late holocene cl

origins of taiwan s mud volcanoes evidence from geochemistry abstract the supply of natural gas from mud volcanoes is commonly attributed to the migration of gas bearing fluids from a deeper source area however the relative importance of these gas sources is not well known onshore mud volcanoes in taiwan are mainly located in the foothills of southwestern taiwan and in the coastal range of eastern taiwan generally along structurally weak zones geochemical analyses of gases and sediments from 17 mud volcanoes were undertaken in this study using molecular and stable isotopic compositions hydrocarbon gases were characterized by type and source maturity source rock assessments and nanofossil analyses were carried out to evaluate the potential and to infer the origin of sediments a particular effort was directed towards determining the genetic relationships between mud volcanic gas and associated sediments gases from taiwan s mud volcanoes are predominantly ch4 enriched with the exception of a few mud volcanoes where co2 predominates the origins of hydrocarbon gases in these systems range from microbial to thermally over mature sources while excess co2 may be derived from an inorganic origin as indicated by measured 13 c co 2 values the integration of geochemistry and local geology has yielded models with which to evaluate possible mechanisms for the formation of mud volcanoes

chironomidae insecta diptera succession in żabieniec bog and its palaeo lake central poland through the late weichselian and holocene abstract subfossil chironomidae assemblages were studied in a sediment sequence from abieniec bog in central poland the climate history and habitat changes in the palaeo lake were reconstructed from these assemblages currently no chironomid based climate calibration set is available from poland and so past mean july air temperatures were inferred from chironomid climate calibration data sets from norway russia and switzerland during the late weichselian the three calibration functions from these data sets provided similar temperature inferences but there was some divergence in the reconstructions for the younger dryas and holocene in the late pleniglacial inferred summer air temperature was relatively low 8 12 c and the lake was oligotrophic at about 16 5 ka bp temperature rapidly rose to 15 c and assemblage diversity substantially increased during the interstadial temperature stayed at this level in the younger dryas july air temperature was only 1 2 c lower than in the interstadial as inferred from the norwegian calibration data set whereas the russian and swiss calibration functions did not indicate any temperature decrease from the beginning of the holocene taxa typical of meso eutrophic conditions dominated there was an increased abundance of phytophilous species and the assemblage composition was also influenced by changes in water level palaeotemperature reconstructions differed in their values from 8 0 to 8 7 ka bp inferences based on the swiss and russian data sets indicated a cold oscillation while reconstructions based on the norwegian data set did not show any temperature decrease after 2 5 ka bp assemblage diversity and head capsule concentrations decreased in the last millennium semi terrestrial taxa dominated except from late medieval to early modern times when shallow water species reappeared

a 200 year mid european air temperature record preserved in lake sediments an extension of the δ18op air temperature relation into the past abstract a detailed history of the water oxygen isotope ratios of lake ammersee southern germany was established for the last two centuries by analyzing oxygen isotope ratios of ostracod shells from a sediment core in a three to five year resolution empirical analysis and modelling of the isotope hydrology of the lake show that the oxygen isotopic composition of the lake water is mainly controlled by the isotopic composition of local precipitation for the last 200 years the lake isotope record is strongly correlated to the air temperature record from hohenpeisenberg situated within the lake s catchment area thus the mid european relation between 18 o in precipitation and air temperature documented for the last 20 years can be extended over a longer time and a larger temperature range the results provide further support for the validity of ostracod 18 o from ammersee sediments as a quantitative proxy for mean annual air temperature probably extending back to the last glaciation

geochemistry and episodic accumulation of natural gases from the ledong gas field in the yinggehai basin offshore south china sea abstract the ledong gas field consisting of three gas pools in a shale diapir structure zone is the largest gas discovery in the yinggehai basin the gases produced from the pliocene and quaternary marine sandstone reservoirs show a considerable variation in chemical composition with 5 4 88 ch 4 0 93 co 2 and 1 23 7 n 2 the co 2 enriched gases often display heavier methane 13 c values than those with low co 2 contents the 15 n values of the gases range from 8 to 2 and the n 2 content correlates negatively with the co 2 content the high geothermal gradient associated with a relatively great burial depth in this area has led to the generation of hydrocarbon and nitrogen gases from the lower middle miocene source rocks and the formation of abundant co 2 from the tertiary calcareous shales and pre tertiary carbonates the compositional heterogeneities and stable carbon isotope data of the produced gases indicate that the formation of the ld221 gas field is attributed to three phases of gas migration initially biogenic gas followed by thermogenic hydrocarbon gas and then co 2 rich gas the filling processes occurred within a short period approximately from 1 2 to 0 1 ma based on the results of the kinetics modeling geophysical and geochemical data show that the diapiric faults that cut through miocene sediments act as the main pathways for upward gas migration from the deep overpressured system into the shallow normal pressure reservoirs and that the deep overpressure is the main driving force for vertical and lateral migration of the gases this gas migration pattern implies that the transitional pressure zone around the shale diapir structures was on the pathway of upward migrating gases and is also a favorable place for gas accumulation the proposed multiple sources and multiple phases of gas migration and accumulation model for the ledong gas field potentially provide useful information for the future exploration efforts in this area

gas hydrate associated with mud diapirs in southern okinawa trough many mud diapirs have been recognized in southern okinawa trough by a multi channel seismic surveying on r v kexue i in 2001 gas hydrates have been identified by the seismic reflection characteristics the velocity analysis and the impedance inversion geothermal heat flow around the central of the mud diapir has been determined theoretically by the bottom simulating reflectors bsrs comparing the bsr derived and the measured heat flow values we infer that the bsr immediately at the top of the mud diapirs indicate the base of the saturated gas hydrate formation zone bsghfz but not as we ordinarily know the base of the gas hydrate stability zone bghsz which could be explained by the abnormal regional background heat flow and free gas flux associated with mud diapirs as a result it helps us to better understand the generation mechanism of the gas hydrates associated with mud diapirs and to predict the gas hydrate potential in the southern okinawa trough

temperature gradients in northern europe during the last glacial holocene transition 14 914c kyr bp interpreted from coleopteran assemblages late glacial and early holocene climatic conditions have been reconstructed for northern europe using the mutual climatic range mcr palaeoclimate method based on fossil coleopteran assemblages altogether beetle faunas from 77 sites have been analysed ranging from ireland in the west to poland and finland in the east and mcr estimates calculated the results are plotted on 16 maps each representative of a selected time slice covering the period from 14 5 14c kyr bp to 9 0 14c kyr bp eight of the maps show the mcr estimates of tmax mean temperature of the warmest month derived from each site for which data are available while the remainder show estimated tmax isotherms interpolated from these values it can be demonstrated that at times the thermal climate was fairly uniform throughout the study area whereas at others temperature gradients were much steeper than they are in the region today there also appears to be a distinct contrast between cold periods when contours trended nw se and warmer periods when contours trend w e or even ne sw the pattern of climatic changes that emerges is shown to be very different from the traditional view that has been used up to now as a template for classifying late glacial climatic events on a wide even global scale the suddenness and intensity of changes in the thermal climate may have been partially responsible for an apparent lack of equilibrium between the flora and fauna of the time and the physical environment in which they lived 1998 john wiley sons ltd

high resolution late glacial chronology for the gerzensee lake record switzerland δ18o correlation between a gerzensee stack and ngrip oxygen isotope variations were analyzed on bulk samples of shallow water lake marl from gerzensee switzerland in order to evaluate major and minor climatic oscillations during the late glacial to highlight the overall signature of the gerzensee 18o record 18o records of four parallel sediment cores were first correlated by synchronizing major isotope shifts and pollen abundances then the records were stacked with a weighting depending on the differing sampling resolution to develop a precise chronology the 18o stack was then correlated with the ngrip 18o record applying a monte carlo simulation relying on the assumption that the shifts in 18o were climate driven and synchronous in both archives the established chronology on the gicc05 time scale is the basis for 1 comparing the 18o changes recorded in gerzensee with observed climatic and environmental fluctuations over the whole north atlantic region and 2 comparing sedimentological and biological changes during the rapid warming with smaller climatic variations during the bolling allerod period the 18o record of gerzensee is characterized by two major isotope shifts at the onset and at the termination of the bolling allerod warm period as well as four intervening negative shifts labeled gi 1e2 d c2 and b which show a shift of one third to one fourth of the major 18o shifts at the beginning and end of the bolling allerod despite some inconsistency in terminology these oscillations can be observed in various climatic proxies over wide regions in the north atlantic region especially in reconstructed colder temperatures and they seem to be caused by hemispheric climatic variations

hydroclimatic changes in the british isles through the last glacial interglacial transition multiproxy reconstructions from the vale of pickering ne england abstract european paleoenvironmental records through the last glacial interglacial transition lgit ca 16 8 cal ka bp record a series of climatic events occurring over decadal to multi centennial timescales changes in components of the climatic system other than temperature e g hydrology through the lgit are relatively poorly understood however and further records of hydroclimatic changes are required in order to develop a more complete understanding on the phasing of environmental and anthropogenic responses in europe to abrupt climate change here we present a multiproxy palaeoenvironmental record macroscale and microscale sedimentology macrofossils and carbonate stable isotopes from a palaeolake sequence in the vale of pickering vop ne england which enables the reconstruction of hydroclimatic changes constrained by a radiocarbon based chronology relative lake level changes in the vop occurred in close association although not necessarily in phase to threshold shifts across abrupt climate change transitions most notably lowering during cooling intervals of the lgit gi 1d gi 1b and gs 1 this reflects more arid hydroclimates associated with these cooling episodes in the british isles comparisons to hydrological records elsewhere in europe show a latitudinal bifurcation with northern europe 50 60 n becoming more arid humid and southern europe 40 50 n becoming more humid arid in response to these cooling warming intervals we attribute these bifurcating signals to the relative positions of the atlantic storm tracks sea ice margin and north atlantic polar front napf during the climatic events of the lgit

oxygen isotope wiggle matching as a tool for synchronising ice core and terrestrial records over termination 1 abstract in nw europe the large number of terrestrial records that are now available from termination 1 15 10 kcal yr bp form the basis for a highly detailed picture of lateglacial environmental change nevertheless the greenland oxygen isotope records grip gisp2 are still regarded as the best high resolution climate proxy for the north atlantic region in order to evaluate spatial contrasts and leads and lags in the climate system integration of ice core marine and terrestrial records is becoming increasingly important intimate objectives however comparisons between different environments require a common time scale for the proxy climate records stable isotope analyses performed on lateglacial lacustrine calcareous deposits in the netherlands provide a terrestrial oxygen isotope record comparable to that from the greenland ice core these atmospherically controlled lacustrine oxygen isotope signals not only constitute an independent palaeoclimatic proxy but provide the basis for synchronising records from these environments as well more over this synchronisation reveals some remarkable aspects concerning the timing of the oxygen isotope and palynological events as recorded in the netherlands above all oxygen isotope wiggle matching offers a means of correlating terrestrial and ice core records

a compilation of western european terrestrial records 60 8 ka bp towards an understanding of latitudinal climatic gradients terrestrial records of past climatic conditions such as lake sediments and speleothems provide data of great importance for understanding environmental changes however unlike marine and ice core records terrestrial palaeodata are often not available in databases or in a format that is easily accessible to the non specialist as a consequence many excellent terrestrial records are unknown to the broader palaeoclimate community and are not included in compilations comparisons or modelling exercises here we present a compilation of western european terrestrial palaeo records covering entirely or partially the 60 8 ka intimate time period the compilation contains 56 natural archives including lake records speleothems ice cores and terrestrial proxies in marine records the compilation is limited to include records of high temporal resolution and or records that provide climate proxies or quantitative reconstructions of environmental parameters such as temperature or precipitation and that are of relevance and interest to a broader community we briefly review the different types of terrestrial archives their respective proxies their interpretation and their application for palaeoclimatic reconstructions we also discuss the importance of independent chronologies and the issue of record synchronization the aim of this exercise is to provide the wider palaeo community with a consistent compilation of high quality terrestrial records to facilitate model data comparisons and to identify key areas of interest for future investigations we use the compilation to investigate western european latitudinal climate gradients during the deglacial period and despite of poorly constrained chronologies for the older records we summarize the main results obtained from nw and sw european terrestrial records before the lgm

the lateglacial and early holocene climate variability and vegetation dynamics derived from chironomid and pollen records of lieporiai palaeolake north lithuania abstract to investigate the lateglacial and early holocene climatic and environmental dynamics in the eastern baltic we analysed chironomid and pollen data from lieporiai palaeolake north lithuania the first quantitative mean july air temperature reconstruction from lithuania based on fossil chironomid assemblages was performed using expanded fennoscandian calibration model our study suggests that sedimentation started at about 14 600 cal yrs bp and lasted until the early holocene the mean july air temperature for lateglacial and early holocene from studied site ranged between 13 c 16 c which was 2 4 c lower than the present rapidly after the deglaciation during bolling gi 1e interstadial reconstructed july air temperature reached 15 c the marked temperature decrease to 13 2 c was recorded during the older dryas gs 1d temperature reached its highest values up to 16 c during the allerod gi 1a the younger dryas gs 1 was relatively cold with the mean july air temperature 14 c and this was 3 9 c colder than the present the pattern of the lateglacial temperature changes from lieporiai lake shows both similarities and some differences from the other chironomid based regional and european reconstructions chironomid inferred palaeoenvironmental changes are in positive correlation with changes in the development of vegetation

a high resolution multiproxy late glacial record of climate change and intrasystem responses in northwest england a lacustrine carbonate sequence from hawes water lancashire uk has been studied using stable isotopic lithological pollen and mineral magnetic analysis the data reveal four abrupt climatic oscillations in the late glacial interstadial leading up to the onset of the loch lomond stadial the data also point to climatic warming relatively early within the stadial ca 12 500 grip yr prior to the onset of the holocene the oxygen isotope record is taken as a signature of climate forcing against which the response of the lake system can be monitored by adopting this approach it is revealed that the response of the biological system to the rapid climatic oscillations is non linear and primarily a function of the antecedent conditions a significant end devensian isotopic excursion a is matched by only minor changes in the cold adapted floras and faunas during the warmer interstadial the response of the biological ecosystem events b d is clearly influenced by thresholds major changes in the catchment vegetation associated with relatively minor oscillations in the isotopic signature the stratigraphical patterns reveal significant lag effects between the onset of climate deterioration and resulting changes in vegetation copyright 2002 john wiley sons ltd

a comparison of reconstructions based on aquatic and terrestrial beetle assemblages late glacial early holocene temperature reconstructions for the british isles this paper presents the results of a study of mcr estimates of mean july temperature tmax during the late glacial interval from four british sites comparing estimates based on terrestrial and aquatic species we have generated precise age models for three of these datasets and have found that in most cases the terrestrial based estimates agree with the aquatic based estimates the temperatures across the late glacial are consistent and warm in the early interstadial however differences exist in the later interstadial where llanilid seems to be slightly warmer than either st bees or gransmoor the small scale discrepancies between aquatic and terrestrial beetle mcr temperature estimates that were found from these sites appear to occur during the transition into the late glacial interstadial during the transition into the younger dryas cooling and during the younger dryas interval we tentatively attribute these discrepancies to the presence of meltwater from snowbanks surrounding the study sites during the stated intervals and suggest that mcr studies of late glacial beetle assemblages from northwest europe should adopt the protocol of generating separate aquatic and terrestrial estimates for comparative purposes

summer temperature development 18 000 14 000 cal bp recorded by a new chironomid record from burgaschisee swiss plateau abstract the termination of the last ice age after the last glacial maximum lgm represents a dynamic period in the history of the circum north atlantic region so far there are few reliably dated climatic reconstructions covering the lateglacial period prior to 14 700 cal bp in central and northern europe we present a new chironomid record for the period 18 000 14 000 cal bp from burgaschisee switzerland chironomid assemblages immediately following glacier retreat were dominated by taxa indicative of cold oligotrophic conditions such as sergentia coracina type and micropsectra radialis type a gradual transition to assemblages with moderate abundances of taxa indicative of warmer climatic conditions such as dicrotendipes nevosus type and tanytarsus glabrescens type started after ca 16 100 cal bp this initial and gradual chironomid assemblage shift culminated in a more pronounced and rapid inferred temperature change at the oldest dryas bolling transition at ca 14 700 cal bp where further types indicative of warm conditions such as tanytarsus lactescens type first occurred and replaced chironomids indicative of colder conditions such as paracladius and protanypus we estimated past july air temperature changes from the chironomid assemblages by applying to the record a chironomid temperature transfer function that is based on chironomid distribution data from 274 lakes in switzerland and norway the resulting reconstruction which features a sample specific root mean square error of prediction of 1 36 1 46 c indicates temperatures around 9 c at the beginning of the record an initial gradual warming phase initiating at ca 16 100 cal bp is recorded reaching values around 10 c for the period 16 100 15 500 cal bp temperatures continue to increase reaching values around 12 c for the period preceding the bolling warming when temperatures rose rapidly to values around 15 c the early temperature rise to values of 10 12 c prior to the bolling warming agrees with widespread vegetation changes recently reported for this region based on palaeobotanical analyses which indicate a shift from herbaceous tundra to shrub tundra with low density tree birch stands with open canopies together these results suggest an earlier lateglacial temperature increase in southwest central europe than expected based on earlier palaeobotanical reconstructions although with a less pronounced warming than has been reported for ca 16 000 cal bp from south of the alps this early lateglacial warming agrees with glacier reconstructions which suggest several step wise reductions of glacier extent in this period as well as with evidence from other palaeotemperature reconstructions and suggests that not only southern europe but significant parts of europe north of the alps may have been characterized by early lateglacial warming well before the rapid warming at ca 14 700 cal bp

an event stratigraphy for the last termination in the north atlantic region based on the greenland ice core record a proposal by the intimate group it is suggested that the grip greenland ice core should constitute the stratotype for the last termination based on the oxygen isotope signal in that core a new event stratigraphy spanning the time interval from ca 22 0 to 11 5 k grip yr bp ca 19 0 10 0 k 14 c yr bp is proposed for the north atlantic region this covers the period from the last glacial maximum through termination 1 of the deep ocean record to the pleistocene holocene boundary and encompasses the last glacial late glacial of the traditional northwest european stratigraphy the isotopic record for this period is divided into two stadial episodes greenland stadials 1 gs 1 and 2 gs 2 and two interstadial events greenland interstadials 1 gi 1 and 2 gi 2 in addition gi 1 and gs 2 are further subdivided into shorter episodes the event stratigraphy is equally applicable to ice core marine and terrestrial records and is considered to be a more appropriate classificatory scheme than the terrestrially based radiocarbon dated chronostratigraphy that has been used hitherto 1998 john wiley sons ltd

climate and biomass control on fire activity during the late glacial early holocene transition in temperate ecosystems of the upper rhone valley france abstract the main objective of this study is to document paleofire activity during the late glacial early holocene transition in temperate ecosystems for this purpose we cored lakes paladru and moras rhone valley france and quantified sedimentary charcoal accumulation rate and fire frequency to assess the role of climate and vegetation in paleofire activity charcoal data were compared to vegetation dynamics based on pollen analyses and to climate reconstructions the first increase in paleofire activity occurred at the beginning of the bolling allerod interstadial period 14 500 cal yr bp synchronous with temperature and fire prone vegetation increases during the younger dryas paleofire activity first decreased 12 600 12 200 cal yr bp and then abruptly increased 12 200 11 600 cal yr bp this change corresponds to a known climate partitioning that occurred during the younger dryas and implies that a sufficient quantity of biomass was available during the second period at the beginning of the holocene fire activity remained high this is in agreement with the increases in temperature and vegetation density the change in forest composition since ca 11 200 cal yr bp partly explains the decrease in paleofire activity whereas warm climate conditions seem suitable for fire ignition and propagation

isotope signature of the younger dryas and two minor oscillations at gerzensee switzerland palaeoclimatic and palaeolimnologic interpretation based on bulk and biogenic carbonates oxygen and carbon isotope ratios in the carbonate of benthic ostracodes pseudocandona marchica and molluscs pisidium ssp were measured across the transitions bordering the younger dryas chronozone in littoral lacustrine cores from gerzensee switzerland the specific biogenic carbonate records confirm the major shifts already visible in the continuous bulk carbonate oxygen isotope record 18occ if corrected for their vital offsets oxygen isotope ratios of pisidium and juvenile p marchica both formed in summer are almost identical to 18occ this bulk carbonate is mainly composed of encrustations of benthic macrophythes chara ssp also mainly produced during summer adult p marchica which calcify in winter show consistently higher 18o larger shifts across both transitions and short positive excursions compared with the summer forms especially during early preboreal despite such complexity the 18o of adult p marchica probably reflects more accurately the variations of the 18o of former lake water because during winter calcification temperatures are less variable and the water column isotopically uniform the difference between normalised 18o of calcite precipitated in winter to that formed in summer can be used to estimate the minimum difference between summer and winter water temperatures in general the results indicate warmer summers during the late allerod and early preboreal compared with the younger dryas altogether the isotopic composition of lake water 18ol and of the dissolved inorganic carbonate 13cdic reconstructed from adult pseudocandona marchica as well as the seasonal water temperature contrasts indicate that the major shifts in the 18o of local precipitation at gerzensee were augmented by changes of the lake s water balance with relatively higher evaporative loss occurring during the allerod compared with the younger dryas it is possible that during the early preboreal the lake might even have been hydrologically closed for a short period we speculate that such hydrologic changes reflect a combination of varying evapotranspiration and a rearrangement of groundwater recharge during those climatic shifts

midges and palaeotemperature reconstruction the north american experience abstract the development of midge based palaeoclimatology in north america is reviewed with a focus on lateglacial and holocene climatic change although relatively few sites have been studied midge inferred palaeotemperatures reveal detailed records of lateglacial climate oscillations and more subtle holocene temperature changes holocene climate changes are often at or near the detection limit using current palaeotemperature inference models interference from other environmental variables including water depth and oxygen concentration changes are discussed as well as the challenges inherent to developing better models the isotopic signature of chitin preserved in midge head capsules has opened new avenues for midge palaeotemperature inference through coordinated research efforts national and international collaborations will provide opportunities to reconstruct holocene palaeoclimate at continental and hemispheric scales

low velocity layers in the northwestern margin of the south china sea evidence from receiver functions of ocean bottom seismometer data abstract the receiver function method was applied to teleseismic recordings of an active source ocean bottom seismometer array in the northwestern margin of the south china sea forward modeling of the receiver functions was used to derive velocity interfaces beneath the stations two main groups of low velocity layers were imaged the first group in the reef area with a thickness of 7 10 km exhibits a seaward uptrend of the buried depth but poor continuity the second group with a thickness of 3 4 km is more continuous along the zhongsha trough the buried depth decreases asymmetrically from the flanks to the rift center a high shear wave velocity layer of 4 0 km s is imaged at the crust bottom beneath the zhongsha trough with thickness of 3 km the average vp vs in the cenozoic sediment is 2 0 3 0 and was affected by high fluid activity induced by intensive faults the vp vs of the crust varies between 1 77 and 1 88 suggesting an intermediate to basic composition under the continental extension together these results suggest a two stage evolution model of the continental crust in the first stage the crust deformed in a ductile manner and thus created considerable shearing structures with high anisotropy that caused the obvious decrease of the shear wave velocity in the second stage the shearing structures connected asymmetrically driven by detachment faults in the upper crust and upwelling of the lower crust the zhongsha trough then formed probably with magmatic underplating due to lithospheric extension or rising of hot mantle materials