effect of wind scouring on climatic records from ice core oxygen isotope profiles removal of winter snow by wind explains why the annual mean oxygen isotope ratio at an ice divide is 2 5 less negative than it is 1 2 km downslope cores from two sites on an ice cap ellesmere island canada show past variations in the difference depending on where the ice originated relative to the scoured zone some ice core climatic records may need correction for scouring

controls on the basinwide architecture of late miocene messinian evaporites on the levant margin eastern mediterranean abstract interpretation of 2d and 3d seismic data from the levant margin eastern mediterranean has revealed the complex depositional and structural setting of the basinwide late miocene messinian evaporites the data set covers a total area of 20 000 km2 permitting a semi regional investigation of the thick up to 1 8 km evaporitic wedge the sequential analysis of time structure maps isochron maps and seismic cross sections highlighted the main morphological and structural features characterizing the pre syn and post evaporitic levant margin this approach provided insights on the impact of local vs regional factors in governing the distribution of the messinian salinity crisis in the region two regional features have been recognized as the most significant controlling factors for the architecture of the messinian evaporites firstly a series of anticlines of the syrian arc foldbelt acted as a structural barrier indirectly governing the overall landward extension of the evaporites secondly submarine canyons active in the area at least since the oligocene afiq el arish and ashdod canyons represented preferential sites of erosion and deposition of evaporites our results document therefore the importance of the deep seated structures and relict drainage for the architecture of the messinian evaporites on the levant margin the new insights provided can be additionally used to infer the original depositional geometry of the evaporites in the study area and as an analogue in other mediterranean areas where 3d seismic is not available yet and sub salt imaging is limited

messinian evaporites and fluid flow abstract thick evaporite sequences deposited in saline giant basins are traditionally viewed as impermeable barriers to fluid flow this paradigm has recently been challenged by documented evidence of fluid migration pathways through several km thick series of evaporites such as the late miocene messinian sediments in the mediterranean basin deposited during the messinian salinity crisis msc our paper reviews the occurrence of fluid expulsion events in these evaporites in the depocentres of the basin and analyses their potential as seal bypass systems the messinian salt giant was deposited in peculiar conditions where massive sea level changes occurred in a relatively limited time interval and a thick basin centre evaporitic series was deposited between pre msc and post msc deep water sediments consequently rapid water and sediment loading unloading events contributed to the creation of overpressures up to fracture and possibly lithostatic gradient causing the fluids to be released in explosive events examples of fluid expulsion events are here grouped and classified in relation to the long and short term effects of the messinian salinity crisis as well as the local controls and pre conditioning basin factors while peaks of fluid expulsion activity during the short time frame of the msc can be mainly linked to mediterranean wide events local controls appear to play a major role in post msc fluid mobilisation in these cases evaporite breach is largely dependent on the availability of pre msc undersaturated fluid sources and the capability of the pre msc sediments to be overpressured the analysis here presented can be used as a basis to understand the controls on syn and post depositional movement of fluids in sedimentary basins moreover the analysis of temporal and spatial distribution of fluid expulsion events can help define hydrocarbon migration style and pathways in deep seated petroleum plays

holocene paleoclimatology of the queen elizabeth islands canadian high arctic abstract a wide variety of evidence reflecting in different ways the changing climate of the queen elizabeth islands during the holocene is reviewed all proxies pertain to summer conditions many sources of information provide weak or equivocal paleoclimatic signals but a general pattern of events can be discerned temperatures in the early to mid holocene were highest comparable with or higher than temperatures prevailing for much of this century although much evidence points to a mid holocene thermal maximum there is also considerable evidence that conditions were warmer in the early holocene possibly related to orbitally induced radiation anomalies the apparent mid holocene thermal maximum may reflect lags in the response of the environment and of some proxies in recording paleoclimatic conditions more direct indices point to warmest conditions in the early holocene before 7500 bp temperatures declined from 3000 bp culminating in exceptionally low temperatures from 100 400 bp this may have been the coldest period of the entire holocene resulting in glacier advances to post glacial maximum positions the period since 1925 has witnessed a pronounced increase in temperature leading to negative mass balances on glaciers and ice sheets throughout the archipelago this period is the warmest for at least 1000 years and perhaps for several thousand years modern climate in the queen elizabeth islands may thus be characteristic of the early to mid holocene and atypical of conditions which prevailed for much of the last few thousand years

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

regional isostatic response to messinian salinity crisis events abstract the salinity crisis of the mediterranean during messinian time was one of the most dramatic episodes of oceanic change of the past 20 or so million years resulting in the deposition of kilometer thick evaporitic sequences a large and rapid drawdown of the mediterranean water level caused erosion and deposition of non marine sediments in a large lago mare basin both the surface loading by the lower messinian evaporites and the removal of the water load resulted in isostatic flexural rebound that significantly affected river canyons and topographic slopes we use flexure models to quantitatively predict possible signatures of these events and verify these expectations at well studied margins the highly irregular shape of the reconstructed basin calls for a three dimensional model near basin margins plate bending effects are most pronounced which is why flexure is particularly important for a relatively narrow basin like the mediterranean we focus on one specific sea level scenario for the messinian salinity crisis where most of the evaporite load was deposited during a sea level highstand followed by a rapid desiccation evaporite loading at current sea level is expected to cause subsidence of the deep basins by hundreds of meters and simultaneous uplift of continental parts of the margins differential uplift may lead to significant slope angle changes and thus gravity flows the relative scarcity of lower evaporite sequences along the margins may be a result of these phenomena normal faulting of lower evaporite and older sediments and rocks is expected on the margins desiccation enhances erosion of the freshly exposed continental shelf and slope subsidence and riverbed sedimentation occurs on the continental margins and significant uplift towards the basin center reverse faulting is predicted at the margins finally regional isostatic uplift following zanclean flooding is predicted to destabilize margin slope deposits and to cause marginal uplift river down cutting and normal faulting

the potential effects of percolating snowmelt on palynological records from firn and glacier ice the effects of meltwater percolation on pollen in snow firn and glacial ice are not fully understood and currently hamper the use of pollen in ice core studies of paleoclimate several studies have suggested that due to grain size pollen is not mobilized by meltwater transport however these findings contradict many ice core pollen studies that show pollen concentrations in snow and firn are much higher than concentrations found in the ice layers they eventually form this study addresses one aspect of this question by investigating whether meltwater percolation can effectively transport pollen within a snowpack we used nine styrofoam coolers filled by natural snow accumulation the coolers were tested in three groups of three replicates each to simulate different glacier snowpack conditions and spiked at the surface with a known amount of lycopodium marker spores the snow was melted to two thirds the original volume sampled stratigraphically and tested for spore concentrations meltwater effluent was also collected and examined results show substantial vertical and horizontal spore transport during the experiment peak spore concentrations were found in the bottommost snow layer or in the meltwater effluent in eight of nine coolers indicating that the majority of surface spores were transported through the snowpack via meltwater percolation and or runoff

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

late holocene environmental conditions in coronation gulf southwestern canadian arctic archipelago evidence from dinoflagellate cysts other non pollen palynomorphs and pollen boxcore 99lssl 001 68 0958 n 114 1868 w 211 m water depth from coronation gulf represents the first decadal scale marine palynology and late holocene sediment record for the southwestern part of the northwest passage the record was studied for organic walled microfossils dinoflagellate cysts non pollen palynomorphs pollen terrestrial spores and sediment characteristics 210 pb 137 cs and three accelerator mass spectrometry 14 c dates constrain the chronology three prominent palaeoenvironmental zones were identified during the interval ad 1470 1680 zone i the climate was warmer and wetter than at present and environmental conditions were more favourable to biological activity and northward boreal forest migration with reduced sea ice and a longer open water growing season the interval ad 1680 1940 zone ii records sea ice increase and generally cool polar conditions during the little ice age during ad 1940 2000 zone iii organic microfossils indicate an extended open water season and decreased sea ice with suggested amelioration surpassing that of zone i although more marine studies are needed to place this record into an appropriate context the succession from ameliorated zone i to cooler sea ice influenced conditions zone ii and finally to 20th century warming zone iii corresponds well with several terrestrial climatic records from the neighbouring mainland and victoria island and with lower resolution marine records to the west copyright 2011 john wiley sons ltd

setting and tectonic evolution of some eastern mediterranean deep sea basins abstract nine discrete deep sea basins seven from the calabrian and mediterranean ridges and two from the strabo trench were explored geologically during several cruises carried out from 1978 to 1984 in the eastern mediterranean the seven basins displaying similar geological features calabrian and mediterranean ridges may be divided into three groups on the basis of their size 1 very small basins botticelli and raffaello basins whose area ranges from 1 1 to 4 3 km 2 2 small basins ares aphrodite and katia basins from 7 to 13 km 2 and 3 large basins bannock and cleft basins from 22 to 74 km 2 the two basins from the strabo trench tyro and kretheus basins whose areas range from 16 to 20 km 2 are considered separately tectonics is the most important element affecting basin formation processes progressive folding and faulting of messinian pliocene and quaternary sediments in the calabrian and mediterranean ridges allows the infiltration of water into the subbottom and dissolution of messinian evaporites so that collapse of the overlying unconsolidated plio quaternary cover creates local distensive tectonics superimposed on the regional compressive tectonic setting the size of the basins reflects different steps in this process very small basins are related to the fracturing occurring at the top of anticlines small basins originate when anticlines are faulted and large amounts of water are able to reach the evaporites and increase the intensity of leaching finally large basins are related to regional tectonic lineaments both compressive large reverse faults overthrusts and strike slip salt diapirism may be associated with some of these situations the process responsible for the tyro and kretheus basins formation is the pull apart mechanism connected with the strike slip motion occurring in that area the geometric position of subaqueously dissolved evaporites seems to influence the environment on the basin floor brines originating from the dissolution of buried evaporites are thought to disperse in the subbottom whereas brines originating from dissolution of evaporites cropping out on the basin walls can flow to the floor and cause stagnation only if the shape of the basin prevents the action of bottom currents

ephemeral thermal and solute plumes formed by upwelling groundwaters near salt domes geochemical observations made by previous workers indicate that rapid upward advection of hot water has occurred along the flanks of some salt domes in the northern gulf of mexico basin and in the danish central trough the observations are based on pore fluid chemistry and on high temperatures of formation of metal sulfides and other diagenetic minerals near the crests of salt domes some of the diagenetic minerals formed at 40 c to 80 c above the ambient temperature of the host rocks numerical simulations of coupled heat and dissolved salt transport show that thermal perturbations in excess of 60 c can be repeatedly produced near the crest of a salt dome by focused dewatering of a thick strongly overpressured sedimentary interval around the dome in our simulations dewatering was triggered and stopped by cyclically changing the permeability at the salt sediment interface the thermal plumes dissipated within 100 kyr after dewatering ceased stratigraphically shallow brine plumes were also formed by dewatering and these gravitationally unstable plumes dissipated more slowly by sinking within 1 m y simulations showed that free thermohaline convection can also generate thermal perturbations near the crest of a dome in this mode of upwelling thermal perturbations reached 30 c when the vertical permeability of the hydrostatically pressured interval was 10 14 m2 10 mdarcy because such permeabilities seem large for the hydrostatically pressured interval as a whole in the northern gulf of mexico basin the formation of high temperature metal sulfide deposits near the crests of salt domes seems more likely to be due to dewatering of the overpressured interval with very strong focusing of expelled waters along the flanks of salt domes

stratigraphy and palaeoecology of a possible interglacial site northernmost ellesmere island canada an extensive stratigraphic section at cape alfred ernest on the wootton peninsula northwest ellesmere island contains six lithofacies which appear to record two glacial phases separated by an organic layer 1 a lower massive gravel records a pre ice advance outwash phase 2 massive fine grained sediments record a period of non glacial marine deposition when sea level was higher than present 3 a massive diamicton records the advance of ice across the site 4 intermediate stratified beds record supraglacial and proglacial outwash and include an organic layer 5 massive diamicton grading down valley to stratified diamicton and then massive sheared diamicton overlain by laminated fine grained sediments with dropstones recording the last late wisconsinan glaciation 6 upward coarsening sands and gravels record proglacial outwash and grade to raised marine deltas radiocarbon dates of 39270 640 and 51000 yr bp were obtained on samples from the organic layer by accelerator mass spectrometry and conventional radiocarbon dating respectively palaeoecological data suggest that the organics accumulated in a wet sedge meadow environment when the climate was warmer than present stratigraphic considerations suggest that the organic layer represents an interglacial interval which if valid indicates that the site constitutes the northernmost interglacial stratigraphy in the canadian arctic alternatively the organic layer may date to plio pleistocene times

a holocene ice core pollen record from ellesmere island nunavut canada abstract a holocene record of pollen deposition was obtained from an ice core drilled through the agassiz ice cap the pollen records long range atmospheric transport to the ice cap pollen concentrations were highest in the early holocene 15 grains l decreased in the mid holocene 6 grains l and increased in the late holocene 9 grains l in the early holocene the higher concentration of tree pollen at a time when large parts of canada were still ice covered and when forest was generally farther away implies that atmospheric circulation was stronger than at present following deglaciation as vegetation migrated north in central and eastern canada sources of pollen were closer to the agassiz ice cap however the concentration of tree pollen decreased on the ice cap this was followed by several relatively rapid changes after 3500 yr ago until ca 3500 yr ago the pollen concentration curves resembled the ice core 18 o and summer melt layer curves both regarded as temperature proxies

modern pollen distribution in marine sediments from the northern part of the south china sea we analyzed the pollen and spore distributions in sediments from the northern south china sea to support reconstruction of the region s paleoenvironment 1 based on pca analysis in the two areas with water depths of 200 m pollen and spores found at water depths of 200 m wind transport is dominant 2 tree pollen was abundant on the continental shelves near guangdong and southeastern hainan island the center of the study area and deep basins in the south pinus pollen was abundant with the highest levels on the continental shelf near guangdong and in the marine area south of 15 degrees n pollen from tropical and subtropical broad leaved trees e g castanopsis quercus had low abundances castanopsis pollen appeared to originate near hainan island guangdong and the indochina peninsula herbaceous pollen was less abundant with pollen from the poaceae and artemisia scattered among the northern and southern regions with the highest levels near guangdong and a distribution that followed the rivers or sea surface circulation poaceae pollen was most abundant along the guangdong and vietnam coasts due to their proximity to tropical and subtropical grasslands and crops monolete spores and cyperaceae pollen were most abundant near the pearl river estuary southern hainan island and southwestern taiwan probably originating from fluvial river discharge trilete spores mostly dicranopteris were most abundant on the continental shelf of southeastern hainan island and the continental slope far from guangdong 3 pollen and spore assemblages from airborne sea surface water and sediment samples were compared from august to september airborne pollen and spores mainly belong to trees ulmaceae pinus and herbaceous pollen and have seasonal characteristics ocean surface waters in august september mainly contain d dichotoma rhizoma polypodiodis nipponicae and other trilete spores but no pinus pollen with clear seasonality characteristic pollen and spore assemblages in surface sediments are dominated by trilete spores pinus and herbaceous pollen and appear to integrate the pollen characteristics of the four seasons c 2014 elsevier b v all rights reserved

a modern pollen spectrum from dye 3 south greenland ice sheet results of pollen analysis of a large firn sample from dye 3 southern greenland are reported the sample was divided into three sections all dominated by pine birch and ragweed pollen pollen concentration for the entire sample is 15 pollen grains per litre and the annual pollen deposition rate has been estimated at approximately 0 73 grains cm 2 year 1 7300 grains m 2 a 1 although these values are slightly lower than expected considering the relatively southern latitude of the site they are within the range of values obtained from other arctic ice caps

late quaternary pollen transport processes western north atlantic data from box models cross margin and n s transects abstract surface pollen assemblages in coastal and neritic sediments of the western north atlantic compare well with eastern north american vegetation zones and late quaternary pollen in marginal marine sediments clearly correlate with changes in terrestrial vegetation and paleoclimates in contrast offshore assemblages are strongly affected by differential adaptation of pollen to long distance transport by wind and water marine pollen transport processes were studied by measuring air and water inputs to a coast shelf box model and by study of surface samples from cross margin transects in three different climatic and oceanographic regions at approximately 38 45 and 55 n latitude the box model shows that aerial transport is the main process by which pollen moves across the continental margin off nova scotia two clear seabed distribution patterns were found betula quercus and herb pollen decrease rapidly offshore in abundance grains per cubic centimetre and in relative abundance percentage pinus and picea have abundance peaks on the continental margin but percentages increase further offshore distributions of the main pollen and spore taxa were compared for late wisconsinan glacial oxygen isotopic stage 2 12 28 ka terminal pleistocene 10 12 ka and holocene sediments at 5 continental margin and 3 deep sea sites the largest changes were found in percentages of pinus picea and herb pollen during the late wisconsinan glacial and terminal pleistocene intervals at subpolar latitudes these data can be related to shifts in paleo vegetation winds and hydrology that accompany global climate change

younger dryas pollen records from sverdrup island kara sea abstract sverdrup island in the kara sea is currently occupied by polar desert vegetation the analysis of allerod deposits indicates a climate drier than presently with increased summer and decreased winter temperatures the relative scarcity of distal pollen indicates that mainland source areas were located further south than at present younger dryas cooling and increased dryness resulted in an increase of the proportions of artemisia chenopodiaceae and salix pollen and in the extent of sphagnum mosses preboreal time was marked by warmer more humid conditions with dwarf birches ericales and possibly alnus fruticosa the increased proportions of distally derived arboreal birch pollen coupled with the local component of the assemblages indicates that the early holocene represented the climatic optimum initiated by the opening of the arctic ocean subsequent climate fluctuations were muted on sverdrup island due to the development of microclimatic conditions associated with an oceanic regime

dating of seasonal snow firn accumulation layers using pollen analysis reliable chronologies in ice cores and snow pits from many alpine glaciers in latitudes between 60 n and 60 s are often difficult to establish owing to problems with annual layer counting problems arise from melting wind erosion and the negligible amount of precipitation in some seasons all of which tend to obscure the seasonal variations in 18 o and chemical concentrations that are typically used to date ice cores however alpine glaciers contain many species of pollen grains that peak at particular times of the year we used the peaks in betulaceae pinus artemisia and a combination of abies and picea pollen species to determine the four seasonal layers of a snow pit on belukha glacier in russia s altai mountains comparing the pollen dated profiles with wind and precipitation records allows us to determine where a seasonal layer is missing thus the pollen dating method described here may be a useful tool to measure the annual snow deposition on alpine glaciers even when some seasonal layers are eroded by wind or missing due to negligible precipitation

chemical composition and crystal structure of merrillite from the suizhou meteorite merrillite ideally ca9namg po4 7 is an important accessory phosphate mineral in many different groups of meteorites including martian meteorites and a major carrier of rare earth elements ree in lunar rocks by means of electron microprobe analysis single crystal x ray diffraction and raman spectroscopy we present the first structure determination of merrillite with a nearly ideal chemical composition ca9 00na0 98 mg0 95fe0 06 1 01 p1 00o4 7 from the suizhou meteorite a shock metamorphosed l6 chondrite suizhou merrillite is trigonal with space group r 3 c and unit cell parameters a 10 3444 3 c 37 0182 11 a and v 3430 5 2 a3 its crystal structure refined to r 1 0 032 is characterized by a structural unit consisting of a mg fe po4 6 16 complex anion that forms a bracelet and pinwheel arrangement such structural units are linked by interstitial complexes with a formula of ca9na po4 16 which differs from that of ca9 po3 oh 16 ca9 po3f 16 ca9 ca0 5 0 5 po4 16 or ca9 xree x na1 x x po4 16 in terrestrial whitlockite terrestrial extraterrestrial bobdownsite meteoritic ca rich merrillite or lunar ree rich merrillite respectively the suizhou merrillite is found to transform to tuite at high pressures pointing to the likelihood of finding ree bearing tuite on the moon as a result of shock events on ree merrillite

long distance transport of pollen to greenland 1 four pollen traps were recently placed at coastal sites in east and west greenland in order to assess long distance transport of pollen to the arctic domain by identifying potential vegetation source areas associated with air mass pathways we were able to produce the first detailed record of pollen transport from eastern north america to narsarsuaq southern greenland the record is based on observations and on a transport and dispersion model used to calculate back trajectories of the air masses the evidence points to the pollen being transported northward by the air mass over newfoundland and the labrador sea before reaching narsarsuaq at this point the air mass was at an altitude of 3000 m deposition of pollen grains occurred with downward air movements associated with a 0 5 mm h rain the source areas for these pollen grains differ from those of dust and certain other aerosols that reach the summit of the greenland ice sheet the results demonstrate the need for continued maintenance and analysis of the greenland pollen trap data in order to improve our understanding of atmospheric circulation and transport to high northern latitudes

pollen analysis of the 1973 ice core from devon island glacier canada abstract meltwater from a 299 m long ice core was filtered and analyzed for fossil pollen and spores pollen concentration was higher in the late holocene and interglacial intervals ca 7 liter 1 than in the early holocene and wisconsinan ca 1 2 liter 1 ones the late holocene and interglacial assemblages were dominated by alnus alder whereas the early holocene and wisconsinan ones were dominated by betula birch and artemisia sage during the holocene and probably the last interglaciation most of the pollen and spores were blown a minimum of 1000 km from low arctic shrub tundra and adjacent subarctic picea spruce forest these areas were dominated by the arctic air mass during the summer pollinating season during the wisconsinan early holocene glacier ice and arctic air were more widespread and pollen sources were more distant thus at this time relatively little pollen was incorporated into the ice the devon ice core data suggest that there should have been pollen in the continental ice sheet of wisconsin time when the ice sheet retreated this pollen would be carried by meltwater and redeposited with silt and clay together with contemporary pollen producing an ecologically anomalous assemblage

upper cenozoic history of the labrador sea baffin bay and the arctic ocean a paleoclimatic and paleoceanographic summary foraminifera palynomorphs and stable isotopes in planktonic foraminifera have been studied in piston cores from the northern labrador sea southern baffin bay and the alpha ridge region of the central arctic ocean foraminifera in cores from the labrador sea and southern baffin bay show glacial interglacial 18o values similar to those reported from the norwegian and greenland seas in contrast to the eastern north atlantic ocean however peaks of subarctic foraminifera and dinoflagellates in the western north atlantic cores show that relatively warm atlantic surface water continued to flow into the northern labrador sea during the early glaciation growth phases of isotopic stages 2 4 6 and 8 boreal and subarctic pollen suggest that warm atlantic air flowed into the northern labrador sea and baffin bay during the ice sheet growth phases the advection of warm air masses and the presence of open waters during the summer probably provided moisture for the growth of the laurentide innuitian and greenland ice sheets isotopic and microfossil records in arctic cores can also be tentatively correlated with major high latitude north atlantic glacial interglacial events magnetostratigraphic palynological and amino acid dating however shows that sedimentation on the alpha ridge has been very slow during the past 0 73 m y therefore events of less than 20 000 years duration cannot be clearly discerned interpretation of pre pleistocene paleoenvironments is further limited by the sparseness of calcareous and siliceous microfossils

paleoenvironments of the canadian high arctic derived from pollen and plant macrofossils problems and potentials abstract analyses of peat sections lake sediments and ice cores provide information about late quaternary arctic environments palynomorphs and plant macrofossils from each of these three types of sediments record different aspects of the environment with particular spatial and temporal scales of resolution in the arctic the limits to the interpretation of past environments are particularly significant problems of low pollen concentrations long distance transport stratigraphic inversions and contamination by fossils from older deposits are more serious in this region due to the biogeographic context that characterizes these high latitudes and influences the particular ecological and geomorphological processes however recent work has shown that past environments can be reconstructed from evidence preserved in high arctic sediments and ice cores if these problems are taken into account before their interpretation

modern and late quaternary pollen spectra of fiord sediments eastern baffin island arctic canada abstract pollen spectra of thirty surface samples from baffin island fiords are dominated by abetula filicales cyperaceae gramineae association that is somewhat representative of local or regional vegetation however betula and filicales are over represented andsalix cyperaceae and ericales are under represented compared to their importance in the present vegetation two possible causes for this disparity related to the fluvial processes that furnish most pollen to fiords are 1 fluvial reworking of older sediment that contains abundantbetula and filicales and 2 greater resistance of these taxa to corrosion and degradation during fluvial transport the pollen stratigraphy of five piston cores from fiords contains two types of pollen assemblages in the lower portions of the cores exotic pollen types and pre quaternary palynomorphs are abundant the upper portions of the cores contain an assemblage roughly representative of the present vegetation in which cyperaceae and gramineae are abundant and exotic and pre quaternary types are reduced or absent the lower assemblage was deposited during the late glacial deglacial transition and deglaciation ca 12 000 to 6000 b p when eastern baffin island had little vegetation cover and long distance transport and reworking were virtually the only pollen sources a feature of several cores is a major peak in dinoflagellates about 5000 b p this event may be related to the postglacial marine climatic optimum in the eastern canadian arctic between 5000 and 3000 b p

modern and holocene pollen assemblages from some small arctic lakes on somerset island nwt canada abstract modern pollen samples from 15 lakes along a north south transect on western somerset island nwt canada show a decrease in pollen concentrations from the high arctic to the mid arctic zone but there are few differences in the pollen percentages between these sites long distance transport accounts for up to 50 of the pollen in these lake sediments cores from two lakes show few changes in the percentages of important pollen types except for an initial period before 6000 yr b p of increased salix the pollen concentration of lake rs36 from the mid arctic is twice that of lake rs29 from the high arctic and at both sites the concentrations decreased during the past 6000 yr b p this suggests a climatic deterioration during the past 6000 yr which has caused a decrease in the abundance of plants on the landscape

application of pollen analysis to dating of ice cores from lower latitude glaciers 1 ice cores from temperate regions have long been expected to be useful for understanding local climate trends but a reliable dating method has proved difficult here we show that measurements of pollen using samples with only 10 ml of water can give an accurate measure of the annual ice accumulation in addition two major types of pollen allow us to estimate the summer ice accumulation as well as the annual accumulation

giant solution subsidence structure in the western mediterranean related to deep substratum dissolution terra nova 24 181 188 2012 abstract sinkholes are frequently observed where soluble rocks are present in meteoritic recharge areas or when subsurface dissolution causes ground collapse seismic profiles on the inner shelf of the gulf of lions w mediterranean display a giant atypical sub circular structure up to 800 m thick and 2 km wide it is characterized by down warped internal seismic reflections forming a concave v shaped depression rooted in the substratum most likely carbonated this structure is interpreted as a poly phased solution subsidence collapse structure of plio quaternary age the last phase of deformation probably occurred during the last sea level low stand phase the mechanism proposed for the creation of this structure is collapse dissolution of the soluble substratum as a result of a combination of several possible factors including pre existing deep messinian palaeo karst with active groundwater flows during plio quaternary lowstands and deep rooted acidic fluids ascending through the substratum

modelling of thermal convection in sedimentary basins and its relevance to diagenetic reactions abstract mathematical calculations of thermal convection have been carried out using a porous three player model to simulate pore water flow in a sedimentary basin with layers of different permeabilities the calculated flow lines demonstrate that even very thin layers eg around salt domes and igneous or hydrothermal intrusions analyses of formation waters from sedimentary basins like the north sea often show evidence of a crude stratification of the pore water with respect to salinity and isotopic composition this is evidence suggesting that large scale convection or other types of mixing does not take place and positive salinity depth gradient may help to physically stabilize the formation water the fact that many of the shallow reservoir rocks from the north sea have formation water with low salinity and negative 18 o values suggest that this is modified meteoric water and that migration of petroleum from deeper parts of the basin occurred as a separate phase along restricted migration pathways and was not associated with a high flux of pore water in the absence of thermal convection the total pore water flux through sandstones will be rather small except locally where we may have focused compactional flow through small cross sections diagenetic reactions will therefore normally be relatively isochemical during deeper burial