deposition and modification of a flood layer on the northern california shelf lessons from and about the fate of terrestrial particulate organic carbon the 1995 flood of the eel river in northern california provided an opportunity to follow the short term history of riverine particulate matter on a continental shelf particulate organic carbon including both vascular plant debris and soil carbon was utilized as a tracer of the distribution and modification of the shelf flood deposit these components were sorted during initial emplacement of the deposit both in the river plume and in the benthic boundary layer during the 8 months following the flood lateral transport shallow burial and bioturbation contributed to spatial changes in the amount and character of carbon in the flood deposit study of the deposit suggests that this and previous flood layers may be preserved in the shelf and upper slope stratigraphic record as clay rich beds with relatively high carbon to nitrogen ratios and more negative 13c values than background non flood sediment concentrations of vascular plant debris are locally characteristic of such layers and may serve as distinctive stratigraphic markers investigation of organic carbon in the 1995 flood layer on the eel river shelf provides insight into the fate of terrestrial particulate carbon on continental margins in general flooding of the eel river and of similar river systems draining mountainous terrains introduces large quantities of terrestrial carbon to the marine environment and may favor the preservation of both terrestrial and marine carbon the abundant woody vascular plant debris discharged during floods is especially likely to survive oxidation and sulfate reduction in the shallower zones of the seabed this study reveals the dominant role that physical and biological processes may play in attenuating the terrestrial organic carbon signal on shelves over monthly to yearly time scales

the indian monsoon and its variability for over 300 years the monsoon has been viewed as a gigantic land sea breeze it is shown in this paper that satellite and conventional observations support an alternative hypothesis which considers the monsoon as a manifestation of seasonal migration of the intertropical convergence zone itcz with the focus on the indian monsoon the mean seasonal pattern is described and why it is difficult to simulate it is discussed some facets of the intraseasonal variation such as active weak cycles break monsoon and a special feature of intraseasonal variation over the region namely poleward propagations of the itcz at intervals of 2 6 weeks are considered vertical moist stability is shown to be a key parameter in the variation of monthly convection over ocean and land as well as poleward propagations special features of the bay of bengal and the monsoon brought out by observations during a national observational experiment in 1999 are briefly described

the ages of fractures in the eye dashwa pluton atikokan canada ages of fractures in the eye dashwa granite pluton north of atikokan ontario are estimated from analyses of their filling materials pegmatite aplite hornblendeporphyry epidote chlorite gypsum diabase iron oxides carbonate and clays the analyses include radiometric age determinations of filling materials comparison of crystallization temperatures of filling materials with the expected temperature of the pluton through time and paragenetic relations derived from textures the major fractures primarily epidote and chlorite filled were produced by penetrative deformation during cooling immediately after intrusion of the pluton from 2 6 ga to 2 4 ga they transected the pluton and largely defined the present overall fracture network less severe penetrative deformation occurred about 1 1 ga when a few diabase dikes and small gypsum fractures developed a second source of fracturing appears to have existed through most of geological time and it reopened segments of old fractures within about 400 m of the present erosional surface it is unknown whether the near surface or supergene fractures formed more or less continuously through time or in distinct episodes such as during glacial periods open fractures which are most common in the near surface layer tend to transmit groundwater but fracture sealing due to the accumulation of filling materials seems to occur with time underground excavations such as nuclear fuel waste disposal vaults would be less susceptible to the incursion of groundwater if they were located below the near surface layer

mapping of apparent magnetic susceptibility and the identification of fractures a case study from the eye dashwa lakes pluton atikokan ontario in situ magnetic susceptibility measurements are only possible on outcrops which are often limited by overburden and water bodies an alternative approach is to derive an apparent susceptibility map from total magnetic intensity tmi surveys which was done in this study for the eye dashwa lakes pluton near atikokan ontario susceptibility logs of cores directly link alteration to systematic changes in the amount and composition of magnetic minerals the surficial distribution of alteration zones was originally estimated from a limited number of in situ magnetic susceptibility measurements here through forward modeling of the tmi data set susceptibility data are used to validate the apparent susceptibility data set the modeling accounts for the bathymetric surface of all lakes that cover the area a two step process of bulk and local scale modeling was used to estimate apparent susceptibility patterns bulk magnetic susceptibility is used as an indicator of overall alteration content and local scale apparent magnetic susceptibility values are computed using a forward modeling routine the new apparent magnetic data set indicates northwest and northeast linears which are the same as those seen in previous studies

spatial variability in sedimentary processes on the eel continental slope the northern california continental margin receives episodically large quantities of sediment from the eel river which seasonally discharges to the shelf regional circulation broadcasts this sediment widely not only affecting sedimentation on the shelf but on the slope as well a suite of 60 cores has been collected to examine the processes of sediment accumulation and sediment delivery to the eel continental slope in waters 800 m deep spatial surveys of accumulation rate 0 2 1 3 g cm 2 year 1 and surficial sediment grain size 4 8 5 demonstrate that sediment is accumulating throughout the eel margin reflecting a rapid and widespread redistribution of the fluvial discharge downcore grain size profiles of heterogeneous sediments suggest that hemipelagic and other episodic sediment delivery processes may be important for the slope in areas proximal to the river in more distal areas downcore profiles reveal relatively homogeneous sediments delivered dominantly by hemipelagic processes a budget for fine grained sediment shows that this upper portion of the slope contains at a maximum 20 of the river s annual discharge a combined budget for the shelf and upper slope suggests that at least 60 of the annual sediment load is not accounted for in these areas the eel continental slope because of the large terrigenous sediment input the narrow width of the adjacent shelf and its energetic environment is a good analogue for slopes during transitional stands of sea level and for modern tectonically active settings processes typically associated with these geological settings i e supply of sediment to the slope and downslope mass movement are actively occurring 1999 elsevier science b v all rights reserved

community benthic paleoecology from high resolution climate records mollusca and foraminifera in post glacial environments of the california margin abstract paleoecological reconstructions of past climate are often based on a single taxonomic group with a consistent presence less is known about the relationship between multi taxon community wide change and climate variability here we reconstruct paleoecological change in a late quaternary 16 1 3 4 ka sediment core from the california margin 418 m below sea level of santa barbara basin sbb usa using mollusca animalia and foraminifera rhizaria microfossils building upon previous investigations we use multivariate ordination and cluster analyses to interpret community scale changes in these distinctly different taxonomic groups across discrete climate episodes the strongest differences between seafloor biological communities occurred between glacial prior to termination ia 14 7 ka and interglacial climate episodes holocene communities were well partitioned indicating that sub millennial oceanographic variability was recorded by these microfossils we document strong evidence of chemosynthetic trophic webs and sulfidic environments from gastropod alia permodesta and bivalve lucinoma aequizonata which characterized restricted intervals previously interpreted as well oxygenated such as the pre bolling warming mollusc records indicate first order trophic energetic shifts between detrital and chemosynthetically fixed carbon molluscs associated with widely different physiological preferences occur here within single decadal intervals of sediment and as such mollusc assemblages may reflect significant inter decadal oceanographic variability foraminifera assemblages provide exceptional records of the sequential chronological progression of the deglacial climatic and oceanographic events whereas mollusc assemblages reflect non chronological similarities in reoccurring communities foraminifera taxa that drive community similarity here are also independently recognized as marker species for seafloor hypoxia regimes which provides support for the idea that oxygenation change is a principal driver of seafloor environmental variability

a study of rock alteration in the eye dashwa lakes pluton atikokan northwestern ontario canada abstract as a part of the research pertaining to evaluation of the suitability of crystalline rocks for the disposal of nuclear fuel waste a study of core samples from five boreholes in the eye dashwa lakes pluton reveals several types and degrees of alteration the different degrees of alteration are related to the intensity of pink coloration and the amounts of plagioclase and ferromagnesian minerals that are affected the alteration process has reconstituted plagioclase to pure albite in highly altered rocks whereas in unaltered and slightly altered rocks it occurs as oligoclase the alteration products chlorite and sericite are relatively fe rich in the highly altered rocks unaltered to slightly altered moderately altered and highly altered samples each occupy a distinct field in a cao mgo feo variation diagram a close association exists between alteration and fractures a model relating fractures alteration and fracture infillings is proposed distinct differences in chemical and some physical properties between altered and unaltered rocks indicate that significant changes have occurred the distinct physical and chemical characteristics of the alteration and its close association with faults and fractures suggest the need to consider alteration as an important parameter in evaluating crystalline rocks for nuclear fuel waste disposal

multiple alteration events in the east bull lake anorthosite gabbro layered complex ne ontario canada evidence from fracture mineralogy and40ar 39ar dating abstract the east bull lake anorthosite gabbro layered complex contains a variety of alteration minerals some of the more common ones are calcic amphiboles biotite epidote adularia quartz chlorite calcite prehnite pumpellyite laumontite gypsum iron hydroxides and clays the mode of occurrence and the data related to the stability of the alteration minerals suggest that they were formed under pressure temperature conditions of 1 epidote amphibolite greenschist facies 2 prehnite pumpellyite facies 3 zeolite facies and 4 low temperature mineral facies 40 ar 39 ar data of hornblende and adularia indicate that the pluton is affected by distinct alteration events two mafic dyke intrusions that overlap the alteration events are recognised in the pluton synthesis of available radiometric ages suggests that the pluton intruded at 2472 70ma and was subjected to alteration as late as the paleozoic and cenozoic eras

macrofaunal communities associated with chemosynthetic habitats from the u s atlantic margin a comparison among depth and habitat types abstract hydrocarbon seeps support distinct benthic communities capable of tolerating extreme environmental conditions and utilizing reduced chemical compounds for nutrition in recent years several locations of methane seepage have been mapped along the u s atlantic continental slope in 2012 and 2013 two newly discovered seeps were investigated in this region a shallow site near baltimore canyon bcs 366 412 m and a deep site near norfolk canyon ncs 1467 1602 m with both sites containing extensive chemosynthetic mussel bed and microbial mat habitats sediment push cores suction samples and ekman box cores were collected to quantify the abundance diversity and community structure of benthic macrofauna 300 m in mussel beds mats and slope habitats at both sites community data from the deep site were also assessed in relation to the associated sediment environment organic carbon and nitrogen stable carbon and nitrogen isotopes grain size and depth infaunal assemblages and densities differed both between depths and among habitat types macrofaunal densities in microbial mats were four times greater than those present in mussel beds and slope sediments and were dominated by the annelid families dorvilleidae capitellidae and tubificidae while mussel habitats had higher proportions of crustaceans diversity was lower in bcs microbial mat habitats but higher in mussel and slope sediments compared to ncs habitats multivariate statistical analysis revealed specific sediment properties as important for distinguishing the macrofaunal communities including larger grain sizes present within ncs microbial mat habitats and depleted stable carbon isotopes 13c in sediments present at mussel beds these results suggest that habitat differences in the quality and source of organic matter are driving the observed patterns in the infaunal assemblages including high diversity and high variability in the macrofaunal community composition this study is the first investigation of seep infauna along the u s atlantic slope north of the blake ridge diapir and provides a baseline for future regional comparisons to other seep habitats along the atlantic margin

methane cold seeps as biological oases in the high arctic deep sea cold seeps can support unique faunal communities via chemosynthetic interactions fueled by seabed emissions of hydrocarbons additionally cold seeps can enhance habitat complexity at the deep seafloor through the accretion of methane derived authigenic carbonates mdac we examined infaunal and megafaunal community structure at high arctic cold seeps through analyses of benthic samples and seafloor photographs from pockmarks exhibiting highly elevated methane concentrations in sediments and the water column at vestnesa ridge vr svalbard 79 n infaunal biomass and abundance were five times higher species richness was 2 5 times higher and diversity was 1 5 times higher at methane rich vestnesa compared to a nearby control region seabed photos reveal different faunal associations inside at the edge and outside vestnesa pockmarks brittle stars were the most common megafauna occurring on the soft bottom plains outside pockmarks microbial mats chemosymbiotic siboglinid worms and carbonate outcrops were prominent features inside the pockmarks and high trophic level predators aggregated around these features our faunal data visual observations and measurements of sediment characteristics indicate that methane is a key environmental driver of the biological system at vr we suggest that chemoautotrophic production enhances infaunal diversity abundance and biomass at the seep while mdac create a heterogeneous deep sea habitat leading to aggregation of heterotrophic conventional megafauna through this combination of rich infaunal and megafaunal associations the cold seeps of vr are benthic oases compared to the surrounding high arctic deep sea

measurements of transience and downward fluid flow near episodic methane gas vents hydrate ridge cascadia aqueous flux measurements within cold seep regions on northern hydrate ridge cascadia indicate a high degree of variability with extended periods of downflow and reversals of flow direction over periods of weeks to months local episodic venting of free methane gas was also observed the instruments recorded similar changes in hydrologic flow patterns both on and off clam fields the magnitude of the flow rates decreasing away from the clam field the coincidence of episodic gas venting with nearby highly variable aqueous fluid flow suggests that they may be coupled we propose that these observations are consistent with the action of a gas driven pump that operates somewhat like a geyser the hypothesis of gas driven pumping of seawater through northern hydrate ridge has important ramifications for the mass fluxes through this region

early fracture evolution within the eye dashwa lakes pluton atikokan ontario canada abstract the fracture history of part of the eye dashwa lakes pluton near atikokan ontario was investigated from drill core and surface fracture data the earliest fractures contain aplite and compose less than 5 of the population they developed during the initial stages of plutonic cooling and contraction in response to local magma related pressures internal pressures decreased as the pluton cooled subsequent fractures comprising more than 90 of the population formed soon afterwards under the influence of a regional subhorizontal nw se compression statistical analysis and field evidence indicate that subhorizontal and moderately dipping dip slip fractures are filled mainly with epidote these were followed by formation of steeply dipping to subvertical strike slip fractures that are filled mainly with chlorite the resulting fracture framework was well established by the end of the archaean minor stress changes since then have rejuvenated the old fracture zones rather than creating new zones

strontium isotopic composition of some brines from the precambrian shield of canada abstract twenty four groundwater samples from seven operating mines at sudbury yellow knife and thompson ontario north west territories and manitoba resp all from depths greater than 1 km and ranging in total dissolved solids tds from 1900 to 250 000 mg l 1 were measured for their 87 sr 86 ar values each geographic location gives a limited range in values and each location is distinct from the others this is interpreted as the result of extensive water rock interaction on a local scale for most of the time these brines were isolated and only recently have been exposed to surface water as a result of the mining operations the extent of the isolation is shown by the contrasting isotopic values of two pockets of water 0 711 vs 0 716 located on opposite sides of the same fault system on the north range at sudbury the exchange at all sites probably has continued until the present as indicated by the close agreement between water and present day 87 sr 86 sr whole rock values if so it suggests that there is no single age for such brines but it may be possible to date stages in the water s evolution by determining the age of secondary minerals that equilibrated with the water

mud volcanoes in the mediterranean sea are hot spots of exclusive meiobenthic species mud volcanoes are cold seeps in which the escape of gas and fluids associated with mud creates 3 d bottom structures that enhance the spatial heterogeneity and potentially alter the functioning of the benthic ecosystems we investigated a complex system of mud volcanoes of the mediterranean sea characterised by the presence of different structures i e isolated domes domes surrounded by moats clustered domes and ridges displaying different levels of seepage we hypothesize that the combined effects of seafloor heterogeneity i e different 3 d structures as revealed by detailed topographic analysis fluid emissions and trophic characteristics of these systems can influence the structural and functional biodiversity of meiofauna with special focus on the nematodes we found that sediments affected by intensive seepage displayed the lowest faunal abundances and number of higher taxa however mud volcanoes without emissions but characterized by a high structural complexity such as the ridges were associated with the highest meiofaunal abundances and number of higher taxa mud volcanoes hosted also a remarkable abundance of rare taxa specifically associated with these structures e g acarians cumaceans tanaids cladocerans and hydroids and absent in slope sediments used as a control each mud volcano area displayed a different nematode species composition overall 76 nematode species from a total of 235 were exclusively associated with mud volcano structures whilst 29 were exclusively encountered in slope sediments we conclude that the presence of mud volcanoes for their contribution to increase spatial heterogeneity and for the extreme conditions associated with gas emissions promotes higher levels of beta diversity thus enhancing the regional gamma benthic diversity these findings provide new insights on the factors controlling meiobenthic biodiversity in mud volcanoes and clues for future action of conservation of the biodiversity specifically associated with these habitats

influence of indian ocean dipole on boreal summer intraseasonal oscillations in a coupled general circulation model 1 the role of indian ocean dipole iod on poleward propagation of boreal summer intraseasonal oscillations bsiso is examined using long simulation of a coupled ocean atmosphere general circulation model the model sintex f1 simulates the salient features of bsiso realistically it is found that coherent incoherent poleward propagation of precipitation anomalies from 5 s to 25 n are observed during negative positive iod years the probable mechanisms behind such an anomaly in poleward propagation of bsiso in contrasting iod years are identified we find that the mean structure of meridional specific humidity distribution undergoes cardinal changes in contrasting iod years which in turn influences the meridional propagation of bsiso enhanced decreased air sea interaction in negative positive iod years also supports coherent incoherent poleward propagation of bsiso anomalies this study has important implications considering the critical role of bsiso in modulating the seasonal mean summer monsoon rainfall

complex flow patterns through hydrate ridge and their impact on seep biota our recent measurements of long term fluid flux rates and output fluid chemistry at seep sites on hydrate ridge cascadia suggest that the mechanisms driving fluid flow in gas hydrate bearing forearc settings may be significantly more complex than previously thought temporal changes in the polarity and magnitude of flow and in seep fluid chemistry were observed the nature of flow appears to generate a strong response in the chemosynthetic seep community ecology we document here 1 the frequency and range of temporal variability in flow rates 2 the relatively rapid changes in outflow composition 3 strong outflow of seawater like fluids 4 the association of calyptogena sp clams with oscillatory and inflow settings and 5 microbial mat communities associated with strong advection of altered fluids these results suggest that a reappraisal may be required of the nature of the hydrologic system and its effect on related processes such as benthic seep community ecology and biogeochemical cycles

gas hydrate destabilization and methane release events in the krishna godavari basin bay of bengal abstract methane release events have been linked to global warming alteration of the carbon cycle and influence on biota however unequivocal evidence of paleomethane release events are limited we report several negative carbon stable isotope excursions in planktic and benthic foraminifera in a core md161 8 from the krishna godavari k g basin bay of bengal the most negative 13 c spikes are recorded during the marine isotope stages mis 4 and at the transition of mis 5 to 4 occurrence of highly 13 c depleted average 13 c 48 2 4 vpdb authigenic high magnesian calcite are also reported within this time window from the core md161 8 in the present work an unequivocal explanation for the observed 13 c depletion in the marine planktic and benthic foraminifera is difficult to achieve solely from the optical electron microscopy or c o stable isotope ratio analyses due to possible influence of diagenetic alteration we attribute the observed episodic methane expulsion events as inferred from the negative 13 c excursions and earlier reports on the occurrence chemosynthetic bivalves and mo concentration anomaly to the destabilization of the base of gas hydrate stability zone bghsz sea level drop and shale tectonics induced focused fluid flow are the two possible causes of hydrate destabilization discussed here shale tectonics were possibly responsible for creating fault systems which acted as the conduit for gas flow through the sediment column and subsequent seepage shale and salt tectonics in the passive continental margins being a globally observed phenomenon its role as an important driving force for enhanced methane emission needs detailed investigation to understand the climatic perturbations through geologic time additional evidence of methane emission from site md161 15 further supports the link between shale tectonics and methane emission

termination of indian ocean dipole events in a coupled general circulation model abstract using 200 yr of coupled general circulation model cgcm results causes for the termination of indian ocean dipole iod events are investigated the cgcm used here is the scale interaction experiment frontier research center for global change sintex f1 model which consists of a version of the european community hamburg echam4 6 atmospheric model and a version of the ocean parallelise opa8 2 ocean general circulation model this model reproduces reasonably well the present day climatology and interannual signals of the indian and pacific oceans the main characteristics of the intraseasonal disturbances isds oscillations are also fairly well captured by this model however the eastward propagation of isds in the model is relatively fast in the indian ocean and stationary in the pacific compared to observations a sudden reversal of equatorial zonal winds is observed as a result of significant intraseasonal disturbances in the equatorial indian ocean in november december of iod events

the use of autoradiography in determining the distribution of radionuclides sorbed on thin sections of plutonic rocks from the canadian shield abstract autoradiography coupled with classical petrographic techniques has been used to determine the distribution of radionuclides sorbed under oxic conditions onto rock thin sections representative of the four major types of plutons in the canadian shield to determine which minerals are most effective in removing radionuclides from aqueous solutions kodak spectroscopic and ilford k 5 nuclear emulsion plates were investigated the ilford film was found to give higher resolution and required a shorter exposure time than the kodak film sorption was found to be negligible on quartz and strongest on the mafic minerals the pyroxenes micas hornblende and opaques and on alteration minerals chlorite and sphene precipitation of am and pm was observed indicating that for actinides and rare earths experimentally obtained static sorption coefficients may reflect precipitation as well as sorption and must be used with caution in modelling studies

review of the modelling of radionuclide transport from u series disequilibria and of its use in assessing the safe disposal of nuclear waste in crystalline rock abstract u series disequilibia from crystalline rocks and u deposits have been used to estimate the timing of hydrogeological events for u and ra mobility and to model the transport rates of u and ra both with some sucess unfortunately activity ratio data alone are not unique to a given process or model and it is shown how inappropriate choice of the model can have quite diverse consequences for interpretation of the data information from other sources is needed to help minimise these non uniqueness problems but as yet the state of methodology is unadequate to assess completely the validity of the models in particular the rate of deposition of u in fractures seems highly dependent upon the availability of trivalent fe and other low temperature minerals whose rates of formation are largely unknown this review reinforces the need to assess closely the suggestion that chemisorption is an effective retardant of fracture borne borne repository source radionuclides

the central paratethys during oligocene as an ancient counterpart of the present day black sea unique records from the coccolith limestones abstract four isochronous oligocene coccolith limestone horizons from the carpathians were examined in order to reconstruct paleoceanographic conditions in the central paratethys the dominance of small and size uniform pyrite framboids the occurrence of low diversity dinoflagellate cysts and coccolithophorids and the presence of biomarker molecule 28 30 dinorhopane indicate that the water column was stratified with the upper water column being relatively well oxygenated but the bottom water being anoxic the latter is confirmed by the fine and consistent horizontal laminations in various parts of the basin scarcity of benthic organisms and their trace fossils the limestones exhibit typical marine 13c values but are significantly depleted in 18o and enriched in 87sr relative to contemporaneous ocean water these isotopic compositions result from a decreased salinity of the surface waters caused by an increased riverine input this is confirmed by the lack or impoverishment of planktonic foraminifers presence to abundance of goniodomid dinoflagellate cysts and massive occurrence of low diversity nannoplankton assemblages which indicates decreased salinities as low as 17 and high productivity in the upper water column these observations indicate that the limestones were formed during periods when connection of the central paratethys with the global ocean was limited which impeded water exchange causing the development of low salinity conditions of surface water and bottom water anoxia during the deposition of the oldest tylawa horizon primary productivity was enhanced and chemocline was positioned exceptionally high in the water column moreover decreased 13c values in both carbonates and organic matter of this horizon suggest that widespread methane venting took place in the basin during np23 all these data show that during the oligocene the central paratethys experienced similar conditions to those of the current black sea which can be used as a modern analogue especially for the tylawa horizon therefore the tylawa horizon can be perceived as a potential effect of future post depositional processes of coccolith marls analogous to those having been deposited in the black sea for 2 7 kyr

clustering of synoptic activity by indian summer monsoon intraseasonal oscillations 1 active and break phases of the indian summer monsoon are characterized by enhancement and decrease of precipitation over the monsoon trough region using genesis data of monsoon low pressure systems lps and circulation data for the period 1954 to 1993 it is shown that the frequency of occurrence of lps is nearly 3 5 times higher in the active phase of monsoon as compared to the break phase in addition the tracks of these synoptic systems are also strongly spatially clustered along the monsoon trough during the active phase of the monsoon the enhanced decreased frequency of occurrence of lps during active break phases is due to modulation of meridional shear of zonal winds and cyclonic vorticity along the monsoon trough by the intraseasonal oscillations iso

paleoenvironmental evolution in a high stressed cold seep system vicchio marls miocene northern apennines italy abstract excellent exposures of miocene seep carbonates enclosed in marine marly sediments vicchio outcrops in the northern apennines italy offer the opportunity to highlight the evolution of a fossil seep ecosystem and the response of benthic communities to high stressed environmental conditions for this purpose seep related facies and molluscs within carbonate bodies have been studied coupled with benthic foraminiferal assemblages and carbon and oxygen isotopes in the enclosing marls the integrated planktonic foraminiferal and calcareous nannofossil biostratigraphy has allowed us to constrain the seepage within well calibrated bioevents and to stress the relationships with paleoclimatic and paleoceanographic variations during the middle miocene in the mediterranean area our biostratigraphic data indicate that the onset of the seepage approximates the mi3b cooling event 13 82 ma and the seepage system lasts for 400 kyr the evolution of the vicchio cold seep system passes through four phases 1 the onset of the seepage characterized by a pervasive flow of methane rich fluids is inferred by 13c depletion of marly sediments and by prevailing benthic foraminifera indicative of suboxic conditions at the sea floor 2 the methane flow becomes focused causing the precipitation of wide pinnacle like carbonate bodies which contain giants lucinids enclosing marls indicate well oxygenated conditions possibly enhanced by paleoceanographic variations connected to the mi3b cooling event 3 the appearance of the vesicomyid christineconcha cf c regab and the absence of lucinids in seep carbonates suggest stable methane rich fluid emissions higher flow rates locally favoured the flourishment of bacterial mats benthic foraminifera show abundance peaks of organic matter depending taxa 4 the reduced intensity of methane rich fluid flows favours the precipitation of stratiform carbonate bodies along strike the macrofauna is characterized by the presence of both vesicomyidae and giant lucinids foraminiferal assemblages in the enclosing marls indicate the restoration of well oxygenated conditions

individual and combined influences of enso and the indian ocean dipole on the indian summer monsoon the relative influences of the enso and indian ocean dipole iod events on the indian summer rainfall were studied using observational data and an atmospheric general circulation model agcm the composite analysis of rainfall anomalies demonstrates that the iod while significantly influencing the indian summer monsoon rainfall also significantly reduces the impact of enso on the indian summer rainfall whenever these events with the same phase co occur the agcm experiments have shown that during an el nino event the walker circulation over the tropical indo pacific region is modulated a low level anomalous divergence center over the western pacific and an anomalous convergence zone over the equatorial indian ocean are induced furthermore an anomalous zone of convergence over the myanmar and south china regions is induced during an el nino event these zones of anomalous convergence are complemented by anomalous divergence over the indian region causing anomalous subsidence and weakened rainfall when a strong positive iod event simultaneously occurs with el nino the latter s influence on the indian monsoon is reduced by both poles of the iod through the following mechanism an anomalous divergence center as compared to the summers when an el nino alone occurs is introduced in the eastern tropical indian ocean from this center the anomalous divergent flow crosses the equator and this air while weakening the el nino induced divergence over the western pacific also leads to convergence over the indian monsoon region this results in the reduction of the enso induced subsidence and the related rainfall deficit over the eastern flank of the indian monsoon trough region and adjoining regions to the east on the other hand over the western part of the tropical indian ocean sector part of the anomalous ascending motion from the warm pole of the positive iod event subsides just to the north of the equator moves northward ascends and causes surplus rainfall this reduces the enso induced rainfall deficit over western india the western part of the monsoon trough and parts of pakistan the agcm experiments also demonstrate that positive iod events amplify the enso induced dryness over the indonesian region

a diagram for interpreting orientation data for planar features in core abstract a new type of diagram depicts orientation data for planar structures found in drill core strike and dip of fractures intersected by a borehole are plotted independently side by side as a function of borehole length these companion plots show variations in distribution and orientation of fractures the diagram is used to establish boundaries between fracture domains and to interpret a sequence of fracturing based on the spatial relationship between domains comprising different fracture patterns

cold seep and oxygen minimum zone associated sources of margin heterogeneity affect benthic assemblages diversity and nutrition at the cascadian margin ne pacific ocean abstract hydrate ridge hr located on the northeastern pacific margin off oregon is characterized by the presence of outcropping hydrates and active methane seepage additionally permanent low oxygen conditions overlay the benthic realm this study evaluated the relative influence of both seepage and oxygen minima as sources of habitat heterogeneity and potential stress inducing features on the bathyal metazoan benthos primarily nematodes at three different seep and non seep hr locations exposed to decreasing bottom water oxygen concentrations with increasing water depth the nematode seep communities at hr exhibited low diversity with dominance of only one or two genera daptonema and metadesmolaimus elevated average individual biomass and 13c evidence for strong dependance on chemosynthesis derived carbon resembling deep sea seeps worldwide although the hr seep habitats harbored a distinct nematode community like in other known seep communities they differed from deep sea seeps in well oxygenated waters based on that they shared the dominant genera with the surrounding non seep sediments overlain by oxygen deficient bottom water the homogenizing effect of the oxygen minimum zone on the seep nematode assemblages and surrounding sediments was constant with increasing water depth and concomitant greater oxygen deficiency resulting in a loss of habitat heterogeneity

isotopic evidence for chemosynthesis based nutrition of macrobenthos the lightness of being at pacific methane seeps the importance of chemosynthetic nutritional pathways was examined for macrofaunal invertebrates 300 mm from methane seeps in the gulf of alaska 4 413 4 443 m on the oregon margin 590 m and on the northern california slope eel river margin 520 m by use of natural abundance stable isotopic data seep macrofauna exhibited lighter d 13 c and d 15 n values than those in nonseep sediments but isotopic signatures varied among seep sites macrofaunal isotopic signatures indicated chemosynthetically fixed carbon sources with a significant contribution from methane derived carbon mdc in macrofauna from sediments of pogonophoran fields averaged 13

the role of seawater freezing in the formation of subsurface brines abstract several mechanisms evaporation water rock interaction ultra filtration have been suggested to explain the evolution of ubiquitous ca chloride subsurface brines in the present paper the freezing of seawater in polar regions and in even wider areas during glacial periods is proposed as an additional possible path of brine formation four detailed seawater freezing experiments to 14 c resulting in a concentration factor of about 5 were carried out and na k ca mg sr cl so4 and br were analysed in the residual brines and in the ice br and sr whose behavior during the freezing of seawater is reported here for the first time show a conservative behavior throughout the studied temperature range our data and earlier literature show that the high salinities which are common in subsurface brines 300 g l may be obtained by the removal of h2o as ice in the primary glacial environment the decrease in the na cl ratio is caused by the crystallization of mirabilite na2so4 10h2o supplemented by hydrohalite nacl 2h2o sulfate is removed both in mirabilite and by bacterial reduction the brine then migrates to the subsurface heats up under the local geothermal gradient and interacts with the adjacent rocks at this stage it may be diluted by meteoric waters its mg ca ratio decreases dolomitization and chloritization the so 4 cl ratio varies according to the local gypsum anhydrite equilibrium conditions and the ca so 4 hco 3 ratio increases as a result of dolomitization or chloritization the interaction with rocks in the subsurface may affect both the original 87 sr 86 sr and the 18 o 16 o ratios of the brine although several of the processes which lead to the formation of ca chloride brines are common for both the evaporative and the freezing models the na br cl relationship in a given brine can be used to discriminate between the two modes of brine evolution several subsurface brines from the canadian shield and one brine from finland are used as examples of the seawater freezing model and an explanation is proposed for the necessary mass production of brines in glacial environments

effects of air sea coupling on the boreal summer intraseasonal oscillations over the tropical indian ocean the effects of air sea coupling over the tropical indian ocean tio on the eastward and northward propagating boreal summer intraseasonal oscillation bsiso are investigated by comparing a fully coupled ctl and a partially decoupled indian ocean pdio experiment using sintex f coupled gcm air sea coupling over the tio significantly enhances the intensity of both the eastward and northward propagations of the bsiso the maximum spectrum differences of the northward eastward propagating bsiso between the ctl and pdio reach 30 25 of their respective climatological values the enhanced eastward northward propagation is related to the zonal meridional asymmetry of sea surface temperature anomaly ssta a positive ssta appears to the east north of the bsiso convection which may positively feed back to the bsiso convection in addition air sea coupling may enhance the northward propagation through the changes of the mean vertical wind shear and low level specific humidity the interannual variations of the tio regulate the air sea interaction effect air sea coupling enhances reduces the eastward propagating spectrum during the negative indian ocean dipole iod mode positive indian ocean basin iob mode and normal years during positive iod and negative iob years such phase dependence is attributed to the role of the background mean westerly in affecting the wind evaporation sst feedback a climatological weak westerly in the equatorial indian ocean can be readily reversed by anomalous zonal sst gradients during the positive iod and negative iob events although the ssta is always positive to the northeast of the bsiso convection for all interannual modes air sea coupling reduces the zonal asymmetry of the low level specific humidity and thus the eastward propagation spectrum during the positive iod and negative iob modes while strengthening them during the other modes air sea coupling enhances the northward propagation under all interannual modes due to the persistent westerly monsoon flow over the northern indian ocean

oxygen minimum zone biotic baseline transects for paleoceanographic reconstructions in santa barbara basin ca abstract we describe modern ocean floor biological trends employing exploratory remotely operated vehicle rov hercules dives in the santa barbara basin california usa through the nautilus exploration program using rov videos in situ measurements and sediment cores we described oxygenation temperature biological zonation and bulk sediment 15n across three 120 meter vertical transects from 380 to 500 m m that cross the depth of the ventilating sill 475 m and upper omz boundary these observations revealed major changes in the distribution of biota tied largely to changes in dissolved oxygen concentration upward increases in oxygen and temperature were coincident with successive disappearance and appearance of megafauna and foraminifera species and overall increases in community diversity the most significant and abrupt change in seawater measurements biological communities sediment textures and nitrogen isotopes were observed near the depth of the ventilating sill from 480 to 450 m microbial mats were observed up to the depth of 475 m dense populations of alia permodesta were identified at depths where dissolved oxygen o2 was

isotopic composition of uranium and thorium in crystalline rocks the 238u 234u 230th 232th system has been investigated in 84 silicic crystalline rocks obtained from drill cores surface and near surface samples in california wyoming colorado and illinois results of these analyses displayed on ternary diagrams with apexes for 238u 234u and 230th indicate five predominant geochemical processes that affected uranium in the rock 1 bulk uranium leaching where 238u and 234u were removed with little or no fractionation 2 preferential 234u leaching by alpha recoil displacement 234u recoil loss with lesser 238u loss 3 234u recoil loss with little or no 238u loss 4 uranium assimilation where both 238u and 234u were added with present day 234u 238u activity ratios varying from 0 8 to 1 2 and 5 addition of 234u and 230th by daughter emplacement processes 234u 230th recoil gain evidence for the existence of 234u and 230th recoil gain in rocks is the most important finding of this investigation radioactive disequilibrium occurs in the majority of rocks analyzed where 234u recoil loss is the predominant process associated with incipient weathering u assimilation and 234u 230th recoil gain occur under conditions of substantial water penetration along fractures and into weathered zones in the rocks relatively unfractured and petrographically fresh rocks from the uph 3 drill hole in northern illinois are closest to being in radioactive equilibrium for any suite of rocks included in this study and they demonstrate that equilibrium during the last 0 5 m y can be maintained over a substantial vertical distance where there has been little or no movement of water in the basement rock the 238u 234u 230th system can be a sensitive indicator of geologically recent u mobility and rock water interaction both in petrographically fresh core samples and in sealed fracture zones

hydrate ridge a natural laboratory for the study of microbial life fueled by methane from near surface gas hydrates hydrate ridge cascadia convergent margin is characterized by abundant methane hydrates at and below the seafloor active venting of fluids and gases chemosynthetic communities composed of giant sulfide oxidizing bacteria and clams authigenic carbonates and some of the highest methane oxidation rates ever found in the marine environment fluid flow rates vary over six orders of magnitude among closely spaced settings at the crest of hydrate ridge the distribution of benthic communities is mainly related to the sulfide flux from the subsurface sediments produced by anaerobic oxidation of methane aom even at high flux rates aom removes most of the methane seeping from the subsurface less than 50 of the methane escapes from bacterial mats from calyptogena fields 15 and from acharax beds no methane is emitted to the water column the precipitation of carbonate derived from aom is a significant and permanent carbon sink hence compared to the amount of gas hydrates and methane derived carbonates stored at the summit of hydrate ridge the emission of methane is relatively low due to the efficient filtering capacity of methanotrophic microbial communities this present review updates current knowledge of the geology of hydrate ridge summarizes recently published data on geomicrobiology and biogeochemistry and derives a local methane budget

sulfur isotope geochemistry of fracture filling gypsum in an archean granite near atikokan ontario canada abstract gypsum occurs as fracture filling material in the eye dashwa lakes pluton near atikokan ontario sulfur isotope analyses and mode of occurrence indicate that the gypsum is probably of precambrian age even though associated calcite veins indicate a minimum age of 40 000 yr petrographic analysis suggests that the gypsum was formed by the interaction of porewater with epidote plagioclase and pyrite gypsum occurs in fractures at depths 500 m where it has remained in stable equilibrium since its formation the significance of its occurrence is examined with reference to implications for the disposal of nuclear fuel waste in crystalline rocks heat generated by nuclear fuel waste in a storage vault could cause dissolution of gypsum filling material and reopen the fractures however the impermeable nature of the gypsum filled fractures and their stable equilibrium at depths 500 m may provide a method of sealing open fractures

boreal summer quasi monthly oscillation in the global tropics the boreal summer intraseasonal oscillation iso in the global tropics is documented here using a 7 year suite 1998 2004 of satellite measurements a composite scenario was made of 28 selected events with reference to the oscillation in the eastern equatorial indian ocean eio where the oscillation is most regular and its intensity is indicative of the strength of the subsequent northward propagation the average oscillation period is about 32 days and this quasi monthly oscillation qmo is primarily confined to the tropical indian and pacific oceans topics that were investigated are the partition of convective versus stratiform clouds the vertical structure of precipitation rates and the evolution of cloud types during the initial organization and the development of intraseasonal convective anomalies in the central indian ocean during the initiation of the convective anomalies the stratiform and convective rains have comparable rates the prevailing cloud type experiences a trimodal evolution from shallow to deep convection and finally to anvil and extended stratiform clouds a major northwest southeast slanted rainband forms as the equatorial rainfall anomalies reach sumatra and the rainband subsequently propagates northeastward into the west pacific ocean the enhanced precipitation in the west pacific then rapidly traverses the pacific along the intertropical convergence zone meanwhile migrating northward to the philippine sea a seesaw teleconnection in rainfall anomalies is found between the southern bay of bengal 5 15 n 80 100 e and the eastern pacific 5 15 n 85 105 w local sea surface temperature sst rainfall anomalies display a negative simultaneous correlation in the off equatorial regions but a zero correlation quadrature phase relationship near the equator we propose that atmosphere ocean interaction and the vertical monsoon easterly shear are important contributors to the northeastward propagation component of the intraseasonal rainband the observed evidence presented here provides critical information for validating the numerical models and it supports the self induction mechanism theory for maintenance of the boreal summer iso

fractures and fracture infillings of the eye dashwa lakes pluton atikokan ontario fractures in the eye dashwa pluton near atikokan ontario can be subdivided on the basis of their filling materials these materials include aplite epidote chlorite and gypsum carbonate clay listed in order of decreasing age established from crosscutting relations textures indicate that infilling occurred during fracture growth continuous cooling of the pluton during fracturing is inferred from the expected crystallization temperatures of fillings fracturing began before the pluton was completely solidified 650 600 c and continued to temperatures below 100 c many fractures appear to have been sealed by the filling materials after initiation but were subsequently sheared and filled by lower temperature materials apparently the majority of fractures formed during or immediately after pluton solidification and new fractures became smaller and more restricted in location as cooling progressed fractures and filling materials are seen as important features in assessing the possibility of movement

biotite chloritization process in hydrothermally altered granites abstract chloritization of biotite in a hydrothermal environment was studied in two granitic rocks of the massif central france four types of transformation were observed 1 mg chlorite growth upon 001 biotite planes in contact with quartz 2 biotite pseudomorphosed by a corrensite residual biotite assemblage 3 corrensite residual biotite pseudomorphosed by a ferromagnesian chlorite and 4 biotite pseudomorphosed by chlorite these transformations induce an expansion of the site of the ferromagnesian minerals which can be observed by the corrosion of neighbouring minerals and fracturation of the rock around the new chlorites open fractures or chloritic veinlets if al is considered as a strictly inert component the reaction biotite chlorite produces a decrease of the ferromagnesian mineral volume of 13 ferry 1979 this is not in agreement with petrographic observations of the rocks studied here therefore writing of a chloritization reaction must take into account a volume increase in this case al does not behave as an inert component but as a mobile one at the scale of the microsystem biotite neighbouring crystals albitization of plagioclase which occurs simultaneously with the chloritization process is the al furnisher in addition fe and mg must be brought into the microsystem during the transformation of biotite into chlorite this explains why the mg mg fe ratio is not the same between biotite chlorite growths and chlorite pseudomorphs because the bulk rock composition is enriched in these components the hydrothermal fluids must contain fe and mg before they flow into the rock chloritization in propylitized granites is not an isochemical process

cyclic deformation and chemical transport in the folson lake fault zone east bull lake anorthosite gabbro complex evidence for seismic pumping abstract the east bull lake anorthosite gabbro a late archean 2472 24ma magmatically layered lopolith at the southern margin of the superior province has experienced regional retrograde metamorphism and is transected by the folson lake fault zone a structure of regional extent the fault zone displays repeated episodes of ductile brittle deformation and vein development it has been extensively metasomatized in domains marked by the sequential development of quartz adularia epidote chlorite laumontite calcite and clay fe oxyhydroxide downhole geochemical profiles through the fault zone show coherent patterns for zr hf zr th ta nb and cr co ni which are interpreted to reflect variations in primary igneous compositions by alteration insensitive elements metasomatism is marked by peaks of sio2 k2o or na2o with al2o3 fe mn and mg and ca plus volatiles corresponding to domains of quartz adularia or albite chlorite and laumontite plus calcite respectively the analogue elements th and u are present at uniformly low levels averaging 1 1 and 0 4 ppm respectively thorium covaries with zr such that variations of abundance reflect primary differences whereas th u ratios scatter between 1 5 to 10 indicating minor remobilization of u strontium has been extensively redistributed within the fault zone and cs covaries with k retrograded areas of the pluton have whole rock 18 values ranging between 4 5 and 7 2 per mil both below and above primary values of 5 7 per mil indicating open system behaviour during regional retrograde metamorphism within the fault zone hydrothermal reservoirs involved in later k metasomatism were at temperatures of 150 250 c where 18 o h2o 2 6 to 1 7 per mil likely representing isotopically and chemically evolved deep pore fluids expelled during crustal activity related to tectonic processes in the nearby grenville province calcite and laumontite developed by the advection through the fault zone of ca rich thermal brines at temperatures around 50 200 c where 18oh2o 15 to 0 per mil such fluids were evolved formation brines with a major component of meteoric h2o expelled in the lower paleozoic the multiple deformation metasomatism events are interpreted in terms of episodic seismic pumping on a fault that was intermittently active over a time scale in excess of 1 ga

food web structure of seep sediment macrobenthos from the gulf of mexico abstract the slope environment of the gulf of mexico gom supports dense communities of seep megafaunal invertebrates that rely on endosymbiotic bacteria for nutrition seep sediments also contain smaller macrofaunal invertebrates whose nutritional pathways are not well understood using stable isotope analysis we investigate the utilization of chemosynthetically fixed and methane derived organic matter by macrofauna biological sampling was conducted in three lower slope gom seep environs green canyon gc852 1428 m atwater valley at340 2230 m and alaminos canyon ac601 2384 m infaunal 13 c and 15 n exhibited a broad range of values most infauna appeared to be heterotrophic although several taxa had very light 15 n and 13 c values indicating possible reliance on chemoautotrophic symbioses the lightest 13 c and 15 n values were observed in nematodes 13 c 54 6 0 1 15 n 6 1 0 2 and one gastropod 13 c 54 1 15 n 1 1 from green canyon mixing model results indicated that sulfur oxidizing beggiatoa may be an important food source for seep infauna the rate of utilization ranged from 60 to 100 at green canyon and atwater valley the overall range in isotope values was similar across the three sites suggesting that biogeochemical processes may be very similar in these geographically distinct areas

a model for the boreal summer intraseasonal oscillation abstract the tropical intraseasonal oscillation iso exhibits pronounced seasonality the boreal summer iso is more complex than its winter counterpart due to the coexistence of equatorial eastward off equatorial westward and northward propagating low frequency modes and their interactions based on observational evidence and results obtained from numerical experiments a mechanism is proposed for the boreal summer iso in which the northern hemisphere summer monsoon nhsm circulation and moist static energy distribution play essential roles with a climatological july mean basic state the life cycle of model low frequency waves consists of four processes an equatorial eastward propagation of a coupled kelvin rossby wave packet an emanation of moist rossby waves in the western pacific a westward propagation and amplification of the rossby waves in south asian monsoon regions and a reinitiation of the equatorial disturbances over the central indian ocean the life cycle spans about one month and p

combined carbonate carbon isotopic and cellular ultrastructural studies of individual benthic foraminifera 2 toward an understanding of apparent disequilibrium in hydrocarbon seeps 1 numerous previous studies show disequilibrium between stable carbon isotope ratios of foraminiferal calcite and pore water dissolved inorganic carbon in hydrocarbon seeps calling into question the utility of this widely used paleoceanographic tracer as a proxy we use a recently developed method to compare stable carbon isotope ratios of foraminiferal carbonate with cell ultrastructural observations from individual benthic foraminifera from seep under chemosynthetic bivalves and nonseep habitats in monterey bay california to better understand control s of benthic foraminiferal carbon isotope ratios two attributes previously proposed to cause the isotopic offsets are diet and symbionts ultrastructural analysis shows that positive staining with rose bengal indicates presence of foraminiferal cytoplasm bacterial biomass or a combination of both and thus is not an unequivocal indicator of viability we also show for the first time that some living seep foraminifera have endobionts results from our unique yet limited data set are consistent with suggestions that in our sites several foraminiferal species collected from seep clam beds may not survive there diet and symbiont presence do not appear to be major contributors to disequilibrium little calcification of seep tolerant foraminiferal species occurs while seep conditions prevail and microscale variability in habitats could influence 13c of benthic foraminiferal carbonate results further suggest that our knowledge of benthic foraminiferal ecology and biomineralization especially in extreme habitats such as seeps must be bolstered before we fully understand the fidelity of paleoenvironmental records derived from benthic foraminiferal test 13c data

dependence of simulation of boreal summer tropical intraseasonal oscillations on the simulation of seasonal mean the link between realism in simulation of the seasonal mean precipitation and summer tropical intraseasonal oscillations and their dependence on cumulus parameterization schemes is investigated using the florida state university global spectral model fsugsm forty member model ensemble simulations of the northern summer season are generated for three different cumulus parameterization schemes namely arakawa schubert naval research laboratory nrl zhang and mcfarlane national center for atmospheric research ncar and emanuel massachusetts institute of technology mit the mit scheme simulates the regional pattern of seasonal mean precipitation over the indian monsoon region well but has large systematic bias in simulating the precipitation over the western pacific and the maritime continent although the simulation of details of regional distribution of precipitation over the indian monsoon region by the nrl and ncar schemes is not accurate they simulate the spatial pattern of precipitation over the tropical indo pacific domain closer to observation the nrl scheme seems to captures the observed northward and eastward propagation of intraseasonal precipitation anomalies realistically however the simulations of the ncar and mit schemes are dominated by a westward propagating component the westward propagating mode seen in the model as well as observations is indicated to be an equatorial rossby wave modified by the northern summer mean flow an examination of the relationship between simulation of the model climatology and eastward propagating character of monsoon intraseasonal oscillations isos in a limited sample shows that the scheme that simulates better seasonal mean pattern of rainfall over the tropical indo pacific domain also simulates better intraseasonal variance and more realistic eastward propagation of monsoon isos among the parameters known to be important for meridional propagation of the summer monsoon isos the meridional gradient of mean humidity in the lower atmosphere seems to be crucial in determining the northward propagation in the equatorial indian ocean between 10 s and 10 n for better prediction of the seasonal mean indian monsoon therefore the model climatology should have minimum bias not only over the indian monsoon region but also over the entire indo pacific basin

bioturbation by symbiont bearing annelids in near anoxic sediments implications for biofacies models and paleo oxygen assessments anoxic or nearly anoxic conditions 4 m o2 have long been associated with the absence of bioturbation and animal traces this premise has guided interpretation of paleoceanographic conditions from rocks and sediments we recently observed a high density living assemblage of highly mobile symbiont bearing burrowing phallodrilinid oligochaetes within a nearly anoxic basin 1 m o2 0 02 0 03 ml l 1 on the peru margin 305 m these observations were made during the most intense part of the 1997 98 el nino when there may have been slight oxygenation of an otherwise anoxic basin but oligochaete presence prior to this event is likely the occurrence of symbiont bearing gutless oligochaetes mainly within the upper 5 cm of the sediment column coincided with a bioturbated zone overlying distinctly laminated sediments our observations redefine the lower oxygen limit of macrofaunal bioturbation to 2 m and indicate a need to modify currently accepted ideas about the relationship between bioturbation and paleo oxygen concentration these results also address an ongoing debate about the lifestyles of bioturbating organisms in oxygen poor settings

macrobenthos community structure and trophic relationships within active and inactive pacific hydrothermal sediments hydrothermal fluids passing through sediments create a habitat hypothesized to influence the community structure of infaunal macrobenthos here we characterize the density biomass species composition diversity distributions lifestyle and nutritional sources of macroinfauna in hydrothermal sediments in ne and sw pacific settings and draw comparisons in search of faunal attributes characteristic of this habitat there is increasing likelihood that seafloor massive sulfide deposits associated with active and inactive hydrothermal venting will be mined commercially this creates a growing imperative for a more thorough understanding of the structure dynamics and resilience of the associated sediment faunas and has stimulated the research presented here macrobenthic assemblages were studied at manus basin 1430 1634 m papua new guinea png as a function of location south su vs solwara 1 and hydrothermal activity active vs inactive and at middle valley 2406 2411 m near juan de fuca ridge as a function of habitat active clam bed microbial mat hot mud inactive background sediment the studies conducted in png formed part of the environmental impact assessment work for the solwara 1 project of nautilus minerals niugini limited we hypothesized that hydrothermally active sites should support a higher densities and biomass b greater dominance and lower diversity c a higher fraction of deposit feeders and d greater isotopic evidence for chemosynthetic food sources than inactive sites manus basin macrofauna generally had low density o1000 ind m

a study of the chemistry of pore fluids and authigenic carbonates in methane seep environments kodiak trench hydrate ridge monterey bay and eel river basin analyses of the chemical and isotopic composition of carbonates rocks recovered from methane seepage areas of the kodiak trench hydrate ridge monterey bay clam flats and the eel river basin coupled with the studies of the chemistry of the pore fluids have shown that these carbonates have grown within the sediment column geochemical profiles of pore fluids show that in deep water seeps kodiak trench 4450 m monterey bay 1000 m hydrate ridge 650 m 13c dic values are low isotopically light whereas in the eel river area 350 500 m 13c dic values are much higher isotopically heavier in all cases the 13c values indicate that processes of methane oxidation associated with sulfate reduction are dominant in the shallow sediments data on the isotopic composition of authigenic carbonates found at sites in kodiak trench eel river basin south and eel river basin north indicate a variable composition and origin in different geochemical environments some of the authigenic carbonates from the study sites show a trend in their 13c values similar to those of the pore fluids obtained in their vicinity suggesting formation at relatively shallow depths but others indicate formation at greater sediment depths the latter usually consist of high magnesium calcite or dolomite which from their high values of 13c up to 23 and 18o up to 7 5 suggest formation in the deeper horizons of the sediments in the zone of methanogenesis these observations are in agreement with observations by other workers at hydrate ridge in monterey bay and in the eel river basin

isotopic evidence for the incorporation of methane derived carbon into foraminifera from modern methane seeps hydrate ridge northeast pacific the presence of modern methane seeps at hydrate ridge offshore oregon provide an opportunity to study the influence of methane seeps on the ecology and geochemistry of living foraminifera a series of cores were collected from the southern summit of hydrate ridge in 2002 samples were preserved and stained to determine the 13c composition of three species of live stained and dead benthic foraminifera uvigerina peregrina cibicidoides mckannai and globobulimina auriculata specimens were examined under light and scanning electron microscopy sem and exhibit no evidence of diagenesis or authigenic carbonate precipitation individual living foraminifera from seep sites recorded 13c values from 0 4 to 21 2 indicating the isotopic influence of high methane concentrations average 13c values calculated from single specimens range from 1 28 to 5 64 at seep sites and 0 81 to 0 85 at a control off seep site two distinct seep environments distinguished by the presence of microbial mats or clam fields were studied to determine environmental influences on 13c values individual foraminifera from microbial mat sites exhibited more depleted 13c values than those from clam field sites we interpret these differences as an effect of food source and or symbiotic microbes on foraminiferal carbon isotopic values acting to magnify the negative 13c values recorded via the dic pool no statistical difference was found between 13c values of live vs dead specimens this suggests that authigenic carbonate precipitation did not play a dominant role in the observed isotopic compositions however a few dead specimens with extremely negative 13c composition 12 do indicate potential evidence for an authigenic influence on the recorded 13c composition

influence of indian ocean dipole on poleward propagation of boreal summer intraseasonal oscillations abstract the influence of the indian ocean dipole iod on the poleward propagation of boreal summer intraseasonal oscillations bsisos is examined using observed datasets this study finds that coherent incoherent poleward propagation of precipitation anomalies from 5 s to 25 n are observed during negative positive iod years disorganized poleward propagation of bsiso in the south equatorial indian ocean is observed during positive iod years the rationale behind such an anomaly in the poleward propagation of bsiso in contrasting iod years is identified based on the theory of northward propagating bsiso which suggests the influential role of air sea interaction on the genesis and propagation of bsiso it is found that the mean structure of moisture convergence and meridional specific humidity distribution undergoes radical changes in contrasting iod years which in turn influences the meridional propagation of bsiso this study assumes significance considering the critical role of bsiso in modulat

the geology of nuclear waste disposal an icsu committee on the geological disposal of high level radioactive wastes has concluded that century long interim storage is essential and that disposal in subduction trenches and ocean sediments deserves more attention

geological imprint of methane seepage on the seabed and biota of the convergent hikurangi margin new zealand box core and grab carbonate results abstract short box cores to 30 cm bsf and seafloor carbonate grab samples were acquired at mapped hydrocarbon seep sites 600 1200 m water depths during the 2007 rv sonne so191 cruise on the hikurangi margin offshore eastern north island new zealand to evaluate the influence of methane seepage on sedimentologic biotic mineralogic and stable isotopic attributes of seabed sediments sedimentary horizons in the box cores consist of siliciclastic silts and sands shell beds and nodular microcrystalline aragonite bands up to 15 cm thick the megafauna is dominated by infaunal to semi infaunal chemosymbiotic bivalves calyptogena lucinoma and acharax as well as associated worms and carnivorous and grazing gastropods burrows in silts some occupied by worms or juvenile acharax mainly have simple morphologies more typical of high energy nearshore settings than deep sea environments while a few are large and sparsely branched with wall scratch marks inferred to be of decapod crustacean origin the box core silts and nodular carbonate samples vary in toc content from 0 2 to 0 9 wt carbonate content from 4 to 78 and 13 c and 18 o values from 50 3 to 0 6 pdb and 0 77 to 3 2 pdb respectively low carbonate content silt samples have the most enriched 13 c values implying a seawater source for their pore water bicarbonate negative 13 c and positive 18 o values typify the nodular microcrystalline aragonite bands indicating formation during microbially mediated sulphate dependent anaerobic oxidation of methane aom in a cold near seafloor environment as is also supported by lipid biomarker data a clear isotopic mixing trend of decreasing 13 c and increasing 18 o and carbonate content in the fine seafloor grab carbonate samples show greater textural variability and are divided into two types fresh appearing grey to white blocks yield similar mineralogic isotopic and biomarker signatures to the nodular carbonate bands in the cores a largely seep related epifauna affiliated with these grab samples include chemosymbiotic bathymodiolin mussels siboglinid tube worms methanotrophic suberitid sponges and grazing limpets which in places are entombed within the carbonate by contrast some dark reddish to brown iron stained microcrystalline dolomitic slabs and tubular concretions support abundant non seep epifaunal encrusters from the surrounding deep sea indicative of long exposure on the seafloor distinct stable isotopic signatures of these exhumed dolostones 13 c c 20 pdb 18 o up to 7 pdb suggest derivation from an oxidised methane pool and pore fluid freshening by gas hydrate dissociation or from mobilized burial fluids that have undergone clay mineral dehydration

a case study of the impact of boreal summer intraseasonal oscillations on yangtze rainfall the impact on yangtze rainfall of the boreal summer intraseasonal oscillations bsisos over the entire asian summer monsoon region during summer 1996 was investigated using the aphrodite gridded rainfall and the ncep doe reanalysis ii products wavelet analyses suggest that the isos of yangtze rainfall were regulated mainly by both 30 60 and 10 25 day oscillations respectively linked to bsiso1 and bsiso2 activity phase locking of the wet phases of these two isos resulted in a prolonged wet episode from late june to mid july the circulation evolution of the bsiso1 mode showed that active convection accompanied by strong convergence of anomalous zonal winds first developed over the equatorial indian ocean with suppressed convection over the south china sea scs philippine sea and with active convection over the yangtze basin the triple convection anomaly that aligned meridionally in the east asian sector arose from a local meridional vertical cell associated with a rossby wave like coupled circulation convection system the opposite flow patterns occurred during the dry phase of yangtze rainfall the composite bsiso2 cases demonstrated a weak convective anomaly initially appeared around the maritime continent with a huge anomalous anticyclone accompanied by suppressed convection over the scs philippine sea the low level convergence of the anomalous southwesterlies on the northwestern side of the anticyclone and the consequent ascent led to positive rainfall anomalies over the yangtze basin when the entire scs was dominated by an anomalous cyclone resulting from interaction with upstream systems convection over the yangtze basin was suppressed

structures and mechanisms of the northward propagating boreal summer intraseasonal oscillation abstract the spatial and temporal structures of the northward propagating boreal summer intraseasonal oscillation bsiso are revealed based on the analysis of both the echam4 model simulation and the ncep ncar reanalysis the bsiso structure and evolution characteristics simulated by the model bear many similarities to those derived from the ncep ncar reanalysis the most notable features are the remarkable meridional asymmetries relative to the bsiso convection in the vorticity and specific humidity fields a positive vorticity perturbation with an equivalent barotropic structure appears a few latitude degrees north of the convection center the maximum specific humidity also shows a clear northward shift in the lower troposphere two internal atmospheric dynamics mechanisms are proposed to understand the cause of the northward propagation of the bsiso the first is the vertical shear mechanism the key process associated with this mechanism is the generation of barotropic vorticity due to the couplin

the nuclear waste disposal problem an overview from a geological and geochemical perspective abstract in this paper we present a brief review of nuclear waste disposal research from a geological and geochemical perspective examples were chosen to illustrate both laboratory and field aspects of nuclear waste disposal and to show how these could be linked together by geological analogy and observation this strategy of linking geological observations and laboratory experiments and tailoring the disposal concept to simulate the more attractive features of the geology should give greater credence to the overall performance assessment of a nuclear waste disposal system

stable isotope signatures and methane use by new zealand cold seep benthos the carbon isotopic composition of seep faunal tissue represents a time integrated view of the interaction between biology and the biogeochemical gradients within the environment here we provide an initial description of carbon and nitrogen stable isotope signatures of dominant symbiont bearing megafauna and heterotrophic mega and macrofauna from 10 methane seep sites on the continental margin of the north island of new zealand 662 1201 m water depth isotopic signatures suggest that sulfide oxidation supports symbiont bearing taxa including solemyid and vesicomyid bivalves and methanotrophic symbionts are present in the seep mussel bathymodiolus sp multiple species of frenulata siboglinidae are present and have a range of isotopic values that are indicative of both thiotroph and methanotroph based nutrition isotopic composition of the tubeworm lamellibrachia sp varied by 23 3 among individuals although there was no consistent difference among sites variation in methane use by heterotrophic fauna appears to reflect the availability of hard vs soft substrate macrofauna on hard substrates had high 13c signatures reflecting consumption of photosynthetic derived organic matter two unique biotic assemblages were discovered to be fueled largely by methane a hard substrate multi phyla sponge associated community inhabiting the sponge pseudosuberites sp and a soft sediment assemblage dominated by ampharetid polychaetes isotope signatures yield estimates of 38 100 and 6 100 methane derived carbon in sponge associates and ampharetid bed macrofauna respectively these estimates are comparable to those made for deeper methane seeps at the florida escarpment 3290 m and kodiak alaska seeps 4445 m the overall high use of methane as a carbon source by both symbiont bearing and heterotrophic fauna suggests that new zealand methane seeps are an ideal model system to study the interaction among metazoans bacteria archaea and their resulting effect on methane cycles

carbon stable isotopic composition of benthic foraminifera from pliocene cold methane seeps cascadia accretionary margin abstract cold methane seep carbonates preserve the distinctive carbon stable isotope signatures of their ambient porewaters thus facilitating the identification of methane sources and fluid migration pathways this study employs an isotopic indicator from microfossils in a diffuse fossil seep for the recognition and characterization of methane seepage in the rock record benthic foraminifera from the pliocene quinault formation western washington state are plentiful and provide a temporal link between modern and more ancient seeps stable carbon isotope analyses of individual foraminiferal tests revealed a clear distinction between seep and non seep foraminifera infaunal species globobulimina pacifica and nonion basispinatum collected from seep samples exhibited 13 c values that were highly variable and often strongly depleted values ranged from 33 1 to 55 3 pdb in g pacifica and from 2 1 to 42 9 pdb in n basispinatum the epifaunal species cibicidoides mckannai though less depleted also showed considerable variability with 13 c values ranging from 1 7 to 3 1 pdb in contrast non seep specimens were much more enriched and less variable non seep specimens of n basispinatum displayed 13 c values clustering between 0 5 and 1 5 pdb while non seep specimens of c mckannai yielded a range of 1 1 to 1 8 pdb sem analyses and oxygen isotope values of foraminiferal tests indicated minimal diagenetic alteration 13 c values from authigenic blebs small nodules with wispy indistinct boundaries ranged from 8 7 to 38 4 pdb by combining these inorganic carbonate data with the foraminiferal values the association of seep specific bivalves and the present day leakage of thermogenic methane from the nearby garfield gas mound we conclude that these foraminifera precipitated their tests in the presence of methane derived carbon thus they record pore water 13 c depletion and syn depositional fluid flow pathways near the sediment water interface in a seep system active 3 4 mya and continuing onshore and offshore today the range and degree of 13 c depletion in the pliocene microfossils is due to the heterogeneity of seepage caused by different methane sources i e thermogenic and biogenic the tortuosity of fluid migration pathways reaching the seafloor sediments and mixing of seep fluids with dissolved inorganic carbon dic and marine organic carbon

molecular and isotopic analysis of anaerobic methane oxidizing communities in marine sediments convergent lines of molecular carbon isotopic and phylogenetic evidence have previously indicated hinrichs k u hayes j m sylva s p brewer p g delong e f 1999 methane consuming archaebacteria in marine sediments nature 398 802 805 that archaea are involved in the anaerobic oxidation of methane in sediments from the eel river basin offshore northern california now further studies of those same sediments and of sediments from a methane seep in the santa barbara basin have confirmed and extended those results mass spectrometric and chromatographic analyses of an authentic standard of sn 2 hydroxyarchaeol hydroxylated at c 3 in the sn 2 phytanyl moiety have confirmed our previous tentative identification of this compound but shown that the previously examined product was the mono tms rather than di tms derivative further analyses of 13 c depleted lipids appreciably more abundant in samples from the santa barbara basin have shown that the archaeal lipids are accompanied by two sets of products that are only slightly less depleted in 13 c these are additional glycerol ethers and fatty acids the alkyl substituents in the ethers mostly monoethers with some diethers are non isoprenoidal the carbon number distributions and isotopic compositions of the alkyl substituents and of the fatty acids are similar suggesting strongly that they are produced by the same organisms their structures n alkyl and methyl branched n alkyl require a bacterial rather than archaeal source the non isoprenoidal glycerol ethers are novel constituents in marine sediments but have been previously reported in thermophilic sulfate and nitrate reducing organisms which lie near the base of the rrna based phylogenetic tree based on previous observations that the anaerobic oxidation of methane involves a net transfer of electrons from methane to sulfate it appears likely that the non archaeal 13 c depleted lipids are products of one or more previously unknown sulfate reducing bacteria which grow syntrophically with the methane utilizing archaea their products account for 50 of the fatty acids in the sample from the santa barbara basin at all methane seep sites examined the preservation of aquatic products is apparently enhanced because the methane oxidizing consortium utilizes much of the sulfate that would otherwise be available for remineralization of materials from the water column

thorite in fault zones of a granitic pluton atikokan canada implications for nuclear fuel waste disposal abstract thorite identified under a scanning electron microscope occurs in fault zones investigated throughout the eye dashwa pluton the undeformed nature and development of corona structures around the thorite suggest its growth during post kinematic conditions tho2 and sio2 constitute the major oxides in the thorite found in the pluton while ce2o3 fe2o3 cao uo2 p2o5 and s are present in minor amounts thermodynamic analysis shows that this thorite is a stable phase in contact with ambient groundwater in granitic environments the antiquity 2 3 ga and the chemical inertness of this thorite in contact with granite groundwater can be used as an example of a natural analogue for some aspects of nuclear fuel waste disposal

indian ocean monsoon coupled interactions and impending monsoon droughts 1 monsoon droughts over the indian subcontinent emanate from failures in the seasonal june september monsoon rains while prolonged dry spells monsoon breaks pervade on sub seasonal intra seasonal time scales the underlying causes for these long lasting anomalies remain elusive based on analyses of a suite of observed data sets we report an ocean atmosphere dynamical coupling on intra seasonal time scales in the tropical indian ocean which is pivotal in forcing extended monsoon breaks and causing droughts over the subcontinent this coupling involves a feedback between the monsoonal flow and thermocline depth in the equatorial eastern indian ocean eeio in which an anomaly of the summer monsoon circulation induces downwelling and maintains a higher than normal heat content the near equatorial anomalies induce strong and sustained suppression of monsoon rainfall over the subcontinent it is concluded that the intra seasonal evolution of the ocean monsoon coupled system is a vital key to unlocking the dynamics of monsoon droughts

mineral evolution and element mobility during episyenitization dequartzification and albitization in the postkinematic bohus granite southwest sweden abstract the petrography and geochemistry of two subsurface occurrences of pervasively albitized and episyenitized i e dequartzified granite in the central part of the postkinematic sveconorwegian bohus granite in southwestern sweden were studied the altered granite is whitened and consists of an albite microcline framework with a very fine grained interstitial assemblage of illite hematite ankerite anatase textural relations indicate that the initial dissolution of magmatic quartz accompanied by albitization of plagioclase left a vuggy reservoir rock which facilitated fluid penetration and thereby further alteration the subsequent stage is characterized by infilling of vugs by the very fine grained authigenic assemblage and by concomitant alteration of igneous minerals such as magnetite ilmenite and biotite deuteric alteration products of magmatic minerals are affected by these two alteration stages implying that episyenitization occurred widely after emplacement and cooling of the host granite mass balance calculations with reference to adjacent unaffected granite evince mainly si loss and na gain reflecting the observed mineralogical changes the volume decrease is estimated to be 9 owing to compaction accompanying the dequartzification and a slight porosity increase the calculations revealed a slight enrichment in hrees y essentially hosted by xenotime and a thorite xenotime solid solution both exsolved during recrystallization of monazite oxidation of ferrous iron and partial loss of chalcophile elements reflect oxidizing conditions the alteration episode is permo carboniferous and is possibly associated with circulation of oxidizing fluids through the bohus granite

foraminiferal response to an active methane seep environment a case study from the adriatic sea abstractit has been analysed the taxonomic structure and isotopic composition of the cytoplasm and tests of living rose bengal stained protoplasm full and dead empty tests benthic foraminifera 63 m in surface sediments from sites with and without methaneseepage at water depths of about 25 m water in the northern adriatic sea and compared these data to isotope analyses of carbonaterocks at the same locations foraminiferal density is higher in seep samples than in control ones despite the low oxygen and highsulphide contents in sediments the 13 c values in foraminiferal cytoplasm at the seep sites are lower than those in cytoplasm ofthe same species in control samples suggesting that beggiatoa may be a food source for the foraminifera and explaining thehigher foraminiferal density at the seep site in contrast the 13 c values of tests of living and dead benthic foraminifera at seep siteswere not significantly different from those in tests of the same species collected at the control sites therefore the carbon isotopevalues of foraminiferal tests in this area do not reflect the ones of the methane seepage although the authigenic carbonate incalcareous sandstones of the methane seepage area is significantly negative and indicates the contribution of methane seepage thesimilar carbon isotope values measured in the foraminiferal tests from shallow settings of the north eastern adriatic sea seemtherefore to be independent of methane seepages 2006 elsevier b v all rights reserved

distribution of uranium thorium and rare earth elements in the eye dashwa lakes pluton a study of some analogue elements abstract the distribution of u th and rare earth elements ree s in the eye dashwa lakes pluton near atikokan ontario is examined materials analysed include a unaltered granite b altered granite c highly altered granite adjacent to open fractures and d fracture filling minerals distinct distribution patterns are noted for u and some ree s among the four types of samples th shows higher concentrations in materials c and d compared with unaltered and altered granite the highly altered granite and some fracture fillings have greater concentrations of u th and ree s the large concentrations of u th and ree s in these materials are due to both sorption on selective materials and precipitation as mineral phases containing these elements the occurrence of uraninite bastnaesite and thorogummite coatings on fracture fillings are examples of this precipitation

chemical alteration in the micro weathering environment within a spheroidally weathered anorthosite boulder a chemical and mineralogical study of the innermost rindlets of a spheroidally weathered boulder from the wichita mountains oklahoma details incipient alteration of minerals along solution channels alteration products in plagioclase areas are highly aluminous whereas ferruginous residuum is commonly found in olivine alteration zones alteration of plagioclase along solution channels results in sharp weathering contacts as contrasted with wider zones of limonite bordering solution channels in olivine in certain instances cores of fresh olivine are surrounded by limonite indicating that diffusion may play a role in this type of alteration mobility of sesquioxides is evidenced by aluminum rich debris adjacent to mafic materials in solution channels and iron bearing material in channels cutting through plagioclase not resolved is whether the movement of sesquioxides in solution channels is by transport of colloidal particulates or by diffusion of dissolved species calcic plagioclase alters to calcite along the innermost solution channel it is postulated that solution exterior to the boulder and undersaturated with respect to calcite enters the rind system via solution channels cut off from the co2 reservoir of the atmosphere by the narrow confines of this solution channel the solution reacts with the bytownite to precipitate calcite apart from the occurrence of calcite no crystalline weathering products were found in the innermost rindlet samples a poorly crystallized illite was identified in the outermost rindlet these findings suggest that initial alteration products on weathering rinds are amorphous and that with time these products attain a degree of identifiable crystallinity

coupling between northward propagating intraseasonal oscillations and sea surface temperature in the indian ocean using a hybrid atmosphere ocean coupled model it is shown that during the boreal summer northwardpropagating intraseasonal oscillations npisos are strongly coupled to the underlying sea surface temperature sst in the indian ocean sector on the one hand the intraseasonal atmospheric convection changes the sst through solar radiation latent heat flux and mixed layer entrainment on the other the induced sst fluctuations feed back to affect the intraseasonal convection the preferential northward rather than southward propagation of boreal summer isos in the indian ocean is partially explained by an interaction among the summer mean climate state the atmospheric disturbances and the ocean surface temperature a solution to an atmosphere only model forced with daily sst produces much stronger npisos than a similar solution forced with monthly mean sst amip type run the atmosphere only model however even when it is forced by daily sst from the coupled model with a small amount of noise in the initial and or boundary conditions is unable to reproduce the npisos in the coupled case in the coupled system intraseasonal sst anomalies are forced by intraseasonal atmospheric convection and hence are in quadrature with the convection in the stand alone atmospheric model however sst acts only as a boundary forcing and the resultant atmospheric convection has almost the same phase with the underlying sst one consequence is that the intensity of the sst forced intraseasonal convection in the stand alone atmospheric model is considerably weaker than in the coupled model finally solutions indicate that the northward movement of the off equatorial convection in the northern indian ocean is more closely related to local intraseasonal sst anomalies than to the equatorial eastward moving madden julian oscillation positive negative sst anomalies in the northern indian ocean lead the active break phases of the intraseasonal convection by about 2 pentads 10 days therefore intraseasonal sst anomalies in the northern indian ocean are potentially a useful index to forecast active break spells of the south asian summer monsoon

relationships between sulfide oxidizing bacterial mats and their carbon sources in northern gulf of mexico cold seeps abstract chemical and isotopic characterization of microbial mats collected from methane and petroleum seeps in the gulf of mexico suggest microbial mat color is related to carbon utilization a survey of white and orange colored microbial mats collected in the northern gulf of mexico from the brine pool nr 1 bp and a hydrate mound site in green canyon 234 gc 234 during johnson sea link submersible dives was conducted to explore the bacterial utilization of different carbon sources sedimentary organic matter at bp is predominantly derived from biogenic methane whereas organic material available in sediments at gc 234 originates from a mixture of methane and non methane hydrocarbons interstitial sulfide concentrations were significantly elevated in porewater fluids below white mats collected from bp 1 2 0 2 mm and below orange mats at gc 234 6 1 0 7 mm sulfate reduction rates ranging from 0 4 to 3 8 mol so 4 cm 3 d 1 indicate rapid sulfate consumption below gc 234 orange mats a model based on carbon isotopes was used to delineate possible inorganic and organic carbon sources to bp white mats and gc 234 orange mats the results suggest the white mats are chemoautotrophic and that the orange mats may employ either heterotrophy or autotrophy

impact of atmospheric intraseasonal oscillations on the indian ocean dipole during the 1990s abstract effects of atmospheric intraseasonal oscillations isos on the indian ocean zonal dipole mode iozdm are investigated by analyzing available observations and a suite of solutions to an ocean general circulation model namely the hybrid coordinate ocean model hycom data and model solutions for the period 1991 2000 are analyzed a period that includes two strong iozdm events during 1994 and 1997 and a weak one in 1991 both the data analysis and model results suggest that atmospheric isos play a significant role in causing irregularity of the two strong iozdm events and the premature termination of the weak one of particular interest is a basinwide wind driven oceanic resonance with a period near 90 days involving the propagation of equatorial kelvin and first meridional mode rossby waves across the basin before the onset of the strong 1997 dipole wind variability had significant power near 90 days and the resonance was strongly excited associated with the resonance was a deepened t

relationships between the distribution and stable isotopic composition of living benthic foraminifera and cold methane seep biogeochemistry in monterey bay california 1 as part of an ongoing effort to explore the use of foraminifera as a means to assess modern and ancient methane release we compared ambient pore water chemistry with the distribution and stable isotopic composition of living rose bengal stained foraminifera in mbari rov ventana tube cores taken from modern seepage areas about 1000 m water depth in monterey bay california benthic foraminiferal isotopic differences between sites clearly indicate that methane influenced pore waters affect foraminiferal distributions and carbonate isotope geochemistry carbon isotope signatures of living benthic foraminifera did not conform to the very negative 30 to 48 methane influenced carbon isotope values of the pore waters they live in instead the influence of methane seep pore waters was reflected in the greater range and carbon isotopic variability of living seep foraminifera compared with published 13c values of foraminifera living in nonseep habitats it is not clear what relative influences biological ecological and physical factors have on the carbon isotopic signatures observed in seep foraminifera substantial carbon isotope differences can exist between individuals of the same seep species for instance 13c values of living globobulimina pacifica varied by as much as 2 9 between seeps within 8 km of each other whereas 13c values of living uvigerina peregrina varied by as much as 1 95 within the same seep provided there is no diagenetic alteration of the test carbonate isotopic results of individual seep foraminifera support the hypothesis that foraminifera can be used to assess past and present methane seepage

seasonality and meridional propagation of the mjo abstract the madden julian oscillation mjo is known to have a substantial impact on the variability of the asian australian summer monsoons an important but not well understood aspect of the mjo monsoon connection is the meridional propagation of bands of enhanced or reduced precipitation that are especially pronounced during the northern summer in this study the nature of the seasonality of the mjo is examined with a focus on the meridional propagation using both observations and simulations with an atmospheric general circulation model agcm a key result is that the agcm when forced with idealized eastward propagating equatorial dipole heating anomalies reproduces the salient features of the observed seasonality in the precipitation and wind fields associated with the mjo including meridional propagation into the indian and australian summer monsoon regions an analysis of the simulations and observations shows that the off equatorial precipitation anomalies are initiated by surface fricti

albitization and quartz dissolution in paleoproterozoic metagranite central sweden implications for the disposal of spent nuclear fuel in a deep geological repository hydrothermal alteration resulting in albitization and quartz dissolution has been identified in paleoproterozoic metagranites down to 1000 m elevation at forsmark sweden the alteration features were discovered during investigations to locate a site for the disposal of spent nuclear fuel in a deep geological repository in general albitization occurs extensively but it is also observed locally adjacent to minor intrusive bodies of amphibolite the altered rocks show a marked decrease in k feldspar and an increase in quartz relative to the unaltered equivalents resulting in an epitonalitic composition plagioclase is metamorphic in character and generally richer in albite than in the unaltered rocks it is inferred that albitization was triggered by the input of basic or intermediate melts into the crust during igneous activity close to the peak of regional metamorphism at 1 87 1 86 ga the mineralogy of the epitonalites gives rise to an increased thermal conductivity and thereby a positive influence for the design and safety of a deep geological repository for spent nuclear fuel however the increased frequency of low conductive amphibolite in the albitized volumes consistent with the proposed mechanism for alteration gives a negative influence in sharp contrast to the albitization a majority of the occurrences of quartz dissolution which resulted in the formation of episyenite are located along fracture zones quartz dissolution took place between or after 1 8 1 7 ga when the bedrock was able to respond to deformation in a brittle manner most of the vugs left after the removal of quartz are to a variable extent refilled by hydrothermal assemblages including quartz albite k feldspar hematite chlorite and calcite the geometry and spatial distribution of episyenite argue against an extreme fluid rock ratio and it is inferred that the fluids had at least a moderate salinity with a temperature in excess of 300 degrees c the dissolution process was promoted by the generation of secondary permeability localized in columnar or pipe like volumes the close spatial connection to fracture zones provides a basis to avoid bedrock affected by this type of alteration and thereby reduce the negative mechanical and hydrogeological aspects for a deep geological repository c 2012 elsevier b v all rights reserved

extremes of the indian summer monsoon rainfall enso and equatorial indian ocean oscillation it is well known that anomalies of the indian summer monsoon rainfall ismr are linked to el nino and southern oscillation enso we show that large anomalies of the ismr are also linked to the equatorial indian ocean oscillation equinoo between states with enhancement suppression of atmospheric convection over the western part of the equatorial indian ocean with suppression enhancement over the eastern part and associated changes in the anomaly of the zonal wind along the equator equinoo is the atmospheric component of the coupled indian ocean dipole mode there is a strong relation between the large anomalies of ismr and a composite index which is a linear combination of the indices for enso and equinoo with all seasons with large deficits excess characterized by small large values of the index however the variation of ismr within one standard deviation is more complex and does not appear to be related to the composite index

fluid venting in the eastern aleutian subduction zone fluid venting has been observed along 800 km of the alaska convergent margin the fluid venting sites are located near the deformation front are controlled by subsurface structures and exhibit the characteristics of cold seeps seen in other convergent margins the more important characteristics include 1 methane plumes in the lower water column with maxima above the seafloor which are traceable to the initial deformation ridges 2 prolific colonies of vent biota aligned and distributed in patches controlled by fault scarps over steepened folds or outcrops of bedding planes 3 calcium carbonate and barite precipitates at the surface and subsurface of vents and 4 carbon isotope evidence from tissue and skeletal hard parts of biota as well as from carbonate precipitates that vents expel either methane or sulfide dominated fluids a biogeochemical approach toward estimating fluid flow rates from individual vents based on oxygen flux measurements and vent fluid analysis indicates a mean value of 5 5 0 7 l m 2 d 1 for tectonics induced water flow wallmann et al 1997b a geophysical estimate of dewatering from the same area von huene et al 1997 based on sediment porosity reduction shows a fluid loss of 0 02 l m 2 d 1 for a 5 5 km wide converged segment near the deformation front our video guided surveys have documented vent biota across a minimum of 0 1 of the area of the convergent segment off kodiak island hence an average rate of 0 006 l m 2 d 1 is estimated from the biogeochemical approach the two estimates for tectonics induced water flow from the accretionary prism are in surprisingly good agreement

abrupt termination of indian ocean dipole events in response to intraseasonal disturbances 1 we have investigated the role of atmospheric intraseasonal disturbances on termination of the indian ocean dipole iod using multiple datasets we observed significant 30 60 day atmospheric disturbances associated with equatorial westerly zonal winds prior to termination of all iod events except for the 1982 and 1997 events the westerlies excite anomalous downwelling kelvin waves that terminate the basin wide coupled processes by warming the eastern indian ocean the 1982 and 1997 iod events coincide with the strongest el nino events during those years the intraseasonal disturbances are weak

characteristics and chronology of fracture fluid infiltration in the archean eye dashwa lakes pluton superior province evidence from h c o isotopes and fluid inclusions the archean eye dashwa lakes pluton 2672 24 ma has domains of mineralogically fresh isotropic granite domains that have undergone bulk hydrothermal alteration and at least eleven sets of sequential fracture arrays each with distinctive mineral assemblages fresh granite is characterized by whole rock 18o 8 1 to 8 6 and primary magmatic quartz feldspar 1 3 quartz biotite 5 2 to 5 4 and quartz magnetite 9 8 fractionations magmatic fluids had a calculated isotopic composition of 18o 7 9 0 5 and d 80 5 these isotropic volumes of the granite have not experienced significant incursion of external thermal waters pegmatites quartz molybdenite veins and phlogopite muscovite coated fractures are sporadically distributed in the granite and were precipitated from high temperature magmatic fluids where 18o 8 0 to 10 3 and d 80 5

an extinct foraminifer endemic to hydrocarbon seeps modern seafloor hydrocarbon seeps are usually surrounded by an unusual macrobiota dominated by symbiont bearing endemic bivalves and worms numerous species of foraminifera shelled protists also live around hydrocarbon seeps but none have been found that are endemic to this environment an extinct species of benthic foraminifera amphimorphinella butonensis has been found in large numbers in a 15 m diameter patch of siltstone surrounding a miocene concretionary carbonate mound inferred to be a fossil methane seep in new zealand the tests exhibit highly negative 13 c values consistent with a methane rich environment of recrystallization on or just below the seafloor this extremely rare species has been recorded only once before from asphalt impregnated miocene muddy limestone in indonesia most likely also associated with hydrocarbon seepage is this the first record of a foraminiferal species that was specifically adapted and endemic to hydrocarbon seep environments

bivalve shell horizons in seafloor pockmarks of the last glacial interglacial transition a thousand years of methane emissions in the arctic ocean we studied discrete bivalve shell horizons in two gravity cores from seafloor pockmarks on the vestnesa ridge 1200 m water depth and western svalbard 79 00 n 06 55 w to provide insight into the temporal and spatial dynamics of seabed methane seeps the shell beds dominated by two genera of the family vesicomyidae phreagena s l and isorropodon sp were 20 30 cm thick and centered at 250 400 cm deep in the cores the carbon isotope composition of inorganic 13c from 13 02 to 2 36 and organic 13c from 29 28 to 21 33 shell material and a two end member mixing model indicate that these taxa derived between 8 and 43 of their nutrition from chemosynthetic bacteria in addition negative 13c values for planktonic foraminifera 6 7 to 3 1 concretions identified as methane derived authigenic carbonates and pyrite encrusted fossil worm tubes at the shell horizons indicate a sustained paleo methane seep environment combining sedimentation rates with 14c ages for bivalve material from the shell horizons we estimate the horizons persisted for about 1000 years between approximately 17 707 and 16 680 years b p corrected the seepage event over a 1000 year time interval was most likely associated with regional stress related faulting and the subsequent release of overpressurized fluids

the boreal summer intraseasonal oscillation relationship between northward and eastward movement of convection the summertime intraseasonal oscillation iso is an important component of the south asian monsoon lagged regressions of intraseasonally filtered 25 80 days outgoing longwave radiation olr reveal that centers of convection move both northward and eastward from the central equatorial indian ocean subsequent to the initiation of an iso eastward movement of convection is also seen at indian subcontinent latitudes 10 8 208n based on the regression results the summertime iso convection signal appears as a band tilting northwestward with latitude and stretching from the equator to about 208n viewed along any meridian convection appears to propagate northward while equatorial convection propagates to the east to examine the robustness of the connection between eastward and northward movement individual isos are categorized and composited relative to the strength of the large scale eastward component of convection in the central equatorial indian ocean it is found that the majority of isos that exhibit northward movement onto the indian subcontinent 42 out of 54 isos or 78 also exhibit eastward movement into the western pacific ocean it is also found that when convection in the central indian ocean is not followed within 10 20 days by convection in the western pacific ocean 12 out of 54 isos or 22 the independent northward movement of convection in the indian ocean region is somewhat stunted the link between the eastward and northward movement of convection is consistent with an interpretation of the summertime iso in terms of propagating equatorial modes the northward moving portion of convection is forced by surface frictional convergence into the low pressure center of the rossby cell that is excited by equatorial iso convection a similar convergence pattern is seen for the northern winter iso but it does not generate poleward movement due to relatively cool ssts underlying the surface convergence

the significance of titanite and apatite u pb ages constraints for the post magmatic thermal hydrothermal evolution of a batholithic complex berens river area northwestern superior province canada abstract titanite apatite and in one case rutile from a suite of twenty seven samples representing the major phases of an extensive and well dated archean plutonic domain of the northwestern superior province have been dated by u pb to determine the temporal progress of thermal and hydrothermal events accompanying and following major plutonism and to assess the isotopic behaviour of these geochronometers most samples contain 1 dark brown titanite with 350 20 ppm u showing shapes and textural relationships indicative of a primary magmatic origin and yielding ages corresponding either to the time of magmatic crystallization or to that of secondary metamorphic or magmatic events known in the area 2 pale titanite with 30 2 ppm u showing textural evidence for a secondary origin by breakdown of biotite hornblende oxide or older titanite and yielding ages that in general post date the major plutonic and metamorphic events in the area 3 apatite containing 30 5 ppm u occasionally up to 150 ppm u showing igneous shapes and textural relationships but yielding post magmatic ages similar to those of coexisting pale titanite 4 rutile in one sample postdating the ages of coexisting titanite and apatite the common coexistence of two noncoeval titanite generations demonstrates that the often invoked mechanism of pb diffusion during slow cooling in this case has no general validity the distribution of primary dark titanite ages however could be explained by late closure to diffusion or alternatively as the result of resetting by the thermal or hydrothermal effects caused by younger plutonic activity the ages of the secondary pale titanites probably reflect crystallization during discrete retrogressive events promoted by moderate heating or enhanced fluid activity the correspondence between pale titanite and apatite ages suggests that the same processes also caused the isotopic resetting of apatite on a regional scale the data pattern permits the identification of domains characterized by differences in the length and intensity of the thermal and hydrothermal processes the most protracted activity is recorded in northern domains of the berens river area whereas the gold mineralized red lake area in the south underwent a very rapid decline of the thermal hydrothermal activity these data also highlight important differences between the red lake and other gold camps of the superior province such as hemlo and val d or where hydrothermal activity locally associated with mineralization occurred as much as 30 80 m y after the major orogenic developments

new records of oligocene diffuse hydrocarbon seeps northern cascadia margin abstract fossil methane seeps are preserved in late eocene through pliocene marine sedimentary units of the cascadia margin of the northeastern pacific all cascadia fossil seeps are situated in the uplifted accretionary wedge that overlies extensive middle eocene coal bearing units and the paleocene early eocene siletzia large igneous province this study describes eight previously unrecorded oligocene seeps all of which are identified by small scattered carbonates with or without accompanying characteristic seep macrofauna from both inner and outer shelf depths we interpret these deposits as reflecting spatially and temporally diffuse seepage of hydrocarbon enriched fluids sourced from various carbon sources within the actively deforming accretionary prism and term them diffuse seeps 13c and 18o values from foraminiferal carbonate from the studied stratigraphic units have broad variability authigenic carbonates occurring as nodules blebs burrow fill and fracture fill indicated microbial and thermogenic methane and multiple fluid flow pathways from within the actively deforming accretionary wedge it is apparent that the complex fluid flow regime observed in modern seeps of the cascadia margin is a continuation of one established in the late eocene

influence of seep emission on the non symbiont bearing fauna and vagrant species at an active giant pockmark in the gulf of guinea congo angola margin detailed surveying with an rov found that a dense and diverse cold seep community colonises a giant pockmark located at 3200 m depth 8 km north from the deep congo channel several types of assemblages either dominated by mytilidae and vesicomyidae bivalves or siboglinidae polychaetes are distributed on the 800 m diameter active area the site is characterised by a most active central zone in a depression with abundant carbonate concretions and high methane fluxes where high density clusters of mussels and siboglinids dominate in contrast the peripheral zones display large fields of dead and live vesicomyids on soft sediment with a lower mean density and lower methane concentration in seawater the associated megafauna includes alvinocarididae shrimps echinoids holothurians of the family synaptidae several species of gastropods two species of galatheids and zoarcidae and ophidiidae fishes multivariate analyses of video transect data show that the distribution of these major megafauna species at the pockmark scale is influenced by the habitat heterogeneity due to fluid or gas emission occurrence of hydrates substratum variability and by the presence of large symbiont bearing species several assemblages dominated either by mytilids vesicomyids or siboglinids have been sampled for megafauna densities and biomass estimations and stable isotope measurements 13c and 15n of dominant species and food sources the highest estimates of megafauna densities have been obtained in mytilid beds according to their stable isotopes values non symbiont bearing species mainly rely on chemosynthesis originated carbon either as primary consumers of chemoautotrophic microorganisms or at higher trophic level recycling organic matter or relying on bivalve and tubeworm production most of them likely feed on different sources like shrimps but differences according to habitat have been evidenced carbon and nitrogen isotope ratios of galatheids and benthic or benthopelagic fishes captured by trawls at increasing distances from the pockmark provide evidence of the high variability in the proportion of chemosynthesis originated carbon in their diet from 15 to 38 according to the species captured as far as 4 km to the site

geological geochemical and microbiological heterogeneity of the seafloor around methane vents in the eel river basin offshore california marine methane vents and cold seeps are common features along continental margins worldwide serving as localized sites for methane release and colonization by microbial and chemosynthetic megafaunal communities the eel river basin erb located on the continental slope off northern california contains active methane vents and seep associated chemosynthetic biological communities cbc on the crests of anticlines in 520 m water depth seep related features on the seafloor have a patchy distribution and include active bubbling vents chemosynthetic clam beds and sulfide oxidizing bacterial mats methane sources supplying local seeps are heterogeneous on all spatial scales and support a large and diverse microbial assemblage involved in the anaerobic oxidation of methane aom to develop a comprehensive understanding of the complex biological geochemical and physical processes associated with and influencing seafloor methane seepage a multidisciplinary approach is required here we present an integrative multidisciplinary study that illustrates the diverse processes associated with seafloor methane seepage within the eel river basin and the complex interactions defining the geochemistry mineralogy and microbiology within this environment