detailed tephrochronology and composition of major holocene eruptions from avachinsky kozelsky and koryaksky volcanoes in kamchatka abstract avachinsky kozelsky and koryaksky volcanoes form one of the most volcanically active clusters in the kamchatka volcanic arc and are located in close proximity of the cities of petropavlovsk kamchatsky and elizovo the most populated area in kamchatka in this paper we report a compilation of new and revised previously published data on the eruptive history of these volcanoes during the past 13 5 kyrs we identify 217 explosive eruptions of these volcanoes determine their ages using 207 radiocarbon dates and bayesian statistical modeling and characterize their tephra geochemically using major and trace element compositions of bulk samples 40 samples and volcanic glass 75 samples avachinsky has been the most active during the holocene time and had 150 explosive eruptions koryaksky produced 60 eruptions and kozelsky had only two eruptions in the early holocene our new data confirm the onset of the avachinsky postglacial activity at 11 3 cal ka bp and previously distinguished two major stages of avachinsky holocene eruptive history stage i 8 3 8 cal ka bp and stage ii 3 8 cal ka bp present during stage i eruptions were relatively rare but they included at least six large pumice eruptions with tephra volumes exceeding 0 5 km3 stage i tephras had low k andesitic bulk compositions and low k rhyolitic matrix glasses the andesites likely sampled volatile rich crystal mush from a long lived magma chamber under avachinsky volcano the stage ii started at 3 8 cal ka bp with a powerful eruption and was related to the construction of the young cone inside the avachinsky somma the subsequent late holocene eruptions were frequent but most of them did not exceed the volume of 0 3 km3 the stage ii tephras are mostly cindery basaltic andesites containing well crystallized groundmasses of andesitic composition these tephras originate from smaller perhaps more shallow magmatic reservoirs and their matrix glasses are likely products of in situ crystallization of relatively mafic magmas on their ascent to the surface koryaksky volcano was mostly active in the early holocene when avachinsky was quiet koryaksky tephras had a relatively constant bulk medium k andesitic composition during the holocene thanks to characteristic compositions high frequency and well constrained ages tephras of avachinsky and koryaksky volcanoes can be used for high resolution dating of local sediments some eruptions of avachinsky volcano reached volcanic explosivity index vei 5 and produced widely dispersed tephras these eruptions could have had global environmental effects and their tephras can be used for the correlation of disparate sedimentary archives some avachinsky and koryaksky eruptions were closely spaced in time however their tephras are easily distinguished by respective low k and medium k compositions and by different trace element patterns which imply compositionally different sources in the mantle wedge we interpret these differences to reflect the increasing slab surface temperature and transition of slab component from a relatively low temperature fluid like phase under avachinsky to more high temperature and solute rich supercritical fluid or melt under koryaksky the transition appears to be very sharp in kamchatka causing a large compositional shift in magmas just behind the volcanic front

holocene tsunamis in the southwestern bering sea russian far east and their tectonic implications the bering sea coast of kamchatka overlies a boundary between the proposed okhotsk and bering blocks or micro plates of the north american plate in the russian far east a history of tsunamis along this coast for the past 4000 yr indicates that the zone north of the kuril kamchatka subduction zone produces tsunamigenic earthquakes every few centuries such a record is consistent with convergence of the proposed okhotsk and bering blocks along the bering sea coast of kamchatka a tsunami deposit from the 1969 m w 7 7 ozernoi earthquake helps us interpret older tsunami deposits newly studied tephra layers from shiveluch volcano as well as previously established marker tephra layers in northern kamchatka provide age control for historic and prehistoric tsunami deposits based on 50 measured sections along 14 shoreline profiles tsunami deposit frequencies in the southwestern bering sea are about five per thousand years for tsunamis generated north of the kuril kamchatka trench

the caldera forming eruption of ksudach volcano about cal a d 240 the greatest explosive event of our era in kamchatka russia the largest plinian eruption of our era and the latest caldera forming eruption in the kuril kamchatka region occurred about cal a d 240 from the ksudach volcano this catastrophic explosive eruption was similar in type and characteristics to the 1883 krakatau event the volume of material ejected was 18 19 km3 8 km3 dre including 15 km3 of tephra fall and 3 4 km3 of pyroclastic flows the estimated height of eruptive column is 22 30 km a collapse caldera resulting from this eruption was 4 6 5 km in size with a cavity volume of 6 5 7 km3 tephra fall was deposited to the north of the volcano and reached more than 1000 km pyroclastic flows accompanied by ash cloud pyroclastic surges extended out to 20 km the eruption was initially phreatomagmatic and then became rhythmic with each pulse evolving from pumice falls to pyroclastic flows erupted products were dominantly rhyodacite throughout the eruption during the post caldera stage when the shtyubel cone started to form within the caldera basaltic andesite and andesite magma began to effuse the trigger for the eruption may have been an intrusion of mafic magma into the rhyodacite reservoir the eruption had substantial environmental impact and may have produced a large acidity peak in the greenland ice sheet

zonally asymmetric response of the southern ocean mixed layer depth to the southern annular mode interactions between the atmosphere and ocean are mediated by the mixed layer at the ocean surface the depth of this layer is determined by wind forcing and heating from the atmosphere variations in mixed layer depth affect the rate of exchange between the atmosphere and deeper ocean the capacity of the ocean to store heat and carbon and the availability of light and nutrients to support the growth of phytoplankton however the response of the southern ocean mixed layer to changes in the atmosphere is not well known here we analyse temperature and salinity data from argo profiling floats to show that the southern annular mode sam the dominant mode of atmospheric variability in the southern hemisphere leads to large scale anomalies in mixed layer depth that are zonally asymmetric from a simple heat budget of the mixed layer we conclude that meridional winds associated with departures of the sam from zonal symmetry cause anomalies in heat flux that can in turn explain the observed changes of mixed layer depth and sea surface temperature our results suggest that changes in the sam including recent and projected trends attributed to human activity drive variations in southern ocean mixed layer depth with consequences for air sea exchange ocean sequestration of heat and carbon and biological productivity

tephrochronological dating of paleoearthquakes in active volcanic arcs a case of the eastern volcanic front on the kamchatka peninsula northwest pacific

do peatlands or lakes provide the most comprehensive distal tephra records abstract despite the widespread application of tephra studies for dating and correlation of stratigraphic sequences tephrochronology questions remain over the reliability and replicability of tephra records from lake sediments and peats particularly in sites 1000 km from source volcanoes to address this we examine the tephrostratigraphy of four pairs of lake and peatland sites in close proximity to one another

towards a climate event stratigraphy for new zealand over the past 30 000 years nz intimate project it is widely recognised that the acquisition of high resolution palaeoclimate records from southern mid latitude sites is essential for establishing a coherent picture of inter hemispheric climate change and for better understanding of the role of antarctic climate dynamics in the global climate system new zealand is considered to be a sensitive monitor of climate change because it is one of a few sizeable landmasses in the southern hemisphere westerly circulation zone a critical transition zone between subtropical and antarctic influences new zealand has mountainous axial ranges that amplify the climate signals and consequently the environmental gradients are highly sensitive to subtle changes in atmospheric and oceanic conditions since 1995 intimate has through a series of international workshops sought ways to improve procedures for establishing the precise ages of climate events and to correlate them with high precision for the last 30 000 calendar years the nz intimate project commenced in late 2003 and has involved virtually the entire new zealand palaeoclimate community its aim is to develop an event stratigraphy for the new zealand region over the past 30 000 years and to reconcile these events against the established climatostratigraphy of the last glacial cycle which has largely been developed from northern hemisphere records e g last glacial maximum lgm termination i younger dryas an initial outcome of nz intimate has been the identification of a series of well dated high resolution onshore and offshore proxy records from a variety of latitudes and elevations on a common calendar timescale from 30 000 cal yr bp to the present day high resolution records for the last glacial coldest period lgcp including the lgm sensu stricto and last glacial interglacial transition lgit from auckland maars kaipo and otamangakau wetlands on eastern and central north island marine core md97 2121 east of southern north island speleothems on northwest south island okarito wetland on southwestern south island are presented discontinuous fragmentary records comprising compilations of glacial sequences fluvial sequences loess accumulation and aeolian quartz accumulation in an andesitic terrain are described comparisons with ice core records from antarctica epica dome c and greenland gisp2 are discussed a major advantage immediately evident from these records apart from the speleothem record is that they are linked precisely by one or more tephra layers based on these new zealand terrestrial and marine records a reasonably coherent regionally applicable sequence of climatically linked stratigraphic events over the past 30 000 cal yr is emerging three major climate events are recognised 1 lgcp beginning at ca 28 000 cal yr bp ending at termination i ca 18 000 cal yr bp and including a warmer and more variable phase between ca 27 000 and 21 000 cal yr bp 2 lgit between ca 18 000 and 11 600 cal yr bp including a lateglacial warm period from ca 14 800 to 13 500 cal yr bp and a lateglacial climate reversal between ca 13 500 and 11 600 cal yr bp and 3 holocene interglacial conditions with two phases of greatest warmth between ca 11 600 and 10 800 cal yr bp and from ca 6 800 to 6 500 cal yr bp some key boundaries coincide with volcanic tephras copyright 2007 john wiley sons ltd

some aspects of the organic geochemistry of petroleum fluids the most important influences on the compositions of petroleum fluids are in many cases the composition of a petroleum sample may allow the depositional environment of its source rock and its temperature history before and after expulsion to be determined this information assists the search for more petroleum in a region we suggest that this approach should be used more frequently to validate models of petroleum generation and migration in the second part of the paper we discuss the origin and nature of the differences in petroleum composition which are frequently found within individual petroleum reservoirs petroleum accumulations in permeable reservoirs are normally found to be inmechanical equilibrium and verticalchemical equilibrium this is manifested by constant subsurface fluid density at any given depth across the accumulation and increases in subsurface density with depth known as gravitational segregation however even in permeable reservoirs lateral differences in composition inherited from the reservoir filling process are not totally eliminated by mixing processes such as diffusion and convection thus lateral chemical equilibrium is often not achieved and lateral compositional variations are observed in present day oil and gas reservoirs these observations are justified in terms of order of magnitude estimates for the rates at which reservoirwide mixing occurs a case history is presented

establishing tephrostratigraphic frameworks to aid the study of abrupt climatic and glacial transitions a case study of the last glacial interglacial transition in the british isles c 16 8 ka bp abstract distally dispersed tephra layers have become an important tool in the investigation of palaeoenvironmental and archaeological records across the globe they offer possibilities for the synchronisation and improved chronological control in those records to which they can be traced and hence contribute to an improved understanding of the pattern and timing of environmental and archaeological change during periods of rapid climatic adjustment however their use as robust isochronous markers for synchronising records is frequently compromised by uncertainties relating to stratigraphical context precise chronology and chemical composition here we collate and review the tephrostratigraphical information dating to the last glacial interglacial transition lgit c 16 8 ka bp in the british isles based on published and unpublished records obtained from 54 sites based on details of their stratigraphic position chronology and chemical composition we propose that 26 individual eruption events may be represented in this collective record which spans the lgit the great majority of these eruptives can be traced in origin to iceland but we also report on the recent discoveries of ultra distal tephra from the north american cascades range including for the first time the mount st helens j tephra at a site in southern ireland these particular ultra distal discoveries have resulted from a reinterpretation of older data demonstrating the potential importance of unknown analyses in older tephra datasets the outcome of this review is a comprehensive but provisional tephrostratigraphic framework for the lgit in the british isles which helps to focus future research on parts of the scheme that are in need of further development or testing the results therefore make an important contribution to the wider european tephrostratigraphic framework while adding new discoveries of transcontinental isochronous tephra markers

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

a study of the holzener asphaltkalk northern germany observations regarding the distribution composition and origin of organic matter in an exhumed petroleum reservoir abstract the holzener asphalkalk deposit is located on the southwestern flank of the hils syncline northern germany it consists of a series of kimmeridgian portlandian bitumen impregnated limestones cumulative thickness of nearly 200 m overlain unconformably by neocomian claystones and underlain by older jurassic and triassic sediments the most bitumen rich limestone layers have been extensively mined with the result that there is three dimensional access to what is probably an exhumed series of stacked petroleum reservoirs geochemical petrological and petrophysical techniques were used to gain some insight into the distribution and the source of the organic matter in two of the 13 layers of the deposit most disseminated organic matter was found to be soluble in organic solvents and rich in non hydrocarbons its distribution appears to be controlled by ooid versus carbonate matrix abundances the occurrence of fractures and degree of impregnation small meso to micro pores have high bitumen saturations whereas large pores meso to macro have much lower saturations mature petroleum is thought to have once filled all pores but alteration has probably removed as much as 85 of it mainly from the large pores regional geochemical considerations pyrolysis and stable carbon isotope data indicate that the original petroleum was most probably derived from the underlying posidonia shale toarcian source rock asphaltene pyrolysis data indicate that an algal lacustrine co source might have also contributed to the deposit

developing a holocene tephrostratigraphy for northern japan using the sedimentary record from lake kushu rebun island abstract palaeoclimate records in east asia offer significant potential to further our understanding of monsoon dynamics and can serve as a link between north atlantic and tropical climate systems the sedimentary core from lake kushu rebun island provides the first high resolution palaeoclimate record from northern japan in order for this regionally significant archive to be synchronised to other records and to generate a more detailed holocene tephra lattice for east asia we present the first cryptotephra stratigraphy for northern japan using the kushu rk12 core the detailed rk12 tephrostratigraphy integrates local and far travelled tephras originating from japan russia china north korea and most likely indonesia five key cryptotephra layers have been identified precisely dated and correlated to the specific eruptions or the source region b tm tephra changbaishan volcano sh 12 tephra shiveluch volcano ko g tephra komagatake volcano ma f j tephra mashu volcano and rk12 0819 tephra with possible indonesian origin these tephra horizons are very widely dispersed providing opportunities to synchronise distant palaeoclimate records from the polar region through high northern latitudes to the tropics which facilitate interregional comparison of palaeoclimate and environmental data in addition a number of the geochemically analysed horizons contain other minor numbers of compositionally distinct glass which can also be grouped and correlated to their source volcanoes these minor analyses are of interest since they provide new insight into regional tephra dispersal e g ash dispersal potential of aira and towada and could suggest that there are other potential eruptions that have yet to be identified in the geological record e g potential changbaishan eruptions the integrated lake kushu cryptotephra record extends the ash dispersal of several key tephra horizons in the region the presence of the shiveluch sh 12 tephra in lake kushu ca 1900 km away documents the first example of a russian tephra reaching the japanese archipelago furthermore glass compositions suggest that the core could preserve an eruption event derived from indonesia highlighting the future possibility to significantly extend and interlink the tephra lattice across the entirety of asia this is an essential step for the understanding of how climate changes propagate over large geographical areas indeed several of these tephra markers coincide with significant ecological changes reflected in the pollen proxy record at lake kushu using this high resolution palaeoenvironmental record we however find no significant ecological impact following the large late holocene millennium eruption from changbaishan china north korea

integrating the holocene tephrostratigraphy for east asia using a high resolution cryptotephra study from lake suigetsu sg14 core central japan abstract tephra volcanic ash layers have the potential to synchronise disparate palaeoenvironmental archives on regional to hemispheric scales highly productive arc regions like those in east asia offer a considerable number of widespread isochrons but before records can be confidently correlated using these layers a refined and integrated framework of these eruptive events is required here we present the first high resolution holocene cryptotephra study in east asia using the lake suigetsu sedimentary archive in central japan the holocene tephrostratigraphy has been extended from four to twenty ash layers using cryptotephra extraction techniques which integrates the deposits from explosive eruptions from north korea china south korea and along the japanese arc this lake suigetsu tephrostratigraphy is now the most comprehensive record of east asian volcanism and the linchpin site for correlating sequences across this region major element glass geochemical compositions are presented for the tephra layers in the sequence which have been compared to proximal datasets to correlate them to their volcanic source and specific eruptions this study has significantly extended the ash dispersal of many key holocene marker layers and has identified the first distal occurrence of isochrons from ulleungdo and changbaishan volcanoes utilising the high precision lake suigetsu chronology we are able to provide constrained eruption ages for the tephra layers which can be transferred into other site specific age models containing these markers this new framework indicates that several isochrons stratigraphically bracket abrupt climate intervals in japan and could be used to precisely assess the regional and hemispheric synchronicity of these events

a new high resolution holocene tephra stratigraphy in eastern iceland improving the icelandic and north atlantic tephrochronology a new and improved holocene tephra stratigraphy and tephrochronological framework for eastern and northern iceland is presented investigations of a sediment sequence from lake logurinn have revealed a comprehensive tephra record spanning the last 10 200 years a total of 157 tephra layers have been identified whereof 149 tephra layers have been correlated to its source volcanic system using geochemistry stratigraphy and age fifteen layers have chemical composition of two affinities that possibly represent two very closely spaced eruptions thus these 157 tephra layers are believed to represent 172 explosive eruptions nineteen tephra marker layers have been identified in the lake logurinn record g1922 a1875 v1477 v1410 h1636 k1625 o1362 g1354 k1262 v874 hrafnkatla sn 1 grakolla hy h3 h4 ho ll1755 and reitsvik 8 tephra markers new potential tephra markers are the silicic askja l 9400 cal bp the low titanium basalt layers ll 1774 10 150 cal bp and ll 1755 9990 cal bp assigned to veidivotn bardarbunga and the tephra layers ll 1527 8 7850 cal bp ll 911 2 2370 cal bp ll 908 4 2350 cal bp ll 781 9 1930 cal bp ll 644 4 1480 cal bp not yet correlated to a source volcanic system a silicic tephra marker layer reitsvik 8 correlated to the fosen tephra in norway has been identified in lake logurinn the lake logurinn tephra record has been connected and integrated with the icelandic terrestrial tephrochronology and stratigraphy through 102 tephra layers the marine tephra stratigraphy through 39 layers and overseas through 9 tephra layers this record is the first high resolution tephra stratigraphical and chronological framework for the holocene in eastern iceland as well as the most detailed and continuous record and has considerable potential to serve as a key section or a stratotype for the holocene in eastern iceland and the north atlantic

minimum volume of a tephra fallout deposit estimated from a single isopach a simple method is presented to calculate the minimum volume of an exponentially thinning fall deposit for which only one isopach is available this method exploits the fact that the product of the area enclosed within an isopach a and its thickness t reaches a maximum value ta max for a certain isopach it is shown that the minimum volume is vmin 3 69ta which is equal to the actual volume when ta ta max calculation of vmin for 327 isopachs from 74 fallout deposits shows that it is often just a bit lower than the volume calculated from all the available isopachs it is therefore proposed that vmin provides a useful minimum volume estimate for fallout deposits for which only one isopach is available

the spatial distribution of holocene cryptotephras in north west europe since 7 ka implications for understanding ash fall events from icelandic eruptions abstract we present distribution maps for all cryptotephras distal volcanic ash layers younger than 7 ka that have been reported from three or more lakes or peatlands in north west europe all but one of the tephras originates from iceland the exception has been attributed to jan mayen we find strong spatial patterning in tephra occurrence at the landscape scale most but not all of the tephra occurrences are significantly spatially clustered which likely reflects atmospheric and weather patterns at the time of the eruptions contrary to expectations based on atmospheric modelling studies tephras appear to be at least as abundant in ireland and northern scotland as in scandinavia rhyolitic and other felsic tephras occur in lakes and peatlands throughout the study region but andesitic and basaltic tephras are largely restricted to lake sites in the faroe islands and ireland explanations of some of these patterns will require further research on the effects of different methodologies for locating and characterizing cryptotephras these new maps will help to guide future investigations in tephrochronology and volcanic hazard analysis

paleoseismic and slip rate observations along the honey lake fault zone northeastern california usa the honey lake fault is a major strike slip fault in northeastern california that accommodates northwest directed right lateral shear in the northern walker lane we reexamine the fault s paleoseismic history and slip rate by evaluating a natural stream bank exposure of the fault and offset terrace riser structural and stratigraphic relations within the modern stream cut radiocarbon ages and a detailed topographic survey of the offset terrace riser are used to estimate a holocene fault slip rate of 1 7 0 6 mm yr or more we also interpret the occurrence of at least four surface rupturing earthquakes during the last 7025 calendar years before present b p three of the surface rupturing earthquakes occurred prior to 4670 calendar years b p and have interevent times that range between 730 and 990 yr the stratigraphic record is limited after 4670 calendar years b p and records evidence for at least one more subsequent surface rupturing earthquake

submarine paleoseismology of the northern hikurangi subduction margin of new zealand as deduced from turbidite record since 16 ka abstract paleoseismic studies seek to characterise the signature of pre historical earthquakes by deriving quantitative information from the geological record such as the source magnitude and recurrence of moderate to large earthquakes in this study we provide a 16 000 yr long paleo earthquake record of the 200 km long northern hikurangi margin new zealand using cm thick deep sea turbidites identified in sediment cores cores were collected in strategic locations across the margin within three distinct morphological re entrants the poverty ruatoria and matakaoa re entrants the turbidite facies vary from muddy to sandy with evidence for rare hyperpycnites interbedded with hemipelagites and tephra we use the oxal probabilistic software to model the age of each turbidite using the sedimentation rate of hemipelagite deduced from well dated tephra layers and radiocarbon ages measurements on planktonic foraminifera turbidites are correlated from one core to the other using similarity in sedimentary facies petrophysical properties and ages results show that 46 turbidites are synchronous along the entire margin amongst them 41 are interpreted as originating from the upper continental slope in response to earthquake triggered slope failures between 390 170 to 16 450 310 yr bp using well established empirical relationships that combine peak ground acceleration magnitude and location of earthquakes we calculate that synchronous slope failures were triggered by the rupture of 3 of the 26 known active faults in the region each capable of generating mw 7 3 to 8 4 earthquakes two are crustal reverse faults and one is the subduction interface the 41 mw 7 3 earthquakes occurred at an average recurrence interval of 400 yr over the last 16 000 yr among them twenty are interpreted as subduction interface earthquakes that occurred at an average recurrence interval of 800 yr with alternating periods of high activity and low return times 305 610 yr and quiescence periods with high return times 1480 2650 yr based on turbidite paleoseismology we propose that subduction interface earthquakes were of lower magnitude during active periods mw 7 5 than during quiescence periods mw 8 2

active faulting on the wallula fault zone within the olympic wallowa lineament washington state usa the wallula fault zone is an integral feature of the olympic wallowa lineament an 500 km long topographic lineament oblique to the cascadia plate boundary extending from vancouver island british columbia to walla walla washington the structure and past earthquake activity of the wallula fault zone are important because of nearby infrastructure and also because the fault zone defines part of the olympic wallowa lineament in south central washington and suggests that the olympic wallowa lineament may have a structural origin we used aeromagnetic and ground magnetic data to locate the trace of the wallula fault zone in the subsurface and map a quarry exposure of the wallula fault zone near finley washington to investigate past earthquakes along the fault we mapped three main packages of rocks and unconsolidated sediments in an 10 m high quarry exposure our mapping suggests at least three late pleistocene earthquakes with surface rupture and an episode of liquefaction in the holocene along the wallula fault zone faint striae on the master fault surface are subhorizontal and suggest reverse dextral oblique motion for these earthquakes consistent with dextral offset on the wallula fault zone inferred from offset aeromagnetic anomalies associated with ca 8 5 ma basalt dikes magnetic surveys show that the wallula fault actually lies 350 m to the southwest of the trace shown on published maps passes directly through deformed late pleistocene or younger deposits exposed at finley quarry and extends uninterrupted over 120 km

late glacial to holocene paleoenvironmental change on the northwestern pacific seaboard kamchatka peninsula russia we used a new sedimentary record from a small kettle wetland to reconstruct the late glacial and holocene vegetation and fire history of the krutoberegovo ust kamchatsk region in eastern kamchatka peninsula russia pollen and charcoal data suggest that the late glacial landscape was dominated by a relatively fire prone larix forest tundra during the greenland interstadial complex gi 1 and a subarctic steppe during the younger dryas gs1 the onset of the holocene is marked by the reappearance of trees mainly alnus incana within a fern and shrub dominated landscape the holocene thermal maximum htm features shifting vegetational communities dominated by alnus shrubs diverse forb species and locally abundant aquatic plants the htm is further defined by the first appearance of stone birch forests betula ermanii kamchatka s most abundant modern tree species the late holocene is marked by shifts in forest dynamics and forest graminoid ratio and the appearance of new non arboreal taxa such as bayberry myrica and meadow rue filipendula kamchatka is one of earth s most active volcanic regions during the late glacial and holocene kamchatka s volcanoes spread large quantities of tephra over the study region thirty four tephra falls have been identified at the site the events represented by most of these tephra falls have not left evidence of major impacts on the vegetation although some of the thicker tephras caused expansion of grasses poaceae and at least in one case forest die out and increased fire activity

a nexus of plate interaction vertical deformation of holocene wave built terraces on the kamchatsky peninsula kamchatka russia kamchatsky peninsula lies within a complex meeting place of tectonic plates in particular the orthogonal interaction of the west moving komandorsky island block with mainland kamchatka examining the holocene history of vertical deformation of marine wave built terraces along the peninsular coast we differentiated tectonic blocks undergoing uplift and tilting separated by zones of stable or subsided shorelines we analyzed 200 excavations along 30 coastal profiles and quantified vertical deformation on single profiles as well as along the coast using paleoshorelines dated with marker tephras for the past 2000 yr the average rates of vertical deformation range from about 1 to 7 mm yr uplift patterns are similar to those detected from historical leveling and from mapping of the stage 5e quaternary marine terrace ca 120 ka average vertical deformation in the holocene is highest for the shortest studied time period from ca a d 250 to 600 and it is several times faster than rates for marine oxygen isotope stage mis 5e terraces vertical displacements observed along the coast are most likely coseismic and probably have included subsidence as well as uplift events because subsidence is generally associated with erosion almost surely more prehistoric large earthquakes occurred than are recorded as topographic steps in these terraces we suggest that the distribution of coastal uplift and subsidence observed along the kamchatsky peninsula coastline is qualitatively explained by the squeezing of the kamchatsky peninsula block between the bering and okhotsk plates and the komandorsky island block

coseismic coastal subsidence associated with unusually wide rupture of prehistoric earthquakes on the kamchatka subduction zone a record in buried erosional scarps and tsunami deposits abstract the prograding strand plain of avachinsky bay kamchatka russia along the highly active kamchatka subduction zone exhibits geological evidence buried erosional scarps for coseismic subsidence only three times in the last four millennia the last event about 1200 years ago this same coast has a historical record since a d 1737 of five subduction zone earthquakes with large tsunami runup 5 m the last of which was the 1952 mw 9 kamchatka earthquake and a geological record of more than 30 large tsunamis in the last 4000 years this rarity of buried scarps relative to large earthquakes contrasts with the cascadia strand plain in sw washington state where most or all large events are represented by buried scarps a strong factor in the amplitude and sign of coseismic deformation is distance from the seaward edge of a subduction zone the trench the avachinsky bay coastline is 180 200 km from the trench with 25 slab dip requiring unusually wide ruptures to generate significant coseismic subsidence this coastal zone is undergoing net subsidence approximately equivalent to the total of the three coseismic subsidence events generating a sequence of beach ridges that increase in elevation seaward each of the three unusual coseismic subsidence events comprises a an earthquake whose deformation field caused b onshore coseismic subsidence thus local sea level rise and c sufficient deformation offshore to produce a large tsunami a b c followed by d a period of coastal erosion and shoreline retreat leaving e an erosional beach scarp that was f subsequently buried once progradation resumed we identified dated and correlated the scarps and tsunami deposits from these events with several field methods including trenching tephrostratigraphy and ground penetrating radar the scarps were correlated over an alongshore distance of 50 70 km the most recent event event 1 occurred 800 cal ad 1100 1250 14 years bp event 2 600 cal bc 2400 2450 14 years bp and event 3 1700 cal bc 3300 3500 14 years bp we developed methods for quantifying subsidence coastal erosion and tsunami size for each of these events all three retain evidence of 0 4 1 2 m of coseismic subsidence coastal erosion in the case of event 1 averaged more than 100 m all three event tsunamis were amongst the largest in the last 4000 years

prediction of sea of japan east sea acidification over the past 40 years using a multiparameter regression model 1 a multiparameter linear regression model mlr of aragonite saturation state arg as a function of temperature pressure and o2 concentration in the upper 1 000 m of the sea of japan east sea was derived with an uncertainty of 0 020 1 the arg data n 1 482 used to derive the basin wide arg prediction model were collected during a field survey in 1999 and were corrected for anthropogenic co2 some biases were resolved by addition of a pressure and o2 concentration interaction term to the proposed model correlation between the two predictor terms caused by addition of this term was minimized by centering the data for the three variables thus subtracting the mean from each individual data point validation of the model against data sets obtained in 1992 and 2007 yielded correlation coefficients of 0 995 0 013 for 1992 n 64 p 0 001 and 0 995 0 009 for 2007 n 137 p 0 001 and root mean square errors of 0 064 for 1992 and 0 050 for 2007 the strong correlation between measurements and predictions suggests that the model can be used to estimate the distribution of arg in the sea of japan east sea including dynamic coastal waters on varying time scales when basic hydrographic data on temperature pressure and o2 concentration are available application of the model to past measurements for the sea of japan east sea indicated that interdecadal variability 2 from the mean in arg corrected for anthropogenic co2 was generally high 0 1 0 7 in the upper water layer 200 m depth and decreased 0 05 0 2 with depth for waters deeper than 500 m the interdecadal variability is largely controlled by variations in the degree of water column ventilation superimposed on this natural variability the input of co2 derived from fossil fuels has markedly acidified the upper water layers during the anthropocene and thereby moved the aragonite saturation horizon upward by 50 250 m the impact of co2 derived from fossil fuels on upper ocean acidification will increase in the future the present study indicates that in combination with other easily measurable parameters a multifunctional model can be a powerful tool for predicting the temporal evolution of arg in the ocean including coastal waters that are highly likely to be susceptible to ocean acidification in the future

reconstructing the oceanic 13c suess effect the anthropogenic 13c change for the time period 1968 to 1991 was determined based on calculations of the preformed 13c 12c of dissolved inorganic carbon dic distributions on isopycnal surfaces in the main thermocline of the pacific north atlantic and south indian oceans the time rate of change of preformed 13c the 13c suess effect along isopycnals was calculated using cfc derived water ages and yields a time history of the surface water 13c change at the isopycnal outcrop location the surface ocean suess effect recorded on isopycnals decreased with increasing outcrop latitude from approximately 0 2 decade 1 within the subtropics to around 0 1 decade 1 in the subpolar oceans in the pacific ocean these surface 13c change rate reconstructions agree both in magnitude and meridional trend with direct observations of surface ocean 13c changes reported from time series measurements and from comparisons of surface water 13c of dic measurements in 1970 and 1993 a global ocean average surface 13c rate of change of 0 15 0 04 decade 1 is determined which is slightly smaller than a previous time series data and model based estimate 0 171 decade 1 bacastow etal 1996 depth integrations of the 13c reconstructions in the pacific indian and atlantic oceans when combined with these previous individual depth profile comparisons and geochemical ocean sections study bomb 14c inventories quay et al 1992 imply a global depth integrated 13c change rate of 9 7 2 4 m yr 1 over the time period 1970 1990 these results imply a net oceanic co2 uptake rate of 1 9 0 9 gt c yr 1 over the time period 1970 1990 when applied to an atmospheric 13co2 and 12co2 budget

decadal 1994 2008 change in the carbon isotope ratio in the eastern south pacific ocean we determined the 14 year change in the anthropogenic co2 inventory in the eastern south pacific ocean along the 110 w meridian from 67 s to 21 n using seawater 13c data sets collected in 1994 and 2008 the vertical integral of the 14 year 13c change was assessed in five latitude bands and found to be greatest 14 7 m yr 1 in the subpolar band 38 s 55 s and smallest 3 0 m yr 1 in the tropical band 21 n 18 s the 13c change in each of the latitudinal bands was primarily caused by inputs of anthropogenic co2 via air sea exchange and transport more than 50 of the total anthropogenic co2 was added to the subpolar band via the northward movement of antarctic intermediate water aaiw from the south and the remaining 50 was added via air sea exchange we also calculated the ratio of the temporal change in 13c to the change in dissolved inorganic carbon which is a measure of the efficiency of oceanic uptake of anthropogenic co2 the ratio for aaiw in 1994 0 017 mol kg 1 1 was greater than that in 2008 0 010 mol kg 1 1 based on the change in preformed 13c and dissolved inorganic carbon dic indicating reduced efficiency of co2 uptake by the southern ocean in 2008 relative to that in 1994 aaiw remained at the surface for a shorter period in 2008 relative to 1994 and thus would have taken up less atmospheric co2 prior to subduction the projected reduction in this ratio indicates a weakening of co2 uptake by the southern ocean in the future

paleoseismicity of the cascadia subduction zone evidence from turbidites off the oregon washington margin cores from cascadia deep sea channel contain sequences of turbidites that can be correlated and dated by the first occurrence of volcanic glass from the mount mazama eruption 6845 50 radiocarbon yrbp turbidity currents from the tributaries appear to have occurred synchronously to form single deposits in the main channel there being only 13 turbidite deposits in the lower main channel since the mazama eruption instead of the twice as many expected if the tributaries had behaved independently in addition to the cascadia channel 13 post mazama turbidites have been deposited in the astoria canyon and at two sites off cape blanco sample locations that span 580 km of the oregon washington margin pelagic intervals deposited between the turbidites suggest that in each place the turbidity currents occurred fairly regularly every 590 170 years on average the best explanation of the spatial and temporal extent of the data is that the turbidity currents were triggered by 13 great earthquakes on the cascadia subduction zone the variability of turbidite timing is similar to that for great earthquake cycles the thickness of the topmost pelagic layer suggests the last event was 300 60 years ago from three places along the margin but this number may be a biased underestimate it is however consistent with the youngest sudden subsidence event on the washington coast the turbidite data demonstrate that the near term hazard of a great earthquake on the cascadia subduction zone is of the order of 2 10 in the next 50 years

late quaternary tephrostratigraphy of southern chile and argentina abstract the southern and austral volcanic zones of the andes comprise 74 volcanic centres with known post glacial activity at least 21 of these have had one or more large explosive eruptions in the late quaternary dispersing tephra over vast areas these tephra layers therefore have great potential as tephrochronological marker horizons in palaeoenvironmental studies in southern chile and argentina a region that is particularly useful to study climate dynamics of the southern hemisphere however to date tephrochronology has rarely been fully utilised in this region as a correlation and dating tool here we review the existing post glacial tephrostratigraphic record of the southern and austral volcanic zones and compile a database of known occurrences of tephra from these volcanoes in ice and lacustrine marine peat and cave sediment records we address the inconsistencies in and revisions of the tephrostratigraphies presented in prior literature and discuss the challenges in correlating tephras and the limitations of the tephrostratigraphic record in this area this study highlights the many gaps that still exist in our knowledge of the eruptive histories of these volcanoes but also reveals the largely under utilised potential of tephra as a correlation tool in this region this is exemplified by the severe lack of adequate geochemical analysis of tephra layers preserved in many lacustrine and peat sediment sections which are particularly important tephrostratigraphic records in southern chile and argentina due to the paucity of surface preservation

large scale deformation related to the collision of the aleutian arc with kamchatka the far western aleutian island arc is actively colliding with kamchatka westward motion of the aleutian arc is brought about by the tangential relative motion of the pacific plate transferred to major right lateral shear zones north and south of the arc early geologic mapping of cape kamchatka a promontory of kamchatka along strike with the aleutian arc revealed many similarities to the geology of the aleutian islands later studies support the notion that cape kamchatka is the farthest west aleutian island and that il has been accreted to kamchatka by the process of arc continent collision deformation associated with the collision onshore kamchatka includes gravimetrically determined crustal thickening and formation of a narrow thrust belt of intensely deformed rucks directly west of cape kamchatka the trend of the thrust faults is concave toward the collision zone indicating a radial distribution of maximum horizontal compressive stress offshore major crustal faults trend either oblique to the kamchatka margin or parallel to major aleutian shear zones these offshore faults are complex accommodating both strike slip and thrust displacements as documented by focal mechtmisms and seismic reflection data earthquake activity is much higher in the offshore region within a zone bounded to the north by the northernmost aleutian shear zone and to the west by an apparent aseismic front analysis of focal mechanisms in the region indicate that the present day arc continent contact zone is located directly east of cape kamchatka in modeling the dynamics of the coiiision zone using thin viscous sheet theory the rhealogical parameters are only partially constrained to values of n the effective power law exponent 2 3 and ar the argand number s 30 these values are consistent with a fnrcarc thermal profile of kamchatka previously determined from heat flow modeling the thin viscous sheet modeling also indicates that onshore thrust faulting is a consequence not only of compressive stresses resulting from the west directed collision but also of sediment induced coupling of the subducting pacific plate

arc continent collision of the aleutian komandorsky arc into kamchatka insight into quaternary tectonic segmentation through pleistocene marine terraces and morphometric analysis of fluvial drainage at the nw corner of the pacific region just south of the kamchatsky peninsula the northern tip of pacific plate subduction and associated volcanic arc interacts with the western end of the aleutian komandorsky dextral transform plate boundary and associated arc study of both holocene and pleistocene sequences of uplifted marine terraces and also of fluvial drainage patterns on the kamchatsky peninsula allows us to highlight active tectonics produced by complex plate interaction our results show that the central eastern coast of the peninsula is currently divided into four different zones consisting in uplifted blocks associated with various uplift rates in front of a fold and thrust zone to the west our main tectonic benchmark the altitude of the shoreline correlated to last interglacial maximum mis 5e yields late pleistocene uplift rates ranging from 0 2 to 2 74 mm yr one of the main active faults bounding the coastal blocks is dextral and is interpreted as a prolongation of an offshore fault of the aleutian komandorsky dextral transform plate boundary we suggest that structures on the kamchatsky peninsula accommodate a part of the transform motion but that mainly the arc continent collision of the aleutian arc against kamchatka produces a bulldozer effect on the kamchatsky peninsula

late cenozoic tephrostratigraphy offshore the southern central american volcanic arc 2 implications for magma production rates and subduction erosion pacific drill sites offshore central america provide the unique opportunity to study the evolution of large explosive volcanism and the geotectonic evolution of the continental margin back into the neogene the temporal distribution of tephra layers established by tephrochonostratigraphy in part 1 indicates a nearly continuous highly explosive eruption record for the costa rican and the nicaraguan volcanic arc within the last 8 m y the widely distributed marine tephra layers comprise the major fraction of the respective erupted tephra volumes and masses thus providing insights into regional and temporal variations of large magnitude explosive eruptions along the southern central american volcanic arc cava we observe three pulses of enhanced explosive magmatism between 0 1 ma at the cordillera central between 1 2 ma at the guanacaste and at 3 ma at the western nicaragua segments averaged over the long term the minimum erupted magma flux per unit arc length is 0 017 g ms tephra ages constrained by ar ar dating and by correlation with dated terrestrial tephras yield time variable accumulation rates of the intercalated pelagic sediments with four prominent phases of peak sedimentation rates that relate to tectonic processes of subduction erosion the peak rate at 2 3 ma near osa particularly relates to initial cocos ridge subduction which began at 2 91 0 23 ma as inferred by the 1 5 m y delayed appearance of the oib geochemical signal in tephras from barva volcano at 1 42 ma subsequent tectonic re arrangements probably involved crustal extension on the guanacaste segment that favored the 2 1 ma period of unusually massive rhyolite production

holocene tephrostratigraphic framework and monsoon evolution of east asia key tephra beds for synchronising palaeoclimate records abstract in east asia our understanding of holocene climate change forcing mechanisms and propagation require the precise chronological control of palaeoclimate records to allow robust integration of data sets the existing chronologies predominantly based on 14c method however are not sufficient to constrain key questions about abrupt climate shifts that occur within a century in the transitions between states widely dispersed tephra layers allow precise dating and synchronisation of sedimentary archives providing a chronological framework for integrating records especially where the visible tephra record is complemented by the addition of cryptotephra non visible ash despite significant tephra studies in this region however a comprehensive holocene tephra framework is not available to address this issue we carry out a thorough review on holocene tephra investigations undertaken in japan using widespread tephra beds we present an integrated tephra framework and suggest the way forward for establishing this as a wider approach for east asia the framework is based on twenty two ash layers that are mainly from japan and to a lesser extent china n korea s korea and russia each tephra is assessed in terms of chronology geochemistry and distribution the framework is compared with high resolution palaeoclimate records from east asia using this we demonstrate regional variations in monsoon evolution and more importantly the potential of tephra isochrons in constraining such variations given the scarce identification of tephra layers in those well resolved palaeoclimate records we advocate a more systematic employment of the cryptotephra method which would potentially lead to a significant advance in east asian tephrochronology and the correlation of palaeoclimate archives in the region

geochemical effects of petroleum migration and expulsion from toarcian source rocks in the hils syncline area nw germany for mature oil prone source rocks of toarcian age in the hils syncline area nw germany the geochemical effects of primary migration of petroleum are shown expulsion has occurred at high efficiencies primarily via a network of macro and micro fractures the effects of this fracture controlled expulsion with respect to gross and molecular composition of c15 soluble organic matter are documented samples from fractured intervals have expelled total c15 soluble organic matter more efficiently than adjacent unfractured intervals a systematic comparison of samples taken at cm intervals away from macro fractures reveals compositional gradients which are interpreted to reflect preferential depletion of saturated and aromatic hydrocarbons from the source rock shale into the fractures extracts of shale samples directly at fracture walls are enriched in nso compounds and highly polar asphaltene like fractions the composition of residual petroleum fluids extracted from the fracture fill materials is variable in some cases there is a close match with that of the shale at some distance away from the fractures in other cases there is geochemical evidence to suggest that petroleum fluids were chemically altered during lateral flow along the fractures based on available geological and geochemical evidence a conceptual model is proposed to explain fracture development and fluid flow processes rapid heating by a nearby intrusive body at shallow depths when the toarcian sediments still contained about 15 20 pore water has played an important role overpressuring of aqueous pore fluids with abundant dissolved carbonate caused intense fracturing of the rich intervals in the mature toarcian sections finally the closely interdependent relationships between petroleum generation and petroleum migration processes are documented especially the evolution of these relationships with maturity progress from immature 0 48 rm to mature 0 68 and 0 88 rm and overmature 1 45 rm stages is shown for example in the maturity interval from 0 68 to 0 88 rm most of the measured shale compaction and porosity decrease is achieved by expulsion of petroleum for some samples there is an inverse relationship between kerogen quality and extractable hydrocarbon yields suggesting that expulsion efficiencies were higher from the better quality intervals because the petroleum achieved higher saturations and hence higher relative permeabilities

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

oil generation and migration in the gifhorn trough nw germany abstract the origin and migration of oils from selected oil fields in the gifhorn trough nw germany was investigated by geochemical analysis of crude oils and possible lower and middle jurassic source rocks productive reservoir sandstones in the gifhorn trough occur in the dogger beta zone of the middle jurassic bajocian and are interbedded with shales that contain 1 2 toc mostly type iii kerogen in the lower jurassic toarcian organic matter rich shales 9 12 toc whose kerogen has a type ii composition form the best quality oil prone source rocks biomarker and stable isotope analyses of oils and source rock extracts reveal that all oils analysed are derived from the lower toarcian shales lias epsilon the timing of oil generation and migration was investigated by reconstructing the geothermal history of the source rock in specific drainage areas and determining the availability of migration pathways through geological time hydrocarbon generation started in the central part of the gifhorn trough in upper cretaceous time differences in the maturity of the oils display separate small drainage areas close to the reservoirs variations in oil composition within deep buried reservoirs indicate the preservation of different migration phases

aperiodic recurrence of geologically recorded tsunamis during the past 5500 years in eastern hokkaido japan 1 along hokkaido s pacific coast near the town of kiritappu sandy deposits in a muddy lagoon and on a nearby beach ridge plain provide evidence for 15 tsunamis between 200 and 6000 years ago additional sand beds at the lagoon probably represent the historical tsunamis of a d 1843 and 1894 we observed the sequences of sandy deposits in continuous slices 2 to 4 m deep some of the deposits consist of just a single sand bed whereas others contain multiple units of sand muddy sand or sandy mud and mud caps including plant detritus we also found at the lagoon a 17th century tsunami deposit that thickens and thins regardless of elevation or distance inland we bracketed the ages of most of the inferred tsunamis by radiocarbon dating of detritus mainly seeds and leaves at the lagoon and charcoal at the beach ridge plain from pretsunami and posttsunami beds tsunami dates computed from the bracketing ages commonly have uncertainties spanning 2 to 4 centuries within these uncertainties the inferred sequence of 15 prehistoric tsunamis at the lagoon beginning almost 6000 years ago can be matched tsunami by tsunami with the inferred history at the beach ridge plain 15 km away the sand sheet extents suggest that most of these tsunamis were larger than any generated at hokkaido in the last 200 years the intervals between these inferred outsized tsunamis average nearly 400 years but range widely from about 100 to about 800 years

prehistoric human responses to volcanic tephra fall events in the ust kamchatsk region kamchatka peninsula kamchatsky krai russian federation during the middle to late holocene 6000 500 cal bp abstract prehistoric peoples in kamchatka coped with recurrent volcanic tephra fall events during the middle to late holocene recent data collected by the international collaborative circumpolar archaeological project icaap between 2009 and 2011 explores the long term relationships between drastic landscape change and concomitant human response a combination of new archaeological paleoenvironmental and tephrochronological data demonstrate how the major ksudach 1750 cal bp ks1 eruption accelerated settlement relocation from the interior to the paleo coastline

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

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

a mid to late holocene cryptotephra framework from eastern north america abstract holocene cryptotephras of alaskan and pacific northwestern origin have recently been detected ca 7000 km away on the east coast of north america this study extends the emerging north american tephrochronological framework by geochemically characterising seventeen cryptotephra layers from four newly explored peatlands all detected tephras were deposited during the late holocene with no horizons present in the peat between ca 3000 5000 years ago the prevalence of the alaskan white river ash eastern lobe ad 847 1 is confirmed across the eastern seaboard from newfoundland to maine and a regional depositional pattern from mount st helens set w ad 1479 1482 is presented the first occurrences of four additional cryptotephras in eastern north america are described three of which may originate from source regions in mexico kamchatka russia and hokkaido japan the possibility of such tephras reaching eastern north america presents the opportunity to link palaeo archives from the tropics and eastern asia with those from the western atlantic seaboard aiding inter regional comparisons of proxy climatic records

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

stratigraphy distribution and petrographic properties of holocene tephras in hokkaido northern japan abstract thirty one widespread visible holocene tephras in hokkaido northern japan were identified and their stratigraphic relationships were examined among these three tephras from komagatake volcano ko c1 ko c2 and ko g three from tarumae volcano ta a ta b and ta c us 1663 from usu volcano ma b from mashu volcano and b tm from baegdusan volcano on the boundary between north korea and china cover a large area of southern and eastern hokkaido and are thus useful tephras for correlating sedimentary records and holocene phenomena all tephras were identified on the basis of their mineral composition and the refractive indices and major elements of their glass shards the volcanic glass samples were dehydrated before refractive index measurement by heating at 400 c for 12 h most holocene tephras in hokkaido can be easily identified on the basis of the refractive indices and major element compositions of volcanic glass

defining the potential source region of volcanic ash in northwest europe during the mid to late holocene abstract far travelled volcanic ash fine grained tephra clouds pose economic and societal risks largely through their potential impact on the aviation industry a long view of ash clouds extending over northwest europe assembled from the study and geochemical characterisation of cryptotephra i e tephra invisible to the naked eye in sedimentary records can help inform the understanding of the frequency of such events and the nature of eruptions that generate them here we review the records of cryptotephra deposition in northwest europe during the mid to late holocene the last eight millennia to gain insights into the sources of volcanic ash reaching this region we consider almost 500 published and unpublished datasets for cryptotephras recorded in sedimentary sequences ranging from ireland to latvia and on the basis of their major element geochemical composition we identify 90 unique ash horizons and their likely provenance the majority 72 of the cryptotephras derive from icelandic eruptions but a large proportion 24 originates from other volcanic regions including alaska the cascades kamchatka mexico the azores and possibly the mediterranean although moderate magnitude eruptions in iceland may potentially disperse ash clouds over europe it appears that only large magnitude events in more distant regions have generally had this capacity and then only when suitable meteorological conditions prevailed nevertheless the cryptotephra records demonstrate that ash clouds from most volcanic regions capable of producing large explosive eruptions in the northern mid to high latitudes particularly those to the west of europe as well as in tropical north america have the potential to extend to northwest europe volcanic ash forecasts for this region need therefore to take into account possible risks posed not only by icelandic eruptions but also by any large magnitude eruptions in north america or the north pacific area

anthropogenic co2 accumulation rates in the north atlantic ocean from changes in the 13c 12c of dissolved inorganic carbon 1 the anthropogenic co2 accumulation rate for the north atlantic ocean was estimated on the basis of the decrease in the 13c of the dissolved inorganic carbon measured between cruises in 1981 transient tracers in the north atlantic 1993 oaces and 2003 repeat hydrography a mean depth integrated 13c change of 15 0 3 8 m yr 1 was estimated by applying a multiple linear regression approach to determine the anthropogenic 13c decrease at 22 stations where 13c depth profiles were compared the largest and deepest anthropogenic 13c decreases occurred in the subpolar ocean and in contrast the smallest and shallowest decreases occurred in the tropical ocean a mean anthropogenic co2 accumulation rate of 0 63 0 16 mol c m 2 yr 1 0 32 0 08 pg c yr 1 in the north atlantic ocean over the last 20 years was determined from the mean depth integrated 13c change and a ratio of anthropogenic 13c to dic change of 0 024 mol kg 1 1 only half of the accumulated anthropogenic co2 in the north atlantic during the last 20 years was the result of air sea co2 uptake based on a comparison of the air sea 13co2 flux to the dic13 inventory change with the other half likely a result of northward advective transport

lacustrine turbidites as a tool for quantitative earthquake reconstruction new evidence for a variable rupture mode in south central chile understanding the long term earthquake recurrence pattern at subduction zones requires continuous paleoseismic records with excellent temporal and spatial resolution and stable threshold conditions south central chilean lakes are typically characterized by laminated sediments providing a quasi annual resolution our sedimentary data show that lacustrine turbidite sequences accurately reflect the historical record of large interplate earthquakes among others the 2010 and 1960 events furthermore we found that a turbidite s spatial extent and thickness are a function of the local seismic intensity and can be used for reconstructing paleo intensities consequently our multilake turbidite record aids in pinpointing magnitudes rupture locations and extent of past subduction earthquakes in south central chile comparison of the lacustrine turbidite records with historical reports a paleotsunami subsidence record and a marine megaturbidite record demonstrates that the valdivia segment is characterized by a variable rupture mode over the last 900 years including i full ruptures mw 9 5 1960 1575 1319 9 1127 44 ii ruptures covering half of the valdivia segment mw 9 1837 and iii partial ruptures of much smaller coseismic slip and extent mw 7 5 8 1737 1466 4 also distant or smaller local earthquakes can leave a specific sedimentary imprint which may resolve subtle differences in seismic intensity values for instance the 2010 event at the maule segment produced higher seismic intensities toward southeastern localities compared to previous megathrust ruptures of similar size and extent near concepci n

synchronisation of sedimentary records using tephra a postglacial tephrochronological model for the chilean lake district abstract well characterised tephra horizons deposited in various sedimentary environments provide a means of synchronising sedimentary archives the use of tephra as a chronological tool is however still widely underutilised in southern chile and argentina in this study we develop a postglacial tephrochronological model for the chilean lake district ca 38 to 42 s by integrating terrestrial and lacustrine records tephra deposits preserved in lake sediments record discrete events even if they do not correspond to primary fallout by combining terrestrial with lacustrine records we obtain the most complete tephrostratigraphic record for the area to date we present glass geochemical and chronological data for key marker horizons that may be used to synchronise sedimentary archives used for palaeoenvironmental palaeoclimatological and palaeoseismological purposes most volcanoes in the studied segment of the southern volcanic zone between llaima and calbuco have produced at least one regional marker deposit resulting from a large explosive eruption magnitude 4 some of which now have a significantly improved age estimate e g the 10 5 ka llaima pumice eruption from llaima volcano others including several units from puyehue cordon caulle are newly described here we also find tephra related to the cha1 eruption from chaiten volcano in lake sediments up to 400 km north from source several clear marker horizons are now identified that should help refine age model reconstructions for various sedimentary archives our chronological model suggests three distinct phases of eruptive activity impacting the area with an early to mid holocene period of relative quiescence extending our tephrochronological framework further south into patagonia will allow a more detailed evaluation of the controls on the occurrence and magnitude of explosive eruptions throughout the postglacial

holocene eruptive history of ksudach volcanic massif south kamchatka evolution of a large magmatic chamber the combination of geological tephrochronological and geochemical studies is used to reconstruct the holocene eruptive history of ksudach volcanic massif south kamchatka and to trace the evolution of its magma ksudach is located in the frontal volcanic zone of kamchatka from early holocene till ad 240 the volcano had repetitive voluminous caldera forming eruptions later they gave way to frequent moderate explosive effusive eruptions that formed the shtyubel stratovolcano inside the nested calderas and then to frequent larger explosive eruptions holocene eruptive products are low k2o two pyroxene plagioclase basaltic andesite to rhyodacite mineralogical geochemical and isotopic data suggest that all the rock varieties originated as a result of fractionation of an initial mafic melt with insignificant contamination and assimilation intensive mixing of the fractionating melts prior to and during the course of the eruptions is ubiquitous the eruptions might have been triggered by repetitive injections of new mafic melt into the silicic chamber crystallization of the andesitic and rhyodacitic melts is estimated to have occurred at temperatures of 970 1010 c and 890 910 c respectively ph2o 1 5 2 0 kbar and fo2 close to the nno buffer according to the experimental data such ph2o corresponds to 4 5 5 5 of water in the melt that is close to the content of water in the silicic hornblende bearing magmas of the rear zone of the kuril kamchatka arc hence we suggest that the transition from pyroxene phenocryst associations of the frontal zone to the hornblende bearing ones of the rear zone might be interpreted as reflecting higher temperatures of crystallization of the melts from the frontal zone rather than increasing water content in the rear zone magmas

the indian ocean 13c suess effect the 13c of dissolved inorganic carbon dic decrease the 13c suess effect in the indian ocean was calculated using a multiparameter linear regression comparison of the 1978 geochemical ocean sections study and 1995 world ocean circulation experiment 13c of dic hydrographic and nutrient data the surface ocean 13c decrease rate along 80 and 115 e ranged from approximately 0 1 decade 1 at 55 s to a maximum of approximately 0 18 decade 1 at 35 s and decreased northward to around 0 13 decade 1 at the equator using a global extrapolation based on ocean model results bacastow et al 1996 and previous 13c changes calculated from 1970 to 1993 station reoccupations in the pacific ocean and based on preformed 13c versus chlorofluorocarbon age trends in the indian pacific and atlantic oceans sonnerup et al 1999 an ocean wide average surface ocean 13c rate of change of 0 15 to 0 17 decade 1 was estimated the average depth integrated 13c change rate between 1978 and 1995 along 80 and 115 e was 6 9 0 5 m yr 1 from 58 s to 5 n

holocene volcanic activity at grimsvotn bardarbunga and kverkfjoll subglacial centres beneath vatnajokull iceland assessment of potential future eruptive behaviour of volcanoes relies strongly on detailed knowledge of their activity in the past such as eruption frequency magnitude and repose time the eruption history of three partly subglacial volcanic systems grimsvotn bardarbunga and kverkfjoll was studied by analysing tephra from soil profiles around the vatnajokull ice cap which extend back to 7 6 ka well known regional holocene marker tephra e g h3 h4 h5 were utilized to correlate profiles stratigraphic positions and geochemical compositions were used for fine scale correlation of basaltic tephra around vatnajokull ice cap 345 tephra layers were identified of which 70 originated from grimsvotn bardarbunga or kverkfjoll the eruption frequency of each volcanic system was estimated grimsvotn has been the most active with an average of 7 eruptions 100 years range 4 14 during prehistoric time before 870 ad bardarbunga has been the second most active with 5 eruptions 100 years range 1 8 and kverkfjoll has remained essentially calm with 0 3 eruptions 100 years but showing periodic activity with repose times of 1000 years all three volcanic systems experienced lulls in activity from 5 ka to 2 ka referred to as the mid holocene low this reduced eruption frequency appears to have resulted from a decrease in magma generation and delivery from the mantle plume rather than from changes in ice load glacier thickness in prehistoric time there was a time lag of 1000 3000 years between a peak of activity at volcanoes directly above the mantle plume versus at volcanoes located in the non rifting part of the eastern volcanic zone closer to the periphery of the island this time space relationship suggests that a significant future increase in volcanism can be expected there following increased levels of volcanism above the plume

paleotsunamis from the central kuril islands segment of the japan kuril kamchatka subduction zone abstract paleotsunami records from the central kuril island segment of the japan kuril kamchatka subduction zone indicate that the region has been frequently inundated by tsunamis as many as 20 22 tsunami deposits are recognized on matua island for the past 3300 yr with an average tsunami recurrence interval of 150 yr and 34 36 tsunami deposits are evident on simushir island for the past 2350 yr with an average recurrence of 65 yr these intervals are short but comparable to other segments of the japan kuril kamchatka subduction zone results from all survey locations reveal shortening recurrence intervals toward the present especially for the last 600 yr indicating a possible preservation bias on simushir tsunamis at least 11 m higher than the modern tsunamis in 2006 and 2007 occurred every 300 yr on average on matua tsunamis with slightly farther inundation than the 2006 and 2007 tsunamis occurred every 215 yr while those with at least 100 m farther inland inundation occur every 750 yr our paleotsunami record almost certainly includes tsunamis that are not from great subduction zone earthquakes in the central kuril segment we expect the matua record includes volcanic tsunamis and the simushir record includes tsunamis from the southern kuril segment

localized subduction of anthropogenic carbon dioxide in the southern hemisphere oceans the southern ocean makes a substantial contribution to the oceanic carbon sink observationally based estimates of carbon subduction suggest that carbon sequestration depends on physical properties such as mixed layer depth ocean currents wind and eddies that are potentially sensitive to climate variability and change

a continuous 5300 yr holocene cryptotephrostratigraphic record from northern new zealand and implications for tephrochronology and volcanic hazard assessment a continuous 5280 calendar cal yr long cryptotephrostratigraphic record of a peat core from northern new zealand demonstrates that cryptotephra studies can enhance conventional tephra records by extending the known distribution of ash fall and enabling re assessment of volcanic hazards a systematic sampling strategy was used to locate peaks in glass shard concentrations and to determine loci of individual geochemical populations and a palynological method involving spiking samples with lycopodium spores was adapted to facilitate accurate counting of glass shard concentrations using glass shard major element compositions and a core chronology based on eight ams 14c ages and two visible macroscopic tephra layers taupo tephra unit y 1688 1748 cal bp and tuhua tephra 6800 7230 cal bp 2cr age ranges four cryptotephras were correlated with known eruptions whakaipo unit v 2743 2782 cal bp stent unit q 4240 4510 cal bp and unit k 4970 5290 cal bp erupted from taupo volcanic ce

correlating tephras and cryptotephras using glass compositional analyses and numerical and statistical methods review and evaluation abstract we define tephras and cryptotephras and their components mainly ash sized particles of glass crystals in distal deposits and summarize the basis of tephrochronology as a chronostratigraphic correlational and dating tool for palaeoenvironmental geological and archaeological research we then document and appraise recent advances in analytical methods used to determine the major minor and trace elements of individual glass shards from tephra or cryptotephra deposits to aid their correlation and application protocols developed recently for the electron probe microanalysis of major elements in individual glass shards help to improve data quality and standardize reporting procedures a narrow electron beam diameter 3 5 m can now be used to analyze smaller glass shards than previously attainable reliable analyses of microshards defined here as glass shards in part 2 of the review we describe critically assess and recommend ways in which tephras or cryptotephras can be correlated in conjunction with other information using numerical or statistical analyses of compositional data statistical methods provide a less subjective means of dealing with analytical data pertaining to tephra components usually glass or crystals phenocrysts than heuristic alternatives they enable a better understanding of relationships among the data from multiple viewpoints to be developed and help quantify the degree of uncertainty in establishing correlations in common with other scientific hypothesis testing it is easier to infer using such analysis that two or more tephras are different rather than the same adding stratigraphic chronological spatial or palaeoenvironmental data i e multiple criteria is usually necessary and allows for more robust correlations to be made a two stage approach is useful the first focussed on differences in the mean composition of samples or their range which can be visualised graphically via scatterplot matrices or bivariate plots coupled with the use of statistical tools such as distance measures similarity coefficients hierarchical cluster analysis informed by distance measures or similarity or cophenetic coefficients and principal components analysis pca some statistical methods cluster analysis discriminant analysis are referred to as machine learning in the computing literature the second stage examines sample variance and the degree of compositional similarity so that sample equivalence or otherwise can be established on a statistical basis this stage may involve discriminant function analysis dfa support vector machines svms canonical variates analysis cva and anova or manova or its two sample special case the hotelling two sample t2 test randomization tests can be used where distributional assumptions such as multivariate normality underlying parametric tests are doubtful compositional data may be transformed and scaled before being subjected to multivariate statistical procedures including calculation of distance matrices hierarchical cluster analysis and pca such transformations may make the assumption of multivariate normality more appropriate a sequential procedure using mahalanobis distance and the hotelling two sample t2 test is illustrated using glass major element data from trachytic to phonolitic kenyan tephras all these methods require a broad range of high quality compositional data which can be used to compare unknowns with reference training sets that are sufficiently complete to account for all possible correlatives including tephras with heterogeneous glasses that contain multiple compositional groups currently incomplete databases are tending to limit correlation efficacy the development of an open online global database to facilitate progress towards integrated high quality tephrostratigraphic frameworks for different regions is encouraged

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

improved age modelling and high precision age estimates of late quaternary tephras for accurate palaeoclimate reconstruction abstract the role of tephrochronology as a dating and stratigraphic tool in precise palaeoclimate and environmental reconstruction has expanded significantly in recent years the power of tephrochronology rests on the fact that a tephra layer can stratigraphically link records at the resolution of as little as a few years and that the most precise age for a particular tephra can be imported into any site where it is found in order to maximise the potential of tephras for this purpose it is necessary to have the most precise and robustly tested age estimate possible available for key tephras given the varying number and quality of dates associated with different tephras it is important to be able to build age models to test competing tephra dates recent advances in bayesian age modelling of dates in sequence have radically extended our ability to build such stratigraphic age models as an example of the potential here we use bayesian methods now widely applied to examine the dating of some key late quaternary tephras from italy these are the agnano monte spina tephra amst the neapolitan yellow tuff nyt and the agnano pomici principali app and all of them have multiple estimates of their true age further we use the bayesian approaches to generate a revised mixed radiocarbon varve chronology for the important lateglacial section of the lago grande monticchio record as a further illustration of what can be achieved by a bayesian approach with all three tephras we were able to produce viable model ages for the tephra validate the proposed 40 ar 39 ar age ranges for these tephras and provide relatively high precision age models the results of the bayesian integration of dating and stratigraphic information suggest that the current best 95 confidence calendar age estimates for the amst are 4690 4300 cal bp the nyt 14320 13900 cal bp and the app 12380 12140 cal bp

trenching studies of active faults in kamchatka eastern russia palaeoseismic tectonic and hazard implications the central part of the kamchatka peninsula is characterized by a well defined depression associated with active volcanism aligned ne sw on the east the depression is bounded by a prominent system of active faults known as the east kamchatka fault zone ekfz in order to improve understanding of the behaviour and kinematic role of this fault zone a fieldwork programme including study of trenches was conducted in the north central part of this system aerial photograph analysis ground truthed indicates a westward fault dip with predominantly normal slip while lateral offsets of river terraces and stream channels demonstrate a combined dextral component over 20 excavated pits and natural exposures were examined to confirm a detailed tephra succession extending from the early holocene to recent historic eruptions this chronological framework then provided age control on five past faulting events recognised in three trenches these events took place at about 10 5 6 0 4 5 and in a two event succession within a short time span at 3 3 3 2 ka bp event clustering may be characteristic and fault length displacement values suggest earthquakes of m6 5 thus representing a significant new element in regional seismic hazard evaluations additional to events generated at the subduction interface the relatively long gap in faulting since the two most recent events may also be significant for hazard scenarios and there is a possible link between the faulting and volcanic activity in the depression overall the ekfz together with the nachiki transverse zone farther south is thought to define a regional scale block that is extending eastwards independently from the rest of kamchatka

tephrochronological investigation at dvuh yurtochnoe lake area kamchatka numerous landslides and lake tsunami and their environmental impacts distal volcanic tephras in soil sections and lake sediments in the dvuh yurtochnoe two yurts lake area central kamchatka were investigated in order to provide a chronological framework for the reconstruction of late quaternary landscape development mineralogical and geochemical data point to sources from 5 volcanoes ten tephra layers were identified and correlated to known eruptive events the ages were corroborated by radiocarbon dating of the soil sections around two yurts lake these findings allow the reconstruction of regional paleoenvironmental change recorded in the soil sections around two yurts lake during the last glacial maximum lgm time the area was affected by glacial advances that produced the glacial moraines at the eastern outlet of the lake a large landslide ca 15 000 18 000 14c bp dammed the valley and led to formation of two yurts lake several more landslide events can be recognized in the holocene and one affected two yurts lake ca 3000 14c bp this event produced a tsunami documented by poorly sorted deposits with rounded pebbles in the onshore sections around the lake in contrast to the soil sections tephras buried in the soupy lacustrine sediments of two yurts lake are not well preserved and show inconsistent age depth relationships compared to those suggested by radiocarbon dating due to sinking through the lake sediments nevertheless tephrochronological data revealed the strong impact of terrestrial landslides on lake sedimentation

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