productivity regime and phytoplankton size structure in the arabian sea abstract the productivity regime and size structure of phytoplankton are described for three different epipelagic systems in the arabian sea during the inter monsoon period in spring 1987 1 the coast of oman 2 the central arabian sea and 3 the shelf off pakistan these results are related to the functioning of the specific ecosystem off the coast of oman the transition from a surface maximum of autotrophic biomass and production to a more oligotrophic system with a chlorophyll subsurface maximum was observed concomitantly the size spectrum changed towards a higher significance of picoplankton in the central arabian sea a typical oligotrophic system with a pronounced subsurface maximum of autotrophic biomass and primary production was encountered here the epipelagic system could be divided into two distinct sub systems the surface layer regenerated production the predominance of picophytoplankton and minor losses due to sedimentation thus a closed system and the subsurface maximum layer at the nutricline characterized by higher sedimentation losses and more diatoms both sub systems showed about the same productivity the turnover in the surface layer having been much greater than in the subsurface maximum the system on the shelf off pakistan is seen as a decay stage of the open ocean system when water from offshore is transported onto the shelf during the onset of monsoon winds

dinoflagellate cyst based modern analogue technique at test a 300 year record from the gulf of taranto eastern mediterranean abstract to test the performance of dinoflagellate cyst based palaeoenvironmental reconstructions derived via the modern analogue technique mat and a non quantitative method we have compared reconstructions of mixed layer temperature sea surface temperature and mixed layer salinity of a well dated site from the gulf of taranto to instrumental data of air temperature precipitation and river discharge two hypotheses are tested the reconstructions of dinoflagellate cyst based mat improve when a a local reference dataset rather than an extra regional reference dataset is used b the reference and downcore datasets are corrected for species specific preservation prior to analysis this is achieved by executing four experiments based on different reference datasets 1 a north atlantic dataset including all species 2 a north atlantic dataset including degradation resistant species 3 a mediterranean dataset including all species 4 a mediterranean dataset including degradation resistant species only we show that mat based reconstructions improve when a local rather than an extra regional reference dataset is used exclusively including species resistant to degradation improves the reconstruction if an extra regional reference dataset is used but leads to considerable loss of variability if the local reference dataset is used both mat based and qualitative reconstructions correlate to instrumental data for industrial times for pre industrial times mat reconstructions of variability in temperature and salinity do not co vary with variability in the instrumental data whereas qualitative reconstructions provide a relatively good fit we suggest this to be a result of the anthropogenic influence on coastal marine ecosystems existing today at the majority of the coastal sample sites in the reference dataset as a result conditions at these sites do not correspond to pre industrial conditions we advise users of dinoflagellate cyst transfer functions to pay more attention to this aspect

instability conditions of loose sand in plane strain when a loose sand specimen is loaded under an undrained condition it may become unstable the instability conditions may be specified by an instability line determined using undrained tests however the instability behavior of sand has seldom been studied under plane strain conditions experimental data obtained under both triaxial and plane strain conditions are presented in this paper to define the instability conditions of loose sand under plane strain conditions using the state parameter a unified relationship can be established between the normalized slope of instability line and the state parameters for both axisymmetric and plane strain conditions using this relationship the instability conditions established under axisymmetric conditions can also be used for plane strain conditions

short term climate variability during roman classical period in the eastern mediterranean abstract to obtain insight into character and potential forcing of short term climatic and oceanographic variability in the southern italian region during the roman classical period 60 bc ad 200 climatic and environmental reconstructions based on a dinoflagelate cyst record from a well dated site in the gulf of taranto located at the distal end of the po river discharge plume have been established with high temporal resolution short term fluctuations in accumulation rates of the adriatic surface water species lingulodinium machaerophorum the freshwater algae concentricystes and species resistant to aerobic degradation indicate that fluctuations in the trophic state of the upper waters are related to river discharge of northern and eastern italian rivers which in turn are strongly related to precipitation in italy the dinoflagellate cyst association indicates that local sea surface temperatures which in this region are strongly linked to local air temperatures were slightly higher than today we reconstruct that sea surface temperatures have been relatively high and stable between 60 bc ad 90 and show a decreasing trend after ad 90 fluctuations in temperature and river discharge rates have a strong cyclic character with main cyclicities of 7 8 and 11 years we argue that these cycles are related to variations of the north atlantic oscillation climate mode a strong correlation is observed with global variation in 14c anomalies suggesting that solar variability might be one of the major forcings of the regional climate apart from cyclic climate variability we observed a good correlation between non cyclic temperature drops and global volcanic activity indicating that the latter forms an additional major forcing factor of the southern italian climate during the roman classical period

size fractionated primary production and nitrogen assimilation in the northwestern indian ocean abstract rates of phytoplankton production and nitrogen assimilation were measured at various stations along a transect in the northwestern indian ocean from near the equator northwards into the upwelling system off the arabian peninsula during september october 1986 the measurements were made using in situ incubation techniques with the simultaneous use of 14c and 15n isotopes samples were fractionated after the incubations into three size classes 0 2 0 8 m 0 8 5 0 m and 5 0 m for the 14c incubations and 5 m for the 15n incubations the assimilation of nitrate and ammonium was measured these measurements were supported by a detailed description of the horizontal and vertical distributions of chlorophyll temperature and underwater light field by the deployment of a towed undulating oceanographic recorder rates of primary production ranged from approximately 0 5 g c m 2 day 1 at the equator reducing to 2 5 in the upwelling region off the coast of oman total nitrogen assimilation followed a similar pattern very significant variations in the size distribution of the activity of the plankton were observed over 75 of the carbon and nitrogen assimilation was in the

miocene and pliocene sandstone petrofacies of the northern albuquerque basin new mexico and implications for evolution of the rio grande rift abstract sand stone petrofacies are an essential element in paleogeographic and paleotectonic reconstruction of nonmarine basins such as those of the rio grande rift the miocene pliocene santa fe group of the northern albuquerque basin records development of the rio grande rift the santa fe group consists of alluvial lacustrine and eolian deposits three lithostratigraphic units from oldest to youngest the zia middle red and ceja are petrologically indistinguishable and therefore are all part of the albuquerque petrofacies qfl 53 26 21 also present is a locally derived volcanic hypabyssal petrofacies sandstone composition and regional relations indicate that most of the albuquerque petrofacies is the distal equivalent of miocene petrofacies of the espanola basin and southern tusas mountains equivalence of petrofacies in the two basins supports a hypothesis for two stage development of the rio grande rift during middle to late miocene time the two basins were connected to form one enlarged espanola basin an irregular west tilted half graben formed by high angle faulting on reactivated laramide structures in the latest miocene movement began on the embudo pajarito la bajada san francisco rincon fault system and the sandia mountains rose rapidly in the process the northern albuquerque basin reversed its half graben tilt from westward as the southern part of the miocene espa ola basin to eastward the modern albuquerque basin the modern albuquerque basin bears little resemblance to its miocene counterpart

evolution of productivity and monsoonal dynamics in the eastern arabian sea during the past 68ka using dinoflagellate cyst records for the first time here we report the dinoflagellate cyst assemblage response to the monsoon variability over the last 68 ka from the eastern arabian sea eas based on the cyst assemblage five dinoflagellate cyst zones were established corresponding to four marine isotopic stages mis 1 4 an increased abundance of autotrophic gonyaulacoid species especially spiniferites during glacials mis 2 and 4 and late mis 3 41 67 to 25 3 ka reflects high productivity driven by strong winter convection during the northeast monsoon in contrast their decreased abundance during mis 1 and early mis 3 58 6 to 42 87 ka reveals decrease in productivity due to strong stratification caused by intense monsoon precipitation induced runoff from the western ghats and reduced light penetration driven by cloud cover the variation in heterotrophic protoperidinium species abundance could be related to variation in the oxygen minimum zone omz intensity with better preservation during intense omz in mis 3 and the late holocene 3 ka onwards therefore it is proposed here that the abundance of protoperidinium can be used as an index of omz in the eas

fluxes of planktic foraminifera in response to monsoonal upwelling on the somalia basin margin abstract sediment trap samples collected off somalia bi weekly from early june 1992 through mid february 1993 show large seasonal variations in the shell flux and species composition of planktic foraminifera these variations mirror the monsoon driven circulation which resulted in massive upwelling and offshore eddy transport in summer during the sw monsoon june september and accounted for nearly 90 of the estimated annual shell flux of planktic foraminifera g bulloides dominated the sw monsoon along with g glutinata t quinqueloba n dutertrei and t iota in a fauna rich species but with a low diversity and equitability during the autumn intermonsoon november december the ocean became stratified and the nutrient exhausted whereas during the ne monsoon january march a warm surface mixed layer developed with the nutrients entrained by deep wind mixing it was dominated by g ruber in association with g tenella g aequilateralis g trilobus g sacculifer and g menardii in a fauna poorer in species but with a higher diversity and equitability consequently the ratio in the abundance of g bulloides and g ruber follows the monsoonal cycle closely as both species persist throughout the year only the rare g theyeri seems to be restricted to the sw monsoon in october at the end of the sw monsoon the trap at 265 m above the bottom intercepted massive amounts of fine grained carbonate m resuspended from the shelf and upper slope it contained extreme fluxes of bioclastic fragments benthic foraminifera and benthic ostracods as well as enhanced fluxes of small sized planktic foraminifera m notably g rubescens integrated over the year the species composition intercepted by the trap shows a very good match with the shell fauna in a core top sediment from the same site apparently the year estimated monsoonal record of planktic foraminifera which is strongly dominated by the sw monsoon production survives burial intact consequently the species composition of planktic foraminifera and measures such as the bulloides ruber ratio can be applied as a proxy for past changes in the intensity of the sw monsoon off somalia compared to the modern condition

the phytoplankton bloom in the northwestern arabian sea during the southwest monsoon of 1979 the biological variability of the northwestern arabian sea during the 1979 southwest monsoon has been investigated by the synthesis of satellite ocean color remote sensing with analysis of in situ hydrographic and meteorological data sets and the results of wind driven modeling of upper ocean circulation the phytoplankton bloom in the northwestern arabian sea peaked during august september extended from the oman coast to about 65 e and lagged the development of open sea upwelling by at least 1 month in total the pigment distributions hydrographic data and model results all suggest that the bloom was driven by spatially distinct upward nutrient fluxes to the euphotic zone forced by the physical processes of coastal upwelling and offshore ekman pumping coastal upwelling was evident from may through september yielded the most extreme concentrations of phytoplankton biomass and along the arabian coast was limited to the continental shelf in the promotion of high concentrations of phytoplankton upward ekman pumping to the northwest of the somali jet axis stimulated the development of a broad open sea phytoplankton bloom oceanward of the oman shelf vertical mixing during the 1979 southwest monsoon was apparently not a primary cause of the regional scale phytoplankton bloom

ocean atmosphere responses to climatic change in the labrador sea pleistocene plankton and pollen records abstract pleistocene climate change is examined using proxy climatic records from oxygen isotope data calcareous and organic walled marine microfossils pollen and terrestrial spores deposited during the past 0 9 ma at odp site 646 in the labrador sea 500 km north of the present polar front paleotransfer functions applied to planktonic foraminiferal assemblages show relative increases in interglacial summer 3 7 and winter 3 5 temperatures and in winter salinity 0 5 2 for the past 0 4 ma but only two earlier intervals early stage 11 and stage 17 have changes of comparable magnitude coccolith and dinoflagellate cyst accumulation rates show that primary productivity is generally correlated with temperature and salinity changes at the start of interglacials these productivity peaks lag the ice volume changes by 2 4 ka dinocyst blooms seem to precede coccolith peaks reflecting the tolerance of opportunistic species for large variations in temperature and salinity peaks in pollen and spore abundance are strongly correlated with ice volume which controls the position and stability of the polar jet stream in addition to the northern extent of forest vegetation time series analysis was made of 7 oceanographic variables sst summer and winter surface salinity coccoliths dinocysts planktonic and benthic foraminifera and 5 other variables 18 pollen spores percent sand foraminiferal test fragmentation and reworked palynomorphs most variables showed significant power peaks at 100 ka and or at 41 ka however sea surface responses showed minor peaks at 26 and 16 ka and microfossil productivity also showed significant peaks at 68 ka the high latitude labrador sea records thus display large non linear regional responses to climate changes in addition to the effects of orbital insolation forcing at 41 and 23 ka

dinoflagellate cysts from sediment traps deployed in the bellingshausen weddell and scotia seas antarctica dinoflagellate cysts have been recovered from six long term 1 2 yr sediment trap moorings deployed in the bellingshausen weddell and scotia seas antarctica these traps mostly moored near the sea bed to sample the nepheloid layer were located both within and to the north of the maximum sea ice limit the numbers of cysts together with the composition of the assemblages reinforce the importance of the maximum sea ice limit as a modern biogeographic boundary for the distribution of dinoflagellate cysts cysts derived from heterotrophic dinoflagellates make up the highest proportions within the assemblages recovered from the traps one trap sampled the export production revealing little difference in cyst flux over those sampling the nepheloid layer cyst flux appears to be highest in areas closest to the antarctic convergence north of the maximum sea ice limit and to high nutrient availability there are however differences between the sediment trap assemblages and those recovered from core top samples at the same or nearby sites these differences in the greater number of cysts and in the higher numbers of round brown protoperidinium cysts in the traps may reflect annual differences in the primary productivity and or cyst production in the area in some areas the sediment record may preserve little information about local surface water productivity because of the activity of bottom water currents for example those arising from the antarctic circumpolar current

critical state based interpretation of the monotonic behavior of hostun sand abstracta series of bender element tests and drained and undrained monotonic triaxial compression and extension tests were performed on air pluviated samples of hostun sand samples were prepared t

atlas of modern dinoflagellate cyst distributions in the black sea corridor from aegean to aral seas including marmara black azov and caspian seas abstract we present the first comprehensive taxonomic and environmental study of dinoflagellate cysts in 185 surface sediment samples from the black sea corridor bsc which is a series of marine basins extending from the aegean to the aral seas including marmara black azov and caspian seas for decades these low salinity semi enclosed or endorheic basins have experienced large scale changes because of intensive agriculture and industrialisation with consequent eutrophication and increased algal blooms the bsc atlas data provide a baseline for improved understanding of linkages between surface water conditions and dinoflagellate cyst dinocyst distribution diversity and morphological variations by cross reference to dinocyst occurrences in sediment cores with radiocarbon ages covering the past c 11 700 years the history of recent biodiversity changes can be evaluated the seabed cyst samples integrate seasonal and multi year data which are not usually captured by plankton samples and the cyst composition can point to presence of previously unrecorded motile dinoflagellate species in the bsc results show the presence of at least 71 dinocyst taxa of which 36 can be related to motile stages recorded in the plankton comparison with sediment core records shows that five new taxa appear to have entered or re entered the region over the past century statistical analysis of the atlas data reveals the presence of four ecological assemblages which are primarily correlated with seasonal and annual surface water salinity and temperature correlation with phosphate nitrate and silicate nutrients chlorophyll a and bottom water oxygen is less clear but may be important for some taxa biodiversity indices reveal strong west east biogeographical differences among the basins that reflect the different histories of mediterranean versus ponto caspian connections the atlas data provide a standardised taxonomy and regional database for interpreting downcore cyst variations in terms of quantitative oceanographic changes the atlas also provides a baseline for monitoring further changes in the bsc dinocysts that may accompany the accelerating development of the region

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

liquefaction and flow failure during earthquakes two aspects of seismically induced liquefaction are discussed which are of vital engineering significance the triggering condition and the consequences of liquefaction the triggering condition is examined with respect to liquefaction analysis note being taken of the onset condition which is governed by cyclic strength consequences of liquefaction are discussed with respect to post seismic stability analysis in which the residual strength plays a major role procedures used for liquefaction analysis based on the results of in situ sounding tests are introduced and the applicability of this method for estimating associated ground settlements is discussed the evaluation of residual strength requires a better understanding of undrained sand behaviour results of extensive laboratory rests on japanese standard sand are examined and new index parameters are proposed to quantify undrained sand behaviour better the results of laboratory tests on silty sands are examined in the same way ah the results are

aeromagnetic anomalies over faulted strata high resolution aeromagnetic surveys are now an industry standard and they commonly detect anomalies that are attributed to faults within sedimentary basins however detailed studies identifying geologic sources of magnetic anomalies in sedimentary environments are rare in the literature opportunities to study these sources have come from well exposed sedimentary basins of the rio grande rift in new mexico and colorado high resolution aeromagnetic data from these areas reveal numerous curvilinear low amplitude 2 15 nt at 100 m terrain clearance anomalies that consistently correspond to intrasedimentary normal faults figure 1 detailed geophysical and rock property studies provide evidence for the magnetic sources at several exposures of these faults in the central rio grande rift summarized in grauch and hudson 2007 and hudson et al 2008 a key result is that the aeromagnetic anomalies arise from the juxtaposition of magnetically differing strata at the faults as opposed to chemical process

instability and liquefaction of granular soils under undrained and partially drained states an experimental investigation of the initiation of instability liquefaction in saturated sand under partially drained conditions is presented the domain of stress space in which this instability develops is identified under various degrees of drainage and its relationship to the zone of instability observed under undrained shear is explored it is shown that partially drained conditions may render sand unstable that would otherwise be stable in a completely undrained state extremely small void ratio increases that cannot be regarded as physical loosening of sand if sand is partially drained contribute to instability implications of the findings are discussed in practical problems of liquefaction key words sand liquefaction undrained partially drained instability triaxial test

recognition of cyclic and non cyclic environmental changes in the mediterranean pliocene a palynological approach the interval between 2 8 and 2 3 ma b p from the south italian singa section has been investigated for its dinoflagellate cyst and sporomorph contents in order to facilitate palaeoenvironmental interpretation the following curves are derived from the data the ratios sporomorphs dinoflagellate cysts protoperidinioid gonyaulacoid dinoflagellate cysts warm cold water indicating dinoflagellate cysts inner neritic oceanic dinoflagellate cysts outer neritic oceanic dinoflagellate cysts and the reworked dinoflagellate cysts per gram of sediment furthermore the already available 18o curve has been used calibration of changes in the sporomorph dinoflagellate ratio against the computed astronomical insolation curve leads to an improved age assessment for the section frequency analysis on the curves shows the 23 41 and 100 ka frequency components to be most important phase and amplitude differences between the filtered 23 41 and 100 ka frequency components are used for environmental interpretation the 23 ka frequency band is best explained by changes in runoff induced transport the 41 ka frequency components are classified in a group with short response time to orbital forcing and a group with longer response time those signals having a short response time are attributed to local precipitation induced changes in runoff those signals having a longer response time are mainly attributed to changes in global temperature and to a lesser extent to changes in global ice volume finally longer term cyclic and non cyclic changes are mainly attributed to temperature and sea level variation

burial of living dinoflagellate cysts in estuarine and nearshore sediments the deposition and burial of living dinoflagellate cysts was studied in two different environments the nearshore waters of the southern gulf of maine and a small shallow shat pond on cape cod massachusetts perch pond vertical profiles of cysts and two naturally occuring radionuclides 210pb 234th differed significantly between the two environments at 160 m depths in the gulf of maine cyst profiles in the sediment often showed a subsurface peak in abundance 6 8 cm below the surface the 210pb profiles were consistent with a rapidly mixed surface layer 2 6 cm thick above another region 6 at least 12 cm thick where mixing was slower but still dominant over sediment deposition the sediment mixing coefficient db ranged from 15 to 26 cm2 y 1 in this lower region the radiotracer profiles and modelling results both suggest that the subsurface peaks in cyst abundance are not the result of a pulse input in one year followed by burial via bioturbation or sediment deposition instead we hypothesize that they arise from a combination of germination from the surface mixed layer and mortality at depth in contrast the cyst and radiotracer profiles in the shallow perch pond embayment are consistent with a single thin 2 cm mixed layer at the sediment surface burial of cysts below this level is due to a relatively high rate of sediment deposition 2 9 mm y 1 with little or no biological mixing this lack of mixing is consistent with reports of seasonal anoxia in perch pond a recurrent process which kills benthic animals before they reach the size or community composition needed for deep bioturbation opportunistic recolonizing species are only capable of mixing the top 1 or 2 cm resuspension and redeposition of cysts by wind and storms appears to be limited by the small size and somewhat protected location of the pond the lack of deep mixing allows us to compare the survival of cysts of different species by modelling the decrease in cyst abundance below 2 cm a simple exponential decay equation fits the data well and indicates that the living cysts of some species e g gyrodinium uncatenum gonyaulax polyedra are more susceptable to mortality in the deeper anoxic sediments than are gonyaulax verior and alexandrium formerly protogonyaulax tamarense

dinoflagellate cysts as indicators of climatic and oceanographic changes during the past 40 kyr in the santa barbara basin southern california 1 the dinoflagellate cyst record from ocean drilling program hole 893a santa barbara basin southern california is examined at millennial scale resolution for the past 40 kyr changes in cyst abundance composition of cyst assemblages and their diversity reflect major shifts in climate and ocean circulation in the region over this time interval throughout the sequence dinoflagellate cyst assemblages are dominated by heterotrophic dinoflagellates brigantedinium spp and other upwelling related taxa such as echinidinium and protoperidinium americanum are abundant indicating the continued influence of coastal upwelling on the basin during the late quaternary a significant increase in cyst accumulation rates is seen during the holocene and to a lesser extent during shorter warming events such as bolling allerod and dansgaard oeschger interstadials implying enhanced marine productivity during these periods cyst diversity is high during the holocene an increase in abundance of cysts produced by autotrophic dinoflagellates in the late holocene suggests enhanced input of warm nutrient rich waters in contrast cyst assemblages from the last glacial maximum exhibit a relatively low diversity and an increase in the cysts of heterotrophic dinoflagellates in particular selenopemphix nephroides the presence of this taxon in association with brigantedinium spp implies substantial cooling of surface waters in the santa barbara basin at that time

sand flow liquefaction instability under shear volume coupled strain paths flow liquefaction of sands is commonly studied by means of undrained tests however experimental findings indicate that seepage induced change in pore water pressure after earthquake cessation may

climate variability and land ocean interactions in the indo pacific warm pool a 460 ka palynological and organic geochemical record from the timor sea climatic conditions in the western timor sea and the adjacent northwestern part of australia are reconstructed for the last 460 ka based oil geochemical and palynological proxy records of paleoproductivity and land vegetation precipitation from images core md01 2378 reduced precipitation and elevated productivity characterize glacial stages whereas enhanced precipitation and reduced productivity are typical of interglacial stages a long term reduction in precipitation over the last 320 ka occurred in two steps at approximately 300 ka and 180 ka bp that are clearly recognizable in the pollen record variations in paleoproductivity and paleoclimate in the timor sea and adjacent landmasses appear to be driven by similar mechanisms that are related to the precession control led australian monsoon system c 2005 elsevier b v all rights reserved

evolution of paleo sea surface conditions over the last 600 years in the mackenzie trough beaufort sea canada abstract in order to document long term climate trends and predict future climate change for the arctic we need to look at the geological record to establish the link between historical and pre industrial 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 multi decadal timescales here we present the fossil dinocyst assemblages established from three sediment cores collected along an inshore offshore transect in the mackenzie trough during the 2004 cases canadian arctic shelf exchange study cruise the chronology of each core was determined using 210 pb activity and ams 14 c measurements in core 912a sediment cores 912a 909b and 906b cover the last 600 200 and 100 years respectively palynomorph influxes increase from the bottom to the top of each core illustrating an increasing productivity over the last 600 years until 1850 ad when we observe a decrease of productivity until today we determined a succession of two assemblages over the last 600 years assemblage i at the base of each core is mostly composed of dinocysts from heterotrophic taxa the modern assemblage assemblage ii at the top of each core is mostly composed of dinocysts from autotrophic taxa quantitative reconstructions of sea surface parameters reveal a sharp increase in summer august temperature 2 to 5 c throughout the study area from 1400 ad until 1800 1850 ad after which the increase between 0 5 and 1 0 c is much slower until modern times

changes in miocene through pleistocene dinoflagellates from the eastern equatorial pacific odp site 1039 in relation to primary productivity abstract palynological data from offshore costa rica allow us to investigate the relationship between dinoflagellate cyst assemblages and changes in regional oceanic primary productivity from miocene to pleistocene productivity at odp site 1039 was influenced by tectonic drift as site 1039 approached the continent from the equator to its current position at 10 n in addition dinoflagellate abundance is modulated by regional productivity events which modified primary productivity as also indicated by available data on calcareous nannofossils diatoms toc and caco 3 content five palynomorph intervals are defined the early late miocene one dominated by batiacasphaera represents relatively stable productive oceanic conditions before the closure of the indonesian and panama seaways the late miocene decrease in palynomorph recovery is related to the carbonate crash event the high abundance and diversity of the assemblages at the end of the late miocene to early pliocene indicate increased productivity related to the global biogenic bloom and a change in dominance from batiacasphaera to impagidinium to nematosphaeropsis the low abundance of the late pliocene interval is related to el nino like conditions and there is another change related to the disappearance of batiacasphaera and dominance of impagidinium nematosphaeropsis and operculodinium the abundant pleistocene assemblages represent increased marine productivity and a high influx of continental palynomorphs and bissacate pollen associated with the proximity of the costa rica dome pleistocene dinoflagellates are characterized by spiniferites and selenopemphix together with rare impagidinium and nematosphaeropsis

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

palaeoproductivity and post depositional aerobic organic matter decay reflected by dinoflagellate cyst assemblages of the eastern mediterranean s1 sapropel abstract in the reconstruction of bioproductivity in surface waters the extent to which a proxy has been diagenetically altered is often a matter of debate here we investigate how organic and calcareous walled dinoflagellate cysts can be used for separately estimating bioproductivity and oxygen related diagenesis this is achieved by studying the cyst content of the most recent eastern mediterranean sapropel s1 that is thought to have been deposited under conditions of increased primary production in surface waters and possible anoxia in the bottom waters based on chemical evidence it has been shown that the visible sapropelic layer represents only the residual lower part of what was initially a much thicker sapropel as a result of post depositional decay of organic matter related to oxygen penetration into the sediments the effect of aerobic organic matter decay on the cyst associations is studied through the comparison of the unaffected lower part of the initial sapropel and the oxidised upper part comparing the unaffected sapropelic sediments with pre and post sapropelic material gives insight into the relationship between fossil cysts assemblages and palaeoproductivity impagidinium aculeatum impagidinium patulum operculodinium israelianum polysphaeridium zoharyi and probably impagidinium spp impagidinium paradoxum and nematosphaeropsis labyrinthus are very resistant against aerobic decay and their accumulation rates appear to be primarily related to productivity in surface waters protoperidinium and echinidinium species on the other hand are shown to be very sensitive and can be used to recognise oxygen related decay the calcareous walled dinoflagellate cysts seem to be unaffected by oxic organic matter decay in mediterranean sediments

coupling between sw monsoon related surface and deep ocean processes as discerned from continuous particle flux measurements and correlated satellite data particle flux data obtained by time series sediment traps deployed at water depths of approximately 3000 m in the western central and eastern arabian sea since 1986 were compared with wind speeds derived from measurements made by microwave radiometer flying on polar orbiting satellites and sea surface temperatures ssts provided by the physical oceanography distributed active archive center at jet propulsion laboratory this comparison has allowed us to trace the link between the oceanographic and biological processes related to the development of the sw monsoon with the pattern and interannual variability of particle fluxes to the interior of the arabian sea we could recognize the well known upwelling systems along the coasts of somalia and oman as well as open ocean upwelling at the beginning of the sw monsoon both open ocean upwelling and coastal upwelling off oman cause a cooling of surface waters at our western and central arabian sea stations when ssts fall below their long term average an increase in fluxes which are dominated by coccolithophorid derived carbonates occurs the timing of this increase is determined by the rate of surface water cooling further intensification of upwelling as the sw monsoon progresses causes additional increases in biogenic opal fluxes denoting diatom blooms in the overlying waters the total fluxes during this period are the highest measured in the open arabian sea at the central arabian sea location the fluxes are only randomly affected by these blooms the particle flux in the eastern arabian sea is as high as in the central arabian sea but is influenced by a weaker upwelling system along the indian coast the observed interannual variability in the pattern of particle fluxes during the sw monsoons is most pronounced in the western arabian sea this is controlled by the intensity of the upwelling systems on the one hand and the transport of cold nutrient poor south equatorial water into the oman region on the other the latter effect which is strongest during the sw monsoon with highest recorded wind speeds reduces the influence of upwelling and the related particle fluxes at the western arabian sea station where highest fluxes occur during sw monsoons with moderate wind speeds thus coastal and open ocean upwelling are most effective in transferring biogenic matter to the deep sea during the sw monsoons of intermediate strength

rock magnetic characterization of faulted sediments with associated magnetic anomalies in the albuquerque basin rio grande rift new mexico variations in rock magnetic properties are responsible for the many linear short wavelength low amplitude magnetic anomalies that are spatially associated with faults that cut neogene basin sediments in the rio grande rift including the san ysidro normal fault which is well exposed in the northern part of the albuquerque basin magnetic susceptibility measurements from 310 sites distributed through a 1200 m thick composite section of rift filling sediments of the santa fe group and prerift eocene and cretaceous sedimentary rocks document large variations of magnetic properties juxtaposed by the san ysidro fault mean volume magnetic susceptibilities generally increase upsection through eight map units from 1 7 to 2 2e 4 in the prerift eocene and cretaceous rocks to 9 9e 4 1 2e 3 in three members of the miocene zia formation of the santa fe group to 1 5e 3 3 5e 3 in three members of the miocene pleistocene arroyo ojito formation of the santa fe group rock magnetic measurements and petrography indicate that the amount of detrital magnetite and its variable oxidation to maghemite and hematite within the santa fe group sediments are the predominant controls of their magnetic property variations magnetic susceptibility increases progressively with sediment grain size within the members of the arroyo ojito formation deposited in fluvial environments but within members of the zia formation deposited in mostly eolian environments reaches highest values in fine to medium sands partial oxidation of detrital magnetite is spatially associated with calcite cementation in the santa fe group both oxidation and cementation probably reflect past flow of groundwater through permeable zones magnetic models for geologic cross sections that incorporate mean magnetic susceptibilities for the different stratigraphic units mimic the aeromagnetic profiles across the san ysidro fault and demonstrate that the stratigraphic level of dominant magnetic contrast changes with different exposure levels into the fault these data indicate that tectonic juxtaposition of primary variations of magnetic properties of strata across the fault is the source of the associated magnetic anomaly this study indicates that magnetic anomalies over faults and folds can be generated by sediments 1 deposited within tectonic basins having volcanic or basement source areas rich in magnetite 2 having depositional environments with sufficient but varying energy to transport dense magnetic minerals and cause stratigraphic changes of magnetic properties and 3 having magnetic minerals preserved owing to their youth or nonreactive geochemical environments

possibility of postliquefaction flow failure due to seepage this study examines the postliquefaction flow failure mechanism in which shear strain develops due to seepage upward during the redistribution of excess pore water pressure after an earthquake the mechanism is addressed as both a soil element and a boundary value problem triaxial tests that reproduce the stress state of a gentle slope subjected to upward pore water inflow were performed with the results showing that shear strain can increase significantly after the stress state reaches the failure line in addition when subject to equivalent volumetric strain shear strain is considerably larger in loose sand conditions than in dense sand compared with consolidated and drained test results the dilatancy coefficient which indicates the rate of dilation is the same as that obtained from pore water inflow tests torsional hollow cylinder tests were also performed to ascertain the limit of dilation of sand specimens it was found that the values are nonlinear in behavior in addition a postliquefaction flow failure mechanism based on one dimensional consolidation theory and shear deformation behavior as a result of pore water inflow is proposed

selective preservation of organic walled dinoflagellate cysts as a tool to quantify past net primary production and bottom water oxygen concentrations to understand the role of the ocean within the global carbon cycle detailed information is required on key processes within the marine carbon cycle bio production in the upper ocean export of the produced material to the deep ocean and the storage of carbon in oceanic sediments quantification of these processes requires the separation of signals of net primary production and the rate of organic matter decay as reflected in fossil sediments this study examines the large differences in degradation rates of organic walled dinoflagellate cyst species to separate these degradation and productivity signals for this accumulation rates of cyst species known to be resistant r cysts or sensitive s cysts to aerobic degradation of 62 sites are compared to mean annual chlorophyll a sea surface temperature sea surface salinity nitrate and phosphate concentrations of the upper waters and deepwater oxygen concentrations furthermore the degradation of sensitive cysts as expressed by the degradation constant k and reaction time t has been related to bottom water o2 the studied sediments were taken from the arabian sea north western african margin north atlantic western equatorial atlantic ocean caraibic south western african margin south atlantic and southern ocean atlantic sector significant relationships are observed between a accumulation rates of r cysts and upper water chlorophyll a concentrations b accumulation rates of s cysts and bottom water o2 and c degradation rates of s cysts kt and bottom water o2 relationships that are extremely weak or are clearly insignificant on all confidence intervals are between 1 s cyst accumulation rates and chlorophyll a concentrations sea surface temperature sst sea surface salinity sss phosphate concentrations p and nitrate concentrations n 2 between r cyst accumulation rates and bottom water o2 sst sss p and n and between 3 kt and water depth co variance is present between the parameters n and p n p and chlorophyll a oxygen and water depth correcting for this co variance does not influence the significance of the relationship given above the possible applicability of dinoflagellate cyst degradation to estimate past net primary production and deep ocean ventilation is discussed 2007 published by elsevier b v

meltwater and seasonality influence on subpolar gyre circulation during the holocene abstract dinoflagellate cyst assemblages in a marine sediment core from the iceland basin were used to carry out qualitative and quantitative assessments of upper ocean conditions in the northern branch of the subpolar gyre spg during the holocene the data revealed that the early holocene i e prior to 6 8 kyr b p experienced elevated summer sea surface temperatures sst in contrast winter sst was lower compared to modern conditions this stronger than present seasonality revealed by our data thus shows the influence of the early holocene insolation forcing higher seasonality also dominated the reconstructed sea surface salinity sss in the same period with lower salinity during both summers and winters the lower sss suggests freshwater advection into the spg and the dinoflagellate cyst content from this interval indicates a dominant sourcing from the canadian labrador coast and thus the eastern margin of the laurentide ice sheet within this interval of low sss the onset of the holocene climate optimum stands out by its distinct marine assemblage components and associated high summer sst and relative sss increase between 9 3 and 7 8 kyr b p a prominent shift in the overall assemblage composition occurs at 6 8 kyr b p with lower seasonality in sea surface conditions from that time onwards increased summer and winter sss suggest that this change is linked to the halted influence of meltwater from the laurentide ice sheet a westward shift of the subpolar front and a contracted spg allowing an easier northward movement of southern sourced north atlantic waters contributing to and consequently sustained by the spin up of the overturning circulation the subpolar front appears to gradually have moved slightly eastward again between 2 8 and 1 9 kyr b p towards its modern day position with a subtle increase of elements characterized by a typical east greenland current signature in the iceland basin finally spectral analyses indicate that a range of periodicities may be present in the new sss and sst records most notably a 2000 yr periodicity in sss changes although none of the periodicities are dominant in both records or throughout the time interval covered by the records

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

reconstructing marine productivity of the cariaco basin during marine isotope stages 3 and 4 using organic walled dinoflagellate cysts 1 an organic walled dinoflagellate cyst analysis was carried out on sediment core md03 2622 retrieved from the cariaco basin the core comprises the 73 30 ka interval down core changes in cyst abundance accumulation rate and composition of cyst assemblages were used to identify climatic and oceanographic changes at orbital and millennial time scales in this near equatorial seasonal upwelling area throughout the sequence dinoflagellate cyst assemblages were dominated by heterotrophic dinocysts mainly brigantedinium spp with the exception of four autotrophic dominated mainly spiniferites ramosus intervals around 58 53 46 and 37 ka at orbital time scales changes in the dinoflagellate productivity seem to follow low latitude insolation with the highest productivities coinciding with maximum february insolation 47 38 ka at millennial scales cyst accumulation rates appeared to coincide with dansgaard oeschger d o variability with significant increments occurring during warm interstadials the opposite was true during stadials short periods of high nutrient availability and stratified conditions followed heinrich events h4 h5 h5a and h6 and concurred with enhanced river runoff spectral analyses confirm the existence of these and other higher frequency periodicities and support the idea of a tightly coupled terrestrial marine and tropical high latitude climate system during the last glacial period

structural controls on geothermal circulation in surprise valley california a re evaluation of the lake city fault zone faults and fractures play an important role in the circulation of geothermal fluids in the crust and the nature of that role varies according to structural setting and state of stress as a result detailed geologic and geophysical mapping that relates thermal springs to known structural features is essential to modeling geothermal systems published maps of surprise valley in northeastern california suggest that the lake city fault or lake city fault zone is a significant structural feature cutting obliquely across the basin and connecting thermal springs across the valley newly acquired geophysical data audio magnetotelluric gravity and magnetic combined with existing geochemical and geological data suggest otherwise we examine potential field profiles and resistivity models that cross the mapped lake city fault zone while there are numerous geophysical anomalies that suggest subsurface structures they mostly do not coincide with the mapped traces of the lake city fault zone nor do they show a consistent signature in gravity magnetics or resistivities that would suggest a through going fault that would promote connectivity through lateral fluid flow instead of a single continuous fault we propose the presence of a deformation zone associated with the growth of the range front surprise valley fault the implication for geothermal circulation is that this is a zone of enhanced porosity but lacks length wise connectivity that could conduct fluids across the valley thermal fluid circulation is most likely controlled primarily by interactions between n s trending normal faults

use of selective degradation to separate preservation from productivity the assessment of diagenetic influences on the sedimentary record is problematic despite its crucial importance for accurate environmental reconstruction and understanding of biochemical cycles we propose a general applicable method that uses differences in degradation rates of organic components to separate degradation and productivity we demonstrate this method on a southeastern atlantic sediment core covering the past 145 k y the new method solves discrepancies between existing organic matter silica and carbonate based productivity reconstructions and emphasizes the importance of bottom and pore water characteristics for transformation of the sedimentary record

paleohydrology and paleoclimatology off northwest africa during the last glacial interglacial transition and the holocene palynological evidences abstract pollen and dinoflagellate cyst analyses of deep sea core located off morocco provide a continuous record of paleoclimatic and paleohydrological change off northwestern africa since the last glacial episode the stratigraphy is given by isotopic analysis 18 o of planktonic foraminifera which shows a two step deglaciation xeric conditions on the adjacent land marked by the increase of steppe taxa artemisia chenopodiaceae amaranthaceae ephedra and the development of the montane taxon cedrus atlantica are observed before termination ia and during the younger dryas these intervals are also marked by a high abundance of pinus pollen grains which indicates a strengthening of the northeastern ne trade winds variations of the surface water temperatures are shown by the fluctuations of dinoflagellate cyst assemblages which reflect a cooling of the surface waters during termination ia and the younger dryas episode intensification of the upwelling system off morocco resulting from enhanced trade winds occurred during these two key periods quercus forests which are an important part of the present day vegetation of the maghreb region developed around 8500 yr b p dinoflagellate cyst assemblages suggest that present day oceanic conditions were established during this period

water film in liquefied sand and its effect on lateral spread a one dimensional 1d saturated sand layer of 2 m in thickness in which a silt seam is sandwiched is liquefied by an instant shock it is found that a water film is easily formed beneath the silt seam with a thickness as thin as a few millimeters just after liquefaction in loose sand and that the film lasts longer than the postliquefaction settlement the effect of the water film on pore pressure distribution and sand settlement is intensively studied one gram shake table tests are then carried out for 2d models with or without seams of silt within a saturated sand layer in the former case water films formed beneath silt seams just after liquefaction enable the soil mass above them to glide because of an unbalanced force along the water films not only during but also after shaking in the latter case the soil deforms continuously mostly during shaking and stops afterward thus a significnat effect of water films formed beneath thin low permeability sublayers in a liquefied loose sand on the failure mode and timing in lateral spread is clearly demonstrated by these simple model tests

seismic liquefaction lateral spreading and flow slides a numerical investigation into void redistribution experience from past earthquakes indicates that seismically induced large lateral spreads and flow slides in alluvial sand deposits have taken place in coastal and river areas in many parts of the world the ground slope in these slides was often not very steep gentler than a few percent recent research indicates that the presence of low permeability silt or clay sublayers within the sand deposits is responsible for this behaviour such layers form a barrier to upward flow of water associated with earthquake generated pore pressures this causes an accumulation of pore water at the base of the layers resulting in greatly reduced strength and possible slope instability this paper uses an effective stress coupled stress flow dynamic analyses procedure to demonstrate the effects of a low permeability barrier layer on ground deformations from an earthquake event the analyses show that an expansion zone develops at the base of barrier layers in stratified soil deposits under seismic loading which can grea

organic walled dinoflagellate cysts and benthic foraminifera in coastal sediments of the last century from the gulf of tehuantepec south pacific coast of mexico abstract qualitative and quantitative analysis of recent organic walled dinoflagellate cysts dinocysts was performed on surface sediment samples and a core from the continental shelf of the gulf of tehuantepec mexico in order to document the spatial distribution of dinocyst assemblages in relation to upwelling and primary productivity and to assess the environmental history of the last century the analyses of surface sediment samples show a close relation between dinocyst assemblages and productivity on a regional scale polysphaeridium zoharyi and heterotrophic taxa notably brigantedinium spp dominate in the high productivity zone whereas spiniferites delicatus and other phototrophic taxa are more abundant in the lower productivity zone sediment in an eighteen cm long gravity core dated using 210 pb and 137 cs provided a record of the last century at annual to decadal resolution thus yielding a unique opportunity to examine variations in dinocyst assemblages associated with environmental changes cyst concentrations in the core range between 477 and 2300 cysts g 1 giving cyst fluxes between 68 and 494 cysts cm 2 yr 1 twenty three phototrophic and heterotrophic cyst taxa were identified brigantedinium spp p zoharyi and bitectatodinium spongium are dominant and are associated with the seasonal upwelling that characterizes the area cysts of potentially toxic species such as p zoharyi the cyst of pyrodinium bahamense var compressum and or bahamense occur throughout the core despite slight variations in relative abundances of the taxa in the assemblages there is no evidence for eutrophication following industrial development of the adjacent coastal zone core samples were also analyzed for benthic foraminiferal content in order to determine possible effects of high upwelling induced productivity on bottom water oxygenation the benthic foraminiferal assemblages are dominated by hanzawaia concentrica over 50 with less abundant uvigerina excellens cancris spp planulina ornata quinqueloculina lamarckiana epistominella sandiegoensis nonionella basispinata cassidulina modeloensis and textularia foliacea the benthic foraminiferal assemblages are characteristic of oxygen concentrations above 1 ml l 1 indicating that possible changes in productivity did not significantly affect bottom water oxygen concentrations over the last 100 years

recent anthropogenic and climatic history of nunatsiavut fjords labrador canada this study aimed at reconstructing past climatic and environmental conditions of a poorly known and documented subarctic region the nunatsiavut northern labrador a multiproxy approach was chosen using fossil dinoflagellate cysts diatoms and pollen from sediment cores taken into three fjords nachvak 59 n saglek 58 5 n and anaktalak 56 5 n it allowed estimating terrestrial and marine influences in each fjord and documenting the recent history of human activities of the southern fjords saglek and anaktalak fossil pollen and dinoflagellate cyst assemblages allowed depicting the climate history of the region over the last 200 300 years in contrast to the general warming trend observed in the arctic and subarctic canada since the beginning of the industrial era the nunatsiavut has experienced relative climate stability over this period fossil pollen data show a shift of the tree limit to the south illustrating the cooling of terrestrial conditions our reconstructions suggest that the labrador region has remained climatically stable over the last 150 300 years with just a slight cooling trend of the reconstructed sea surface temperatures only perceptible in saglek and anaktalak fjords

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

palaeo ecological significance transport and preservation of organic walled dinoflagellate cysts in the somali basin nw arabian sea to date relatively little information is available about factors influencing organic walled cyst production of tropical dinoflagellates and processes influencing the final burial of cysts in bottom sediments such as transport and preservation to extend this information cyst fluxes were documented for three sediment traps from june 1992 to february 1993 at two sites in the somali basin northwestern arabian sea as well as the cyst association of underlying sediments by comparing cyst associations of contemporaneously collected trap samples at different depths at one site information about transport and processes of decay in the water column was obtained neither transport nor decay appears to have any detectable influence on cyst association during cyst settlement through the water column comparing the trap associations with the underlying sediments indicates that downslope transport appears to have influenced the cyst association on a local scale only species selective decay probably related to the presence of oxygen in bottom sediments has influenced the cyst association most pronouncedly at the most offshore site relating variations in the trap associations with environmental conditions of the overlying surface waters indicates that highest production of both filled and empty cysts occurs during the sw monsoon upwelling based on this correlation three groups of species can be distinguished species with highest fluxes during 1 the first half of the sw monsoon june august bitectatodinium spongium echinidinium granulatum echindinium transparantum echinidnium spp cysts of protoperidinium compressum and cysts of protoperidinium subinerme 2 the transition between the sw monsoon and inter monsoon spiniferites mirabilis and spiniferites spp 3 no particular season all other species cyst associations of all trap samples are dominated by cyst of protoperidinium species cysts with highest fluxes during the sw monsoon form about a third of the associations

a 35 000 year record of changes in the eastern indian ocean offshore sumatra article i nfo we have examined the upper 276 cm of deep sea core bar9403 taken at a water depth of 2034 m offshore the southern portion of sumatra in the eastern indian ocean using several micropalaeontological proxies faunal counts and stable isotopes of oxygen and carbon of planktic and benthic foraminifers as well as floral counts of dinoflagellates were obtained to reconstruct conditions in the oceans over the last 35 000 years at times we found that when benthic foraminifers indicate high organic content values at the bottom of the ocean this is not paralleled by high productivity signals at the sea surface but instead must relate to changes in bottom water circulation as a result of slower water circulation the marine isotopic stages mis 3 1 are clearly differentiated by benthic and foraminiferal assemblages as well as dinoflagellates and their cysts mis 3 is characterised by a much sharper than today thermocline that was closer to the sea surface and by the absence of a low salinity barrier layer which today results from high monsoonal rains the absence of the latter persisted during the last glacial period mis 2 when bottom circulation must have been reduced and high percentages of organic matter occurred on the sea floor combined with low dissolved oxygen levels the deglaciation is marked by a change in salinity at the sea surface as seen by the dinoflagellates and planktic foraminifers and progressive alteration of the thermocline was detected by foraminifers suggesting a less productive deep chlorophyll maximum in contrast with mis 3 and 2 monsoonal activity commenced around 15 000 cal years ago and was well established 2000 years later the holocene is marked by a significant increase in river discharge to the ocean pulsed by the delivery of organic matter to the sea floor despite overall oligotrophic conditions at and near the sea surface induced by a permanent low salinity cap we did not identify obvious and persistent upwelling conditions offshore sumatra for the last 35 000 years

late quaternary environmental changes and latitudinal shifts of the antarctic circumpolar current as recorded by dinoflagellate cysts from offshore chile 41 s abstract the late quaternary organic walled dinoflagellate cyst record of site 1233 41 s offshore chile was studied with a 200 year resolution spanning the last 25 000 years the study provides the first continuous record of sub recent and recent dinoflagellate cysts in the southeast se pacific major changes in the composition of the cyst association cyst concentration and morphology of operculodinium centrocarpum reflect changes in sea surface temperature sst sea surface salinity sss palaeoproductivity and upwelling intensity these changes can be associated with latitudinal shifts of the circumpolar frontal systems the high cyst concentration high brigantedinium spp abundances low species diversity and the occurrence of certain cold water species are supportive for a 7 10 equatorward shift of the antarctic circumpolar current acc during the coldest phase of the last glacial maximum lgm between 25 and 21 1 cal ka bp deglacial warming initiated at 18 6 cal ka bp termination i 18 6 11 1 cal ka bp is interrupted by an unstable period of extreme seasonality rather than a cooling event between 14 4 and 13 2 cal ka bp synchronous with the antarctic cold reversal acr the holocene maximum is observed between 11 6 and 9 8 cal ka bp and is typified by the most southward position of the northern margin of the acc a cooling phase occurred during the early holocene until 7 cal ka bp and during the last 0 8 ka our data indicates that the se pacific 41 s climate has been influenced over the whole record by changes in the southern hemisphere sh high latitudes while during the mid to late holocene also a tropical forcing mechanism was involved including the el nino southern oscillation and the variable hadley cell intensity furthermore this study showed a relationship between the variable morphology of the spines processes of o centrocarpum and the combined variation of sea surface salinity and temperature sss sst ratio

palynological evidence for climatic and oceanic variability off nw africa during the late holocene pollen and organic walled dinoflagellate cyst assemblages from core geob 9503 5 retrieved from the mud belt 50 m water depth off the senegal river mouth have been analyzed to reconstruct short term palaeoceanographic and palaeoenvironmental changes in subtropical nw africa during the time interval from ca 4200 to 1200 cal yr bp our study emphasizes significant coeval changes in continental and oceanic environments in and off senegal and shows that initial dry conditions were followed by a strong and rapid increase in humidity between ca 2900 and 2500 cal yr bp after ca 2500 cal yr bp the environment slowly became drier again as indicated by slight increases in sahelian savannah and desert elements in the pollen record around ca 2200 cal yr bp this relatively dry period ended with periodic pulses of high terrigenous contributions and strong fluctuations in fern spore and river plume dinoflagellate cyst percentages as well as in the fluxes of pollen dinoflagellate cysts fresh water algae and plant cuticles suggesting episodic flash flood events of the senegal river the driest phase developed after about 2100 cal yr bp

high resolution palynological record of holocene climatic and oceanographic changes in the northern south china sea abstract for the first time palynological records of terrestrial palynomorphs and dinoflagellate cysts are investigated in a sediment core from the northern south china sea scs covering the last 12 500 years both terrestrial and marine palynomorph records show strong signals of the sea level change during the studied interval the highest herb pollen content was associated with extensive grasslands on the exposed shelf at the low sea level stand during the younger dryas and early holocene the increase in fern spores and decrease in concentrations of dinoflagellate cysts and terrestrial palynomorphs was observed during the sea level rise interval from 12 500 to 6800 or 6000 cal yr bp then the sea level became stabilized and consistently low dinoflagellate cyst abundances and high abundances of fern spores were recorded a high abundance of impagidinium in the period 12 000 10 400 cal yr bp possibly resulted from increased input of western philippine sea waters into the scs and the branching of the kuroshio current a short term decrease of impagidinium at 11 700 11 000 cal yr bp corresponding to the mwp 1b event might be associated with input of the east china sea waters through the taiwan strait the relationship between the sedimentation rates and the concentrations of terrestrial palynomorphs indicates a water dominant transport for pollen and spore dispersal prior to 6300 cal yr bp whereas wind transport became more prominent thereafter the timing of this change corresponds to the highest sea level stand at 6800 6000 cal yr bp when the present oceanographic setting was formed the mid holocene optimum can be seen by the highest abundance of subtropical tropical broad leaved arboreal pollen and by the highest abundances of dapsilidinium pastielsii three strengthened winter monsoon intervals at 5500 cal yr bp 4000 cal yr bp and 2500 cal yr bp are reflected by increases in pinus pollen content after the present oceanographic condition formed

predicting the onset of static liquefaction of loose sand with fines abstractloose sandy soil subject to undrained shearing manifests deviatoric strain softening and such a behavior has been referred to as collapse static liquefaction or instability this paper uses the term instability and characterizes its triggering by the corresponding effective stress ratio referred to as the instability ratio is to capture the influence of fines on is the state parameter as originally proposed by been and jefferies was generalized to an equivalent granular state parameter this is achieved simply by replacing the void ratio e with the equivalent granular void ratio e the conversion from e to e was achieved by a predictive approach and backanalysis is not required it was hypothesized that provided the fines content is less than the threshold value is and at the start of undrained shearing can be described by a single relationship irrespective of the fines content two published databases and a series of undrained triaxial tests results are used to eva

dinoflagellate cysts from two sediment traps east of new zealand abstract two discontinuous sediment trap records of organic walled dinoflagellate cyst dinocyst flux each sampling 300 days within the years 2005 2009 were derived from two time incremental traps deployed at 1500 m water depth east of new zealand the traps sampled flux from beneath two distinct surface water masses on either side of the subtropical front i warm seasonally macronutrient depleted subtropical and ii cold micronutrient limited subantarctic waters nineteen dinocyst taxa or taxonomic groups were identified from the trap samples trap assemblages at both sites were dominated by cysts of protoperidiniaceae notably brigantedinium spp which comprised almost 98 of the dinocyst flux the seasonality of the dinocyst flux differed between the traps with a pronounced spring flux in the subtropical trap while seasonal variation in the subantarctic trap was relatively muted in subtropical waters moderate correlation was observed between protoperidiniaceae cyst flux and chlorophyll a concentrations in surface waters in the 3 4 weeks prior to sampling in subantarctic waters there was a weak correlation between protoperidiniaceae cyst flux and reduced intensity of storm induced turbulence during the preceding 2 3 weeks there was a large discrepancy between dinocyst assemblages in the traps and those observed in nearby sea floor sediments protoperidiniaceae dinocysts particularly echinidinium and brigantedinium were highly under represented in the sea floor assemblages these forms are more susceptible to degradation in oxygenated sediments than other dinocysts but inter annual variability in cyst flux or short term variation not covered by sampling discontinuities in the current study could also have contributed to this discrepancy the major differences in the seasonality of dinocyst fluxes between the two water masses examined in this initial study suggest that mean annual rather than seasonal climatologies are more appropriate for dinocyst based quantitative palaeoenvironmental reconstructions in the new zealand region

evaluation of simulation models of lateral spread sites treated with prefabricated vertical drains abstractfinite element analyses are performed of centrifuge tests consisting of untreated and drain treated lateral spread sites with the goal of evaluating the ability of numerical simulations to predict the response of sites improved with prefabricated vertical drains finite element models of varying complexity are analyzed a two dimensional model of the full centrifuge test a three dimensional unit cell model around a single drain and a two dimensional unit cell model all the finite element models predict pore pressures consistent with the centrifuge tests the deformation responses of the finite element models show that unit cell analyses produce significantly larger deformations than those observed in the centrifuge this result is caused by the fact that the centrifuge test geometry is not well represented by the infinite slope condition assumed in a unit cell the full two dimensional model predicts deformations that are more consistent with those of the centrifuge because it can capture the

soil liquefaction induced uplift of underground structures physical and numerical modeling abstractunderground structures located in liquefiable soil deposits are susceptible to floatation following a major earthquake event such failure phenomenon generally occurs when the soil liquefies and loses its shear resistance against the uplift force from the buoyancy of the underground structure numerical modeling accompanied with centrifuge experiments with shallow circular structures has been carried out to investigate the floatation failure at different buried depths of the structure the influence of the magnitude of input sinusoidal earthquake shaking was also studied both numerical and experimental results showed matching uplift response of the structures and acceleration and pore pressure measurements in the liquefied soil deposit a higher uplift displacement of the structure was observed for shallower buried depth thereby indicating the influence of overlying soil weight against floatation results also showed that the structures commenced floatation in the presence of high excess pore pr

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

experimental investigation of drainage during earthquake induced liquefaction earthquake induced liquefaction is typically viewed as an undrained phenomenon with undrained element tests forming the core of knowledge built around it however there is evidence to suggest that

advancements in understanding the aeromagnetic expressions of basin margin faults an example from san luis basin colorado advancements in aeromagnetic acquisition technology over the past few decades have led to greater resolution of shallow geologic sources with low magnetization such as intrasedimentary faults and paleochannels detection and mapping of intrasedimentary faults in particular can be important for understanding the overall structural setting of an area even if exploration targets are much deeper aeromagnetic methods are especially useful for mapping structures in mountain piedmont areas at the margins of structural basins where mineral exploration and seismic hazard studies may be focused and where logistical or data quality issues encumber seismic methods understanding if the sources of aeromagnetic anomalies in this context originate from sedimentary units or bedrock is important for evaluating basin structure and or depth to shallow exploration targets

stability of scour protection due to earthquake induced liquefaction centrifuge modelling abstract a key aspect of permanent offshore structures is protection against scour this is typically in the form of a blanket of coarse gravel or cobbles surrounding the structure these coarse particles are selected for their high resistance to being displaced by strong currents and thus protect the underlying finer sand particles from scour however in the event of an earthquake the foundation sand may be susceptible to some degree of liquefaction this research investigates the effects of seismic induced liquefaction over a scour blanket and if sinking is inhibited by some combination of the additional effective stress imposed by the gravel together with the interlocking resistance that develops when coarse particles are subjected to relative displacements in order to evaluate the stability of scour protection blankets a programme of physical modelling was carried out involving the assessment of different configurations of stone layers over a liquefiable material and a monopile type foundation models were subjected to scaled base shaking equivalent to earthquake loading a mass balance of particle sinkage showed that a filter layer was critical for maintaining the integrity of the armour stones based on displacement and pore water pressure measurements it was found that the presence of the scour protection blankets improved the response of the liquefiable sand under seismic loading and even inhibited the occurrence of liquefaction this implies that a well designed scour protection blanket can assist in protecting against earthquake effects also

the behavior of a compressible silty fine sand publications associated with sands are often limited to clean i e little fines content uniform uncemented silica or quartz sand on the other hand the importance of mineral content particle

undrained and drained stress strain response the deformation response of saturated soils to a total stress increment at the ambient void ratio and effective stress state is shown to be dependent on the direction of the effective strain increment it is argued that in a given field problem most soil elements neither deform fully drained nor undrained but do so partially drained the degree of partial drainage controls the direction of the effective stress increment and hence the deformation response experimental data are presented which demonstrate how shear stiffness changes with the direction of effective stress increment as a function of the ambient effective stress state key words stress strain undrained drained partially drained stress path stiffness

recent eutrophication and consequent hypoxia in the bottom waters of the lower st lawrence estuary micropaleontological and geochemical evidence micropaleontological and geochemical analyses were carried out on two sediment box cores ah00 2220 and cr02 23 recovered in the lower st lawrence estuary lsle in order to document recent temporal variations of primary productivity and carbon fluxes to the bottom waters these reveal a ten fold increase in the accumulation rate of dinoflagellate cysts and benthic foraminifera in the sediment over the last four decades which can be interpreted as a recent increase in pelagic and benthic production furthermore the appearance of the benthic foraminiferal species brizalina subaenariensis and bulimina exilis which are tolerant of low oxygen concentrations and high organic fluxes in the upper 20 cm of the cores may reflect significant changes in bottom water conditions over the last 40 yrs variations in the microfossil abundances in core ah00 2220 are strongly correlated with an increase in organic carbon oc content from 1 1 to 1 6 and to a shift in the isotopic signature of the latter 13 corg from 24 8 to 24 0 similarly a concomitant decrease in the corg n ratio from 15 to 12 an increase in organic carbon content from 1 3 to 1 9 and an increase in 13 corg from 24 5 to 23 5 were observed in core cr02 23 all of which suggest an enhanced accumulation of marine over terrestrial oc in the lsle our results imply that a significant increase in marine productivity in the lsle occurred since the 1960 s 2006 elsevier b v all rights reserved

drained instability of sand in plane strain flowslide or failure of loose granular soil slopes is often explained using liquefaction or instability data obtained from undrained triaxial tests however under static loading conditions the assumption of an undrained condition is not realistic for sand particularly clean sand case studies have indicated that instability of granular soil can occur under essentially drained conditions e g the wachusett dam failure in 1907 laboratory studies on changi sand by chu et al in 2003 have shown that sand can become unstable under completely drained conditions however these studies were carried out under axisymmetric conditions and thus cannot be applied directly to the analysis of slope failures in this paper experimental data obtained from plane strain tests are presented to study the instability behaviour of loose and dense sand under plane strain conditions based on these test data the conditions for the occurrence of drained instability in plane strain are established using the modified sta

recent geographical distribution of organic walled dinoflagellate cysts in the southeast pacific 25 53 s and their relation to the prevailing hydrographical conditions abstract forty eight surface sediment samples from the southeast se pacific 25 53 s are investigated for the determination of the spatial distribution of organic walled dinoflagellate cysts along the western south american continental margin fifty five different taxa are recorded and reflect oceanic or coastal assemblages the oceanic assemblages are characterised by low cyst concentrations and the dominance of autotrophs while the coastal assemblages generally contain a higher number of cysts which are mainly produced by heterotrophic species highest cyst concentrations are observed in the active upwelling system offshore concepcion 35 37 s brigantedinium spp echinidinium aculeatum echinidinium granulatum delicatum and cysts of protoperidinium americanum dominate assemblages related to upwelling echinidinium aculeatum appears to be the best indicator for the presence of all year round active upwelling cells other protoperidinioid cysts may also occur in high relative abundances in coastal regions outside active upwelling systems if the availability of nutrients co responsible for the presence absence of their main food sources such as diatoms and other protists is sufficient the importance of nutrient availability as a determining environmental variable influencing cyst signals on a regional scale se pacific is demonstrated through statistical analyses of the data because of the importance of nutrients uncertainties about the outcomes of quantitative sea surface temperature sst reconstructions modern analogue technique based on dinoflagellate cysts may arise since no interaction between different hydrographical variables is considered in this approach the combination of the se pacific surface sample dataset with other published cyst data from the southern hemisphere resulted in a database which includes 350 samples the sh350 database this database is used to test the accuracy of the quantitative reconstructions by calculating and comparing the estimated versus observed values for each site an attempt to perform quantitative sst reconstructions on the last 25 cal ka of site odp1233 41 s 74 27 w is made and again stresses the importance of other environmental variables such as nutrient availability in determining the dinoflagellate cyst assemblages

late quaternary climatic and oceanographic changes in the northeast pacific as recorded by dinoflagellate cysts from guaymas basin gulf of california mexico a high resolution record of organic walled dinoflagellate cyst production in guaymas basin gulf of california mexico reveals a complex paleoceanographic history over the last 40 ka guaymas basin is an excellent location to perform high resolution studies of changes in late quaternary climate and paleo productivity because it is characterized by high primary productivity high sedimentation rates and low oxygen bottom waters these factors contribute to the deposition and preservation of laminated sediments throughout large portions of the core md02 2515 in this study we document dinoflagellate cyst production at a centennial to millennial scale throughout the late quaternary based on the cyst assemblages three dinoflagellate cyst zones were established and roughly correspond to marine isotope stages miss 1 to 3 miss 1 and 3 are dominated by cysts of heterotrophic dinoflagellates whereas mis 2 is characterized by enhanced variability and a greater proportion of cysts produced by autotrophic taxa the most dominant dinoflagellate cyst taxa found throughout the core were brigantedinium spp and operculodinium centrocarpum dansgaard oeschger event 8 is observed in the dinoflagellate cyst record where it is characterized by an increase in warm taxa such as spiniferites pachydermus other intervals of interest are the younger dryas where warmer conditions are recorded and the holocene which is characterized by the consistent presence of tropical species stelladinium reidii tuberculodinidum vancampoae bitectatodinium spongium and an increase in quinquecuspis concreta changes in cyst assemblages concentrations and species diversity along with geochemical data reflect major orbital to millennial scale climatic and oceanographic changes reference price a m k n mertens v pospelova t f pedersen and r s ganeshram 2013 late quaternary climatic and oceanographic changes in the northeast pacific as recorded by dinoflagellate cysts from guaymas basin gulf of california mexico paleoceanography 28 doi 10 1002 palo 20019

the relationship between neogene dinoflagellate cysts and global climate dynamics abstract the neogene period 23 03 2 58 ma underwent a long term relatively gradual cooling trend culminating in the glacial interglacial climate of the quaternary palaeoclimate studies on the neogene have provided important information for understanding how modern patterns of atmospheric and oceanic circulation developed and how they may relate to wider environmental change here we use a newly created global database of neogene dinoflagellate cysts the tertiary oceanic parameters information system topis to investigate how dinoflagellate cysts recorded the cooling of neogene surface marine waters on a global scale species with warm and cold water preferences were determined from previously published literature and extracted from the database percentages of cold water species were calculated relative to the total number of species with known temperature preferences from each site and compared throughout the neogene at differing latitudes overall the percentage of cold water species increases gradually through the neogene this trend indicates a gradual global cooling that is comparable to that reported from other marine and terrestrial proxies this also demonstrates the use of dinoflagellate cysts in determining temperature change on both extended temporal and wide geographical scales the increase in the percentage of cold water species of dinoflagellate cysts recorded worldwide from the early and middle miocene to the late pliocene indicates a global scale forcing agent on neogene climate such as co2

void redistribution in sand under post earthquake loading a mechanism for void redistribution in an infinite slope under post earthquake loading conditions is described by consideration of the in situ loading paths that can occur under post earthquake conditions and the results of triaxial tests designed to represent specific in situ post earthquake loading paths the mechanism is illustrated by application to an example problem void redistribution is shown to be a phenomena that may be more pronounced at the field scale than at the laboratory scale key words liquefaction earthquake void redistribution triaxial sand

average process length variation of the marine dinoflagellate cyst operculodinium centrocarpum in the tropical and southern hemisphere oceans assessing its potential as a palaeosalinity proxy the study investigates the morphological variability of the dinoflagellate cyst operculodinium centrocarpum resting cyst of protoceratium reticulatum in core top samples distributed over the southern hemisphere and the tropics in relation to sea surface temperature sst and sea surface salinity sss at the corresponding sites the process lengths show a moderate inverse relationship to summer sst ssst r 0 44 and ssss ssst r 0 4 however lateral transport of cysts probably produced noise in the plots after excluding tropical and southern hemisphere sites considered to have been affected by long distance lateral transport the relationship between process length and density follows the equation sd 0 8422x 1016 9 r 0 55 with a root mean square error 0 63 kg m 3 while the negative correlation with ssst increases up to r 0 79 next to salinity this study thus highlights the importance of a second factor temperature affecting process length in the topics and the southern hemisphere oceans

elements d une climatostratigraphie du pleistocene moyen et tardif dans l est du canada par l analyse palynologique et isotopique du forage 84 030 003 mer du labrador the piston and gravity cores 84 030 003 collected in the southern labrador sea have been sampled for detailed palynological and isotopic analyses the 18o record on foraminifera neogloboquadrina pachyderma left coiling indicates a stratigraphy spanning isotopic stages 8 to 1 i e over ca 300 000 years the isotopic record allows the calculation of a mean sedimentation rate of approximately 5 cm ka the pollen and spore contents of the sediments are low the low pollen influxes generally less than 1 grain cm2 per year and the dominance of pinus suggest aeolian transport over long distances with southwest northeast to south southwest north northeast trends dinoflagellate cyst concentrations are relatively low indicating a low regional phytoplanktonic productivity the assemblages are however diversified they reflect influences from the north atlantic drift and from the labrador current the occurrence of warm temperate to tropical impagidinium species in deposits suggests an almost permanent

dinoflagellate cyst distribution in sediments of western bay of bengal role of sea surface conditions bay of bengal is a shallow marine basin exposed to seasonal fluctuation in precipitation and run off thus salinity temperature nutrient and productivity vary along the latitudinal and onshore offshore gradient in the bay of bengal these parameters directly affect primary productivity including that of dinoflagellate cysts the spatial distribution of organic walled dinoflagellates cyst is studied in the 50 surface samples of eight transects from the western bay of bengal to infer variation in the environmental conditions in the region the cyst diversity consists of 40 taxa with an overall high dominance of protoperidinioid cysts over gonyalaucoides based on the study distinct onshore and offshore dinocyst assemblages are identified the high productive coastal upwelling region is characterised by the dominance of gonyalaucoid dinocyst species bitectatodinium spongium zonneveld 1997 zonneveld and jurkschat 1999 indicating its adaptability to the fluctuating salinity and high nutrient conditions the outer shelf to middle slope regions of western bay of bengal is dominated by the protoperidinioid species this is in contrast to the gonyalaucoid dinocyst assemblages of the outer shelf to middle slope regions in other oceans since protoperidinioids prefer high nutrient and reducing environmental conditions for growth and preservation their presence suggest high nutrient availability due to the river discharge and low oxygen condition in the slope region in bay of bengal statistical analyses of the sea surface parameters and dinoflagellate cyst abundance data indicate that salinity and silicates as a major source of nutrient played a major role in the distribution of dinoflagellate cyst in the bay of bengal

source of anomalous magnetization in area of hydrocarbon potential petrologic evidence from jurassic preuss sandstone wyoming idaho thrust belt the jurassic preuss sandstone which crops out in the central part of the wyoming idaho thrust belt on trend with a hydrocarbon producing region to the south has been previously identified as the source of anomalous magnetization in the area elsewhere anomalous magnetization in sedimentary rocks near hydrocarbon accumulations has been attributed to hydrocarbon engendered magnetic minerals but magnetization of the preuss is controlled by detrital magnetite evidence of a detrital origin for magnetite includes 1 concentration of magnetite grains along laminations containing other heavy minerals 2 the presence of exsolved ilmenite hematite and spinel in the magnetite grains and 3 titanium contents typical of igneous derived magnetite that detrital magnetite is responsible for the anomalous magnetization in the preuss is further indicated by the systematic eastward decrease in magnetite abundance corresponding to a similar eastward decrease in magnetic susceptibility and remanent magnetization of the unit petrologic and vitrinite reflectance studies indicate a complex low temperature 150 c or 302 f diagenetic history for the preuss nevertheless preservation of detrital magnetite the presence of diagenetically early ferric oxide minerals and the absence of sulfide minerals all indicate that the preuss has not experienced sulfidic reducing conditions common in areas of hydrocarbon seepage the marine carbon isotopic composition of calcite that cements most preuss sandstones dgr13c values ranging from 2 47 to 1 48 pmil is evidence that carbonate diagenesis also was not influenced by hydrocarbons the results of this multidisciplinary study of the preuss underscore the importance of similar studies when evaluating the sources of aeromagnetic anomalies in areas of hydrocarbon potential

geographical distributions of organic walled dinoflagellate cysts in surficial sediments of the benguela upwelling region and their relationship to upper ocean conditions the organic walled cyst content of 41 surface sediment samples from the south eastern south atlantic ocean have been studied to create a dataset that can be used for palaeoceanographic reconstructions in order to obtain insight into which environmental factors influence the distribution of individual cyst species the cyst associations have been compared with oceanographic characteristics of the overlying water masses i e temperature salinity density and stratification gradients the associations and relationships have been established by visual examination of the dataset and the multivariate ordination techniques detrended correspondence analysis and canonical correspondence analysis special attention has been given to the factors of transport and preservation of the cysts five associations have been recognised as being characteristic of 1 areas influenced by coastal upwelling and or river outflow 2 open ocean 3 agulhas current and southern benguela current 4 benguela current and 5 walvis bay shelf break area the factors dominant in influencing either directly or indirectly the cyst distributions appear to be the stratification in the upper 50 m of the water column nutrient concentration and seasonality variations in sea surface temperatures and salinities have only minor effect on cyst distribution

provenance of post wapiabi sandstones and its implications for campanian to paleocene tectonic history of the southern canadian cordillera late campanian to early paleocene sandstones of the alberta foothills were derived from three types of rocks i andesitic dacitic volcanic rocks that were presumably comagmatic with middle to late mesozoic plutons in the omineca crystalline belt ii low grade metamorphic rocks in the suprastructure of the omineca crystalline belt and iii sedimentary rocks in die rocky mountain thrust belt principally pelitic rocks in the western main ranges and carbonates and chert arenites in the eastern main and front ranges a paucity of quartzo feldspathic rocks fragments and potassium feldspar indicates that the core of the omineca crystalline belt was not extensively exposed at that time vertical trends in composition of the sandstones reveal five petrographic stages stage i is dominated by volcanic rock fragments and plagioclase suggesting that initial progradation of the sediment was largely a response to coeval volcanism or tectonic emplacement of older volcanic rocks stages iii and v are characterized

modelling the behaviour of large gravity wharf structure under the effects of earthquake induced liquefaction abstract gravity wharf structures are widely used worldwide to form shallow and deep water ports they are large structures with a height of 25 50 m depending on the water depth when these structures are to be sited on loose to medium dense sand earthquake induced liquefaction settlements present a significant risk this often requires expensive soil replacement or other ground improvement techniques in this paper the dynamic behaviour of these large structures that exert very high bearing pressures on the foundation soil was investigated for the first time the level of settlements they can suffer due to soil liquefaction was investigated using dynamic centrifuge testing it will be shown that the full liquefaction does not occur below the structure even when the free field soil fully liquefies during strong earthquakes however there will be some stiffness degradation owing to excess pore pressure generation and consequent structural settlements the level of these settlements are considered to be acceptable from a service limit state sls perspective in addition to this the hydro dynamic pressures that act on the gravity wharf structure were also investigated

selective aerobic and anaerobic degradation of lipids and palynomorphs in the eastern mediterranean since the onset of sapropel s1 deposition abstract selective degradation of organic matter in sediments is important for reconstructing past environments and understanding the carbon cycle here we report on compositional changes between and within lipid classes and kerogen types represented by palynomorph groups in relation to the organic matter flux to the sea floor and oxidation state of the sediments since the early holocene for central eastern mediterranean site abc26 this includes the initially oxic but nowadays anoxic presapropelic interval the still unoxidised lower part of the organic rich s1 sapropel its postdepositionally oxidised and nowadays organic poor upper part as well as the overlying postsapropelic sediments which have always been oxic a general 2 3 times increase in terrestrial and marine input during sapropel formation is estimated on the basis of the total organic carbon toc pollen spore dinoflagellate cyst n alkane n alkanol and n alkanoic acid concentration changes in the unoxidised part of the sapropel the long chain alkenones 1 15 diols and keto ols loliolides and sterols indicate that some plankton groups notably dinoflagellates may have increased much more apart from the terrestrial and surface water contributions to the sedimentary organic matter anomalous distributions and preservation of some c 23 c 27 alkanes alkanols and alkanoic acids have been observed which are interpreted as a contribution by organisms living in situ comparison of the unoxidised s1 sapropel with the overlying oxidised sapropel and the organic matter concentration profiles in the oxidised postsapropelic sediments demonstrates strong and highly selective aerobic degradation of lipids and palynomorphs there seems to be a fundamental difference in degradation kinetics between lipids and pollen which may be possibly related with the absence of sorptive preservation as a protective mechanism for palynomorph degradation the n alkanes impagidinium and nematosphaeropsis are clearly more resistant than toc the n alkanols and n carboxylic acids are about equally resistant whereas the pollen all other dinoflagellate cysts and other lipids appear to degrade considerably faster which questions the practice of normalising to toc without taking diagenesis into account selective degradation also modifies the relative distributions within lipid classes whereby the longer chain alkanes alcohols and fatty acids disappear faster than their shorter chain equivalents accordingly interpretation of lipid and palynomorph assemblages in terms of pre or syndepositional environmental change should be done carefully when proper knowledge of the postdepositional preservation history is absent two lipid based preservation proxies are tested the diol keto ol oxidation index based on the 1 15c 30 diol and keto ols doxi and the alcohol preservation index api whereby the former seems to be the most promising

palynological evidence for late quaternary climate and marine primary productivity changes along the california margin a high resolution sedimentary record of dinoflagellate cysts from ocean drilling program hole 1017e off point conception california margin reflects how marine primary productivity has changed in response to major shifts in climate and ocean circulation along the california margin over the past 42 kyr throughout the studied sequence dinoflagellate cyst assemblages are dominated by upwelling related taxa signifying the continued presence of coastal upwelling on the margin during the late quaternary the cyst record suggests that marine primary productivity was enhanced during the holocene and bolling and to a lesser extent during the late glacial and most dansgaard oeschger events while an apparent reduction in primary productivity can be seen during the younger dryas the best analogue technique based on a modern dinoflagellate cyst assemblage database from the northeast pacific was used for quantitative reconstruction of past sea surface conditions it points to dynamic changes in annual marine primary productivity 235 331 g c m 2 yr 1 and sea surface temperature 10 1 12 6 c in winter 13 1 14 3 c in summer while sea surface salinity appears to be confined to a narrower range 32 9 33 4 in summer our results also indicate noticeable climate variability during the holocene in this region

evolution and variability of the asian monsoon system state of the art and outstanding issues the asian monsoon is comprised of the indian and east asian subsystems these two components are linked to one another in varying degrees by regions of strong sensible heating indo asian landmass and strong latent heat export the western pacific warm pool and the southern subtropical indian ocean variability within the indian and east asian subsystems interactions among them and the extent to which they interact with other climate phenomena e g enso are current topics of modern and paleoclimate research this work provides an overview of past and current paleomonsoon research on tectonic to interannual time scales with a primary focus on marine sediment records while past and current work has contributed greatly to our understanding of paleomonsoon variability at all time scales additional efforts are required to make further progress in two critical areas 1 additional efforts are needed in terms of proxy development and evaluation requiring concerted efforts at long term sediment trap deployments in key monsoon influenced regions as well as development of adequate and widely available core top databases these are necessary to assess the impact of modern oceanographic and seafloor processes on potential monsoon proxies 2 additional effort is also needed in acquiring a sufficient geographic distribution of downcore records to assess linkages among the subsystems and their role in the context of extratropical climate change these records should have high sedimentation rates including varved sections this requires substantial survey support to identify the most appropriate coring and drilling targets c 2004 elsevier ltd all rights reserved

holocene climate history of the nunatsiavut northern labrador canada established from pollen and dinoflagellate cyst assemblages covering the past 7000 years this study documents the past 7000 years of holocene climatic history for labrador and nunatsiavut using a sedimentary sequence of more than 8 m retrieved in nachvak fjord one of the northernmost fjords of nunatsiavut using a multi proxy approach combining a solid accelerator mass spectrometry ams 14c chronology and the fossil assemblages of pollen grains and dinoflagellate cysts dinocysts we were able to compare terrestrial and marine records in an effort to obtain a better understanding of the mid to late holocene climate history of the nunatsiavut records begin at the end of the deglaciation and showed a general delay in the sequence of climate events which followed both in terrestrial and marine realms the presence of pentapharsodinium dalei in great abundance in nachvak fjord revealed a strong influence of the north atlantic ocean and the labrador sea until 3000 yr bp afterward its rather fast disappearance marked the increased influence of arctic waters the last 1000 years show clim

comparison of qualitative and quantitative dinoflagellate cyst approaches in reconstructing glacial interglacial climate variability at west iberian margin iodp shackleton site u1385 abstract dinoflagellate cysts dinocysts are commonly used to reconstruct past environmental conditions at the sea surface such as primary production temperature and salinity abundances of selected dinocyst taxa are used in qualitative indices whereas the modern analogue technique mat is used for quantitative reconstructions qualitative indices use process based knowledge of present day relations between the environmental variables and the distribution of dinocysts whereas the mat is based on the assumption that past assemblages have modern counterparts that correspond to similar sea surface conditions here we explore the potential of both approaches to reconstruct sea surface temperature sst production ssp salinity sss and seasonality during the last 22 thousand years along the west iberian margin wim at integrated ocean drilling program iodp site u1385 we compare results to published paleoclimatic reconstructions our sst and sss reconstructions provide the first continuous dinocyst mat based sst and sss records for this area and time interval qualitative and quantitative dinocyst based sst estimates from the wim are similar and resemble previous sst estimates from dinocysts alkenones and foraminifers from nearby sites the surface temperature trends and millennial scale variations largely match those from the greenland ice core records quantitative mat based sst estimates show increased seasonality in the glacial stage resulting from strong winter cooling dinocyst mat based salinity decreases concomitantly with cooling during the younger dryas and heinrich stadial 1 hs1 likely related to the melting of icebergs that reached the region during hs1 our qualitative and quantitative ssp estimates show higher values in the glacial stage compared to the holocene which is consistent with published records and supports the usefulness of both approaches small differences between sst tracer records may be explained by the limited number of modern analogues from warm ocean regions in the dinocyst reference dataset for mat the small number of dinocysts used in the qualitative estimates the possible effect of a parameter other than temperature that might amplify noise and or seasonal biases of the tracer species in any case the advantage of the qualitative approach is to allow reconstructions in non analogue situations regression of the qualitative index versus present day sst also allows for a quantitative reconstruction although over a limited range of ssts especially towards the lower end and with quite some uncertainty but produces reasonable values beyond the upper limit of the mat the mat reconstructs more reliable ssts with a much smaller error of prediction but only up to present day wim values because it is based on the assumption that past assemblages have modern counterparts that correspond to similar sea surface conditions which is not always valid the advantages of the mat approach include its quantitative nature and insights into seasonality hence both approaches are complementary at site u1385 mat can be used for reconstructions in the colder periods yd hs1 and glacial stage with a small error of prediction and the quantified index can be used to estimate sst beyond the limit of the mat holocene and b a

permeability and stiffness of sands at very low effective stresses loose saturated sandy soils may undergo liquefaction under cyclic loading generating positive excess pore pressures due to their contractile nature and inability to dissipate pore pressures rapidly during earthquake loading these liquefied soils have a near zero effective stress state and hence have very low strength and stiffness causing severe damage to structures founded upon them the duration for which this near zero effective stress state persists is a function of the rate of reconsolidation of the liquefied soil which in turn is a function of the permeability and stiffness of the soil at this very low effective stress existing literature based on observation of physical model tests suggests that the consolidation coefficient cv associated with this reconsolidation of liquefied sand is significantly lower than that of the same soil at moderate stress levels in this paper the results of a series of novel fluidisation tests in which permeability k and coefficient of consolidation cv were indep