the role of caco3 compensation in the glacial to interglacial atmospheric co2 change the only viable explanations put forth to date for the glacial to interglacial change in atmospheric co2 content suggested from measurements of the co2 content of gas extracted from ice cores involve changes in the ocean s nutrient cycles any nutrient change capable of creating the 80 atm changes in atmosphere co2 pressure suggested by the ice core results also creates significant change in the deep ocean s co3 content evidence from deep sea sediments suggests that these co3 changes are compensated on the time scale of a few thousand years by reductions or increases in amount of caco3 accumulating in deep sea sediments this compensation process has two important consequences first it significantly increases the magnitude of the co2 change per unit of nutrient forcing second it causes a delay in the response of the atmospheric co2 change while the first of these consequences is a boon to those seeking to explain the co2 change the second may prove to be a curse the ice core co2 record shows no evidence of a significant lag between the co2 response and the polar warming in any case it is important that we improve our knowledge of the magnitude and timing of the caco3 preservation events which mark the close of episodes of glaciation and of the dissolution events which mark the onset of these episodes

time variations of δ15n of organic nitrogen in deep western subarctic pacific sediment over the last 145 ka we present 15n data of organic nitrogen 15non from a deep western subarctic pacific wsap sediment core over the last 145 ka to remove the effect of inorganic nitrogen in on bulk nitrogen bn we used the contents of in and bn and the isotopic ratios of in 15nin and bn 15nbn the contribution of in to bn was largest 59 and 15nin had lower values than 15nbn however the large contributions of in to bn and the distinct isotopic values did not largely change any variability associated with 15non in the 15nbn thus it is possible to use 15nbn in carrying out paleoceanographic research with 15n at least in the open wsap the 15non values have been affected by long term diagenesis making the values lower with depth in the sediment but the values during less productive colder periods were generally lower compared to those during neighboring productive warmer periods the results might indicate that 15non during the less productive colder periods i e glacial periods were lower than that during the productive warmer periods i e interglacial periods previous studies have reported that the biological production in wsap where it is limited by iron at present during glacial periods was at more reduced level than during interglacials despite there being more eolian dust supply during glacial periods this indicates that the increase of biological production with enhanced iron supply derived from eolian dust during the glacial periods did not occur if this is the case and alternatively the iron input from the subsurface layer to the surface mixed layer by ventilation process is more important as suggested by recent works the variations in 15non would be explained by the variations in the fe no3 ratio in the upwelled water although 15non has been affected by long term diagenesis in the sediment the usage of this isotopic ratio provides new implication regarding the past ocean circulation in the open wsap

the bering and okhotsk seas modern and past paleoceanographic changes and gateway impact abstract the high biological productivity and an efficient biological pumping in the subarctic pacific and adjacent seas make this region important to the modern carbon cycle and both modern and the past climate of the earth knowledge of the northern marginal seas of the pacific however is unsubstantial the bering sea is located between the pacific ocean and the arctic sea and plays an important role in ocean circulation involving balances of heat salt and various chemical properties thus it is necessary to unravel the geologic history of the bering sea as a gateway to the pacific and the arctic atlantic during the last 5 million years and beyond the okhotsk sea is considered a locus of north pacific intermediate water formation today the intermediate water formation is linked with seasonal sea ice cover diatom records from the okhotsk sea demonstrate that sea ice cover was distributed on the western side of the sea and the eastern part was open water during the last glacial maximum this configuration permitted a better ventilation of the glacial okhotsk sea through increased quantity of intermediate water presumably formed there at that time

the bering sea and paleoceanography abstract this paper serves as an introduction to the bering sea preceding the 14 contributed papers contained in this volume several parts of the paper are allocated for current reviews of the bering sea included in the review topics are geomorphology surface water circulation and the importance of the formation of intermediate waters representative results of previous paleoceanographic studies are also presented in particular focusing on spatial and temporal distributions of biosiliceous microfossils as well as isotopic analyses of carbon and nitrogen concerning changes in productivity and nutrients motivations behind the scientific expeditions conducted which resulted in the many papers included here are briefly discussed in order to illustrate the recent trend in paleoceanography in the bering sea and the adjacent regions brief summaries or highlights of each of the contributed papers are given in order to provide an overview of the volume

volcano hydrothermal inflation revealed through spatial variation in stress field in tatun volcano group northern taiwan abstract to investigate the inflation characteristics of subsurface volcano hydrothermal activity we examine the spatial variability of the stress field in the tatun volcano group tvg of northern taiwan using 1016 earthquake focal mechanisms at depths shallower than 5 km from 2012 to 2017 we determine these focal mechanisms using the data from a dense seismic network composed of 40 seismic stations in an area of approximately 10 10 km2 in the tvg we find that this area is subject to the northwest southeast trended extension and subvertical compression the stress magnitude ratios near the dayoukeng area are significantly lower than that in the other areas this feature is likely related to an inflating source buried underneath the dayoukeng area our model shows good agreement between the observed and predicted values when the inflating pressure source located at a depth of approximately 2 km and with the average potency ranging from 1 4 105 to 7 105 m3 near the dayoukeng area we suggest that this inflation is associated with the local volcano hydrothermal activity this inflation is the principal pressure source in the shallow crust 5 km at depth in the tvg and may persist for at least a decade

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

orbital scale benthic foraminiferal oxygen isotope stratigraphy at the northern bering sea slope site u1343 iodp expedition 323 and its pleistocene paleoceanographic significance abstract a continuous composite oxygen isotope 18o stratigraphy from benthic foraminifera in the bering sea was reconstructed in order to provide insight into understanding sea ice evolution in response to northern hemisphere glaciation oxygen isotope records from multiple species of benthic foraminifera at integrated ocean drilling program iodp expedition 323 site u1343 54 33 4 n 176 49 0 e water depth 1950 m yield a highly refined orbital scale age model spanning the last 1 2 ma and a refined age model between 1 2 and 2 4 ma an inter species calibration was used to define species offsets and to successfully obtain a continuous composite benthic 18o record correlated with the global composite benthic 18o stack curve lr04 to construct an orbital scale age model the consistency of the benthic 18o stratigraphy with biostratigraphy and magnetostratigraphy confirms the reliability of both methods for constraining age the time difference between cyclic changes in sedimentary physical properties and glacial interglacial cycles since 0 8 ma is notable and suggests that physical properties alone cannot be used to construct an orbital scale age model amplitude changes in physical properties and a significant drop in the linear sedimentation rate during glacials after 0 9 ma indicate that the glacial sea ice edge extended beyond the bering sea slope site u1343 at this time

the yellowstone magmatic system from the mantle plume to the upper crust the yellowstone supervolcano is one of the largest active continental silicic volcanic fields in the world an understanding of its properties is key to enhancing our knowledge of volcanic mechanisms and corresponding risk using a joint local and teleseismic earthquake p wave seismic inversion we revealed a basaltic lower crustal magma body that provides a magmatic link between the yellowstone mantle plume and the previously imaged upper crustal magma reservoir this lower crustal magma body has a volume of 46 000 cubic kilometers 4 5 times that of the upper crustal magma reservoir and contains a melt fraction of 2 these estimates are critical to understanding the evolution of bimodal basaltic rhyolitic volcanism explaining the magnitude of co2 discharge and constraining dynamic models of the magmatic system for volcanic hazard assessment

deepwater formation in the north pacific during the last glacial termination between approximately 17 500 and 15 000 years ago the atlantic meridional overturning circulation weakened substantially in response to meltwater discharges from disintegrating northern hemispheric glacial ice sheets the global effects of this reorganization of poleward heat flow in the north atlantic extended to antarctica and the north pacific here we present evidence from north pacific paleo surface proxy data a compilation of marine radiocarbon age ventilation records and global climate model simulations to suggest that during the early stages of the last glacial termination deep water extending to a depth of approximately 2500 to 3000 meters was formed in the north pacific a switch of deepwater formation between the north atlantic and the north pacific played a key role in regulating poleward oceanic heat transport during the last glacial termination

a phreatic explosion model inferred from a very long period seismic event at mayon volcano philippines during a phreatic explosion at mayon volcano philippines on 7 may 2013 a very long period seismic event with a peak frequency of 0 4 hz was observed our frequency domain waveform inversion solution of the event in the frequency range 0 1 0 6 hz is consistent with a subhorizontal tensile crack and a vertical single force at a shallow location beneath the summit crater the source time functions obtained by the waveform inversion are band passed forms we estimated the deconvolved forms of the source time functions dstfs which are source time functions corrected for the effects of the band pass filter the dstf of the crack can be approximated by an impulse type function composed of inflation followed by deflation whereas the dstf of the single force can be approximated by a downward impulse the inflation of the crack may be attributed to boiling of underground water and its deflation can be attributed to discharge of water vapor whereas the downward force may be understood as the counterforce of the explosion our results suggest that only a portion of the crack wall was destroyed by the explosion we could not find clear precursors in seismic thermography geothermal geodetic and meteorological data we present a model of repeated explosions in which an explosion can occur once the fragmented portion of the crack is sealed by precipitation of clay minerals or hydrothermal secondary deposits this model may explain the absence of clear precursory signals before the 2013 explosion

on the preservation of laminated sediments along the western margin of north america 1 piston gravity and multicores as well as hydrographic data were collected along the pacific margin of baja california to reconstruct past variations in the intensity of the oxygen minimum zone omz gravity cores collected from within the omz north of 24 n did not contain laminated surface sediments even though bottom water oxygen bwo concentrations were close to 5 mol kg however many of the cores collected south of 24 n did contain millimeter to centimeter scale brown to black laminations in holocene and older sediments but not in sediments deposited during the last glacial maximum in addition to the dark laminations holocene sediments in soledad basin silled at 290 m also contain white coccolith laminae that probably represent individual blooms two open margin cores from 430 and 700 m depth that were selected for detailed radiocarbon dating show distinct transitions from bioturbated glacial sediment to laminated holocene sediment occurring at 12 9 and 11 5 ka respectively the transition is delayed and more gradual 11 3 10 0 ka in another dated core from soledad basin the observations indicate that bottom water oxygen concentrations dropped below a threshold for the preservation of laminations at different times or that a synchronous hydrographic change left an asynchronous sedimentary imprint due to local factors with the caveat that laminated sections should therefore not be correlated without independent age control the pattern of older sequences of laminations along the north american western margin reported by this and previous studies suggests that multiple patterns of regional productivity and ventilation prevailed over the past 60 kyr

sources of long chain fatty acids in deep sea sediments from the bering sea and the north pacific ocean abstract the distributions and compound specific carbon isotope ratios of long chain n fatty acids and long chain n alkanes in two sedimentary cores collected from the north pacific ocean and the bering sea have been examined long chain fatty acids were further fractionated into three sub fractions esterified free and polar to investigate their sources the 13 c values of these fractions clarified the sources of different fatty acids the esterified fraction had lighter 13 c values 30 1 0 70 similar to those of the long chain n alkanes 30 2 1 08 consistent with a mainly terrestrial plant origin in contrast the long chain fatty acids except c 28 from the polar and free fractions had heavier isotopic values 27 5 1 06 suggesting a mixed origin from terrestrial and marine organisms the esterified fatty acids from the north pacific ocean and the bering sea can be used as terrestrial biomarkers

large changes in seasonal sea ice distribution and productivity in the sea of okhotsk during the deglaciations changes in the surface environment of the central sea of okhotsk were reconstructed using tex86 paleothermometry facilitated by the bit index in order to investigate paleoenvironmental changes during the glacial interglacial cycles the core top tex86 derived temperature is the same as the present day summer sea surface temperature sst suggesting that tex86 records seasonal rather than annually averaged ssts in this region the tex86 record reveals 3 c lower summer sst during glacial maxima than during interglacial periods and significant warming during the deglaciations 15 10 ka and 136 130 ka this is consistent with previous inferences of more expanded and persistent seasonal sea ice during the glacial periods than the present day and its substantial retreat during the deglaciation timing of the deglacial warming also coincided with a distinct increase in coccolithophorid productivity suggesting a causal relationship between sea surface warming and coccolithophorid blooms during the deglaciations the relationship could reflect an increase in the supply of fresh and warm water from the amur river during deglaciation which significantly impacted hydrology by facilitating sea surface stratification which in turn promoted production of coccolithophids

earthquake slip weakening and asperities explained by thermal pressurization for the earth s crust to release accumulated stress in the form of an earthquake a fault must weaken and give way otherwise the movement would quickly grind to a halt due to the surrounding pressure this weakening is not really understood laboratory experiments simply don t match seismologists estimates of the distance a fault must slip before it becomes very weak a new study concludes that the missing ingredient is water geological studies and measurements show the slip zones to be narrow impermeable structures water already in the fault zone can quickly become pressurized by frictional heating as the rocks start to move catalysing large earthquakes from minor movements an earthquake occurs when a fault weakens during the early portion of its slip at a faster rate than the release of tectonic stress driving the fault motion1 2 this slip weakening occurs over a critical distance dc understanding the controls on dc in nature is severely limited however because the physical mechanism of weakening is unconstrained conventional friction experiments typically conducted at slow slip rates and small displacements have obtained dc values that are orders of magnitude lower than values estimated from modelling seismological data for natural earthquakes3 4 5 6 here we present data on fluid transport properties of slip zone rocks and on the slip zone width in the centre of the median tectonic line fault zone japan we show that the discrepancy between laboratory and seismological results can be resolved if thermal pressurization of the pore fluid7 8 9 10 is the slip weakening mechanism our analysis indicates that a planar fault segment with an impermeable and narrow slip zone will become very unstable during slip and is likely to be the site of a seismic asperity

relative geomagnetic paleointensity and δ18o at odp site 983 gardar drift north atlantic since 350 ka abstract at odp site 983 relative geomagnetic paleointensity and planktic and benthic 18o records have been acquired for the last 350 kyr the mean sedimentation rate in this interval is 11 3 cm kyr magnetic properties and hysteresis ratios indicate that pseudo single domain magnetite is the remanence carrier volume susceptibility k anhysteretic arm and isothermal irm remanence values vary by a factor of 3 4 well within the criteria usually cited for paleointensity studies natural remanent magnetization nrm is normalized by arm and irm to acquire the paleointensity proxy arithmetic means of nrm arm and nrm irm calculated for five demagnetization steps in the 25 45 mt range constitute the relative paleointensity estimates some paleointensity lows particularly those at 40 120 and 188 ka are associated with directional excursions of the field especially the event at 188 ka referred to here as the iceland basin event that constitutes a short lived polarity reversal for the last 200 kyr the records can be correlated with other high resolution paleointensity records such as those from the labrador sea mediterranean somali basin and sulu sea implying that the millennial scale features are globally synchronous a labeling system for paleointensity features is proposed that ties prominent highs and lows to oxygen isotope stages

new perspectives on beringian quaternary paleogeography stratigraphy and glacial history abstract aspects of the paleogeography stratigraphy and glacial history of beringia have been greatly revised over the past 15 20 yr access to north east russia in particular has provided the opportunity to evaluate the beringia landscape as a contiguous subcontinent during the quaternary for the first time new research has made clearer the connection between tectonic forces and the submergence of the bering strait during the middle pliocene revisions in the regional stratigraphy of glacial and interglacial deposits in northwest alaska and northeast russia provide a new foundation for assessing the causes for differences in glacial ice extent through time the consensus of all field workers verifies that glacial ice throughout most of beringia was of very limited extent during the last glacial maximum the onset of regional glaciation during the waning stages of the last interglaciation is clearly out of phase with glaciation at lower latitudes despite the lack of much glacial activity during the early holocene alaska contains a rich record of late holocene glacial response to neoglacial cooling changes in the holocene environment of beringia likely had a profound affect on early inhabitants the curiosity driven vision and spirit of both david hopkins and the late troy pewe have had a profound influence on arctic paleoenvironmental research

heat signature on the chelungpu fault associated with the 1999 chi chi taiwan earthquake 1 we have made observations of a heat signature that is associated with the frictional heat generated at the time of faulting for a large earthquake temperature measurements in a borehole that intersects the chelungpu fault at a depth of about 1100 m show a small increase near the fault even six years after the earthquake the temperature signature has a symmetric shape with a width of about 40 m and is centered on the fault that slipped about 5 m during the 1999 chi chi taiwan earthquake the small amplitude of 0 06 c for the observed temperature anomaly indicates a very low level of friction that generated heat at the time of the earthquake

direct ventilation of the north pacific did not reach the deep ocean during the last deglaciation 1 despite its tremendous size the deep north pacific has received relatively little attention by paleoceanographers it was recently suggested that the deep north pacific was directly ventilated by dense waters formed in the subarctic pacific during heinrich stadial 1 hs1 of the early deglaciation here we present new redox sensitive trace metal data from a sediment core at 2393 m in the subarctic pacific in comparison with previously published data from elsewhere in the region the combined picture shows no sign of ventilation during the early deglaciation in any available core from water depths of 2393 m and deeper while the deepest core to display clear signs of enhanced ventilation during hs1 was raised from 1366 m water depth thus it appears likely that although the north pacific was well ventilated to intermediate depths during hs1 the deep ocean did not receive a significant input of dense waters from a local source but remained isolated from the surface waters above

seismicity characteristics of a potentially active quaternary volcano the tatun volcano group northern taiwan the tatun volcano group tvg is located at the northern tip of taiwan near the capital taipei and close to two nuclear power plants because of lack of any activity in historical times it has been classified as an extinct volcano even though more recent studies suggestthattvgmighthavebeenactiveduringthelast20ka inmay2003aseismicmonitoringprojectatthetvgareawasinitiated by deploying eight three component seismic stations some of them equipped with both short period and broadband sensors during the 18 months observation period local seismicity mainly consisted of high frequency earthquakes either occurring as isolated events or as a continuous sequence in the form of spasmodic bursts mixed and low frequency events were also present during the same period eventhoughtheyoccurredonlyrarely arrivaltimesfromeventswithclearp s wavephaseswereinvertedinordertoobtaina minimum 1dvelocity modelwithstation corrections probabilistic nonlinear earthquakelocationswere calculated for allthese events using the newly derived velocity model most high frequency seismicity appeared to be concentrated near the areas of hydrothermal activity forming tight clusters at depths shallower than 4 km relative locations calculated using the double difference method and utilising catalogue and cross correlation differential traveltimes showed insignificant differences when compared to the nonlinear probabilistic locations in general seismicity in the tvg area seems to be primarily driven by circulation of hydrothermal fluids as indicated by the occurrence of spasmodic bursts mixed low frequency events and a b value 1 17 0 1 higher than in any other part of taiwan these observations that are similar to those reported in other dormant quaternary volcanoes indicate that a magma chamber may still exist beneath tvg and that a future eruption or period of unrest should not be considered unlikely

probable dynamic triggering of phreatic eruption in the tatun volcano group of taiwan abstract on 16 march 2014 utc a small phreatic eruption occurred in the tatun volcano group tvg of taiwan although it was not reported until analysis of both seismic and acoustic data revealed that the source was in the vicinity of the hsiaoyukeng fumarole a replay of the acoustic data accelerated 60 fold reveals that the gradual decrease in frequency that was recorded produces a volcanic whistle similar to the jet of steam released from a heating kettle the phreatic eruption may have been dynamically triggered by a m6 7 earthquake in chile a similar phenomenon occurred on 5 january 2015 when a phreatic eruption was recorded in the tvg immediately after the generation of dynamic seismic waves by an m5 0 earthquake in japan this is the first scientific report of a phreatic eruption detected in the tvg indicating that these volcanoes are still active as a result it is important to monitor their volcanic activity and identify volcanic reservoirs beneath the tvg to mitigate future possible volcanic impact

effects of pressure on pore characteristics and permeability of porous rocks as estimated from seismic wave velocities in cores from tcdp hole a summary changes in vp vs poisson s ratio around a fault are related to changes in the fluid transport properties of rocks which play a significant role in seismogenic processes here we report a notable relationship between vp vs and the permeability of porous fault related rocks chelungpu fault taiwan by direct and simultaneous measurement of elastic wave velocities vp and vs and permeability under increasing effective confining pressure peff up to 25 mpa vp and vs for all samples increased with peff in the range up to 20 mpa then were nearly constant as peff increased to 25 mpa most silty sandstones with large proportions of fine grained material showed positive correlations between vp vs and permeability with rising pressure on the other hand well sorted sandstones showed only slight changes in permeability with respect to vp vs with rising pressure we infer that grain size distributions in particular the amount of silt and clay size grains are responsible for the change in permeability with pressure as small particles clog pore networks with increasing peff causing the decrease in permeability these findings may be useful to explain changes in permeability and pore pressure in the deep crust

deep pacific caco 3 compensation and glacial interglacial atmospheric co 2 abstract benthic foraminiferal 13c suggests that there was a net shift of isotopically light metabolic co2 from the upper ocean into the deep ocean during the last glacial period according to the caco3 compensation hypothesis this should have caused a transient drop in deep ocean co32 that was eventually reversed by seafloor dissolution of caco3 the resulting increase in whole ocean ph may have had a significant impact on atmospheric co2 compounding any decrease that was due to the initial vertical co2 shift the opposite hypothetically occurred during deglaciation when co2 was returned to the upper ocean and atmosphere and deep ocean co32 temporarily increased followed by excess burial of caco3 and a drop in whole ocean ph the deep sea record of caco3 preservation appears to reflect these processes with the largest excursion during deglaciation as expected but various factors make quantification of deep sea paleo co32 difficult here we reconstruct deep equatorial pacific co32 over the last glacial interglacial cycle using benthic foraminiferal zn ca which is strongly affected by saturation state during calcite precipitation our data are in agreement with the caco3 compensation theory including glacial co32 concentrations similar to or slightly lower than today and a termination i co32 peak of 25 30 mol kg 1 the deglacial co32 rise precedes ice sheet melting consistent with the timing of the atmospheric co2 rise a later portion of the peak could reflect removal of co2 from the atmosphere ocean system due to boreal forest regrowth caco3 compensation alone may explain more than one third of the atmospheric co2 lowering during glacial times

enhanced marine productivity off western north america during warm climate intervals of the past 52 k y studies of the santa barbara basin off the coast of california have linked changes in its bottom water oxygen content to millennial scale climate changes as recorded by the oxygen isotope composition of greenland ice through the use of detailed records from a sediment core collected off the magdalena margin of baja california mexico we demonstrate that this teleconnection predominantly arose from changes in marine productivity rather than changes in ventilation of the north pacific as was originally proposed

very long period seismic signals at the tatun volcano group northern taiwan abstract very long period vlp seismic events have been detected in the tatun volcano group tvg located around the border between taipei city and new taipei city in northern taiwan in which has 7 million residents by using both analyses of particle motions and travel time delay one vlp volcanic earthquake s source is estimated to be at a shallow depth 800 m beneath mt chihsin which is the highest and youngest volcano in the tvg the significant variation of seismic energy at different azimuths provides strong evidence to distinguish a crack source from other kinds of sources such as a sphere vertical pipe or even double couple source this is further confirmed by synthetic modeling of the seismograms recorded at two stations as well as the compressional first motion at three seismic stations thus a deeper plumping system with high pressure fluid is required to generate the vlp signals and other volcanic earthquakes in the tvg combining this result with those of previous studies we conclude that the tvg might not be totally extinct and some further investigations must be carried out to improve understanding of the volcanic characteristics of the tvg

the russian component of an arctic ice sheet during the last glacial maximum abstract the extent of late weichselian glaciation in arctic russia remains a problem our model of 1995 1998 suggests a continuous and long lived ice sheet centered on the kara sea other reconstructions suggest a smaller and diachronous glaciation the vast majority of dates support the model of restricted glaciation we show that these dates are inconsistent with the geologic record of ice flow across the kara barents divide with second order glacial geology of kola peninsula and with evidence for glacial surges they are also inconsistent with late weichselian climate of the arctic with eurasian continental paleohydrology including meltwater drainage systems cataclysmic megafloods major transgressions of the caspian sea and with the entire paleogeographic context of northern eurasia we believe that due to impeded ventilation of the pleistocene arctic ocean these dates are often too old and that recycling and contamination of the samples would also contribute to the dating errors destructive impacts of late glacial ice sheet surges and megafloods upon the arctic glacial sequences would also aggravate the situation by ignoring the dates until these problems are addressed we find that the field evidence supports continuous glaciation of arctic russia at the lgm and that the resulting ice sheet was part of an arctic ice sheet that included an ice shelf in the arctic ocean and ice sheets in greenland and north america we present 3 d reconstructions of the arctic ice sheet and with an enlarged antarctic ice sheet we show that the ice volume is equivalent to an lgm sea level that was 130 135 m lower than at present the reconstructions depict the arctic ice sheet before and after massive thawing of the bed that allows partial gravitational collapse of the overlying ice with a minimal change in ice volume

reconstruction of paleoproductivity in the sea of okhotsk over the last 30 kyr 1 marine and terrestrial derived biomarkers alkenones brassicasterol dinosterol and long chain n alkanes as well as carbonate biogenic opal and ice rafted debris ird were measured in two sediment cores in the sea of okhotsk which is located in the northwestern pacific rim and characterized by high primary productivity down core profiles of phytoplankton markers suggest that primary productivity abruptly increased during the global meltwater pulse events 1a about 14 ka and 1b about 11 ka and stayed high in the holocene spatial and temporal distributions of the phytoplankton productivity were found to be consistent with changes in the reconstructed sea ice distribution on the basis of the ird this demonstrates that the progress and retreat of sea ice regulated primary productivity in the sea of okhotsk with minimum productivity during the glacial period the mass accumulation rates of alkenones caco3 and biogenic opal indicate that the dominant phytoplankton species during deglaciation was the coccolithophorid emiliania huxleyi which was replaced by diatoms in the late holocene such a phytoplankton succession was probably caused by an increase in silicate supply to the euphotic layer possibly associated with a change in surface hydrography and or linked to enhanced upwelling of north pacific deep water index terms 1050 geochemistry marine geochemistry 4835 4850 1055 geochemistry organic geochemistry 4267 oceanography general paleoceanography keywords okhotsk sea paleoproductivity sediment citation seki o m ikehara k kawamura t nakatsuka k ohnishi m wakatsuchi h narita and t sakamoto 2004 reconstruction of paleoproductivity in the sea of okhotsk over the last 30 kyr paleoceanography 19 pa1016

source mechanism of a very long period event at mt ontake central japan response of a hydrothermal system to magma intrusion beneath the summit abstract a very long period vlp volcanic event which occurred on 25 january 2007 beneath mt ontake central japan was recorded by nearby broadband seismometers as well as the japanese nationwide hi net and f net seismic networks the vlp waveforms show a pulse like shape with a duration of approximately 1 min the vlp event was accompanied by a burst sequence of long period lp events we carried out waveform inversion to determine the source mechanism and location of the vlp event our analysis indicates volumetric changes in an inclined crack seismic moment of 10 14 nm at the vlp source which is located at 0 6 km above sea level beneath the summit of mt ontake and above dikes determined from gps data the source time functions of the vlp event showed a pulse like triangular shape indicating inflation followed by deflation of the crack at the source we interpreted the result of the waveform inversion as follows gases released from the intruded magma heated an aquifer system beneath the summit of mt ontake a break of unstable superheated water in a hydrothermal crack in the system caused vaporization of water and associated crack inflation which was followed by discharge of steam from the crack resulting in its collapse these processes caused the vlp event which may have been a precursor of a small phreatic eruption that occurred in late march 2007

introduction to pliocene pleistocene paleoceanography of the bering sea abstract high resolution paleoceanography of the pliocene pleistocene is important in understanding climate forcing mechanisms and associated environmental changes during this major transition from global warmth to the ice ages this is particularly true in high latitude marginal seas such as the bering sea the bering sea has been very sensitive to changes in global climate during interglacial and glacial or milankovitch time scales this is due to significant changes in water circulation land ocean interaction and sea ice formation with the aim to reveal the climate and oceanographic history of the bering sea over the past 5 my iodp expedition 323 cored a total of 5741 m of sediment 97 4 recovery at seven sites in 2009 on d v joides resolution covering three regions the umnak plateau the bowers ridge and the bering slope the water depths of the drill sites range from 818 m to 3174 m allowing for the characterization of past vertical water mass distribution including changes in the oxygen minimum zone the four deepest holes range from 600 m to 745 m below the seafloor and resulted in the recovery of long sediment sequences ranging from 1 9 my to 5 my in age following the expedition two sampling parties at kochi core center for acquisition of ca 58 000 subsamples and two scientific meetings were conducted in order to proceed with the analyses of sediment core samples and discussions here pertinent results primarily from iodp expedition 323 are consolidated as a single special volume of deep sea research part ii topical studies in oceanography

post collisional magmatism around northern taiwan and its relation with opening of the okinawa trough being part of an active mountain belt formed by oblique collision of the luzon arc with asia northern taiwan and the offshore islets are marked by a series of latest pliocene quaternary volcanoes whose eruptions have been conventionally ascribed to westward propagation of the ryukyu volcanic arc on the basis of new geochemical data along with supporting geologic and geophysical evidence we propose instead that this young volcanism resulted from post collisional lithospheric extension in the northern taiwan mountain belt and the mantle source regions involved in the melt generation have been significantly modified by the nearby ryukyu subduction related processes magmas thus produced through the northeast to the southwest in the northern taiwan volcanic zone ntvz vary from low k to calc alkaline and then shoshonitic compositions such a spatial geochemical variation characterized by southwestward increase in enrichments of potassium and incompatible trace elements runs subparallel to the southwestern part of the present day ryukyu trench the geochemical variation that can be explained by southwestward decrease in degrees of partial melting of the mantle sources is reconciled with a southwestward weakening extensional regime observed in the ntvz the post collisional extension in northern taiwan furthermore might have played a role in reactivation of the opening in the middle okinawa trough and gave way to its rapid southwestward propagation with associated development of the ryukyu subduction zone west of124oe this nascent subduction in turn resulted in abundant submarine volcanoes which delineate an embryo volcanic front along the southern margin of the trough therefore the southwestern okinawa trough is not a fore arc basin as had been previously alleged but represents an atypical back arc basin which developed broadly synchronously or prior to its arc trench system in this particular collision extension subduction tectonic environment 1999 elsevier science b v all rights reserved

biogenic opal production changes during the mid pleistocene transition in the bering sea iodp expedition 323 site u1343 abstract biogenic opal content and mass accumulation rate mar at iodp expedition 323 site u1343 were found to fluctuate consistently generally being high under warm conditions and low under cold conditions during the last 2 4 ma continuous wavelet transform analysis of the normalized biogenic opal content indicates that export production in the bering sea varied predominantly at 41 ka periodicity before 1 25 ma and shifted to 100 ka periodicity at the onset of the mid pleistocene transition mpt 1 25 0 7 ma the 100 ka cycles dominated until the holocene export production in the bering sea decreased markedly in the bering sea two times during the mpt the first occurred at the beginning of the mpt 1 25 ma and the second in the middle of the mpt 0 9 ma these decreases coincided with both increases in the relative abundance of sea ice diatoms and decreases in the warm water diatom species neodenticula seminae indicating that reductions in export production in the bering sea during the mpt were associated with climate cooling decreases in export production in the bering sea during the mpt were most likely associated with the increased influence of polar arctic domains on the high latitude north pacific

effects of sea level sea ice extent and nutrient availability on primary production at the umnak plateau bering sea iodp site u1339 during marine isotope stage mis 5 abstract this study investigates how primary production responded to changes in nutrient availability sea level and sea ice coverage at the umnak plateau during marine isotope stage mis 5 and parts of mis 4 and mis 6 the umnak plateau during mis 4 and mis 6 had low primary production resulting from extensive sea ice coverage that enhanced stratification and limited nutrient replenishment this nutrient limitation was relieved during the deglaciation going into mis 5 when previously exposed continental shelves were flooded and the eastern aleutian island passes were opened by an increase in sea level resulting in an increase in productivity opening and closing of the eastern aleutian island passes during the rest of mis 5 reflected fluctuations in sea level and likely affected nutrient sources and productivity at the umnak plateau nutrients during sea level lowstands were likely sourced by the aleutian north slope current whereas most of the sea level high stands throughout mis 5 had nitrogen sourced by an increase in nitrogen fixation and the assimilation of remineralized nitrogen which led to highly depleted nitrogen isotope values never before seen for the northern pacific higher sea level and productivity near the beginning of mis 5 likely reflected mis 5e however a discrepancy between two diatom productivity proxies suggests that changing environmental conditions stimulated a change in the dominant diatom species this highlights the complexities associated with productivity in the bering sea and emphasizes the need to continue studying how productivity and ecosystems changed during previous warm periods

changes and influencing factors in biogenic opal export productivity in the bering sea over the last 4 3 ma evidence from the records at iodp site u1340 we reconstructed changes in biogenic opal export productivity boep in the southern bering sea bs over the last similar to 4 3 ma based on mass accumulation rate mar of biogenic opal from integrated ocean drilling program iodp site u1340 the results show that the boep in the bs was high and variable between similar to 4 3 and similar to 1 9 ma extremely low and relatively stable from similar to 1 9 to similar to 1 1 ma and then fluctuated frequently generally high during interglacials and low during glacials during the last similar to 1 1 ma one interval of enhanced boep from similar to 4 3 to similar to 3 2 ma is a response to the late miocene early pliocene biogenic bloom event another interval from similar to 2 8 to similar to 1 9 ma correlates with global opal burial shifting from high latitude oceans to upwelling influenced regions following the intensification of the northern hemisphere glaciation nhg whereas the increase in bs opal export productivity during the last similar to 1 1 ma tends to be a local phenomenon overall the boep shows a similar trend and good correspondence to the input of the alaskan stream as which can be traced using the na2o k2o ratio we thus conclude that the as may be the direct and primary factor on boep variability in the bs during the last similar to 4 3 ma in addition although the poor correlation between opal mar and volcanic glass suggests that boep variability was not controlled by longterm variations in the volcanism or ash abundance increased ash abundance indicated by high contents of volcanic glasses was also a possible reason for enhanced boep during the period from similar to 4 3 to similar to 3 2 ma and the last similar to 0 5 ma

glacial age hydrography of the far northwest pacific ocean stable isotope data on benthic foraminifera from more than 30 cores on the northern emperor seamounts and in the okhotsk sea are synthesized in paleohydrographic profiles spanning the depth range 1000 4000 m holocene core top benthic foraminiferal 18o and 13c data are calibrated to modern hydrographic properties through measurements of 13c of co2 and 18o of seawater cibicidoides stable isotope ratios are close to the 13c and equilibrium 18o of seawater whereas uvigerina 18o and 13c are variably offset from cibicidoides glacial maximum 13c of cibicidoides displays a different vertical profile than that of the holocene when results are adjusted by 0 32 to account for the secular change in 13c during the last glacial maximum the data coincide with the modern seawater and foraminiferal curves deeper than 2 km however at shallower depths 13c gradually increases by as much as 1 above the modern value furthermore above 2 km the benthic 18o decreases by 0 5 these results are consistent with a benthic front at 2 km in the north pacific see herguera et al 1992 but they differ from interpretations based on trace metal data which indicate a source of nutrient depleted deep water during glaciation the isotopic data suggest that during glaciation there was a better ventilated watermass at intermediate depths in the far northwestern pacific it was relatively fresher than deep waters there and deep waters were as nutrient rich as today

transport through unimak pass alaska we examined inflow through unimak pass 200 m deep which is the only major connection between the shelves of the north pacific ocean and the eastern bering sea geostrophic transport was generally northward from the gulf of alaska into the bering sea the flow through the pass appeared to be modulated by the seasonal cycle of freshwater discharge on shorter time scales transport also was affected by semi daily variations in tidal mixing this effect was significant and not anticipated near bottom currents measured from moorings were maximum during winter and significantly correlated r 0 7 with the alongshore winds although the flow through unimak pass transported some nutrients from the north pacific ocean the gulf of alaska shelf is not the major source of nutrients to the bering sea shelf

a diatom record of mid to late holocene palaeoenvironmental changes in the southern okinawa trough palaeoceanographic changes over the last 6800 years are documented in a diatom record from core md05 2908 from the southern okinawa trough changes in diatom components are used to reflect variations in the strength of the kuroshio current and the influence of coastal waters and these changes are compared with records of the east asian summer monsoon which exerts an important influence on regional climate and oceanography a decreasing trend in the contribution of coastal diatoms during the last 6800 years is related to the weakening of the east asian summer monsoon during the holocene in response to diminishing insolation and a southward shift in the intertropical convergence zone relatively high abundances of the kuroshio current indicator species during the intervals 2600 2200 and 4800 3600 cal a bp and lower abundances during the intervals 3200 2800 and 2200 1300 cal a bp imply that there is no consistent weakening of the kuroshio current during the interval 4500 3000 cal a bp the pulleniatina minimum event which is a widespread feature in the east china sea and the south china sea a major reduction in coastal diatoms at 3200cal a bp and a slight decrease in the kuroshio current indicator species during the interval 3200 2800 cal a bp indicate that a palaeoceanographic shift occurred in the southern okinawa trough which coincided with a northern hemisphere climatic cooling denoted the neoglaciation in europe in addition changes in the freshwater species component of the record are suggested mainly to result from variations in flood frequency in north eastern taiwan caused by typhoons a dramatic increase in the frequency of flood events during the last millennium may have been caused by relatively strong el nino southern oscillation activity compared with the more stable period between 6800 and 1000 cal a bp which experienced a low frequency of flood events

paleointensity of the geomagnetic field during the last 80 000 years high resolution records of the relative paleointensity of the geomagnetic field have been obtained from five marine cores three duplicate records were used to estimate the regional coherency of the data within a single area tyrrhrenian sea while the two others document the field variations in the eastern mediterranean and the southern indian ocean careful investigations of distinct rock magnetic parameters have established the downcore uniformity of the sediments in terms of magnetic mineralogy and grain sizes the time depth control was provided by oxygen isotopes and small scale variations in the deposition rates were constrained by means of tephrachronology the synthetic curve calculated from the mediterranean records provides a continuous record of the intensity variations during the last 80 000 years 80 kyr which correlates well with the sparse volcanic data available for the period 0 40 kyr the fact that identical behavior is seen in both data sets and that they also compare quite well with results from a core collected in the pacific ocean establishes the truly dipolar character of these variations the dipole field moment is characterized by large scale changes as shown by the existence of pronounced drops at 39 and 60 kyr alternating with periods of higher intensity the record suggests a periodic nature for these intensity variations however the period studied is not sufficiently long to state this conclusively these results demonstrate the potential of sediments for such studies and constitute a first step towards obtaining a global paleointensity record over a long period of time

the deglacial transition on the southeastern alaska margin meltwater input sea level rise marine productivity and sedimentary anoxia 1 oxygen isotope data from planktonic and benthic foraminifera on a high resolution age model 44 14c dates spanning 17 400 years document deglacial environmental change on the southeast alaska margin 59 33 32 n 144 9 21 w 682 m water depth surface freshening i e 18o reduction of 0 8 began at 16 650 170 cal years b p during an interval of ice proximal sedimentation likely due to freshwater input from melting glaciers a sharp transition to laminated hemipelagic sediments constrains retreat of regional outlet glaciers onto land circa 14 790 380 cal years b p abrupt warming and or freshening of the surface ocean i e additional 18o reduction of 0 9 coincides with the bolling interstade of northern europe and greenland cooling and or higher salinities returned during the allerod interval coincident with the antarctic cold reversal and continue until 11 740 200 cal years b p when onset of warming coincides with the end of the younger dryas an abrupt 1 reduction in benthic 18o at 14 250 290 cal years b p likely reflects a decrease in bottom water salinity driven by deep mixing of glacial meltwater a regional megaflood event or brine formation associated with sea ice two laminated opal rich intervals record discrete episodes of high productivity during the last deglaciation these events precisely dated here at 14 790 380 to 12 990 190 cal years b p and 11 160 130 to 10 750 220 cal years b p likely correlate to similar features observed elsewhere on the margins of the north pacific and are coeval with episodes of rapid sea level rise remobilization of iron from newly inundated continental shelves may have helped to fuel these episodes of elevated primary productivity and sedimentary anoxia

late pliocene to early pleistocene 2 4 1 25 ma paleoproductivity changes in the bering sea iodp expedition 323 hole u1343e abstract late pliocene to early pleistocene paleoproductivity changes in the bering sea were reconstructed using geochemical concentrations and mass accumulation rates mars of caco 3 biogenic opal and total organic carbon toc and sedimentary nitrogen isotope ratios 15 n at iodp expedition 323 hole u1343e drilled in the northern slope area 1956 m deep of the bering sea caco 3 concentration is generally low but prominent caco 3 peaks occur intermittently due to subseafloor authigenic carbonate formation rather than biogenic accumulation regardless of glacial interglacial variations biogenic opal concentrations reflect orbital scale glacial interglacial variations however toc concentration did not show clear glacial interglacial variation probably due to poor preservation the sedimentary 15 n values vary synchronously with biogenic opal concentration on orbital timescales the co varying pattern of opal productivity and 15 n values at hole u1343e is a result of nutrient utilization controlled by diatom productivity in the bering slope area where fe is not a limiting factor biogenic opal and toc mars showed a temporal shift at around 1 9 ma from a high productivity period under nutrient enriched conditions to a low productivity period under relatively nutrient depleted conditions high diatom productivity with low 15 n values before 1 9 ma is associated with abundant nutrient supply by upwelling in relation to strong surface current system this productivity decrease at about 1 9 ma was also found in the southern bering sea site u1341 and may be related to global opal reorganization

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 20 000 year record of ocean circulation and climate change from the santa barbara basin much of the evidence for climate driven fluctuations in ocean circulation during the past 20 000 years has come from studies of the north atlantic region1 6 the extent to which such interactions have occurred in other ocean basins and any associated teleconnec tions between basins is poorly understood here we present high resolution palaeoclimate and palaeoceanographic records from a 20 000 year sedimentary sequence from the santa barbara basin on the eastern margin of the north pacific ocean the sequence shows oscillations of the benthic environment between low oxygen conditions laminated sediments during periods of warm climate and higher oxygen conditions non laminated bioturbated sediments during cool intervals age differences between coexisting benthic and planktonic foraminifers indicate climate related changes in the age and source and hence oxygen content of basin bottom waters relatively young bottom waters are associated with the cooler intervals and are considered to reflect high proportions of intermediate waters derived from proximal sources conversely older bottom waters are associated with the warmer intervals and were derived from more distal sources these climate driven variations in ocean circulation appear to be synchronous with the main ocean climate fluctuations in the north atlantic region1 6 suggesting that a tight coupling mechanism operates between the two basins

clay mineral stratigraphy during the last 2 4ma at iodp exp 323 site u1343 in the bering sea abstract the clay mineral composition at iodp exp 323 site u1343 in the bering sea was analyzed so as to unravel their provenance over glacial interglacial cycles for the last 2 4 ma smectite was negatively correlated with the sum of illite and chlorite therefore their ratio s i c was used as an indicator of clay mineral composition changes in general the s i c ratio was rather similar for glacial and interglacial periods during most of the last 2 4 ma in addition these results overlap with those of surface sediments in the modern east aleutian basin which suggests that smectite rich clay particles are delivered from the aleutians by the northward bering slope current bsc rather than from rivers in western alaska however some clay mineral compositions of the glacial periods after the mid pleistocene transition mpt 1 25 0 7 ma were characterized by low illite and relatively high smectite during this period extensive ice rafting might have transported the smectite rich clay particles to site u1343 from the glacial shelf off alaska and or from glacial rivers from that area

a review on phreatic eruptions and their precursors abstract an analysis of the reported information on 132 historical phreatic events indicates that most of these 115 were not followed by a magmatic or phreatomagmatic eruption only in 18 cases precursory phenomena are reportedly lacking whereas they are recognized for the majority 72 of the considered cases these precursors have been analyzed as a function of the kind of phreatic event and of its possible triggering mechanism unfortunately the quality of the available information is poor however data suggest that anomalous seismicity ground deformation changes in the output chemistry and temperature of fumaroles and thermal springs are potential mid term precursors whereas seismic tremor is a common short term precursor

productivity changes in the bering sea during the late quaternary changes in biological productivity of the bering sea have been evaluated for the late quaternary based on biogenic opal calcium carbonate and microfossils in two piston cores biological productivity increased during marine isotope stage mis 1 after the last glaciation during the last deglaciation two pronounced peaks of calcium carbonate content were observed at ca 2400 m water depth which can be explained by the caco3 compensation hypothesis and coccolithophore blooms simultaneous with the caco3 peaks oxygen poor deep water was apparently distributed in the aleutian basin based on benthic foraminiferal assemblages the low o2 events seem to be related to deep water circulation and or elevated productivity in the northwest pacific after the caco3 peak events biogenic opal contents and diatoms increased gradually associated with enhanced vertical mixing with an inflow of the alaskan stream through the eastern aleutian arc passes r 2005 elsevier ltd all rights reserved

in situ calcium carbonate dissolution in the pacific ocean over the past several years researchers have been working to synthesize the woce jgofs global co2 survey data to better understand carbon cycling processes in the oceans the pacific ocean data set has over 35 000 sample locations with at least two carbon parameters oxygen nutrients cfc tracers and hydrographic parameters in this paper we estimate the in situ caco3 dissolution rates in the pacific ocean water column calcium carbonate dissolution rates ranging from 0 01 1 1 mmol kg1 yr1 are observed in intermediate and deepwater beginning near the aragonite saturation horizon in the north pacific intermediate water between 400 and 800 m caco3 dissolution rates are more than 7 times faster than observed in middle and deep water depths average 0 051 mmol kg1 yr1 the total amount of caco3 that is dissolved within the pacific is determined by integrating excess alkalinity throughout the water column the total inventory of caco3 added by particle dissolution in the pacific ocean north of 40s is 157 pg c this amounts to an average dissolution rate of approximately 0 31 pg c yr1 this estimate is approximately 74 of the export production of caco3 estimated for the pacific ocean these estimates should be considered tomore be upper limits for in situ carbonate dissolution in the pacific ocean since a portion of the alkalinity increase results from inputs from sediments less

preliminary analysis of volcanoseismic signals recorded at the tatun volcano group northern taiwan 1 the tatun volcano group lies at the northern tip of taiwan only 15 km north of the capital taipei a seismic array consisting of 5 stations equipped with both broadband and short period sensors was installed in 2003 in order to monitor the seismic activity of the area it recorded a variety of events including common volcano tectonic earthquakes and volcanoseismic signals like tornillos short duration monochromatic events 10 15 s and long duration spasmodic bursts 15 min an analysis of the complex frequencies of the tornillo monochromatic signals shows that q values are of the order of several hundreds based on the model of a fluid filled crack such q values can result from the oscillations of a crack containing a misty or dusty gas these observations put into doubt the long standing suggestion that the tatun volcanoes are extinct and prompt for a thorough assessment of the volcanic hazard for this area

elastic wave velocities and permeability of cracked rocks abstract cracks play a major role in most rocks submitted to crustal conditions mechanically cracks make the rock much more compliant they also make it much easier for fluid to flow through any rock body relying on fracture mechanics and statistical physics we introduce a few key concepts which allow to understand and quantify how cracks do modify both the elastic and transport properties of rocks the main different schemes which can be used to derive the elastic effective moduli of a rock are presented it is shown from experimental results that an excellent approximation is the so called non interactive scheme the main consequences of the existence of cracks on the elastic waves is the development of elastic anisotropy due to the anisotropic distribution of crack orientations and the dispersion effect due to microscopic local fluid flow at a larger scale macroscopic fluid flow takes place through the crack network above the percolation threshold two macroscopic fluid flow regimes can be distinguished the percolative regime close to the percolation threshold and the connected regime well above it experimental data on very different rock types show both of these behaviors

intensification of the northeast pacific oxygen minimum zone during the bolling allerod warm period although climate records from several locations around the world show nearly synchronous and abrupt changes the nature of the inferred teleconnection is still poorly understood on the basis of preserved laminations and molybdenum enrichments in open margin sediments we demonstrate that the oxygen content of northeast pacific waters at 800 m depth during the bolling allerod warm period 15 13 kyr was greatly reduced existing oxygen isotopic records of benthic and planktonic foraminifera suggest that this was probably due to suppressed ventilation at higher latitudes of the north pacific comparison with ventilation records for the north atlantic indicates an antiphased pattern of convection relative to the north pacific over the past 22 kyr perhaps due to variations in water vapor transport across central america

evidence of frictional melting from disk shaped black material discovered within the taiwan chelungpu fault system 1 the taiwan chelungpu fault drilling project penetrated three fault zones as the chelungpu fault system which slipped during the 1999 chi chi earthquake discovering disk shaped black material bm disk within the middle and lower fault zones in hole b the microscopic features of the bm disks indicated that they were pseudotachylytes and they showed high magnetic susceptibility possibly the result of intense shearing or high temperature conditions inorganic carbon content of the bm disks was low possibly because of thermal decomposition of carbonate minerals the high temperatures might be related to frictional heating during the earthquake implying that the bm disks were produced under intense shearing with frictional heating that reached melting temperature because the disks which provide the only evidence of melting pre date the 1999 earthquake we concluded that frictional melting did not occur during the earthquake

biogenic opal indicating less productive northwestern north pacific during the glacial ages 1 biogenic opal and ice rafted detritus ird data from sediments in the okhotsk sea and the neighboring north pacific revealed the remarkable reduction in opal production and southward advancement of sea ice covered area during the last glacial maximum resulting also southward shift of high biological productive area in the northwestern north pacific it implies that the substantial reduction in outflux of co2 to the atmosphere in northwestern north pacific and the pronounced increase in co2 sequestering in temperate north pacific this could be an additional co2 reduction mechanism of atmospheric co2 in the last glacial period

interior hydrography and circulation of the glacial pacific ocean abstract the deep water of the pacific ocean is a key component of the global climate system on the time scale of late pleistocene glaciation and deglaciation despite its importance the deep pacific during the last glacial maximum has received relatively little attention compared to the deep atlantic in part because the pacific poorly preserves carbonate sediments on the sea floor here we review the current state of knowledge of the deep hydrography and circulation of the glacial pacific by examining available nutrient proxy data including some new 13 c and 18 o data measured on benthic foraminifera planulina wuellerstorfi from the vicinity of japan available benthic 13 c and 18 o and radiocarbon data from the pacific support the presence of a deep hydrographic boundary at around 2000 m during the last glacial maximum paleoceanography 3 1988 343 paleoceanography 7 1992 273 paleoceanography 13 4 1998 323 the deep hydrographic divide in the glacial pacific is similar to what is inferred in the atlantic quaternary research 18 1982 218 paleoceanography 3 1988 317 paleoceanography 3 1988 343 annual reviews of earth planetary sciences 20 1992 245 science 259 1993 1148 the indian nature 333 1988 651 paleoceanography 13 1998 20 and the southern ocean paleoceanography 11 1996 191 suggesting that this is a global phenomenon during the glacial time the upper water mass has a distinctly enriched 13 c compared to the deeper water mass whose possible origins are discussed

a biomarker approach for assessing marine and terrigenous inputs to the sediments of sea of okhotsk for the last 27 000 years abstract a sediment core taken from the sea of okhotsk which is located in the western north pacific rim with an extensive seasonal sea ice cover was investigated for lipid class compounds total organic carbon total nitrogen and 13 c of bulk organic matter to reconstruct changes in sedimentary regimes of marine and terrestrial organic matter over the last 27 kyrs higher molecular weight n alkanes fatty acids and fatty alcohols showed an increase in terrigenous inputs in glacial and to a greater extent in early deglacial periods the enhanced terrestrial input in the deglaciation stages has for the first time been found and never been reported in the open ocean biomarker profiles together with the coarse grain size distribution in nearby sediment cores suggested that sea ice rafting was the main transport mechanism of continental material to the okhotsk sea sediments however the ice rafting inputs have been weakened from 14 kyrs bp to the holocene probably due to a rapid reduction of the sea ice cover and continental shelf erosion profiles of c 37 alkenones phytol and brassicasterol as well as temporal variation in calcium carbonate and organic carbon contents indicated that the marine inputs were enhanced during the deglaciation the enhanced marine inputs were likely caused by an intensification of the primary production induced by a possibly increased nutrient supply from the continental shelves in early deglaciation and by the deglacial retreat of the sea ice cover at 14 kyrs bp this study demonstrates that biomarkers in the marginal marine sediments had recorded changes in the biogeochemical processes in the sea of okhotsk over the last 27 kyrs which may be significantly affected by changes in the okhotsk water exchange processes such as sea ice activity and sea ice transport of terrigenous materials

volcano hydrothermal activity detected by precise levelling surveys at the tatun volcano group in northern taiwan during 2006 2013 abstract precise levelling surveys were conducted from 2006 to 2013 on three levelling routes in the tatun volcano group tvg located approximately 15 km northeast of taipei to detect deformation in relation to the volcano hydrothermal activities of the tvg uplift was detected around the most active fumarole tayoukeng fumarole throughout the period 2007 to 2011 the uplift rate throughout the period from march 2009 to march 2011 was reduced in comparison to the rate between 2007 and 2009 following this a dormant state or a small amount of subsidence was detected in the period march 2011 to march 2013 and throughout the period from june 2006 to march 2013 subsidence was centred on an area 0 5 km east of the summit of mt cising the highest peak in the tvg a model of two spherical sources was therefore estimated from the deformation recorded from august 2007 to march 2011 using a genetic algorithm a deflation source was obtained about 0 5 km northeast of mt cising at a depth of 2 km and an inflation source was situated approximately 1 km south of the tayoukeng fumarole at a depth of 0 7 km based on previous seismic and amt studies the estimated sources are interpreted as being hydrothermal reservoirs because almost all the benchmarks around mt cising show subsidence at a constant speed we conclude that the deeper hydrothermal reservoir at a depth of 2 km may have been releasing hydrothermal fluid at a constant rate throughout the period from 2006 to 2013 however it was suggested that in 2011 the shallower hydrothermal reservoir at a depth of 0 7 km changed from an inflation state to a dormant state or small deflation based on temporal vertical changes around tayoukeng fumarole a possible model for the volcano hydrothermal system is therefore proposed it is considered that the hydrothermal fluid may be supplied intermittently from the magma chamber to the deeper hydrothermal reservoir at a depth of 2 km although this type of fluid input event may not have occurred during our research period and that the hydrothermal fluid upwelling between mt cising and tayoukeng fumarole flows transversally into a highly cracked and fluid saturated area that continues to tayoukeng fumarole the existence of a shallower hydrothermal reservoir at a depth of 0 7 km in the highly cracked and fluid saturated area is therefore plausible

glacial to interglacial surface nutrient variations of bering deep basins recorded by δ13c and δ15n of sedimentary organic matter stable carbon and nitrogen isotopic ratios 13c and 15n of organic matter were measured in three sediment cores from deep basins of the bering sea to investigate past changes in surface nutrient conditions for surface water reconstructions hemipelagic layers in the cores were distinguished from turbidite layers on the basis of their sedimentary structures and 14c ages and analyzed for isotopic studies although 13c profiles may have been affected by diagenesis both 15n and 13c values showed common positive anomalies during the last deglaciation we explain these anomalies as reflecting suppressed vertical mixing and low nutrient concentrations in surface waters caused by injection of meltwater from alpine glaciers around the bering sea appendix tables are available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington dc 20009 document p95 003 2 50 payment must accompany order

tomography of the source area of the 1995 kobe earthquake evidence for fluids at the hypocenter seismic tomography revealed a low seismic velocity 5 and high poisson s ratio 6 anomaly covering about 300 square kilometers at the hypocenter of the 17 january 1995 magnitude 7 2 kobe earthquake in japan this anomaly may be due to an overpressurized fluid filled fractured rock matrix that contributed to the initiation of the kobe earthquake

influence of northwest pacific productivity on north pacific intermediate water oxygen concentrations during the bolling allerod interval 14 7 12 9 ka elevated productivity in the northwest pacific is suggested as a new possible control driving past intervals of low o2 intermediate water along the western continental margin of north america according to this mechanism o2 consumption would occur near the site of formation of north pacific intermediate water npiw due to increased respiration of organic carbon in response to a high productivity event evidence is provided for such a productivity increase during the bolling allerod interval 14 7 12 9 ka a time when laminated sediments were deposited along the northern california margin by this mechanism low o2 events in intermediate waters off the western north american margin could occur without significant changes in the rate of npiw ventilation

carbonate deposition and benthicδ13c in the subarctic pacific implications for changes of the oceanic carbonate system during the past 750 000 years abstract carbonate deposition at two core sites in the subarctic pacific 48 n 133 w 2 9 km and 3 7 km water depth follows the standard pacific carbonate cycles with glacial values being increased over interglacial values benthic 13c follows the global trend that is glacial values are more negative than interglacial values comparison with the benthic 13c record of north atlantic dsdp site 552 56 n 23 w 2 3 km water depth shows the north pacific records to be nearly in phase with and continuously more negative relative to the north atlantic record this suggests that concentrations of co2 org were permanently higher in the north pacific than in the north atlantic during the past 750 000 years conceivably supporting the hypothesis that there was no deep water forming in the late pleistocene north pacific whereas one would expect that the north pacific deep waters were continuously more corrosive to carbonates than deep waters in the north atlantic carbonate deposition at the deep north pacific core sites is enhanced during glacial periods and occasionally higher than at shallow north atlantic site 552 even though site 552 was probably above lysocline depth during most of the late pleistocene this apparent paradox can be resolved only by invoking an increase in alkalinity in the glacial north pacific which would have increased the degree of carbonate ion saturation and thereby improved the state of carbonate preservation

synthesis and thermal decomposition of tetragonal rbclo4 and volume of fluid o2 from 2 to 9 gpa 1 orthorhombic o rbclo4 transforms to a new tetragonal t form at pressures above 20 kbar thermal decomposition proceeds through the reversible equilibrium reaction t rbclo4 b2 rbcl 2o2 at modestly increasing temperatures centered 550 c over the pressure range investigated from 20 to 90 kbar cell volumes for t rbclo4 and b2 rbcl were determined by high pressure high temperature in situ x ray diffraction on station 16 4 of the daresbury synchrotron radiation source from which the partial molar volume of o2 along the decomposition curve was determined this volume 10 cm3 mol is in close agreement with volumes determined from studies of the thermal decomposition of kclo3 and kclo4 but is difficult to reconcile with fluid o2 volumes determined using shock wave techniques if these new o2 partial molar volumes are relevant to molten iron solutions then storage of substantial amounts of o2 in the core becomes feasible

diatom stratigraphy of the late pleistocene brunhes subarctic pacific sancetta c and silvestri s m 1984 diatom stratigraphy of the late pleistocene brunhes subarctic pacific mar micropaleontol 9 263 274 three piston cores in the subarctic region of the north pacific show consistent changes in relative abundance of diatom species throughout the brunhes magnetic epoch these events can be used both as stratigraphic markers to subdivide the interval and as indicators of oceanographic conditions the stratigraphic record shows an acme for a ochotensis from about 625 350 kyr isotope stages 15 10 a marked increase in amplitude of abundance fluctuations for r hebetata 300 0 kyr stages 8 1 the extinction of r curvirostris at 276 kyr stage 8 and abundance fluctuations of d seminae roughly in phase with the global oxygen isotope record from 450 0 kyr stages 12 1 in the subarctic pacific an abrupt change in species abundance is not a reliable indicator of hiatus occurrence although details are not clear there appears to have been a fundamental change of the subarctic gyre during the middle brunhes stages 10 8 time with more intense glacial intervals and stronger glacial interglacial contrast occurring after that time coarse clastic detritus is not restricted to glacial intervals suggesting that ice rafting has occurred throughout the brunhes interval peak levels of ice rafting may occur during ice growth and decay as well as during short intervals within a stage

evidence for a reduction in the carbonate ion content of the deep sea during the course of the holocene the paleo carbonate ion proxy proposed by broecker et al 1999 is applied in a search for trends in the holocene acidity of waters in the transition zone between north atlantic deep water and antarctic bottom water aabw a clear signal emerges that the carbonate ion content of waters in this zone declined during the past 8000 years in order to determine whether this decline represents a strengthening of the northward penetrating tongue of low co3 content aabw or a global reduction of co3 ion measurements were made on a core from the ontong java plateau in the western equatorial pacific evidence for a similar decline in co3 ion over the course of the holocene was obtained lending support of the latter explanation such a drop is consistent with the recent finding by indermuhle et al 1999 that the co2 content of the atmosphere as recorded in the taylor dome antarctica ice core rose by 20 25 ppm during the past 8000 years

evidence from diatom bound nitrogen isotopes for subarctic pacific stratification during the last ice age and a link to north pacific denitrification changes higher diatom bound d 15 n 70 wt lower opal content and 1200 ppm lower biogenic barium taken together and with constraints on sediment accumulation rate these results suggest a reduced supply of nitrate to the surface due to stronger stratification of the upper water column of the bering sea during glacial times with more complete nitrate consumption resulting from continued iron supply through atmospheric deposition this finding extends the body of evidence for a pervasive link between cold climates and polar ocean stratification in addition we hypothesize that more complete nutrient consumption in the glacial age subarctic pacific contributed to the previously observed ice age reduction in suboxia and denitrification in the eastern tropical north pacific by lowering the nutrient content of the intermediate depth water formed in the subpolar north pacific in the deglacial interval of the bering sea record two apparent peaks in export productivity are associated with maxima in diatom bound and bulk sediment d 15 n the high d 15 n in these intervals may have resulted from greater surface nutrient consumption during this period however the synchroneity of the deglacial peaks in the bering sea with similar bulk sediment d 15 n changes in the eastern pacific margin and the presence of sediment lamination within the bering sea during the deposition of the productivity peaks raise the possibility that both regional and local denitrification worked to raise the d 15 n of the nitrate feeding bering sea surface waters at these times

chronostratigraphy of sediment cores from the bering sea and the subarctic pacific based on paleomagnetic and oxygen isotopic analyses the chronostratigraphy of six piston cores collected from the bering sea and one piston core from the subarctic pacific is reported age models are primarily based on oxygen isotope data from cores bow 8a and es in conjuction with relative paleointensity proxy records biogenic opal data and a radiolarian datum from other cores whose sediments mainly consist of diatom microfossils and poorly preserved calcium carbonate the records the first paleointensity proxy reported from the bering sea show that characteristic paleointensity lows at 40 60 and 100 ka which have been well documented in other paleointensity records those features can be correlated to standard paleointensity curves with the aid of biogenic opal data and a radiolarian datum the mean sedimentation rates of the diatom rich cores collected in the eastern bering sea range from 10 to 20 cm kyr 1 in contrast the mean sedimentation rate of core bow 8a from the western edge of the bowers ridge is only 3 cm kyr 1 which is comparable to core es from the pelagic realm in the subarctic pacific these results suggest that biological productivity has been quite high during the late pleistocene in the eastern part of the bering sea but low over the western edge of the bowers ridge r 2005 elsevier ltd all rights reserved

joint inversion for vp vs and vp vs at safod parkfield california we refined the three dimensional 3 d vp vs and vp vs models around the san andreas fault observatory at depth safod site using a new double difference dd seismic tomography code tomoddps that simultaneously solves for earthquake locations and all three velocity models using both absolute and differential p s and s p times this new method is able to provide a more robust vp vs model than that from the original dd tomography code tomodd obtained simply by dividing vp by vs for the new inversion waveform cross correlation times for earthquakes from 2001 to 2002 were also used in addition to arrival times from earthquakes and explosions in the region the vp values extracted from the model along the safod trajectory match well with the borehole log data providing in situ confirmation of our results similar to previous tomographic studies the 3 d structure around parkfield is dominated by the velocity contrast across the san andreas fault saf in both the vp and vs models there is a clear low velocity zone as deep as 7 km along the saf trace compatible with the findings from fault zone guided waves there is a high vp vs anomaly zone on the southwest side of the saf trace that is about 1 2 km wide and extends as deep as 4 km which is interpreted to be due to fluids and fractures in the package of sedimentary rocks abutting the salinian basement rock to the southwest the relocated earthquakes align beneath the northeast edge of this high vp vs zone we carried out a 2 d correlation analysis for an existing resistivity model and the corresponding profiles through our model yielding a classification that distinguishes several major lithologies

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

global changes in intensity of the earth s magnetic field during the past 800kyr recent advances in palaeomagnetic and dating techniques have led to increasingly precise records of the relative intensity of the earth s past magnetic field at numerous field sites the compilation and analysis of these records can provide important constraints on changes in global magnetic field intensity and therefore on the earth s geodynamo itself a previous compilation for the past 200 kyr integrated 17 marine records into a composite curve1 with the geomagnetic origin of the signal supported by an independent analysis of 10be production made on different cores2 the persistence of long term features in the earth s magnetic intensity or the existence of long term periodic changes cannot however be resolved in this relatively short time span here we present the integration of 33 records of relative palaeointensity3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 into a composite curve spanning the past 800 kyr we find that the intensity of the earth s dipole field has experienced large amplitude variations over this time period with pronounced intensity minima coinciding with known excursions in field direction reflecting the emergence of non dipole components no stable periodicity was found in our composite record and therefore our data set does not support the hypothesis that the earth s orbital parameters have a direct and strong influence on the geodynamo

wisconsin holocene paleoenvironment of the bering sea evidence from diatoms pollen oxygen isotopes and clay minerals abstract a core from the southeastern bering sea contains a depositional record of the wisconsin glacial interval and the holocene four lithologic units show distinctive changes in diatom species palynomorphs oxygen isotopes in diatom silica and clay minerals unit 4 the oldest probably represents the glacial advance of the early wisconsin and records extensive sea ice cover and a soggy herbaceous tundra on the exposed continental shelf unit 3 represents the stades and interstades of the middle wisconsin including an early period of high seasonal variability and a later period with expansion of winter sea ice in the basin and of tundra onshore unit 2 represents the late wisconsin glacial maximum and subsequent deglaciation with a tundra covered shelf sea ice cover increased to a maximum during which the surface waters were probably covered by sea ice throughout the year subsequent to the sea ice maximum the isotope ratios record a major meltwater event unit 1 represents the holocene with expansion of shrub tundra or scrub forest in the coastal upland and waters of increased temperature and salinity in the bering sea

what caused the atmosphere s co2 content to rise during the last 8000 years 1 we make a case that the 20 ppm rise in atmospheric co2 content over the last 8000 years was at least in part a consequence of the 500 gt c increase in terrestrial biomass early in the present interglacial rather than of a 200 gt c decrease in terrestrial biomass during the latter part of the holocene as proposed by indermuhle et al 1999 in support of this claim we present new 13c measurements from an ontong java plateau box core which do not reproduce the trend deduced from measurements on co2 from the taylor dome ice core in attempt to distinguish between scenarios put forth to accounting for the late holocene rise in atmospheric co2 content we also made foraminifera shell weight measurements on three box cores from the ontong java plateau we were surprised to find that the early holocene caco3 preservation event we sought was strongly depth dependent the largest magnitude was at 4 km where co3 ion concentrations appear to have been 30 mol kg higher than today s and hence nearly as high as those in today s north atlantic deep water

biogenic sediments in the west caroline basin the western equatorial pacific during the last 330 000 years abstract primary productivity as well as new production have played an important role in the global carbon cycle during the late quaternary the mean organic carbon nitrogen atomic ratio was 8 3 from the c4402 sediments in the west caroline basin which indicates a limited contribution of terrigenous organic carbon to the organic matter in the sediments the fluctuation of carbonate preservation shows that the accumulation rate of organic carbon has reflected primary productivity the results from sediment trap experiments which were carried out at site c4402 indicate that plankton bloom was characterized by a large influx of siliceous plankton when organic carbon was effectively removed palaeoproductivity estimates calculated by using the formula of sarnthein et al 1988 would be plausible because the fluctuation pattern of such estimates correlates closely with changes in the accumulation rate of biogenic opal in the sediments the primary productivity in the west caroline basin increased during stage 2 stage 3 late stage 6 stage 6 7 boundary and stage 8 at a glance the results are similar to other studies that have reported higher glacial productivity in low latitude regions however some leads and lags are found between the west caroline basin and other areas of the equatorial pacific and atlantic the spectral analysis of mar organic indicates that the western equatorial pacific reaches a maximum in mar organic approximately 7000 years before the maxima in the eastern pacific a regional variation of the response of mar organic to the orbital forcing climatic condition suggests that the efficiency of the organic carbon pump may vary with longitude in the equatorial pacific

a major hydrothermal reservoir underneath the tatun volcano group of taiwan clues from a dense linear geophone array a dense linear geophone array is deployed across the tatun volcano group tvg at the northern tip of taiwan where more than 7 million residents live in the taipei metropolis the array is composed of 50 geophones with a station spacing of 200 m in average and it is designed for striking in the nw se direction to record the many earthquakes in eastern taiwan where the philippine sea plate subducted beneath the eurasia plate the detailed examination of felt earthquakes shows consistent p wave delays are recorded at particular stations of the array the further forward modeling indicates there is a low velocity zone lvz at depths between 0 5 and 2 5 km beneath the major fumarole sites combining this preliminary result with previous studies including clustering seismicity volcanic earthquakes low resistivity zone strong degassing processes and shallow velocity structures we suggest that the lvz might be associated with the major hydrothermal reservoir at the tvg the identification of the hydrothermal reservoir by the lvz not only implies a potential volcanic threat such as phreatic eruptions in the future but also provides the possibility of sustainable geothermal resources for replacing traditional nuclear and fossil fuel power plants detailed images of the lvz and other volcanic structures will be obtained soon when dense geophone arrays with more than 600 geophones are deployed from 2020 to 2022

late quaternary changes in intermediate water oxygenation and oxygen minimum zone northern japan a benthic foraminiferal perspective 1 a strong oxygen minimum zone omz currently exists at upper intermediate water depths on the northern japanese margin nw pacific the omz results largely from a combination of high surface water productivity and poor ventilation of upper intermediate waters we investigated late quaternary history last 34 kyr of ocean floor oxygenation and the omz using quantitative changes in benthic foraminiferal assemblages in three sediment cores taken from the continental slope off shimokita peninsula and tokachi northern japan at water depths between 975 and 1363 m these cores are well located within the present day omz a region of high surface water productivity and in close proximity to the source region of north pacific intermediate water late quaternary benthic foraminiferal assemblages experienced major changes in response to changes in dissolved oxygen concentration in ocean floor sediments foraminiferal assemblages are interpreted to represent three main groups representing oxic suboxic and dysoxic conditions assemblage changes in all three cores and hence in bottom water oxygenation coincided with late quaternary climatic episodes similar to that known for the southern california margin these episodes in turn are correlated with orbital and millennial climate episodes in the greenland ice core including the last glacial episode bolling allerod b a younger dryas preboreal earliest holocene early holocene and late holocene the lowest oxygen conditions marked by dysoxic taxa and laminated sediments in one core occurred during the b a and the preboreal intervals suboxic taxa dominated mainly during the last glacial the younger dryas and most of the holocene dysoxic conditions during the b a and preboreal intervals in this region were possibly caused by high surface water productivity at times of reduced intermediate ventilation in the northwestern pacific remarkable similarities are evident in the late quaternary sequence of benthic foraminiferal assemblage change between the two very distant continental margins of northern japan and southern california the oscillations in omz strength reflected by these faunal changes were widespread and apparently synchronous over wide areas of the north pacific reflecting broad changes in intermediate water ventilation and surface ocean productivity closely linked with late quaternary climate change on millennial and orbital timescales

an image of a magma intrusion process inferred from precise hypocentral migrations of the earthquake swarm east of the izu peninsula summary earthquake swarms in the area east of the izu peninsula central japan have been active and have been repeated intermittently since 1978 after 40 years of quiescence the activities were always accompanied by crustal deformations which were well modelled by dyke intrusions to study the process of a dyke intrusion precise hypocentres of the latest activity occurring in 1998 are obtained in this paper using waveform similarity by which new images of volcanic processes have been successfully acquired at several volcanoes the relocated hypocentres are mainly aligned on a thin vertical plane with a circular shape at a depth of 3 7 km and there is an aseismic area at the centre the normal direction to the plane coincides well with the direction of tectonic extensional stress around the hypocentral area and matches theoretical models well at the beginning of the activity a small fraction of the events occurred at greater depth where hypocentres align on a vertical line and migrate upward at a rate of 1 km h 1 the migration rate in this stage agrees well with a theoretical model of buoyancy driven dyke propagation after 1 day from the beginning earthquakes began to occur around the aseismic area and hypocentres spread on the thin circular plane described above during this activity the hypocentres seemed to migrate downwards and upwards from the centre the earthquakes are caused by shear fracture at the tip of the dyke and the migration of hypocentres reflects that the dyke expands downward and upward from the neutrally buoyant layer that is located at the centre of the swarm in this paper we also propose a process of magma intrusion based on the precise migration of hypocentres and show that the 1998 activity is composed of a few simple volcanic processes magma rising by buoyancy it staying at a neutral buoyancy point and spreading outward from the neutral point with elastic fracture by an inside excess magma pressure

northeastern atlantic benthic foraminifera during the last 45 000 years changes in productivity seen from the bottom up we studied benthic foraminifera from the last 45 kyr in the 63 mu m size fraction in biogeochemical ocean flux studies bofs cores 5k 50 degrees 41 3 n 21 degrees 51 9 w depth 3547 m and 14k 58 degrees 37 2 n 19 degrees 26 2 w depth 1756 m at a time resolution of several hundreds to a thousand years the deepest site showed the largest fluctuations in faunal composition species richness and benthic foraminiferal accumulation rates the fluctuations resulted from changes in abundance of epistominella exigua and alabaminella weddellensis in the present oceans these species bloom opportunistically when a spring plankton bloom results in seasonal deposition of phytodetritus on the seafloor the phytodetritus species had very low relative abundances and accumulation rates during the last glacial maximum a strong increase in absolute and relative abundance of e exigua and a weddellensis during deglaciation paralleled the decrease in abundance of the polar planktonic foraminifer neogloboquadrina pachyderma s and the increase in abundance of warmer water planktonic species such as globigerina bulloides this strong increase in relative abundance of the phytodetritus species and the coeval increase in benthic foraminiferal accumulation rate were thus probably caused by an increase in the deposition of phytodetritus to the seafloor and thus probably of surface productivity when the polar front retreated to higher latitudes the abundance of phytodetritus species decreased during the younger dryas but not to the low levels of fully glacial conditions during heinrich events periods of excessive melt water formation and ice rafting benthic accumulation rates were very low as were the absolute and relative abundances of the phytodetritus species supporting suggestions that surface productivity was very low during these events in both cores pullenia and cassidulina species were common during isotope stages 2 3 and 4 as were bolivinid buliminid and uvigerinid species high relative abundances of these species have been interpreted as indicative either of sluggish deep water circulation or of high organic carbon fluxes to the seafloor in our cores relative abundances of these species are negatively correlated with benthic foraminiferal accumulation rates and we can thus not interpret them as indicative of increased productivity during glacials the percentage of these low oxygen species calculated on a phytodetritus species free basis decreased slightly at deglaciation at 5k but not at 14k this suggests that decreased production of north atlantic deep water during the last glacial might have slightly affected benthic foraminiferal faunas in the eastern north atlantic at 3547 m depth but not at 1756 m in conclusion major changes in deep sea benthic foraminiferal faunas over the last 45 000 years in our cores from the northeastern atlantic were the result of changes in surface water productivity not of changes in deep water circulation productivity was lower during the glacial probably because of extensive ice cover

relationship between δ15n values of bulk sediments and total organic carbon concentration in response to orbital scale biogenic opal production in the bering slope area over the last 600 kyrs abstract biogenic opal production in the surface water of the bering sea shows clear orbital scale variations such as interglacial highs and glacial lows in this study we examined the variation patterns in 15 n of bulk sediment 15 n bulk reflecting nitrate utilization and total organic carbon toc concentration in terms of organic carbon oc production in response to the orbital scale biogenic opal production during the last 600 kyrs at site u1343 iodp exp 323 in the bering slope area at site u1343 15 n bulk value and toc concentration do not show the distinct glacial interglacial change moreover contrary to the weak correlation between toc and biogenic opal concentrations toc concentration is positively correlated with 15 n bulk value indicating the strong control of oc production on nitrate utilization it should be noted that glacial terminations are characterized by high 15 n bulk value high toc and low biogenic opal concentration whereas the following full interglacials are characterized by low 15 n bulk value low toc and high biogenic opal concentration during the last 600 kyrs in other words glacial terminations are characterized by complete nitrate utilization associated with high oc production under low biogenic opal production whereas the following full interglacial periods are characterized by decreased nitrate utilization associated with low oc production under high biogenic opal production such different glacial interglacial variation patterns of oc production and nitrate utilization in response to biogenic opal production can best be explained by variable si c or si n uptake ratio by diatoms possibly owing to fe availability the glacial fe input increase at site u1343 is thought to be ascribed to more dust input or large discharge from the glacial yukon river these findings imply that fe transport and contribution may play a significant role in governing the nutrient cycles in the bering slope region of the northern hemisphere

crack density and saturation rate in the 1995 kobe earthquake region we have estimated the 3 d distribution of crack density parameter and saturation rate in the 1995 kobe earthquake region by applying a crack theory to values of seismic velocity and poisson s ratio obtained from seismic tomography our results show that and exhibit considerable heterogeneity higher and exist in the kobe fault zone in particular at the mainshock hypocenter high areas are generally consistent with high areas but high areas have a much wider distribution indicating that microcracks exist in more localized areas while fluids are permeating through wider areas in the crust a significant discrepancy between and exists beneath osaka bay where is low while is high is generally high beneath seas but low beneath land areas osaka bay and the present sea land distribution in southwest japan have existed for 2 millions years this period is long enough for the sea water to permeate down to the deep crust through the active faults that would have been ruptured during many earthquakes cycles

mechanisms affecting ultrasonic wave propagation in fluid containing sandstones under high hydrostatic pressure the elastic and anelastic parameters of sandstones at ultrasonic frequencies under low uniaxial pressure are strongly influenced by the fluid content the two main mechanisms controlling the rock behavior are based on 1 local fluid flow and 2 a grain surface effect which results in a modulus reduction both mechanisms depend fundamentally on the microstructure the critical factor controlling seismic wave velocity and attenuation in rocks under low pressure ultrasonic measurements have been performed on a fluid containing sandstone under hydrostatic pressure up to 200 mpa to investigate the mechanisms affecting rock behavior under in situ pressure conditions at high hydrostatic pressure the measured p wave velocities indicate a change in the rock microstructure and in the influence of the fluid by means of two models the effects of the mechanisms of local fluid flow murphy et al 1986 and global fluid flow biot 1956a b were calculated and the loss mechanisms were compared in their capability of explaining the experimental data the experimental and theoretical results show that for the investigated fluid containing sandstone both the local fluid flow mechanism and in the case of polar fluids the modulus reduction are still effective at high external pressure

variations in the radiolarian assemblages in the bering sea since pliocene and their implications for paleoceanography radiolarian assemblages were analyzed using samples from the iodp site u1340 to reconstruct the paleoceanographic conditions in the bering sea based on the characteristic faunal changes the radiolarian evolution at site u1340 was divided into four major intervals from stages i to iv with stage iv divided into substages iva and ivb the radiolarians in each stage recorded significant paleoenvironmental conditions in general the bering sea was governed by an ocean ecological environment with stable warm and saline surface water during stage i 4 15 myr to 3 91 myr the environment in the bering sea fluctuated strongly during stage 11 3 91 myr to 2 75 myr and was controlled by the cold water masses and sea ices during stage iii 2 75 myr to 1 07 myr with the gradual development of cold and well ventilated intermediate water stage iva 1 07 myr to 0 47 myr was a transitional period characterized by the enhanced formation of cold subsurface and intermediate water as well as of the oxygen rich deep water during stage ivb after 0 47 myr the bering sea was mainly characterized by enhanced warmth during interglacial episodes and well developed water layers that were generally comparable to those of the modern bering sea these conditions indicated that the vertical water mass structure of the modern bering sea began to form since 0 47 ma every stage boundary in the studied core was marked by notable changes in the radiolarian assemblages these changes corresponded to the climatic cooling event at similar to 3 91 ma the intensification of northern hemisphere glaciation at similar to 2 75 ma the beginning of the middle pleistocene transition at similar to 1 07 ma and the low latitude radiolarian ecology event at similar to 0 47 ma in addition the relative abundance pattern of cycladophora davisiana indicates that the bering sea was the main source of the past north pacific intermediate water at ca 0 85 ma mis22 ca 0 63 ma mis16 and ca 0 18 ma mis6 just as it was during the last glacial maximum c 2014 elsevier b v all rights reserved

surface nitrate utilization in the bering sea since 180 ka bp insight from sedimentary nitrogen isotopes we present high resolution records of sedimentary nitrogen 15nbulk and carbon isotope ratios 13cbulk from piston core so201 2 85kl located in the western bering sea the records reflect changes in surface nitrate utilization and terrestrial organic matter contribution in submillennial resolution that span the last 180 kyr the 15nbulk record is characterized by a minimum during the penultimate interglacial indicating low nitrate utilization 62 80 despite the relatively high export production inferred from opal concentrations along with a significant reduction in the terrestrial organic matter fraction mterr this suggests that the consumption of the nitrate pool at our site was incomplete and even more reduced than today 84 15nbulk increases from marine isotope stage mis 5 4 and culminates during the last glacial maximum which indicates that nitrate utilization in the bering sea was raised during cold intervals mis 5 4 5 2 4 and almost complete during mis 3 and 2 93 100 this is in agreement with previous hypotheses suggesting that stronger glacial stratification reduced the nutrient supply from the subeuphotic zone thereby increasing the iron to nutrient ratio and therefore the nitrate utilization in the mixed surface layer large variations in 15nbulk were also recorded from 180 to 130 ka bp mis 6 indicating a potential link to insolation and sea level forcing and its related feedbacks millennial scale oscillations were observed in 15nbulk and 13cbulk that might be related to greenland interstadials

stable isotope and lithologic evidence of late glacial and holocene oceanography of the northwestern pacific and its marginal seas abstract stable isotopes geochemical lithological and micropaleontological results from cores from the far northwest fnw pacific and the okhotsk and bering seas are used to reconstruct the regional environment for the last glaciation the deglacial transition and the holocene 18 o records of planktonic foraminifera of the region show two light shifts during deglacial time provoked by the freshening of the surface water and climate warming these north pacific terminal events t1anp and t1bnp with ages of 12 500 and 9300 yr b p respectively occur almost simultaneously with two episodes of accelerated glacier melting around the north atlantic along with the isotopic shifts the caco 3 content in regional sediments increased abruptly 1a and 1b carbonate peaks probably due to changes of productivity and pore water chemistry of surface sediments organic matter and opal concentration increased during the transition between t1anp and t1bnp events in the sediments of the fnw pacific and the southern part of the bering sea and opal content increased in the holocene in the bering and okhotsk seas 13 c records of cores from the okhotsk and bering seas and the fnw pacific do not contradict the hypothesis of increased intermediate water formation in the region during glaciation during deglaciation accumulation of the coarse terrigenous component decreased in sediments of the bering sea and the fnw pacific before the t1anp event probably as a result of rising sea level and opening of the bering strait