stacking paleointensity and oxygen isotope data for the last 1 5 myr piso 1500 coupled relative geomagnetic paleointensity rpi and oxygen isotope records are used to construct rpi and oxygen isotope stacks for the last 1 5 myr the coupled correlations are accomplished using the match algorithm lisiecki l e and lisiecki p a 2002 application of dynamic programming to the correlation of paleoclimate records paleoceanography 17 1049 doi 10 1029 2001pa000733 to simultaneously correlate isotope and rpi records the simultaneous match reduces the degree of freedom associated with correlations using rpi or oxygen isotope records alone the overall compatibility of rpi and oxygen isotopes indicates a dominant global but independent component in both signals the local wavelet power spectrum lwps for the rpi stack indicates little significant orbital power although the accompanying oxygen isotope stack has all the lwps characteristics expected of a high resolution oxygen isotope record containing orbital frequencies the piso 1500 stack represents a new stratigraphic template that can be used to correlate among marine sediment records and link them to polar ice cores via variations in cosmogenic nuclide production scaling the stack to values for virtual axial dipole moment vadm indicate maxima at 15 1022 am2 and minima that imply a threshold of 2 5 1022 am2 below which values are associated with either polarity reversals or magnetic excursions

climate volcanism feedback and the toba eruption of 74 000 years ago abstract a general feedback between volcanism and climate at times of transition in the quaternary climate record is suggested exemplified by events accompanying the toba eruption 74 000 yr ago the largest known late quaternary explosive volcanic eruption the toba paroxysm occurred during the 18o stage 5a 4 transition a period of rapid ice growth and falling global sea level which may have been a factor in creating stresses that triggered the volcanic event toba is estimated to have produced between 1015 and 1016 g of fine ash and sulfur gases lofted in co ignimbrite ash clouds to heights of at least 32 5 km which may have led to dense stratospheric dust and sulfuric acid aerosol clouds these conditions could have created a brief dramatic cooling or volcanic winter followed by estimated annual northern hemisphere surface temperature decreases of 3 to 5 c caused by the longer lived aerosols summer temperature decreases of 10 c at high northern latitudes adjacent to regions already covered by snow and ice might have increased snow cover and sea ice extent accelerating the global cooling already in progress evidence for such climate volcanic feedback following milankovitch periodicities is found at several climatic transitions

clay minerals in late glacial and holocene sediments of the northern and southern aegean sea different source areas oceanography and climate regimes influenced the clay mineral assemblages and grain size distribution of two sediment cores from the north and south aegean sea during the last glacial and the holocene in the north aegean sea clay mineral composition is mainly controlled by sea level evolution melting of southeastern european glaciers and establishment of the connection between the black sea and aegean sea the long term development of clay mineral assemblages in the south aegean sea reflects changes in the nile discharge and african dust input at this site the establishment of pluvial conditions in the nile catchment during the early to middle holocene resulted in a substantial rise in smectite illite ratios in the late holocene stepwise aridification of the southern borderlands caused an increase in windblown sediment material and a decrease in nile suspended material the clay mineral records exhibit periodic millennial scale fluctuations in the north aegean sea the changes are centred at a period of 1 3 1 8 ka and can be attributed to short term climate and weathering changes in the northern borderlands the changes in the south aegean sea are centred at periods of 3 2 4 3 1 9 2 4 and 1 3 1 7 ka reflecting short term changes in wind strength and northeast african hydrology 2007 elsevier b v all rights reserved

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr

geomagnetic dipole strength and reversal rate over the past two million years independent records of relative magnetic palaeointensity from sediment cores in different areas of the world can be stacked together to extract the evolution of the geomagnetic dipole moment1 2 and thus provide information regarding the processes governing the geodynamo so far this procedure has been limited to the past 800 000 years 800 kyr ref 3 which does not include any geomagnetic reversals here we present a composite curve that shows the evolution of the dipole moment during the past two million years this reconstruction is in good agreement with the absolute dipole moments derived from volcanic lavas which were used for calibration we show that at least during this period the time averaged field was higher during periods without reversals but the amplitude of the short term oscillations remained the same as a consequence few intervals of very low intensity and thus fewer instabilities are expected during periods with a strong average dipole moment whereas more excursions and reversals are expected during periods of weak field intensity we also observe that the axial dipole begins to decay 60 80 kyr before reversals but rebuilds itself in the opposite direction in only a few thousand years

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

tephrochronology of the kamchatka kurile and aleutian arcs evidence for volcanic episodicity abstract volcanic ash layers in north pacific deep sea sediment provide a record of episodic explosive volcanism in the kamchatka kurile and aleutian arcs over the past five million years we counted 450 ash layers determined layer thickness and cumulative ash thickness to quantify the flux of ash with time we use this record to investigate the eruptive history of these arcs test the reliability of the marine ash record and inquire into the regional episodicity of north pacific explosive volcanic history episodes of explosive volcanism occurred at approximately 0 2 0 5 0 7 0 9 1 5 1 7 and 2 5 2 65 ma in the kamchatka arc and 0 15 0 4 1 7 1 8 2 55 2 65 and at 3 0 3 1 ma in the eastern aleutian arc these generally coeval eruptive episodes suggest that the pulses in explosive volcanism in the north pacific enumerated here and recognized by others are regionally episodic over a wide portion of the pacific rim and not just a response to local volcanogenic processes

relative paleointensity stack during the last 250 kyr in the northwest pacific 1 we have conducted a paleomagnetic study of 10 sediment cores recovered from the northwest pacific the purpose is to establish a regional paleointensity stack during the last 250 kyrs nopapis 250 for global coverage of paleointensity data as well as a regional reference for paleointensity assisted stratigraphy in the studied cores reductive dissolution of magnetite appears to have occurred mainly in glacial periods such horizons accompany large decreases in s ratio s 0 3t 1 irm 0 3t sirm 2 as low as 0 90 the sediments are also intercalated by frequent volcanic ash layers prerequisites for reliable relative paleointensity estimation are not satisfied at these horizons we rejected unsuitable data by quantitative criteria based on s ratio and saturation isothermal remanent magnetization sirm and constructed the nopapis 250 curve from the remaining data in the construction of the curve we chose irm as a normalizer because acquisitions of anhysteretic remanent magnetization arm are considered to be influenced by magnetic interactions among magnetic grains in the northwest pacific sediments relative intensity variation of the nopapis 250 gives a standard deviation that is 33 of the average if the normal distribution is assumed the nopapis 250 curve generally shows similar variation patterns compared with other high resolution records reported from other regions many paleointensity lows are recognized in common six out of the nine lows can be correlated with reported excursions in literature

magnetic hysteresis parameters and day plot analysis to characterize diagenetic alteration in gas hydrate bearing sediments 1 the j meter coercivity spectrometer is a machine capable of rapid and simple measurement of magnetic hysteresis isothermal remanence acquisition and magnetic viscosity of rocks and sediments the j meter was used to study a suite of samples collected from strata in the gas hydrate bearing japex jnoc gsc mallik 5l 38 well 69 5 n 134 6 w in the mackenzie delta of the northwestern canadian arctic the day plot of magnetic hysteresis ratios for these samples is exotic in that the points do not plot along a hyperbola as is usually observed rather they plot as a scatter which is shown to contour into vertical slices using coercivity field hc or saturation magnetization js and horizontal slices using the relative quantity of superparamagnetism jspm js optical microscopy reveals that the magnetic minerals are detrital magnetite and authigenic greigite greigite is dominant in sands which in situ had 70 gas hydrate saturation and in silts in which gas hydrate growth was blocked by insufficient porosity we infer that the silts were the accumulation sites for solutes which had been excluded from the pore waters in neighboring coarser grained sediments during the course of gas hydrate formation consequently we conclude that magnetic properties are related to gas hydrate related processes and as such may have potential as a method of remote sensing for gas hydrate deposits

pacific offshore record of plinian arc volcanism in central america 2 tephra volumes and erupted masses 1 sediment gravity cores collected from the pacific seafloor offshore central america contain numerous distal ash layers from plinian type eruptions at the central american volcanic arc dating back to more than 200 ka in part 1 of this contribution we have correlated many of those ash layers between cores and with 26 tephras on land the marine ash layers cover areas of up to 106 km2 in the pacific ocean and represent a major fraction 60 90 of the erupted tephra volumes because the pacific coast lies within a few tens of kilometers downwind from the volcanic arc combining our own mapping efforts on land and published mapping results with our marine data yields erupted volumes of all major tephras along the arc that range from 1 to 420 km3 recalculated to erupted magma mass the widespread tephras account for 65 of the total magma output at the arc complementing our tephra data with published volumes of the arc volcanic edifices and volcano ages we calculate the long term average magma eruption rates for each volcano moreover we use incompatible element variations to calculate the cumulate masses that were fractionated during variable degrees of differentiation this yields a minimum estimate of long term average magma production rate at each volcano because intrusives without surface expression and losses by erosion are not accounted for peak magma production rates increase from costa rica to guatemala but there is considerable scatter within each region and large differences even between neighboring volcanoes

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

sedimentation processes in the eastern mediterranean sea during the late glacial and holocene revealed by end member modelling of the terrigenous fraction in marine sediments we present grain size distributions of the terrigenous fraction of two sediment cores from the southeast levantine sea sl112 and the northern aegean sea sl148 spanning the time interval from the late glacial to the present end member modelling of the grain size distribution allows discriminating between aeolian and fluvial transport of the sediments and helps to infer palaeoenvironmental conditions in the source areas sedimentary and depositional processes during the late glacial and holocene were controlled by climatic variations of both the northern high latitudes and the african climate system the sedimentation at site sl112 off israel is dominated by the suspension load of the river nile and aeolian dust from the sahara variations in grain size reflect the early to mid holocene climate transition from the african humid period to recent arid conditions this climate change was gradual in contrast to the abrupt humidity change documented in western saharan records this implies a successive decrease in nile river sediment supply due to a step wise aridification of the headwaters the grain size data of sl112 show a humidity maximum at 5 kyr bp coincident with a regionally restricted wet phase in the levantine sea the sediments at the north aegean site sl148 consist of riverine particles and low amounts of aeolian dust probably derived from south european sources and with probably minor saharan influence the sedimentation processes are controlled by climate conditions being characterized by enhanced deposition of dust during the cold and dry glacial period and by decreased aeolian influx during the temperate and humid holocene

orbital and millennium scale environmental changes in the southern bering sea during the last glacial holocene geochemical and paleontological evidence the d 18 o benthic foraminiferal curve and ams 14 c radiocarbon data provide a representative age model for a southern bering sea sediment core gc 11 downcore profiles of d 18 oo fn pachyderma s and u auberiana carbonate and organic carbon contents species changes in the planktonic foraminifera assemblages and some diatom species show orbital mis 1 2 and 3 and millennium scale variability influenced by the alaska current flowing into the studied region three warmer episodes in the southern bering sea environment were assumed to be synchronous with do interstadials 8 12 and 14 in gisp 2 chronology during mis 3 more severe climate and environmental conditions in the southern bering sea during mis 2 occurred synchronously with the lgm within a 17 19 ka time span two well pronounced environmental warming events productivity spikes and changes in the pore water geochemistry separated by younger dryas cooling were observed at the base of mis 1 coeval with mwp 1a and 1b regional glacial primary productivity based on the calculation of the organic carbon mar similar to that found in the far northwestern pacific exceeded the late holocene values under conditions close to the present day r 2005 elsevier ltd all rights reserved

climate response to the samalas volcanic eruption in 1257 revealed by proxy records the eruption of samalas in indonesia in 1257 ranks among the largest sulfur rich eruptions of the common era with sulfur deposition in ice cores reaching twice the volume of the tambora eruption in 1815 sedimentological analyses of deposits confirm the exceptional size of the event which had both an eruption magnitude and a volcanic explosivity index of 7 during the samalas eruption more than 40 km 3 of dense magma was expelled and the eruption column is estimated to have reached altitudes of 43 km however the climatic response to the samalas event is debated since climate model simulations generally predict a stronger and more prolonged surface air cooling of northern hemisphere summers than inferred from tree ring based temperature reconstructions here we draw on historical archives ice core data and tree ring records to reconstruct the spatial and temporal climate response to the samalas eruption we find that 1258 and 1259 experienced some of the coldest northern hemisphere summers of the past millennium however cooling across the northern hemisphere was spatially heterogeneous western europe siberia and japan experienced strong cooling coinciding with warmer than average conditions over alaska and northern canada we suggest that in north america volcanic radiative forcing was modulated by a positive phase of the el nino southern oscillation contemporary records attest to severe famines in england and japan but these began prior to the eruption we conclude that the samalas eruption aggravated existing crises but did not trigger the famines

geomagnetic moment variation and paleomagnetic excursions since 400 kyr bp a stacked record from sedimentary sequences of the portuguese margin abstract a paleomagnetic study was performed in clayey carbonate sedimentary sequences deposited during the last 400 kyr on the portuguese margin northeast atlantic ocean declination and inclination of the stable remanent magnetization present recurrent deviations from the mean geomagnetic field direction the normalized intensity documents a series of relative paleointensity rpi lows recognized in other reference records three directional anomalies occurring during rpi lows chronologically correspond to the laschamp excursion 42 kyr bp the blake event 115 122 kyr bp and the icelandic basin excursion 190 kyr bp a fourth directional anomaly recorded at 290 kyr bp during another rpi low defines the portuguese margin excursion four non excursional rpi lows are recorded at the ages of the jamaica pringle falls mamaku calabrian ridge 1 and levantine excursions the rpi record is characterized by a periodicity of 100 kyr paleointensity lows often coinciding with the end of interglacial stages this record sets the basis of the construction of an authigenic 10be 9be record from the same sedimentary sequences carcaillet et al this issue

a summary of brunhes paleomagnetic field variability recorded in ocean drilling program cores the ocean drilling program odp has recovered many long sediment sequences from around the world that contain medium to high resolution paleomagnetic records of brunhes age these records have provided an important new global view of geomagnetic field variability during stable magnetic dipole polarity that could not be recovered by conventional terrestrial or deep sea piston coring the odp paleomagnetic records of directional variability can be routinely recovered and used regionally as a very highresolution relative chronostratigraphic tool 200 yr resolution odp paleomagnetic records of brunhes age relative paleointensity have dramatically improved our understanding of global geomagnetic field intensity these records document the global scale pattern of paleointensity and demonstrate its use as a high resolution relative chronostratigraphic tool that under ideal conditions could have a precision of 500 yr odp paleomagnetic records and associated oxygen isotope chronostratigraphies have also greatly improved our understanding of the number and ages of brunhes geomagnetic field excursions and their relationship to normal directional secular variation and paleointensity variability although significant progress has been made though odp paleomagnetic studies of brunhes aged sediments it is clear that more work is needed to further resolve and define the detailed global pattern of brunhes psv and its relationship to excursions and true polarity reversals

the 7600 14c year bp kurile lake caldera forming eruption kamchatka russia stratigraphy and field relationships abstract the 7600 14 c year old kurile lake caldera forming eruption ko in southern kamchatka russia produced a 7 km wide caldera now mostly filled by the kurile lake the ko eruption has a conservatively estimated tephra volume of 140 170 km 3 making it the largest holocene eruption in the kurile kamchatka volcanic arc and ranking it among the earth s largest holocene explosive eruptions the eruptive sequence consists of three main units i initial phreatoplinian deposits ii plinian fall deposits and iii a voluminous and extensive ignimbrite sheet and accompanying surge beds and co ignimbrite fallout the ko fall tephra was dispersed over an area of 3 million km 2 mostly in a northwest direction it is a valuable stratigraphic marker for southern kamchatka the sea of okhotsk and a large part of the asia mainland where it has been identified as a 6 to 0 1 cm thick layer in terrestrial and lake sediments 1000 1700 km from source the ignimbrite which constitutes a significant volume of the ko deposits extends to the sea of okhotsk and the pacific ocean on either side of the peninsula a distance of over 50 km from source fine co ignimbrite ash was likely formed when the ignimbrite entered the sea and could account for the wide dispersal of the ko fall unit individual pumice clasts from the fall and surge deposits range from dacite to rhyolite whereas pumice and scoria clasts in the ignimbrite range from basaltic andesite to rhyolite ignimbrite exposed west and south of the caldera is dominantly rhyolite whereas north east and southeast of the caldera it has a strong vertical compositional zonation from rhyolite at the base to basaltic andesite in the middle and back to rhyolite at the top following the ko eruption iliinsky volcano formed within the northeastern part of the caldera producing basalt to dacite lavas and pyroclastic rocks compositionally related to the ko erupted products other post caldera features include several extrusive domes which form islands in kurile lake submerged cinder cones and the huge silicic extrusive massif of dikii greben volcano

onshore offshore correlation of pleistocene rhyolitic eruptions from new zealand implications for tvz eruptive history and paleoenvironmental construction abstract taupo volcanic zone tvz in the north island new zealand is arguably the most active quaternary rhyolitic system in the world numerous and widespread rhyolitic tephra layers sourced from the tvz form valuable chronostratigraphic markers in onshore and offshore sedimentary sequences in deep sea cores from ocean drilling program odp leg 181 sites 1125 1124 1123 and 1122 located east of new zealand ca 100 tephra beds are recognised post dating the plio pleistocene boundary at 1 81 ma these tephras have been dated by a combination of magnetostratigraphy orbitally tuned stable isotope data and isothermal plateau fission track ages the widespread occurrence of ash offshore to the east of new zealand is favoured by the small size of new zealand the explosivity of the mainly plinian and ignimbritic eruptions and the prevailing westerly wind field although some tephras can be directly attributed to known tvz eruptions there are many more tephras represented within odp cores that have yet to be recognised in near source on land sequences this is due to proximal source area erosion and or deep burial as well as the adverse effect of vapour phase alteration and devitrification within near source welded ignimbrites despite these difficulties a number of key deep sea tephras can be reliably correlated to equivalent aged tephra exposed in uplifted marine back arc successions of wanganui basin where an excellent chronology has been developed based on magnetostratigraphy orbitally calibrated sedimentary cycles and isothermal plateau fission track ages on tephra significant pleistocene tephra markers include the kawakawa omataroa rangitawa onepuhi kaukatea kidnappers b potaka unit d ahuroa ongatiti rewa sub rewa pakihikura ototoka and table flat tephras six other tephra layers are correlated between odp core sites but have yet to be recognised within onshore records the identification of pleistocene tvz sourced tephras within the odp record and their correlation to wanganui basin and other onshore sites is a significant advance as it provides 1 an even more detailed history of the tvz than can be currently achieved from the near source record 2 a high resolution tephrochronologic framework for future onshore offshore paleoenvironmental reconstructions and 3 well dated tephra beds correlated from the offshore odp sites with astronomically tuned timescales provide an opportunity to critically evaluate the chronostratigraphic framework for onshore plio pleistocene sedimentary sequences e g wanganui basin cf naish et al 1998 quaternary science reviews 17 695 710

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

tephrochronology and the extended intimate integration of ice core marine and terrestrial records event stratigraphy 8 128 ka b2k the comparison of palaeoclimate records on their own independent timescales is central to the work of the intimate integrating ice core marine and terrestrial records network for the north atlantic region an event stratigraphy has been established from the high precision greenland ice core records and the integrated gicc05 chronology this stratotype provides a palaeoclimate signal to which the timing and nature of palaeoenvironmental change recorded in marine and terrestrial archives can be compared to facilitate this wider comparison without assuming synchroneity of climatic change proxy response intimate has also focussed on the development of tools to achieve this in particular the use of time parallel marker horizons e g tephra layers volcanic ash coupled with the recent temporal extension of the greenland stratotype as part of this special issue we present an updated intimate event stratigraphy highlighting key tephra horizons used for correlation across europe and the north atlantic we discuss the advantages of such an approach and the key challenges for the further integration of terrestrial palaeoenvironmental records with those from ice cores and the marine realm

the avaatech xrf core scanner technical description and applications to ne atlantic sediments abstract x ray fluorescence xrf core scanning provides rapid high resolution down to 1 mm records of chemical composition on split sediment cores the measurements are non destructive and require very limited sample preparation the new avaatech xrf core scanner operational since 2002 covers the atomic mass range from al to u instrument parameters especially tube voltage can be adjusted to provide optimum settings for selected elements or sets thereof owing to the nature of the surface of split sediment cores particularly effects resulting from sample inhomogeneity and surface roughness results are semiquantitative yet provide reliable records of the relative variability in elemental composition downcore selected case studies from diverse sedimentary settings in the ne atlantic ocean illustrate a range of applications of xrf logging data these include preliminary stratigraphic interpretations glacial interglacial cycles provenance studies of the terrigenous sediment fraction lithological characterization early diagenetic processes and distinction between carbonate phases aragonite v calcite

environmental change in the sea of okhotsk during the last 1 1 million years on the basis of two sedimentary records from the central sea of okhotsk we reconstruct the closely coupled glacial interglacial changes in terrigenous flux marine productivity and sea ice coverage over the past 1 1 myr the correspondance of our sedimentary records to the china loess grain size record china loess particle timescale chiloparts suggests that environmental changes in both the sea of okhotsk area and in se asia were closely related via the siberian atmospheric high pressure cell during full glacial times our records point to a strong siberian high causing northerly wind directions the extension of the sea ice cover and a reduced amur river discharge deglacial maxima of terrigenous flux were succeeded by or synchronous to high productivity events marine productivity was strengthened during glacial terminations because of an effective nutrient utilization at times of enhanced water column stratification and high nutrient supply from fluvial runoff and sea ice thawing during interglacials se monsoonal winds prevailed analogous to today s summer situation of a pronounced mongolian heat low and a strong hawaiian high strong freshwater discharge induced by high precipitation rates in the amur drainage area and a seasonally reduced and mobile sea ice cover favored marine productivity although being considerably lower than during the terminations and a lowered flux of ice rafted detritus

eruptive history of karymsky volcano kamchatka ussr based on tephra stratigraphy and 14c dating eruptions of the active karymsky stratovolcano began about 5300 6100 14c b p from within a pre existing caldera which formed 7700 14c b p as indicated by 32 14c determinations on buried soils and charcoal the volcano has gone through two major cycles of activity separated by a 2300 year period of repose the first cycle can be divided into two stages 6100 5100 and 4300 2800 b p the earlier stage began with especially intense eruptions of basaltic andesite to dacite the later stage was characterized by moderate strength eruptions of andesite the second cycle which is characterized by weak to moderate intermittent eruptions of andesite started 500 b p and continues to the present eruptive patterns suggest that this cycle may continue for at least another 200 years with an eruptive character similar to that of the recent past

a full holocene tephrochronology for the kamchatsky peninsula region applications from kamchatka to north america abstract geochemically fingerprinted widespread tephra layers serve as excellent marker horizons which can directly link and synchronize disparate sedimentary archives and be used for dating various deposits related to climate shifts faulting events tsunami and human occupation in addition tephras represent records of explosive volcanic activity and permit assessment of regional ashfall hazard in this paper we report a detailed holocene tephrochronological model developed for the kamchatsky peninsula region of eastern kamchatka nw pacific based on 2800 new electron microprobe analyses of single glass shards from tephra samples collected in the area as well as on previously published data tephra ages are modeled based on a compilation of 223 14c dates including published dates for shiveluch proximal tephra sequence and regional marker tephras new ams 14c dates and modeled calibrated ages from the krutoberegovo key site the main source volcanoes for tephra in the region are shiveluch and kliuchevskoi located 60 100 km to the west in addition local tephra sequences contain two tephras from the plosky volcanic massif and three regional marker tephras from ksudach and avachinsky volcanoes located in the eastern volcanic front of kamchatka this tephrochronological framework contributes to the combined history of environmental change tectonic events and volcanic impact in the study area and farther afield this study is another step in the construction of the kamchatka wide holocene tephrochronological framework under the same methodological umbrella our dataset provides a research reference for tephra and cryptotephra studies in the northwest pacific the bering sea and north america

paleonutrient and productivity records from the subarctic north pacific for pleistocene glacial terminations i to v our study addresses fundamental questions of the mode and timing of orbital and millennial scale changes in the meridional overturning circulation moc of the subarctic north pacific particular concerns are the vertical mixing the present and past abundance of nutrients in surface waters despite strong stratification and the north pacific north atlantic seesaw of oscillations in sea surface temperature sst we do this by generating and interpreting multiple records for glacial terminations i v down two long piston cores one each from the western and eastern subarctic pacific chlorins and biogenic opal are proxies for surface water productivity delta 13 c of epibenthic foraminifera is a record of deepwater ventilation and the delta 13 c of n pachyderma sin is a tracer of nutrients in subsurface waters that extend up to the sea surface during times of vertical mixing the degree of mixing is traced by pairing sst and delta 18 o records of planktic surface and subsurface pycnocline dwellers tight age control is deduced from a suite of age calibrated 14 c plateau boundaries for termination i and benthic delta 18 o and geomagnetic events for the last 800 ka carbon 14 paleoreservoir ages record the ages of surface and deep waters to uncover short term changes in moc over termination i we have defined a standard sequence of short term productivity events for termination i also evident during terminations ii to v and subsequent interglacials over the last 450 ka the peak glacial regime of stable stratification and low productivity terminated together with the end of ice rafting and melting near 17 ka similar to 2000 years after the onset of termination i pulses of vertical mixing and incursion of warm surface waters from the subtropics followed convected young water masses finally penetrated down to 3600 m water depth at 17 0 to less than 14 5 ka significantly improving bottom water ventilation through the late deglacial and earliest interglacial mixing with upwelled nutrients from the pycnocline induced short term maxima in algal production of chlorins and biogenic opal near 17 15 and 15 12 ka respectively deglacial meltwater incursions in the aleutian current and silica input from north american rivers also promoted east pacific productivity after 15 5 ka productivity decreased during the late deglacial and early interglacial coeval with an exceptional peak in caco 3 preservation caused by both low organic flux and well ventilated deepwater subsequently low salinity and cool surface waters and in turn stratification were gradually restored a second opal dominated productivity maximum marked the ends of interglacials the deglacial pulses of vertical mixing around 17 11 ka imply an important contribution of the north pacific to the coeval release of oceanic co 2 into the atmosphere and support the east west seesaw model of climate change

the 20 january 2007 ml 4 8 odaesan earthquake and its implications for regional tectonics in korea a moderate sized earthquake m l 4 8 occurred in the mideast korea peninsula on 20 january 2007 it was the largest inland earthquake to occur there since the inception of a modern seismic observation system although only four aftershocks were noticed in previous studies a careful review of continuous data revealed that the main event was accompanied by at least 74 micro foreshocks and aftershocks a subset of 25 events was selected for further analysis to determine precise earthquake locations focal mechanism solutions and the current status of regional tectonic stress as well as to answer questions raised about the sequence earthquake hypocenters were seen to be more clustered after the hypodd relocation a source radius of 1 km for the main event was estimated based on the distribution of precisely determined aftershock locations focal mechanism solutions of larger events in the sequence suggest either a left lateral strike slip fault trending west northwest east southeast or a right lateral strike slip fault trending north northeast south southwest as the responsible structure although the woljeongsa fault striking north northeast south southwest in the local geological map matches one of the proposed trends precise earthquake relocation results gave a contradictory result showing that a previously unknown west northwest east southeast striking fault was responsible for the earthquake sequence we also observed an unusual lack of large magnitude aftershocks a relatively large stress drop during the main event and no previous earthquake record in the region observations made in the study consistently indicate the sequence nucleated along a less developed fault focal mechanism solutions suggest the current status of tectonic stress governing earthquake generation in korea is east northeast west southwest compression and north northwest south southeast extension

tephra from andesitic shiveluch volcano kamchatka nw pacific chronology of explosive eruptions and geochemical fingerprinting of volcanic glass the 16 ka long record of explosive eruptions from shiveluch volcano kamchatka nw pacific is refined using geochemical fingerprinting of tephra and radiocarbon ages volcanic glass from 77 prominent holocene tephras and four late glacial tephra packages was analyzed by electron microprobe eruption ages were estimated using 113 radiocarbon dates for proximal tephra sequence these radiocarbon dates were combined with 76 dates for regional kamchatka marker tephra layers into a single bayesian framework taking into account the stratigraphic ordering within and between the sites as a result we report 1 700 high quality glass analyses from late glacial holocene shiveluch eruptions of known ages these define the magmatic evolution of the volcano and provide a reference for correlations with distal fall deposits shiveluch tephras represent two major types of magmas which have been feeding the volcano during the late glacial holocene time baidarny basaltic andesites and young shiveluch andesites baidarny tephras erupted mostly during the late glacial time 16 12 8 ka bp but persisted into the holocene as subordinate admixture to the prevailing young shiveluch andesitic tephras 12 7 ka bp present baidarny basaltic andesite tephras have trachyandesite and trachydacite sio2 71 5 wt strongly calc alkaline medium k characteristics of shiveluch volcanic glasses along with moderate cl cao and low p2o5 contents permit reliable discrimination of shiveluch tephras from the majority of other large holocene tephras of kamchatka the young shiveluch glasses exhibit wave like variations in sio2 contents through time that may reflect alternating periods of high and low frequency volume of magma supply to deep magma reservoirs beneath the volcano the compositional variability of shiveluch glass allows geochemical fingerprinting of individual shiveluch tephra layers which along with age estimates facilitates their use as a dating tool in paleovolcanological paleoseismological paleoenvironmental and archeological studies electronic tables accompanying this work offer a tool for statistical correlation of unknown tephras with proximal shiveluch units taking into account sectors of actual tephra dispersal eruption size and expected age several examples illustrate the effectiveness of the new database the data are used to assign a few previously enigmatic wide spread tephras to particular shiveluch eruptions our finding of shiveluch tephras in sediment cores in the bering sea at a distance of 600 km from the source permits re assessment of the maximum dispersal distances for shiveluch tephras and provides links between terrestrial and marine paleoenvironmental records

the behaviour of platinum group elements in basalts from the east greenland rifted margin the continental flood basalts of the east greenland volcanic rifted margin were extruded during continental breakup above the ancestral iceland mantle plume at 55 ma three distinct magma types the low ti high ti and very high ti series lts hts and vhts respectively are found intercalated in the 6 km thick plateau lava sequence incompatible trace elements indicate that the lts are derived from a more depleted mantle source compared to hts and vhts the lts is characterised by increasing cu 105 to 248 ppm and pd 7 to 24 ppb constant cu pd ratio 10 000 and decreasing ir 1 1 to 0 05 ppb and ru 1 8 to 0 3 ppb concentrations during magmatic differentiation 16 to 7 wt mgo the constant cu pd ratio reflects silicate and chromite dominated fractionation without concurrent segregation of sulphide s undersaturated differentiation is also indicated in the hts which also displays increasing pd 6 16 ppb and decreasing ir concentrations 1 to 0 05 ppb during differentiation and the cu pd ratios for the entire series average 21 000 however some hts samples have elevated cu pd ratios up to 33 000 cu pd ratios in the hts do not correlate with mgo and this is interpreted to reflect varying cu pd ratios of hts parental magmas rather than s saturated differentiation during s undersaturated differentiation of the lts and hts pt pd ratios decrease from 1 3 to 0 11 and 1 1 to 0 2 respectively which indicates that pd is much more incompatible than pt during s undersaturated differentiation the vhts consists exclusively of highly evolved samples with low mgo 6 6 6 1 wt and pd ir ratios 98 228 here cu pd ratios increase from 17 500 to 35 000 with decreasing cr concentrations which indicate that these magmas experienced silicate fractionation with concurrent segregation of sulphide the lts represent melting of a depleted source and show high pge concentrations and constant cu pd ratios during s undersaturated differentiation melting of a normal depleted upper mantle source generates s saturated melts morb and the depleted lts source is therefore considered an extraordinary s poor component within the ancestral iceland plume of the three series the vhts contain the largest contribution from enriched mantle portions the vhts have similar pge but much higher nb concentrations for instance compared to the most evolved lts and hts samples indicating that the enriched source contributes nb but not pge

old crow tephra across eastern beringia a single cataclysmic eruption at the close of marine isotope stage 6 abstract old crow tephra is the largest and most widespread quaternary eruption presently known in eastern beringia its major and trace element geochemistry fe ti oxides and stratigraphic and paleoecological context indicate that it is the result of a single cataclysmic eruption the proximal region may well have experienced tephra fallout from small eruptions just prior to or after the old crow event but there is no evidence to indicate that the distal area was affected we recalculate the glass fission track age at 124 10 ka which coupled with stratigraphic and paleoenvironmental reconstructions indicates that deposition occurred prior to development of the last interglacial boreal forest which suggests a latest marine isotope stage mis 6 age the bulk tephra volume erupted is estimated by three different approaches that are in broad agreement at 200 km 3 but this result must be considered as tentative given the poor controls on definition of isopachs over such a large area the source caldera although presently unrecognized is located in the eastern aleutian arc possibly at or near the emmons lake volcanic center

ages of calderas large explosive craters and active volcanoes in the kuril kamchatka region russia the ages of most of calderas large explosive craters and active volcanoes in the kuril kamchatka region have been determined by extensive geological geomorphological tephrochronological and isotopic geochronological studies including more than 600 14c dates eight krakatoa type and three hawaiian type calderas and no less than three large explosive craters formed here during the holocene most of the late pleistocene krakatoa type calderas were established around 30 000 40 000 years ago the active volcanoes are geologically very young with maximum ages of about 40 000 50 000 years the overwhelming majority of recently active volcanic cones originated at the very end of the late pleistocene or in the holocene these studies show that all holocene stratovolcanoes in kamchatka were emplaced in the holocene only in the eastern volcanic belt periods of synchronous intensified holocene volcanic activity occurred within the time intervals of 7500 7800 and 1300 1800 14c years bp

tephra layers of in the quaternary deposits of the sea of okhotsk distribution composition age and volcanic sources the fullest summary on composition age and distribution of 23 tephra layers detected and investigated in the okhotsk sea pleistocene holocene deposits is presented seven tephra layers are surely identified with powerful explosive eruptions of volcanoes of kamchatka kurile and japanese islands for them the areas of ash falls including which weren t revealed earlier on the land are specified and established it is estimated that explosive eruptions of volcanoes of the kamchatka sredinny range were the sources for three tephra layers complex investigations of morphological mineralogical and chemical composition of tephras including composition of rare and earth rare elements electron microprobe analysis and laser ablation method la icp ms have been made for all studied layers they were a basis for tephrostratigraphic correlation of the regional deposits promoting to specification of stages of volcanic explosive activity in this region

late pleistocene and holocene tephrostratigraphy of interior alaska and yukon key beds and chronologies over the past 30 000 years abstract the aleutian arc alaska peninsula and wrangell volcanic field are the main source areas for tephra deposits found across alaska and northern canada and increasingly tephra from these eruptions have been found further afield in north america greenland and europe however there have been no broad scale reviews of the late pleistocene and holocene tephrostratigraphy for this region since the 1980s and this lack of data is hindering progress in identifying these tephra both locally and regionally to address this gap and the variable quality of associated geochemical and chronological data we undertake a detailed review of the latest pleistocene to holocene tephra found in interior alaska and yukon this paper discusses nineteen tephra that have distributions beyond southwest alaska and that have the potential to become or already are important regional markers this includes three modern events from the 20th century ten with limited data availability but potentially broad distributions and six that are widely reported in interior alaska and yukon each tephra is assessed in terms of chronology geochemistry and distribution with new bayesian age estimates and geochemical data when possible this includes new major element geochemical data for crater peak 1992 redoubt 1989 90 and two andesitic tephra from st michael island tephra d as well as revised age estimates for dawson tephra oshetna hayes set h aniakchak cfe ii and the white river ashes northern and eastern lobes

holocene key marker tephra layers in kamchatka russia detailed tephrochronological studies in kamchatka peninsula russia permitted documentation of 24 holocene key marker tephra layers related to the largest explosive eruptions from 11 volcanic centers each layer was traced for tens to hundreds of kilometers away from the source volcano its stratigraphic position area of dispersal age characteristic features of grain size distribution and chemical and mineral composition confirmed its identification the most important marker tephra horizons covering a large part of the peninsula are from north to south ages given in14c yr b p sh2 1000 yr b p and sh3 1400 yr b p from shiveluch volcano kz 7500 yr b p from kizimen volcano krm 7900 yr b p from karymsky caldera khg 7000 yr b p from khangar volcano av1 3500 yr b p av2 4000 yr b p av4 5500 yr b p and av5 5600 yr b p from avachinsky volcano op 1500 yr b p from the baraniy amfiteatr crater at opala volcano khd 2800 yr b p from the maar at khodutka volcano ks1 1800 yr b p and ks2 6000 yr b p from the ksudach calderas ksht3 a d 1907 from shtyubel cone in ksudach volcanic massif and ko 7700 yr b p from the kuril lake iliinsky caldera tephra layers sh5 2600 yr b p from shiveluch volcano av3 4500 yr b p from avachinsky volcano optr 4600 yr b p from opala volcano ks3 6100 yr b p and ks4 8800 yr b p from ksudach calderas ksht1 1100 yr b p from shtyubel cone and zlt 4600 yr b p from iliinsky volcano cover smaller areas and have local stratigraphic value as do the ash layers from the historically recorded eruptions of shiveluch sh1964 and bezymianny b1956 volcanoes the dated tephra layers provide a record of the most voluminous explosive events in kamchatka during the holocene and form a tephrochronological timescale for dating and correlating various deposits