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

middle and late jurassic radiolarian palaeoecology versus carbon isotope stratigraphy abstract jurassic radiolarians are sensitive to palaeoclimatic palaeoceanographic changes recorded by the stable carbon isotope curve carbon isotopic variations have been linked to changes in ocean structure productivity and concentrations of greenhouse gases in the atmosphere in the middle upper jurassic terminilletto section of the umbria marche sabina apennines central italy well preserved radiolarians are present in a sequence of cherty limestones interbedded with platform derived carbonates the 13 c curve in the aalenian kimmeridgian interval indicates three main positive 13 c events in the lower bajocian late bathonian lower callovian and middle oxfordian the positive 13 c shifts are correlated to increases in visible chert in the outcrop and may represent periods of increased biological productivity of surface sea water spumellaria nassellaria ratios and the fluctuations of relative abundance of selected genera tend to correlate with 13 c and chert abundance values and seem to be related to episodes of high nutrient mobilisation from the base of the bajocian the radiolarian associations show a slight tendency towards diversification coincident with increasing 13 c values in the upper part of the middle bajocian last appearances prevail over first appearances associated with the peak of the 13 c event this may indicate maximum eutrophic conditions coincident with the late bathonian early callovian positive 13 c shift the radiolarian associations record a different trend with respect to the bajocian event when the 13 c values are increasing to a maximum radiolarian associations tend to be reduced in species diversity followed by a small diversification trend when the 13 c values are decreasing we speculate that during the callovian a more stressful palaeoenvironment due to high level of eutrophication is indicated by the combination of high productivity of biogenic silica and low carbonate input although varying preservational conditions may have influenced the observed trends in the radiolarian associations the good correlation between changes of sedimentation patterns radiolarian assemblages and 13 c positive anomalies open interesting avenues for further investigations concerning the palaeoecology of mesozoic radiolarians

holocene paleoceanography of the northwest passage canadian arctic archipelago abstract a series of cores box and piston were collected at 2 key locations in lancaster sound cores 2004 804 009 bc and pc and barrow strait cores 2005 804 004 bc and pc in the canadian arctic archipelago to document the evolution of sea surface conditions in the main axis of the northwest passage during the holocene time period reconstruction of sea surface parameters summer temperature and salinity duration of sea ice cover were estimated based on transfer functions using dinoflagellate cyst assemblages as proxy indicators the chronology of these cores is based on calibrated ams 14c dates 210pb analyses and correlations between paleomagnetic secular variations of the geomagnetic field and a predicted spherical harmonic model of the geomagnetic field cals7 k 2 our age models for both cores indicate that 009 pc spans the last 11 100 cal bp while 004 pc encompasses the last 10 800 cal bp calculated sedimentation rates are in the range of 43 140 cm kyr for core 009 pc and 15 118 cm kyr for core 004 pc allowing for a millennial time scale resolution in each core our results indicate relatively harsh conditions in lancaster sound between 10 800 and 9000 cal bp summer temperatures 2 c cooler than at present which we associate with the presence of active ice streams in northernmost baffin bay and a weak west greenland current this is followed by a warming trend up to 3 c higher than present that took place between 8500 and 5500 cal bp which we associate with the holocene thermal maximum and to a large scale atmospheric pattern such as the arctic oscillation operating at the millennial time scale this is concomitant with an increase in the relative abundance of phototrophic dinoflagellate cyst taxa a gradual cooling of sea surface temperature and increased sea ice follow this from 5500 cal bp until the modern period in barrow strait harsh sea surface conditions prevailed from 11 100 to 5500 cal bp with summer temperatures as low as 4 c cooler than at present the warming trend occurred later in this region between 5500 and 1000 cal bp after which a gradual cooling is observed until the modern period the apparent shift or opposite warming trends between lancaster sound and barrow strait after 5500 cal bp could be the result of a change in atmospheric circulation patterns related to a possible shift in the ao mode from ao to ao comparison of ice core 18o record from devon island ice cap and the reconstructed sea surface temperature from core 009 pc suggests a strong atmospheric oceanic coupling throughout the holocene in this area

latest quaternary and holocene paleoceanography of the eastern baffin island continental shelf canada benthic foraminiferal evidence foraminiferal zones radiocarbon ages on shells and corrected ages on pretreated organic sediment from four cores from the eastern baffin island continental shelf suggest a three stage deglacial to postglacial history late wisconsin to holocene the earliest sediments in the cores contain foraminiferal species elphidium excavatum cassidulina reniforme islandiella helenae indicative of distal glaciomarine environments that lasted at least several thousand years an oceanographic change about 8500 years ago is indicated by a melonis zaandamae zone in northern and central shelf cores collected from 200 800 m water depth the presence of m zaandamae in the north and its absence in the south suggest warmer and more saline postglacial water in northern baffin bay whose influence became diluted with cooler coastal meltwater as the current flowed south along the baffin island shelf sediments after 6000 years ago on the northern and central shelf are dominated by agglutinated foraminifera suggesting dis

greenland glacial history and local geodynamic consequences summary space time reconstructions of the continental ice sheets that existed at last glacial maximum lgm have previously been produced using two entirely independent methodologies one based upon the use of theoretical models of ice sheet accumulation and flow and one based upon the geophysical inversion of relative sea level rsl histories from previously ice covered regions the analyses described in this paper demonstrate the significant advantages that derive from the simultaneous application of both methods to the particular case of greenland we thereby show that the ice 4g reconstruction of the glaciation history of this region from lgm to present which was based upon the geophysical inversion of rsl data alone was reasonably accurate in the peripheral regions where rsl data were available but inaccurate in the interior of the ice sheet which was unconstrained by such information we test the new model of greenland glacial history determined by the simultaneous application of the constraints that derive from ice sheet modelling and the geophysical inversion of rsl data by employing recently published geodetic inferences of mass balance over the entire interior region of the ice sheet and of gps measurements of vertical crustal motion these observations which were not employed to constrain the ice sheet reconstruction provide significant support for the new glacial history for greenland that our analyses have led us to infer

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

sea surface conditions in northernmost baffin bay during the holocene palynological evidence the analysis of cores collected in northernmost baffin bay from within the area of the north water polynya permits definition of a composite sedimentary sequence ca 12 m thick spanning the last 10 000 14 c yr with only a few discontinuities palynological analyses were performed in order to reconstruct changes in surface water conditions and biogenic production transfer functions using dinocyst assemblages were applied to estimate sea surface temperature sst and salinity as well as the seasonal duration of sea ice cover at the base of the record prior to 9300 14 c yr bp dinocysts and organic linings of benthic foraminifers are sparse indicating harsh conditions and low productivity after ca 9300 14 c yr bp the increased concentration of benthic foraminifers up to 10 3 linings cm 3 and dinocyst fluxes 10 2 10 3 cysts cm 2 yr 1 reveals high biological productivity related to open water conditions the early to middle holocene from ca 9000 to ca 3600 14 c yr bp is marked by relatively high species diversity in dinocyst assemblages and the significant occurrence of autotrophic taxa such as spiniferites elongatus pentapharsodinium dalei and impagidinium pallidum this assemblage suggests conditions at least as warm as at present from ca 6400 to ca 3600 14 c yr bp transfer functions indicate warmer conditions than at present with sst in august fluctuating up to 5 5 c after 3600 14 c yr bp the dinocyst record suggests a trend of decreasing temperature toward modern values marked by recurrent cooling events copyright 2001 john wiley sons ltd

spatial and temporal distribution of soil organic carbon in nonsorted striped patterned ground of the high arctic 1 the role of periglacial processes on soil carbon distribution is examined at a high arctic site in northwest greenland a 16 m trench dug across a series of nonsorted stripes at thule air base revealed sand rich wedges underlying striped vegetated troughs and organic rich soil horizons buried at depth the site has sparse prostrate vegetation and is estimated to contain 9 4 kg m 2 of soil organic carbon soc in the active layer the distribution of carbon is variable with nearly half 49 stored in the sand wedges which only account for 10 of the trench area additionally 62 of the total soc was found below 25 cm highlighting the significant role of cryoturbation and physical redistribution of carbon in permafrost affected soils carbon in the active sand rich wedges dates from modem at the surface 65 35 radiocarbon years to 2695 40 radiocarbon years at depth and carbon turnover time appears to be 450 years buried organic horizons found at 50 70 cm depth have radiocarbon ages of 27 480 31 900 bp a conceptual model is proposed in which the active sand wedges have developed in an approximately 30 ka surface containing buried soils preserved in permafrost or under a cold based glacier as the ice retreated and soils warmed soil development and active cryoturbation resumed forming nonsorted stripes in the modern surface

quaternary ice transport in the canadian arctic and extent of late wisconsinan glaciation in the queen elizabeth islands most of the ice rafted debris in channels off the queen elizabeth islands nunavut is of local origin particularly in the inner part of the archipelago but samples from the arctic shelf contain as much as 40 grains from sources as far away as 2000 km including the siberian shelves particle transport by drifting sea ice from distant shelves is an important process on the arctic continental shelf of the queen elizabeth islands in the interior of the queen elizabeth islands and in the viscount melville and lancaster sounds particle transport is limited to distances of approximately 200 km mixing is more common among grains of coarse silt to fine sand than in the 250 m fraction but even the latter contains debris from sources far apart during the late wisconsinan the northern southern and eastern queen elizabeth islands were covered by glaciers flowing radially from ice centers on the islands into the inter island channels queens channel was completely filled by ice and a glacier lobe moved

duration of the early bajocian and the associated δ13c positive excursion based on cyclostratigraphy the early bajocian about 172 ma ago was a period of tectonic changes a global carbon isotope positive excursion and biological diversification of marine invertebrates e g ammonites radiolarians and coccolithophores unfortunately both the duration of the early bajocian and the associated palaeoenvironmental changes are still poorly constrained we propose here an estimate of the duration of this sub stage based on a cyclostratigraphic analysis of the carbonate content from the chaudon norante section french subalpine basin france the chaudon norante succession has been correlated with les dourbes section using greyscale variations to detect possible local hiatuses the duration estimated here for the entire early bajocian is 4 082 ma two intervals were identified in the positive 13 c excursion an increase of carbon isotope values lasting 1 36 ma and climax isotope values lasting for 2 72 ma a cooling at high latitudes and warming at low latitudes may have enhanced the earth s temperature gradient leading to an increase in humidity which in turn triggered ocean eutrophication at the origin of the 13 c positive excursion supplementary material the complete dataset presented in the paper a colour version of the figure 8 and correlation of 13 c excursions between our studied site and contemporaneous sites are available at www geolsoc org uk sup18555

geochemistry of modern brachiopods applications and implications for oceanography and paleoceanography abstract modern rhynchonellida terebratulida thecideida and a few inarticulated brachiopods were collected live or soon after death at 30 locations from depths of 2 3940 m from the equator to high latitudes covering the atlantic pacific indian caribbean and mediterranean oceans seas well preserved fibers of the secondary layer combined with sr 450 1928 mg kg mn 1 199 mg kg and fe 1 610 mg kg contents confirm with few exceptions the excellent preservation of the modern brachiopod material evaluation of the stable isotope compositions was conducted on 276 specimens and on 374 published samples for a total database of 650 samples from 80 locations it revealed that oxygen isotope incorporation into shell calcite secondary layer of modern articulated brachiopods in most cases occurs in equilibrium with the ambient water and as such reflects surrounding environmental conditions thecideida as a group shallow water and low latitude incorporate oxygen isotopes 3 04 to 0 35 into shell calcite in equilibrium with their ambient water a large majority of genera and species of the terebratulida shallow water and low mid latitude also incorporate oxygen 2 30 to 3 48 into shell calcite in isotopic equilibrium with their surrounding water in contrast equilibrium incorporation of oxygen isotopes into shell calcite by the rhynchonellida is uncertain but a vital effect probably applies to the craniida the question of equilibrium disequilibrium incorporation of carbon isotopes into shell calcite of modern brachiopods remains unresolved at this time isotope compositions range up to 4 5 5 6 and 1 5 for 13 c and up to 5 5 5 9 and 0 3 for 18 o for shallow water low mid and high latitude brachiopods respectively strontium isotopes of modern brachiopods as expected show no significant variation with location latitude water depth temperature salinity and general water conditions once local habitat and ecological influences of fossil brachiopods from similar latitudes are considered their isotopic elemental values should be valuable diagenetic indicators and important oceanographic chemostratigraphic proxies

reduced sea ice concentrations in the arctic ocean during the last interglacial period revealed by sediment cores off northern greenland 1 we present a record encompassing marine isotope stages 7 1 from a hitherto unexplored and heavily ice covered area of the arctic ocean the lomonosov ridge off the northern greenland canada continental margin using nannofossil and benthic foraminifera stratigraphy planktic foraminifera assemblages are used as a key paleoceanographic proxy and a surprisingly large variability is found for an interior arctic ocean site abundant small 63 125 m subpolar turborotalita quinqueloba occur in two sections possibly representing substages 5e last interglacial and 5a warm interstadial however the present day circulation pattern and the very distant location of high productive regions cannot explain such high abundances of subpolar specimens in the interior perennially sea ice covered arctic ocean hence our proxy record indicates that last interglacial sea ice concentrations were reduced off some areas of northern greenland canada whether this was part of a larger regional pattern or it represents the influence of polynya areas with locally increased productivity remains to be solved with respect to glacial conditions increased ice rafted debris ird deposition in the area appears to be associated with glacial stages 6 4 and late 3 stage 2 sediments including the last glacial maximum are condensed with a sparse ird content only

landscape chronology and glacial history in thule northwest greenland abstract constraining past responses of ice sheets to changes in climate enhances our ability to predict future changes in ice extent and sea level here we employ surficial geologic mapping stratigraphic analysis radiocarbon dating of marine mollusks and analysis of cosmogenic 10 be in glacially deposited boulders to make inferences about past ice extents in thule northwest greenland our work shows the existence of two distinct diamict units in the thule area we infer that one diamict was deposited by the main greenland ice sheet while the second was deposited by a subsequent outlet glacier re advance boulders in the two diamicts n 13 and n 15 respectively have similar bimodal distributions of cosmogenic 10 be ages both diamicts have a group of younger 10 be ages as well as a more diffuse group of considerably older 10 be ages 20 30 ka many of the boulders likely contain nuclides inherited from previous periods of exposure suggesting that glacial ice in the thule region has been cold based and non erosive in the past the landscape chronology we develop suggests that deglaciation after the last glacial maximum occurred 10 8 ka and was later followed by a re advance of outlet glaciers possibly in concert with the 9 3 ka or 8 2 ka cold events

facies and climate environmental changes recorded on a carbonate ramp a sedimentological and geochemical approach on middle jurassic carbonates paris basin france a detailed sedimentological geochemical and mineralogical study is carried out on the early bajocian to early callovian middle jurassic limestones of the paris basin objectives are to document and explain the facies changes in the context of the climate environmental evolution at the nw european scale deposits include 18 lithofacies which are stacked into 10 third order depositional sequences at a greater time scale 4 biosedimentary packages are distinguished by their allochems associations 1 an intracratonic carbonate environment with coral reefs and crinoid rich facies is typical of the early bajocian 2 a major facies change occurred at the early late bajocian transition with a shift from crinoid and coral rich facies to ooid rich facies during the late bajocian a southward dipping ooid ramp with successive progradational trends was emplaced 3 a large lagoon protected by ooid shoals developed during the bathonian in a muddy ramp setting 4 at the bathonian callovian boundary a second major change occurred with the lagoonal facies being superseded by an ooid bioclastic crinoids corals ramp associated with a waning of carbonate productivity retrogradational trend our geochemical study including a compilation of bibliographic data allows us to refine the existing sea surface palaeotemperature pattern a cooling from the latest early bajocian to the late bajocian and a subsequent warming from the earliest callovian to the early middle callovian transition are described using a proxy of sea surface temperatures together with 13c and mineralogical data our new 18o values suggest a palaeo climatic palaeo environmental control of facies in this shallow carbonate ramp environment

application of acoustic tomography to reconstruct the horizontal flow velocity field in a shallow river a novel acoustic tomographic measurement system capable of resolving sound travel time in extremely shallow rivers is introduced and the results of an extensive field measurements campaign are presented and further discussed acoustic pulses were transmitted over a wide frequency band of 20 35 khz between eight transducers for about a week in a meandering reach of theb sen river hiroshima japan the purpose of the field experiment was validating the concept of acoustic tomography in rivers for visualizing current fields the particular novelty of the experiment resides in its unusual tomographic features subbasin scale 100 m 270 m and shallowness 0 5 3 0 m of the physical domain frequency of the transmitted acoustic signals central frequency of 30 khz and the use of small sampling intervals 105 s inverse techniques with no a priori statistical information were used to estimate the depth average current velocity components from differential travel times zeroth order tikhonov regularization in conjunction with l curve method deployed to stabilize the solution and to determine the weighting factor appearing in the inverse analysis concurrent direct environmental measurements were provided in the form of adcp readings close to the right and left bank very good agreement found between along channel velocities larger than 0 2 m s obtained from the two techniques inverted quantities were however underestimated perhaps due to vicinity of the adcps to the banks and strong effect of river geometry on the readings in general comparing the visualized currents with direct nodal measurements illustrate the plausibility of the tomographically reconstructed flow structures

integrated stratigraphy radiolarians and calcareous nannofossils of the middle to upper jurassic alpine radiolarites lombardian basin italy constraints to their genetic interpretation abstract new biostratigraphic data obtained by integrating radiolarians and calcareous nannofossils document a depositional history for the middle to upper jurassic radiolarites of the italian southern alps characterized by strong fluctuations in the sedimentation rates associated to shifts from gravity driven to hemipelagic sedimentary process we studied the radiolarites in four sections located in different settings of the lombardian basin a rifted basin of the northern adriatic plate the sections studied were described and sampled in detail to obtain data on their lithology using facies and microfacies analysis and calcimetry and their nanno and microfossils content especially radiolarians and calpionellids an almost complete record of radiolarians was detected throughout the selcifero lombardo formation so that the radiolarian zonation uazs for the middle to upper jurassic interval partially integrated with calcareous nannofossil and calpionellid biostratigraphic data was successfully applied accordingly the lower member radiolariti correlates with the lower bathonian uaz 5 to the kimmeridgian uaz 11 interval and the upper member rosso ad aptici displays an age spanning from the kimmeridgian to the base of upper thitonian from uazs 10 11 to nannofossil njk zone we interpret the radiolarites as pelagic sediment relatively enriched in radiolarian during a long time span of basin starvation due to the near absence of periplatform exportation if we except bathonian a period of relatively higher sedimentation rates the radiolarites are characterized by very low sedimentation rates implying equally low radiolarian productivity therefore it is not necessary to claim for high tethyan water fertility during middle to late jurassic even if this latter condition likely played a role in the production exportation of the carbonate platforms

quaternary glacial and marine environmental history of northwest greenland a review and reappraisal new information on middle and late quaternary deposits of the thule region northwest greenland necessitates the revision of the chronostratigraphy of the area and allows fuller understanding of the marine environmental changes in ba n bay the stratigraphic record is interpreted as the product of three marine events saunders qarmat and nuna in decreasing age during which marine sedimentation occurred on coastal areas now land and three or four glacial events of decreasing age and ice cover agpat narsaarsuk and kap abernathy wolstenholme fjord to which the marine events were glacio isostatically related subarctic atlantic water reached this northern part of ba n bay during all three marine events but the warmest conditions warmer than the present occurred in the qarmat event correlated with the deep sea oxygen isotope stage 5e the question of late stage 5 events is considered the nuna event dates to latest stage 2 and the holocene whilst the saunders event is of uncertain age but at least stage 6 a number of glacial events with advances confined to the fjords are dated to stage 2 wolstenholme fjord and late stage 6 narsaarsuk and an intermediate advance kap abernathy is undated in the range of stage 2 5 extension of glaciation to the shelf edge is dated to stage 6 agpat event 1999 elsevier science ltd all rights reserved

palynostratigraphy and chronostratigraphy of baffin bay deep sea cores climatostratigraphic implications abstract palynostratigraphic considerations and 14c dates ams accelerator mass spectrometry on foraminifera samples from piston cores suggest sedimentation rates as high as ca 8 11 cm ka in deep baffin bay during the late pleistocene throughout this interval baffin bay experiences rigorous conditions and probably the extension of a dense sea ice cover unfavourable to phytoplanktonic productivity the dinocyst microflora indicates only brief episodes of higher productivity related to arctic conditions and to moderately low salinites ca 30 31 the abundance of reworked pre quaternary palynomorphs in the deposits is interpreted as a response to glacial and glacio marine activity in the northernmost areas surrounding baffin bay the dinocyst stratigraphy spanning approximately over the last ice age ca 100 ka reveals that baffin bay constituted a confined basin isolated from the north atlantic ocean prior to the present interglacial

holocene emergence at cape herschel east central ellesmere island arctic canada implications for ice sheet configuration twenty five radiocarbon age determinations on marine molluscs basal organic pond sediments charred remains in archeological sites and a variety of other materials have allowed the construction of an emergence curve for cape herschel east central ellesmere island 78 35 n 74 40 w only a narrow fringe of land is present between the prince of wales icefield and smith sound yet emergence of the order of 135 m has taken place during the last 8500 8700 radiocarbon years the highest in situ shells were collected at an elevation of 107 5 m and ages of 8470 100 bp gsc 3314 and 8230 70 bp to 230 were obtained on this material the spectacular and fresh appearing glacial sculpture along both sides of smith sound coupled with the rapid emergence in holocene time and the fact that the oldest dates on marine shells at the fiord heads to the west are 3000 4000 years younger than those at cape herschel provides convincing evidence that an ice stream filled smith sound 500 m deep during the late wis

dinoflagellate cyst evidence for warm interglacial conditions at the northern barents sea margin during marine oxygen isotope stage 5 dinoflagellate cyst analysis has been conducted on a sediment core from the northern barents sea margin eastern arctic ocean to reconstruct sea surface conditions during marine oxygen isotope stage 5 cyst concentrations and composition of assemblages display a distinct variability reflecting deglacial warming and the onset of relatively warm interglacial conditions in early stage 5 dinoflagellate cyst assemblages of the last interglacial which corresponds broadly to substage 5e are comparable with those from recent sediments of the area but have lower abundances of cold water taxa such assemblages suggest that sea surface temperatures of the last interglacial were therefore at least as warm as today or even warmer after a distinct cooling relatively stable cold conditions with minor periods of surface water warming prevailed from mid substages 5d to 5b temperatures might have been similar in substages 5a and 5e but the different compositions of assemblages indicate a stronger stratification of surface waters probably owing to a larger meltwater supply in substage 5a these results are compared with previous studies on marine carbonate and calcareous microfossil records from the fram strait and yermak plateau area which show that the general view of a cold last interglacial in the eastern arctic ocean is untenable copyright 2001 john wiley sons ltd

fluctuations of local glaciers in greenland during latest pleistocene and holocene time abstract this paper is the first to summarize research on fluctuations of local glaciers in greenland e g ice caps and mountain glaciers independent of the greenland ice sheet during latest pleistocene and holocene time in contrast to the extensive data available for fluctuations of the greenland ice sheet surprisingly little data exist to constrain local glacier extents much of the available research was conducted prior to wide spread use of ams radiocarbon dating and the advent of surface exposure and luminescence dating although there is a paucity of data generally similar patterns of local glacier fluctuations are observed in all regions of greenland and likely reflect changes in paleoclimate which must have influenced at least the margins of the inland ice absolute age data for late glacial and early holocene advances of local glaciers are reported from only two locations disko island and the scoresby sund region subsequent to late glacial or early holocene time most local glaciers were smaller than at present or may have disappeared completely during the holocene thermal maximum in general local glacier advances that occurred during historical time 1200 1940 ad are the most extensive since late glacial or early holocene time historical documents and more recent aerial photographs provide useful information about local glacier fluctuations during the last 100 yrs in all but one area north greenland local glaciers are currently receding from historical extents

evidence for major environmental perturbation prior to and during the toarcian early jurassic oceanic anoxic event from the lusitanian basin portugal the timing and causal relationships between the pronounced negative c isotope excursion and paleoenvironmental perturbations associated with the toarcian oceanic anoxic event early jurassic remain unclear particularly because biotic crises and carbonate production decrease appear to have been initiated earlier than the main c isotope anomaly here we present a new quantification of late pliensbachian early toarcian calcareous nannofossils abundance and size from the peniche reference section portugal together with o and c isotope records of well preserved brachiopod shells from the same section the brachiopod shell 13c curve parallels that of bulk carbonate and records two pronounced negative isotopic excursions close to the pliensbachian toarcian boundary 2 and during the toarcian oceanic anoxic event 3 5 our results indicate that both c isotope negative excursions were characteristic of benthic and shallow water environments suggesting that these two carbon cycle perturbations affected all epioceanic reservoirs coeval shifts toward lower values of brachiopod oxygen isotope compositions and closely correlated northward migrations of mediterranean ammonite fauna suggest that both events coincided with major rises in seawater temperatures probably as a result of increased co2 levels and enhanced greenhouse conditions co2 induced changes in seawater chemistry likely affected the calcification potential of both neritic and pelagic systems as evidenced by synchronous drops of platform derived carbonate accumulation and drastic reductions in size 3 m of the main pelagic carbonate producer schizosphaerella we suggest that the early toarcian paleoenvironmental crisis occurred in two distinct episodes that were most likely related to two successive phases of intense volcanic degassing in the karoo ferrar province

relative sea level changes since 15 000 cal yr bp in the nanortalik area southern greenland we present new results for relative sea level change for southern greenland for the interval from 9000 cal yr bp to the present together with earlier work from the same region this yields a nearly complete record from the time of deglaciation to the present isolation and or transgression sequences in one lake and five tidal basins have been identified using lithostratigraphic analyses sedimentary characteristics magnetic susceptibility saturated induced remanent magnetisation sirm organic and carbonate content and macrofossil analyses ams radiocarbon dating of macrofossils and bulk sediment samples provides the timescale relative sea level fell rapidly and reached present day level at similar to 9300 cal yr bp and continued falling until at least 9000 cal yr bp between 8000and6000cal yrbpsea level reached its lowest level of around similar to 10m below highest astronomical tide at around 5000 cal yr bp sea level had reached above 7 8 m below highest astronomical tide and slowly continued to rise not reaching present day sea level until today the isostatic rebound caused rapid isolation of the basins that are seen as distinct isolation contacts in the sediments in contrast the late holocene transgressions are less well defined and occurred over longer time intervals the late holocene sea level rise may be a consequence of isostatic reloading by advancing glaciers and or an effect of the delayed response to isostatic rebound of the laurentide ice sheet one consequence of this transgression is that settlements of palaeo eskimo cultures may be missing in southern greenland copyright c 2006 john wiley sons ltd

chronology of the last recession of the greenland ice sheet a new deglaciation chronology for the ice free parts of greenland the continental shelf and eastern ellesmere island canada is proposed the chronology is based on a new compilation of all published radiocarbon dates from greenland and includes crucial new material from southern northeastern and northwestern greenland although each date provides only a minimum age for the local deglaciation some of the dates come from species that indicate ice proximal glaciomarine conditions and thus may be connected with the actual ice recession in addition to shell dates dates from marine algae lake sediments peat terrestrial plants and driftwood also are included only offshore and in the far south have secure late glacial sediments been found other previous reports of late glacial sediments older than 11 5 cal kyr bp from onshore parts of greenland need to be confirmed most of the present ice free parts of greenland and nares strait between greenland and ellesmere island were not deglaciated until the early holocene copyright c 2002 john wiley sons ltd less

assimilation of coastal acoustic tomography data into a barotropic ocean model a data assimilation technique was applied to analyze the first coastal acoustic tomography data obtained in the neko seto channel of the seto inland sea japan on march 2 3 1999 the ensemble kaiman filter technique accompanied by the forecast of error covariances by means of the monte carlo method is found to be best fitted to the present problem because currents in the tomography region are dominated by the strongly nonlinear tidal vortices furthermore the analyzed results are in better agreement with the shipboard adcp results than those obtained by the inverse analysis of the travel time difference data for the pairs of acoustic stations

deciphering kinetic metabolic and environmental controls on stable isotope fractionations between seawater and the shell of terebratalia transversa brachiopoda this study presents carbon and oxygen stable isotope data obtained from high resolution sampling 500 m of the brachiopod terebratalia transversa from the san juan islands washington state usa the aim of this study is to unravel the respective effects of physiological and environmental controls on the stable isotopic composition of brachiopod shell calcite based on an sem study of the shell a three dimensional sampling was performed in order to investigate carbon and oxygen isotope variations along isochrons and ontogenetic transects the primary as well as the outer part of the secondary shell layer display large and variable isotopic offsets as high as 7 for 13c and 6 for 18o relative to expected equilibrium values the significant positive correlations between 18o and 13c values indicate that the isotopic compositions of these shell domains are mainly controlled by kinetic isotope fractionation effects the ontogenetic 13c and 18o variations can be used to establish a growth curve of the studied specimen whose age is estimated close to 8 years the extent of apparent o 18 disequilibrium observed in this study is about as large as any yet measured in any organism which makes this brachiopod an interesting and important case the carbon and oxygen isotope compositions increase from the outer towards the inner part of the secondary layer where they reach values of 0 0 8 and 0 8 to 0 2 respectively corresponding calculated temperatures are between 12 and 13 8 c and fall in the range of seawater temperatures recorded off the san juan islands 7 13 c these results suggest that the calcite fibres were secreted more and more slowly during the thickening of the shell throughout the animal s life finally approximating isotopic equilibrium this study illustrates that the stable isotopic composition of the modern brachiopod t transversa is predominantly influenced by kinetic fractionation and to a minor degree by metabolic effects except for the innermost part of the shell the measured isotope ratios do not reflect environmental conditions during shell precipitation it remains to be tested by comparable studies whether other modern brachiopod species or even fossil brachiopods reflect comparable fractionation effects these results point out the need for re examination of paleozoic oceanographic conditions

middle jurassic coccolith fluxes a novel approach by automated quantification coccolithophores major pelagic carbonate producers underwent important changes during the latest aalenian early bajocian ca 170 ma middle jurassic specifically a new genus called watznaueria diversified and started dominating the coccolith assemblages while this change in the coccolith assemblages is already known the impact on coccolith absolute abundances and fluxes is still misunderstood here we tested for the first time on mesozoic deposits an automated counting method using the syraco system and then compared these results with a classic counting method two neural networks were created based on the shape birefringence and size of coccoliths the first of which contained only one class and the second of which was composed of six classes based on the morphological criteria used for the neural networks coccoliths were not identified at the species level we quantified coccolith absolute abundances and estimated fluxes for the latest aalenian early bajocian in two well dated and correlated sections cabo mondego in portugal and chaudon norante in france there is a strong linear correlation between classic and automatic counting r 0 8 supporting the latter as a reliable method for coccolith absolute abundance and flux quantification in spite of under or over estimation by automatic counting with respect to classic counting the absolute abundance stratigraphic trends are remarkably similar under or over estimation may be reduced by further technical improvements such as automatic focus at cabo mondego coccolith fluxes increased from 0 2 109 coccoliths m2 yr in the latest aalenian to 700 109 coccoliths m2 yr in the middle of the laeviuscula ammonite zone early bajocian remaining high for the rest of the early bajocian at chaudon norante a similar trend was observed this coccolith flux increase is therefore considered to be a supra regional event matching an important 13cbulk carbonate positive excursion the carbon isotopic positive excursion along with the onset of radiolarian sedimentation and coccolith fluxes is related to a gradual increase in the fertility of the oceans during the early bajocian and is likely associated with warmer and more humid climates and associated enhanced continental weathering

reconstruction of the glacial ice covers of greenland and the canadian arctic islands by three dimensional perfectly plastic ice sheet modelling a three dimensional perfectly plastic ice sheet model developed for determining the surface elevations and the flow pattern of an ice sheet with given bottom topography and ice margin positions is applied to the reconstruction of the glacial ice covers of greenland and the canadian arctic islands in the northern regions two different reconstructions have been performed with ice margins along the present 600 and 200 m sea depth contours respectively in central greenland the ice margin is considered to be at the outermost ice margin deposits on the coastal shelf to the west and at the present 200 m sea depth contour to the east the main conclusions to be drawn from the reconstructions are 1 the flow pattern of the glacial ice cover of greenland shows a great resemblance to the present one the central ice divide being displaced less than 50 km from its present position and being no more than 200 m higher than today 2 the main ice divide of the ice sheet covering the canadian arctic islands the innuitian ice sheet was located over the highlands of eastern ellesmere island with local domes positioned over the present ice caps indicating that even the deep ice of wisconsin age in these ice caps is of local origin this is also the case for the devon island ice cap 3 even in the not very likely case of a rather extensive glacial ice cover in north west greenland the ice flow pattern upstream of the camp century deep drill site would not have changed radically compared to the present flow pattern thus it is concluded that even advanced ice margins in late wisconsin time could at most have resulted in an elevation of the deposition site of the late wisconsin ice at camp century 600 m higher than at present the consequences of this conclusion are discussed

acoustic tomography in the florida strait temperature current and vorticity measurements various aspects of near bottom ocean variability including the alongshore temperature and current the cross slope temperature the onshore offshore flow and the area averaged relative vorticity on the western slope of the florida strait near 27 n have been measured with a three point acoustic reciprocal transmission three pairs of reciprocal travel time data were extracted from acoustic pulse responses of a 1983 august triangular transmission experiment temperatures and currents were estimated from the sum and difference respectively of reciprocal travel times and an area averaged vorticity was estimated from circulation following stokes theorem the estimations agree well with the concurrent direct measurements at two nearby moorings low frequency fluctuations of temperatures currents and vorticity show a strong weekly period clearly and consistently describing a near bottom onshore offshore water movement on the western slope in association with the gulf stream meanders

pronounced summer warming in northwest greenland during the holocene and last interglacial projections of future rates of mass loss from the greenland ice sheet are highly uncertain because its sensitivity to warming is unclear geologic reconstructions of quaternary interglacials can illustrate how the ice sheet responded during past warm periods providing insights into ice sheet behavior and important tests for data model comparisons however paleoclimate records from greenland are limited early holocene peak warmth has been quantified at only a few sites and terrestrial sedimentary records of prior interglacials are exceptionally rare due to glacial erosion during the last glacial period here we discuss findings from a lacustrine archive that records both the holocene and the last interglacial lig from greenland allowing for direct comparison between two interglacials sedimentary chironomid assemblages indicate peak july temperatures 4 0 to 7 0 c warmer than modern during the early holocene maximum in summer insolation chaoborus and chironomids in lig sediments indicate july temperatures at least 5 5 to 8 5 c warmer than modern these estimates indicate pronounced warming in northwest greenland during both interglacials this helps explain dramatic ice sheet thinning at camp century in northwest greenland during the early holocene and for the lig aligns with controversial estimates of eemian warming from ice core data retrieved in northern greenland converging geologic evidence for strong lig warming is challenging to reconcile with inferred greenland ice sheet extent during the lig and the two appear incompatible in many models of ice sheet evolution an increase in lig snowfall could help resolve this problem pointing to the need for hydroclimate reconstructions from the region

last interglacial arctic warmth confirms polar amplification of climate change the warmest millennia of at least the past 250 000 years occurred during the last interglaciation when global ice volumes were similar to or smaller than today and systematic variations in earth s orbital parameters aligned to produce a strong positive summer insolation anomaly throughout the northern hemisphere the average insolation during the key summer months m j j was ca 11 above present across the northern hemisphere between 130 000 and 127 000 years ago with a slightly greater anomaly 13 over the arctic greater summer insolation early penultimate deglaciation and intensification of the north atlantic drift combined to reduce arctic ocean sea ice allow expansion of boreal forest to the arctic ocean shore across vast regions reduce permafrost and melt almost all glaciers in the northern hemisphere insolation amplified by key boundary condition feedbacks collectively produced last interglacial summer temperature anomalies 4 5 c above present over most arctic lands significantly above the average northern hemisphere anomaly the last interglaciation demonstrates the strength of positive feedbacks on arctic warming and provides a potentially conservative analogue for anticipated future greenhouse warming

an acoustic travel time method for continuous velocity monitoring in shallow tidal streams 1 long term variations of streamflow in a tidal channel were measured using a fluvial acoustic tomography fat system through one transmission path fat is an innovative acoustic technology that utilizes the time of travel method to determine velocity between two points from multiple ray paths that traverse the entire cross section of stream due to high spatial variability of flow distribution stationary adcp measurements were not likely to yield true section averaged flow velocity and moving boat adcp method was therefore used to provide reference data as such two short term moving boat adcp campaigns were carried out by the authors in the first campaign a couple of acoustic stations were added to the fat system in order to resolve flow angularity in addition to the mean velocity comparing the fat results with corresponding adcp section averaged flow direction and velocity indicated remarkable consistency second campaign was designed to capture the influence of salt wedge intrusion on the sound propagation pattern it was found that fat velocity measurements bias high if acoustic stations lay inside the cooler freshwater layer ray tracing hindcasts suggest that installing acoustic stations inside the salt wedge may significantly improve function of output of the system comparing salinities evaluated from long term fat travel time records with nodal salinity measurements provided by conductivity temperature sensors reveals the potential ability of fat in measuring salt flux

multivariate analysis and quantitative paleoecology of benthic foraminifera in surface and late quaternary shelf sediments northern canada abstract benthic foraminifera in surface sediments from northeastern canada and the beaufort shelf were studied to determine the quantitative relationship between recent assemblage distributions and modern water depth temperature and salinity factor analysis shows that 7 factor assemblages account for 92 of the variance between samples multiple linear regression shows that different factors are significantly related to water depth august bottom water temperature or salinity multiple correlation coefficients for depth temperature and salinity are 0 94 0 72 and 0 92 respectively labrador fjords contain arenaceous faunas dominated by eithersaccammina atlantica andreophax fusiformis or byeggerella advena regression analysis shows that thesaccammina reophax factor is most strongly related to salinity theeggerella factor is related to depth and temperature a fauna dominated bytrochammina nana andbuliminella elegantissima is correlated with warm deep water in davis strait calcareous assemblages dominated byelphidium excavatum orcassidulina reniforme are found in arctic bays and shelf areas these factor assemblages are strongly related to temperature and depth cassidulina is also related to salinity anislandiella helenae fauna on the inner labrador shelf is strongly correlated with depth and salinity anonionellina labradorica fauna in deep shelf basins is closely related to salinity the multiple regression model for the sea bed data estimates water depth august bottom water temperature and salinity within confidence limits of 67 m 1 3 c and 1 0 paleoecological transfer functions were used to quantify environmental changes recorded by the foraminifera in two piston cores on a transect across the labrador shelf paleo depth estimates obtained from the core data produce relative sea level curves which are similar in shape to theoretical curves for this region paleo salinity and temperature estimates for offshore core 12 show that the change from a postglacialnonionellina fauna to a late glaciale excavatum fauna is accompanied by a decrease of about 2 in salinity and 4 c in temperature paleoecological estimates for fjord core 111 show that the change from a modernsaccammina reophax fauna to a mid holocenei helenae fauna corresponds to a salinity increase of 3 5 and temperature increase of 1 2 c

deciphering processes controlling mid jurassic coccolith turnover the middle jurassic is characterized by major changes within the fossil coccolithophorid community with a transition from lotharingius dominated to watznaueria dominated assemblages concomitant with a significant increase in the pelagic carbonate production the mechanisms that triggered this overturn remain poorly understood here we present a compilation new and previously published data of lotharingius and watznaueria abundances through the early middle jurassic transition alongside this trends in newly acquired and literature derived carbon and oxygen isotope data were used to represent paleoceanographic indicators such as nutrient and temperature changes the nannofossil data show a rapid around 1 5 myr turnover around the aalenian bajocian transition across the aalenian bajocian boundary assemblages dominated by lotharingius spp give way to assemblages dominated by watznaueria spp coinciding with a peak in a particular morphological group of watznaueria species with a cross in the central area the proliferation of this morphogroup occurred during a time of oceanic opening and rearrangement of ocean circulation this led on to the evolution of pioneering coccolithophorid taxa but also to extinctions in several marine groups in the early bajocian the proliferation of two other morphogroups watznaueria without a central area structure and watznaueria with a bar corresponds to the major diversification of watznaueria and the beginning of its meso zoic dominance the watznaueria diversification and dominance are associated with radiation in other marine groups and these biotic changes occurred during a time of putative enhanced oceanic fertility and relatively low temperatures this study suggests that restructuring of fossil coccolithophorid communities may be favored during short turnover intervals related to major paleoceanographic change

history of the greenland ice sheet paleoclimatic insights abstract paleoclimatic records show that the greenland ice sheet consistently has lost mass in response to warming and grown in response to cooling such changes have occurred even at times of slow or zero sea level change so changing sea level cannot have been the cause of at least some of the ice sheet changes in contrast there are no documented major ice sheet changes that occurred independent of temperature changes moreover snowfall has increased when the climate warmed but the ice sheet lost mass nonetheless increased accumulation in the ice sheet s center has not been sufficient to counteract increased melting and flow near the edges most documented forcings and ice sheet responses spanned periods of several thousand years but limited data also show rapid response to rapid forcings in particular regions near the ice margin have responded within decades however major changes of central regions of the ice sheet are thought to require centuries to millennia the paleoclimatic record does not yet strongly constrain how rapidly a major shrinkage or nearly complete loss of the ice sheet could occur the evidence suggests nearly total ice sheet loss may result from warming of more than a few degrees above mean 20th century values but this threshold is poorly defined perhaps as little as 2 c or more than 7 c paleoclimatic records are sufficiently sketchy that the ice sheet may have grown temporarily in response to warming or changes may have been induced by factors other than temperature without having been recorded

ice sheet extent and early deglacial history of the southwestern sector of the greenland ice sheet the offshore and coastal geomorphology of southwest greenland records evidence for the advance and decay of the greenland ice sheet during the last glacial maximum regional ice flow patterns in the vicinity of sisimiut show an enlarged ice sheet that extended southwestwards on to the shelf with an ice stream centred over holsteinsborg dyb high level periglacial terrain composed of blockfield and tors is dated to between 101 and 142 ka using 26al and 10be cosmogenic exposure ages these limit the maximum surface elevation of the last glacial maximum ice sheet in this part of southwest greenland to ca 750 810 m asl and demonstrate that terrain above this level has been ice free since mis 6 last glacial maximum ice thickness on the coast of ca 700 m implies that the ice sheet reached the mid to outer continental shelf edge to form the outer hellefisk moraines exposure dates record ice surface thinning from 21 0 to 9 8 ka with downwasting rates varying from 0 06 to 0 12 m yr 1 this reflects strong surface ablation associated with increased air temperatures running up to the bolling interstadial gis1e at ca 14 ka and later marine calving under high sea levels the relatively late retreat of the itilleq ice stream inland of the present coastline is similar to the pattern observed at jakobshavn isbrae located 250 km north in disko bugt which also retreated from the continental shelf after ca 10 ka we hypothesise that the ice streams of west greenland persisted on the inner shelf until the early holocene because of their considerable ice thickness and greater ice discharge compared with the adjacent ice sheet

holocene palaeoceanographic changes in barrow strait canadian arctic foraminiferal evidence holocene changes in the benthic and planktic foraminiferal fauna 63 m from a marine sediment core arc 3 canadian arctic archipelago 74 16 050 n 91 06 380 w water depth 347 m show that significant environmental and palaeoceanographic variations occurred during the last 10 ka foraminiferal assemblages are restricted to the ca 4 5 10 ka interval as younger samples are mostly barren of foraminifera due to intense carbonate dissolution after ca 4 5 ka foraminiferal assemblages in the ca 4 5 10 ka interval are dominated by the benthic species islandiella helenae and cassidulina reniforme 57 of total with elphidium clavatum cibicides lobatulus and buccella frigida also being common in this interval the dominance of these species indicates a seasonal sea ice regime which is consistent with the occurrence of the sea ice diatom derived organic geochemical biomarker ip25 throughout the core the abundances of c reniforme and e clavatum decline upcore consistent with more frequent mixing of the barrow strait water column during the early holocene it is likely that the influence of co2 rich arctic surface water masses have caused an increase in bottom water corrosivity after ca 8 5 ka and dissolution has been further enhanced by sea ice related processes after ca 6 ka concomitant with increased ip25 fluxes dissolution is strongest when ip25 fluxes are highest suggesting a link between the sea ice and benthic systems copyright 2010 john wiley sons ltd

carbon cycle perturbation in the middle jurassic and accompanying changes in the terrestrial paleoenvironment abstract carbon isotope analyses of fossil wood from the middle jurassic ravenscar group yorkshire ne england reveal a significant excursion toward light isotopic values 13c change of 3 to 4 at about the aalenian bajocian boundary 174 ma a positive carbon isotopic excursion is also shown for the middle bajocian 170 ma but is less clearly defined these isotopic patterns are very similar to the few published marine carbonate records available for this time in particular one based on belemnites from the hebrides basin nw scotland and others from pelagic limestones in italy the similarity of the terrestrial and marine isotope curves is an indication that the observed isotopic signal is a global phenomenon through parts of the ravenscar group the scarborough formation supplementary data from bulk organic carbon and palynofacies analysis confirm that isotopic curves based on bulk analyses may be strongly influenced by the balance of terrestrial versus marine organic matter present in th

a model of greenland ice sheet deglaciation constrained by observations of relative sea level and ice extent an ice sheet model was constrained to reconstruct the evolution of the greenland ice sheet gris from the last glacial maximum lgm to present to improve our understanding of its response to climate change the study involved applying a glaciological model in series with a glacial isostatic adjustment and relative sea level rsl model the model reconstruction builds upon the work of simpson et al 2009 through four main extensions 1 a larger constraint database consisting of rsl and ice extent data model improvements to the 2 climate and 3 sea level forcing components 4 accounting for uncertainties in non greenland ice the research was conducted primarily to address data model misfits and to quantify inherent model uncertainties with the earth structure and non greenland ice our new model termed huy3 fits the majority of observations and is characterised by a number of defining features during the lgm the ice sheet had an excess of 4 7 m ice equivalent sea level iesl which reached a maximum volume of 5 1 m iesl at 16 5 cal ka bp modelled retreat of ice from the continental shelf progressed at different rates and timings in different sectors southwest and southeast greenland began to retreat from the continental shelf by 16 to 14 cal ka bp thus responding in part to the bolling allerod warm event c 14 5 cal ka bp subsequently ice at the southern tip of greenland readvanced during the younger dryas cold event in northern greenland the ice retreated rapidly from the continental shelf upon the climatic recovery out of the younger dryas to present day conditions upon entering the holocene 11 7 cal ka bp the ice sheet soon became land based during the holocene thermal maximum htm 9 5 cal ka bp air temperatures across greenland were marginally higher than those at present and the gris margin retreated inland of its present day southwest position by 40 60 km at 4 cal ka bp which produced a deficit volume of 0 16 m iesl relative to present in response to the htm warmth our optimal model reconstruction lost mass at a maximum centennial rate of c 103 4 gt yr our results suggest that remaining data model discrepancies are affiliated with missing physics and sub grid processes of the glaciological model uncertainties in the climate forcing lateral earth structure and non greenland ice particularly the north american component finally applying the huy3 greenland reconstruction with our optimal earth model we generate present day uplift rates across greenland due to past changes in the ocean and ice loads with explicit error bars due to uncertainties in the earth structure present day uplift rates due to past changes are spatially variable and range from 3 5 to 7 mm a including earth model uncertainty

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

bio and aminostratigraphy of some quaternary marine deposits in west greenland 14c dates and the geological setting of quaternary marine deposits from three sites in west greenland indicate a pre holocene age the mollusc faunas at the sites are distinctly different although

holocene relative sea level changes in the inner bredefjord area southern greenland in this paper we present new relative sea level data from southern greenland a key area for understanding the greenland ice sheet gis response to climate change within fourteen lakes and marine lagoons from the inner part of bredefjord nordre sermilik in southern greenland isolations revealed by stratigraphic and palaeoecological analyses are dated and relative sea levels reconstructed due to coastal emergence caused by the gis retreat within the area the relative sea level fell rapidly in the early holocene between at least c 9600 and c 7300 cal yrs bp attaining a rate of 2 cm per year between 9600 and 8000 cal yrs bp spatial variability in relative sea level changes is show for southern greenland from a comparison with the nanortalik and the qagortoq areas the regression occurred about 2000 years later in the inner bredefjord area compared to the nanortalik area and about 1000 years later compared to the qaqortoq area this is a consequence of earlier deglaciation in areas located at the outer coast between c 8000 cal yrs bp and the present day relative sea level was lower than today the lowest relative sea level in the inner bredefjord area of between 5 4 and 15 m a h a t above highest astronomical tide was reached between 7000 and 1000 cal yrs bp the neoglacial readvance together with the collapse of the laurentide peripheral bulge is probably responsible for the transgression in the inner bredefjord area as has been indicated from the nearby sites qagortoq and nanortalik our relative sea level reconstructions showing spatial variability within southern greenland have implications for glacial isostatic adjustment gia modelling and the understanding of the gis ice sheet dynamics the early holocene regression is consistent with the recession of the southern sector of the gis from the shelf edge at c 22 000 cal yrs bp reaching inland of the present day outer coast by c 12 000 cal yrs bp and its present margin by c 10 500 cal yrs bp c 2013 elsevier ltd all rights reserved

timing and warmth of the last interglacial period new u series evidence from hawaii and bermuda and a new fossil compilation for north america abstract the timing and duration of the last interglacial period have been controversial with some studies suggesting a relatively short duration that is orbitally forced and others suggesting a long duration that is at most only partly related to orbital forcing new high precison thermal ionization mass spectrometric tims u series ages of last interglacial corals from hawaii and bermuda test these competing hypotheses waimanalo formation corals from slowly uplifting oahu hawaii range in age from 134 to 113 ka with most ages between 125 and 115 ka combined with published u series ages from nearby lanai the data suggest a long last interglacial period that may have occurred from 136 to at least 115 ka the results indicate that orbital forcing may not have been the only control on ice sheet growth and decay because sea level would have been high at times of relatively low northern hemisphere summer insolation on tectonically stable bermuda deposits from the 200 ka penultimate interglacial period 120 ka peak last interglacial period and 80 ka late last interglacial period high sea stands have been newly dated fossil corals on bermuda are derived from patch reefs that likely were catch up responses to sea level rise it is expected that u series ages of last interglacial corals on bermuda should overlap with but not be as old as the range of corals on oahu last interglacial corals on bermuda give a range of 125 113 ka which supports this hypothesis a large number of emergent marine deposits on hawaii bermuda and along coastal north america have now been dated to the last interglacial period both oahu and bermuda have marine invertebrate faunas with a number of extralimital southern species of mollusks suggesting warmer than present waters during the last interglacial period warmer waters are also suggested for last interglacial localities around most of north america from florida to canada and greenland and baja california to alaska these observations are consistent with similar warm water faunas of last interglacial age reported from japan the mediterranean basin and western australia it is likely that significant changes in ocean currents took place during the last interglacial period with a movement of relatively warm waters to higher latitudes than is the case today

black shales and carbon isotopes in pelagic sediments from the tethyan lower jurassic detailed sampling and analysis of jurassic pelagic limestones and marls from italy hungary and switzerland have enabled construction of an isotope stratigraphy across the pliensbachian toarcian boundary with resolution to the zonal level the oxygen isotope record is unremarkable the carbon isotopes however show two positive excursions one relatively minor during the pliensbachian margaritatus zone subnodosus subzone the other more major during the toarcian early falciferum zone where a maximum 13c value of 4 52 pdb is attained these intervals are known to be favoured periods of organic rich sedimentation in diverse parts of the globe and the isotopic excursions are interpreted as a response to abnormally high rates of storage of organic carbon in the sedimentary record a comparable phenomenon has been documented from the cenomanian turonian boundary in the cretaceous where it has been referred to the influence of an oceanic anoxic event some italian sections spanning this lower jurassic interval contain organic rich shales in the falciferum zone the isotopic signatures from their included locally manganiferous carbonate betray a considerable diagenetic overprint and they cannot therefore be incorporated in a composite isotopic curve carbon isotopes from the organic carbon itself are extremely negative falling to 33 pdb and in one section examined in detail correlate with the calcium carbonate content of the shales they may reflect a partial change to a non calcified planktonic biota during deposition of this lime poor interval possibly responding to upwelling and increased fertility of near surface waters the onset of upwelling may have been as early as spinatum tenuicostatum zone time that is at the pliensbachian toarcian boundary

δ18o and δ13c values of modern brachiopod shells abstract researchers have not rigorously tested the hypothesis that calcite from modern brachiopod shells is precipitated in oxygen isotope equilibrium with ambient seawater isotopic variability at the intraspecimen and intertaxon levels has not been examined without such data for modern brachiopods similar data from ancient brachiopods cannot be accurately interpreted in this study a survey is made of 18 o and 13 c values of terebratulid rhynchonellid thecideidine and craniacean brachiopods from antarctica the bay of fundy curacao japan new zealand norway puget sound palau sicily and south africa this suite of samples provides a wide range of taxonomic levels temperatures salinities and depositional environments for evaluating the degree of isotopic equilibrium attained during precipitation of brachiopod calcite new data indicate that modem brachiopod calcite is not always precipitated in oxygen and carbon isotope equilibrium with ambient seawater calcite from the primary layer and specialized shell structures hinge brachidium foramen interarea muscle scars are depleted in both 18 o and 13 c a characteristic of biological fractionation or vital effects often found in other calcerous marine organisms our findings suggest that these portions of the brachiopod shell should be avoided during sampling of ancient brachiopods secondary layer calcite the material most often analyzed in ancient brachiopods has higher 18 o and 13 c values which approach and sometimes correspond with predicted equilibrium values therefore secondary layer calcite is the most suitable portion of the brachiopod shell for use as an ancient seawater proxy although near equilibrium precipitation in secondary layer calcite is encouraging to those studying the isotopic composition of ancient oceans these data come with caveats large intraspecimen variability in the 18 o values of secondary layer calcite 1 in some samples limits the use of brachiopods as precise indicators of the 18 o value or temperature of ancient seawater the 18 o and 13 c values of secondary layer calcite deviate from predicted equilibrium values toward the lower values of the primary layer and specialized shell structures indicating a measurable vital effect in most cases measured 18 o values are lower than the calculated equilibrium values dictated by seasonal variations in the 18 o value and temperature of seawater ontogenetic variations in the 13 c values of secondary layer calcite have also been measured and must be assessed when interpreting ancient data modern brachiopods occur in a wide range of seawater salinities and temperatures therefore the relation between salinity and the 18 o value of seawater must be known to correctly calculate the temperature of calcite precipitation from secondary layer 18 o values errors of up to 15 c are found if ambient seawater is assumed to have a constant 18 o value e g 0 smow and the 18 o values of secondary layer calcite are used to calculate temperature coupled with vital effects and intraspecimen variability these errors can obscure the resolution of secular variations in the rock record

strontium isotope variations in middle jurassic late bajocian callovian seawater implications for earth s tectonic activity and marine environments abstract strontium isotope ratios of well preserved belemnite rostra and ammonite shells are presented from stratigraphically well dated upper bajocian callovian sediments of the polish jura chain in central poland nekto benthic belemnites show a narrow trend of changes of 87 sr 86 sr ratio that are interpreted to record secular variations in the strontium isotope composition of seawater a new fit of the seawater strontium isotope curve for the late bajocian callovian is presented based on current and literature data the data show a gradual decrease of seawater 87 sr 86 sr ratio throughout the late bajocian earliest middle callovian lowest 87 sr 86 sr ratios 0 706850 and the flat minimum of the curve were reached in the latest middle and the late callovian the middle jurassic decrease in seawater 87 sr 86 sr ratio is interpreted to have been a result of the increased volcanic activity of the seafloor studied nektonic ammonites are considered to have lived in surface or shallow near coastal waters of the polish jura chain basin and been affected by the freshwater influx a slight enrichment of ammonite shells in 87 sr isotope is linked to a change in strontium isotope composition of the surface or near coastal waters due to the riverine strontium input

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr