dinoflagellate cyst assemblages as tracers of sea surface conditions in the northern north atlantic arctic and sub arctic seas the new n 677 data base and its application for quantitative palaeoceanographic reconstruction the distribution of dinoflagellate cyst dinocyst assemblages in surface sediment samples from 677 sites of the northern north atlantic arctic and sub arctic seas is discussed with emphasis on the relationships with sea surface parameters including sea ice cover salinity and temperature of the coldest and warmest months difficulties in developing a circum arctic data base include the morphological variation within taxa e g operculodinium centrocarpum islandinium cezare and polykrikos sp which probably relate to phenotypic adaptations to cold and or low salinity environments sparse hydrographical data together with large interannual variations of temperature and salinity in surface waters of arctic seas constitute additional limitations nevertheless the use of the best analogue technique with this new dinocyst data base including 677 samples permits quantitative reconstruction of sea surface conditions at the scale of the northern north atlantic and the arctic domain the error of prediction calculated from modern assemblages is 1 3 ca nd 1 8 c for the temperature of february and august respectively 1 8 for the salinity and 1 5 months yr 1 for the sea ice cover application to late quaternary sequences from the western and eastern subpolar north atlantic labrador sea and barents sea provide reconstructions compatible with those obtained using the previous dinocyst data base n 371 which mainly included modern data from the northern north atlantic copyright 2001 john wiley sons ltd journal of quaternary science

relationships between dinoflagellate cyst assemblages in surface sediment and hydrographic conditions in the bering and chukchi seas palynological analyses were performed on 52 surface sediment samples from the eastern part of the bering sea and chukchi sea in order to document the regional distribution of dinoflagellate cyst assemblages and their relationship with sea surface conditions the assemblages present a relatively high species diversity 20 taxa are recovered routinely especially in the bering sea where they are dominated by operculodinium centrocarpum and the cyst of pentapharsodinium dalei accompanied mainly by spiniferites elongatus s l spiniferites ramosus impagidinium pallidum brigantedinium spp islandinium minutum selenopemphix quanta selenopemphix nephroides quinquecuspis concreta and the cyst of polykrikos kofoidii the percentages of the main taxa vary with latitude and principal component analysis shows that the distribution of assemblages is closely related to hydrographic conditions notably the seasonal duration of sea ice cover and the sea surface temperature in february the dinoflagellate cyst assemblages from the bering sea differ significantly from those of subarctic seas of the north atlantic with respect to their species composition and relationships with sea surface conditions in particular the occurrence of the cyst of polykrikos kofoidii and quinquecuspis concreta and the positive correlation between the percentages of operculodinium centrocarpum and the extent of sea ice constitute peculiar features in the bering sea assemblages copyright 2001 john wiley sons ltd journal of quaternary science

satellite color observations of spring blooming in bering sea shelf waters during the ice edge retreat in 1980 coastal zone color scanner czcs images of the eastern bering sea between april 27 and july 22 1980 were analyzed in a study of the biological response of the bering sea system to the 1000 km retreat of the ice edge across the shelf and to the subsequent establishment of the highly stratified water column characteristic of spring and early summer images from the norton sound area showed seasonal changes both in an ice edge bloom near the sound and in the yukon river sediment plume inside the sound three spring images revealed details of several stages of the classic spring bloom development over the shelf which typically begins inshore and progresses offshore high pigment concentrations were observed over the inner shelf domain in early spring and developing across the middle shelf domain in may a band of high chlorophyll concentration seaward of the 100 m isobath in the approximate area of the outer domain thought to have been caused by periodic offshore movements of shelf waters was seen in late july the phytoplankton pigment concentrations derived from the satellite data appeared to be much lower than those observed by the processes and resources of the bering sea shelf group but the spatial and temporal distributions agreed well with trends identified during that experiment while it is clear that the ice edge and open water spring bloom events together make up the most important component of the seasonal bering production cycle the extraordinary spatial and temporal extent of the classic spring bloom over the shelf underscores the significance of the contribution made by this phenomenon to the annual production budget of the eastern bering shelf

gradational thresholds and landform singularity significance for quaternary studies abstract geomorphic threshold conditions have been identifed at which stream patterns change and gully initiation occurs for both the threshold conditions are defined by the parameter of relative shear stress which is a measure of the energy state of the system and is based on known values of stream slope and mean annual discharge for patterns or drainage area for gullies the probability of passing from a stream pattern to another or from stable to gullied valley floors is a smooth function of relative shear stress and so the thresholds separating the different states of the geomorphic systems are gradational the singularity of landforms prevents the identification of a sharp threshold and as a result landform sensitivity will differ within the same area and under the same conditions therefore geomorphic predictions and postdictions will be uncertain and quaternary correlations will lack precision

palynomorph distribution in recent sediments from the labrador sea surface sediments from the labrador sea and baffin bay have been examined for their palynomorph content pollen and spore assemblages reflect the vegetation zones of eastern canada although long distance atmospheric transport results in over representation of pinus and spores a linear decrease of pollen input is observed with distance from the source vegetation the abyssal domain receives less than 2 of the initial input the abundance of dinoflagellate cysts reflects a relatively high primary productivity in surface water masses which seems proportional to the benthic productivity as shown by the concentrations of organic linings of foraminifers the relative abundance of dinoflagellate cyst taxa and principal component analysis led to the definition of three assemblages that can be related to sea surface conditions and current pattern the modern distribution of dinoflagellate cysts was used to interpret assemblages recovered in five box cores from the deep labrador sea results reveal important ch

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

tributary trunk stream relations in a cut and fill landscape a case study from wolumla catchment new south wales australia at the time of european settlement of the south coast of new south wales australia in the mid nineteenth century river courses were discontinuous throughout wolumla catchment within a few decades of settlement intact valley fills had been transformed into incised channels along trunk streams this induced associated patterns of secondary incision into tributary valley fills three of the primary subcatchments in wolumla catchment became fully incised while an upland swamp and a floodout i e sand sheet deposits atop an intact valley floor remain in mid catchment of the fourth subcatchment of the 70 lower order tributaries which join the trunk streams in the four subcatchments 27 have incised 12 of which are discontinuously incised incision of tributary streams in wolumla catchment cannot be explained by subcatchment area and slope relations the position of the trunk stream channel within the valley floor trough is the key determinant of whether or not tributary streams have incised changes to river morphology since european settlement have altered the linkage of tributary streams to the trunk stream impacting directly on the within catchment transfer of water and sediment

observed tides on the northeastern bering sea shelf bottom pressure observations november 1981 to august 1982 show that the diurnal tides dominate the outer reaches of the northeastern bering sea shelf the diurnal tides decrease inshore from the shelf break maximum k1 amplitude of 38 cm and appear to be evanescent sverdrup poincare waves on the outer shelf the k1 amplitude 2 3 cm in the bering strait is 6 of that at the shelf break the diurnal phase lags vary little 322 359 g for the k1 tide between the stations north and eastward from the shelf break the tides become smaller and more semidiurnal the semidiurnal amplitudes vary considerably between stations these observations show the effects of semidiurnal amphidromic systems predicted by numerical models the m2 amplitude 7 6 cm in the bering strait is about a third of that at the shelf break m2 amplitude of 23 cm the semidiurnal phase lags are earliest at the shelf break 87 g for m2 and appear to increase toward st lawrence island 336 g for m2 in shpanberg strait and the bering strait 202 g for m2 the tidal harmonic constants fluctuated seasonally possibly in response to the variations in ice cover the diurnal amplitudes generally increased during winter while the semidiurnal amplitudes decreased at the shelf break the k1 amplitude increased 2 5 cm or 7 but the o1 and semidiurnal m2 amplitudes 0 4 cm or 2 for m2 showed little variation in bering strait the variations in m2 amplitude up to 3 0 cm amounted to 37 of the mean amplitude the decrease may be due to attenuation of the m2 tide from the arctic ocean in addition to damping of the m2 tide on the northeastern bering sea shelf shorter term fluctuations were also observed in the tides the tidal fluctuations may contribute to those observed in the deep sea numerical models show a set of amphidromic systems including a semidiurnal system off cape navarin and rapid phase transitions in the vicinity of some of the stations these models are in relatively good agreement with the observations

slope area thresholds of road induced gully erosion and consequent hillslope channel interactions pikes peak highway is a partially paved road between cascade colorado and the summit of pikes peak significant gully erosion is occurring on the hillslopes due to the concentration of surface runoff the rearrangement of drainage pathways along the road surface and adjacent drainage ditches and the high erodibility of weathered pikes peak granite that underlies the area as a result large quantities of sediment are transported to surrounding valley networks causing significant damage to water quality and aquatic wetland and riparian ecosystems this study establishes the slope drainage area threshold for gullying along pikes peak highway and a cesium 137 based sediment budget highlighting rates of gully erosion and subsequent valley deposition for a small headwater basin

stelladinium bifurcatum n sp a distinctive extant thermophilic heterotrophic dinoflagellate cyst from the late quaternary of the eastern pacific and east equatorial atlantic oceans abstract stelladinium bifurcatum n sp is a large and distinctive brown heterotrophic dinoflagellate cyst recorded from upper pleistocene through modern sediments of the eastern pacific modern sediments of the western bay of bengal and sediment traps from the south china sea and upper pleistocene through middle holocene deposits of the east equatorial atlantic it is distinguished by prominent apical and antapical horns numerous long processes distributed along the cingulum tips of horns and processes that are characteristically solid or thickened and taper to points a prominent flagellar scar and an archeopyle formed by the second anterior intercalary plate with the operculum adnate along the right lateral margin stelladinium bifurcatum has been recorded in the literature under several names including stelladinium reidii and the cyst of protoperidinium stellatum from which it differs in having abundant cingular processes at least one of which usually has a strongly divergent bifurcation re examination of published records shows stelladinium bifurcatum to have a tropical subtropical neritic distribution in modern sediments of the eastern pacific margin and to be associated with high biological productivity similarly in pleistocene holocene sediments off west equatorial africa stelladinium bifurcatum is linked to elevated sea surface temperatures during the last deglaciation and it serves as a marker of river discharge associated with an increase in monsoonal dynamics at this time

the nutrient salinity and stable oxygen isotope composition of bering and chukchi seas waters in and near the bering strait seawater nutrient salinity and oxygen 18 data collected from 1990 to 1993 in the bering and chukchi seas were used to identify potential sources of nutrients and water masses that result in formation of the arctic ocean upper halocline and its associated nutrient maximum water matching the delta sup 18 o values of the arctic ocean upper halocline and containing sufficient or a nearly sufficient nutrient and salinity concentration was collected in subsurface waters in the summer in portions of the bering sea particularly the gulf of anadyr however nutrient concentrations significantly declined in this north flowing water over the shallow continental shelf before it reached the bering strait as a consequence of biological utilization and dilution with nutrient poor and oxygen 18 depleted fresh water therefore it does not appear likely that the flow of unaltered water through the bering strait in the summer plays a critical role in the formation of the arctic ocean upper halocline the role of other mechanisms for contributing pacific derived waters to the arctic ocean nutrient maximum is considered copyright 1997 american geophysical union

application of artificial neural networks ann to high latitude dinocyst assemblages for the reconstruction of past sea surface conditions in arctic and sub arctic seas the artificial neural network ann method was applied to dinoflagellate cyst dinocyst assemblages to estimate palaeoceanographical conditions the ann method was adapted to three distinct data bases covering the northern north atlantic n 371 plus the arctic seas n 540 and the bering sea n 646 the relative abundance of 23 dinocyst taxa was calibrated against hydrographic variables sea surface temperature salinity and density in february and august and seasonal extent of sea ice cover using anns the estimation of hydrographical parameters based on an ann yields high coefficients of correlation between observations and reconstructions for each variable selected the validation tests performed on the different data bases suggest more accurate calibration at the scale of the north atlantic and arctic n 540 than on a multibasin scale i e when including the subpolar north pacific n 646 the ann calibrations and the modern analogue technique mat have been applied to two sequences from the northwest north atlantic spanning the past 25 000 yr for the purpose of comparison both approaches yielded similar results generally within the range of their respective uncertainties demonstrating their suitability the main discrepancies generally correspond to assemblages with poor modern analogues for which we have to admit a higher degree of uncertainties in the reconstruction whatever the approach used copyright 2001 john wiley sons ltd

dinoflagellate cyst distribution in surface sediments from the arabian sea northwestern indian ocean in relation to temperature and salinity gradients in the upper water column abstract surface sediment samples from the arabian sea indian ocean have been investigated for their dinoftagellate cyst content to obtain information about the environmental affinity and potential palaeo environmental significance of the cyst species their distribution is compared with the environmental characteristics of the overlying water column using detrended correspondence analysis and canonical correspondence analysis the distribution patterns of individual species are compared with temperature and salinity gradients over four seasons the main variation in cyst association appears to be related to variation in those gradients affected by the sw and ne monsoons on the basis of this relationship four groups of species can be recognised 1 central arabian sea species 2 sw monsoon upwelling species 3 ne monsoon eutrophic species 4 species with no distinct relationship with monsoon related gradients the downcore occurrences of species from groups 1 2 and 3 have potential as indicators for palaeo sw and ne monsoon strength

last glacial maximum to holocene sea surface conditions at umnak plateau bering sea as inferred from diatom alkenone and stable isotope records 1 the bering sea gateway between the pacific and arctic oceans impacts global climate when glacial interglacial shifts in shore line position and ice coverage change regional albedo previous work has shown that during the last glacial termination and into the holocene sea level rises and sea ice coverage diminishes from perennial to absent yet existing work has not quantified sea ice duration or sea surface temperatures sst during this transition here we combine diatom assemblages with the first alkenone record from the bering sea to provide a semiquantitative record of sea ice duration sst and productivity change since the last glacial maximum lgm during the lgm diatom assemblages indicate that sea ice covered the southeastern bering sea perennially at 15 1 cal ka b p the diatom assemblage shifts to one more characteristic of seasonal sea ice and alkenones occur in the sediments in low concentrations deglaciation is characterized by laminated intervals with highly productive and diverse diatom assemblages and inferred high coccolithophorid production at 11 3 cal ka b p the diatom assemblage shifts from one dominated by sea ice species to one dominated by a warmer water north pacific species simultaneously the sst increases by 3 c and the southeastern bering sea becomes ice free year round productivity and temperature proxies are positively correlated with independently dated records from elsewhere in the bering sea the sea of okhotsk and the north pacific indicating that productivity and sst changes are coeval across the region

process length variation of the cyst of the dinoflagellate protoceratium reticulatum in the north pacific and baltic skagerrak region calibration as an annual density proxy and first evidence of pseudo cryptic speciation process length variation of cysts of the dinoflagellate protoceratium reticulatum claparede et lachmann butschli in surface sediments from the north pacific was investigated the average process

variability of sea ice cover in the chukchi sea western arctic ocean during the holocene 1 dinocysts from cores collected in the chukchi sea from the shelf edge to the lower slope were used to reconstruct changes in sea surface conditions and sea ice cover using modern analogue techniques holocene sequences have been recovered in a down slope core b15 2135 m 75 44 n sedimentation rate of 1 cm kyr 1 and in a shelf core p1 201 m 73 41 n sedimentation rate of 22 cm kyr 1 the shelf record spanning about 8000 years suggests high frequency centennial oscillations of sea surface conditions and a significant reduction of the sea ice at circa 6000 and 2500 calendar cal years b p the condensed offshore record b15 reveals an early postglacial optimum with minimum sea ice cover prior to 12 000 cal years b p which corresponds to a terrestrial climate optimum in bering sea area dinocyst data indicate extensive sea ice cover 10 months yr 1 from 12 000 to 6000 cal years b p followed by a general trend of decreasing sea ice and increasing sea surface salinity conditions superimposed on large amplitude millennial scale oscillations in contrast 18o data in mesopelagic foraminifers neogloboquadrina pachyderma and benthic foraminifers cibicides wuellerstorfi reveal maximum subsurface temperature and thus maximum inflow of the north atlantic water around 8000 cal years b p followed by a trend toward cooling of the subsurface to bottom water masses sea surface to subsurface conditions estimated from dinocysts and 18o data in foraminifers thus suggest a decoupling between the surface water layer and the intermediate north atlantic water mass with the existence of a sharp halocline and a reverse thermocline especially before 6000 years b p the overall data and sea ice reconstructions from core b15 are consistent with strong sea ice convergence in the western arctic during the early holocene as suggested on the basis of climate model experiments including sea ice dynamics matching a higher inflow rate of north atlantic water

dinoflagellate cyst distribution in high latitude marine environments and quantitative reconstruction of sea surface salinity temperature and seasonality a data base of 179 reference sites documents the relations between the assemblages of organic walled dinoflagellate cysts and sea surface temperature salinity and seasonality throughout the north atlantic adjacent subpolar basins labrador sea baffin bay irminger and iceland basins and epicontinental environments off eastern canada estuary and gulf of st lawrence hudson bay principal component analyses show close relationships between dinoflagellate cyst data and sea surface conditions the first component 71 1 of the variance correlates with the winter temperature salinity and seasonal duration of sea ice cover whereas the second component 11 3 of the variance appears mainly related to summer temperature transfer functions using the best analogue method were tested by reconstructing modern sea surface conditions on the basis of the reference dinoflagellate cyst assemblages the correlation coefficient between instrumental averages and reconstructed values ranges from 0 87 august tem

reconstruction of sea surface conditions at middle to high latitudes of the northern hemisphere during the last glacial maximum lgm based on dinoflagellate cyst assemblages abstract a new calibration database of census counts of organic walled dinoflagellate cyst dinocyst assemblages has been developed from the analyses of surface sediment samples collected at middle to high latitudes of the northern hemisphere after standardisation of taxonomy and laboratory procedures the database comprises 940 reference data points from the north atlantic arctic and north pacific oceans and their adjacent seas including the mediterranean sea as well as epicontinental environments such as the estuary and gulf of st lawrence the bering sea and the hudson bay the relative abundance of taxa was analysed to describe the distribution of assemblages the best analogue technique was used for the reconstruction of last glacial maximum lgm sea surface temperature and salinity during summer and winter in addition to sea ice cover extent at sites from the north atlantic n 63 mediterranean sea n 1 and eastern north pacific n 1 three of the north atlantic cores from the continental margin of eastern canada revealed a barren lgm interval probably because of quasi permanent sea ice six other cores from the greenland and norwegian seas were excluded from the compilation because of too sparse assemblages and poor analogue situation at the remaining sites n 54 relatively close modern analogues were found for most lgm samples which allowed reconstructions the new lgm results are consistent with previous reconstructions based on dinocyst data which show much cooler conditions than at present along the continental margins of canada and europe but sharp gradients of increasing temperature offshore the results also suggest low salinity and larger than present contrasts in seasonal temperatures with colder winters and more extensive sea ice cover whereas relatively warm conditions may have prevailed offshore in summer from these data we hypothesise low thermal inertia in a shallow and low density surface water layer

identifying the signature of sea surface properties in dinocyst assemblages implications for quantitative palaeoceanographical reconstructions by transfer functions and analogue techniques abstract dinoflagellate cyst dinocyst assemblages are widely used for the reconstruction of multiple oceanographic variables through the application of transfer functions there is evidence that the number and kind of variables driving compositional changes in dinocyst assemblages vary regionally and that the selection of driving factors and the evaluation of transfer function performances are method specific and complicated by spatial autocorrelation here we used two new modern datasets from the northern hemisphere atlantic arctic and the northern hemisphere pacific oceans to re evaluate the impact of sea surface properties in dinocyst assemblages we determined the dimensionality of the dinocyst ecological response and identified the main drivers for both regions we calibrated and evaluated transfer function methods for the prediction of these variables and estimated their performances considering spatial autocorrelation in both datasets multiple environmental variables mutually and independently affect assemblage compositions but the number and kind of these variables differ between datasets we detected spatial autocorrelation which was often due to environmental similarity but some variables appeared to reflect geographical closeness implying that spatial independence between sample sites depends upon the variables we identified different primary drivers in both areas highlighting the merit of regional calibrations and the necessity to carry out variable selection for each region separately the multiple gradients identified imply that potentially multiple parameters could be reconstructed from the same fossil dinocyst assemblages however as the multiple gradients reflect geographical structuring we propose that regional calibrations even at the expense of generalisation could improve the reliability and interpretation of transfer function reconstructions

micropaleontology and palynology of core par87a 10 a 23 000 year record of paleoenvironmental changes in the gulf of alaska northeast north pacific micropaleontological data of core par87a 10 reveal that the last glacial interval prior to 13 ka was marked by low biogenic fluxes and poor caco3 preservation quantitative estimates of sea surface conditions based on dinocyst assemblages suggest that cold temperatures and freezing winter conditions existed during this period the glacial to interglacial transition i e the 13 8 ka interval was characterized by an increase in fluxes of microfossils indicating enhanced productivity in surface waters a higher biogenic carbonate production probably resulted in better preservation of caco3 this interval was marked by relatively low salinity and by sea surface temperatures increasing toward modern values relatively high pollen flux during the transition suggests nutrient inputs through atmospheric and or fluvial transport from the adjacent north american continent after 8 ka diminished fluxes of plankton concomitant with a decline in pollen input are associated with decreasing nutrient supply as predominantly eastward winds became established over the north pacific

middle pleistocene to holocene palynostratigraphy of ocean drilling program site 887 in the gulf of alaska northeastern north pacific a palynological investigation was undertaken on the upper 29 m of sediment at ocean drilling program odp site 887 spanning the last 430 000 years i e isotopic stages 12 to 1 pollen and dinocyst assemblages reveal a major ecostratigraphical boundary at the middle late pleistocene transition the middle pleistocene pollen data doc ument the occurrence of a spruce forest vegetation in the source area likely located on the adjacent alaskan coast whereas the late pleistocene is marked by higher inputs of pine shrub and herb taxa suggesting predominant inputs from a more open landscape the middle pleistocene is characterized by a low diversity in dinocyst assemblages which are dominated by operculodinium centrocarpum whereas the late pleistocene is marked by the significant oc currence of pentapharsodinium dalei pyxidinopsis reticulata and by high percentages of brigantedinium spp such as semblages suggest open oceanic and cool temperate conditions during the middle pleistocene changing toward generally colder and less saline conditions during the late pleistocene in addition large fluctuations in the dinocyst assemblages during the late pleistocene are recorded in phase with the main shifts in the isotopic stratigraphy a new dinocyst taxon spiniferites alaskensis sp nov exclusively recorded in sediments of the isotopic substage 5e is de scribed herein resume une analyse palynologique a ete realisee sur une sequence sedimentaire de 29 metres prelevee au site odp 887 et couvrant les derniers 430 000 ans soit les stades isotopiques 12 a 1 les assemblages de pollen et de dinokystes revelent une transition ecostratigraphique majeure entre le pleistocene moyen et le pleistocene superieur les assembla ges polliniques du pleistocene moyen indiquent la presence d une vegetation dominee par l epinette et l aulne dans la region source qui etait sans doute localisee le long des cotes de l alaska de forts pourcentages de pin et des taxons arbustifs et herbaces au pleistocene superieur indiquent des apports issus d un paysage plus ouvert le pleistocene moyen est caracterise par une faible diversite dans les assemblages de dinokystes et par la dominance de operculodi nium centrocarpum tandis que le pleistocene superieur est marque par pentapharsodinium dalei pyxidinopsis reticulata et des pourcentages eleves de brigantedinium spp les assemblages suggerent des conditions oceaniques temperees fraiches pendant le pleistocene moyen et des eaux de surface plus froides et moins salines au cours du pleistocene su perieur par ailleurs de larges fluctuations sont enregistrees dans les assemblages de dinokystes au pleistocene supe rieur en phase avec la stratigraphie isotopique parmi les dinokystes une nouvelle espece spiniferites alaskensis sp nov observee exclusivement pendant le sous stade isotopique 5e est decrite ici marret et al 386

an expanded modern dinoflagellate cyst dataset for the southwest pacific and southern hemisphere with environmental associations organic walled dinoflagellate cyst dinocyst assemblages were examined in 120 sea floor sediment samples from the southwest sw pacific to highlight dinocyst distribution in the region from these 120 samples census counts of 40 samples were added to previously published census data from the southern hemisphere to form a modern dataset of 311 samples sh 311 cluster analysis k means clustering of a 98 sample sub set from the sw pacific nz 98 reveals four distinct assemblages which coincide with modern subantarctic surface water the subtropical front and two clusters from subtropical surface water a similar clustering of the sh 311 dataset reveals an additional three assemblages two associated with polar waters colder than those sampled in the sw pacific and one that may be endemic to the south atlantic ocean multivariate ordination canonical correspondence analysis and redundancy analysis indicates that the dinocyst assemblages change most along a sea surface temperature sst gradient in both the regional sw pacific and southern hemisphere datasets sst accounts for 38 to 56 of the species environmental relationship after removal of covarying variables and contributes 2 3 times the explainable inertia than the other environmental variables tested both modern datasets sh 311 and nz 98 are suitable as a training set for quantitative palaeotemperature transfer functions applied to late quaternary records with the caveat that the modern assemblage also displays sensitivity to productivity shoreline proximity bottom water oxygen and water mass variation that may be exploited in certain situations c 2013 elsevier b v all rights reserved

on the relationship between atmospheric circulation and the fluctuations in the sea ice extents of the bering and okhotsk seas monthly and 3 day averaged nimbus 5 electrically scanning microwave radiometer sea ice data have been analyzed to document the fluctuations of the bering sea and sea of okhotsk ice covers for the four winters 1972 1973 through 1975 1976 on the short term seasonal and interannual time scales and to define those periods for which there is an out of phase relationship between the fluctuations of the two sea ice covers the sea ice fluctuations are shown to be related to changes in the position and intensity of quasi stationary high and low pressure systems associated with large scale standing wave patterns in the atmosphere through a comparison of the areal changes in ice cover with changes in the amplitude and phase of zonal harmonics 1 2 and 3 of the sea level pressure field on the seasonal time scale the sea level pressure for december the month of most rapid seasonal sea ice growth for both the bering and okhotsk seas is dominated by harmonic 2 which explains almost 60 of the total sea level pressure variance on average over the four winters the phase of harmonic 2 which is associated with the position of the aleutian low shifts from 156 e in 1972 1973 to 190 e in 1975 1976 thus providing a connection between the increasingly heavy bering sea ice cover over these four winters and the general circulation of the atmosphere on the short term episodes of midwinter bering sea ice retreat are generally preceded by or coincident with the breakdown of harmonic 1 and the intensification of harmonics 2 and 3 these episodes are also related to the coincidence of the phases of harmonics 2 and 3 with a mean position of 165 e this result is in excellent agreement with a study of the north pacific oscillation showing that the two modes of the oscillation are associated with the longitudinal position of the aleutian low it is suggested here that these two modes result from changes in the amplitudes and phases of atmospheric long waves 1 2 and 3 evidence is also presented indicating that the interaction of standing and transient components of wave 1 may play an important role in these fluctuations finally these results establish an observational connection relating climate dynamics to changes in ice covers in seasonal sea ice zones

distribution of dinoflagellate cysts and other aquatic palynomorphs in surface sediments from the beagle channel southern argentina article i nfo palynological analyses of 22 surface sediment samples from the beagle channel tierra del fuego argentina were performed in order to investigate the distribution of dinocyst assemblages and other aquatic pal ynomorphs and to explore their relationships with sea surface conditions which are regionally characterized by cold and low salinity conditions 4 9 c and 27 33 5 respectively results show relatively low dinocyst concentrations 253 to 5568 cysts g and species diversity 19 taxa identified the assemblages are mostly composed of protoperidiniaceae and appear typical of a marginal marine environment with surface waters characterized by low to moderate salinity and high nutrient content due to river inputs the assemblages are thus compatible with the occurrence of freshwater to brackish water taxa botryococcus braunii botryococcus sp polyasterias sp halodinium sp and radiosperma corbiferum the dinocyst assemblages are dominated by brigantedinium spp echinidinium spp and selenopemphix quanta accompanied by cysts of pentapharsodinium dalei islandinium minutum votadinium spinosum polykrikos kofoidii and polykrikos schwartzii the assemblages from the beagle channel show similarities with those of high latitude regions of the northern hemisphere however some taxa which were exclusively reported from relatively warm environments in the northern hemisphere occur in relatively high percentages in the beagle channel e g echinidinium delicatum and votadinium spinosum the absence of selenopemphix antarctica in the bea gle channel is consistent with its known ecological affinities since it characterizes environments marked by seasonal sea ice cover

a holocene palynological record from the northeastern laptev sea and its implications for palaeoenvironmental research a 844 cm long core ps51 118 3 77 53 54 n 132 11 92 e recovered from the upper slope 122 m water depth of the laptev sea russian arctic has been studied for pollen spores and aquatic palynomorphs including freshwater green algae and cysts of marine dinoflagellates the age model was established on the basis of radiocarbon dates obtained on marine bivalve mollusk shells the available dates suggest that the analyzed sediment was accumulated during the last ca 10 8 cal ka and reveal two intervals with markedly different sedimentation rates reflecting the sedimentary regime changes of the laptev sea shelf during postglacial sea level rise very high sedimentation rates ca 4 7 mm per year in the lower part of the core 120 866 cm between ca 9 2 and 10 8 cal ka bp reflect lower than present sea levels high erosion activity and much closer position of the palaeo shoreline with the lena and yana river mouths to the core site dramatic decrease in sedimentation rates ca 0 1 mm per year during the middle and late holocene interval reflects high sea level and decreased amount of suspended material transported to the outer shelf by rivers despite the location of the core site at the continental slope and far away from the modern coastline pollen spores and fresh water algae constitute a major part of the microfossils throughout the whole record indicating great impact of the lena and yana rivers and possibly prevalent wind regime on the pollen and non pollen palynomorph npp assemblages although a number of short term decadal to multi century oscillations deviate from the mean holocene values pollen taxa percentages and pollen based numerical biome reconstructions do not show very clear trends the latter is likely a result of the mixed environmental signal and complex pollen contribution of several large environmental regions and vegetation zones of siberia drained by the lena and yana rivers the greater pollen contribution of the forested regions to the ps51 118 3 record reflects higher pollen production of the boreal trees and shrubs over the low productive arctic vegetation the intervals of the relative increase in the tundra biome scores in the ps51 118 3 record reflect decreased arboreal pollen production or and increased landscape openness within the pollen source area and can be correlated within the uncertainty of the age models with the cold episodes observed in the greenland ice and north atlantic sediment records

reconstruction of sea surface temperature salinity and sea ice cover in the northern north atlantic during the last glacial maximum based on dinocyst assemblages past sea surface conditions over the northern north atlantic during the last glacial maximum were examined from the study of 61 deep sea cores the last glacial maximum time slice studied here corresponds to an interval between heinrich layers h2 and h1 and spanningabout 20 16 ka on a 14c time scale transfer functions based on dinocyst assemblages were used to reconstruct sea surface temperature salinity and sea ice cover the results illustrate extensive sea ice cover along the eastern canadian margins and sea ice spreading only during winter over most of the northern north atlantic on the whole much colder winter prevailed despite relatively mild conditions in august 10 15 c at most offshore sites thus suggesting a larger seasonal contrast of temperatures than today lower salinity than at present is reconstructed especially along the eastern canadian and scandinavian margins likely because of meltwater supply from the surrounding ice sheets these reconstructions contrast with those established by climap on the basis of planktonic foraminifera these differences are discussed with reference to the stratigraphical frame of the last glacial maximum which was not the coldest phase of the last glacial stage the respective significance of dinocyst and foraminifer records is also examined in terms of the thermohaline characteristics of surface waters and the vertical structure of upper water masses which was apparently much more stratified than at present in the northern north atlantic thus preventing deep water formation

electromagnetic wave propagation in disrupted coal seams it is of economic importance to locate zones of geological disturbance in longwall coal panels prior to the start of mining operations this can be done with electromagnetic em longwall attenuation tomography in which the amplitude of a single frequency wave in the 300 khz range is measured over a number of raypaths the main component of the signal is a fundamental waveguide mode zones with high attenuation rates have been observed to be zones of geological disturbance a two dimensional tm magnetic field transverse to the plane of propagation mode time domain finite difference solution was developed and used to determine the excess attenuation ea that occurs in disturbed zones ea is defined as the actual attenuation going through a disturbed zone less the attenuation for an equal length of the normal undisturbed waveguide a typical model has a coal seam bordered above and below by rock with a disturbed zone various types of disturbances such as sand channels and faults were modeled syntheti

reconstructing past sea ice cover of the northern hemisphere from dinocyst assemblages status of the approach abstract dinocysts occur in a wide range of environmental conditions including polar areas we review here their use for the reconstruction of paleo sea ice cover in such environments in the arctic ocean and subarctic seas characterized by dense sea ice cover islandinium minutum islandinium cezare echinidinium karaense polykrikos sp var arctic spiniferites elongatus frigidus and impagidinium pallidum are common and often occur with more cosmopolitan taxa such as operculodinium centrocarpum sensu wall dale cyst of pentapharsodinium dalei and brigantedinium spp canonical correspondence analyses conducted on dinocyst assemblages illustrate relationships with sea surface parameters such as salinity temperature and sea ice cover the application of the modern analogue technique permits quantitative reconstruction of past sea ice cover which is expressed in terms of seasonal extent of sea ice cover months per year with more than 50 of sea ice concentration or mean annual sea ice concentration in tenths the accuracy of reconstructions or root mean square error of prediction rmsep is 1 1 over 10 which corresponds to perennial sea ice such an error is close to the interannual variability standard deviation of observed sea ice cover mismatch between the time interval of instrumental data used as reference 1953 2000 and the time interval represented by dinocyst populations in surface sediment samples which may cover decades if not centuries is another source of error despite uncertainties dinocyst assemblages are useful for making quantitative reconstruction of seasonal sea ice cover

distribution patterns of dinoflagellate cysts and other organic walled microfossils in recent norwegian greenland sea sediments dinoflagellate cysts and other organic walled microfossils have been studied in recent surface sediments from the entire norwegian greenland sea more than 30 taxa have been recognized of which only few show a distinct distribution pattern and allow description of four assemblages the occurrence of most taxa is related to the relatively warmer waters of the norwegian sea algidaspaeridium minutum s 1 brigantedinium simplex and impagidinium pallidum are the only species showing a preference for colder water masses two species i pallidum and nematosphaeropsis labyrinthus are mainly restricted to the oceanic environment whereas the other species have also been reported from neritic environments in previous studies due to the limited knowledge of the ecological and sedimentological factors influencing the occurrence of dinoflagellate cysts in oceanic environments their distribution in recent sediments can be only related to surface water masses in a broad sense although the distribution of assemblages correlates with specific surface water masses comparison with assemblages recovered from sediment traps deployed basinwide in the norwegian greenland sea dale and dale 1992 revealed some major discrepancies in species composition and percentage abundances the differences cannot be explained with certainty at the moment although there is some evidence that transport of dinoflagellate cysts and other fossilizable microplankton in water masses by currents in sea ice and sediments may modify the assemblages found in recent oceanic surface sediments from the norwegian greenland sea

holocene fluctuations in arctic sea ice cover dinocyst based reconstructions for the eastern chukchi sea cores from site hly0501 05 on the alaskan margin in the eastern chukchi sea were analyzed for their geochemical organic carbon 13corg corg n and caco3 and palynological dinocyst pollen and spores content to document oceanographic changes during the holocene the chronology of the cores was established from 210pb dating of near surface sediments and 14c dating of bivalve shells the sediments span the last 9000 years possibly more but with a gap between the base of the trigger core and top of the piston core sedimentation rates are very high 156 cm ka allowing analyses with a decadal to centennial resolution the data suggest a shift from a dominantly terrigenous to marine input from the early to late holocene dinocyst assemblages are characterized by relatively high concentrations 600 7200 cysts cm3 and high species diversity allowing the use of the modern analogue technique for the reconstruction of sea ice cover summer temperature and salinity results indicate a decrease in sea i

the contribution of alaskan siberian and canadian coastal polynyas to the cold halocline layer of the arctic ocean numerous arctic ocean circulation and geochemical studies suggest that ice growth in polynyas over the alaskan siberian and canadian continental shelves is a source of cold saline water which contributes to the maintenance of the arctic ocean halocline the purpose of this study is to estimate for the 1978 1987 winters the contributions of arctic coastal polynyas to the cold halocline layer of the arctic ocean the study uses a combination of satellite oceanographic and weather data to calculate the brine fluxes from the polynyas then an oceanic box model is used to calculate their contributions to the cold halocline layer of the arctic ocean this study complements and corrects a previous study of dense water production by coastal polynyas in the barents kara and laptev seas recurrent polynyas form on the canadian and alaskan coasts from banks island to the bering strait and on the siberian coast from the bering strait to the new siberian islands in the bering sea polynyas form in norton sound south and west of st lawrence island and in the gulf of anadyr two regions that account for almost 50 of the total dense water production are the siberian coastal polynyas in the adjacent regions of the gulf of anadyr and anadyr strait and the alaskan coastal polynyas which occur along the coast from cape lisburne to point barrow for all of the western arctic coastal regions examined the mean annual total brine flux is 0 5 0 2 sv combination of this flux with the contribution from the barents kara and laptev seas which is recalculated from data in the earlier study shows that over the entire arctic coastal polynyas generate about 0 7 1 2 sv of dense water this compares well with the theoretical estimates of 1 1 5 sv because an unknown fraction of the barents kara and laptev brine flux must go to the eurasian basin deep water the coastal polynyas alone cannot renew the halocline layer other potential brine generation mechanisms include overall freezing on the shelves and the response of the ice to infrequent violent storms for example during february 1982 an intense storm generated a large region of low ice concentration in the eastern chukchi sea over barrow canyon the refreezing of the region was followed by the flow of a dense plume down barrow canyon although the ocean dynamical response to this refreezing needs to be established the possible response of a barrow canyon flow to this refreezing event suggests that the overall refreezing in response to infrequent violent storms may be a potential source of the additional brine needed to maintain the arctic ocean halocline

modern distribution of dinocysts from the north pacific ocean 37 64 n 144 e 148 w in relation to hydrographic conditions sea ice and productivity abstract palynological analyses were performed on 53 surface sediment samples from the north pacific ocean including the bering and okhotsk seas 37 64 n 144 e 148 w in order to document the relationships between the dinocyst distribution and sea surface conditions temperatures salinities primary productivity and sea ice cover samples are characterized by concentrations ranging from 18 to 143 816 cysts cm3 and the occurrence of 32 species a canonical correspondence analysis cca was carried out to determine the relationship between environmental variables and the distribution of dinocyst taxa the first and second axes represent respectively 47 and 17 8 of the canonical variance axis 1 is positively correlated with all parameters except to the sea ice and primary productivity in august which are on the negative side results indicate that the composition of dinocyst assemblages is mostly controlled by temperature and that all environmental variables are correlated together the cca distinguishes 3 groups of dinocysts the heterotrophic taxa the genera impagidinium and spiniferites as well as the cyst of pentapharsodinium dalei and operculodinium centrocarpum five assemblage zones can be distinguished 1 the okhotsk sea zone which is associated to temperate and eutrophic conditions seasonal upwellings and amur river discharges it is characterized by the dominance of o centrocarpum brigantedinium spp and islandinium minutum 2 the western subarctic gyre zone with subpolar and mesotrophic conditions due to the kamchatka current and alaska stream inflows assemblages are dominated by nematosphaeropsis labyrinthus pyxidinopsis reticulata and brigantedinium spp 3 the bering sea zone depicting a subpolar environment influenced by seasonal upwellings and inputs from the anadyr and yukon rivers it is characterized by the dominance of i minutum and brigantedinium spp 4 the alaska gyre zone with temperate conditions and nutrient enriched surface waters which is dominated by n labyrinthus and brigantedinium spp and 5 the kuroshio extension north pacific subarctic current zone characterized by a subtropical and oligotrophic environment which is dominated by o centrocarpum n labyrinthus and warm taxa of the genus impagidinium transfer functions were tested using the modern analog technique mat on the north pacific ocean 359 sites and the entire northern hemisphere databases 1419 sites results confirm that the updated northern hemisphere database is suitable for further paleoenvironmental reconstructions and the best results are obtained for temperatures with an accuracy of 1 7 c

channel morphology and bedload pulses in braided rivers a laboratory study bedload pulses in gravel bed rivers have been widely reported in recent years and attempts have been made to relate them to channel morphology bedload transport and channel morphology were measured in a small scale generic model of braided gravel bed streams two experiments are described in which braided channels developed in a 14 m 3 m sand tray total bedload output from the tray was weighed every 15 minutes stream bed geometry was surveyed every four hours pulses were observed in the bedload output time series and were qualitatively related to the channel morphology immediately upstream of the measuring section the bagnold 1980 bedload equation generally overpredicts measured bedload transport rates when applied to channels that were in equilibrium or aggrading underprediction occurred when applied to degrading channels aggradation was associated with channel multiplication and bar deposition channel pattern simplification occurred when degradation took place and bars emerged from the water flow development of phases of aggradation and degradation is dependent upon the three dimensional geometry of the stream beds spatial and temporal feedback loops can be identified enabling links between channel morphology and bedload transport rate to be directly identified

on the wind driven variability of the flow through bering strait analysis of time series from 1981 to 1982 near bering strait shows the meridional wind component the current and the oceanic pressure gradient to be well correlated we argue that because of the constraining coastal geometry there are wind driven flow divergences which perturb the oceanic pressure field and account for most of the current variability for example northerly winds cause a pronounced set down of sea level southeast of bering strait and if the winds are strong enough they will reverse the mean slope downward to the north through the strait winds during 1976 1977 were also well correlated with the bering strait transport estimates of coachman and aagaard 1981 and we therefore use the calculated winds from 1946 to 1982 to examine the low frequency transport variability there is a marked seasonal cycle with summer transport about 50 greater than during winter the long term mean transport is calculated as less than 0 6 sv which is much lower than earlier estimates abnormally large transports apparently occurred during a number of years from 1948 to 1967 but during the past 15 years transports have tended to be considerably less corresponding to the stronger northerly winds during these years the interannual wind variability near bering strait together with the corresponding variability in the transport through the strait is in fact part of the large scale variability of the atmospheric circulation over the north pacific and its oceanic effects

influence of the st lawrence island polynya upon the bering sea benthos the influence of a polynya a persistent ice free region on water column production and subsequent transport to the shallow continental shelf benthos of the bering sea was evaluated by studying spatial patterns of organic material deposition benthic biomass community sediment metabolism benthic population structure and other potential indicators of enhanced organic carbon transport to benthic communities underlying the st lawrence island polynya despite suggestions that polynyas may be important localized centers of primary production in polar waters we found that the st lawrence island polynya does not obviously enhance the biomass of benthic communities directly below the polynya however southward flowing baroclinic currents generated as a result of brine injection at the polynya edge do appear to have an influence on the biomass and ecological structure of bering sea benthic communities south of st lawrence island these currents appear to affect mean sediment oxygen consumption surface organic carbon nitrogen ratios total organic content and bottom water ammonia by sweeping phytodetrital matter south and to the west of the island a particle reactive short lived natural radioisotope 7be used as an indicator of rapid days to weeks deposition of particulate material from the water column was detected only in surface sediments to the southwest of the island indicating enhancement of particle deposition to the southwest of the island finally the 18o content of tunicate cellulose was highest in the polynya region consistent with increased filter feeding in the late winter when the polynya is present and presumably promoting primary production in the open water the anadyr current consisting of nutrient rich deeper bering sea water that is upwelled onto the shelf in the gulf of anadyr flows west to east in the region south of st lawrence island throughout the year and is the major forcing function for high production in the region the interaction of anadyr water with the winter spring ephemeral polynya and associated baroclinic currents combine to positively influence benthic communities

braided channel pattern and palaeohydrology using an index of total sinuosity abstract channel patterns are commonly represented as discrete types e g straight meandering braided separated by threshold values of slope and discharge however for gravel bed river patterns an index of total sinuosity p can be defined which varies continuously with both stream power per unit channel belt length represented as the product of mean annual flood and valley gradient and median bed material diameter an empirical relationship between p and these controlling variables can be used to provide palaeo hydrological reconstructions for braided stream traces on terrace fragments as an alternative to methods based on bed material sizes and criteria for the threshold of grain motion

surface sediment dinoflagellate cysts from the hudson bay system and their relation to freshwater and nutrient cycling abstract surface sediment samples from the hudson bay system were analysed in order to examine the role of key regulators of arctic marine productivity light and nutrients as affected by freshwater stratification and sea ice cover on the spatial distribution and production of dinoflagellate cysts total cyst fluxes vary from 0 2 10 6 to 30 6 10 6 cysts m 2 a 1 with the highest values observed in eastern hudson bay a total of 24 cyst taxa representing 11 genera of five orders were identified and distribution maps of the most common taxa have been produced this is the first record of echinidinium aculeatum echinidinium karaense cf echinidinium delicatum islandinium brevispinosum selenopemphix quanta cysts of protoperidinium americanum cysts of cf biecheleria sp and polarella glacialis in the hudson bay system dinoflagellate cyst assemblages show distinct spatial patterns revealing three compositional domains eastern hudson bay western central hudson bay and hudson strait the eastern domain is characterised by a dominance of autotrophic cysts of pentapharsodinium dalei whereas the western central domain is characterised by autotrophic operculodinium centrocarpum with some contribution by heterotrophic polykrikos sp var arctic morphotype and polykrikos spp sites from hudson strait are distinguished by an overwhelming prevalence of heterotrophic protoperidiniaceae cysts mainly islandinium minutum and have the highest values of sedimentary biogenic silica used as a proxy for diatom productivity sediment geochemical tracers are used as proxies for freshwater inputs lignin and its biomarkers and nitrate availability nitrogen isotopes and sea ice concentrations derived from passive microwave data as a proxy for light availability sea ice regulated length of the dark season has a negligible influence on the proportion and production of heterotrophic dark adapted versus autotrophic light dependent dinoflagellate cysts perhaps due to the location of our study area on the southern fringe of the arctic instead cyst populations in hudson bay are primarily regulated by vertical stratification and nitrate availability while in hudson strait the pivotal mechanism constitutes food availability

geomorphic effects of a large flood on fluvial fans the response of 12 fluvial fans near sydney australia to a large storm between 2 and 4 february 1990 was determined by repeating previously surveyed longitudinal profiles and by undertaking detailed field observations of erosion and deposition peak rainfall intensities occurred on 3 and 4 february when between 173 and 193 8 mm were recorded return periods for 24 h duration peak rainfall ranged between 5 7 and 11 0 years on the annual maximum series at six stations within the study area and return periods for 48 h peak rainfall ranged between 13 5 and 29 4 years of the 12 fans seven were trenched and five untrenched the most significant geomorphic effects of the storm were recorded on the proximal region of the fans however fan response was highly variable with one fan exhibiting no detectable change three fans localized deposition two fans spatially disjunct erosion and deposition two fans channel avulsions and seven fans fanhead trench reworking some fans exhibited more than one type of response a four stage tentative cyclical model of fanhead development was constructed from the field data stage 1 refers to the episodic aggradation of the fanhead by localized deposition spatially disjunct erosion and deposition and or channel avulsions stage 2 represents the initiation of a fanhead trench when progressive aggradation locally exceeds a threshold slope leading to localized erosion this erosion initially creates one or more discontinuous flow aligned scour pools over time the scour pools widen deepen and extend both up and downfan stage 3 refers to the coalescence of discontinuous scour pools into a continuous trench by the removal of intervening log and boulder steps stage 4 represents the backfilling phase of the trench once it has been overwidened and or slope reduced aggradation then continues as for stage one

late holocene paleoceanography and climate variability over the mackenzie slope beaufort sea canadian arctic abstract late holocene paleoceanography and climate variability of the southeastern beaufort sea canadian arctic have been investigated on the basis of sedimentary cores collected over the mackenzie slope piston trigger and box cores were sampled at station 803 in 2004 aboard the ccgs amundsen at 218 m water depth the chronology of the piston core is constrained by 4 ams 14 c dates as the sedimentation rate in the box core is assessed from 210 pb data we obtain a continuous composite sequence covering the last 4600 years with a sedimentation rate of 140 cm kyr 1 transfer functions modern analogue technique based on dinoflagellate cyst dinocyst assemblages were used to reconstruct the evolution of sea surface conditions over the time period covered by the cores palynological data reveal that dinocyst assemblages are dominated by operculodinium centrocarpum sensu lato mean of 43 3 throughout the core with the accompanying taxa brigantedinium spp 19 6 islandinium minutum 15 6 and cysts of pentapharsodinium dalei 13 7 four zones have been established on the basis of dinocyst relative abundances dinocyst assemblage zone 1 d1 from 4600 to 2700 cal years bp is dominated by o centrocarpum mean of 49 0 in zone d2 2700 1500 cal years bp the relative abundances of o centrocarpum decrease 34 4 in favour of the opportunistic heterotrophic taxa brigantedinium spp 28 8 and cysts of polykrikos sp var arctic quadratus 2 8 dinocyst zone d3 1500 30 cal years bp or 450 1920 ad is characterised by the high relative abundance of the peridinioid taxa i minutum 19 9 the last zone d4 spanning from 1920 to 2004 ad is again dominated by o centrocarpum 44 5 and shows low relative abundances of brigantedinium spp and cf echinidinium karaense quantitative reconstructions of past sea surface parameters august sea surface temperature sst august sea surface salinity sss and duration of sea ice cover indicate relatively stable conditions over the last 4 6 kyr with episodic cooling events sst of 1 5 c below the modern value of 6 c that took place between 700 and 1820 ad we associate the last and the longest of these cooling events 1560 1820 ad with the little ice age reconstructed sss shows decadal oscillations since 1920 ad that we tentatively associate with the accumulation of freshwater by the beaufort gyre and the subsequent great salinity anomalies our data suggest that similar salinity anomalies could have occurred ca 1860 and 1790 ad stable isotopic data show a slight increase in 13 c values from 27 1 at the base to 25 8 at the top over the last 4 6 kyr that we associate with the gradual increase in atmospheric co 2 concentration as recorded by antarctic ice cores variations in the 15 n profile suggest variations in pacific water influence from 4600 to 1300 cal years bp associated with centennial scale shifts of the arctic oscillation phases

paleoenvironments of the strait of georgia british columbia during the last deglaciation microfaunal and microfloral evidence the strait of georgia is situated between vancouver island and the western canadian mainland it was deglaciated quickly around 12 500 14c yr bp by in situ downwasting the subsequent marine invasion has left glacimarine sediments with foraminifers diatoms and dinocysts characterizing successive paleoenvironments recognizable basinwide the first paleoenvironment represents near ice conditions under the influence of the turbid meltwater plume marked by low algal productivity and few foraminifers mostly elphidium excavatum just off the plume the second environment shows a peak of nonionellina labradorica possibly resulting from an observed sudden increase in diatom numbers mostly ice dwelling forms implying a long annual sea ice cover further away cassidulina reniforme increases n labradorica decreases while other calcareous foraminifer species colonize the area there are fewer ice diatoms more marine planktonic diatoms and dinocysts become more abundant finally after 12 000 14c yr bp calcareous foraminifers are gradually replaced because of dissolution of calcium carbonate by a low diversity arenaceous assemblage at the same time abundant planktonic diatoms and dinocysts indicate warmer surface temperature the succession of fossils and environments compares well with modern horizontal off glacier successions observed in fjords of the european arctic

the relationship between flow shear stress and stream pattern based on simple hydraulic reasoning a discharge q slope s diagram for streams is given a physical interpretation permitting the assignment of a relative shear stress value to each stream a sample of 359 streams is used ranging in mean annual discharge from 900 000 to 0 05 ft 3s 1 varying in pattern from highly sinuous p 3 1 to straight and braided sorted according to their relative shear stress values 0 avg streams of high sinuosity p 1 5 are characterized by low relative shear stress median 0 56 which is significantly lower than that characterizing braided streams median 1 70 it is concluded that for natural stream populations the passage from one pattern to another is gradual and the geomorphic thresholds defined by relative shear stress are fuzzy ones

fluvial connectivity and climate a comparison of channel pattern and process in two climatically contrasting fluvial sedimentary systems in south africa abstract the aim of this research was to investigate the dynamics of valley formation sediment delivery and channel pattern in two climatically contrasting fluvial sedimentary systems in south africa each system comprised a network of headwater valley fills and floodplains underlain by sedimentary karoo supergroup rocks that are intersected by resistant dolerite dykes and sills the seekoei river floodplain and gordonville valley fill site in the great karoo however experience less than half the annual precipitation of the nsonge river floodplain and hlatikhulu valley fill in the kwazulu natal drakensberg foothills furthermore rainfall is more variable in the karoo despite climatic differences headwater valley fills were geomorphically similar in contrast floodplains in the two regions were vastly different even when the same downstream control a resistant dolerite intrusion crossing the drainage line was considered upstream of a dolerite dyke the nsonge river is highly sinuous and located in a wide floodplain that has been carved by lateral planation of the underlying bedrock in comparison the seekoei river located upstream of a dolerite sill is discontinuous and characterized by floodouts and avulsing distributaries that undergo periods of bedrock incision followed by infilling it is likely that this disparity is caused by the inability of infrequent unsustained flows to develop meanders and thus adjust the channel planform to changes in discharge sediment load and valley slope flow variability thus exercises a strong control on channel pattern and causes floodouts in headwater settings and the semi arid karoo floodplain as a result sediment transport in the seekoei river is likely to be episodic and net retention of sediment in the semi arid floodplain is greater than in the sub humid nsonge river floodplain where sediment depth is limited

sea surface hydrographical conditions off south faeroes and within the north eastern north atlantic through mis 2 the response of dinocysts the last glacial period showing the progressive development of large boreal ice sheets was punctuated by large climatic excursions these excursions were triggered mainly by atmosphereoceanice coupled dynamics and are thus exemplary case studies of natural climate variability to characterize the sea surface palaeohydrographical changes accompanying these oscillations along the european margin we have integrated new palynological data dinocysts acquired on core md99 2281 60 degrees n faeroe margin during marine isotope stage 2 in a latitudinal transect including published cores md95 2002 47 degrees n celtic margin and md95 2010 66 degrees n voring plateau this transect is superimposed on the modern north atlantic drift pathway but also at the outskirts of glacial european ice sheets thus ideally located to track sea ice extent and ice sheet instabilities through time the results show a coherent and sensitive response of sea surface environments to the complex chain of abrupt events that punctuated the end of the last glacial period the last glacial maximum was marked by large seasonal contrasts of temperatures whereas heinrich events he were characterized by a sharp cooling and sea ice development a tripartite structure is identified within he1 with indices of melting at 19k cal a bp followed by a temperate phase synchronous of a relative stability of ice sheets and a terminal phase 17 515k cal a bp characteristic of the conventional laurentian he1 copyright c 2013 john wiley sons ltd

middle late holocene river terraces in the erhjen river basin southwestern taiwan implications of river response to climate change and active tectonic uplift abstract we reconstruct the holocene river history of the erhjen river area 140 km 2 by correlating river terraces aided by 28 radiocarbon dates multiple terraces developed in the lower erhjen river since the middle holocene they converge downstream to the coastal plain the rates of channel incision into bedrock calculated from these terraces at yuehshihchieh are 7 8 mm year during ca 5 7 2 5 ka 5 cm year during 1 5 1 3 ka and 1 cm year since 1 ka the last is close to the average incision rate since middle holocene meanwhile only a single but wide middle late holocene paleo floodplain was developed in the upper erhjen river it was completely abandoned only after 0 8 ka likely following an episode of base level fall starting from the coastal plain based on the apparent downstream and upstream convergence of these dated terraces we identify a doming structure or anticline within the basin which results in a tilt rate of 10 6 to 10 7 per year in the lower erhjen river valley the major terraces here had different initial long profiles which implies that a critical graded long profile may not be a prerequisite for formation of a wide erosional terrace surface instead we propose that these terraces were initiated by a series of catastrophic rainfall events probably climatic related which brought a large amount of bedload from hillslopes to prevent the channel from incising when valley widening was facilitated by high discharge runoff we find that not only terrace surface formation but also channel incision can be strongly controlled by climatic driven discharge and bedload conditions as suggested by the contrast of bedrock incision rates we observe at yuehshihchieh apparently the climate and its effects on the landscape cannot be regarded as constant during the holocene even in a humid tropical area like taiwan however such a fluctuation of climate could only be recorded in a setting where rivers have a high tendency to incise so that multiple terraces can be created the lower erhjen river that is characterized by active tectonic tilting is an example of this setting

dinoflagellate cysts as indicators of water quality and productivity in british columbia estuarine environments abstract palynological analyses of 60 surface sediment samples from estuarine environments near vancouver island including the georgia strait gs the effingham eff and the seymour belize sb inlets were performed in order to document the distribution of dinoflagellate cyst assemblages and their relationship to hydrographic conditions productivity and nutrient concentrations we tested transfer functions using the analogue method and suggest that dinoflagellate cyst assemblages can be used to reconstruct primary productivity temperature and salinity the eff and sb inlets are characterized by a dominance of autotrophic taxa particularly operculodinium centrocarpum whereas the protoperidinioid and gymnodinial heterotrophic taxa such as quinquecuspis concreta and brigantedinium spp dominate the assemblages of the gs multivariate analysis shows that this distribution is closely linked to primary productivity sea surface temperature sst and spring silica concentration the abundance of autotrophic taxa in the eff and sb inlets is associated with high primary productivity and low summer sst indicating summer upwelling of coastal british columbia whereas the heterotrophic taxa that characterizes the gs assemblages are related to low productivity high summer sst and high silica concentration during spring multivariate analysis shows that the most important environmental parameters related to dinocyst distribution in the restricted embayment of the gs are distance to the shore distance to vancouver harbor spring sea surface salinity sss spring phosphate concentration and spring productivity the autotrophic taxa are generally more common in coastal and shallow waters but spiniferites ramosus and pentapharsodinium dalei show an opposite correlation to spring productivity and salinity p dalei is particularly abundant around vancouver harbor near highly urbanized shores and within the fraser river plume where salinity is low and spring productivity and continental runoff are high s ramosus shows its highest abundance on the western coast of gs protoperidinioid and gymnodinial cysts characterize distal zones within the central and southern gs that are associated with a mixture of brackish waters coming from the fraser river and deep upwelling waters entering the gs via juan de fuca strait the relationship between dinoflagellate cyst assemblages and primary productivity in these estuarine systems differs from that in oceanic and outer neritic zones where the abundance of heterotrophic taxa is commonly associated with upwelling and high productivity

holocene variations of sea surface conditions in the southeastern barents sea reconstructed from dinoflagellate cyst assemblages palynomorphs were analysed in two sediment cores from the southeastern barents sea representing the past 8 3 and 4 4 kyr high dinocyst contents and species diversity enabled the application of the best analogue method to quantitatively reconstruct sea surface salinities temperatures and ice cover using 677 modern reference sites from the north atlantic and arctic seas including new data from the barents sea reported here at the southern core site where waters are affected by the atlantic inflow sea surface conditions were relatively warm and stable between ca 8000 and 5000 calendar yr bp in contrast the past 5 kyr had periods with cooler temperatures and extended ice cover fluctuating mostly at 1 1 5 kyr frequencies at both sites most pronounced coolings occurred around 8 1 5 3 5 3 2 and 2 5 ka the northern site additionally shows younger cooling events tentatively dated to 1 4 0 3 and 0 1 ka identified variations in sea surface conditions indicate changes in atlantic water inputs to the barents sea our results generally correlate to palaeoclimatic reconstructions from northwestern eurasia exemplified by palynological records from karelia this correlation suggests that sea surface variations in the barents sea reflect large scale changes in atmospheric and oceanic interactions between the north atlantic and the arctic copyright 2001 john wiley sons ltd

dinoflagellate cyst assemblages in surface sediments of the laptev sea region arctic ocean and their relationship to hydrographic conditions the occurrence and distribution of dinoflagellate cysts in surface sediments from the laptev sea shelf and the adjacent continental margin has been studied in relation to surface water conditions assemblages were interpreted by visual inspection and q mode factor analysis the inner laptev shelf is a type area for polar environments because of near absence of relatively warm waters from the pacific or atlantic oceans and an extensive seasonal sea ice cover assemblages are of low diversity and are dominated by the cold water taxon islandinium minutum and related morphotypes the common occurrence of distinctive polykrikoid cyst morphotypes is an indicator of polar environments furthermore strong supply of freshwater in summer influences the surface water conditions and is a major factor controlling the occurrence and distribution of dinoflagellate cysts the dinoflagellate cysts nematosphaeropsis labyrinthus and operculodinium centrocarpum are restricted to the continental margin suggesting a relation to the inflow of relatively warm atlantic waters along the eurasian continental margin an abundance maximum of brigantedinium spp at the shelf break is related to the mean position of the marginal ice zone

multi channel patterns of bedrock rivers an example from the central narmada basin india abstract an anomalous multiple channel pattern in bedrock is observed on a predominantly downcutting reach of the narmada river the multi channel reach 800 2750 m in width and 8500 m in length is bounded by major faults and is underlain by granite and gneiss bedrock geomorphological investigations reveal differences among the upstream middle and downstream sub reaches of the multi channel study area whereas the upstream sub reach is dominated by deep flows and fine sediments the lower sub reach is characterized by a steep gradient and rapids the middle sub reach is the widest and is marked by thickly forested islands and boulder berms the characteristics of the three different sub reaches suggest control by the interactions of lithology flood processes and tectonics estimations of hack s 1973 stream gradient index values indicate considerable variations for the sl values along the length of narmada river the highest value of gradient index sl 797 is associated with the multi channel reach implying lithologic or tectonic control given the dimensions of the reach and its channels it appears that the present hydrological regime is inadequate to produce the feature we hypothesize that the multi channel pattern development in bedrock was initiated by block or domal uplift enhanced gradients and extreme floods permitted the system to exploit linear weaknesses in the bedrock leading to the development of anabranches and establishment of multiple channels in bedrock abrupt changes in the channel planform and morphology at the study site indicate that the river is adjusting its channel geometry width depth gradient and plan configuration to a new equilibrium channel morphology through the action of the extreme floods characteristic of this fluvial environment

physical properties of shale at temperature and pressure deformational properties p wave and s wave velocities and electrical resistivity were measured for three north sea malm shales in the laboratory under pressures to 800 bars and temperatures to 100 c these data were used to evaluate how factors such as mineralogy microstructure compaction and pore fluid conductivity affect a shale s seismic and electrical responses deformation in the shales is dominated by inelastic processes which cause time dependent changes in velocity resistivity and pore pressure overall shales are less sensitive to pressure changes as compared to sandstones of similar porosity however changes in temperature result in large changes in physical properties as compared to sandstones or shaly sands p wave and s wave velocities may decrease by as much as 10 percent over the temperature range studied and calculated activation energies for surface conduction are nearly twice those observed in shaly sands these comparisons emphasize fundamental differences in fabric among the

middle late holocene palynology and marine mollusks from archipielago cormoranes area beagle channel southern tierra del fuego argentina abstract the palynology and marine mollusks of a marine sequence from rio ovando 54 51 s 68 35 w archipielago cormoranes beagle channel has been studied in order to reconstruct paleoenvironmental conditions during the middle late holocene the dinoflagellate cyst assemblages from rio ovando sequence reflect fjord estuarine environments close to terrestrial ice field affected by glacier meltwater discharge and characterized by short term oscillations of sea surface water parameters the base of the section which is dated at about ca 4160 14 c yr b p 4736 cal yr b p palynological subzone ro 2c is characterized by a high species diversity of dinocyst and mollusks and it is immediately followed by an interval palynological subzone ro 2b characterized by the presence of the echinidinium islandinium complex and the monospecific mytilus mollusk assemblage this subzone registers an inverse correlation between nothofagus dombeyi type and echinidinium islandinium complex concentration values during ca 4160 14 c yr b p 4736 cal yr b p 4064 14 c yr b p 4540 cal yr b p suggesting a variable climatic condition probably related to neoglacial episodes occurred in the southern patagonia andes during this interval the pollen assemblages permit direct correlations with the onshore palynostratigraphy from southern of tierra del fuego the high percentages of nothofagus dombeyi type recorded throughout most of the profile strongly suggest the presence of a closed forest confirming the existence of a variable cool and wet climate for the archipielago cormoranes area during the middle late holocene

northward flow in the bering and chukchi seas the ocean circulation on the bering and chukchi sea shelves is investigated using a barotropic numerical model in the presence of the winter seasonal wind stress from the northeast observed northward transport through bering strait of 0 6 sv for the 8 month winter season 1981 1982 can be driven by a sea level difference of 0 4 m between the pacific and arctic oceans this sea level difference between basins is in agreement with hydrographic estimates in the absence of wind stress a 0 4 m sea level difference drives a northward transport through bering strait of 1 1 sv maximum transport through bering strait is geostrophically limited not frictionally or inertially limited major qualitative circulation features of the region are evident in the simulations westward intensification of the northward transport across the bering sea shelf is confirmed with the major transport occurring in the relatively deep gulf of anadyr in the absence of wind anadyr strait contributes 72 of the northward transport through bering strait with northeasterly winds there is a net clockwise circulation around saint lawrence island within the 20 m isobath norton and kotzebue sounds are little influenced by the general circulation northward transport in the chukchi sea bifurcates in the vicinity of point hope the predominant branch is directed toward the northwest in a broad canyon feature south of herald shoal and the balance becomes the alaskan coastal current between cape lisburne and point barrow

distribution of dinoflagellate cysts in the canadian arctic marine region the canadian arctic is a major gateway for transport of freshwater from the arctic ocean to the north atlantic this region comprises the beaufort sea the canadian arctic archipelago caa and northern sections of baffin and hudson bays subregional differences include major freshwater runoff to the beaufort sea and hudson bay presence of pacific and atlantic intermediate water in the west and atlantic water in baffin and hudson bays principal component analysis of 50 core top samples shows four subregional dinoflagellate cyst assemblages outer beaufort shelf assemblage i is co dominated by operculodinium centrocarpum s l and brigantedinium spp with minor cysts of pentapharsodinium dalei algidasphaeridium minutum s l and cysts of polykrikos spp assemblage ii in the canadian arctic archipelago is co dominated by brigantedinium spp a minutum s l and cysts of polykrikos spp including two arctic morphotypes assemblage iii in the north water polynya exclusively comprises a minutum s l and brigantedinium spp assemblage iv in baffin bay is dominated by o centrocarpum s l and spiniferites spp with brigantedinium spp on the shelves the ratio of gonyaulacoid to protoperidinioid cysts g p generally decreases with increased sea ice cover but it may also decrease in river plumes and in polynyas copyright 2001 john wiley sons ltd journal of quaternary science

contribution palynostratigraphique dinokystes pollen et spores a la connaissance de la mer de champlain coupe de saint cesaire quebec high resolution continental pollen and spores and marine dinoflagellate cysts microfloral records were obtained from a section consisting of about 0 5 m of glaciolacustrine and 2 5 m of champlain sea deposits at the saint cesaire site the pollen and spore assemblages indicate the existence of a regional open vegetation of shrub tundra to forest tundra fluctuations in the percentages of picea and shrub and herb taxa are related to regional afforestation and paleogeographical evolution of the basin the champlain sea sediments contain an abundant dinocyst flora dominated by operculodinium centrocarpum brigantedinium spp and algidasphaeridium minutum which indicate cold arctic conditions in surface waters fluctuations in concentration 102 104 cm 3 and relative abundance of dinocyst species are attributed to changes in dinoflagellate productivity and paleoceanographic conditions notably paleosalinity morphological variations of operculodinium centrocarpum and algidasphaeridium minutum led to

palynofacies analysis and organic walled dinoflagellate cysts as indicators of palaeo hydrographic changes an example from holocene sediments in skalafjord faroe islands abstract this study documents holocene variations in organic matter deposition from ca 6350 cal yr bc to ad 1430 in skalafjord faroe islands and uses this information to assess palaeo hydrographic conditions the chronology of the interval studied is based on five ams 14 c ages based on the total sedimentary organic content the sediments dating to ca 6350 cal yr bc to ad 160 have been deposited under dysoxic bottom water conditions suggesting good ventilation in the water column the sediments dating to ca ad 160 1090 have been deposited under decreasing oxygen availability from ad 1090 to 1430 suboxic bottom water conditions characterised the fjord high terrestrial influx characterised most sediments in the study interval however moderate terrestrial influx was recorded in sediments dating to ca 6350 5670 cal yr bc based on the dinoflagellate cyst assemblages changes in the nutrient availability were inferred in the waters of the fjord over the study period the nutrients were minimal at ca 6350 5670 cal yr bc they increased in the interval ca 5670 685 cal yr bc and became very abundant at ca 685 cal yr bc to ad 1260 a decreasing trend in nutrient availability was inferred in sediments of age ca ad 1260 1430 a qualitative approach was used for the reconstruction of holocene sea surface temperature conditions based on dinoflagellate cyst and acritarch assemblages the estimated sea surface parameters highlighted the mid holocene final stage of the climatic optimum ca 6350 5300 cal yr bc the neo glaciation period ca 5300 cal yr bc to ad 260 a general climatic amelioration during the period ca ad 260 1090 and a cooling at ca ad 1090 1260

effects of el nino southern oscillation and north pacific weather patterns on interannual variability in the subarctic bering sea extraordinary interannual variability in ice cover air and sea surface temperatures sst and surface winds in the eastern bering sea have been observed over recent years to investigate the causes of this interannual variability long term 20 30 years time series of air ocean and ice parameters from the bering sea were cross correlated with the southern oscillation index soi an index of el nino southern oscillation enso events in the tropical southern hemisphere as well as with an index of pacific north american pna events in the north pacific five to thirty percent of the interannual variability linear regression with various smoothing in the bering sea data sets with the exception of surface winds is explained by the soi when the bering sea data lags the soi for comparison 29 52 of the variability in the sst off south america can be explained by the soi the signs of the correlations all suggest that warming in the bering sea follows negative anomalies in the soi that is enso events positive anomalies in the soi which tend to precede el nino events were found to precede cooling in the bering sea significant correlation persists for 18 20 months higher order polynomial regressions between the soi and bering sea data can explain up to 40 of the bering sea variability the mechanism for the connection between enso events and bering sea interannual variability appears to be of atmospheric nature and is associated with the winter position and intensity of the aleutian low the aleutian low is intensified and eastward of normal in association with el nino i e warm events but is weaker and westward of normal during cool events it is the regional winds associated with the variable position of the aleutian low that cause the regional warming and cooling events this seesaw in the aleutian low is also used to explain the out of phase ice conditions between the bering sea and the sea of okhotsk pna events are also associated with an intensified aleutian low as well as 700 mbar ridging over northwestern north america causing southerly flow over alaska however while correlation between enso events and pna was significant the correlation between the bering sea and pna was marginal except for surface winds here surface winds from the north were significantly correlated with the pna this apparent inconsistency as well as the lack of correlation of surface winds with the soi is explained by the lack of preferred site of the aleutian low during enso events this lack of preferred site helps explain why the major el nino event of 1982 1983 had little apparent effect on the bering sea

distribution of common modern dinoflagellate cyst taxa in surface sediments of the northern hemisphere in relation to environmental parameters the new n 1968 database abstract we present a new version of the standardized northern hemisphere modern dinoflagellate cyst dinocyst database which includes abundances of 71 taxa at 1968 sites across the northern hemisphere cross referenced with 17 environmental parameters extracted mostly from the 2013 world ocean atlas several taxa with tropical to warm temperate affinities were added to the previous database version dinocyst concentrations in the surface sediments reach 106 cysts g 1 with maximum values along the continental margins and minimum values offshore in distal open ocean settings assemblages are characterized by the co occurrence of phototrophic n 41 and heterotrophic taxa n 30 with maximum proportions of heterotrophic taxa in high productivity regions notably at the sea ice edge and in upwelling regions the main pattern of assemblage distributions includes north south and nearshore offshore gradients with maximum diversity of species along the continental margins and towards the south in warm temperate and tropical areas canonical correspondence analyses performed on heterotrophic and phototrophic taxa independently yield consistent results hence suggesting similar but not identical ecological affinities for both taxonomic groups for both groups sea surface temperature and sea ice are the most determining parameters but the phototrophic taxa seem more sensitive to onshore offshore gradients marked by salinity changes productivity related parameters also determine dinocyst distribution especially primary productivity in the fall and winter with a stronger relationship for the combined dataset of phototrophic and heterotrophic taxa

modern dinoflagellate cyst assemblages in surface sediments of nunatsiavut fjords labrador canada abstract in order to document long term climate cycles and predict future climate trends for the arctic geological records archived in ocean sediments can help establish the link between historical and pre historical sea surface parameters dinoflagellate cysts dinocysts are used as proxy indicators of sea surface parameters temperature salinity sea ice cover primary productivity jointly with transfer functions and a modern dinocyst reference database to reconstruct the evolution of sea surface conditions at decadal and millennial timescales here we present the surface distribution of recent dinocyst assemblages in 13 surface samples collected in four nunatsiavut fjords northern labrador canada along a latitudinal gradient and their relationship with various environmental and biological parameters dinocyst concentrations in surface sediments increased from the inner to the outer part of each fjord and also from the northernmost to the southernmost fjords there was also a southward increase in the species diversity with an occurrence and a dominance of cysts from autotrophic dinoflagellates the presence of cysts of the calcareous dinoflagellate species scrippsiella cf s crystallina in anaktalak fjord where mining activities are underway appears to be an indicator of human related pollution within the fjord

energy expenditure and geomorphic work of the cataclysmic missoula flooding in the columbia river ggorge usa cataclysmic releases from the glacially dammed lake missoula producing exceptionally large floods have resulted in significant erosional processes occurring over relatively short time spans erosional landforms produced by the cataclysmic missoula floods appear to follow a temporal sequence in many areas of eastern washington state this study has focused on the sequence observed between celilo and the john day river where the erosional features can be physically quantified in terms of stream power and geomorphic work the step backwater calculations in conjunction with the geologic evidence of maximum flow stages indicate a peak discharge for the largest missoula flood of 10 10 6 m 3 s 1 the analysis of local flow hydraulics and its spatial variation were obtained calculating the hydrodynamic variables within the different segments of a cross section the nature and patterns of erosional features left by the floods are controlled by the local hydraulic variations therefore the association of local hydraulic parameters with erosional and depositional flood features was critical in understanding landform development and geomorphic processes the critical stream power required to initiate erosion varied for the different landforms of the erosional sequence ranging from 500 w m 2 for the streamlined hills up to 4500 w m 2 to initiate processes producing inner channels erosion is possible only during catastrophic floods exceeding those thresholds of stream power below which no work is expended in erosion in fact despite the multiple outbursts which occurred during the late pleistocene only a few of them had the required magnitude to overcome the threshold conditions and accomplish significant geomorphic work 1997 by john wiley sons ltd

laws place history and the interpretation of landforms the state of an earth surface system ess is determined by three sets of factors laws place and history laws l l1 l2 ln are the n general principles applicable to any such system at any time place factors p p1 p2 pm are the m relevant characteristics of the local or regional environment history factors h h1 h2 hq include the previous evolutionary pathway of the ess its stage of development past disturbance and initial conditions geoscience investigation may focus on laws place or history but ultimately all three are necessary to understand and explain ess the lph triad is useful as a pedagogical device illustrated here via application to explaining the world s longest cave mammoth cave ky beyond providing a useful checklist the lph framework provides analytical traction to some difficult research problems for example studies of the avulsions of three southeast texas rivers showed substantial differences in avulsion regimes and resulting alluvial morphology despite the proximity and superficial similarity of the systems avulsions are governed by the same laws in all cases l a l b l c and the three rivers have undergone the same sea level climate and tectonic histories as well as the same general anthropic impacts h a h b h c though regional environmental controls are similar local details such as the location of the modern main channel relative to pleistocene meander channels differ and thus these place factors explain the differences between the rivers the lph framework or similar types of reasoning is implicit in many types of geoscience analysis explicit attention to the triad can help solve or address many specific problems and remind us of the importance of all three sets of factors copyright 2016 john wiley sons ltd

palynological evidence of holocene climate change in the eastern arctic a possible shift in the arctic oscillation at the millennial time scalethis article is one of a series of papers published in this special issue on the theme polar climate stability network dinocyst assemblages and the physical properties of two sediment cores collected in the easternmost part of the main axis of the northwest passage canadian arctic ocean cores 2004 804 009 bc and 2004 804 009 pc 74 11 2 n 81 11 7 w were used to reconstruct changes in sea surface conditions and to characterize changes in the depositional environment core 2004 804 009 pc spans the last 12 180 calibrated cal years bp with sedimentation rates ranging from 45 to 122 cm ka quantitative estimates of sea surface parameters reveal relatively large hydrographic variability at millennial time scale before 11 000 cal years bp our records suggest terrigenous inputs related to the last deglaciation between 11 000 and 9600 cal years bp harsh conditions prevailed with august sea surface temperatures 2 c and the dominance of heterotrophic taxa this episode was followed by a gradual increase in the relative abundance of phototrophic taxa and the establishment of milder condition with sea surface temperature

mechanisms forcing abrupt fluctuations of the indian ocean summer monsoon during the last deglaciation abstract a piston core from the somali upwelling area has been studied at high resolution for its dinoflagellate cyst content variations in cyst association are inferred to reflect changes in indian ocean summer monsoon intensity several abrupt fluctuations in monsoon intensity are detected for the interval between 20 and 10 ka bp comparison of these fluctuations with changes in contrast between 30 n and 30 s july insolation and the 18 o grip ice core values suggests that different mechanisms influenced monsoon intensity at different time intervals a general trend in monsoon intensity follows variations in insolation contrast lagging minimum contrast by 7 5 ka and maximum contrast by 4 ka this phase lag difference can be explained by assuming the existence of an ice snow cover over central asia tibet during glacial times between 18 7 and 12 5 ka bp fluctuations in sw monsoon intensity may be forced by variations in the thermohaline ocean circulation a rapid transition towards strong sw monsoons at 12 5 ka bp is possibly the result of variations in atmospheric circulation and melting of the snow ice fields in central asia tibet variations in glacial interglacial boundary conditions related to temperature change at northern latitudes are likely to have influenced sw monsoon intensity between 12 5 and 10 ka bp whereas after 10 ka bp variations in tropical land surface boundary conditions may be the dominant forcing factor 0 1997 elsevier science ltd all rights reserved

dinoflagellate cyst distribution in marine surface sediments off west africa 17 6 n in relation to sea surface conditions freshwater input and seasonal coastal upwelling abstract an organic walled dinoflagellate cyst analysis was carried out on 53 surface sediment samples from west africa 17 6 n to obtain insight in the relationship between their spatial distribution and hydrological conditions in the upper water column as well as marine productivity in the study area multivariate analysis of the dinoflagellate cyst relative abundances and environmental parameters of the water column shows that sea surface temperature salinity marine productivity and bottom water oxygen are the factors that relate significantly to the distribution patterns of individual species in the region the composition of cyst assemblages and dinoflagellate cyst concentrations allows the identification of four hydrographic regimes 1 the northern regime between 17 and 14 n characterized by high productivity associated with seasonal coastal upwelling 2 the southern regime between 12 and 6 n associated with high nutrient waters influenced by river discharge 3 the intermediate regime between 14 and 12 n influenced mainly by seasonal coastal upwelling additionally associated with fluvial input of terrestrial nutrients and 4 the offshore regime characterized by low chlorophyll a concentrations in upper waters and high bottom water oxygen concentrations our data show that cysts of polykrikos kofoidii selenopemphix quanta dubridinium spp echinidinium species cysts of protoperidinium monospinum and spiniferites pachydermus are the best proxies to reconstruct the boundary between the ne trade winds and the monsoon winds in the subtropical eastern atlantic ocean the association of bitectatodinium spongium lejeunecysta oliva quinquecuspis concreta selenopemphix nephroides trinovantedinium applanatum can be used to reconstruct past river outflow variations within this region

fault location by channel wave seismology in united kingdom coal seams about 80 percent of british deep mined coal is obtained from advance longwall faces this mining method is highly capital intensive therefore it is important to know the geologic structure prior to mining small faults can have a large effect on production rates channel wave seismology offers a possible method for locating these faults a coal seam resembles a dispersive acoustic duct and energy from a seismic source within the seam can be coupled into channel wave modes scattered waves from defects within the seam can be recorded and the data analyzed to produce a map of the seam it has been shown that dispersion does not present a fundamental limitation to the resolution that can be obtained in addition broadband numerical holographic mapping procedures in the form of lag sums can be implemented these techniques have been described previously by mason et al 1980a this paper is divided into two main parts first we show how the basic lag sum techniques have been extended to produce an adapt