seasonal changes in planktonic foraminifera in the northwestern north pacific ocean sediment trap experiments from subarctic and subtropical gyres abstract upper ocean environments such as seawater temperature salinity thermal structure in the water column light intensity and food supply affect the assemblage of planktonic foraminifera since detailed information on planktonic foraminifera was not available for the northwestern north pacific we examined seasonal changes in fluxes and composition of planktonic foraminifera there data were collected by sediment traps deployed at three sites site 50n 50 01 n 165 02 e site knot 43 58 n 155 03 e and site 40n 39 60 n 165 00 e in this area in order to better understand the relationship between the foraminiferal assemblage and surface ocean environments although each planktonic foraminiferal species showed specific seasonal variations in flux some exhibited similar flux profiles in order to define these more accurately correlations among species were calculated and the foraminiferal species classified into four groups 1 group a subpolar species neogloboquadrina pachyderma globigerina quinqueloba globigerina bulloides and globigerinita glutinata 2 group b subtropical and tropical species globigerinoides ruber and globigerinoides sacculifer 3 group c post upwelling species neogloboquadrina dutertrei and 4 group d deep water species globorotalia scitula and globorotalia truncatulinoides the common environments for each period based on foraminiferal production and composition were observed among the three sites based upon predominant foraminiferal groups total foraminiferal fluxes tffs organic matter om fluxes and hydrographic conditions including sea surface temperatures sst and thermal structure the surface ocean environments in the northwestern north pacific could be generalized into five types type i is characterized by a dominance of group b with low tffs under high sst and type ii is marked by a high flux of group a on the other hand type iii shows low tffs and low om fluxes due to low insolation during winter type iv represents a high flux of group a and group d at site 40n under a well mixed surface ocean and type v is characterized by a prominent peak of group c under a developed thermocline a comparison of annual mean foraminifera fluxes at 50 n between the northwestern site 50n and the northeastern north pacific station papa during the normal cold mode demonstrated higher fluxes of foraminifera at site 50n due to higher nutrient concentrations the results also showed that g bulloides is not always a proxy for upwelling and that n pachyderma is not solely controlled by seawater temperature in the northwestern pacific where the surface water is enriched in nutrients the fluxes and composition of foraminifera suggest that similar ocean environments are expected in large areas of the northern north pacific from site knot to station papa during the warm mode which is affected by el nino events

natural cause for mercury pollution at clear lake california and paleotectonic inferences mercury measurements in lake sediments from cores from clear lake california reveal that high hg levels up to 65 ppm have been characteristic for the sediments for over 10 ka a strong hg anomaly occurs in sediments deposited between 10 5 and 8 5 ka which we relate to a period of relatively rapid tectonic subsidence of part of clear lake we hypothesize that mercury rich geothermal fluids rose along the activated fractures and faults and were discharged into the lake causing the anomalously high hg content of the sediments and leading to deposition of the sulphur bank hg deposit the total amount of hg discharged into clear lake over the past 15 ka is estimated to be at least 2400 metric tons chemostratigraphy of lake sediments in geothermally active areas may hold promise for the detection and dating of major paleoseismic periods

characterization of late glacial continental dust in the greenland ice core project ice core twelve glacial dust samples extracted from the greenland ice core project ice core have been characterized in terms of mineralogy sr and nd isotopic composition and rare earth element concentrations the ice samples are taken from the younger dryas the bolling the last glacial maximum and both cold and mild glacial periods back to 44 kyr b p a comparison with samples from possible dust source areas determines eastern asia as being the main source area at all times hereby confirming and extending earlier results biscaye et al 1997 this finding is partly in agreement with recent atmospheric general circulation model simulations of glacial atmospheric dust transport andersen et al 1998 mahowald et al 1999 a low intersample variability in tracer characteristics is discussed in the context of a volcanogenic influence grain size dependence and variability in the conti nental dust source areas the clay mineralogy of the ice core dust shows a weak climatic de pendence while the isotopic composition of sr and nd does not correlate with climate this is interpreted as a geographical variation of source areas on a regional scale within asia two ice dust samples were size fractionated at 2 gm and the grain size dependence on tracer characteristics is in accordance with the literature

palaeoclimatological and chronological implications of the vostok core dust record the2 083 m vostok ice core recovered by the soviet antarctic expeditions has provided much information of climatic and environmental interest for a period covering a full glacial inter glacial cycle1 6 here we present and discuss the dust record obtained down to 2 202 m the final depth to which this core was extended in 1986 first we document the fact that major changes in aeolian deposits as recorded in the vostok core appear to be of global significance and confirm the existence of a link between high latitude aeolian deposits and the earth s orbital parameters7 8 second we propose atmospheric dust as a strati graphic marker to compare timing with other records of palaeocli mate and use the magnetic susceptibility profile measured along the rc11 120 indian ocean core9 for this purpose assuming that major dust events correspond to common aeolian inputs this approach indicates that the vostok and marine records were roughly in phase at the previous glacial interglacial transition

comparing dust flux records from the subarctic north pacific and greenland implications for atmospheric transport to greenland and for the application of dust as a chronostratigraphic tool we present a new record of eolian dust flux to the western subarctic north pacific snp covering the past 27 000 years based on a core from the detroit seamount comparing the snp dust record to the north greenland ice core project ngrip ice core record shows significant differences in the amplitude of dust changes to the two regions during the last deglaciation while the timing of abrupt changes is synchronous if dust deposition in the snp faithfully records its mobilization in east asian source regions then the difference in the relative amplitude must reflect climate related changes in atmospheric dust transport to greenland based on the synchronicity in the timing of dust changes in the snp and greenland we tie abrupt deglacial transitions in the 230th normalized 4he flux record to corresponding transitions in the well dated ngrip dust flux record to provide a new chronostratigraphic technique for marine sediments from the snp results from this technique are complemented by radiocarbon dating which allows us to independently constrain radiocarbon paleoreservoir ages we find paleoreservoir ages of 745 140 years at 11 653 year b p 680 228 years at 14 630 year b p and 790 498 years at 23 290 year b p our reconstructed paleoreservoir ages are consistent with modern surface water reservoir ages in the western snp good temporal synchronicity between eolian dust records from the subantarctic atlantic and equatorial pacific and the ice core record from antarctica supports the reliability of the proposed dust tuning method to be used more widely in other global ocean regions

fresh pumice from the central indian basin a krakatau 1883 signature the occurrence of pumice in the central indian basin cib has been a controversy some are of the opinion that these pumices are erupted from a volcano along the ninetyeast ridge while others suggest the indonesian arc volcanism as their probable source recently it is also suggested that the pumice are the products of in situ silicic volcanism in the cib this study was initiated in order to resolve this controversy about the origin of the fresh pumice from the cib the fresh pumice pieces of different sizes and shapes were collected from the surficial sediments of the cib from an average depth of about 5000 m 12 s 76 e glass is the main phase comprising about 95 volume and resembles the matrix glass in krakatau 1883 dacitic pumice which is also very poor 5 in the modal mineral composition the mineral and glass analyses were carried out with the help of the electron microprobe the orthopyroxenes clinopyroxenes plagioclases and spinels are the mineral phases present in these pumices the pyroxenes have similar wo en and fs components to those previously reported from the 1883 krakatau eruption products geochemically these fresh pumices have a high sio2 content 71 and high total alkali content 8 similar to 1883 eruption products of krakatau thus based on the similarities in mineralogy and glass chemical composition it is inferred that these fresh pumices are the products of the fierce 1883 eruption of the krakatau volcano in the sunda strait of the indonesian arc

a 15 000 year paleoenvironmental record from meiji seamount far northwestern pacific late glacial and holocene hemipelagic sediments from meiji seamount in the far northwest pacific contain common to abundant planktonic and benthic foraminifera for ams 14c dating for stable isotope analysis and for interpreting paleoclimate change we present here chronostratigraphic faunal and geochemical results from a piston core which indicate that during glacial times as young as 14 000 yrs bp the northwest pacific sea surface salinity was at least as low as today effectively inhibiting convective overturn between 12 000 and 13 000 yrs ago after a major flux of ice rafting there is faunal and 18o evidence of an abrupt decrease in surface ocean salinity coincident with this event was an increase in biological productivity shown by higher fluxes of calcium carbonate organic carbon opal and greater abundances and lower 13o of the benthic foraminifera uvigerina oxygen isotope ratios in uvigerina and cibicidoides show step like decreases at about 13 000 14 000 11 000 10 000 and 6000 8000 yrs bp these events may be analogous to steps in the north atlantic 18o record during meltwater events if this interpretation is correct then the temperature and salinity history of the deep pacific lags that of the north atlantic by about 1000 yrs consistent with the transport time of deep water from the north atlantic to the north pacific

quantitative resolution of eolian continental crustal material and volcanic detritus in north pacific surface sediment proxy records of continental climate and atmospheric circulation provided by analyses of eolian continental material extracted from marine sediment have resulted in significant new information concerning the behavior of these climate systems on various timescales these studies however currently are limited to certain geographic areas because no chemical or physical extraction procedure provides an unambiguous separation of eolian continental crustal material from other contaminants like volcanic detritus we employ a combined analytical and statistical procedure in an effort to extract a more refined eolian signal from areas that may be affected by volcanic detritus bulk surface sediment samples from 33 locations in the north pacific were treated using a conventional sequential extraction procedure to remove the carbonate silica and oxyhydroxide components and the residue was analyzed by instrumental neutron activation analysis inaa for la ce sm eu yb lu hf sc and th q mode factor analysis of these data shows that 99 of the variance is explained by two end members which we interpret to be continental crustal material and volcanic detritus five least squares normative analysis models were evaluated to estimate the relative amount of these end members in each sample the continental crustal component was approximated using a fine grained fraction of china loess and bulk loess the volcanic component was approximated using the compositions of average kurile kamchatka volcanic material a median ocean drilling program odp leg 145 ash and a median kurile basalt the model based on average kurile kamchatka volcanic material and the fine loess fraction gives the most accurate results central and east pacific samples typically contain up to 100 of the eolian continental crustal component while samples near japan kamchatka and the aleutians contain a majority of volcanic detritus however the highly variable composition of volcanic material can result in systematic errors up to 25 in samples dominated by volcanic detritus the geographic distribution of the compositional end members is consistent with a continental dust source originating in asia and being diluted by ash from the volcanic arcs of the pacific rim this improved identification and resolution of the eolian continental component realized in this approach should permit paleoclimatic reconstructions to be developed from sediments in significant portions of the world that were previously precluded from analysis because of limitations with chemical or physical extraction procedures

petrologic evolution of krakatau indonesia implications for a future activity abstract krakatau volcano is located along a n35e volcanic lineament running through the sunda straits indonesia its last activity has been characterized by successive phases each beginning with the construction of a cone and ending with its destruction and the formation of a caldera the two last pre and post 1883 cycles are well known but the more ancient ones are not so clearly defined lavas of krakatau belong to an andesitic series in which fractional crystallization plays the most important role the petrologic evolution is characterized by a cyclicity in good agreement with the structural evolution the succession is regular basalts basic andesites acid andesites dacites a gap between acid and basic andesites occurs in each cycle the destructive stages correspond to the occurrence of dacitic terms the anak cycle was characterized from 1927 to 1979 by basalts and basic andesites the 1981 eruption involved a more differentiated magma close to dacitic detailed study of the petrologic evolution since 1883 emphasizes the predominant role of fractional crystallization this process occurred during a very short period between 1979 and 1981 separation of labradorite augite olivine and magnetite from parental basic andesite may generate the dacitic descendant in a shallow reservoir p h 2 o estimated about 0 5 kbar implications for a future activity are considered

sunda strait and central sumatra fault sunda strait marks the limit between java trench frontal subduction and sumatra trench oblique subduction the right lateral central sumatra fault accommodates the oblique subduction it does not pass sunda strait but ends between sumatra and java in a complex pattern of dominantly normal faults associated with subsidence seismicity and volcanism we examine the implications of this phenomenon in sunda strait and in the adjacent fore arc basin and accretionary prism which underwent north south compression due to subduction as well as east west extension we propose that the strait is a consequence of the northwestward motion of the southwestern sumatra block along the central sumatra fault we also propose that the extensional zone in the sunda strait widens considerably to the southwest toward the trench and changes into a composite zone of deformation affected by strike slip as well as normal faulting

the december 22 2018 anak krakatau indonesia landslide and tsunami preliminary modeling results on the evening of december 22 2018 the coasts of the sunda strait indonesia were hit by a tsunami generated by the collapse of a part of the anak krakatau volcano hundreds of people were killed thousands were injured and displaced this paper presents a preliminary modeling of the volcano flank collapse and the tsunami generated based on the results of a 2d depth averaged coupled model involving a granular rheology and a coulomb friction for the slide description and dispersive effects for the water flow part with a reconstructed total volume subaerial and submarine of the landslide of 150 million hbox m 3 inferred from pre and post collapse satellite and aerial images the comparison of the simulated water waves with the observations tide gauges located all around the strait photographs and field surveys is satisfactory due to the lack of information for the submarine part of the landslide the reconstructed submarine slope is assumed to be approximately constant a significant time delay on the results and particularly in the bandar lampung bay could be attributed to imprecisions of bathymetric data the sensitivity to the basal friction and to dispersive effects is analyzed through numerical tests results show that the influence of the basal friction angle on the simulated wave heights decreases with distance and that a value of 2 circ gives consistent results with the observations the dispersive effects are assessed by comparing water waves simulated by a shallow water model and a boussinesq model simulations with frequency dispersion produce longer wave periods and smaller wave amplitudes in the sunda strait and particularly in deep waters

ice core evidence for a very tight link between north atlantic and east asian glacial climate 1 corresponding millennial scale climate changes have been reported from the north atlantic region and from east asia for the last glacial period on independent timescales only to assess their degree of synchrony we suggest interpreting greenland ice core dust parameters as proxies for the east asian monsoon systems this allows comparing north atlantic and east asian climate on the same timescale in high resolution ice core data without relative dating uncertainties we find that during dansgaard oeschger events north atlantic region temperature and east asian storminess were tightly coupled and changed synchronously within 5 10 years with no systematic lead or lag thus providing instantaneous climatic feedback the tight link between north atlantic and east asian glacial climate could have amplified changes in the northern polar cell to larger scales we further find evidence for an early onset of a younger dryas like event in continental asia which gives

petrology and geochemistry of the lamongan volcanic field east java indonesia primitive sunda arc magmas in an extensional tectonic setting new geochemical data are presented from prehistoric and historical multifarious process involving possible inputs from the subducted oceanic lithosphere subducted oceanic sedieruptive products of the lamongan volcanic field lvf east java a region of the sunda arc covering 260 km and containing ments and fluids the asthenospheric and lithospheric portions of the mantle wedge above the subduction zone 90 eruptive vents plus the historically active lamongan volcano lvf lavas include medium k basalts and basaltic andesites from and the arc crust e g tatsumi eggins 1995 following melt generation processes such as crystal fractionation historical eruptions of lamongan and prehistoric eruptions in the eastern lvf along with a high k suite represented by prehistoric accumulation and crustal assimilation during transit to the surface may obscure the true nature of the magma deposits in the western lvf although lacking some of the characteristics of truly primary basalts the least evolved lavas identified source region the effects of these processes on the compositions of erupted lavas must therefore be removed in the lvf have some of the lowest sio2 contents 43 wt sio2 yet reported in sunda arc volcanic rocks mass balance before models of arc magma genesis can be tested for this reason it is desirable to sample magmas that considerations indicate that two chemically distinct lvf magmas may be parental to suites currently being erupted from the neighbouring have suffered minimal modification since segregation from their source region the compositions of the primary volcanoes semeru and bromo lamongan s historical lavas can be related to the medium k andesitic products of semeru by fractional or primitive magmas from different arcs provide a window on the diverse mechanisms of and the components crystallization despite the former s location at the same distance from the trench as bromo a high k volcano extensional tectonics involved in melt production at convergent margins and as such are essential to our understanding of the possibly related to arc segmentation in the region of the lvf creating subduction zone environment conditions that promote the rapid ascent of parental magmas is many studies have highlighted the correlation between probably responsible for this and several other features of the complex extensional tectonics in volcanic arcs and the eruption of lavas with primitive chemical characteristics e g luhr carmichael 1981 knittel oles 1995 bacon et al

glacial interglacial co2 change the iron hypothesis several explanations for the 200 to 280 ppm glacial interglacial change in atmospheric co2 concentrations deal with variations in southern ocean phytoplankton productivity and the related use or nonuse of major plant nutrients an hypothesis is presented herein in which arguments are made that new productivity in today s southern ocean 7 4 1013g yr 1 is limited by iron deficiency and hence the phytoplankton are unable to take advantage of the excess surface nitrate phosphate that if used could result in total southern ocean new production of 2 3 1015 g c yr 1 as a consequence of fe limited new productivity holocene interglacial co2 levels preindustrial are as high as they were during the last interglacial 280 ppm in contrast atmospheric dust fe supplies were 50 times higher during the last glacial maximum lgm because of this fe enrichment phytoplankton growth may have been greatly enhanced larger amounts of upwelled nutrients may have been used and the resulting stimulation of new productivity may have contributed to the lgm drawdown of atmospheric co2 to levels of less than 200 ppm background information and arguments in support of this hypothesis are presented

sea surface temperature variability and sea ice extent in the subarctic northwest pacific during the past 15 000 years past changes in north pacific sea surface temperatures and sea ice conditions are proposed to play a crucial role in deglacial climate development and ocean circulation but are less well known than from the north atlantic here we present new alkenone based sea surface temperature records from the subarctic northwest pacific and its marginal seas bering sea and sea of okhotsk for the time interval of the last 15 kyr indicating millennial scale sea surface temperature fluctuations similar to short term deglacial climate oscillations known from greenland ice core records past changes in sea ice distribution are derived from relative percentage of specific diatom groups and qualitative assessment of the ip25 biomarker related to sea ice diatoms the deglacial variability in sea ice extent matches the sea surface temperature fluctuations these fluctuations suggest a linkage to deglacial variations in atlantic meridional overturning circulation and a close atmospheric coupling between the north pacific and north atlantic during the holocene the subarctic north pacific is marked by complex sea surface temperature trends which do not support the hypothesis of a holocene seesaw in temperature development between the north atlantic and the north pacific key points millennial scale changes in sst in the north pacific during the last 15 kyr changes in sea ice extent suggest a close coupling to sst fluctuations middle to late holocene ssts show no clear sst trend in the north pacific

paleomagnetic evidence for high temperature emplacement of the 1883 subaqueous pyroclastic flows from krakatau volcano indonesia the paroxysmal 1883 eruption of krakatau volcano in indonesia discharged at least 6 5 km3 dense rock equivalent of pyroclastic material into the shallow waters of the sunda straits within a 15 km radius of the volcano progressive thermal demagnetization studies of individually oriented pumice clasts from a core sample of the submarine pyroclastic deposits show that 41 out of 47 clasts exhibit single component remanence with mean inclination of 2 4 the partial thermoremanent magnetization components of both pumice and lithic clasts are well grouped in orientation indicating that substantial cooling of clasts must have occurred following deposition estimated subaqueous emplacement temperature for such clasts is greater than 500 c rare two component lithic fragments exhibit inflection points on vector endpoint diagrams that mark the temperature below which the fragments acquired magnetization of similar orientation these inflection points range from 350 to 550 c indicating a minimum subaqueous emplacement temperature of 350 c paleomagnetic evidence for high emplacement temperature supports the hypothesis that proximal 1883 submarine pyroclastic deposits resulted from entrance of hot subaerially generated pyroclastic flows into the sea similar deposits have been interpreted from the geologic record but this is the first documented example of submarine pyroclastic flows from a historic eruption the krakatau deposits thus serve as an important modern analog for the study of pyroclastic flow seawater interactions

230th normalization an essential tool for interpreting sedimentary fluxes during the late quaternary there is increasing evidence indicating that syndepositional redistribution of sediment on the seafloor by bottom currents is common and can significantly affect sediment mass accumulation rates notwithstanding its common incidence this process generally referred to as sediment focusing is often difficult to recognize if redistribution is near synchronous to deposition the stratigraphy of the sediment is not disturbed and sediment focusing can easily be overlooked ignoring it however can lead to serious misinterpretations of sedimentary fluxes particularly when past changes in export flux from the overlying water are inferred in many instances this problem can be resolved at least for sediments deposited during the late quaternary by normalizing to the flux of 230th scavenged from seawater which is nearly constant and equivalent to the known rate of production of 230th from the decay of dissolved 234u we review the principle advantages and limitations of this method notwithstanding its limitations it is clear that 230th normalization does provide a means of achieving more accurate interpretations of sedimentary fluxes and eliminates the risk of serious misinterpretations of sediment mass accumulation rates

seismicity of the sunda strait evidence for crustal extension and volcanological implications the sunda strait is located in the transitional zone between two different modes of subduction the java frontal subduction and the sumatra oblique subduction this setting implies that the sunda strait region is a key to the understanding of the geodynamic processes involved in order to study the shallow seismicity a microearthquake survey was carried out in that region twelve stations accurately located by the aim of satellite positionning recorded about 300 local events in the summer 1984 from this set 174 shallow earthquakes have been precisely located the results of this study reveal that the crustal earthquakes in the sunda strait area occurs in three main areas 1 beneath the krakatau complex where earthquakes are generated by double couples and are of tectonic origin 2 inside a graben in the western part of the strait and 3 in a more diffused zone to the south of sumatra the individual and composite focal mechanisms from the events inside the strait show an extensional regime a stress tensor which have been deduced from the individual focal mechanisms of earthquakes of the krakatau group shows that the tensional axis is oriented n130oe this study confirms that the sunda strait is in an extensional tectonic regime as a result of the northwestward movement of the sumatra sliver plate along the semangko fault zone

the origin of ferro manganese oxide coated pumice from the central indian ocean basin pumice clasts partially and fully coated with ferro manganese oxide from the central indian ocean basin ciob were analysed for major trace and rare earth elements and glass and mineral grain chemistry to assess their possible source these pumice clasts have 95 glassy matrix with 5 of plagioclase ortho pyroxene amphibole and spinel mineral grains pumice is rhyolitic with high content of silica and total alkalis and show strong light rare earth element enrichment with la 100 times enriched compared to chondritic abundance and exhibits a pronounced negative eu anomaly both the partially and fully coated pumice clasts have a similar composition but this and their glass and mineral orthopyroxene chemistry differs from all tuffs known to have erupted from the toba caldera complex the partial to complete fe mn oxide coating suggests the pumice probably predates activity from the toba caldera their general composition is consistent with a volcanic arc origin and show similarities to rhyolitic eruptives from sumatra the distribution of partially and fully coated pumice in the ciob overlaps with that of uncoated pumice from the voluminous ytt eruption suggesting that other large rhyolitic calderas active in sumatra indonesia similarities in composition to ash layers from the ciob suggest a possible late miocene late pleistocene age for these pumices

crustal differentiation processes at krakatau volcano indonesia anak krakatau is a basaltic andesite cone that has grown following the famous caldera forming 1883 eruption of krakatau it breached sea level in 1927 and since the 1950s has been growing at an average rate of similar to 8 cm a week we present new major and trace element data combined with whole rock delta o 18 sr and nd isotope data for 1883 1993 and 2002 krakatau eruptive products and the surrounding crust bombs erupted from anak krakatau during 2002 contain frothy metasedimentary and plutonic xenoliths that show variable degrees of thermal metamorphism plastic deformation and partial melting contact metamorphic minerals such as cordierite and tridymite in metasedimentary xenoliths are consistent with high temperature metamorphism and incorporation at mid to upper crustal depth energy constrained assimilation and fractional crystallization modelling of whole rock data suggests that the anak krakatau magmas have a genetic relationship with the 1883 eruption products the geochemical impact of crustal contaminants on whole rock compositions is apparently small and we conclude that low levels of assimilation of a quartzo feldspathic sediment are recorded in anak krakatau magmas plagioclase phenocrysts from the 2002 eruption exhibit disequilibrium textures and complex compositional zoning however and are also isotopically variable with a total range in sr 87 sr 86 of 0 center dot 7043 0 center dot 7048 as determined by in situ laser ablation inductively coupled plasma mass spectrometry this suggests that although shallow crustal assimilation appears to have had a limited effect on whole rock chemistry a complex late stage differentiation history is recorded within the magma s cargo of crystals and xenoliths

reconstructing the anak krakatau flank collapse that caused the december 2018 indonesian tsunami volcanogenic tsunamis are one of the deadliest volcanic phenomena understanding their triggering processes and mitigating their effect remains a major challenge on 22 december 2018 flank failure of the anak krakatau volcano in indonesia generated a tsunami which killed more than 400 people this event was captured in unprecedented detail by high resolution satellite imagery and eyewitness accounts here we combine historic observations with these recent data to for the first time interpret the internal architecture of anak krakatau and reconstruct the failure tsunamigenesis and regrowth processes observed we calculate the volume of material initially lost from the volcano flank failure and find that it was relatively small 0 1 km3 compared to the overall changes observed during the entire eruption but was nonetheless able to generate rapid tsunami waves with devastating impacts the flank failure also changed the eruption style and upper volcanic plumbing system with these subsequent explosive eruptions destroying the summit and then partially rebuilding the lost flank the nature of the flank failure was controlled by the internal structure of the island and although regrowth rate will be a primary control on flank failure intervals the reconfiguring of the volcano s internal vent network is likely to have re stabilised it in the medium term the findings demonstrate that hazard assessments at ocean islands must consider that even small flank failures during unexceptional eruptions can have catastrophic consequences

mercury as a proxy for volcanic activity during extreme environmental turnover the cretaceous paleogene transition abstract the usually low geological background concentrations of hg makes this trace element suitable for identifying accumulation pulses in sediments that can be tentatively related to weathering processes and thus to climatic changes intense volcanism has witnessed the cretaceous paleogene transition ktb and was perhaps responsible for dramatic climatic changes and decrease in biodiversity and mass extinction we have used hg concentrations as a proxy for volcanic activity and atmospheric hg and co2 buildup across the ktb at three localities in the salta basin argentina hg contents display several spikes across the ktb with a maximum value of 250 ng g 1 in three drill cores across the ktb in the paraiba basin northeastern brazil hg contents increase from the late maastrichtian to early danian and hg spikes predate the ktb perhaps as a record of volcanic activity before but very close to this transition at stevns klint denmark hg contents reached almost 250 ng g 1 within a 5 cm thick clay layer the fiskeler member fish clay that comprises the ktb some co variation between hg and al2o3 contents has been observed in all of the studied sections across the ktb suggesting that hg is probably adsorbed onto clays thermo desorption experiments in selected samples from the yacoraite formation showed hg 2 as the major species present which is in agreement with a volcanic origin combined hg and c isotope chemostratigraphy may become a powerful tool for the eventual assessment of the role of volcanic activity during extreme climatic and biotic events such as those during the ktb

oxygen isotope and palaeotemperature records from six greenland ice core stations camp century dye 3 grip gisp2 renland and northgrip oxygen isotope variations spanning the last glacial cycle and the holocene derived from ice core records for six sites in greenland camp century dye 3 grip gisp2 renland and northgrip show strong similarities this suggests that the dominant influence on oxygen isotope variations reflected in the ice sheet records was regional climatic change differences in detail between the records probably reflect the effects of basal deformation in the ice as well as geographical gradients in atmospheric isotope ratios palaeotemperature estimates have been obtained from the records using three approaches i inferences based on the measured relationship between mean annual 18o of snow and of mean annual surface temperature over greenland ii modelled inversion of the borehole temperature profile constrained either by the dated isotopic profile or iii by using monte carlo simulation techniques the third of these approaches was adopted to reconstruct holocene temperature variations for the dye 3 and grip temperature profiles which yields remarkably compatible results a new record of holocene isotope variations obtained from the northgrip ice core matches the grip short term isotope record and also shows similar long term trends to the dye 3 and grip inverted temperature data the northgrip isotope record reflects i a generally stronger isotopic signal than is found in the grip record ii several short lived temperature fluctuations during the first 1500 yr of the holocene iii a marked cold event at ca 8 2 ka the 8 2 ka event iv optimum temperatures for the holocene between ca 8 6 and 4 3 ka a signal that is 0 6 stronger than for the grip profile v a clear signal for the little ice age and vi a clear signal of climate warming during the last century these data suggest that the northgrip stable isotope record responded in a sensitive manner to temperature fluctuations during the holocene copyright 2001 john wiley sons ltd

the intercept is a poor estimate of a calibrated radiocarbon age intercept based methods of generating a point estimate of a calibrated radiocarbon date are very popular but exhibit undesirable behaviour they are highly sensitive to the mean of the radiocarbon date and to adjustments of the calibration curve other methods give more stable results the weighted average of the probability distribution function is recommended as the best central point estimate but more consideration should be given to using the full probability distribution rather than a point estimate in developing age depth models

petrology and geochemistry of ordovician k bentonites in new york state constraints on the nature of a volcanic arc altered volcanic ashes k bentonites in the late ordovician caradocian utica shale of new york state are the product of explosive arc volcanism most of the 30 k bentonites examined in this investigation contain fragmental crystals and rock fragments microliths up to 600 mu m in diameter that generally are neither detrital contamination from the surrounding black shale nor igneous phenocrysts the dominant phases are garnet two groups gr sub 15 20 alm sub 45 75 py sub 35 0 sp sub 2 5 gr sub 2 5 alm sub 55 85 py sub 10 40 sp sub 1 plagioclase feldspar an sub 80 10 alkali feldspar or sub 99 0 clinopyroxene wo sub 50 40 en sub 50 30 fs sub 0 30 and orthopyroxene wo sub 1 2 en sub 77 32 fs sub 32 66 accompanied by lesser quantities of hornblende aluminosilicate quartz sphene fe ti oxides apatite and zircon most of the fragmental crystals appear to be derived from the same source as the metamorphic microliths which possess minerals with similar compositions both crystals and microliths are interpreted as xenocrysts and xenoliths from the ancient continental crust on which the ordovician arc was constructed they became entrained in the volcanic plume during explosive eruptions a precambrian age acquired on k feldspars from one k bentonite using the sup 40 ar sub 39 ar method shows that these xenocrysts were derived from depths of less than 5 10 km in the microcontinent at the time of late ordovicianmore volcanism the occurrence of xenocrysts and xenoliths in these k bentonites underscores the importance of performing detailed petrology on ash layers prior to the onset of more sophisticated tasks e g isotopic age determinations regional stratigraphic correlations of k bentonites based upon chemical compositions less

modelling 2018 anak krakatoa flank collapse and tsunami effect of landslide failure mechanism and dynamics on tsunami generation the 2018 anak krakatoa volcano flank collapse generated a tsunami that impacted the sunda strait coastlines in the absence of a tsunami early warning system it caused several hundred fatalities there are ongoing discussions to understand how the failure mechanism of this event affected landslide dynamics and tsunami generation in this paper the sensitivity to different failure scenarios on the tsunami generation is investigated through numerical modelling to this end the rate of mass release the landslide volume the material yield strength and orientation of the landslide failure plane are varied to shed light on the failure mechanism landslide evolution and tsunami generation we model the landslide dynamics using the depth averaged viscoplastic flow model bingclaw coupled with depth averaged long wave and shallow water type models to simulated tsunami propagation we are able to match fairly well the observed tsunami surface elevation amplitudes and inundation heights in selected area with the numerical simulations however as observed by other authors discrepancies in simulated and observed arrival times for some of the offshore gauges are found which raises questions related to the accuracy of the available bathymetry for this purpose further sensitivity studies changing the bathymetric depth near the source area are carried out with this alteration we are also able to match better the arrival times of the waves

influence of the intertropical convergence zone on the east asian monsoon a palaeoclimate record spanning the past 16 000 years with nearly annual time resolution has been obtained from lake huguang maar in china the magnetic properties and titanium content of the lake sediments are thought to reflect changes in the east asian winter monsoon strength thus providing a complement to palaeoclimate archives that record the strength of the rain bearing summer monsoon the records point to an anti correlation between winter and summer monsoon strength best explained by migration of the intertropical convergence zone itcz a belt of low pressure air at the equator interestingly the decline of china s tang dynasty and the mayan civilization broadly coincide with drought periods recorded in lake huguang maar and cariaco basin sediments respectively did major shifts in the position of the itcz catalyse simultaneous events in civilizations on opposite sides of the pacific ocean the asian australian monsoon is an important component of the earth s climate system that influences the societal and economic activity of roughly half the world s population the past strength of the rain bearing east asian summer monsoon can be reconstructed with archives such as cave deposits1 2 3 but the winter monsoon has no such signature in the hydrological cycle and has thus proved difficult to reconstruct here we present high resolution records of the magnetic properties and the titanium content of the sediments of lake huguang maar in coastal southeast china over the past 16 000 years which we use as proxies for the strength of the winter monsoon winds we find evidence for stronger winter monsoon winds before the bolling allerod warming during the younger dryas episode and during the middle and late holocene when cave stalagmites suggest weaker summer monsoons1 2 3 we conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone similar migrations of the intertropical convergence zone have been observed in central america for the period ad 700 to 900 refs 4 6 suggesting global climatic changes at that time from the coincidence in timing we suggest that these migrations in the tropical rain belt could have contributed to the declines of both the tang dynasty in china and the classic maya in central america

kinematics of tertiary deformation in the basement involved fold thrust complex western nordenskiold land svalbard tectonic implications based on fault slip data analysis abstract kinematic analysis based on the interpretation of small scale fault and fold data supports a kinematic evolution history involving heterogeneous crustal shortening and uplift and subsequent extension collapse for the major west coast fold thrust complex in western nordenskiold land svalbard this deformation can be divided into three main kinematic events stage 1 represents an early distinctive nne ssw oriented contractional episode that generated layer parallel and low angle thrusts and internal folds stage 1 structures population 1 are arranged in an apparent en echelon geometry and oblique direction relative to the major nne ssw trending fold thrust complex of stage 2 affinity stage 2 structures include ene verging chevron folds and steeply wsw dipping thrusts and duplexes that evolved during a progressive wsw ene oriented contractional episode initial pre fold stratal shortening stage 2a was followed by a continuous buildup of the fold thrust complex and general crustal thickening syn fold stage 2b until a supercritical height thickness was reached post fold stage 2c at this stage a change in the stress field caused failure of the fold thrust complex and continued ne sw directed shortening was accommodated as vertical strike slip faults population 2c late w e to wsw ene directed extension the stage 3 episode was probably related to collapse of the overthickened stage 2 fold thrust complex the detailed reconstruction of kinematic events in western nordenskiold land supports initial breakup of the greenland svalbard area in early paleocene times during dextral nne ssw directed transpression stage 1 the major deformational episode stage 2 probably of mid paleocene to eocene age was characterized by progressive wsw ene directed shortening and was related to decoupled deformation where broad zones of convergent strain were linked to narrow strike slip zones this strain partitioning is considered to have begun when the hornsund fault zone widened into and reactivated the basin bounding faults of the carboniferous st jonsfjorden trough the latest kinematic episode stage 3 is likely of eocene age and may be ascribed to extensional collapse in the hinterland of the western spitsbergen orogenic wedge within a regional dextral transpressive setting

assessing the collection efficiency of ross sea sediment traps using 230th and 231pa abstract annual fluxes of particulate 230th and 231pa collected by sediment traps deployed at two locations in the ross sea are compared to expected fluxes derived by combining the seasonal depletion of 230th and 231pa in surface waters with the steady state production of each nuclide by radioactive decay of its respective dissolved uranium parent conservative minimum estimates of the expected 230th flux are greater than the flux collected by sediment traps deployed at 200 m by factors of 3 and 6 at the two sites the actual discrepancy may be much larger the discrepancies between expected and measured fluxes of 231pa are slightly smaller but comparable in magnitude to those for 230th the discrepancies between expected and measured fluxes for these natural radionuclides are similar in magnitude to those determined previously using the same sediment traps for particulate organic carbon which suggests that the sediment traps undercollected the actual flux of sinking particles

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

the genesis of silicic arc magmas in shallow crustal cold zones abstract a number of currently popular models for the genesis of evolved arc magmas from basaltic andesite to dacite invoke repeated intrusion partial melting and differentiation at the base of the crust however several observations suggest that this may be the exception rather than the norm 1 geobarometry often indicates shallow pressure 0 1 0 3 gpa evolution 2 incongruent melting of amphibolite at elevated pressures should yield magmas in equilibrium with high pressure phases like garnet but rare earth element patterns almost ubiquiously preclude this 3 compositionally zoned caldera forming eruptions suggest differentiation at near surface depths 4 u series data most commonly indicate differentiation over millennia time scales this requires rapid cooling that in turn is most easily explained by relatively small magma volumes undergoing crystal fractionation within the shallow i e cool crust to further test these ideas we combined published experimental data for liquidus equilibria with appropriate silicic arc magma compositions on projections of the ternary liquidus system nepheline silica olivine recent data for tongan silicic lavas plot either on or close to low pressure 1 atm cotectics for the rocks phenocryst phases suggesting low pressure differentiation using our own and published data from arc volcanoes around the world we find that the majority are consistent with differentiation at shallow depths regardless of total crustal thickness combined with the typical timescales of differentiation we estimate that the volumes of magma stored during differentiation in shallow crustal zones are usually on the order of only a few km 3 there is also a clear role for mixing and recharge that involves magmas that are more deeply sourced and primitive in character typically evolved basalts and basaltic andesites whether the latter differentiated in the lower crust or at the crust mantle boundary has important implications for the constitution and average composition of arc crust at present we can only conclude that evidence for more silicic arc magma generation at these depths is generally lacking

a 35 myr record of helium in pelagic limestones from italy implications for interplanetary dust accretion from the early maastrichtian to the middle eocene we have determined the helium concentration and isotopic composition of a suite of early maastrichtian through middle eocene pelagic limestones in the italian apennines the results provide a 35 myr record of the implied flux of extraterrestrial 3he which is a proxy for the accretion rate of interplanetary dust particles idps our measurements show that the 3he flux was fairly constant in the maastrichtian except for possible minor increases factor of two or less from 70 5 ma to 68 ma and at 66 ma which probably reflect transient increases in the accretion rate of asteroidal and or cometary idps we find no evidence for an increase in idp accretion at or immediately before the k t boundary implying that the k t impact was not associated with enhanced solar system dustiness this observation precludes the possibility that the k t impactor was a member of a major comet shower and is more consistent with impact of a lone comet or asteroid our data suggest a 2 to 4 fold increase in idp accretion between 57 and 54 ma followed by a factor of three decrease over an 4 myr period in the early to middle eocene the duration and magnitude of this variability is inconsistent with previous observations attributed to a shower of long period comets and is more likely the result of collisions in the asteroid belt and or kuiper belt in the entire 35 myr record we find no evidence for major enhancements of the idp accretion rate of the type expected from comet showers our results in combination with earlier 3he measurements do not support models that predict recurrent comet showers with periods of 38 myrs if there is a periodicity in the cratering record that is caused by periodic modulation of the oort cloud it is not evident in the apennine sediment data along with the 3he measurements we also obtained 4he concentrations which record temporal changes in the flux or composition of terrigenous matter the most significant change in 4he occurs in the last 4 myrs of the cretaceous over which the concentration of 4he in the detrital component rises by 300 this rise tracks a strong increase in the seawater 87 sr 86 sr ratio suggesting a globally significant change in the composition of continental detritus delivered to the oceans possibly arising from increased continental weathering

synchronization of north pacific and greenland climates preceded abrupt deglacial warming some proposed mechanisms for transmission of major climate change events between the north pacific and north atlantic predict opposing patterns of variations others suggest synchronization resolving this conflict has implications for regulation of poleward heat transport and global climate change new multidecadal resolution foraminiferal oxygen isotope records from the gulf of alaska goa reveal sudden shifts between intervals of synchroneity and asynchroneity with the north greenland ice core project ngrip 18 o record over the past 18 000 years synchronization of these regions occurred 15 500 to 11 000 years ago just prior to and throughout the most abrupt climate transitions of the last 20 000 years suggesting that dynamic coupling of north pacific and north atlantic climates may lead to critical transitions in earth s climate system

the 1883 eruption of krakatau the 1883 eruption of krakatau was a modest ignimbrite forming event the deposits are primarily coarse grained dacitic non welded ignimbrite large explosions produced pyroclastic flows that entered the sea generating destructive tsunami grain size studies of the ignimbrite suggest that these explosions were not driven by magma seawater interaction the total bulk volume of pyroclastic deposits including co ignimbrite ash is estimated to be 18 21 km3

neodymium isotopic variations in north pacific modern silicate sediment and the insignificance of detrital ree contributions to seawater the neodymium isotopic composition of the silicate fraction of holocene pelagic sediments from the north pacific define two provinces a central north pacific province characterized by unradiogenic and remarkably homogeneous end 10 2 0 5 and a narrow circum pacific marginal province characterized by more radiogenic and variable end 4 2 3 8 the silicate fraction in the central north pacific is exclusively eolian based on prevailing wind patterns meteorological data and neodymium isotopic data the only significant sediment source is chinese loess leaching experiments on chinese loess confirm that leachable nd is isotopically indistinguishable from bulk and residual silicate nd silicates in the circum north pacific marginal province comprise eolian loess volcanic ash and hemipelagic sediments derived from volcanic arcs a compilation of pacific seawater and mn nodule end data shows no clear spatial variation except for a general decrease from surface to deep waters from 3 to 4 and slightly lower end in bottom waters along the western north pacific due to the incursion of antarctic bottom water the relative homogeneity of bottom water end which contrasts sharply with the distinctive variation in sediment end plus the large difference between the average end of bottom waters and the central north pacific eolian silicates 4 vs 10 suggests that any contribution of ree to seawater from eolian materials is insignificant furthermore leaching of ree from eolian particles as they sink though the water column must be insignificant because nd in shallow waters is more radiogenic than nd in deeper waters that there is no contrast in the nd isotopic composition of bottom waters that overlie the central and marginal sediment provinces suggests that the ash and hemipelagic sediments derived from pacific rim volcanic arcs also contribute minimal ree to seawater the elimination of eolian ash and hemipelagic sediments leaves only near shore riverine particulates as a possibly significant particulate source of ree to seawater

coupling eruption and tsunami records the krakatau 1883 case study indonesia the well documented 1883 eruption of krakatau volcano indonesia offers an opportunity to couple the eruption s history with the tsunami record the aim of this paper is not to re analyse the scenario for the 1883 eruption but to demonstrate that the study of tsunami deposits provides information for reconstructing past eruptions indeed though the characteristics of volcanogenic tsunami deposits are similar to those of other tsunami deposits they may include juvenile material e g fresh pumice or be interbedded with distal pyroclastic deposits ash fall surges due to their simultaneity with the eruption five kinds of sedimentary and volcanic facies related to the 1883 events were identified along the coasts of java and sumatra 1 bioclastic tsunami sands and 2 pumiceous tsunami sands deposited respectively before and during the plinian phase 26 27 august 3 rounded pumice lapilli reworked by tsunami 4 pumiceous ash fall deposits and 5 pyroclastic surge deposits only in sumatra the stratigraphic record on the coasts of java and sumatra which agrees particularly well with observations of the 1883 events is tentatively linked to the proximal stratigraphy of the eruption

glacial interglacial variability in the delivery of dust to the central equatorial pacific ocean abstract fluxes of continental mineral aerosols dust were greater during glacial periods than during interglacials throughout most regions of the earth the equatorial pacific ocean was a possible exception to this pattern in that previous studies have reported either greater dust fluxes during interglacials or no consistent glacial interglacial pattern of dust flux we have applied the 230th normalization technique to derive five new records of dust flux from central equatorial pacific ocean sediments in contrast to previous studies which relied on stratigraphic accumulation rates the 230th normalization technique produces internally consistent results revealing fluxes to this region of continental lithogenic material that were positively correlated with global ice volume throughout the past 300 000 yr maximum glacial fluxes of continental mineral aerosols exceed minimum interglacial fluxes by about a factor of 2 similar to changes found elsewhere at low and mid latitudes this amplitude of variability is substantially smaller than that seen in some recent models and these observations provide a calibration point for future model development

detection of magma bodies beneath krakatau volcano indonesia from anomalous shear waves abstract the seismograms of 14 local earthquakes recorded by a temporary network in the sunda strait were used to construct an image of shear wave attenuating bodies in the vicinity of the krakatau volcanic complex seismograms for all ray paths going beneath the krakatau complex show a diminution of the amplitude of s waves these diminutions cannot be attributed to source mechanisms or station effects combination of all ray paths although in limited number demonstrates that the attenuating body is located in two zones which are probably disconnected although the limited set of data available does not allow us to draw a definite conclusion the upper zone is about 9 km deep and the lower one is at least 22 km deep the upper zone contains probably numerous irregular pockets of magma the deep zone appears to be a very wide body related to the extensional nature of the sunda strait the existence of a large deep reservoir should be taken into account for the mitigation of future hazards

glacial interglacial changes in mineral dust and sea salt records in polar ice cores sources transport and deposition 1 sea salt and mineral dust records as represented by na and ca2 concentrations respectively in greenland and antarctic ice cores show pronounced glacial interglacial variations for the last glacial maximum lgm mineral dust sea salt concentrations in greenland show an increase of a factor of approximately 80 15 compared to the holocene and significant shifts by a factor of 15 5 during dansgaard oeschger events in antarctica the dust sea salt flux is enhanced by a factor of 15 3 during the lgm compared to the holocene and variations by approximately a factor of 8 1 2 exist in parallel to antarctic warm events primary glacial dust sources are the asian deserts for greenland and patagonia for antarctica ice core evidence and model results show that both changes in source strength as well as atmospheric transport and lifetime contributed to the observed changes in greenland ice cores in antarctica changes in ice core fluxes are in large parts related to source variations both for sea salt and dust where the formation of sea salt aerosol from sea ice may play a pivotal role summarizing our latest estimates on changes in sources transport and deposition these processes are roughly able to explain the glacial increase in sea salt in both polar regions while they fall short by at least a factor of 4 7 for mineral dust future improvements in model resolution and in the formulation of source and transport processes together with new ice core records e g on dust size distributions will eventually allow convergence of models and observations

subarctic pacific evidence for a glacial deepening of the oceanic respired carbon pool abstract measurements of benthic foraminiferal cadmium calcium cd ca have indicated that the glacial interglacial change in deep north pacific phosphate po4 concentration was minimal which has been taken by some workers as a sign that the biological pump did not store more carbon in the deep glacial ocean here we present sedimentary redox sensitive trace metal records from ocean drilling program odp site 882 nw subarctic pacific water depth 3244 m to make inferences about changes in deep north pacific oxygenation and thus respired carbon storage over the past 150 000 yr these observations are complemented with biogenic barium and opal measurements as indicators for past organic carbon export to separate the influences of deep water oxygen concentration and sedimentary organic carbon respiration on the redox state of the sediment our results suggest that the deep subarctic pacific water mass was depleted in oxygen during glacial maxima though it was not anoxic we reconcile our results with the existing benthic foraminiferal cd ca by invoking a decrease in the fraction of the deep ocean nutrient inventory that was preformed rather than remineralized this change would have corresponded to an increase in the deep pacific storage of respired carbon which would have lowered atmospheric carbon dioxide co2 by sequestering co2 away from the atmosphere and by increasing ocean alkalinity through a transient dissolution event in the deep sea the magnitude of change in preformed nutrients suggested by the north pacific data would have accounted for a majority of the observed decrease in glacial atmospheric pco2

glacial interglacial changes in nutrient supply and stratification in the western subarctic north pacific since the penultimate glacial maximum abstract in piston cores from the open subarctic pacific and the okhotsk sea diatom bound 15n 15ndb biogenic opal calcium carbonate and barium were measured from coretop to the previous glacial maximum mis 6 glacial intervals are generally characterized by high 15ndb 8 and low productivity whereas interglacial intervals have a lower 15ndb 5 7 6 3 and indicate high biogenic productivity these data extend the regional swath of evidence for nearly complete surface nutrient utilization during glacial maxima consistent with stronger upper water column stratification throughout the subarctic region during colder intervals an early deglacial decline in 15ndb of 2 at 17 5 ka previously observed in the bering sea is found here in the open subarctic pacific record and arguably also in the okhotsk and a case can be made that a similar decrease in 15ndb occurred in both regions at the previous deglaciation as well the early deglacial 15ndb decrease best explained by a decrease in surface nutrient utilization appears synchronous with southern hemisphere associated deglacial changes and with the heinrich 1 event in the north atlantic this 15ndb decrease may signal the initial deglacial weakening in subarctic north pacific stratification and or a deglacial increase in shallow subsurface nitrate concentration if the former it would be the north pacific analogue to the increase in vertical exchange inferred for the southern ocean at the time of heinrich event 1 in either case the lack of any clear change in paleoproductivity proxies during this interval would seem to require an early deglacial decrease in the iron to nitrate ratio of subsurface nutrient supply or the predominance of light limitation of phytoplankton growth during the deglaciation prior to bolling allerod warming

a complete terrestrial radiocarbon record for 11 2 to 52 8 kyr b p radiocarbon 14c provides a way to date material that contains carbon with an age up to 50 000 years and is also an important tracer of the global carbon cycle however the lack of a comprehensive record reflecting atmospheric 14c prior to 12 5 thousand years before the present kyr b p has limited the application of radiocarbon dating of samples from the last glacial period here we report 14c results from lake suigetsu japan 35 35 n 135 53 e which provide a comprehensive record of terrestrial radiocarbon to the present limit of the 14c method the time scale we present in this work allows direct comparison of lake suigetsu paleoclimatic data with other terrestrial climatic records and gives information on the connection between global atmospheric and regional marine radiocarbon levels

eolian inputs of lead to the north pacific we evaluate the importance of natural eolian pb to the dissolved oceanic pb budget by measuring the isotopic composition of pb in 35 holocene and late quaternary sediment samples from the north pacific and in 10 samples of chinese loess when the pacific is divided into sediments provinces based on published end and sedimentological data pb from the central north pacific tends to be the most radiogenic and homogeneous due to the dominance of eolian chinese loess lead from the marginal north pacific and the sparsely sampled regions south of 5 n are less radiogenic and more variable owing to hemipelagic inputs from various volcanic arcs and older continental crust located around the pacific rim 208pb 204pb ratios provide the most distinctive provenance information due to the relatively high ratios in chinese loess the chinese loess samples come from 3 localities and span up to 2 myr of time acetic acid leachate bulk loess and loess silicate fractions were analyzed separately leachate pb is considerably less radiogenic than silicate pb the isotopic composition of the silicate component closely matches the sediment data from the central north pacific confirming the dominance of eolian loess in this region we divided up a suite of published hydrogenous pb isotope data from the pacific ocean according to their locations within the three independently defined sediment provinces these data define three distinct fields differentiated primarily by their 206pb 204pb ratios which increase going from the central to southern to marginal provinces this relationship with sediment province strongly suggests that natural eolian and probably hemipelagic inputs significantly impact the seawater pb budget direct support for the dominance of eolian chinese loess in the central north pacific dissolved pb budget comes from the close match between loess leachate pb and the central province hydrogenous pb data eolian inputs are likely to dominate local seawater pb budgets only where eolian pb fluxes are high relative to hemipelagic pb fluxes and where the flux of pb carried by deep water advection is low

continuous record of microparticle concentration and size distribution in the central greenland ngrip ice core during the last glacial period 1 a novel laser microparticle detector used in conjunction with continuous sample melting has provided a more than 1500 m long record of particle concentration and size distribution of the ngrip ice core covering continuously the period approximately from 9 5 100 kyr before present measurements were at 1 65 m depth resolution corresponding to approximately 35 200 yr particle concentration increased by a factor of 100 in the last glacial maximum lgm compared to the preboreal and sharp variations of concentration occurred synchronously with rapid changes in the 18o temperature proxy the lognormal mode of the volume distribution shows clear systematic variations with smaller modes during warmer climates and coarser modes during colder periods we find 1 7 m diameter during lgm and 1 3 m during the preboreal on timescales below several 100 years and the particle concentration exhibit a certain degree of independence present especially during warm periods when generally is more variable using highly simplifying considerations for atmospheric transport and deposition of particles we infer that 1 the observed changes of in the ice largely reflect changes in the size of airborne particles above the ice sheet and 2 changes of are indicative of changes in long range atmospheric transport time from the observed size changes we estimate shorter transit times by roughly 25 during lgm compared to the preboreal the associated particle concentration increase from more efficient long range transport is estimated to less than one order of magnitude

grain size distribution and depositional processes of the mineral component of abyssal sediments lessons from the north pacific grain size analyses of the mineral component of abyssal pacific surface sediments show two distinctly different size distributions that can be associated with sediments that are dominantly eolian and dominantly hemipelagic respectively in the range of 1 to 30 m eolian grains show a distinct size mode at about 2 m 9 and little material coarser than about 16 m 6 hemipelagic grains are characterized by a much flatter size distribution that has a broad size mode near 2 m 9 and important amounts of material coarser than 16 m 6 this ability to distinguish between hemipelagic and eolian grains will obviate some long standing concerns in the interpretation of deep sea sediments examples of the utility of this technique are given for the north pacific and south atlantic

isotope geochemistry of mercury in source rocks mineral deposits and spring deposits of the california coast ranges usa abstract we present here the first study of the isotopic composition of mercury in rocks ore deposits and active spring deposits from the california coast ranges a part of earth s crust with unusually extensive evidence of mercury mobility and enrichment the franciscan complex and great valley sequence which form the bedrock in the california coast ranges are intruded and overlain by tertiary volcanic rocks including the clear lake volcanic sequence these rocks contain two types of mercury deposits hot spring deposits that form at shallow depths the franciscan complex and great valley sequence contain clastic sedimentary rocks with higher concentrations of mercury than volcanic rocks of the clear lake volcanic field mean mercury isotopic compositions 202hg for all three rock units are similar although the range of values in franciscan complex rocks is greater than in either great valley or clear lake rocks hot spring and silica carbonate mercury deposits have similar average mercury isotopic compositions that are indistinguishable from averages for the three rock units although 202hg values for the mercury deposits have a greater variance than the country rocks precipitates from spring and geothermal waters in the area have similarly large variance and a mean 202hg value that is significantly lower than the ore deposits and rocks these observations indicate that there is little or no isotopic fractionation

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds