from greenhouse to icehouse organic walled dinoflagellate cysts as paleoenvironmental indicators in the paleogene abstract dinoflagellates are an important component of the extant eukaryotic plankton their organic walled hypnozygotic cysts dinocysts provide a rich albeit incomplete history of the group in ancient sediments building on pioneering studies of the late 1970s and 1980s recent drilling in the southern ocean has provided a wealth of new dinocyst data spanning the entire paleogene such multidisciplinary studies have been instrumental in refining existing and furnishing new concepts of paleogene paleoenvironmental and paleoclimatic reconstructions by means of dinocysts because dinocysts notably exhibit high abundances in neritic settings dinocyst based environmental and paleoclimatic information is important and complementary to the data derived from typically more offshore groups as planktonic foraminifera coccolithophorids diatoms and radiolaria by presenting case studies from around the globe this contribution provides a concise review of our present understanding of the paleoenvironmental significance of dinocysts in the paleogene 65 25 ma representing earth s greenhouse icehouse transition this episode holds the key to the understanding of extreme transient climatic change we discuss the potential of dinocysts for the reconstruction of paleogene sea surface productivity temperature salinity stratification and paleo oxygenation along with their application in sequence stratigraphy oceanic circulation and general watermass reconstructions

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

paleocene sea level and productivity changes at the southern tethyan margin el kef tunisia integrated analysis of quantitative distribution patterns of organic walled dinoflagellate cysts dinocysts and benthic foraminifera from the paleocene el kef section nw tunisia allows the reconstruction of sea level and productivity fluctuations our records indicate that the environment evolved from an initially oligotrophic open marine outer neritic to upper bathyal setting towards a more eutrophic inner neritic setting influenced by coastal upwelling by the end of the paleocene an overall second order change in paleodepth is reflected by both microfossil groups from the base of planktic foraminifera zone p4 onwards the main phase of shallowing is evidenced by an increase of inner neritic dinocysts of the areoligera group disappearance of deeper water benthic foraminifera and increasing dominance of shallow marine taxa several buliminids haplophragmoides spp trochammina spp the total magnitude of this shallowing is obscured by interaction with a signal of eutrophication but estimated to be around 150 m from 200 to 50 m superimposed on the overall trend third order sea level fluctuations have been identified and correlated to sequences in other regions paleoproductivity indicators notably protoperidinioid dinocysts and buliminids show a trend from an oligotrophic to a eutrophic setting d 2005 elsevier b v all rights reserved

dinoflagellate cysts sea level changes and planktonic foraminifers across the cretaceous tertiary boundary at el haria northwest tunisia abstract dinoflagellate cysts and planktonic foraminifers have been studied from the cretaceous tertiary k t boundary interval at el haria northwest tunisia a high resolution integrated biostratigraphy is presented the k t boundary is drawn at the level of extinction of cretaceous planktonic foraminifers and is coincident with the first occurrence of the dinoflagellate cyst species danea californica the final extinction of planktonic foraminifers is foreshadowed by a reduction in their total abundance some 5 kyr earlier at the base of the boundary clay this reduction is coeval with reported anomalies in siderophyle elements and 13 c values in the same area dinoflagellate cysts do not show accelerated rates of extinction at k t time associations of dinoflagellate cysts however change drastically and parallel changes in relative numbers of sporomorphs spores and pollen and in the quantity of land derived organic matter jointly these changes reflect a rapidly falling sea level during the final 17 kyr of the mesozoic which culminates at the level of the k t boundary this steep sea level fall at k t time represents a peak regressive pulse at the end of the well documented latest cretaceous regressive trend this short term sea level fall might show to be a wide spread phenomenon which could have caused an excess shrinking of the already reduced areal extent of marginal seas since deep waters in cretaceous oceans were primarily produced in shallow marginal seas the rate of formation of deep water might have been minimized at k t time minimum rates of formation of deep water might have curtailed the slow upward mixing of relatively cool and nutrient rich deeper water through which the thermocline weakened and surficial waters became depleted in nutrients consequently phytoplankton productivity rapidly diminished which in combination with a weakened thermal gradient pushed the highly depth stratified cretaceous planktonic foraminiferal fauna to extinction over a period of time of some 5 kyr guembelitria cretacea was the sole planktonic foraminifer which could accommodate to the low productivity conditions the oscillating rise in sea level at the beginning of the cenozoic reinforced the upward mixing of relatively cool and nutrient rich deeper water steepened the thermocline and replenished the photic layer with nutrients concomitant niche differentiation in the photic layer progressively stimulated morphological innovation amongst early cenozoic planktonic foraminifers the final return of normally sized planktonic foraminifers and of stable and well balanced dinoflagellate cyst associations at about 125 kyr after the k t boundary seems to indicate that primary productivity and niche differentiation in the photic layer begin to revert to optimum levels the earliest cenozoic planktonic foraminiferal species globoconusa minutula and parvularugoglobigerina fringa are thought to have developed from a benthic foraminiferal species rather than having a planktonic ancestry

early oligocene dinoflagellate cysts from the upper rhine graben sw germany paleoenvironmental and paleoclimatic implications using principal component analysis and cyst diversity and equity trends we can recognize four distinct dinoflagellate cyst dinocyst assemblages from four rupelian early oligocene cores in the mainz embayment of the northern rhine graben sw germany these assemblages are the spiniferites ramosus pc1 thalassiphora pelagica pc2 homotryblium tenuispinosum pc3 and vozzhennikovia spinula pc4 assemblages the four cores provide an onshore offshore transect in the mainz embayment the h tenuispinosum assemblage shows high factor loadings in proximal to intermediate cores which is interpreted to reflect temporary high salinity conditions mean dinocyst diversity and equity increase with distance from the mid rupelian shoreline indicating increasingly stable paleoenvironmental conditions towards the center of the mainz embayment within individual cores changes in dinocyst assemblages through time are related to paleoenvironmental and paleoclimatological changes the three proximal to intermediate cores show dominance of the h tenuispinosum assemblage repeatedly alternating with high factor loadings of the t pelagica assemblage in both cases dinocyst diversity and equity tend to be reduced highest factor loadings of the s ramosus assemblage occur in intervals where neither of the above assemblages is dominant and tend to coincide with dinocyst diversity and equity maxima we interpret this distribution pattern to denote different paleoceanographic conditions reflecting drier and more humid phases in the early oligocene of central europe during relatively dry periods increased salinity conditions prevailed in proximal to intermediate settings of the mainz embayment as reflected by the dominance of the h tenuispinosum assemblage during more humid periods increased runoff led to higher nutrient availability and the formation of a pycnocline separating slightly less saline surface waters from higher saline deeper waters thus impeding vertical circulation these environmental conditions are documented in high loadings of the t pelagica assemblage which is indicative of increased eutrophication and or oxygen depleted bottom waters transitions between drier and more humid periods i e episodes of normal marine conditions are characterized by high loadings predominantly of the s ramosus assemblage as well as increased dinocyst diversity and equity values we propose that the alternations between drier and more humid phases may be related to variations in the ocean atmosphere moisture flux from the north atlantic into central europe bearing a high latitude climate signal 2002 elsevier science b v all rights reserved

late eocene to early oligocene dinoflagellate cysts from the priabonian type area northeast italy biostratigraphy and paleoenvironmental interpretation abstract marginal marine late eocene through early oligocene dinoflagellate cyst successions have been studied from the type area of the priabonian stage northeast italy the results allow the recognition of dinoflagellate zones previously defined in bio and magnetostratigraphically well calibrated pelagic sequences from central italy thus providing a first order correlation of the priabonian stage to the standard chronostratigraphic scale with unprecedented precision within this detailed biostratigraphic framework successive shifts in the composition of the dinoflagellate cyst assemblages are interpreted in terms of sea level and sea surface temperature sst fluctuations the evaluation of ecologically and sedimentary controlled changes in the composition of dinoflagellate cyst assemblages in combination with sequence stratigraphic analysis allows the reconstruction of third and fourth order sea level fluctuations the third order sea level fluctuations appear to correspond to exxon cycles ta4 1 4 5 the stratigraphically and palaeoenvironmentally important late eocene dinoflagellate cyst species glaphyrocysta priabonensis sp nov is formally described

morphological and abundance variations in homotryblium cyst assemblages related to depositional environments uppermost oligocene lower miocene jylland denmark abstract abundant occurrences of homotryblium dinoflagellate cysts have been interpreted as reflecting deposition in near shore marginal marine areas either in hypersaline or low salinity environments it has also been suggested that the process length of homotryblium cysts is related to proximity to the coast the present study provides new insights in the ecology of homotryblium and adds important information about the use of the morphological variations of homotryblium cysts for environmental reconstructions it presents an example where homotryblium cysts show high relative abundances in a low salinity partly restricted marine depositional environment four different species of homotryblium were recorded homotryblium additense is proposed as a new species the regional palaeogeographic distribution of the four species h additense homotryblium vallum homotryblium plectilum and homotryblium tenuispinosum shows a distinct depositional proximal distal distribution pattern h additense occurs only in a narrow stratigraphic interval in the most proximal part of the study area h vallum only occurs sporadically mainly in the proximal parts of the study area h plectilum dominates the proximal areas while h tenuispinosum dominates the more distal areas variations in abundance and cyst type also seem to respond to systems tracts sequence boundaries and flooding surfaces the observed distributional patterns of homotryblium species strongly indicate a response to the salinity of the depositional environment it is further suggested that at least some of the recorded species of homotryblium originated from the same motile dinoflagellate species producing cysts of different morphology in response to variations in salinity a phenomenon known from extant dinoflagellates

mixed layer evolution in the sea of okhotsk observed with profiling floats and its relation to sea ice formation 1 the time evolution of the ocean mixed layer in the seasonal sea ice zone of the okhotsk sea has been observed with profiling floats the heat storage rate in the mixed layer estimated from the float data well coincides with the surface heat flux mixed layer deepening and the onset of ice formation can be well reproduced by a bulk mixed layer model suggesting that onset of ice formation can be predicted by local atmospheric conditions this explains the remarkably high correlation of the onset day of sea ice formation with the surface heat loss in the preceding fall the anomalously large heat loss in the fall of 2000 led to the anomalously early ice formation strong stratification due to the amur river fresh water flux is indispensable for ice formation through suppression of deep convection

eocene stratigraphy of the north sea basin abstract the eocene of the north sea basin has been divided into five stratigraphic sequences named the dornoch balder frigg alba and grid the palaeocene eocene boundary lies at the base of the dornoch sequence whereas the grid extends into the lower oligocene the sequences display consistent and predictable patterns on electric log data and are bounded by high gamma log peaks which mark thin condensed claystone sections the sequences have been calibrated using a detailed dinocyst zonation that recognizes a succession of 30 biovents it can be shown that individual sequence boundaries consistently fall within the same dinocyst subzone giving a high degree of confidence that these boundaries represent time lines the sequences can be mapped over the whole of the north sea basin retaining their internal character from quadrant 3 in the north to quadrants 21 and 22 in the south a distance of 400 km the high gamma peaks marking the sequence boundaries are interpreted as surfaces of maximum condensation that record the effect of greatly reduced sediment input into the basin these surfaces are believed to have a variety of origins including eustatic sea level rise changes in sediment supply to the basin and changes in rates of tectonic subsidence or uplift

solutions in chronostratigraphy the paleocene eocene boundary debate and aubry vs hedberg on chronostratigraphic principles abstract in several recent papers m p aubry et al have argued that hedbergian principles of chronostratigraphy are being violated by the international commission on stratigraphy ics when selecting global stratotype sections and points gssps for the formal divisions of the geological time scale the current debate over the definition of the paleocene eocene p e boundary has been a major focus of their arguments unfortunately aubry et al have obscured matters by misusing the term unit stratotype and by equivocally using the term stage for the very different concepts of synthem and global chronostratigraphic stage the p e boundary option most repugnant to aubry et al carbon isotope excursion cie p e thanetian ypresian boundary is perfectly compatible with h d hedberg s views in contrast another option preferred by aubry et al recognition of new 1 m y duration age stage between thanetian and ypresian is inconsistent with hedberg s views additional problems with the p e boundary arguments of aubry et al include the fact that a ypresian unit stratotype does not exist the fact that the base of the ypresian synthem is not immutable and the fact that the nannofossil tribrachiatus digitalis is of dubious relevance to the boundary debate as for chronostratigraphy in general aubry et al have misrepresented hedberg s views by 1 falsely claiming that the content of a stage is what determines its boundaries 2 misunderstanding the general concept of the boundary stratotype 3 distorting the base defines boundary principle 4 falsely claiming that traditional pre gssp chronostratigraphic boundaries cannot be changed 5 falsely implying that traditional stage unit stratotype boundaries can be adjusted by no more than 300 000 years when defining formal age stage boundaries with gssps 6 falsely claiming that the definition of a geochronologic chronostratigraphic boundary should precede its correlation 7 claiming that traditional unconformable stage boundaries may be suitable horizons for gssps 8 distorting the meaning of arbitrariness in regard to the definition of geochronologic chronostratigraphic boundaries and 9 claiming that gssps are inherently unstable in that they are subject to redefinition whenever a more powerful element of correlation is discovered if taken seriously the unit stratotype sanctifying chronostratigraphic philosophy of aubry et al would require the creation of perhaps dozens of new phanerozoic ages stages of relatively very short duration wherever there was a significant gap between two successive historical stage unit stratotypes for all of these reasons the arguments of aubry et al have no merit

frazil ice entrainment of sediment large tank laboratory experiments laboratory experiments that simulate natural ice formation processes and sediment entrainment in shallow water are presented a 10 30 cm s 1 current was forced with impellers in a 20 m long 1 m deep indoor tank turbulence in the flow maintained a suspension of sediments at concentrations of 10 20 mg l 1 at 0 5 m depth low air temperatures 15 c and 5 m s 1 winds resulted in total upward heat fluxes in the range 140 260 w m 2 the cooling produced frazil ice crystals up to 2 cm in diameter with concentrations up to 4 5 g l 1 at 0 5 m depth considerable temporal variability with time scales of 1 min was documented a close to constant portion of the smaller frazil crystals remained in suspension after some hours the larger crystals which made up most of the ice volume accumulated as slush at the surface current measurements were used to calculate the turbulent dissipation rate and estimates of vertical diffusion were derived after 5 8 hours sediment concentrations in the surface slush were normally close to those of the water after 24 hours however they were 2 4 times higher data indicate that sediment entrainment depends on high heat fluxes and correspondingly high frazil ice production rates as well as sufficiently strong turbulence waves do not seem to increase sediment entrainment significantly

a key source area and constraints on entrainment for basin scale sediment transport by arctic sea ice combining field measurements remote sensing and numerical modelling a key site for ice entrainment and basinwide dispersal of sediments by sea ice has been identified near the new siberian islands the total ice bound sediment export of 18 5 x 10 6 t for an entrainment event documented in 1994 95 is of the same order of magnitude as annual sediment supply to the deep sea sector of the eurasian arctic and the greenland sea satellite imagery and ancillary data indicate that ice advection from this source may play an important role in sedimentation downstream in the transpolar drift

towards quantitative environmental reconstructions from ancient non analogue microfossil assemblages ecological preferences of paleocene eocene dinoflagellates abstract we explore a novel approach towards quantification of paleo ecological signals from non analogue microfossil assemblages by quantifying relations between assemblages and high quality geochemical and sedimentological data from sedimentary archives we test this approach using one group of microfossils the organic cysts of dinoflagellates dinocysts which are widely used in shelf and open marine settings for biostratigraphy and reconstructions of past environments and environmental change similar to other microfossil groups dinocysts can be used to reconstruct environments with relatively high confidence for recent time periods as species affinities can be derived from observational and instrumental data in the absence of such data the ecology of extinct species is much less certain and as a result reconstructions in deep time are often limited to qualitative interpretations to explore if quantitative empirical relations between extinct dinocysts and high quality geochemical data can be established we study a major event of climate change the paleocene eocene thermal maximum petm 56 ma ago the petm is a particularly suitable period for this exercise as there is a multitude of large environmental perturbations associated with the transient global warming such as deoxygenation sea level rise and an accelerated hydrological cycle the synthesized published dataset exhibits better spatial and temporal coverage compared to any other period in deep time we extract empirical relations for the abundance of previously proposed paleoecological groups as a function of independent environmental proxies for example sea surface temperature and terrestrial organic matter input the results unequivocally illustrate that many dinocysts show relations to several of the reconstructed environmental variables notably we show that one genus apectodinium and an ecogroup epicystal goniodomidae required sea surface temperatures in excess of 20 c and 25 c respectively while one species florentinia reichartii was only abundant between 30 and 35 c other groups apparently favored either a limited spiniferites or high senegalinium terrestrial input to the study site relating to salinity nutrient levels or suspended sediment load i e murkiness crucially our work shows that the validation and quantification of ecological signals by independent environmental proxy data provides the opportunity to extract more quantitative information from a wide range of non analogue microfossil assemblages while this approach is not limited to any specific group of microfossils or macrofossils we stress that proper calibration datasets high quality sedimentological and geochemical proxy records are needed and should ideally have decent geographical coverage and include one or more environmental perturbations using this approach such empirical relations can be established for a wide range of microfossil groups that have highly complementary geological records which increases the value of existing data and ensures future application of microfossil based paleoecology

the production of ice and dense shelf water in the okhotsk sea polynyas this paper examines the ice and dense water production in the okhotsk sea coastal polynyas for the 1990 1995 winters the dominant polynyas occur on the northwest and northern shelves and in shelikhov bay we use an algorithm developed for the special sensor microwave imager ssm i to derive for each polynya the area and composition of thin ice and open water and a heat flux algorithm to derive the ice and brine production historic oceanographic observations show that the northwest shelf is the only north pacific region where the 26 8 potential density surface outcrops to the surface and is also that part of the okhotsk shelf where the densest water is observed to occur in support of these observations we find that the northwest shelf polynya is the dominant ice and brine producer contributing on average about 55 of the total production shelikhov bay is the second largest producer with about 25 of the total this region has been previously neglected by both oceanographic and remote sensing studies using a combination of two dense water production models we find that the 6 year average dense water production lies between 0 2 0 4 sv the ice and brine production for the dominant northwest shelf vary interannually by a factor of 3 while the production from all the northern polynyas varies by factor of 2 the source of the variability for the northwest shelf comes from the fact that the southwest to northeast trend of the coastline and the mean winter geostrophic wind velocities are roughly parallel which means that small variations in the wind direction yield large changes in the ice production

eustatic variations during the paleocene eocene greenhouse world we reconstruct eustatic variations during the latest paleocene and earliest eocene 58 52 ma dinoflagellate cysts grain size fractions and organic biomarkers in marine sections at four sites from three continents indicate an increased distance to the coast during the paleocene eocene thermal maximum petm the same trend is recognized in published records from other sites around the world together the data indicate a eustatic rise during the petm beginning 20 to 200 ka before the globally recorded negative carbon isotope excursion cie at 55 5 ma although correlations are tentative we recognize other global transgressions during chrons c25n and c24n the latter may be associated with eocene thermal maximum 2 53 5 ma or the x event 52 ma these results suggest a link between global sea level and hyperthermal intervals potentially because of the melting of small alpine ice sheets on antarctica thermal expansion of seawater or both however the early onset of sea level rise relative to the cie of the petm suggests contributions from other mechanisms perhaps decreasing ocean basin volume on sea level rise copyright 2008 by the american geophysical union

sediment transport by sea ice in the chukchi and beaufort seas increasing importance due to changing ice conditions abstract sediment laden sea ice is widespread over the shallow wide siberian arctic shelves with off shelf export from the laptev and east siberian seas contributing substantially to the arctic ocean s sediment budget by contrast the north american shelves owing to their narrow width and greater water depths have not been deemed as important for basin wide sediment transport by sea ice observations over the chukchi and beaufort shelves in 2001 02 revealed the widespread occurrence of sediment laden ice over an area of more than 100 000 km2 between 68 and 74 n and 155 and 170 w ice stratigraphic studies indicate that sediment inclusions were associated with entrainment of frazil ice into deformed multiple layers of rafted nilas indicative of a flaw lead environment adjacent to the landfast ice of the chukchi and beaufort seas this is corroborated by buoy trajectories and satellite imagery indicating entrainment in a coastal polynya in the eastern chukchi sea in february of 2002 as well as formation of sediment laden ice along the beaufort sea coast as far eastward as the mackenzie shelf moored upward looking sonar on the mackenzie shelf provides further insight into the ice growth and deformation regime governing sediment entrainment analysis of radarsat synthetic aperture sar imagery in conjunction with bathymetric data help constrain the water depth of sediment resuspension and subsequent ice entrainment 20 m for the chukchi sea sediment loads averaged at 128 t km 2 with sediment occurring in layers of roughly 0 5 m thickness mostly in the lower ice layers the total amount of sediment transported by sea ice mostly out of the narrow zone between the landfast ice edge and waters too deep for resuspension and entrainment is at minimum 4 106 t in the sampling area and is estimated at 5 8 106 t over the entire chukchi and beaufort shelves in 2001 02 representing a significant term in the sediment budget of the western arctic ocean recent changes in the chukchi and beaufort sea ice regimes reduced summer minimum ice extent ice thinning reduction in multi year ice extent altered drift paths and mid winter landfast ice break out events have likely resulted in an increase of sediment laden ice in the area apart from contributing substantially to along and across shelf particulate flow an increase in the amount of dirty ice significantly impacts sub ice algal production and may enhance the dispersal of pollutants

stratigraphic and spatial distribution of palynomorphs in deep water turbidites a meta data study from the uk central north sea paleogene abstract the paleogene sele formation spans across the basinal areas of the uk central north sea and comprises a very laterally extensive deep marine fan system namely the forties sandstone member a very important oil and gas reservoir horizon the development of this turbidite system across the basin floor resulted from the response to sea level changes and fluctuating sediment yield from the continental landmass influenced by hinterland uplift and climate in order to understand the distribution of terrestrially sourced and marine palynomorphs in this depositional system comprising stacked turbidite flows statistical analyses of palynology data from 41 wells have been conducted these statistical studies support the division of the microplankton into nine groups clustering taxa depending on their ecology and taphonomy it is observed that the palynological assemblages are influenced by sediment provenance across the turbidite fans the landmass vegetation ecology and the marine microplankton populations varying across the basin the dominant derived cluster groups b peridinioids dominated by apectodinium species and e probably autotrophic gonyaulacoids comprise about 70 of the taxa recorded these dinoflagellates bloomed as a result of low salinity surface waters and an increase in water mass eutrophication resulting from the greenhouse climate optimal conditions of the petm the pollen and spore data although challenging to interpret due to the varied quality of the data set supports the interplay of a coastal wetland vegetation on extensive marginal delta systems with associated wetland and swamp environments

the use of cyclic stratigraphic pattern of peridinioid and gonyaulacoid dinoflagellate cysts in differentiating potential thick monotonous carbonate reservoirs a possible ecostratigraphic tool under test abstract the current work used the conventional peridinioid gonyaulacoid ratio p g to devise a new concept of dinoflagellate cyst zonation called the dinoflagellate ecological zone dez which is based here on the peridinioid ecological zone pez and gonyaulacoid ecological zone gez the pez and gez were used successfully to further divide the thick monotonous carbonate succession mid cenomanian to campanian in q 72 1x well in the eastern desert of egypt into smaller ecozones pez and gez are practical and easy to use in subdividing large conventional biozones of the carbonate reservoirs into distinguishable smaller ecozones when a finer resolution is necessary on a reservoir scale for production demands this tool is suggested to be used in the hydrocarbon exploration industry with minimum knowledge of the taxonomy of the dinoflagellate cysts the proposed pez and gez are related to local ecological conditions within the basin hydrocarbon field i e can be traced out laterally in an intra basinal scale this tool can be applied to any carbonate reservoirs in any petroliferous basin worldwide moreover the p g ratio the relative abundances of the dinoflagellate cyst assemblages and other palynological parameters were used successfully to reveal the palaeodepositional settings of the identified pez and gez alternating transgressive and regressive phases were identified although a dissimilar species composition is observed in each of these ecozones environments were interchanging between the regressive marginal marine to proximal inner neritic and the transgressive distal inner to middle shelf settings three peridiniacean dinoflagellate cyst peaks were recorded the middle cenomanian subtilisphaera peak the middle coniacian isabelidinium chatangiella and manumiella peak and the middle santonian isabelidinium peak

observations of frazil ice formation and upward sediment transport in the sea of okhotsk a possible mechanism of iron supply to sea ice in the sea of okhotsk sediment incorporation transport and release by sea ice potentially plays important roles in the bio related material such as iron cycle and ecosystem the backscatter strength data of bottom mounted acoustic doppler current profilers have suggested signals of frazil ice down to 30 m depth and signals of upward sediment transport throughout the water column simultaneously in the region northeast of sakhalin with a water depth of 100 m such events occurred under turbulent conditions with strong winds of 10 20 m s 1 during such events newly formed ice was present near the observational sites shown by satellite microwave imagery sediment dispersion from the bottom occurred in association with strong currents of 1 0 1 5 m s 1 during these events the mixed layer reaches near the bottom due to wind induced stirring inferred from the high frequency component of vertical velocity thus the winter time turbulent mixing brings re suspended sediment up to near the ocean surface this study provides the first observational evidence of a series of processes on the incorporation of sedimentary materials into sea ice sedimentary particles are dispersed by the strong bottom current subsequently brought up to near the surface by winter time mixing and finally incorporated into sea ice through underwater interaction with frazil ice and or flooding of sea ice floes this wintertime incorporation of bottom sediment into sea ice is a possible mechanism of iron supply to sea ice which melts in spring and releases bio reactive iron into the ocean

dinoflagellate cysts from the upper campanian upper cretaceous of hornby island british columbia canada with implications for nanaimo group biostratigraphy and paleoenvironmental reconstructions abstract thirty mudstone samples from coastal exposures of the northumberland formation on hornby island british columbia canada yielded diverse dinoflagellate cyst and terrestrial sporomorph assemblages a late campanian age for the formation has been well defined through magnetostratigraphy macrofossil biostratigraphy and geochemical studies of the hornby island section dinoflagellate cyst taxa corresponding to 61 genera are exceptionally well preserved and include specimens referable to at least 68 formally established species the earliest occurrences of canninginopsis maastrichtiensis druggidium cf discretum phanerodinium belgicum renidinium cf vitilaire senegalinium simplex spiniferella cornuta and xenicodinium delicatum sensu slimani et al are reported along with the most recent occurrence of senoniasphaera protrusa extending their stratigraphic ranges into the upper campanian the palynomorph assemblages support a late campanian age two dinoflagellate cyst ecozones are recognized ecozone 1 and ecozone 2 assemblages suggest sediment deposition in an inner shelf environment with moderate to high nutrient input and primary productivity

palaeocene biostratigraphy and sequence stratigraphy of the uk central north sea abstract the palaeocene of the central north sea can be divided into four stratigraphic sequences named the ekofisk maureen lista and forties these sequences display consistent and predictable patterns on electric log data and are bounded by high gamma log peaks which represent thin condensed mudstones five additional subsequences are recognized within the lista sequence biostratigraphic analysis has enabled the palaeocene to be divided into six dinocyst zones and 11 subzones based on last occurrence or last abundance events that are considered to have chronostratigraphic significance across the north sea basin the dinocyst zonation has been integrated with bioevents based on other microfossil groups and correlated with onshore nw european sections permitting calibration with the standard worldwide nannoplankton and planktonic foraminiferal zones these bioevents display a consistent relationship with the stratigraphic sequences allowing the construction of a confident stratigraphic framework for the palaeocene

transport and modification processes of dense shelf water revealed by long term moorings off sakhalin in the sea of okhotsk 1 the region off the east coast of sakhalin is thought of as an important pathway of dense shelf water dsw from its production region in the northwestern okhotsk sea to the southern okhotsk sea from july 1998 to june 2000 the first long term mooring experiment was carried out in this region to observe the southward flowing east sakhalin current esc and dsw moored and associated hydrographic data show considerable modification of cold dense water via mixing with warm offshore water in the slope region off northern sakhalin significant onshore eddy heat flux was observed at the northernmost mooring 54 9 n which suggests the occurrence of baroclinic instability the eddy heat flux was not significant farther south at moorings along 53 n cold anticyclonic eddies were identified that were consistent with isolated eddies seen in the hydrographic data the three years of hydrographic data also showed large differences in extent and properties of dsw furthermore the mooring data show that seasonal variability of dsw was quite different in the two years the average dsw transport for 26 7 evaluated using the moored data at 53 n for 1 year 1998 1999 was 0 21 sv 106 m3 s 1 this value is at the lower end of the previous indirect estimates along with the dsw modification this transport estimate indicates that dsw was not only carried southward by the esc but was spread offshore by eddies off northern sakhalin

sequence development during uplift palaeogene stratigraphy and relative sea level history of the outer moray firth uk north sea abstract published models of sequence stratigraphy have been derived from studies of the depositional history of subsiding basins during the palaeogene sediment accumulation in the outer moray firth basin of the north sea coincided with episodes of basin uplift palaeogene trends in coastal onlap and relative sea level in this basin have been estimated directly from seismic data and reveal two long duration cycles of relative sea level fall and rise the first cycle comprising over 800 m fall followed by 500 m rise was initiated in the earliest palaeocene and lasted approximately 9 my the second cycle began in the early eocene and resulted in approximately 70 m fall and 150 m rise in relative sea level over 13 my the duration of both of these cycles can be defined as second order superimposed on both of these long term second order cycles are higher frequency variations in relative sea level with periodicities of around 1 5 my and amplitudes of up to 150 m these shorter cycles are associated with the deposition of sequences identified on the seismic data one of the effects of this superimposition was to either subdue or enhance the development of systems tracts within the sequences enhancement took place where the sea level trends were similar on both the long and the short duration curves e g both rising systems tracts were subdued where sea level trends were opposed in general lowstands and transgressive systems tracts showed significant enhancement within a sequence when the sequence coincided with the steeply falling and steeply rising portions respectively of the long duration relative sea level cycle groups of these skewed sequences are stacked in certain distinct patterns termed sequence sets the pattern type is again dependent on the coincidence of the group of sequences with the second order cycle in general downstepping sequence sets are associated with the steeply falling part of the second order cycle progradational sequence sets with the gently falling to gently rising portion and retrogradational sequence sets with the steeply rising portion these stacking patterns reflect large scale changes in accommodation volume the multi sequence depositional record of a tectonically driven long duration cycle of relative sea level can be considered as a composite sequence where its systems tracts are composed of sequence sets

sediments in arctic sea ice implications for entrainment transport and release despite the arctic sea ice cover s recognized sensitivity to environmental change the role of sediment inclusions in lowering ice albedo and affecting ice ablation is poorly understood sea ice sediment inclusions were studied in the central arctic ocean during the arctic 91 expedition and in the laptev sea east siberian arctic region expedition 1992 results from these investigations are here combined with previous studies performed in major areas of ice ablation and the southern central arctic ocean this study documents the regional distribution and composition of particle laden ice investigates and evaluates processes by which sediment is incorporated into the ice cover and identifies transport paths and probable depositional centers for the released sediment in april 1992 sea ice in the laptev sea was relatively clean the sediment occasionally observed was distributed diffusely over the entire ice column forming turbid ice observations indicate that frazil and anchor ice formation occurring in a large coastal polynya provide a main mechanism for sediment entrainment in the central arctic ocean sediments are concentrated in layers within or at the surface of ice floes due to melting and refreezing processes the surface sediment accumulation in central arctic multi year sea ice exceeds by far the amounts observed in first year ice from the laptev sea in april 1992 sea ice sediments are generally fine grained although coarse sediments and stones up to 5 cm in diameter are observed component analysis indicates that quartz and clay minerals are the main terrigenous sediment particles the biogenous components namely shells of pelecypods and benthic foraminiferal tests point to a shallow benthic marine source area apparently sediment inclusions were resuspended from shelf areas before and incorporated into the sea ice by suspension freezing clay mineralogy of ice rafted sediments provides information on potential source areas a smectite maximum in sea ice sediment samples repeatedly occurred between 81 n and 83 n along the arctic 91 transect indicating a rather stable and narrow smectite rich ice drift stream of the transpolar drift the smectite concentrations are comparable to those found in both laptev sea shelf sediments and anchor ice sediments pointing to this sea as a potential source area for sea ice sediments in the central arctic ocean sea ice clay mineralogy is significantly different from deep sea clay mineral distribution patterns the contribution of sea ice sediments to the deep sea is apparently diluted by sedimentary material provided by other transport mechanisms

environmental dynamics during the paleocene eocene thermal maximum petm in the northeastern peri tethys revealed by high resolution micropalaeontological and geochemical studies of a caucasian key section abstract the sedimentary record of the paleocene eocene thermal maximum petm in the wide epeiric sea of the ne peri tethys contains a sapropelitic bed sbd characterized by a specific microfossil assemblage and negative oxygen and carbon isotope excursions cie new results obtained from a high resolution sampling of this interval in the kheu section central caucasus allows us to explore the succession interrelationships and consequences of global and regional palaeoenvironmental events during the petm the cie apparently lasted twice as long as the sbd accumulation period thus the sbd represents a response to the early and most dramatic phase of the petm related to rapid transgression and greatly enhanced eutrophication of the basin the lithological architecture of the sbd represents four bands each of which consists of a dark low calcareous toc rich clay and relatively paler calcareous clays the highest toc concentrations are found in the lower and upper bands of the sbd however the lower band mostly consists of basinal organic matter while the upper band represents mixed basinal and terrestrial organic matter pre petm events include the initial evolution of the rhomboaster nannofossil lineage with the early first appearance of a short arm species relatively reduced calcareous plankton productivity changes in the ratios of dinocyst ecological groups and minor fluctuations in 13c and 18o the onset of the cie corresponds to the base of the sbd which exhibits a dramatic decrease in total nannofossil abundance and an increase in total dinoflagellate abundance the occurrence of excursion taxa of nannofossils rhomboasters asymmetric discoasters and dinocysts axiodinium augustum epelidinium pechoricum and significant variations in the species ratios of both nannoplankton and dinoflagellate communities with widespread dominance of warm water and eutrophic species above the sbd but during the late phase of cie the nannofossil abundance and species composition show a slight recovery but most paleocene taxa become extinct during the cie recovery apectodinium spp significantly decrease in abundance above the sbd but rare specimens of ax augustum persist higher in the section after the end of the cie thus the major extinction of the paleocene nannofossil taxa occurs after the termination of the most critical conditions during the cie recovery phase while the dinocyst excursion taxa survive even later

the apectodinium acme and terrestrial discharge during the paleocene eocene thermal maximum new palynological geochemical and calcareous nannoplankton observations at tawanui new zealand manifestations of profound perturbations in biogeochemical systems during the paleocene eocene thermal maximum petm include a prominent global negative 13c and a pronounced increase in the relative abundance of dinoflagellate cysts dinocysts assigned to the genus apectodinium while motile representatives of apectodinium were most likely thermophilic and heterotrophic the underlying causes of this dinoflagellate response are not well understood here we provide new insight by examining the palynology chemistry and calcareous nannoplankton across the petm in a continental slope section at tawanui new zealand across the petm marked changes in the relative abundance of apectodinium vary antithetically with significant changes in the 13c of carbonate and organic matter in general the high relative abundance of apectodinium relates to enhanced concentrations of dinocysts signifying a bloom of apectodinium in surface waters during the petm changes in apectodinium and 13c records correspond to variations in many other parameters including a smaller negative shift in bulk carbonate 13c than expected increased terrestrial palynomorphs elevated toc and c n ratios lower carbonate contents higher sio2 and al2o3 contents and lower si al ratios all of these variations can be explained by an increase in delivery of terrigenous material to the continental margin a peak in the relative abundance of glaphyrocysta dinocysts at the onset of the petm may indicate greater down slope transport of neritic material changes in calcareous nannoplankton abundances suggest increased nutrient availability in surface waters during the petm the combined results show that apectodinium dominated assemblages global perturbations in carbon isotopes and enhanced terrigenous delivery closely correspond in time at tawanui a sudden and massive carbon injection to the ocean atmosphere system may have enhanced weathering and increased terrigenous inputs to continental margins during the petm we further suggest that these inputs caused the apectodinium acme by elevating primary productivity in marginal seas

paleogene early neogene paleoenvironmental reconstruction based on palynological analysis of odp hole 959a west africa abstract five paleoenvironmental intervals interval 1 interval 5 are established in the late paleogene early neogene of the ocean drilling program odp site 959 hole 959a cote d ivoire ghana transform margin in the eastern equatorial atlantic the intervals are based on dinoflagellate cyst and palynofacies analyses of 30 samples covering a 273 3 m interval we observed an abundance of the filisphaera group filisphaera filifera and bitectatodinium tepikiense which is interpreted as an arctic migration to equatorial regions during a narrow interval in the early oligocene early rupelian in addition we document one hiatus within interval 3 in the early miocene aquitanian the dominance of typically restricted marine species of the polysphaeridium group homotryblium plectilum and polysphaeridium zoharyi at several horizons in the open oceanic sediments of odp hole 959a appear to be very distinctive events upon integrating dinoflagellate cyst data with prior lithologic and microfossil data we interpret these dominance events as being due to offshore transportation by turbidity currents intervals 1 and 2 hiatus event interval 3 or hyperstratification conditions intervals 3 and 4 in addition the dominance of cribroperidinium spp c giuseppei and c tenuitabulatum in the upper part of the section within paleoenvironmental interval 5 is suggestive of cold water masses during a strong upwelling period in the latest early miocene burdigalian the general abundance of amorphous organic matter alongside the dinoflagellate cyst assemblage supports an outer neritic oceanic depositional environment for the studied site the consistent occurrence of degraded phytoclasts in the sediments also suggests fluvial outflows to this offshore site

what drives the southward drift of sea ice in the sea of okhotsk abstract the sea of okhotsk is the southernmost sea ice zone with sizable ice it is widely believed that the prevailing northwesterly wind and the southward east sakhalin current esc are the two main factors that drive the southward drift of sea ice however the relative contributions of these factors have not been understood in this paper by using the current and ice drift data measured with the moored acoustic doppler current profiler a 3 d ocean model simulation objective analysis data of the wind and satellite sea ice data we examine to what degree and how the ice drift is determined by the wind and ocean current from a linear regression of the observed ice drift ocean current and wind the wind forced component of the ice drift was best fitted when sea ice is assumed to move with a speed of 1 6 of the geostrophic wind with a turning angle of 17 6 to the left of the wind such a relationship was adopted as the wind drift component for all sea ice pixels detected from special sensor microwave imager data for the ocean forced component of the ice drift we adopted the current at 20 m depth from a numerical model simulation that reproduces well the esc and its variability we then evaluated the sea ice drift over 46 54 n during 1998 2005 for the southward drift of sea ice the contribution of the wind component is found to be larger than the oceanic component although the ocean contribution becomes larger typically comparable to the wind contribution near the coast and in the northern region where the esc is stronger we estimated the average annual cumulative southward ice transport to be 3 0 0 9 10 11 m 3 at 53 n this ice transport is comparable to the annual discharge of the amur river the ratio of wind to oceanic components in the transport is estimated to be 1 2 1 8 we also conducted ice drift simulations based on the modeled current velocity and the assumed wind drift of 1 5 geostrophic wind with a turning angle of 15 to the left the simulations reproduce well the ice drift north of 47 n but not south of 47 n likely due to the poor representation of the current system at the latter underevaluation of the wind factor near the ice edges and the neglect of ice formation and melt

paleoclimatic and paleoenvironmental records of the oligocene miocene transition central jylland denmark a multidisciplinary study of the oligocene miocene o m transition was carried in two boreholes harre 1 and horn 1 from the danish land area in order to improve the understanding of the paleodimatological and environmental changes across the mi 1 the earliest miocene cooling event dinoflagellate cyst dinocyst biostratigraphy supported by re evaluation of the foraminiferid biostratigraphy a new set of magnetic data and stable carbon isotope delta c 13 records were applied to improve the age model for the studied succession as well as the positioning of the o m boundary these data further enabled a correlation of the two investigated profiles with the well established stratigraphical framework for the danish area the bit index an organic proxy indicating the relative input of soil derived organic matter dinocyst assemblages and palynofacies have been applied for establishing the paleoenvironmental changes across the oligocene miocene o m boundary our data indicate a shallowing upward trend in the latest oligocene resulting in the establishment of a very restricted marine setting in the earliest miocene our study confirms that the o m boundary is located at a sequence boundary the local sequence boundary b sb b and corresponds to an increase in terrestrial organic matter input a mean air temperature record based on the mbt cbt proxy reveals an similar to 2 degrees c drop in temperature at the o m and the sequence boundary our findings confirm previous suggestions that this sequence boundary is a result of the glacio eustatic sea level fall related with the mi 1 cooling event the unconformity at the sequence boundary probably correlates with the coldest part of mi 1 and thus no deposits from this period have been preserved this suggests that the temperature drop might have been greater than 2 degrees c

arctic late paleocene early eocene paleoenvironments with special emphasis on the paleocene eocene thermal maximum lomonosov ridge integrated ocean drilling program expedition 302 we reconstruct the latest paleocene and early eocene 57 50 ma environmental trends in the arctic ocean and focus on the paleocene eocene thermal maximum petm 55 ma using strata recovered from the lomonosov ridge by the integrated ocean drilling program expedition 302 the lomonosov ridge was still partially subaerial during the latest paleocene and earliest eocene and gradually subsided during the early eocene organic dinoflagellate cyst dinocyst assemblages point to brackish and productive surface waters throughout the latest paleocene and early eocene dinocyst assemblages are cosmopolitan during this time interval suggesting warm conditions which is corroborated by tex86 reconstructed temperatures of 15 18 c inorganic geochemistry generally reflects reducing conditions within the sediment and euxinic conditions during the upper lower eocene spectral analysis reveals that the cyclicity recorded in x ray fluorescence scanning fe data from close to eocene thermal maximum 2 53 ma presence confirmed by dinocyst stratigraphy is related to precession within the lower part of the petm proxy records indicate enhanced weathering runoff anoxia and productivity along with sea level rise on the basis of total organic carbon content and variations in sediment accumulation rates excess organic carbon burial in the arctic ocean appears to have contributed significantly to the sequestration of injected carbon during the petm

geochemistry of surficial and ice rafted sediments from the laptev sea siberia the laptev sea as a part of the world s widest continental shelves surrounding the arctic ocean is a key area for understanding the land ocean interaction in high latitude regions with a yearly freshwater input of 511 km3 the lena river one of the eight major world rivers has an influencing control over the environment of this arctic marginal sea which is ice covered during most of the year in this paper the first measurements are presented of the major and trace element distribution within the 20 m grain size fraction of surficial sediments and of particulate matter in new and young ice from the laptev sea siberian arctic the concentration and distribution of major and trace elements have been determined in 51 surficial sediment samples covering the whole laptev sea shelf south of the 50 m isobath thirty one samples of particulate matter in newly formed ice were taken during the freeze up period in 1995 median concentration levels of heavy metals in surficial sediments ni 46 g g 1 cu 26 g g 1 zn 111 g g 1 and pb 21 g g 1 are within the concentration range of marine unpolluted sediments also the sediment laden ice showed no indication of anthropogenic perturbation of the trace metal inventory spatial distribution patterns of heavy metals are mainly determined by variation of mineral composition and different fluvial sediment sources in the eastern and western laptev sea the laptev sea shelf is cut by five north south trending submarine valleys enrichment of manganese in the oxic surficial sediment layer within these valleys and the occurrence of small ferromanganese nodules are caused by a high input of dissolved and particulate mn from the lena river and a strong diagenetic cycling of mn on the laptev sea shelf evidence is given that the content of as in surficial sediments is also strongly affected by diagenetic cycling this causes surficial sediment as concentrations of more than 100 g g 1 enrichment of mn and as was mainly observed in the submarine valleys distant from the major river mouth the sediment dilution due to higher sedimentation rates near the river outlets and a strong sediment re working by ice gouging in the shallow areas are the principle causes for the absence of diagenetic accumulation in this region during the formation of new ice scavenging of riverine suspended matter and resuspension of sediments followed by an incorporation of particles into the ice are important processes for the river shelf ocean transport of particulate trace elements it could be shown that particle loaded ice posseses the same geochemical signatures as the suspended matter and surficial seafloor sediments in the area of ice origin this has also strong implications for the contaminant transport on the arctic shelves and allows to use the geochemical signature of sea ice for the reconstruction of ice drift pattern within the arctic ocean

tropical ocean decadal variability and resonance of planetary wave basin modes part ii numerical study abstract oceanic response to stochastic wind forcing is studied in a tropical extratropical basin using two shallow water models a periodically forced model and a time forward model consistent with theory extratropical stochastic wind forces a decadal spectral peak in the tropical and eastern boundary ocean as a resonant response of the planetary wave basin mode this resonant response is characterized by a rather uniform amplitude and phase in the equatorial and eastern boundary region in comparison away from the eastern boundary the extratropical ocean is affected significantly by the local ekman pumping forcing with spectral peaks varying with location a complex eof ceof analysis of the time forward model simulation further suggests that these resonant responses are robust and can be extracted as the leading ceof modes thus the resonance of the planetary wave basin mode gives a physically based guideline for the interpretation of decadal oceanic variability in the tropical extratropical ocean

timing cause and impact of the late eocene stepwise sea retreat from the tarim basin west china abstract a vast shallow epicontinental sea extended across eurasia and was well connected to the western tethys before it retreated westward and became isolated as the paratethys sea however the palaeogeography and the timing of this westward retreat are too poorly constrained to determine potential wider environmental impacts let alone understanding underlying mechanisms of the retreat such as global eustasy and tectonism associated with the indo asia collision here an improved chronostratigraphic and palaeogeographic framework is provided for the onset of the proto paratethys sea retreat at its easternmost extent in the tarim basin in western china is provided five different third order sea level cycles can be recognised from the cretaceous palaeogene sedimentary record in the tarim basin of which the last two stepped successively westwards as the sea retreated after the maximum third incursion new biostratigraphic data from the fourth and fifth incursions at the westernmost margin of the tarim basin are compared to our recent integrated bio magneto stratigraphic results on the fourth incursion near the palaeodepocentre in the south western part of the basin while the fourth incursion extended throughout the basin and retreated at 41 ma base c18r the last and fifth incursion is restricted to the westernmost margin and its marine deposits are assigned a latest bartonian early priabonian age from 38 0 to 36 7 ma near top c17n 2n to base c16n 2n similar to the fourth the fossil assemblages of the fifth incursion are indicative of shallow marine near shore conditions and their widespread distribution across eurasia suggests that the marine connection to the western tethys was maintained the lack of diachronicity of the fourth incursion between the studied sections across the southwest tarim basin suggests that the sea entered and withdrew relatively rapidly as can be expected in the case of eustatic control on a shallow epicontinental basin however the westward palaeogeographic step between the fourth and fifth incursions separated by several millions of years rather suggests the combined long term effect of tectonism possibly associated with early uplift of the pamir kunlun shan thrust belt the fourth and fifth regressions are time equivalent with significant aridification steps recorded in the asian interior thus supporting climate modelling results showing that the stepwise sea retreat from central asia amplified the aridification of the asian interior

quantitative evaluation of iron transport processes in the sea of okhotsk abstract comprehensive observations of the iron fe distribution in the western sea of okhotsk were conducted and revealed the existence of two fe transport processes in the sub polar marginal sea one transport process is fe loading from the amur river and transport by the east sakhalin current esc and the other is fe transport by the intermediate water part of which was reported by nishioka et al 2007 here we report on quantitative evaluations of these two fe transport processes the surface dissolved fe diss fe and low salinity water distribution clearly indicate the influence of fe discharge from the amur river and the fe that is transported by the east sakhalin current the amounts of total dissolvable fe td fe and diss fe that cross the surface of the northeast sakhalin coastal area are estimated at 9 0 108 1 3 109 g yr 1 and 1 0 108 1 5 108 g yr 1 respectively although the esc surface transport system along the sakhalin coast is effective the length scale estimation of td fe transport indicated that only 1 5 of the fe at the mouth of the amur river reached 52 n which may be due to scavenging by biological particulates high fe anomalies were observed at the bottom of the continental shelf and the shelf break along the sakhalin coast the extremely low temperature and low n water indicate that fe resuspension due to the reducing properties of sediment occurred on the shelf and that the fe was introduced to dense shelf water dsw by tidal mixing we estimate that the amounts of td fe and diss fe involved in the dsw on the continental shelf are 8 8 1010 2 5 1011 g yr 1 and 2 3 109 6 6 109 g yr 1 respectively length scale estimates of td fe transport indicate that 20 of the td fe on the continental shelf remained in the kuril basin thus the td fe in the intermediate water was efficiently transported to the kuril basin these results indicate that two orders of magnitude more fe is derived from the continental shelf by the intermediate water than by surface water and that fe is transported a greater distance by intermediate water than by the surface layer additionally the fe that reached the kuril straits was mixed by intensive tidal mixing and influenced the vertical profiles of the water columns on both sides of the kuril straits in the kuril basin and the oyashio region our quantitative evaluation also indicates other fe inputs around the kuril strait

bartonian to priabonian dinoflagellate cyst biostratigraphy and paleoenvironments of the m karcha section in the southern tethys margin rif chain northern morocco abstract palynological analyses were performed on the eocene sediments of the m karcha section which is located in the taza region structural tsoul unit eastern external rif northeastern morocco the palynological content of this section is composed essentially of well preserved and diverse dinoflagellate cyst assemblages allowing detailed taxonomic determinations age assignments biostratigraphic correlations and paleoenvironmental interpretations other palynomorphs such as spores pollen grains and foraminiferal linings are rare and therefore not taxonomically determined up to the genus level 131 dinoflagellate cyst species were identified age assignments are based on dinocyst bioevents considered previously as potential biostratigraphic markers of the bartonian and priabonian including the lowest occurrences los of glaphyrocysta semitecta impagidinium dispertitum rhombodinium perforatum cooksonidium capricornum stoveracysta ornata stoveracysta sp 2 of brinkhuis and biffi 1993 and lo and highest occurrence ho of schematophora speciosa the quantitative palynological analyses based mainly on dinoflagellate cysts through the m karcha section revealed an inner neritic generally lagoon environment with a low productivity alternated with short episodes of the open marine influence

structure and seasonal variability of the east sakhalin current abstract in order to clarify the structure and seasonal variability of the flow field near the western boundary of the sea of okhotsk long term mooring measurements were carried out from 1998 to 2000 in this region in most of the mooring period a persistent southward flow the east sakhalin current was observed which extends from the surface to a depth around 1000 m the speed of this southward flow clearly changed seasonally the peak monthly mean speed along 53 n at a depth of 200 m attained a maximum of 37 9 cm s 1 in january and a minimum of 10 8 cm s 1 in july three different cores of intense flow were identified in the southward flow the first core was centered over the continental slope and had rather large vertical extent reaching the bottom on the slope the second core was trapped over the shelf near the surface and was observed from october to november this core was associated with less saline surface water affected by the amur river discharge the third core was intensified toward

observations of supercooling and frazil ice formation in the laptev sea coastal polynya this paper examines a hydrographic response to the wind driven coastal polynya activity over the southeastern laptev sea shelf for april may 2008 using a combination of environmental satellite envisat advanced synthetic aperture radar asar and terrasar x satellite imagery aerial photography meteorological data and sbe 37 salinity temperature depth and acoustic doppler current profiler land fast ice edgemoored instruments when asar observed the strongest end of april polynya event with frazil ice formation the moored instruments showed maximal acoustical scattering within the surface mixed layer and the seawater temperatures were either at or 0 02 c below freezing we also find evidence of the persistent orizontal temperature and salinity gradients across the fast ice edge to have the signature of geostrophic flow adjustment as predicted by polynya models

thickness and production of sea ice in the okhotsk sea coastal polynyas from amsr e 1 from comparisons with thickness of sea ice from advanced very high resolution radiometer avhrr and ice profiling sonar data we have developed an advanced microwave scanning radiometer eos amsr e thin ice thickness algorithm for the sea of okhotsk this algorithm can estimate ice thickness of 0 2 m without snow using the polarization ratio of amsr e brightness temperature at a 36 5 ghz channel from a linear relationship with avhrr ice thickness when a snow cover exists on the thin ice surface as occurred a few times in each winter it is shown that the algorithm cannot detect the thin ice sea ice and dense shelf water dsw production in coastal polynya are estimated on the basis of heat flux calculation with the daily amsr e ice thickness for three winters december march of 2002 2003 to 2004 2005 the ice production is largest in the northwest shelf nws polynya which accounts for 45 of the sum of ice production in major coastal polynyas the ice production in major coastal polynyas would cover the maximum ice area of the okhotsk sea if the average ice thickness is assumed to be 1 m variability of the ice production is mainly modulated by air temperature in the nws polynya which is the main dsw production area the annual dsw formation rate is estimated to be 0 36 sv

a high resolution north sea eocene dinocyst zonation abundant dinoflagellate cysts dinocysts from eocene strata of the north sea exhibit a consistent succession of events based on the analysis of 120 wells from quadrant 3 in the north to quadrants 21 and 22 in the south these events have a constant relationship with stratigraphic sequences and subsequences throughout the area eight eocene dinocyst zones and 23 subzones and the uppermost palaeocene apectodinium augustum biozone are defined by last occurrence or abundance events the north sea dinocyst succession is similar to that in denmark northwest germany belgium the netherlands and southern england permitting correlation with calcareous nannoplankton zones for sections in these areas and hence allowing correlation of north sea stratigraphy with northwest european and worldwide events

eocene to oligocene dinoflagellate cysts from the tattofte section western external rif northwestern morocco biostratigraphy paleoenvironments and paleoclimate abstract the palynological analysis of the eocene oligocene succession from the tattofte section in the western external rif northwestern morocco reveals the presence of well preserved and diverse assemblage rich in dinoflagellate cysts dinocysts qualitative analyses especially of the dinocysts differentiate the individual stages of the deposits while quantitative analyses permit paleoenvironmental and paleoclimatic interpretations we assign the lower part of the tattofte section to the middle eocene lutetian and bartonian and its upper part to the upper oligocene chattian and define a hiatus spanning the late eocene priabonian and early oligocene rupelian the dinocyst marker events used for the biostratigraphic interpretations include the first and last occurrences of marker species such as batiacasphaera compta castellodinium compactum cerebrocysta bartonensis distatodinium biffii distatodinium paradoxum distatodinium ellipticum enneadocysta arcuata homotryblium floripes hystrichokolpoma bullatum impagidinium velorum lentinia serrata pentadinium imaginatum rhombodinium spinula saturnodinium perforatum and ynezidinium brevisulcatum as well as the chiropteridium spp acmes and we equate the chattian with the dinocyst distatodinium biffii zone of brinkhuis et al 1992 changes in the relative abundances of selected dinocyst groups spores and pollen lead to the distinction from oldest to youngest of four marine environments 1 marginal marine to coastal inner neritic under relatively warm water during the middle eocene 2 outer neritic to oceanic during a transgressive regime in the early chattian 3 fluctuating restricted to open marine in the middle chattian and 4 shallow coastal to open marine due to sea level fall at the top of the section in the latest chattian suggested by the chiropteridium spp acmes the acmes of selected thermophilic dinocyst taxa such as polysphaeridium spp and homotryblium spp suggest warm water marine conditions which may be related to the middle eocene climatic optimum meco and late oligocene warming

palaeoecology and palaeoenvironments of the lower palaeogene succession offshore west greenland the microfossil and palynofloral assemblages of the paleocene to middle eocene succession offshore west greenland have been investigated several taxa which are believed to reflect specific palaeoenvironments were selected and their relative abundances measured subsequently an interpretation of the changing depositional settings in the hellefisk 1 ikermiut 1 kang miut 1 nukik 1 and nukik 2 boreholes through the lower palaeogene has been made

oligocene climate changes controlling forced regression in the eastern north sea abstract in this paper we investigate the early oligocene rupelian high angle clinoform complex from the western part of the norwegian danish basin the study consists of an integrated analysis of 3d seismics petrophysical well logs and micropaleontological data a series of erosional features and geometry of prograding units e g the high angle clinoform complex interpreted as a forced regressive unit is identified the proposed depositional model accounts for lithological variations climate induced sea level fluctuation and depositional environment the characteristic high angle clinoform complex has been estimated to be of late rupelian age paleoenvironmental reconstruction of the unit based on dinocyst analysis suggests that the deposition of the succession took place in submarine conditions presence of a cold water dinoflagellate svalbardella within the unit containing high angle clinoforms suggests that the unit was deposited during one of the oligocene glacial maxima the most probably the oi2 cooling event

creation of a heat and salt flux dataset associated with sea ice production and melting in the sea of okhotsk abstractsea ice formation its transport and its melting cause the redistribution of heat and salt which plays an important role in the climate and biogeochemical systems in the sea of okhotsk a heat and salt flux dataset is created in which such sea ice processes are included with a spatial resolution of 12 5 km the dataset is based on a heat budget analysis using ice concentration thickness and drift speed from satellite observations and the ecmwf interim re analysis era interim data the salt flux calculation considers both salt supplied to the ocean from sea ice production and freshwater supplied when the ice melts this dataset will be useful for the validation and boundary conditions of modeling studies the spatial distribution of the annual fluxes shows a distinct contrast between north and south significant ocean cooling with salt supply is shown in the northern coastal polynya region while ocean heating with freshwater supply is shown in the south this contrast suggests a transport

iron and macro nutrient concentrations in sea ice and their impact on the nutritional status of surface waters in the southern okhotsk sea abstract to elucidate the roles of sea ice in biogeochemical cycles in the sea of okhotsk the concentrations of macro nutrients no3 no2 po4 sio2 and nh4 and trace elements fe al were measured in samples of sea ice overlying snow and seawater the oxygen isotope ratio 18o in the sea ice was used to distinguish between snow ice and seawater origin ice except for nh4 the macro nutrient concentrations were lower in sea ice than in surface water in the ice covered area a linear relationship between salinity and concentrations of no3 no2 po4 and sio2 in the sea ice indicated that these macro nutrients originated mainly from seawater the fe concentrations in sea ice were variable and several orders of magnitude higher than those in surface water in the ice covered area the fe concentrations in the sea ice were positively correlated with al concentrations the suggestion being that the fe contained in the sea ice originated mainly from lithogenic mineral particles the annual fe flux into the surface water from sea ice melting in the southern sea of okhotsk was estimated to be 740 mol fe m 2 yr 1 this flux is comparable to the reported annual atmospheric fe flux 267 929 mol fe m 2 yr 1 in the western north pacific in spring sea ice melting may slightly dilute macro nutrient concentrations but increase fe concentrations in surface water these results suggest that sea ice may contribute to phytoplankton growth by release of fe into the water column and have a large impact on biogeochemical cycles in the sea of okhotsk

a model for entrainment of sediment into sea ice by aggregation between frazil ice crystals and sediment grains avertical numerical model has been developed that simulates tank experiments of sediment entrainment into sea ice physical processes considered were turbulent vertical diffusion of heat salt sediment frazil ice and their aggregates differential growth of frazil ice crystals secondary nucleation of crystals and aggregation between sediment and ice the model approximated the real size distribution of frazil ice and sediment using five classes of each frazil crystals 25 m to 1 5 cm were modelled as discs with a constant thickness of their diameter each class had a constant rise velocity based on the density of ice and drag forces sediment grains 1 600 m were modelled as constant density spheres with corresponding sinking velocities the vertical diffusion was set constant for experiments based on calculated turbulent rms velocities and dissipation rates from current data the balance between the rise sinking velocities and the constant vertical diffusion is an important feature of the model the efficiency of the modeled entrainment process was estimated through a an aggregation factor values for a are in the range but average values are often close to 0 01 entrainment increases with increasing sediment concentration and turbulence of the water and heat flux to the air

intensive mixing along an island chain controls oceanic biogeochemical cycles 1 the subarctic pacific is a high nutrient low chlorophyll hnlc region in which phytoplankton growth is broadly limited by iron fe availability however even with fe limitation the western subarctic pacific wsp has significant phytoplankton growth and greater seasonal variability in lower trophic levels than the eastern subarctic pacific therefore differences in fe supply must explain the west to east decrease in seasonal phytoplankton growth the fe flux to the euphotic zone in the wsp occurs at a moderate value in that it is significantly higher than its value on the eastern side yet it is not sufficient enough to cause widespread macronutrient depletion that is hnlc status is maintained although we recognize several fe supply processes in the wsp the mechanisms that account for this moderate value of fe supply have not previously been explained here we demonstrate the pivotal role of tidal mixing in the kuril islands chain kic for determining the moderate value a basin scale meridional fe section shows that fe derived from sediments in the sea of okhotsk is discharged through the kic into the intermediate water masses 800 m of the western north pacific the redistribution of this fe rich intermediate water by intensive mixing as it crosses the kic is the predominant process determining the ratio of micronutrient fe to macronutrients e g nitrate in subsurface waters this ratio can quantitatively explain the differences in surface macronutrient consumption between the western and eastern subarctic as well as the general formation and biogeochemistry of hnlc waters of the subarctic north pacific

numerical model of frazil ice and suspended sediment concentrations and formation of sediment laden ice in the kara sea a one dimensional vertical numerical model of currents mixing frazil ice concentration and suspended sediment concentration has been developed and applied in the shallow southeastern kara sea the objective of the calculations is to determine whether conditions suitable for turbid ice formation can occur during times of rapid cooling and wind and wave induced sediment resuspension although the model uses a simplistic approach to ice particles and neglects ice sediment interactions the results for low stratification shallow 20 m freeze up conditions indicate that the coconcentrations of frazil ice and suspended sediment in the water column are similar to observed concentrations of sediment in turbid ice this suggests that wave induced sediment resuspension is a viable mechanism for turbid ice formation and enrichment mechanisms proposed to explain the high concentrations of sediment in turbid ice relative to sediment concentrations in underlying water may not be necessary in energetic conditions however salinity stratification found near the ob and yenisey rivers damps mixing between ice laden surface water and sediment laden bottom water and probably limits incorporation of resuspended sediment into turbid ice until prolonged or repeated wind events mix away the stratification sensitivity analyses indicate that shallow 20 m unstratified waters with fine bottom sediment settling speeds of 1 mm s 1 or less and long open water fetches 25 km are ideal conditions for resuspension

episodic fire runoff and deposition at the palaeocene eocene boundary qualitative and quantitative coal petrological analyses have been undertaken on the laminated lignite at the base of the cobham lignite bed from scalers hill kent england the maximum negative carbon isotope excursion which marks the beginning of the palaeocene eocene thermal maximum petm occurs near the top of the laminated lignite the lignite contains inertinite a petrographic term used to describe charcoal the laminated lignite has inertinite rich and inertinite poor layers indicative of episodic fires and post fire erosion charcoal clasts are derived from living or recently senesced plants and are dominated by the leaf stalks of herbaceous ferns and wood fragments from flowering plants the charcoal assemblage reflects a low diversity flora possibly adapted to disturbance by fire derived from a source vegetation subjected to seasonal surface wildfires the environmental conditions leading up to and across the onset of the petm are therefore interpreted as incorporating a persistent fire regime with episodic wildfires followed by rainfall and runoff events abundant charcoal indicates near modern oxygen levels whereas the absence of charred peat in this area calls into question previous suggestions that burning of palaeocene peats might have contributed to the short lived negative carbon isotope excursion at the palaeocene eocene boundary

sequence stratigraphic interpretations from palynofacies dinocyst and lithological data of upper eocene lower oligocene strata in southern mississippi and alabama u s gulf coast abstract this paper presents new information on the sequence stratigraphy of the upper eocene lower oligocene strata in southern mississippi and alabama based on palynological and lithological data from five sections by integrating lithological characteristics with palynofacies assemblages several dinocyst paleoecological groups the deflandrea group and the abundance of reworked dinocysts in samples paleobathymetric curves were reconstructed and used to revise the sequence stratigraphy of the area we identified a maximum flooding surface in the middle of the shubuta clay formation in southern mississippi and dated it as latest eocene in southern alabama the eocene oligocene boundary was placed within a condensed section representing about 0 19 ma and it coincided with the shubuta clay vicksburg group contact this condensed section is equivalent to the accumulation of the upper shubuta and red bluff formations in southern mississippi the forest hill mint spring contact which has been interpreted as a sequence boundary that merged with a transgressive surface does not correlate with the tejas a ta 4 3 4 4 sequence boundary of haq et al 1988 the pachuta marl and lower shubuta clay formations are constituents of a late eocene transgressive systems tract in southern mississippi but this systems tract extended to the shubuta clay vicksburg group contact in southern alabama the overlying early oligocene highstand systems tract consisted of the upper shubuta in mississippi and the red bluff bumpnose forest hill formations a thin sandstone in the mint spring was interpreted as a deposit of a possible lowstand systems tract above the sequence boundary in one southern mississippi section in general the mint spring marl and marianna limestone constituted a transgressive systems tract

observations of platelet ice growth and oceanographic conditions during the winter of 2003 in mcmurdo sound antarctica 1 platelet ice is the name given to ice crystals that nucleate in the ocean and grow either at depth or loosely attached to the ice water interface related to the proximity of ice shelves it is known to form in supercooled seawater this study details the conditions for its growth during the austral winter of 2003 in mcmurdo sound antarctica a key finding is that the presence of platelet ice in the sea ice cover is conclusively linked to the time history of the appearance of ice crystals in the water column monitored using the strength of the backscattered signal from an acoustic doppler current profiler as a proxy generally these crystals appeared from mid may as water near the interface became supercooled this near surface supercooling appears to be related to a simultaneous abrupt change in the structure of the upper 250 m of the water column from one that behaved dynamically and contained both the warmest and coolest measured temperatures to one in which the water was essentially isothermal near its surface freezing temperature near surface ocean temperature was also affected by tidal mixing and by an increase in the thickness and density over the course of winter of the surface mixed layer created by salt rejection during ice growth these processes allowed cold water trapped by buoyancy in a band at the base of the mixed layer in early winter to gain access to the ice water interface by midwinter this band of cold water probably had its origin beneath the mcmurdo ice shelf

palynofacies and sea level changes in the middle coniacian late campanian late cretaceous of the east coast basin new zealand abstract a palynofacies analysis of four sections through the paton and herring formations of the east coast basin in southern marlborough indicates that the two formations were deposited on the inner to mid shelf in a marine environment with conspicuous input of plant material from adjacent land area the paton formation was deposited on the inner to mid shelf under oxic conditions and in proximity to a river delta possibly in a deltafront setting its lower part is clearly less marine than its upper part pointing to an overall deepening trend with time the deposition of the herring formation took place farther offshore on the mid shelf in a mud dominated environment under poorly oxygenated conditions at the sediment water interface following a landward shift of shoreline a stratigraphic analysis of changes in palynofacies and lithology through the four sections allows a breakdown of the succession into seven depositional sequences separated by unconformities or their correlative conformities a regional sea level curve for the middle coniacian upper campanian in the east coast basin is proposed on the basis of the inferred sequences and chronostratigraphic control from dinoflagellate biostratigraphy the sea level cycles thus inferred for the east coast basin show a poor correlation with the re scaled haq cycle chart suggesting that regional tectonics rather than eustasi controlled the east coast basin sequences

biostratigraphic evidence for evolving palaeoenvironments in the lower paleogene of the faeroe shetland basin the results of biostratigraphic analysis of the palaeocene to lower eocene section in four faeroe shetland basin wells are presented the succession of bioevents is shown to be the same as that documented for wells in the north sea evolution of microfossil assemblages within the basin reflects the change from an open marine setting in the danian to more restricted marine and non marine conditions in the late thanetian and early ypresian this change is accompanied by a number of microfossil extinctions that form useful regional biomarkers for the faeroe shetland and north sea basins these events include the extinction of planktonic foraminifera close to the danian selandian boundary and the extinction of dinocyst taxa palaeoperidinium pyrophorum and areoligera cf coronata at the selandian thanetian boundary within the thanetian section the extinction of areoligera coincides with an abrupt reduction in numbers and diversity of agglutinated foraminifera the thanetian ypresian boundary is marked by the extinction of apectodinium augustum well 208 19 1 lies in the marine northeastern part of the basin which was connected to the north sea by a narrow seaway however upper thanetian to lower ypresian biofacies become increasingly restricted when traced southwestwards along the basin axis with this interval being non marine in 204 24 1a

observations of vertical currents and convection in the central greenland sea during the winter of 1988 1989 during the winter of 1988 1989 five acoustic doppler current profilers adcps were moored in the central greenland sea to measure vertical currents that might occur in conjunction with deep mixing and convection two adcps were looking up from about 300 m and combined with thermistor strings in the depth range 60 260 m two were looking downward from 200 m and one was looking upward from 1400 m first maxima of vertical velocity variance occurred at two events of strong cold winds in october and november when cooling and turbulence in the shallow mixed layer generated internal waves in the thermocline beginning in late november the marginal ice zone expanded eastward over the central greenland sea reaching its maximum extent in late december in mid january a bay of ice free water opened over the central greenland sea leaving a wedge of ice the is odden curled around it along the axis of the jan mayen current and then northeastward and existing well into april 1989 below the ice a mixed layer at freezing temperatures developed that increased in thickness from 60 to 120 m during the period of ice cover corresponding to an average heat loss of about 40 w m 2 through brine rejection mixed layer salinity increased steadily reducing stability to underlying weakly stratified layers roach et al 1993 during the ice cover period vertical currents were at a minimum after the opening of the ice free bay successive mixed layer deepening to 350 m occurred in conjunction with cooling events around february 1 and 15 accompanied by strong small scale vertical velocity variations upward mixing of more saline waters of atlantic origin during this phase reduced the stability further generating a pool of homogeneous water of 50 km horizontal extent in the central greenland sea preconditioned for subsequent convection to greater depths individual convection events were observed during march 6 16 associated with downward velocities at the 1400 m level of about 3 cm s l one event was identified as a plume of about 300 m horizontal scale in agreement with recently advanced scaling arguments and model results and with earlier similar observations in the gulf of lions western mediterranean the deep convection occurred in the center of the ice free bay hence brine rejection did not seem necessary for its generation plume temperatures at 1400 m were generally higher than that of the homogeneous surface pool suggesting entrainment of surrounding warmer waters on the way down mean vertical velocity over a period of convection events was indistinguishable from zero suggesting that plumes served as a mixing agent rather than causing mean downward transport of water masses however different from the surface pool that was governed by mixed layer physics the water between 400 and 1400 m was not horizontally homogenized in a large patch by the sporadic plumes overall and compared to results from the gulf of lions convection activity in the central greenland sea was weak and limited to intermediate depths in winter 1988 1989

environmental change across the paleocene eocene transition from eastern new zealand a marine palynological approach abstract recent improvements in the resolution and calibration of dinoflagellate cyst dinocyst bioevents across the paleocene eocene p e transition in new zealand allow better understanding of the relation between dinocyst variations and environmental change in southern mid high latitudes during this greenhouse climate combining information from land spore pollen assemblages with coeval dinocyst records allows evaluation of plant changes in a marine based timeframe palynological associations at tawanui and moeraki hampden eastern new zealand fluctuate across the p e transition and local palynological phases are recognized the onset of major fluctuations in dinocyst assemblages coincide with the intense warmth and excess carbon of the initial eocene thermal maximum ietm changes in sea surface temperature sst appear to have been the main environmental factor that affected dinoflagellates short lived intervals of higher ssts suggested by a high relative abundance of the apectodinium complex are seen during the ietm and lower eocene abundant cysts of probable heterotrophic dinoflagellates suggest surface waters remained relatively eutrophic for up to 0 5 myr after the onset of the ietm perhaps in response to enhanced terrigenous input related to changes in the character and pattern of continental weathering in contrast to dinocysts spore pollen assemblages suggest plant communities remained rather stable across the p e transition vegetation was dominated by a mesothermal conifer dominated multistratal rainforest and low latitude nypa mangroves were established by the uppermost paleocene plants in this region show no clear response to the ietm and the predominant vegetation change may have occurred at least 1 5 myr later characterized by an increase in mesothermal megathermal angiosperm plants

tidally induced clouds of suspended sediment connected to shallow water coral reefs abstract the bay of banten west java indonesia represents a shallow coastal embayment harboring coral reefs subject to extremely turbid conditions the sedimentary regime and flow structure of two contrasting coral reef islands in the embayment were investigated to identify the mechanisms responsible for mean and peak levels of suspended sediment concentration ssc around the reefs arrays of in situ calibrated optical backscatter obs sensors were deployed across the reef slopes far field conditions were simultaneously monitored using an acoustic doppler current profiler adcp and a conductivity temperature and depth ctd probe equipped with an obs sensor in addition hydrographic surveys were conducted using the adcp attached to a small fishing boat navigating transects perpendicular to the reef islands the direct influence of river plumes was found to be insignificant waves act only in the uppermost few meters of the reef slopes where coral growth is most abundant and little sediment is available for resuspension tidal currents are the primary cause of high turbidity which was inferred from peaks in the diurnal and semidiurnal frequency bands of ssc spectra and the large depths where the turbidity variation sometimes initiates the entrained sediment disperses upward across the reef slopes which is likely due to a secondary current associated with bending of the flow along the curved hydraulically rough reef slopes in weakly stratified ambient waters changes in sediment availability variable critical shear stresses for erosion and deposition and the formation and evanescence of island wakes may explain the high variability of ssc at the reef slopes

dinoflagellate cyst stratigraphy of the palaeogene strata from the hellefisk 1 ikermiut 1 kangâmiut 1 nukik 1 nukik 2 and qulleq 1 wells offshore west greenland abstract a new palaeogene dinoflagellate cyst stratigraphy from offshore west greenland has been described based on the strata from the hellefisk 1 ikermiut 1 kang miut 1 nukik 1 nukik 2 and qulleq 1 wells twenty one palynological intervals are defined from the late eocene to the late early paleocene this stratigraphy has been correlated with a new microfossil zonation and previous established north sea zonations the stratigraphy and well correlation are based on last appearance datum events and abundances of stratigraphically important species from 355 samples 148 of which are sidewall core samples a major middle eocene hiatus spanning the early lutetian and a major early paleocene hiatus spanning the late santonian late cretaceous to the early danian have been recognised from the offshore deposits

a field and laboratory study of wave damping by grease ice in a field and laboratory study we discuss the formation growth and wave absorption properties of grease ice our field observations show that grease ice formation occurs under cold windy conditions in both leads and polynyas in leads grease ice forms in the open water then is herded to the down wind edge of the lead in polynyas a langmuir circulation herds the grease ice into long plumes parallel to the wind in the laboratory we grow grease ice in a wave tank and measure its wave absorption properties for single frequency two dimensional waves on a large scale we find that the thickness of the grease ice which increases away from the paddle is determined by a balance between the wave momentum flux and the free surface tilt on a small scale our photographs show that the crystals which make up the grease ice consist of discs measuring about 1 mm in diameter and 1 10 m thick which at low rates of shear sinter together into larger clumps yielding a viscosity increase to measure this non linear viscosity we study the decay of wave amplitude between two critical distances measured inwards from the leading edge the first occurs when the depth of grease ice exceeds k 1 where k is the wave number the second further distance is a line of transition from liquid to solid behavior which we call the dead zone between these two distances the wave amplitude decays with a linear slope which increases as a 0 k 2 where a0 is the wave amplitude in open water concurrent measurements of ice concentration show that it increases from values of 18 22 at the leading edge to a local maximum of 32 44 at the dead zone while the values at the dead zone increase non linearly with a0k finally comparison of the observed to that calculated from a yield stress viscosity model shows if the yield stress coefficient is proportional to the incident wave momentum flux the model predicts the observed

ice rafted debris ird based sea ice expansion events during the past 100 kyrs in the okhotsk sea abstract ice rafted debris ird from sediment traps surficial sediments and sediment cores were investigated in order to reconstruct the extent history of sea ice cover during the last 100 kyrs in the okhotsk sea the seasonal ird buried into the sediments during and just after sea ice melting in spring consists of silt and sand size terrigenous particles the spatial distribution of ird within surficial sediments clearly corresponds to the extent of sea ice coverage sea ice expanded to a maximum extent during the glacial periods although sea ice cover was not perennial the okhotsk sea sea ice expansion osie events which are recognized by millennial scale abrupt peaks of ird content have occurred 13 times during the past 100 kyrs these events were amplified during the glacial periods a significant modification of the polar atmospheric circulation in the northern hemisphere is a key process in explaining these osie events

sequence biostratigraphy and paleoenvironmental reconstruction in the early eocene figols group of the tremp graus basin south central pyrenees spain the dinoflagellate cyst palynofacies and foraminiferal records from the early eocene figols group of the spanish pyrenees exhibit major changes associated with relative sea level fluctuations and variations in efficiency of the fluvial systems the mixed siliciclastic carbonate marine succession exposed in the merli esdolomada area was deposited on the shelf in a tectonically active basin under oxic conditions in shallow to moderately deep marine waters close to the lower boundary of the photic zone influenced by river discharge from adjacent emerged lands sedimentary cycles are mainly recorded by fine grained deposits the paleoenvironmental interpretation of palynological and calcareous microfaunal records allows the definition of depositional sequences and enables to trace basinward surfaces identified in more proximal settings by means of sedimentological facies analysis at the same time the solid regional stratigraphic framework already available for the figols group allows new insights on the paleoecology of extinct taxa the merli esdolomada section me spans two 3rd order sequences the upper sequence reflects more marginal marine conditions than the lower one thus pointing to an overall shallowing trend with time in the lower sequence the maximum flooding interval is characterised by a rich and diverse microfauna highest relative abundances of marine phytoplankton and typically neritic dinoflagellate cyst dinocyst assemblages dominated by spiniferites and cordosphaeridium the final phase of the highstand systems tract in proximity of the main sequence boundary is characterised by a decrease in abundance and diversity of dinocysts with the dominance of the lagoonal genus polysphaeridium and by decreased microfaunal diversity discorbids miliolids larger foraminifers palynological records permit the reconstruction of activation and deactivation phases of the fluvial systems variations in runoff from the hinterland nutrient delivery to the sea and productivity in surface waters of the tremp graus basin the overall abundance of spiniferites and the scarcity of peridinioid cysts lingulodinium pediastrum and botryococcus algae are interpreted to indicate oligotrophic conditions during the deposition of the investigated succession recurrent intervals where the temporary disappearance of spiniferites corresponds to highest relative abundances of operculodinium and herbaceous debris are the main evidence for river plumes and denote periods of enhanced fluvial discharge reflecting a milankovitch type cyclicity the rotalia group which shows abundance peaks of cuvillierina spp in the shallower intervals is often associated with these episodes thus suggesting for this taxon more tolerance to turbidity than larger foraminifera within the maximum flooding zone a thalassiphora patula acme corresponding to the local disappearance of homotryblium is deemed to record the distal expression of a fluvial activation which triggered water salinity stratification despite broad morphological similarities homotryblium exhibits more cosmopolitan preferences than polysphaeridium which is instead confirmed as a lagoonal euryhaline taxon the increase of spinizonocolpites pollen toward the top of the figols group records the northwestward migration of nypa mangrove palms from southern europe during the mid early eocene

antarctic sea ice microwave signatures and their correlation with in situ ice observations the general characteristics and microwave radiative properties of sea ice in the weddell sea region during the onset of spring are studied by using the nimbus 7 scanning multichannel microwave radiometer smmr and other satellite sensors in conjunction with in situ observations from the mikhail somov the position of the ice edge the gradient of ice concentration and the width of the marginal ice zone are inferred from the microwave data and are found to be consistent with ship observations especially at 18 ghz the sensitivities of the various smmr frequencies to surface and other effects are investigated by using multi spectral cluster analysis the results show considerable variability in emissivity especially at 37 ghz likely associated with varying degrees of surface wetness ice concentrations are derived by using two methods one that assumes fixed emissivities for consolidated ice and an iterative procedure that accounts for the variable emissivities observed by using the procedure that allows the emissivities to be variable gives ice concentrations that are more consistent with qualitative field observations

magnetic and calcareous nannofossil stratigraphy of the lower palaeogene formations of the hampshire and london basins a magnetostratigraphic study of the lower palaeogene formations exposed in the hampshire and london basins southern uk has led to the identification of eight stratigraphically distinct normal polarity magnetozones within an otherwise reverse polarity sedimentary sequence which spans the late palaeocene to middle eocene a complementary study of the calcareous nannofossil biostratigraphy of these sections and related sections elsewhere in nw europe allows a correlation of this succession of normal polarity magnetozones with the biostratigraphically calibrated geomagnetic polarity timescale based on marine magnetic anomalies it is concluded that the normal polarity chrons corresponding to anomalies 20 21 and 23 are recorded within the huntingbridge earnley and wittering divisions of the bracklesham group respectively that anomalies 24a and 24b are represented within divisions d to b2 of the london clay and anomaly 26 is represented in the lower part of the thanet beds an additional normal polarity magnetozone within the oldhaven beds is believed to represent a short normal polarity event between anomalies 24b and 25 anomalies 22 and 25 appear not to be represented in the uk lower palaeogene succession because of major unconformities at the early middle eocene boundary within the wittering division of the bracklesham group and within the late palaeocene respectively the former appears to correlate with a widespread erosional event in the oceans identified from seismic records vail et al 1979 and interpreted as reflecting a major eustatic sea level fall

revised lower palaeogene lithostratigraphy for the outer moray firth north sea abstract the lower palaeogene lithostratigraphy of the outer moray firth has been revised using wireline log and biostratigraphic data a two fold subdivision into the montrose and moray groups is recognized the montrose group consists of the maureen and lista formations whereas the younger moray group contains the sele balder dornoch and beauly formations the lista formation contains the arenaceous andrew and balmoral members separated by the tuffaceous glamis member the dornoch and beauly formations are prograding shelfal sandstone units that pass basinwards into the age equivalent dominantly argillaceous sele and balder formations the sele formation contains the forties and cromarty members which are locally developed sand rich units stratigraphic analysis has led to the identification of a number of consistently developed high gamma log markers that are interpreted as condensed mudstone horizons these markers are believed to record clastic sediment starvation during periods of maximum marine transgression they often have a strong biostratigraphic fingerprint coinciding with influxes of rich concentrations of microfossils and microflora they are interpreted as the product of synchronous regional transgressive events and have been an important aid to the development of a confident lithostratigraphic framework for the lower palaeogene of the outer moray firth

observations of ice thickness and frazil ice in the st lawrence island polynya from satellite imagery upward looking sonar and salinity temperature moorings 1 for the 1999 winter this paper examines the behavior of the bering sea st lawrence island polynya using a combination of advanced very high resolution radiometer avhrr radarsat synthetic aperture radar sar meteorological data over winter moored upward looking sonars uls and seabird salinity temperature sensors we define a thermal ice thickness from the avhrr retrieval of ice surface temperature combined with meteorological observations and a heat flux model south of the island we compare the uls and thermal thicknesses for congelation and frazil ice when the satellites observe congelation ice over the ulss the uls and thermal ice thicknesses generally agree when sar observes langmuir plumes over the ulss which indicate frazil ice formation the ulss show scatterers at 5 20 m depths in the water column and the seawater temperatures are either within 0 01 c of freezing or are slightly supercooled this suggests that during frazil events crystals either nucleate at depth or are transported to depth by the langmuir circulation the combination of the sar imagery and uls observations also allow measurement of the pack ice advection velocity the polynya width and the downwind frazil accumulation thickness giving widths of 10 to 30 km and thicknesses of 0 1 0 2 m substitution of these observed values with the heat flux into the pease polynya model yields polynya widths that approximately agree with the observed