distribution of anthropogenic co2 in the pacific ocean 1 this work presents an estimate of anthropogenic co2 in the pacific ocean based on measurements from the woce jgofs oaces global co2 survey these estimates used a modified version of the c technique modifications include a revised preformed alkalinity term a correction for denitrification and an evaluation of the disequilibrium terms using an optimum multiparameter analysis the total anthropogenic co2 inventory over an area from 120 e to 70 w and 70 s to 65 n excluding the south china sea the yellow sea the japan east sea and the sea of okhotsk was 44 5 5 pg c in 1994 approximately 28 pg c was located in the southern hemisphere and 16 5 pg c was located north of the equator the deepest penetration of anthropogenic co2 is found at about 50 s the shallowest penetration is found just north of the equator very shallow anthropogenic co2 penetration is also generally observed in the high latitude southern ocean one exception to this is found in the far southwestern pacific where there is evidence of anthropogenic co2 in the northward moving bottom waters in the north pacific a strong zonal gradient is observed in the anthropogenic co2 penetration depth with the deepest penetration in the western pacific the pacific has the largest total inventory in all of the southern latitudes despite the fact that it generally has the lowest average inventory when normalized to a unit area the lack of deep and bottom water formation in the north pacific means that the north pacific inventories are smaller than the north atlantic

planktonic foraminiferal depth habitat and δ18o calibrations plankton tow results from the atlantic sector of the southern ocean varies by several orders of magnitude across a large gradient in sea surface temperature and other hydrographic features demonstrating high sensitivity of foraminiferal populations to regional differences in water properties the depth of maximum abundance for key species such as globigerina bulloides and neogloboquadrina pachyderma is not constant from station to station the pattern suggests that their abundance and shell chemistry are tied to density horizons or other conditions such as food availability that become more sharply defined with depth in the northern subantarctic the consistent observation of globorotalia inflata and globoratalia truncatulinoides as relatively deep dwelling species confirms their utility as indicators of upper thermocline properties in d 18 o all species are observed to be isotopically lighter than predicted from water properties but the species specific offset is fairly uniform at all stations these observations define the utility of multispecies d 18 o for reconstructing temperature and density stratification from past surface oceans index terms 4267 oceanography general paleoceanography 4572 oceanography physical upper ocean processes 4870 oceanography biological and chemical stable isotopes 3030 marine geology and geophysics micropaleontology keywords stratification d 18 o

oceanic cooling recorded in shells spanning the medieval climate anomaly in the subtropical eastern north atlantic ocean abstract the medieval climate anomaly mca 900 1300 ad was the most recent period of pre industrial climatic warming in the northern hemisphere and thus estimations of mca signals can illuminate possible impacts of anthropogenic climate change current high resolution mca climate signals are restricted to mid and high latitude regions which confounds inferences of how the mca impacted some global hemispheric climate mechanisms e g north atlantic oscillation nao to address this knowledge gap we estimate seasonally resolved sea surface temperatures ssts from the oxygen isotope composition 18o of serially sampled phorcus atratus shells from archaeological sites spanning the mca in the canary islands twelve archaeological and six modern p atratus shells were analyzed and archaeological shells were dated using carbonate target radiocarbon dating ssts were estimated using the published aragonite water equilibrium fractionation equation modern shells showed a mean sst of 20 0 1 5 c with a seasonal amplitude of 5 3 0 9 c archaeological shells exhibited a mean sst of 18 2 0 7 c with a mean seasonal amplitude of 5 5 1 0 c thus shells that span the mca in the canary islands recorded ssts that were significantly cooler than the modern p

palaeoceanographic implications of genetic variation in living north atlantic neogloboquadrina pachyderma the shells of the planktonic foraminifer neogloboquadrina pachyderma have become a classical tool for reconstructing glacial interglacial climate conditions in the north atlantic ocean1 2 3 palaeoceanographers utilize its left and right coiling variants which exhibit a distinctive reciprocal temperature and water mass related shift in faunal abundance both at present and in late quaternary sediments1 2 4 5 recently discovered cryptic genetic diversity in planktonic foraminifers6 7 8 now poses significant questions for these studies here we report genetic evidence demonstrating that the apparent single species shell based records of right coiling n pachyderma used in palaeoceanographic reconstructions contain an alternation in species as environmental factors change this is reflected in a species dependent incremental shift in right coiling n pachyderma shell calcite 18o between the last glacial maximum and full holocene conditions guided by the percentage dextral coiling ratio our findings enhance the use of 18o records of right coiling n pachyderma for future study they also highlight the need to genetically investigate other important morphospecies to refine their accuracy and reliability as palaeoceanographic proxies

field examination of the oceanic carbonate ion effect on stable isotopes in planktonic foraminifera we determined the 18o and 13c of individual globigerinoides ruber and pulleniatina obliquiloculata from sediment traps located from 5 n to 12 s along 140 w in the pacific ocean to evaluate the effects of varying co3 on shell 18o and 13c variations in the offset between shell 13c and 13cdic 13cs dic are attributed to differences in co3 temperature and shell size between sample sites when 13cs dic of g ruber was corrected for variations in co3 using the experimental slope of bijma et al 1998 the residual 13cs dic was correlated with mixed layer temperature 0 10 0 04 c 1 the slope of this temperature effect is consistent with experimental results in p obliquiloculata 13cs dic and temperature were strongly anticorrelated 0 14 0 03 c 1 we are unable to separate the influences of co3 and temperature in this species without independent experimental data correcting for co3 variability on 18os of g ruber improves the accuracy of estimated sea surface temperatures

moored sediment trap measurements of carbon export in the subantarctic and polar frontal zones of the southern ocean south of australia sediment trap moorings were deployed from september 21 1997 through february 21 1998 at three locations south of australia along 140 e at 47 s in the central subantarctic zone saz with traps at 1060 2050 and 3850 m depth at 51 s in the subantarctic front with one trap at 3080 m and at 54 s in the polar frontal zone pfz with traps at 830 and 1580 m particle fluxes were high at all the sites 18 32 g m 2 yr 1 total mass and 0 5 1 4 g organic carbon m 2 yr 1 at 1000 m assuming minimal flux outside the sampled summer period these values are similar to other southern ocean results and to the median estimated for the global ocean by lampitt and antia 1997 and emphasize that the southern ocean exports considerable carbon to the deep sea despite its high nutrient low chlorophyll characteristics the saz site was dominated by carbonate 50 of total mass and the pfz site by biogenic silica 50 of total mass both sites exhibited high export in spring and late summer with an intervening low flux period in december for the 153 day collection period particulate organic carbon export was somewhat higher in all the traps in the saz range 0 57 0 84 gc m 2 than in the pfz range 0 31 0 53 with an intermediate value observed at the saf 0 60 the fraction of surface organic carbon export estimated from seasonal nutrient depletion lourey and trull 2001 reaching 1000 m was indistinguishable in the saz and pfz despite different algal communities

late pliocene pleistocene environments and glacial history of the northern north sea abstract based on new geochronological amino acids and sr isotopes and lithological data combined with analyses of 3d seismic data the pliocene pleistocene development of the central northern north sea has been investigated at the start of the plio pleistocene transition the study area was dominated by a deltaic shallow marine or tidal depositional environment with sediments mainly sourced from the west these sand rich sediments include green glauconitic grains that belong to the utsira sand with a local provenance directly above the base quaternary r2 a 60 m thick layer of mud rich sediments of glacimarine origin were deposited at a rate of 12 cm ka between 2 1 5 ma and up to 80 cm ka between 1 5 and 1 2 ma possibly reflecting glacial ice advancing to the norwegian coastline the high rate of deposition in the early pleistocene occurred immediately before the initiation of the norwegian channel ice stream at 1 1 ma following this a large part of the sediment input from fennoscandia seems to have been directed away from the study area to the shelf break at the start of the mid pleistocene transition mpt subaerial conditions allowed the formation of a 50 km long fluvial channel across the study area draining water from the east to the south west the earliest evidence of grounded ice in the investigated area comes from mega scale glacial lineations formed during the mpt at or just after 1 2 ma following this a regional unconformity r4 was formed by one or more grounded ice advances across the study area possibly during or directly after the mpt and likely marks the boundary between the early and mid pleistocene glacimarine sediments the mid to late pleistocene stratigraphy is dominated by glacimarine sediments and tills and is associated with multiple generations of tunnel valleys observed within the seismic data a high shear strength till containing chalk clasts transported from the west and or south of the study area was likely deposited during mis6 and may have been more conducive to tunnel valley formation in comparison to lower shear strength tills deposited by later ice advances a thick till unit overlain by a sand layer in the study area was deposited by grounded ice during the last glacial maximum and subsequent drainage of an ice dammed lake in the southern north sea during the last deglaciation mis2 of the study area this study shows that much of the quaternary age sediments within the northern north sea were deposited relatively rapidly during short periods of time probably leaving significant hiatuses within the stratigraphic record this finding has implications for previous studies that use a chronological framework assuming a relatively continuous sedimentation rate and record for the early pleistocene within the north sea

eruption rates and compositional trends at los humeros volcanic center puebla mexico the los humeros volcanic center located 180 km east of mexico city is one of several pleistocene silicic centers in the back arc portion of the mexican neovolcanic belt the eruptive history at los humeros suggests that average eruptive rates increased with time and exceeded rates of regeneration of differentiated magma silicic volcanism began 0 47 ma ago with extrusion of high silica rhyolite domes shortly thereafter at 0 46 ma ago 115 km3 of magma zoned from high silica rhyolite to rhyodacite were erupted resulting in formation of the xaltipan ignimbrite and collapse of the 21 15 km los humeros caldera high silica rhyolite domes then erupted along the northwestern ring fracture zone of the caldera they are covered by the faby tuff a dominantly rhyodacitic sequence of plinian fall deposits erupted from the southeast quadrant of the los humeros caldera dated at 0 24 ma a second major caldera forming event occurred 0 1 ma ago with the eruption of the zaragoza tuff a nonwelded ignimbrite zoned from rhyodacite to andesite eruption of these 12 km3 of magma led to collapse of the 10 km diameter los potreros caldera which is nested within the older los humeros caldera between 0 04 and 0 03 ma ago an arc of andesitic scoria cones concentrated along the southern ring fracture zone of the los humeros caldera fed lavas that flowed southward from the volcanic center and andesite lavas built two small shields between the eastern rims of the two calderas approximately 6 km of andesitic magma were extruded during this stage activity continued up to 0 02 ma ago with eruption of 10 km3 of rhyodacitic to andesitic lava flows from centers near the northern margin of the los potreros caldera in the area between the eastern rims of the two calderas and within a broad band where the southern segments of the inferred los humeros and los potreros ring fracture zones nearly coincide simultaneous venting of rhyodacitic and andesitic tephra within this band led to formation of the 1 7 km diameter el xalapazco caldera minor fault bounded uplift of the southeastern quadrant of the los potreros caldera followed the latest stage of volcanic activity is represented by the eruption of 0 25 km3 of olivine basalt lavas along the southern ring fracture zone of the los humeros caldera and on the floors of the los potreros and el xalapazco calderas erupted magmas show an overall trend with time toward more mafic compositions volumetric eruptive rates increased from 0 06 km3 per thousand years 0 25 ma ago to 0 2 km3 per thousand years in the last 0 1 ma the increase in eruptive rate may have been the result of a progressive decrease in the structural integrity of the roof zone of the system as successive caldera forming eruptions reactivated old zones of weakness and created new ones an increasingly disrupted roof allowed mafic and intermediate magmas to reach the surface relatively rapidly decreasing their residence time in a high level chamber and thus the time available for their differentiation

seasonal stable isotopic variations in living planktonic foraminifera from bermuda plankton tows abstract seasonal variations in surface water temperature and the 18o 16o ratios of calcite tests of living planktonic foraminifera collected in the upper 10 mare are coincident in the sargasso sea off bermuda the 18o of seasonally restricted globorotalia truncatulinoides and globigerinoides ruber pink and white may be used to determine the seasonal temperature contrast of the oceans in the past a preliminary model based on yearly absolute abundance and isotopic composition of these two species is able to approximate the composite 18o of fossil specimens of these species carbon and oxygen isotopic compositions of most species are size dependent with the largest differences occuring in 13c as a function of size the calcite tests of all living species were depleted in 13c relative to the 13c of total dissolved co2 at 0 and 50 m with no seasonal pattern in 13c being discernible in any species in almost all cases fossil specimens from box core sediments are significantly enriched in 13c and slightly enriched in 18o relative to their counterparts in the living fauna because the sediment populations are generally composed of larger sized specimens compares to the plankton of larger size specimens compared to the plankton

core top calibration of δ18o and δ13c of g ruber white and u mediterranea along the southern adriatic coast of italy we carried out an extensive survey of the oxygen and carbon isotope composition of the planktic species g ruber white and of the benthic species u mediterranea along the southern italian coast of the adriatic sea and in the gulf of taranto comparison with seasonal satellite based sea surface temperature maps and water column profiles as well as with several sets of water samples allows estimation of the effect of salinity and different nutrient supply on the 18o and 13c of foraminifera the results indicate that g ruber white while being highly affected by different salinity and nutrient distributions related to circulation patterns of major water masses dominantly record summer temperature conditions u mediterranea reflect the recent environmental conditions such as nutrient supply and bottom water temperature characteristics along the southern italian coast and clearly show the transition from a near coastal eutrophic system to an offshore oligotrophic system

carbon isotopic disequilibrium in polar planktonic foraminifera and its impact on modern and last glacial maximum reconstructions calibration studies of neogloboquadrina pachyderma sinistral coiling hereinafter referred to as n pachyderma s in the south atlantic raise questions about the interpretation of this species carbon isotope composition as a paleoceanographic tracer of southern ocean surface nutrient contents carbon isotope disequilibrium between 13c of total co2 tco2 of seawater and 13c of n pachyderma s increases systematically between 70 and 40 s several effects could cause the observed carbon isotope disequilibrium including a combination of foraminiferal diet calcification temperature and carbonate ion chemistry combining these corrections to the 13c of n pachyderma s improves the reconstruction of the 13c of seawater tco2 between 0 and 200 m in the modern south atlantic with these corrections applied the 13c for equilibrium calcite reconstructed from n pachyderma s at the last glacial maximum is very similar to preindustrial values suggesting that one cannot rule out the possibility that surface nutrient concentrations in the south atlantic ocean were comparable to today however the magnitude of the uncertainties associated with these corrections make it difficult to assess absolute paleonutrient concentrations with much confidence

catastrophic debris avalanche from ancestral mount shasta volcano california a debris avalanche deposit extends 43 km northwestward from the base of mount shasta across the floor of shasta valley california where it covers an area of at least 450 km 2 the surface of the deposit is dotted with hundreds of mounds hills and ridges all formed of blocks of pyroxene andesite and unconsolidated volcaniclastic deposits derived from an ancestral mount shasta individual hills are separated by flat topped laharlike deposits that also form the matrix of the debris avalanche and slope northwestward about 5 m km radiometric ages of rocks in the deposit and of a postavalanche basalt flow indicate that the avalanche occurred between about 300 000 and 360 000 yr ago an inferred average thickness of the deposit plus a computed volume of about 4 km 3 for the hills and ridges indicate an estimated volume of about 26 km 3 making it the largest known quaternary landslide on earth

preliminary report on the activity at unzen volcano japan november 1990 november 1991 dacite lava domes and pyroclastic flows abstract the eruption of unzen volcano commenced on 17 november 1990 phreatic and phreatomagmatic eruptions occurred by early may 1991 no large scale explosive eruptions preceded the extrusion of lava domes lava domes appeared in a summit crater on 20 may 1991 and they grew on the steep slope of mt fugen at unzen volcano rockfalls from the margins of the domes frequently generated pyroclastic flows major pyroclastic flows occurred on 3 june 8 june and 15 september 1991 the 3 june pyroclastic flow killed forty three persons many of the pyroclastic flows seem to have resulted from the simple rockfalls except one flow on 8 june which was accompanied by an explosion from the crater many of the rockfalls that generated pyroclastic flows were witnessed as of november 1991 unzen volcano was still active with a nearly constant magma supply rate of about 0 3 106 m3 d the total magma output exceeded 45 106 m3 by the beginning of november 1991 the volume of the lava domes is more than 23 106 m3

paleogeographic setting and depositional architecture of a sand dominated shelf depositional system miocene utsira formation north sea basin abstract the middle late miocene utsira sandstone of the north sea basin contains a fully preserved regional marine sand deposit that records a stable paleogeographic setting of shelf sand transport and accumulation within an epeiric shelf sea which persisted for ca 8 myr the sediment dispersal system was defined by 1 sediment input through a prograding strandplain platform coast to shelf bypass and regional basin centered transport and deposition within an elongate seaway 2 a high energy marine regime 3 very low rates of sediment supply and accumulation in the accommodation dominated seaway 4 high sediment reworking ratio and consequent abundance of autochthonous sediment 5 regional along strike sediment transport and 6 local to subregional landward sediment transport shelf systems were primarily nourished by sediment reworked from the shetland strandplain which prograded eastward into the central viking trough the viking strait lay between the constructional platform and the nondepositional horda platform southward longshore transport on the high energy shoreface and shallow shelf platform constructed the mounded south viking shelf shoal southward building sandy banner banks that formed along the recurved arc of the platform margin nourished the shoal system low angle sigmoid clinoforms with downstepping aggradational tops are distinctive architectures of the strike fed sand bodies the combination of strong marine currents and slow but continual sand supply from the shetland strandplain created regional sandy shelf depositional systems that individually covered 3500 to 6000 sq km of basin floor defining elements of the shelf shoal systems include their location within the basin axis mounded morphology stratal architecture and construction by amalgamated marine sand facies

deformation and seismic precursors to dome collapse and fountain collapse nuees ardentes at merapi volcano java indonesia 1994 1998 abstract following the eruption of january 1992 episodes of lava dome growth accompanied by generation of dome collapse nuees ardentes occurred in 1994 1998 in addition nuees ardentes were generated by fountain collapse in january 1997 and the 1998 events also suggest an explosive component significant tilt and seismic precursors on varying time scales preceded these events deformation about the summit has been detected by electronic tiltmeters since november 1992 with inflation corresponding generally to lava dome growth and deflation or decreased inflation corresponding to loss of dome mass strong short term days to weeks accelerations in tilt rate and seismicity occurred prior to the major nuees ardentes episodes apart from those of 22 november 1994 which were preceded by steadily increasing tilt for over 200 days but lacked short term precursors because of the combination of populated hazardous areas and the lack of an issued warning about 100 casualties occurred in 1994 in contrast the strong precursors in 1997 and 1998 provided advance warning to observatory scientists enabled the stepped raising of alert levels and aided hazard management as a result of these factors but also the fortunate fact that the large nuees ardentes did not quite descend into populated areas no casualties occurred the nuee ardente episode of 1994 is interpreted as purely due to gravitational collapse whereas those of 1997 and 1998 were influenced by gas pressurization of the lava dome

cerro grande volcano the evolution of a miocene stratocone in the early trans mexican volcanic belt abstract cerro grande volcano is a well preserved low angle composite volcano that evolved between 11 and 9 ma it represents the beginning of volcanism in the eastern sector of the early trans mexican volcanic belt extensive field stratigraphic and petrologic work revealed a complex volcanic evolution that can be summarized in six principal stages i construction of a shield like lava cone ii generation of unusual lithic rich ignimbrites apparently related to powerful eruptions that caused rapid and significant vent erosion these eruptions could have resulted from shallow magma water interactions iii eruption of peripheral fissural lava flows following a nnw sse trending fissure system iv period of dome growth and explosive collapse v short period of repose followed by open vent explosive magmatic and hydromagmatic eruptions vi radial eruption of lava flows related to a ring fissural system geochemistry data of late miocene volcanics show a continental arc magmatic origin and show that crystal fractionation contributed strongly to magma differentiation several lava flows were erupted with a persistent nnw sse trending orientation and the entire late miocene geologic record is affected by highly dislocated normal faults with the same orientation this may indicate that late miocene volcanism was under tectonic control finally late miocene volcanics and the inception of the early trans mexican volcanic belt could be related to a shallow subduction angle influenced by a significant increase in the convergence rate along the middle american trench at about 20 ma

controls on the carbon isotopic composition of southern ocean phytoplankton carbon isotopic compositions of suspended organic matter and biomarker compounds were determined for 59 samples filtered from southern ocean surface waters in january 1994 along two north south transects woce sr3 from tasmania to antarctica and across the princess elizabeth trough pet east of prydz bay antarctica along the sr3 line bulk organic matter show generally decreasing 13c contents southward which are well correlated with increasing dissolved molecular carbon dioxide concentrations co2 aq this relationship does not hold along the pet transect using concentrations and isotopic compositions of molecular compounds we evaluate the relative roles of several factors affecting the 13c of southern ocean suspended particulate organic matter along the woce sr3 transect the concentration of co2 aq plays an important role it is well described by a supply versus demand model for the extent of cellular co2 utilization and its associated linear dependence of isotopic fractionation ep on the reciprocal of co2 aq an equally important factor appears to be changes in algal assemblages along the sr3 transect with their contribution to isotopic fractionation also well described by the supply and demand model when formulated to include the cell surface volume control of supply changes in microalgal growth rates appear to have a minor effect on ep along the pet transect algal assemblage changes and possibly changes in microalgal growth rates appear to strongly affect the carbon isotopic variations of suspended organic matter these results can be used to improve the formulation of modern carbon cycle models that include phytoplankton carbon isotopic fractionation

the influence of air sea exchange on the isotopic composition of oceanic carbon observations and modeling although the carbon isotropic composition of ocean waters after they leave the surface ocean is determined by biological cycling air sea exchange affects the carbon isotopic composition of surface waters in two ways the equilibrium fractionation between oceanic and atmospheric carbon increases with decreasing temperature in southern ocean surface waters this isotopic equilibrium enriches delta sup 13 c relative to the delta sup 13 c expected from uptake and release of carbon by biological processes alone similarly surface waters in the subtropical gyres are depleted in delta sup 13 c due to extensive air sea exchange at warm temperatures countering the tendency toward isotopic equilibration with the atmosphere a relatively slow process are the effects of the equilibration of co sub 2 itself a much faster process in regions where there is a net transfer of isotopically light co sub 2 from the ocean to the atmosphere e g the equator surface waters become enriched in sup 13 c whereas in regions where isotopically light co sub 2 is entering the ocean e g the north atlantic surface waters become depleted in sup 13 c a compilation of high quality oceanic delta sup 13 c measurements along with experiments performed using a zonally averaged three basin dynamic ocean model are used to explore these processes 40 refs 14more figs 1 tab less

carbon isotope composition of tropical surface water during the past 22 000 years carbon isotope values of many species of planktonic foraminifera are size dependant values of 13c of individual size fractions are therefore an integration of low 13c values of calcite precipitated in the juvenile growth stage and high values precipitated in later stages in general the selection of a particular size fraction for downcore studies has been subjective analysis of different size fractions of planktonic foraminifera however yields different time series in downcore studies by measuring the 13c of many size fractions the 13c precipitated throughout the growth of the foraminifera can be calculated time series of the 13c of calcite precipitated in the late growth stages of planktonic foraminifera from two nearby cores from the caribbean sea result in a better correlation than time series of constant size fractions these 13c records indicate similar 13c values during the last glaciation and the late holocene and a broad deglacial minimum approximately synchronous with a minimum in the 13c records of benthic foraminifera from intermediate depth atlantic cores the deglacial minimum may be a reflection of the isotopic composition of the underlying intermediate water which may be affected by circulation changes or changes in preformed 13c values and or of the flux of water upwelled into the surface layer the small 0 2 to 0 0 glacial interglacial 13c difference in tropical surface water is also believed to be affected by the chemistry of the underlying source water

the imprint of anthropogenic co2 in the arctic ocean evidence from planktic δ13c data from watercolumn and sediment surfaces 13c values of n pachyderma sin from the water column and from core top sediments are compared in order to determine the 13c decrease caused by the addition of anthropogenic co2 to the atmosphere this effect which is referred to as the surface ocean suess effect is estimated to be about 0 9 0 2 within the arctic ocean halocline waters and to about 0 6 0 1 in the atlantic derived waters of the southern nansen basin this means that the area where the arctic ocean halocline waters are formed the arctic shelf regions are relatively well ventilated with respect to co2 nevertheless 13c of dissolved inorganic carbon 13cdic in the arctic ocean halocline waters is far from isotopic equilibrium absolute values of 13c of n pachyderma sin covary with the surface ocean suess effect and we interprete changes in both parameters as a reflection of the degree of ventilation of the waters on the shelf sea measurements of 13c of n pachyderma sin in the arctic ocean from plankton tows reveal a vital effect of about 2 significantly different from other published values a first order estimate of the total anthropogenic carbon inventory shows that despite of its permanent sea ice cover the arctic ocean with 2 of the global ocean area is responsible for about 4 6 of the global ocean s co2 uptake

carbon isotope composition of caribbean sea surface waters response to the uptake of anthropogenic co2 1 the burning of fossil fuels and deforestation have significantly increased atmospheric co2 levels from 280 ppm prior to the industrial revolution to the present value of 390 ppm suess 1955 was the first to show that the carbon isotopic composition of the atmosphere is changing in response to the anthropogenic input of radiocarbon dead 13c depleted co2 from fossil fuel combustion here we report a high resolution planktonic foraminiferal 13c record from the caribbean sea for the last 300 years that clearly resolves the timing and magnitude of the marine 13c suess effect associated with the oceanic uptake of anthropogenically derived co2 cariaco basin sediment trap and upper most box core sediment 13c match both the trend and magnitude of observed 13c changes in atmospheric co2 over the last 15 years the longer sediment record suggests the marine suess effect to be 0 75 from pre industrial values with most of the change occurring since 1950 coincident with the rapid rise in atmospheric co2 noted in ice core and instrumental data if the current anthropogenic co2 emission trend continues extrapolating our marine 13c rate curve into the future suggests that the rate of marine 13c change caused by anthropogenic co2 will increase to 0 10 yr 1 by the end of this century an increase of more than an order of magnitude from 1950 values

cenozoic sequence stratigraphy of the central and northern north sea basin tectonic development sediment distribution and provenance areas the cenozoic succession in the central and northern north sea has been investigated to establish a regional sequence stratigraphic framework changes in sediment distribution indicate a complex pattern of regional vertical movements along older palaeozoic and mesozoic structures in cenozoic times these vertical movements mainly related to tectonic processes along the continental margin to the north and north west were responsible for the generation and removal of provenance areas for sediments delivered to the north sea basin through cenozoic time during the early through middle palaeogene sediments were mainly sourced from areas in the west and from the atlantic margin in the north uplift in the northern north sea in the late eocene was in the earliest oligocene followed by marked basin subsidence and tectonic uplift of southern norway a similar pattern of tectonic movements resulted in subaerial exposure of the northern north sea in the early miocene followed by significant tectonic subsidence in the basin and along the atlantic margin in late miocene pliocene times at the same time southern norway was uplifted and became a major sediment source after the miocene pliocene subsidence uplift events glacial processes in southern norway and fluvial processes in a large drainage area east and south east of the north sea were responsible for the main sediment influx to the north sea the cenozoic depositional sequences in the north sea developed in close interaction with regional tectonic movements and changes in provenance areas tectonic movements in north west europe overprinted global sea level changes so that the generation of depositional sequences and sequence boundaries apparently occurred independently of the rate of eustatic sea level change

crumbling of dacite dome lava and generation of pyroclastic flows at unzen volcano recent modelling of volcanic eruptions has shown that the efficiency of subsurface degassing of magmas determines whether magma erupts explosively or effuses quietly1 2 slow uprise of magma is often accompanied by effective degassing leading to the extrusion of lava flows and domes although lava dome extrusion is one of the less explosive modes of eruption it is often accompanied by explosive pyroclastic activities3 5 the 1991 eruption of unzen volcano provided an opportunity to observe at close range several types of small scale pyroclastic flow glowing avalanches originating from lava domes most of the pyroclastic flows are of merapi type caused by blocks falling from a collapsing dome others are of pelean type originating in an explosion from the side of a dome the lavas apparently show variable degrees of self explosivity we suggest that variable degrees of degassing of the magma produced a wide range of excess pore pressures in the extruded lava domes resulting in both merapi type and pelean type pyroclastic flows from the domes

suspected gas associated clay diapirism on the seabed off mid norway abstract on the continental shelf off mid norway at water depths ranging from 150 to 350 m large areas of the seabed consist of plastic clays with a rugged surface topography and an amorphous opaque subsurface acoustic appearance five topographic side scan sonar and shallow seismic examples are presented and discussed many of the mounds and ridges are suspected to be of a clay diapiric nature numerous gas seepages originating from opaque clays have also been found off mid norway a tentative formation model for the ridges and dome shaped features is proposed the model is based on suspected differential gas charging of subsurface sediments and clay diapirism caused by differential clay buoyancy

historical eruptions of merapi volcano central java indonesia 1768 1998 abstract information on merapi eruptive activity is scattered and much is remotely located a concise and well documented summary of this activity has been long needed to assist researchers and hazard mitigation efforts and the aim of this paper is to synthesize information from the mid 1700s to the present a descriptive chronology is given with an abbreviated chronology in a table that summarizes events by year assigns preliminary volcanic explosivity index vei ratings and hartmann classifications and provides key references the history of volcano monitoring is also outlined the study reveals that a major difference in eruption style exists between the twentieth and nineteenth centuries although the periodicity between larger events seems about the same during the twentieth century activity has comprised mainly the effusive growth of viscous lava domes and lava tongues with occasional gravitational collapses of parts of oversteepened domes to produce the nuees ardentes commonly defined as merapi type in the 1800s however explosive eruptions of relatively large size occurred to vei 4 and some associated fountain collapse nuees ardentes were larger and farther reaching than any produced in the twentieth century these events may also be regarded as typical eruptions for merapi the nineteenth century activity is consistent with the long term pattern of one relatively large event every one or two centuries based on the long term eruptive record deduced by others from volcanic stratigraphy it is uncertain whether or not a recurrence time model continues to apply to merapi but if so merapi could soon be due for another large event and its occurrence with only modest or inadequately appreciated precursors could lead to a disaster unprecedented in merapi s history because the area around the volcano is now much more densely populated

δ18o seasonality of planktonic foraminifera from southern ocean sediment traps latitudinal gradients and implications for paleoclimate reconstructions abstract the oxygen isotopic record obtained from globigerina bulloides globorotalia inflata and neogloboquadrina pachyderma s was analysed for 5 sediment traps moored in the southern ocean and southwest pacific the traps extend from subtropical to the polar frontal environments providing the first analysis of seasonal foraminiferal 18 o records from these latitudes comparison between the foraminiferal records and various equations for predicted 18 o of calcite reveals that the predicted 18 o is best captured by the equations of epstein et al 1953 epstein s buchsbaum r lowenstam h a urey h c 1953 revised carbonate water isotopic temperature scale geological society of america bulletin 64 1315 1326 and kim and o neil 1997 kim s t o neil j r 1997 equilibrium and non equilibrium oxygen isotope effects in synthetic carbonates geochimica et cosmochimica acta 61 3461 3475 the epstein equation shows a constant offset from the 18 o of g bulloides and n pachyderma s across the full range of latitudes the seasonal range in 18 o values for these two species implies a near surface habitat across all sites while g inflata most likely dwells at 50 m depth a significant finding in this study was that offsets from predicted 18 o for g bulloides do not correlate to changes in the carbonate ion concentration this suggests that co 3 2 in and of itself may not capture the full range of carbonate chemistry conditions in the marine system this sediment trap deployment also reveals distinct seasonal flux patterns for each species comparison between flux weighted isotopic values calculated from the sediment traps and the isotopic composition of nearby surface sediments indicates that the sedimentary records retain this seasonal imprint at the 51 s site g bulloides has a spring flux peak while n pachyderma s is dominated by summer production the imprint of these differing seasonal production patterns on the flux weighted 18 o values results in more depleted 18 o for n pachyderma s than for g bulloides interpretations of n pachyderma s isotopic composition as a record of subsurface conditions may therefore need to be refined with implications for interpretation of depleted glacial 13 c for this species sigman boyle 2000 sigman d m boyle e a 2000 glacial interglacial variations in atmospheric carbon dioxide nature 407 859 869

carbon isotopes and habitat of polar planktic foraminifera in the okhotsk sea the carbonate ion effect under natural conditions the upper 500 or 1000 m of the water column in the okhotsk sea was sampled for living planktic foraminifera the polar species neogloboquadrina pachyderma sinistral strongly dominates the foraminiferal assemblage the subpolar to temperate species globigerina bulloides accounts for 10 25 other species account for up to 3 only the shell 18o and 13c values of the species n pachyderma sin are compared to water 18o values and 13c values of dissolved inorganic carbon dic the strong gradient in 18o composition and temperature in the upper water column is reflected in the 18o of n pachyderma sin relative to the values expected for inorganic calcite precipitated under equilibrium conditions n pachyderma sin displays a vital effect of about 1 in 18o the 13c composition of n pachyderma sin is about constant with water depth and the reflection of 13cdic in the foraminiferal shell seems to be masked by other effects most foraminifera are found above or slightly below the thermocline and can be assumed to calcify in the upper 200 m of the water column the gradient of 13cdic extends well below this depth therefore the lack of correlation can partly be attributed to this fact the remaining discrepancy between 13c of n pachyderma sin and 13cdic correlates with the carbonate ion concentration in the water column this leads to the conclusion that the carbonate ion effect cie which has been derived from culturing experiments for other species spero et al 1997 nature 390 497 500 is found here under natural conditions when the magnitude of the cie derived for g bulloides is applied to n pachyderma sin cie corrected 13c of n pachyderma sin is a direct reflection of 13cdic in the water column with a constant offset of 1 2

mud volcanoes in deepwater nigeria abstract detailed study of 3d seismic data from deepwater nigeria has revealed the presence of features interpreted to be mud volcanoes they occur in an upper slope environment seen as 1 2 km circular features at the seabed seabed cores from the mud volcanoes contain oil gas and sand shale clast content richer than the seabed background pliocene fossils have been identified in the cores demonstrating transport of material from depth the features show a high seabed seismic amplitude above a chimney of chaotic seismic reflections and data wipe out the mud volcanoes in the study area shows two distinct clusters located over deeper structural culminations four active mud volcanoes area 1 are located above a rollover anticline in the central part of the area cuspate listric faults reach the seabed on the up slope side of these mud volcanoes four abandoned mud volcanoes have also been identified with progressively older ages towards the crest of the underlying structure these abandoned features are associated with an extremely chaotic seismic signature a combination of over pressured carrier beds and low integrity top seals are believed to be responsible for the formation of these mud volcanoes it is further believed that gas expansion subsequent to seal failure was the main driving force for what must have been violent eruptions the long lived mud volcano activity over the deep structural closure suggests a plumbing system that focuses on escaping compaction water and hydrocarbons through time in the south west of the study area another cluster of five mud volcanoes is located above a shale diapir the seabed expression of the members of this cluster is more varied some show a positive relief at the seabed while others show circular depressions the largest feature represents an assemblage of many smaller mud volcanoes with a common root system their seismic expression is also different from that of area 1 with a well defined sediment wedge at surface and a shallower root system these features are believed to represent a less violent type of mud volcano characterised by ductile flow tectonic stress due to growth of the underlying diapir is thought to have played an important role during eruption in addition to focused methane escape and the low mechanical strength of the overburden

sea surface temperature estimates from the southwest pacific based on planktonic foraminifera and oxygen isotopes planktonic foraminiferal census data were collected on 34 surficial sediment samples from east of new zealand sea surface temperature estimates were derived from the data using the modern analogue technique mat and compared to data from climap s fa 20 equation they were also computed from oxygen isotope analyses of globigerina bulloides the temperature estimates compared well between the three methods and were found to correlate closely with the appropriate seasonal sea surface temperature as measured by satellite the foraminiferal assemblages and derivative temperatures clearly identify the major watermasses and oceanic fronts in the region and thus can be applied to palaeoceanographic analysis of southwest pacific sediments

volcanic dry avalanche deposits identification and comparison with nonvolcanic debris stream deposits abstract a volcanic dry avalanche deposit is defined as a volcaniclastic deposit formed as a result of a large scale sector collapse of a volcanic cone associated with some form of volcanic activity avalanche transport occurred in response to the gravitational field in a manner similar to the transport of nonvolcanic debris streams e g hsu 1975 such deposits are characterized by megablock structure deformed and fractured large blocks up to several hundreds meters in diameter a megablock preserves original layering intrusive contacts or weathered surfaces of the source volcanic edifice surface topography of the deposit is characterised with hummocky relief ratios of fell height to travel distance for volcanic dry avalanche deposits are between 0 18 and 0 06 this range is similar but smaller than the value of 0 58 to 0 08 for nonvolcanic debris stream deposit this similarity suggests similar transportation mechanisms excessive travel distances as defined by hsu 1975 calculated for volcanic dry avalanche deposits give values larger than for debris stream deposits of the same volume the difference is explained by lower rigidity of the collapsing mass due to the existence of soft pyroclastic layers alteration around the vent development of fractures owing to new cryptodome intrusion and boiling of supercritical fluid contained within the collapsed mass

the interaction of volcanism and sedimentation in the proximal areas of a mid tertiary volcanic dome field central arizona u s a abstract exposures of an oligocene small volume dome field in central arizona usa provide an excellent example of the interaction of volcanism and sedimentation in a proximal volcanic setting volcanism in the field began with eruption of a shoshonite cinder cone and lava flows which were emplaced onto braided stream gravels stream sediments aggraded to the top of the lava flows before eruption of an amphibole trachyte dome and its derivative pyroclastic flows deposition from the pyroclastic flows was punctuated by fluvial sedimentation which took the form of both sheetflow reworking and debris flow and hyperconcentrated flow deposition the lack of pronounced channel formation may indicate that inter eruptive periods were brief two principles of volcaniclastic sedimentation are well documented in this study first active aggradation may preserve proximal deposits that are normally eroded quickly from a volcano this aggradation is seen in the interstratification of braided stream gravels derived from outside the area of volcanism with dome derived primary pyroclastic deposits the growing dome apparently did not form a large topographic feature and thus did not overwhelm the preservation caused by regional aggradation the landscape response to volcanism was highly complex and the response of the stream system to short term volcanic processes merely accentuated the effects occurring due to longer term tectonic subsidence second because sediments in the proximal areas of the dome were preserved the interaction of the regional dispersal system with the dome complex is clear pyroclastic deposits were in some cases localized in channels reworked pyroclastic deposits have structures indicative of sheetflow or mass flow but are entirely pyroclastic in composition deposits strongly influenced by the regional system are also mass flows or sheetflows but they contain appreciable concentrations of non volcanogenic material and were deposited by debris choked braided streams

using species specific paleotemperature equations with foraminifera a case study in the southern california bight abstract species specific paleotemperature equations were used to reconstruct a record of temperature from foraminiferal 18 o values over the last 25 kyr in the southern california bight the equations yield similar temperatures for the 18 o values of globigerina bulloides and neogloboquadrina pachyderma in contrast applying a single paleotemperature equation to g bulloides and n pachyderma 18 o yields different temperatures which has been used to suggest that these species record the surface to thermocline temperature gradient in santa barbara basin an isotopically distinct morphotype of g bulloides dominates during glacial intervals and yields temperatures that appear too cold when using a paleotemperature equation calibrated for the morphotype common today when a more appropriate paleotemperature equation is used for glacial g bulloides we obtain more realistic glacial temperatures glacial interglacial temperature differences g i t calculated in the present study indicate significant cooling 8 10 c throughout the southern california bight during the last glacial maximum lgm the magnitude of glacial cooling varies from 8 c near the middle of the southern california bight tanner basin and san nicolas basin to 9 c in the north santa barbara basin and 9 5 10 c in the south velero basin and no name basin our temperature calculations agree well with previous estimates based on the modern analog technique in contrast studies using n pachyderma coiling ratios u k 37 indices and transfer functions estimate considerably warmer lgm temperatures and smaller g i t

carbon isotopes in recent planktonic foraminifera a record of anthropogenic co2 invasion of the surface ocean abstract the release of isotopically light anthropogenic co 2 into the ocean atmosphere carbon reservoir has resulted in a decrease in the carbon isotopic composition of the surface ocean in this paper we examine differences between the carbon isotope composition of planktonic foraminifera from sediment traps with older late holocene material to estimate the change in 13 c 13 c in eastern atlantic surface waters as a result of the invasion of anthropogenic co 2 using stable oxygen isotopes we demonstrate that average trap values for a variety of species are more or less identical to core top values suggesting that foraminifera recovered in sediment traps are representitive of foraminifera deposited in the sediments however carbon isotopes recorded in planktonic foraminifera from recent trap material reveal a decrease in the 13 c composition of all species relative to the core top samples although the magnitude of the decrease varies significantly between species surface dwelling foraminifera g ruber g bulloides show 13 c values of 0 53 to 0 62 which is similar to other estimates from shallow water coral and sponge records for the decrease in the 13 c composition of dissolved organic carbon in surface waters which has taken place since the start of the anthropogenic emissions the magnitude of decrease in the 13 c of surface waters suggested by these records is also close to that predicted by global carbon cycle models deeper thermocline dwelling foraminifera such as g inflata however show 13 c values 0 2 which are substantially lower than their surface dwelling counterparts this reduction in 13 c with increasing depth habitat within the mixed layer may be related to limited vertical penetration of anthropogenic co 2 as a result of the strong upwelling which is observed in the eastern atlantic along the northwest african margin

southwest pacific subtropics responded to last deglacial warming with changes in shallow water sources this study examined sources of mixed layer and shallow subsurface waters in the subtropical bay of plenty new zealand across the last deglaciation 30 5 ka 18o and 13c from planktonic foraminifera globgerinoides bulloides and globorotalia inflata in four sediment cores were used to reconstruct surface mixed layer thickness 18o of seawater 18osw and differentiate between high and low latitude water provenance during the last glaciation depleted planktonic 18osw and enriched 13c 0 4 0 1 indicate surface waters had southern ocean sources a rapid 13c depletion of 1 in g bulloides between 20 and 19 ka indicates an early permanent shift in source to a more distal tropical component likely with an equatorial pacific contribution that persisted into the holocene at 18 ka a smaller but similar shift in g inflata 13c depletion of 0 3 suggests that deeper subsurface waters had a delayed reaction to changing conditions during the deglaciation this contrasts with the isotopic records from nearby hawke bay to the east of the north island of new zealand which exhibited several changes in thermocline depth indicating switches between distal subtropical and proximal subantarctic influences during the early deglaciation ending only after the antarctic cold reversal our results identify the midlatitude subtropics such as the area around the north island of new zealand as a key region to decipher high versus low latitude influences in southern hemisphere shallow water masses

temporal constraints on the growth and decay of large scale mobilized mud masses and implications for fluid flow mapping in sedimentary basins seismic stratigraphic analysis of the cretaceous to succession of the uer terrace north sea seabed basin norway demonstrates that the upper oligocene succession has undergone large scale mobilization of mudstone dominated units due to the upward migration of water and associated hydrocarbons into the interval which is in some way linked to a period of gas expulsion from adjacent deep basins seismic stratigraphic analysis of units overlying the mobilized zones indicates they created positive seafloor topography during the late miocene implying gaseous fluids were expelled at the seabed loading by the overlying pliocene succession caused the mobilized mud masses to deflate and resulted in the formation of low relief fault bounded craters the results of this study have implications for understanding the location and timing of fluid flow in sedimentary basins

defining the 3d geometry of thin shale units in the sleipner reservoir using seismic attributes acknowledgments the seismic interpretation and image processing was carried out in the seislab facility at the university of aberdeen sponsored by bg bp and chevron seismic imaging analysis was performed using geoteric ffa and analysis of seismic amplitudes was performed in petrel 2015 schlumberger we would like to thank the nddc rg11766 10 for funding this research and statoil for the release of the sleipner field seismic dataset utilized in this research paper and also anne kari furre and her colleagues for their assistance we also thank the editor alejandro escalona and the two anonymous reviewers for their constructive and in depth comments that improved the paper

does carbon 13 track anthropogenic co2 in the southern ocean a multiparametric linear regression technique was used for waters in the southern ocean to estimate the change in both 13 c dic 13 c dic and dissolved inorganic carbon dic dic between 1978 and 1998 due to the accumulation of anthropogenic co 2 the observed decrease in 13 c dic at the surface the suess effect was 0 015 0 003 yr 1 in the sub antarctic zone and 0 005 0 003 yr 1 in the antarctic zone similar to values reported for the southern indian ocean gruber et al 1999 sonnerup et al 2000 to compare the 13 c dic with adic we used the ratio of these two anomalies rc 13 c dic dic mol kg 1 1 along the section arc ranged from 0 015 0 005 at 42 s to 0 007 0 005 mol kg 1 1 at 54 s the spatial variability in arc in the southern ocean reflects different timescales for processes controlling the uptake of 13 c from those controlling the uptake of 12 c and indicates that 13 c dic decouples from adic poleward of the sub antarctic zone the variations of arc along the section suggest that the 13 c dic anomaly is not a good predictor of the anthropogenic co 2 inventory in the southern ocean some methods for determining anthropogenic co 2 uptake both on the global and regional scale assume the penetration depths of 13 c dic to be the same as adic which implies a constant value for arc in the ocean at 0 016 mol kg 1 1 heimann and maier reimer 1996 ortiz et al 2000 bauch et al 2000 the use of a constant arc and the observed 13 c dic to estimate anthropogenic co 2 could lead to an underestimate in the inventory of anthropogenic co 2 for the southern ocean by 50

monogenetic volcanism personal views and discussion monogenetic volcanism produces small volume volcanoes with a wide range of eruptive styles lithological features and geomorphic architectures they are classified as spatter cones scoria or cinder cones tuff rings maars maar diatremes and tuff cones based on the magma water ratio dominant eruption styles and their typical surface morphotypes the common interplay between internal such as the physical chemical characteristics of magma and external parameters such as groundwater flow substrate characteristics or topography plays an important role in creating small volume volcanoes with diverse architectures which can give the impression of complexity and of similarities to large volume polygenetic volcanoes in spite of this volcanic facies complexity we defend the term monogenetic volcano and highlight the term s value especially to express volcano morphotypes this study defines a monogenetic volcano a volcanic edifice with a small cumulative volume typically 1 km3 that has been built up by one continuous or many discontinuous small eruptions fed from one or multiple magma batches this definition provides a reasonable explanation of the recently recognized chemical diversities of this type of volcanism

overview of the eruption of soufriere hills volcano montserrat 18 july 1995 to december 1997 the onset of phreatic volcanic activity at the soufriere hills volcano montserrat on 18 july 1995 followed a three year period of heightened volcano seismic activity beneath the island phreatic explosions gave way to continuous eruption of juvenile andesitic magma in the form of a lava dome on or around 15 november 1995 magma production rate has varied leading to changes in eruptive style an explosive eruption on 17 september 1996 followed a period of enhanced dome growth and large scale gravitational collapses from its eastern flank increasing dome volume led to stressing and overtopping of the confining crater walls to the southwest north and west during early 1997 sustained high magma production rate since june 1997 has led to three periods of major gravitational dome collapses followed by vulcanian explosive eruptions dome growth re started immediately after the cessation of the latest of these explosive phases in october 1997 and continues as of december 1997

planktonic foraminiferal flux seasonality in subantarctic sediment traps a test for paleoclimate reconstructions sediment trap moorings deployed during 1997 and 1998 in the subantarctic to polar frontal regions of the southern ocean reveal distinct seasonality in foraminiferal flux foraminiferal assemblages vary between each site yet major species exhibit very similar patterns of seasonal succession which can be associated with changes in mixed layer depth enhanced foraminiferal productivity is also associated with periods of high biogenic silica and particulate organic carbon flux on a broader scale foraminiferal assemblages are strongly delineated by temperature temperature estimates derived from the assemblages using the modern analog technique mat are mostly within 2 5 c of the satellite advanced very high resolution radiometer temperatures observed during the deployment period this indicates that core top sediments included in the mat database do reflect modern observed conditions at the sea surface providing a robust technique for estimating past temperature change from foraminiferal assemblages in southern ocean environments

evolution of a complex isolated dome system cerro pizarro central mexico cerro pizarro is an isolated rhyolitic dome in the intermontane serdan oriental basin located in the eastern trans mexican volcanic belt cerro pizarro erupted 1 1 km3 of magma at about 220 ka activity of cerro pizarro started with vent clearing explosions at some depth the resultant deposits contain clasts of local basement rocks including cretaceous limestone 0 46 ma welded tuff and basaltic lava subsequent explosive eruptions during earliest dome growth produced an alternating sequence of surge and fallout layers from an inferred small dome as the dome grew both vertically and laterally it developed an external glassy carapace due to rapid chilling instability of the dome during emplacement caused the partial gravitational collapse of its flanks producing various block and ash flow deposits after a brief period of repose re injection of magma caused formation of a cryptodome with pronounced deformation of the vitrophyric dome and the underlying units to orientations as steep as near vertical this stage began apparently as a gas poor eruption and no explosive phases accompanied the emplacement of the cryptodome soon after emplacement of the cryptodome however the western flank of the edifice catastrophically collapsed causing a debris avalanche a hiatus in eruptive activity was marked by erosion of the cone and emplacement of ignimbrite derived from a caldera to the north of cerro pizarro the final growth of the dome growth produced its present shape this growth was accompanied by multiple eruptions producing surge and fallout deposits that mantle the topography around cerro pizarro the evolution of the cerro pizarro dome holds aspects in common with classic dome models and with larger stratovolcano systems we suggest that models that predict a simple evolution for domes fail to account for possibilities in evolutionary paths specifically the formation of a cryptodome in the early stages of dome formation may be far more common than generally recognized likewise sector collapse of a dome although apparently rare is a potential hazard that must be recognized and for which planning must be done

the influence of air and sea exchange on the carbon isotope distribution in the sea we explore here the influence of the temperature dependence of isotope fractionation between atmospheric co2and ocean co2 on the distribution of carbon isotopes in the ocean this is accomplished by an analysis of departures from the expected redfield tie between po4 and 13c we find that for the surface ocean the temperature influence largely compensates for the biologic influence in the deep ocean the temperature influence imprinted at the sites of deepwater formation reduces somewhat the biologically induced difference between the carbon isotope ratios for deep waters produced in the northern atlantic and in the antarctic these same features are reproduced in the hamburg ocean model in order to assess the impact of changes in the ratio of ocean mixing rate to wind speed we have made a model run in which co2 exchange rates between air and sea were everywhere doubled as expected the influence of the thermodynamic effect on the oceanic carbon isotope distribution is magnified

glacial differences of southern ocean intermediate waters in the central south pacific abstract southern ocean intermediate waters soiws such as antarctic intermediate water and subantarctic mode water play a key role in modulating the global climate on glacial interglacial time scales they link the southern ocean and the tropics via mechanisms such as oceanic tunneling that transport climatic signals across latitudes despite their importance the past evolution of the soiws in the central south pacific is largely unknown here we compare paired mg ca temperature stable carbon 13c and oxygen 18o isotope records from surface dwelling and deep dwelling planktic foraminifera to infer changes in the water column structure for the last 260 ka in the central south pacific 54 s our study focuses on the subsurface oceanographic variability controlled by soiws which are subducted at the subantarctic front our data show that the subsurface ocean in the central south pacific was colder and fresher during glacial stages than during the holocene 0 10 ka bp suggesting a general glacial enhanced presence of antarctic intermediate water in agreement with previous studies from the eastern equatorial pacific and the southeast pacific however the subsurface ocean salinity differs for both glacial stages with fresher condition during the last glacial maximum lgm 26 5 19 ka bp and more saline condition during the penultimate glacial maximum pgm 155 140 ka bp the 13c data also show contrasting conditions for both glacial time windows in the upper water column with a large depletion of 0 37 in 13c from the lgm values suggests a larger contribution of old low 13c deep waters at intermediate depths at the study site during the pgm plausibly due to stronger upwelling in high southern latitudes the dissimilar scenarios between the lgm and the pgm may have been caused by processes that are analogous to the phase switch in modern day southern annular mode

carbon isotopic disequilibrium between seawater and air in the coastal northern south china sea over the past century six coastal sediment cores collected from the northern south china sea were dated by 210 pb and analyzed for stable carbon and oxygen isotope composition of planktonic foraminifer globigerinoides ruber d 13 cgr and d 18 ogr three of these cores were located east of hainan island and the other three off the pearl river estuary pre surface seawater d 18 o and dissolved inorganic carbon dic d 13 c were identified as the dominant factors controlling downcore variations of d 18 ogr and d 13 cgr respectively results of d 13 cgr were then used to study surface water d 13 cdic and its relation to d 13 c of atmospheric co2 d 13 catm over the past century downcore records showed rather constant d 13 cgr in cores off hainan island but moderate decreases of d 13 cgr at rates between 0 006 and 0 009 per year in cores off the pre isotopic disequilibrium between d 13 cdic and d 13 catm was observed with d 13 cdic apparently higher than expected at equilibrium with d 13 catm except at the site closest to the pre the relatively steady d 13 cgr values east of hainan island were explained by balanced vertical mixing and biological pump whereas the moderate d 13 cgr decreases with time off the pre were attributable to fluvial input of

piercement shale diapirism in the deep water vema dome area voring basin offshore norway abstract within the norwegian 15th round deep water production licence no 217 on the voring plateau on the norwegian continental slope there is an unusually rugged seafloor topography our study addresses new 2d 3d and bathymetric data acquired in the vema dome area where evidence for active piercement shale diapirism is found the cores of the shale diapirs consist of coccolith oozes deposited during the paleocene and miocene individual shale diapirs and diapiric escarpments rise up to 70 m above the general sea floor at 1200 m water depth one of the key questions in our study has been to find out why diapirism is triggered over the vema dome and not over the nearby nyk high which has similar buried deposits of coccolith oozes on the basis of interpretations of the new data we conclude that the triggering is caused by a combination of at least three factors a a buried low density high porosity layer of deformable material the coccolith ooze b a doming substratum which causes extension and faulting c migration of light hydrocarbons through some of the faults and fault zones a fourth factor which probably contributes to triggering is tectonic instability the one factor that discriminates the vema dome area from the neighbouring nyk high area is the dome itself we therefore suspect that this in some way is the main factor responsible for the triggering furthermore we conclude that the process of piercement shale diapirism in the vema dome area is probably still active but because the movement of the sediments is suspected to be very slow it should be of only minor concern to future oil field development

constraining the depth and timing of large scale conical sandstone intrusions kilometer scale sandstone intrusions a recently recognized end member of the spectrum of soft sediment deformation structures are important components of many deep water sandstone reservoirs they result from the remobilization of considerable volumes of sand during early stages of burial this paper uses three dimensional seismic data calibrated to nearby wells to describe an extensive system of large downward tapering conical sandstone intrusions from the faeroe shetland basin on the uk atlantic margin the intrusions are derived from a middle eocene submarine fan and are injected vertically upward through overlying highly faulted claystones to form conical bodies that interconnect across the 700 m thick claystone interval to feed a set of shallow intrusions located within a few hundred meters of the paleoseabed the forcible intrusion of these shallow sandstone bodies produced complementary folding of the contemporaneous seabed the subsequent onlap of these seabed domal folds took place immediately after the intrusion event and by correlation to biostratigraphic data from nearby wells we date these intrusions as late miocene this is the first time that both the age and emplacement depth range of a system of large scale sandstone intrusions have been constrained

comment on seismic chimneys in the southern viking graben implications for palaeo fluid migration and overpressure evolution by karstens and berndt

pyroclastic flows generated by gravitational instability of the 1996 97 lava dome of soufriere hills volcano montserrat numerous pyroclastic flows were produced during 1996 97 by collapse of the growing andesitic lava dome at soufriere hills volcano montserrat measured deposit volumes from these flows range from 0 2 to 9 106 m flows range from discrete single pulse events to sustained large scale dome collapse events flows entered the sea on the eastern and southern coasts depositing large fans of material at the coast small runout distance 1 km flows had average flow front velocities in the order of 3 10 m s while flow fronts of the larger runout distance flows up to 6 5 km advanced in the order of 15 30 m s many flows were locally highly erosive field relations show that development of the fine grained ash cloud surge component was enhanced during the larger sustained events periods of elevated pyroclastic flow productivity and sustained dome collapse events are linked to pulses of high magma extrusion rates

seasonal nutrient depletion and carbon export in the subantarctic and polar frontal zones of the southern ocean south of australia seasonal surface water nitrate and phosphate depletions were calculated for the subantarctic zone saz and polar frontal zone pfz of the southern ocean along the world ocean circulation experiment sr3 repeat section south of tasmania australia and three other transects slightly to the west the depletions were calculated between a single winter july section and eight other sections from october to march in the years 1991 1998 and corrected for frontal movements and changes in water masses between the cruises using observed quasi linear nutrient salinity relationships arranged in a seasonal progression depletion began in approximately october and continued through march in good agreement with satellite biomass based estimates of production nitrate depletion in the saz 510 mmol n m 2 was approximately twice that of the pfz 250 mmol n m 2 but phosphate depletions were similar 29 and 24 mmol p m 2 for the saz and pfz respectively the saz exhibited a redfield n p depletion ratio 15 1 2 3 but the pfz ratio was much lower 8 3 5 4 while the saz exhibits greater seasonal nutrient depletion the relative magnitudes of export in the two zones remain uncertain because supply of nutrients from south of the polar front may lower the observed nutrient depletions in the pfz however comparisons with sediment trap and production measurements for the region south of australia suggest the saz and pfz differences derive from differences in production assuming a redfield c n ratio 6 6 carbon export for the longest period examined july march averaged 3400 430 mmol c m 2 in the saz with a range between 2700 and 3900 mmol c m 2 depending on latitude in the pfz carbon export averaged 1600 350 mmol c m 2 with a range of 1100 to 2000 mmol c m 2 these averages represent minimum annual export production estimates because neither resupply nor export outside the july march observational period is included

deposits of the 30 march 1956 directed blast at bezymianny volcano kamchatka russia on 30 march 1956 a catastrophic directed blast took place at bezymianny volcano it was caused by the failure of 0 5 km3 portion of the volcanic edifice the blast was generated by decompression of intra crater dome and cryptodome that had formed during the preclimactic stage of the eruption a violent pyroclastic surge formed as a result of the blast and spread in an easterly direction effecting an area of 500 km2 on the lower flank of the volcano the thickness of the deposits although variable decreases with distance from the volcano from 2 5 m to 4 cm the volume of the deposit is calculated to be 0 2 0 4 km3 on average the deposits are 84 juvenile material andesite of which 55 is dense andesite and 29 vesicular andesite on a plot of sorting vs median diameter inman coefficients the deposits occupy the area between the fall and flow fields in the proximal zone less than 19 km from the volcano three layers can be distinguished in the deposits the lower one layer a is distributed all over the proximal area is very poorly sorted enriched in fragments of dense juvenile andesite and contains an admixture of soil and uncharred plant remains the middle layer layer b is distributed in patches tens to hundreds of metres across on the surface of layer a layer b is relatively well sorted as a result of a very low content of fine fractions and it contains rare charred plant remains the uppermost layer layer c forms still smaller patches on the surface of layer b layer c is characterized by intermediate sorting is enriched in vesicular juvenile andesitic fragments and contains a high percentage of the fine fraction and very rare plant remains which are thoroughly charred maximum clast size decreases from layer a to layer c the absence of internal cross bedding is a characteristic of all three layers in the distal zone more than 19 km from the volcano stratigraphy changes abruptly deposit here consists of one layer 26 to 4 cm in thickness is composed of wavy laminated sand with a touch of gravel is well sorted and contains uncharred plant remains the bezymianny blast deposits are not analogous with known types of pyroclastic surges with the exception of the directed blast deposits of the mount st helens eruption of 18 may 1980 the peculiarities of deposits from these two eruptions allow them to be separated into a special type blast surge this type of surge is formed when failure of volcanic edifice relieves the pressure from an inter crater dome and or cryptodome a model is proposed to explain the peculiarities of the formation transportation and emplacement of the bezymianny blast surge deposits

transport and deposition of a pyroclastic surge across an area of high relief the 18 may 1980 eruption of mount st helens washington the 08 32 pdt 18 may 1980 mount st helens eruption began as an explosion blast that produced a laterally flowing pyro clastic current blast surge it moved outward in a 180 arc at supersonic speeds and then slowed to subsonic speeds supersonic flow severely eroded the ground and produced a ground layer formerly layer a0 above the ground layer lies the deposit derived from the blast surge the blast surge deposits formed in three continuous and concurrent stages the first stage was movement of the transport system that is the blast surge carrying fragments most of the distance from the vent the next two stages involved the depositional system this system developed from rapidly accumulating sediment by gravity segregation at the base of the blast surge two stages of sediment gravity flows with independent flow regimes formed sequentially in rapid succession from the moving blast surge each moved downhill due to gravity independently of the generating blast surge that was driven by explosive expansion units repeated in some sections are deposits derived from divergent and crossing surge lobes caused by irregular topography locally ponded massive deposits in valleys and depressions formed from gas rich pyroclastic flows and originated in two ways 1 topographic blocking by steep volcano facing slopes blocking includes diversion or damming of the lower elevation high density part of the blast surge that could not surmount high ridges 2 also occurring to form valley ponds was drainage of just deposited or almost deposited material from steep slopes 30 35 moving downhill in all slope directions into separate valleys or depressions distances traveled by the blast surge and rates at which coarsest fragments decrease laterally are related to the topographic grain surge runout was farther where flow directions paralleled topographic trends and least where trends were at right angles to the flow obstacle interference depositional patterns thinning thickening rapid fine to coarse facies changes caused a spread in median diameter values that are as great in local areas near the volcano as they are over the width of the devastated region

a detailed tephrostratigraphic framework at merapi volcano central java indonesia implications for eruption predictions and hazard assessment abstract the upper part of merapi volcano is characterised by a summit crater breached to the southwest and occupied by an unstable lava dome episodes of dome growth have usually resulted in partial dome collapse events that have generated pyroclastic flows in recent years these have inundated the southwestern lower flanks and in the past other sectors of the volcano have been affected this recent pattern of volcanic activity since the 1880s is well known from direct observations in this study the eruptive record extending back to mid holocene times is deduced from the stratigraphy and chronology of volcaniclastic deposits this record forms an important basis from which the average periodicity of eruptions at merapi and the severity and the extent of future eruptions can be assessed the most complete record of eruptive activity from merapi volcano is found in the deeply dissected volcaniclastic fans of the lower flanks here successions of numerous coarse ash and lapilli beds are interbedded with andic soil material thin pyroclastic flow and surge deposits and a hitherto unrecognised inter regional tephra marker bed many of these tephra beds can be reliably correlated around the flanks of merapi volcano and can be distinguished on the basis of physical appearance and stratigraphic association these formations can be reliably used to correlate units around the flanks of the volcano in the deeper parts of this stratigraphic succession pyroclastic products originating from the adjacent merbabu volcano are also recognised and provide evidence of concurrent activity at both volcanoes it is clear from the stratigraphic record that relatively large magnitude eruptive volume to 3 7 108 m3 eruptions have been generated at merapi volcano these eruptive deposits are typically produced from pyroclastic flow and or pyroclastic fall events most of the fall beds are characterised by single to multiple upward fining pumiceous or scoriaeous units sometimes overlain by ash cloud surge beds isopach maps have been produced for several of these tephra beds and most of them show either west southwest south and southeast dispersion except for the ngrangkah tephra which shows no systematic direction or distribution sub plinian or plinian to vulcanian open vent styles of activity appear to have been common at merapi volcano such eruptive episodes are in contrast with the style of activity that had been occurring at merapi volcano in the last two centuries clearly the range of eruptive events likely to be experienced at merapi volcano needs to be more critically considered in any existing or future hazard assessment and contingency planning programme

planktonic foraminiferal δ13c records from southern ocean sediment traps new estimates of the oceanic suess effect the carbon isotopic composition is measured for three species of planktonic foraminifera globigerina bulloides globorotalia inflata and neogloboquadrina pachyderma s from southern ocean sediment traps the sediment traps represent the annual flux of foraminifera in subtropical to polar frontal environments from the western pacific southern australia sector comparison between the seasonal 13c composition of the foraminifera and estimated 13c of dissolved inorganic carbon dic allows disequilibrium effects to be determined disequilibrium exhibits a latitudinal trend with greatest offsets from equilibrium at lower latitudes this effect causes a north to south increase in foraminiferal 13c while the 13cdic displays a decrease across these latitudes disequilibrium in g bulloides can be accounted for by changes in temperature the relationship between disequilibrium and temperature which we derive in this field study is consistent with the laboratory relationship of bemis et al 2000 corrected 13c for g bulloides is closely correlated to seasonal changes in nutrients at each site indicating the utility of g bulloides 13c as a nutrient tracer in southern ocean environments comparison between flux weighted sediment trap values and nearby core tops indicates a modern depletion in 13c which we attribute to the oceanic suess effect the imprint of this effect on the foraminiferal isotopes provides further evidence for the equilibration between surface waters and the atmosphere in the subantarctic zone

episodic basin wide fluid expulsion from geopressured shale sequences in the north sea basin a proposed general model for the episodic dewatering of thick shale successions is based on the recognition of a pervasive polygonal extensional fault network developed in the dominantly fine grained lower tertiary of the north sea basin seismic data show that the faults are arranged in stratigraphically bound structural units tiers that are delimited vertically by almost undeformed condensed sections and are restricted in distribution to the lowest permeability slope and basin floor facies i propose an episodic three stage mechanism to explain the fault genesis involving 1 the development of basin wide overpressured compartments 2 a density inversion between the overpres sured units and the overlying seal and 3 natural hydraulic fracturing pressure bleed off and resealing of the pressure compartment leading to a repeat of the cycle

seasonal variability of δ18o and δ13c of planktic foraminifera in the bering sea and central subarctic pacific during 1990 2000 we evaluated a 10 year time series of 18o and 13c records from three planktic foraminifers neogloboquadrina pachyderma globigerina umbilicata and globigerinita glutinata in the bering sea and central subarctic pacific with a focus on their responses to environmental changes foraminiferal 18o followed the equilibrium equation for inorganic calcite with species specific equilibrium offsets ranging from nearly zero 0 02 for n pachyderma and 0 01 for g umbilicata to 0 16 g glutinata equilibrium offsets in our sediment trap samples were smaller than those from plankton tow studies implying that foraminiferal 18o was modified by encrustation during settling habitat calcification depths varied from 35 55 m n pachyderma and g umbilicata or 25 45 m g glutinata during warm stratified seasons to around 100 m during winter when the mixed layer depth increases unlike 18o foraminiferal 13c showed species specific responses to environmental changes we found a dependency of 13c in g umbilicata on co32 concentrations in ambient seawater that agreed reasonably well with published laboratory results suggesting that 13c of g umbilicata is subject to vital effects in contrast 13c of n pachyderma and g glutinata are likely affected by other species specific biological activities seasonal flux patterns reveal that fossil records of n pachyderma and g glutinata represent annual mean conditions whereas that of g umbilicata most likely indicates those of a specific season because none of these three taxa was abundant from december to february their fossil records likely do not reflect isotope signals from cold seasons

controls on stable isotope and trace metal uptake in neogloboquadrina pachyderma sinistral from an antarctic sea ice environment article the polar foraminifera neogloboquadrina pachyderma sinistral dominates assemblages from the high latitude southern ocean which plays a key role in determining past climate due to the tight linkage between antarctic temperature and atmospheric co2 here we use n pachyderma s harvested from sediment traps off the west antarctic peninsula to construct a seasonal time series for the calibration of calcite proxies in a high latitude seasonal sea ice environment where temperature is decoupled from other environmental parameters we have used a combination of 18 ocaco3 and 13 ccaco3 to decipher the calcification temperature and salinity which reflect that n pachyderma s live in surface waters throughout the year and at the ice water interface in austral winter further our results demonstrate that the uptake of trace metals into n pachyderma s calcite is influenced by secondary environmental conditions in addition to temperature during periods of sea ice cover we propose an elevated carbonate ion concentration at the ice water interface resulting from biological utilisation of co2 could influence calcification in foraminifera our calculations suggest that for n pachyderma s mg ca sr ca ratios and li ca ratios are linear functions of calcification temperature and co3 2 n pachyderma s mg ca ratios exhibit temperature sensitivity similar to previous studies 10 20 c and a sensitivity to co3 2 of 1 mol kg 1 sr ca ratios are less sensitive to environmental parameters exhibiting 5 increase c and 0 5 10 mol kg 1 the relationship between li ca ratios and both temperature and co3 2 is less significant with 10 increase in li ca ratio c and 10 mol kg 1 we show how a multi proxy approach could be used to constrain past high latitude surface

isotopic composition and morphology of living globorotalia scitula a new proxy of sub intermediate ocean carbonate chemistry abundance isotopic composition and morphological imprints of the planktonic foraminifera globorotalia scitula brady were closely examined for possible use as a novel reconstruction tool of chemical environments in sub intermediate depth seawater in the past based on the mocnes plankton tow observation of dwelling depths of g scitula and the isotopic compositions together with hydrochemistry data the empirical relations between isotopic disequilibria in carbon 13c 13cg scitula 13cdic and oxygen 18o 18og scitula 18ow isotopes in the carbonate tests and the seawater 18o and 13c of dissolved inorganic carbon dic respectively are introduced the morphological information such as pore density and porosity is also examined for significant relations to carbonate chemistry shell porosity is strongly correlated saturation state of calcite the dissolution of living g scitula tests may promote the observed isotopic differences as well as the increases in porosity 18o of g scitula is found effectively to be linear function of both water temperature and calcite saturation state and thereby temperature equation for g scitula is provided while 13c of g scitula is a linear function of only calcite saturation state the equation was validated by using globorotalia scitula collected by a sediment trap in intermediate water depths satisfactory agreements were found between observed and calculated 18o from the empirical equations based on temperature and hydrochemistry data at sediment trap deployment site indicating that the equation may be useful in paleo environmental reconstruction of sub intermediate water the sediment trap observation further suggests that the abundance of g scitula does not necessarily correspond to surface water productivity and to poc flux but instead it correlates well with the supply of fine organic matter which appears to be a result of water convection thus g scitula may be an unambiguous and excellent paleo environmental recorder for carbonate chemistry and for fine organic matter transport to the depths if isotopic and morphological observations are combined