combining local and remote infrasound recordings from the 2009 redoubt volcano eruption abstract the explosive phase of the 2009 redoubt volcano eruption produced predominantly short duration high amplitude infrasound signals recorded up to 4500 km away all 19 numbered explosive events were recorded at a local microphone dfr 12 km as well as at an infrasound array in fairbanks alaska i53us 547 km most with high signal to noise ratios the local microphone provides an estimate of the source parameters and comparison between the two datasets allows the unique opportunity to evaluate acoustic source term estimation at a remote array high waveform similarity between dfr and i53us occurs during much of the explosive phase due to strong stratospheric ducting permitting accurate source constraints inferred from i53us data cross correlation analysis after applying a hilbert transform to the i53us data shows how the acoustic energy has passed through a single caustic as predicted by ray theory similar to previous studies significant low frequency infrasound from redoubt recorded at i53us is coincident with high altitude ash emissions the largest events also produced considerable energy at greater than 50 s periods likely related to the initial oscillations of the volcanic plume or jet many of the explosive events have emergent onsets somewhat unusual for explosive short duration eruptions comparison of the satellite derived so2 emissions with the relative amount of acoustic energy at i53us shows a very high statistically significant correlation this study reiterates the utility of using remote infrasound arrays for detection of hazardous emissions and characterization of large volcanic eruptions and demonstrates how under typical meteorological conditions remote infrasound arrays can provide an accurate representation of the acoustic source

boron isotopes and b ca in benthic foraminifera proxies for the deep ocean carbonate system abstract accurate records of the state of the ocean carbonate system are critical for understanding past changes in pco 2 ocean acidification and climate the chemical principles underlying the proxy of oceanic ph provided by the boron isotope ratio of foraminiferal carbonate are relatively well understood but the proxy s reliability has been questioned we present 76 new multi collector inductively coupled plasma mass spectrometry mc icpms 11 b measurements on a range of benthic foraminifera from 23 late holocene samples from the atlantic that reaffirm the utility of the 11 b ph proxy our boron isotope measurements on 10 benthic foraminifera tests typically yield a precision of 0 25 at 2 s d equivalent to 0 03 ph units 11 b values of epifaunal species are within analytical uncertainty of those predicted from a simple model assuming sole incorporation of b oh 4 from seawater and no vital effects using the independently determined fractionation factor of 1 0272 between 11 b 10 b of aqueous boron species infaunal foraminifera are consistent with this model but record the combined effects of lower pore water 11 b and ph no influence of partial dissolution or shell size on 11 b is observed we have also measured the b ca ratios of the same samples for individual cibicidoides species b ca shows a good correlation with co 3 2 but the b ca of different co occurring species morphotypes varies considerably these effects are not seen in 11 b which may therefore provide a more robust proxy of the ocean carbonate system whilst in theory 11 b and b ca can be combined to provide a quantitative reconstruction of alkalinity and dissolved inorganic carbonate dic in practice this is precluded by propagated uncertainties 11 b data give significant constraints on foraminifera calcification mechanisms and seem most simply explained by incorporation of b oh 4 into a hco 3 pool which is then completely incorporated in foraminiferal caco 3 our demonstration of the predictable variation of 11 b with ph across a wide range of species and locations provides confidence in the application of mc icpms measurements of foraminiferal 11 b to reconstruct past changes in the ocean carbonate system

paragenesis of sodic pyroxene bearing quartz schists implications for the p t history of the sanbagawa belt sodic pyroxene jadeite content x jd 0 1 0 3 occurs locally as small inclusions within albite porphyroblasts and in the matrix of hematite bearing quartz schists in the sanbagawa sambagawa metamorphic belt central shikoku japan the sodic pyroxene bearing samples are characteristically free from chlorite and their typical mineral assemblage is sodic pyroxene subcalcic or sodic amphibole phengitic mica albite quartz hematite titanite epidote spessartine rich garnet occurs in mn rich samples sodic pyroxene in epidote bearing samples tends to be poorer in acmite content average x acm 0 26 0 50 than that in the epidote free samples x acm 0 45 0 47 x jd shows no systematic relationship to metamorphic grade and is different among the three sampling regions saruta gawa asemi gawa and bessi besshi the average x jd of the saruta gawa samples 0 21 0 29 is higher than that of the asemi gawa 0 13 0 17 and bessi 0 14 0 23 the p t conditions of the asemi gawa and bessi regions are estimated at 5 5 6 5 kbar 360 c in the chlorite zone 7 8 5 kbar 440 15 c in the garnet zone and 8 9 5 kbar 520 25 c in the albite biotite zone metamorphic pressure of the saruta gawa region is systematically 1 1 5 kbar higher than that of the asemi gawa and bessi regions and materials of the saruta gawa region have been subducted to a level 3 5 km deeper than materials that underwent metamorphism at equivalent temperatures and are now exposed in the asemi gawa and bessi regions pressure slightly increases toward the north structurally high levels through the sanbagawa belt of central shikoku two types of zonal structure were observed in relatively coarse grained sodic pyroxenes in the matrix one type is characterized by increasing x jd from core to rim the other type by decreasing x jd from core to rim both types of zoned pyroxenes show an increase in x fe 2 fe2 fe2 mg from core to rim the first type of zoning was observed in a sample from the chlorite zone of lowest grade whereas the latter occurs in the garnet and albite biotite zones of higher grade the contrast in zonal structure implies that dp dt during prograde metamorphism decreased with increasing metamorphic grade and may have been negative in some samples from the higher grade zones the estimated dp dt of the prograde stage of the chlorite zone is 3 2 kbar 100 c and that of the garnet and albite biotite zones is 1 8 to 0 9 kbar 100 c the variation of dp dt at shallow and deep levels of a subduction system probably reflects the difference of heating duration and or change in thermal gradient of the subduction zone by continuous cooling of the surrounding mantle

multiparametric observation of volcanic lightning sakurajima volcano japan we recorded volcanic lightning generated by vulcanian explosions at sakurajima volcano using a synchronized multiparametric array physical properties of lightning are related to plume dynamics and associated electromagnetic field variations are revealed by video observations high speed and normal speed together with infrasound and high sampling rate magnetotelluric signals data show that volcanic lightning at sakurajima mainly occurs in the plume gas thrust region at a few hundred meters above the crater rim where the overpressure of the turbulent volcanic jets determines the electrification of particles generating a complex charge structure in the growing plume organization of charges may be achieved at later stages when the plume transitions from the jet phase to the convective phase comparison with atmospheric sounding and maximum plume height data show that the effect of hydrometeors on flash generation at sakurajima is negligible and can be more prudently considered as an additional factor contributing to the electrification of volcanic plumes

accuracy of the lightning mapping array 1 the location accuracy of the new mexico tech lightning mapping array lma has been investigated experimentally using sounding balloon measurements airplane tracks and observations of distant storms we have also developed simple geometric models for estimating the location uncertainty of sources both over and outside the network the model results are found to be a good estimator of the observed errors and also agree with covariance estimates of the location uncertainties obtained from the least squares solution technique sources over the network are located with an uncertainty of 6 12 m rms in the horizontal and 20 30 m rms in the vertical this corresponds well with the uncertainties of the arrival time measurements determined from the distribution of chi square values to be 40 50 ns rms outside the network the location uncertainties increase with distance the geometric model shows that the range and altitude errors increase as the range squared r2 while the azimuthal error increases linearly with r for the 13 station 70 km diameter network deployed during steps the range and height errors of distant sources were comparable to each other while the azimuthal errors were much smaller the difference in the range and azimuth errors causes distant storms to be elongated radially in plan views of the observations the overall results are shown to agree well with hyperbolic formulations of time of arrival measurements e g proctor 1971 two appendices describe 1 the basic operation of the lma and the detailed manner in which its measurements are processed and 2 the effect of systematic errors on lightning observations the latter provides an alternative explanation for the systematic height errors found by boccippio et al 2001 in distant storm data from the lightning detection and ranging system at kennedy space center

assessing the impact of diagenesis on δ11b δ13c δ18o sr ca and b ca values in fossil planktic foraminiferal calcite the geochemical composition of foraminiferal tests is a valuable archive for the reconstruction of paleo climatic oceanographic and ecological changes however dissolution of biogenic calcite and precipitation of inorganic calcite overgrowth and recrystallization at the seafloor and in the sediment column can potentially alter the original geochemical composition of the foraminiferal test biasing any resulting paleoenvironmental reconstruction the 11b of planktic foraminiferal calcite is a promising ocean ph proxy but the effect of diagenesis is still poorly known here we present new 11b 13c 18o sr ca and b ca data from multiple species of planktic foraminifera from time equivalent samples for two low latitude sites clay rich tanzanian drilling project tdp site 18 from the indian ocean containing well preserved glassy foraminifera and carbonate rich ocean drilling program odp site 865 from the central pacific ocean hosting recrystallized frosty foraminifera our approach makes the assumption that environmental conditions were initially similar at both sites so most chemical differences are attributable to diagenesis planktic foraminiferal 18o and 13c records show offsets in both relative and absolute values between the two sites consistent with earlier findings that these isotopic ratios are strongly influenced by diagenetic alteration sr ca and b ca ratios in planktic foraminiferal calcite are also offset between the two sites but there is little change in the relative difference between surface and deep dwelling taxa in contrast 11b values indicate no large differences between well preserved and recrystallized foraminifera suggesting that despite extensive diagenetic alteration the 11b of biogenic calcite appears robust potentially indicative of a lack of free exchange of boron between pore fluids and the recrystallizing caco3 our finding may remove one potential source of uncertainty in 11b based ph reconstructions and provide us with greater confidence in our ability to reconstruct ph in the ancient oceans from at least some recrystallized foraminiferal calcite however further investigations should extend this approach to test the robustness of our findings across a range of taphonomies ages and burial settings

theory and observations of controls on lightning flash size spectra previous analyses of very high frequency vhf lightning mapping array lma observations relative to the location of deep convective updrafts have noted a systematic pattern in flash characteristics in and near strong updrafts flashes tend to be smaller and more frequent while flashes far from strong vertical drafts exhibit the opposite tendency this study quantitatively tests these past anecdotal observations using lma data for two supercell storms that occurred in oklahoma in 2004 the data support a prediction from electrostatics that frequent breakdown and large flash extents are opposed an energetic scaling that combines flash rate and flash area exhibits a 5 3 power law scaling regime on scales of a few kilometers and a maximum inflashenergyatabout10km thespectralshapeis surprisinglyconsistentacrossarangeofmoderatetolarge flash rates the shape of this lightning flash energy spectrum is similar to that expected of turbulent kinetic energy spectra in thunderstorms in line with the hypothesized role of convective motions as the generator of thunderstorm electrical energy the correspondence between kinematic and electrical energy spectra suggests that advection of charge bearing precipitation by the storm s flow including in turbulent eddies couples the electrical and kinematic properties of a thunderstorm

relative partitioning of acoustic and seismic energy during strombolian eruptions the relative elastic energy partitioning during strombolian eruptions can be estimated from acoustic pressure and seismic velocity records we outline methods for determining acoustic and seismic energies for sensors deployed within several kilometers of erupting vents we use these energies to introduce the concept of the volcano acoustic seismic ratio g or vasr which is the ratio of elastic energy propagated through the atmosphere and into the earth eruption vasr is a physical diagnostic of explosive degassing that is appropriate for comparing eruption mechanisms at individual and between various volcanoes here we assess acoustic and seismic energies and corresponding vasr for discrete strombolian explosive events at karymsky and erebus volcanoes we attribute the relatively high and stable vasr at erebus g 8 standard deviation 41 to repeatable source conditions occurring at the surface of a persistent lava lake with accompanying strong coupling to the atmosphere lower and more variable vasr at karymsky g 0 18 in 1998 to g 1 51 in 1991 with standard deviations of 93 and 313 respectively is attributed to changing conditions within a narrow partially choked conduit variable seismoacoustic energy partitioning for karymsky as manifested by the large vasr standard deviation suggests that conduit conditions affecting vasr which include magma properties conduit obstruction or fragmentation depths can evolve both during the course of an explosion and between successive events d 2005 elsevier b v all rights reserved

evaluation of the biogeochemical controls on b ca of globigerinoides ruber white from the oceanic flux program bermuda a b s t r a c t boron to calcium b ca ratios in planktonic foraminifera is suggested to be a proxy for the surface oceanic carbonate system the reliability of the proxy has been questioned due to conflicting reports from culture and sediment calibrations on the influence of temperature on b ca to assess this issue b ca and mg ca ratios and 18 ow ere measured in tests of the symbiont bearing surface dwelling planktonic foraminifer globigerinoides ruber white collected by the oceanic flux program ofp time series sediment traps located approximately 75 km se of bermuda b ca ratios in the 300 400 m size fraction of g ruber were approximately 10 20 higher than those in the 200 300 m size fraction in contrast mg ca ratios and 18 ov alues do not exhibit any relationship to test size which indicates that the size effect observed for b ca is not due to differences in depth habitat but to vital effects seasonal variation in the b ca ratio was similar in both size fractions and ranged by 20 30 mol mol this range is larger than that predicted by seasonal variations in seawater b oh hco the proposed boron species incorporated into planktonic foraminiferal calcite and indicates that b ca in g ruber is influenced by an additional variable s the seasonal cycle of b ca in g ruber white was more strongly correlated with light intensity than with temperature both observations suggest that the presence of symbionts in g ruber and seasonal variability in their photosynthetic activity act to modify the internal ph during calcification by up to 0 2u nits relative to ambient seawater 2014 elsevier b v all rights reserved

rapid and sustained surface ocean acidification during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm has been associated with the release of several thousands of petagrams of carbon pg c as methane and or carbon dioxide into the ocean atmosphere system within 10 kyr on the basis of the co occurrence of a carbon isotope excursion cie widespread dissolution of deep sea carbonates and global warming in theory this rapid carbon release should have severely acidified the surface ocean though no geochemical evidence has yet been presented using boron based proxies for surface ocean carbonate chemistry we present the first observational evidence for a drop in the ph of surface and thermocline seawater during the petm planktic foraminifers from a drill site in the north pacific ocean drilling program site 1209 show a 0 8 decrease in boron isotopic composition 11b at the onset of the event along with a 30 40 reduction in shell b ca similar trends in 11b are present in two lower resolution records from the south atlantic and equatorial pacific these observations are consistent with significant global acidification of the surface ocean lasting at least 70 kyr and requiring sustained carbon release the anomalies in the b records are consistent with an initial surface ph drop of 0 3 units at the upper range of model based estimates of acidification

volcanic plume electrification experimental investigation of a fracture charging mechanism although ashfall from particulate volcanic plumes is known to be highly electrically charged little is known about the charging mechanism we describe experiments designed to investigate the particle charges generated from the fracture of pumice small silicate particles were produced in the laboratory during collisions between two samples cut from pumice clasts the net charge magnitudes detected on these particles are similar to those previously measured on ashfall from volcanic plumes 10 5 to 10 6 c kg 1 this net charge is also shown to be the result of a small imbalance between the sums of individual particle charges of both polarities which are up to several orders of magnitude larger than the net charge the magnitude of both the net and single polarity specific charges were only weakly affected by changes of relative humidity but single polarity charges increased steadily with increasing sample impact velocities the dominant charging process during the experiments was that of material fracture the charging mechanism is thus interpreted to be fractoemission the release of nuclear particles from fresh crack surfaces occurring during the production of the silicate particles this implies that the electrification of volcanic plumes could be the result of brittle fragmentation of magma or pumice clasts within the upper regions of the conduit and in the jet region of the plume

character mass distribution and origin of tephra fall deposits from the 2009 eruption of redoubt volcano alaska highlighting the significance of particle aggregation abstract the 2009 eruption of redoubt volcano included 20 tephra producing explosions between march 15 2009 and april 4 2009 utc next generation radar nexrad data show that plumes reached heights between 4 6 km and 19 km asl and were distributed downwind along nearly all azimuths of the volcano explosions lasted between 0 8 mm thick including communities along the kenai peninsula 80 100 km and the city of anchorage 170 km trace ash on march 15 a small 4 6 km asl phreatic explosion containing minor non juvenile ash erupted through the summit ice cap the first five magmatic explosions events 1 5 occurred within a 6 hour period on march 23 plumes rose to heights between 5 5 km and 14 9 km asl during 2 to 20 minute duration explosions and were dispersed mainly along a nne trajectory trace ash fall was reported as far as fairbanks owing to a shift in wind direction and heavy snowfall during these events field discrimination among many of these layers was possible all deposits comprise a volumetrically significant amount of particle aggregates yet only event 5 deposits contain coarse clasts including glacier ice the most voluminous tephra fall was deposited on march 24 event 6 from a 15 minute explosion that sent a plume to 18 3 km asl and dispersed tephra to the wnw within 10 km of the vent this deposit contains 1 11 cm pumice clasts in a matrix of 1 2 mm aggregate lapilli a small dome was presumably emplaced between march 23 and march 26 and was subsequently destroyed during 1 14 minute magmatic explosions of events 7 8 march 26 that sent plumes between 8 2 km and 19 km asl ash fell along a broad swath to the ese covering communities along the kenai peninsula with up to 1 mm of ash proximal deposits are largely composed of aggregate lapilli of 1 2 mm with very little coarse juvenile material events 9 18 march 27 sent plumes between 5 2 km and 15 5 km asl during particle size data showing a preponderance of fine ash even in the most proximal locations along with the abundance of aggregate lapilli documented in most samples confirms that particle aggregation played a significant role in the 2009 eruption and induced premature fallout of fine ash

a gps based three dimensional lightning mapping system initial observations in central new mexico a gps based system has been developed that accurately locates the sources of vhf radiation from lightning discharges in three spatial dimensions and time the observations are found to reflect the basic charge structure of electrified storms observations have also been obtained of a distinct type of energetic discharge referred to as positive bipolar breakdown recently identified as the source of trans ionospheric pulse pairs tipps observed by satellites from space the bipolar breakdown has been confirmed to occur between the main negative and upper positive charge regions of a storm and found to be the initial event of otherwise normal intracloud discharges the latter is contrary to previous findings that the breakdown appeared to be temporally isolated from other lightning in a storm peak vhf radiation from the energetic discharges is observed to be typically 30 db stronger than that from other lightning processes and to correspond to source power in excess of 100 kw over a 6 mhz bandwidth centered at 63 mhz

areal extent of eclogite facies metamorphism in the sanbagawa belt japan new evidence from a raman microprobe study of quartz residual pressure application of raman spectrometry to determine residual pressure retained by quartz grains sealed in garnet reveals significant differences between eclogite facies rocks and lower grade schistose rocks of the sanbagawa metamorphic belt in central shikoku japan garnet in the eclogitic lithologies commonly exhibits two chemically distinct growth stages the inner segment commonly includes quartz grains with higher residual pressures than those in the outer segment suggesting that the former represents prograde eclogite facies and the latter formed during exhumation regional variation of the quartz residual pressure suggests that the eclogite unit has a far greater extent than previously recognized and reveals a large pressure gap between the newly proposed eclogite and noneclogite units

observations of volcanic lightning during the 2009 eruption of redoubt volcano abstract observations of volcanic lightning during the eruption of redoubt volcano in march and april 2009 were made with the lightning mapping array during the eruption twenty three distinct episodes of volcanic lightning were observed electrical activity occurred as either a volcanic lightning storm with up to thousands of lightning discharges or as a weak electrical event with only a handful of lightning discharges during the volcanic lightning storms we observed two phases of electrical activity the explosive phase and the plume phase the explosive phase consisted of very small discharges on the order of 10 100 m occurring directly above the vent while an explosive eruption was ongoing whereas the plume phase was comprised of discharges occurring throughout the plume subsequent to the explosive eruption the area of discharges during the explosive phase ranged from less than 1 km2 to 50 km2 or more the electrical activity at the beginning of the plume phase was dominated by small discharges over time the horizontal extent of the flashes increased with the largest flashes occurring at the end of the plume phase the distribution of the horizontal size of the discharges over the lifetime of the storm indicate that the charge structure of the plume evolved from a complex and clumpy structure to a more simple horizontally stratified structure plume height was shown to be a key factor in the quantity of lightning in a storm the volcanic lightning storms occurred in plumes with column heights greater than 10 km the tall plumes may contribute to the efficiency of charge generation through ice collisions by providing strong updrafts from the large thermal energy input from the eruption

inferring compressible fluid dynamics from vent discharges during volcanic eruptions observations at numerous volcanoes reveal that eruptions are often accompanied by continual radio frequency crf emissions the source of this radiation however has remained elusive until now through experiments and the analysis of field data we show that crf originates from proximal discharges driven by the compressible fluid dynamics associated with individual volcanic explosions blasts produce flows that expand supersonically generating regions of weakened dielectric strength in close proximity to the vent as erupted materialcharged through fragmentation friction or other electrification processtransits through such a region pyroclasts remove charge from their surfaces in the form of small interparticle spark discharges or corona discharge discharge is maintained as long as overpressured conditions at the vent remain beyond describing the mechanism underlying crf we demonstrate that the magnitude of the overpressure at the vent as well as the structure of the supersonic jet can be inferred in real time by detecting and locating crf sources

influence of solution chemistry on the boron content in inorganic calcite grown in artificial seawater abstract the ratio of boron to calcium b ca in marine biogenic carbonates has been proposed as a proxy for properties of seawater carbonate chemistry applying this proxy to planktic foraminifera residing in the surface seawater largely in equilibrium with the atmosphere may provide a valuable handle on past atmospheric co 2 concentrations however precise controls on b ca in planktic foraminifera remain enigmatic because it has been shown to depend on multiple physicochemical seawater properties to help establish a firm inorganic basis for interpreting the b ca records we examined the effect of a suite of chemical parameters ca 2 ph dic salinity and po 4 3 on b ca in inorganic calcite precipitated in artificial seawater these parameters were primarily varied individually while keeping all others constant but we also tested the influence of ph and dic at a constant calcite precipitation rate r by concurrent ca 2 adjustments in the simple ca 2 ph and dic experiments both r and b ca increased with these parameters in the ph ca 2 and dic ca 2 experiments at constant r on the other hand b ca was invariant at different ph and decreased with dic respectively these patterns agree with the behavior of solution b total dic ratio such that at a fixed b total it is independent of ph but decreases with dic based on these results r and b total dic ratio appear to be the primary controls on b ca in inorganic calcite suggesting that both b oh 4 and b oh 3 are possibly involved in b incorporation moreover b ca modestly increased with salinity and po 4 3 inorganic calcite precipitated at higher r and in the presence of oxyanions such as so 4 2 and po 4 3 in growth solutions often undergoes surface roughening due to formation of crystallographic defects vacancies and occasionally amorphous hydrous caco 3 these non lattice sites may provide additional space for b particularly b oh 3 consequently besides the macroscopic influence of r and bulk solution chemistry molecular scale processes associated with calcite nucleation can be an important consideration for b incorporation especially in complex ionic solutions lastly the covariance of b ca with dic and salinity observed here qualitatively agrees with those in planktic foraminifers it follows that their impact on foraminiferal b ca is partly inorganically driven which may explain why the effect is evident across different species

controls on boron incorporation in cultured tests of the planktic foraminifer orbulina universa culture experiments with living planktic foraminifers reveal that the ratio of boron to calcium b ca in orbulina universa increases from 56 to 92 mol mol 1 when ph is raised from 7 61 0 02 to 8 67 0 03 total scale across this ph range the abundances of carbonate bicarbonate and borate ions also change 530 500 and 170 mol kg 1 respectively thus specific carbonate system control s on b ca remain unclear complicating interpretation of paleorecords b ca in cultured o universa also increases with salinity 55 72 mol mol 1 from 29 9 35 4 and seawater boron concentration 62 899 mol mol 1 from 4 40 ppm b suggesting that these parameters may need to be taken into account for paleorecords spanning large salinity changes 2 and for samples grown in seawater whose boron concentration b sw differs from modern by more than 0 25 ppm while our results are consistent with the predominant incorporation of the charged borate species boh4 into foraminiferal calcite the behavior of the partition coefficient kd defined as b ca calcite boh4 hco3 seawater cannot be explained by borate incorporation alone and suggests the involvement of other ph sensitive ions such as co32 for a given increase in seawater boh4 the corresponding increase in b ca is stronger when boh4 is raised by increasing b sw than when it is raised by increasing ph these results suggest that b incorporation controls should be reconsidered additional insight is gained from laser ablation icp ms profiles which reveal variable b ca distributions within individual shells

core top calibration of b ca in pacific ocean neogloboquadrina incompta and globigerina bulloides as a surface water carbonate system proxy abstract practical methods for reconstructing past ocean carbonate chemistry are needed to study past periods of ocean acidification and improve understanding of the marine carbonate system s role in the global climate cycles planktic foraminiferal b ca may fill this role but requires better understanding and improved proxy calibrations we used pacific ocean core top sediments to generate new calibrations of the b ca proxy for past carbonate system parameters in two upwelling subpolar species of asymbiotic planktic foraminifera globigerina bulloides and neogloboquadrina incompta both species show significant positive correlation of b ca with calcite saturation calcite and carbonate ion concentration co 3 2 across a broad range of environmental conditions this suggests a calcification rate control on b ca incorporation as calcite regulates calcification rate in agreement with recent inorganic calcite studies this is also consistent with a surface entrapment model of trace element incorporation into caco3 in neither species is b ca significantly correlated with ph suggesting that ph does not directly regulate boron incorporation and that calculation of ph directly from foraminiferal b ca is not suitable correlations between b ca and b oh 4 b oh 4 hco3 and b oh 4 dic are weaker than with calcite boron partition coefficients k d b ca solid b oh 4 hco 3 seawater show little or no correlation with co32 or temperature and vary widely providing no support for application of kd to calculate carbonate system parameters from b ca we also discuss potential effects of depth related dissolution temperature and salinity on b ca these empirical calibrations linking foraminiferal calcite b ca with calcite provide a strong tool for reconstructing the past ocean carbonate system and improve our understanding of the proxy s geochemical basis

local seismic and infrasound observations of the 2009 explosive eruptions of redoubt volcano alaska article i nfo local seismic and infrasound data are used to characterize the march april 2009 eruptions of redoubt volca no alaska data are from a network of ten seismic stations ranging from 2 6 to 21 km from the vent and a single infrasound sensor 12 2 km from the vent measurements were made for more than 30 explosive erup tions including the 19 numbered events that were identified during the eruption response more than 30 smaller explosions were also identified measured parameters include onset time duration reduced dis placement dr pressure seismic energy and acoustic energy results were compared with complementary gas and lightning data based on ratios of pressure to dr and acoustic to seismic energy we find that the initial group of explosive eruptions on 23 24 march was relatively stronger seismically and included the four highest dr values we infer that these represent vent enlargement or stronger coupling between the magma and wall rocks one event at 12 31 ut on 23 march had an extremely high pressure of 250 pa for the initial pulse and was likely weakly seismically coupled a second group of explosive eruptions on 27 29 march was relatively stronger acoustically deposits were finer grained and of different lithology with less scoria and more dense clasts these two groups may represent different modes of gas release cumulative acoustic energy as a function of time correlates well with comparable lightning and so2 data suggesting that all three provide insight regarding different factors of gas release for the eruption as a whole the number of events identified depends on criteria measured and depends on the goals of the investigations overall the eruptions were substantially stronger than recent eruptions in alaska with some durations exceeding 1 h and pressures an order of magnitude higher

did ice charging generate volcanic lightning during the 2016 2017 eruption of bogoslof volcano alaska the 2016 2017 shallow submarine eruption of bogoslof volcano in alaska injected plumes of ash and seawater to maximum heights of 12 km more than 4550 volcanic lightning strokes were detected by the world wide lightning location network wwlln and vaisala s global lightning dataset gld360 over 9 months lightning assisted monitoring efforts by confirming ash producing explosions in near real time but only 32 out of the 70 explosive events produced detectable lightning what led to electrical activity within some of the volcanic plumes but not others and why did the lightning intensity wax and wane over the lifetime of individual explosions we address these questions using multiparametric observations from ground based lightning sensors satellite imagery photographs acoustic signals and 1d plume modeling detailed time series of monitoring data show that the plumes did not produce detectable lightning until they rose higher than the atmospheric freezing level approximated by 20 c temperatures for example on 28 may 2017 event 40 the delayed onset of lightning coincides with modeled ice formation in upper levels of the plume model results suggest that microphysical conditions inside the plume rivaled those of severe thunderstorms with liquid water contents 5 g m 3 and vigorous updrafts 40 m s 1 in the mixed phase region where liquid water and ice coexist based on these findings we infer that thunderstorm style collisional ice charging catalyzed the volcanic lightning however charge mechanisms likely operated on a continuum with silicate collisions dominating electrification in the near vent region and ice charging taking over in the upper level plumes a key implication of this study is that lightning during the bogoslof eruption provided a reliable indicator of sustained ash rich plumes and associated hazards above the atmospheric freezing level

the universal ratio of boron to chlorinity for the north pacific and north atlantic oceans abstract we report seawater boron concentration mg kg 1 and chlorinity values measured in seawater samples n 139 collected at various depths in the north pacific and north atlantic oceans and the east japan sea located in the western temperate north pacific our results indicate that variations in seawater boron concentration are strongly coupled to variations in chlorinity and salinity yielding a mean boron to chlorinity ratio of 0 2414 0 0009 mg kg 1 1 boron to salinity ratio 0 1336 0 0005 mg kg 1 1 this ratio was surprisingly universal throughout the water column in the three marine basins and across widely different ocean surface regimes but differs from the generally accepted ratio of 0 232 0 005 mg kg 1 1 determined by uppstrom 1974 which was based on only 20 measurements at four sites in the tropical pacific ocean in converting total alkalinity to carbonate alkalinity and vice versa for thermodynamic calculations the difference between these two ratios leads to a difference of 5 mol kg 1 in estimates for ocean surface waters where the contribution of borate to total alkalinity is typically greatest we suggest the use of the new boron to chlorinity ratio for predicting seawater boron concentrations using chlorinity or salinity data

evaluating the utility of b ca ratios in planktic foraminifera as a proxy for the carbonate system a case study of globigerinoides ruber b ca ratios in foraminifera have attracted considerable scientific attention as a proxy for past ocean carbonate system however the carbonate system controls on b ca ratios are not straightforward with inline image inline image in situ inline image at saturation correlating best with b ca ratios in benthic foraminifera rather than ph inline image or inline image as a simple model of boron speciation in seawater and incorporation into caco3 would predict furthermore culture experiments have shown that in planktic foraminifera properties such as salinity and b sw can have profound effects on b ca ratios beyond those predicted by simple partition coefficients here we investigate the controls on b ca ratios in g ruber via a combination of culture experiments and core top measurements and add to a growing body of evidence that suggests b ca ratios in symbiont bearing foraminiferal carbonate are not a straightforward proxy for past seawater carbonate system conditions we find that while b ca ratios in culture experiments covary with ph in open ocean sediments this relationship is not seen in fact our b ca data correlate best with inline image a previously undocumented association and in most regions salinity these findings might suggest a precipitation rate or crystallographic control on boron incorporation into foraminiferal calcite regardless our results underscore the need for caution when attempting to interpret b ca records in terms of the ocean carbonate system at the very least in the case of mixed layer planktic foraminifera

deep time foraminifera mg ca paleothermometry nonlinear correction for secular change in seawater mg ca 1 the mg ca ratio of foraminifera tests is increasingly being utilized as a paleotemperature proxy deep time pre pleistocene mg ca paleothermometry is complicated by the fact that the mg ca ratio of seawater mg casw has undergone considerable secular variation over the cenozoic previous studies have corrected for this by assuming an invariant mg distribution coefficient dmg with mg casw more recent laboratory culturing has shown that this is not the case demonstrating that a power relationship best describes the variation in test mg ca mg catest with mg casw therefore previous corrections are likely to have led to inaccurate temperature reconstructions here we show how the systematics of such a correction should be applied and demonstrate why this provides good evidence that the mg ca ratio of paleogene seawater was lower than previously implied by foraminiferal constraints in agreement with the majority of the proxy mg casw evidence we also demonstrate how it is indirectly possible to constrain the value of h the power component of a mg catest mg casw calibration potentially enabling the appropriate correction of results derived from species where this relationship has not been calibrated however this technique should not be treated as a substitute for culturing the previous erroneous assumptions regarding both 1 the relationship between mg catest and mg caswand 2 the mg ca ratio of seawater at a given time in the past may counteract each other to differing extents as a result previous absolute pre pleistocene paleotemperature estimates derived from mg ca ratios in foraminifera should be treated with caution although relative temperature changes over short 1 ma timescales are likely to be reliable

using lightning observations as a volcanic eruption monitoring tool lightning commonly occurs in the eruption columns produced by explosive volcanic eruptions there are several different kinds of lightning detection instruments that could be employed to help monitor volcanoes each with their own advantages and disadvantages very low frequency vlf instruments have the ability to detect lightning at long ranges but tend to have low sensitivity due to network geometry and typically can provide only the time and 2 d location of a cloud to ground return stroke or similar high amplitude pulse produced by an intracloud discharge low frequency lf and medium frequency mf instruments typically have more sensitivity than a vlf network but can only be used for detection on a regional scale very high frequency vhf lightning mapping instruments also provide only regional coverage but detect all lightning within their range during the 2009 eruption of redoubt volcano alaska usa each of these types of instruments detected lightning from redoubt s ash plume the vhf system consistently detected lightning before the other two during each distinct explosive event and also detected more lightning than the others by one or two orders of magnitude lightning observations could be used to confirm and in some cases detect explosive volcanic activity the rapid response provided by lightning monitoring is a valuable tool for fast identification of potentially hazardous ash clouds

the major ion composition of cenozoic seawater the past 36 million years from fluid inclusions in marine halite fluid inclusions from ten cenozoic eocene miocene marine halites are used to quantify the major ion composition mg2 ca2 k na so42 and cl of seawater over the past 36 my criteria used to determine a seawater origin of the halites include 1 stratigraphic sedimentologic and paleontologic observations 2 br in halite 3 34s of sulfate minerals 4 87sr 86sr of carbonates and sulfates and 5 fluid inclusion brine compositions and evaporation paths which must overlap from geographically separated basins of the same age to confirm a global seawater chemical signal changes in the major ion chemistry of cenozoic seawater record the end of a systematic long term 150 my shift from the ca2 rich mg2 and so42 poor seawater of the mesozoic cacl2 seas to the mgso4 seas with higher mg2 and so42 ca2 of the cenozoic the major ion composition of cenozoic seawater is calculated for the eocene oligocene 36 34 ma serravallian tortonian 13 5 11 8 ma and the messinian 6 5 ma assuming chlorinity 565 mmolal salinity and the k concentration 11 mmolal are constant and the same as in modern seawater fluid inclusions from cenozoic marine halites show that the concentrations of mg2 and so42 have increased in seawater over the past 36 my and the concentration of ca2 has decreased mg2 concentrations increased from 36 mmolal in eocene oligocene seawater 36 34 ma to 55 mmolal in modern seawater the mg2 ca2 ratio of seawater has risen from 2 3 at the end of the eocene to 3 4 and 4 0 respectively at 13 5 to 11 8 ma and 6 to 5 ma and to 5 in modern seawater eocene oligocene seawater 36 34 ma has estimated ranges of so42 14 23 mmolal and ca2 11 20 mmolal if the ca2 so42 product is assumed to be the same as in modern seawater 300 mmolal2 eocene oligocene seawater had ca2 16 mmolal and so42 19 mmolal the same estimates of ca2 and so42 for serravallian tortonian seawater 13 5 11 8 ma are so42 19 27 mmolal and ca2 8 16 mmolal and so42 24 mmolal and ca2 13 mmolal if the ca2 so42 product is equal to that in modern seawater messinian seawater has an estimated range of so42 21 29 mmolal and ca2 7 15 mmolal with so42 26 mmolal and ca2 12 mmolal assuming the ca2 so42 product is equal to that in modern seawater regardless of the estimation procedure so42 shows progressively increasing concentrations from 36 ma to the present values which are the highest of the cenozoic

obliteration of olivine crystallographic preferred orientation patterns in subduction related antigorite bearing mantle peridotite an example from the higashi akaishi body sw japan

role of nappe boundaries in subduction related regional deformation spatial variation of meso and microstructures in the seba eclogite unit the sambagawa belt sw japan abstract the seba eclogite unit of the sambagawa high p t metamorphic belt has a kilometre scale synformal structure and its base is the boundary between an overlying eclogite nappe and an underlying non eclogitic nappe the formation of the nappe boundary is related to a phase of strong penetrative ductile deformation d a spatial variations of meso and microstructures of schistose eclogite in the seba unit reveal that there is i a decreasing intensity of d a and ii a time dependent widening of the d a shear zone away from the nappe boundary these features indicate that the nappe boundary behaved as a core zone during the d a phase and furthermore that development of the regional deformation d a is strongly controlled by the presence of the nappe boundary a new model is proposed where each phase of regional deformation in subduction type metamorphic belts is related to ancient activity of a particular nappe boundary in this model a single phase of deformation may be related to exhumation in one nappe and subduction in an adjacent one

a continental shelf perspective of ocean acidification and temperature evolution during the paleocene eocene thermal maximum a rapid and large injection of isotopically light carbon into the ocean atmosphere reservoirs is signaled by a negative carbon isotope excursion cie at the paleocene eocene boundary 56 m y ago to better understand the extent of ocean warming and acidification associated with the carbon injection we generated elemental and isotopic records of surface and thermocline planktonic foraminifera across the paleocene eocene boundary from an expanded section along the mid atlantic coastal plain new jersey usa ocean temperatures derived from magnesium calcium paleothermometer document a lag in thermocline warming relative to surface waters implying a progressive deepening of the mixed layer in addition to global warming a similar magnitude of acidification as recorded by boron calcium b ca on the shelf compared with open ocean sites confirms widespread acidification of the surface ocean an increase in seawater alkalinity after the cie as recorded by b ca in planktonic foraminifera likely played an important role in neutralizing the added carbon possibly minimizing benthic extinction along the shelf

trace element proxies for surface ocean conditions a synthesis of culture calibrations with planktic foraminifera abstract the trace element composition of planktic foraminiferal calcite provides a useful means of determining past surface ocean conditions we have assembled the results of culture experiments for three species of symbiont bearing planktic foraminifera globigerinoides ruber globigerinoides sacculifer and orbulina universa and one symbiont barren species globigerina bulloides to evaluate their responses to temperature salinity ph carbonate ion and dissolved inorganic carbon dic growth conditions trace element ratios li ca b ca mg ca sr ca mn ca cd ca ba ca na ca and u ca were measured simultaneously on samples grown with the same culture techniques which provides robust relatable calibrations that may be used together in multi proxy paleoceanographic studies our data confirm that temperature is the dominant control on foraminiferal mg ca under the ranges of conditions studied and that the potential effects of salinity and co32 on mg ca of these tropical species across late pleistocene glacial cycles are relatively small carbonate system experiments suggest that sr ca may be useful for reconstructing large dic changes na ca increases with salinity in g ruber pink but not in g sacculifer as these emerging proxy relationships become more firmly established the synthesis of multiple trace element ratios may help paleoceanographers isolate the effects of different environmental parameters in paleo records calcification rates g day vary among species and do not respond consistently to any experimental parameter comparison of our calcification rates with those observed in inorganic calcite precipitation experiments suggest that foraminifera calcify 100 more slowly than inorganic calcites grown in similar solutions we suggest that calcification rate does not typically exert a dominant control on trace element partitioning in planktic foraminiferal calcite though it may play a role for some elements under certain circumstances differences in average growth rate cannot explain composition differences among species pointing to alternative controls that may be biological in origin

an overview of volcano infrasound from hawaiian to plinian local to global abstract volcano infrasound is an increasingly useful technique for detecting locating characterizing and quantifying eruptive activity and can be used to constrain eruption source parameters in recent years studies of infrasound data from active volcanoes have shown clear progress towards mitigating volcanic hazards and understanding volcanic source processes volcano acoustic sources are shallow or aerial thus volcano infrasound data provide valuable information on eruption dynamics and are readily combined with direct and remote observations of gas ash and other eruptive phenomena the infrasound signals produced by volcanoes are indicative of the eruption style and dynamics here we review the diversity of infrasound signals generated by a wide variety of volcanic eruptions from hawaiian to plinian and the physical processes inferred to produce them we place particular emphasis on regional 15 250 km distance and global 250 km distance volcano infrasound studies as recent work in this area has made significant advances in monitoring and characterizing remote and difficult to monitor eruptions long range infrasonic detection of explosive volcanic eruptions is possible due to the energetic source mechanisms involved minor atmospheric attenuation at low frequencies and the existence of waveguides in the atmosphere however accurate characterization of the atmosphere and its spatiotemporal variability is required for reliable long range sound propagation modeling and correct interpretation of global infrasound recordings conversely because volcanic explosions are energetic and sometimes repetitive infrasound sources they can be used to validate atmospheric and acoustic propagation models

a core top assessment of proxies for the ocean carbonate system in surface dwelling foraminifers we have assessed the reliability of several foraminifer hosted proxies of the ocean carbonate system 11b b ca and u ca using holocene samples from the atlantic and pacific oceans we examined chemical variability over a range of test sizes for two surface dwelling foraminifers globigerinoides sacculifer and globigerinoides ruber measurements of 11b in g ruber show no significant relationship with test size in either atlantic or pacific sites and appear to provide a robust proxy of surface seawater ph likewise there is no significant variability in the 11b of our atlantic core top g sacculifer but we find that 11b increases with increasing test size for g sacculifer in the pacific these systematic differences in 11b are inferred to be a consequence of isotopically light gametogenic calcite in g sacculifer and its preferential preservation during postdepositional dissolution the trace element ratio proxies of ocean carbonate equilibria u ca and b ca show systematic increases in both g ruber and g sacculifer with increasing test size possibly as a result of changing growth rates this behavior complicates their use in paleoceanographic reconstructions in keeping with several previous studies we find that mg ca ratios increase with increasing size fraction in our well preserved atlantic g sacculifer but not in g ruber in contrast to previous interpretations we suggest that these observations reflect a proportionally larger influence of compositionally distinct gametogenic calcite in small individuals compared to larger ones as with 11b this influences g sacculifer but not g ruber which has negligible gametogenic calcite

southward extrusion of eclogite bearing mafic ultramafic bodies in the sanbagawa belt central shikoku japan abstract several mafic rock masses which have experienced eclogite facies metamorphism are distributed in flat lying non eclogitic schists in an intermediate structural level thermal core of the sanbagawa belt the largest iratsu mass and an associated peridotite the higashi akaishi mass extend e w for about 8 km and n s for about 3 km and are surrounded by pelitic basic and quartz schists the iratsu mass consists of metabasites of gabbroic and basaltic origin with intercalations of ultramafic rocks felsic gneiss quartz schist and metacarbonate the iratsu mass can be divided into two layers along a wnw trending metacarbonate layer the higashi akaishi mass consists of peridotite with intercalations of garnet clinopyroxenite it is situated beneath the western half of the iratsu mass and their mutual boundary dips gently or steeply to the n or ne these masses underwent eclogite and subsequent epidote amphibolite facies metamorphism as has been reported elsewhere the iratsu higashi akaishi masses and the surrounding rocks underwent ductile deformation under epidote amphibolite facies or lower p t metamorphic conditions their foliation generally trends wnw and dips moderately to the nne and the mineral lineation mostly plunges to the n and ne in non eclogitic schists surrounding the iratsu higashi akaishi masses the foliation generally trends wnw and dips gently or steeply to the n or s and the mineral lineation mostly plunges to the nw n and ne kinematic analysis of deformation structures in outcrops and oriented samples has been performed to determine shear senses consistent top to the north normal fault displacements are observed in peridotite layers of the higashi akaishi mass and eclogite bearing epidote amphibolite layers of the iratsu mass top to the northeast or top to the northwest displacements also occur in non eclogitic pelitic quartz schists on the northern side of the iratsu mass in the structural bottom of the iratsu higashi akaishi masses and to the south reverse fault top to the south movements are recognized in serpentinized peridotite and non eclogitic schists these observations provide the following constraints on the kinematics of the rock masses 1 northward normal displacement of iratsu relative to higashi akaishi 2 northward normal displacement of non eclogitic schists on the north of the iratsu mass and 3 southward thrusting of the iratsu higashi akaishi masses upon non eclogitic schists in the south the exhumation process of the iratsu higashi akaishi masses can be explained by their southward extrusion

doppler weather radar observations of the 2009 eruption of redoubt volcano alaska abstract the u s geological survey usgs deployed a transportable doppler c band radar during the precursory stage of the 2009 eruption of redoubt volcano alaska that provided valuable information during subsequent explosive events we describe the capabilities of this new monitoring tool and present data captured during the redoubt eruption the minimax 250 c mm 250c radar detected seventeen of the nineteen largest explosive events between march 23 and april 4 2009 sixteen of these events reached the stratosphere above 10 km within 2 5 min of explosion onset high column and proximal cloud reflectivity values 50 to 60 dbz were observed from many of these events and were likely due to the formation of mm sized accretionary tephra ice pellets reflectivity data suggest that these pellets formed within the first few minutes of explosion onset rapid sedimentation of the mm sized pellets was observed as a decrease in maximum detection cloud height the volcanic cloud from the april 4 explosive event showed lower reflectivity values due to finer particle sizes related to dome collapse and related pyroclastic flows and lack of significant pellet formation eruption durations determined by the radar were within a factor of two compared to seismic and pressure sensor derived estimates and were not well correlated ash dispersion observed by the radar was primarily in the upper troposphere below 10 km but satellite observations indicate the presence of volcanogenic clouds in the stratosphere this study suggests that radar is a valuable complement to traditional seismic and satellite monitoring of explosive eruptions

structural and microstructural constraints on the mechanism of eclogite formation in the sambagawa belt sw japan abstract eclogites in the seba basic schist of the sambagawa belt show contrasting textures in one type of eclogite coarse grained omphacite is randomly oriented and cross cuts the schistosity suggesting post tectonic growth in contrast in the second type fine grained omphacite is preferentially aligned parallel to the schistosity suggesting pre to syn tectonic growth the former type of eclogite has been regarded as a product of solid state contact metamorphism after the formation of the schistosity while the latter type has been related to the sambagawa regional metamorphism the idea that eclogite can form by contact metamorphism is unconventional and if true could have major implications for the interpretation of eclogitic rocks in general in the seba basic schist it has generally been assumed that the dominant schistosity formed during a single phase of deformation however field and microstructural studies show i there are two different schistosities one formed before and the other during eclogite formation and ii the differences in eclogite texture reflect the strength of deformation during the second stage therefore the various textural types of eclogite in the seba basic schist all formed during a single phase of regional metamorphism and there is no need to invoke contact metamorphism

b ca in planktonic foraminifera as a proxy for surface seawater ph boron isotope systematics indicate that boron incorporation into foraminiferal caco3 is determined by the partition coefficient k d frac left rm b rm ca right rm caco3 left rm b left rm oh right 4 rm hco 3 right rm seawater and b oh 4 hco3 seawater providing in principle a method to estimate seawater ph and pco2 we have measured b ca ratios in globigerina bulloides and globorotalia inflata for a series of core tops from the north atlantic and the southern ocean and in globigerinoides ruber white from ocean drilling program odp site 668b on the sierra leone rise in the eastern equatorial atlantic b ca ratios in these species of planktonic foraminifera seem unaffected by dissolution on the seafloor k d shows a strong species specific dependence on calcification temperature which can be corrected for using the mg ca temperature proxy a preliminary study of g inflata from southern ocean sediment core chat 16k suggests that temperature corrected b ca was 30 higher during the last glacial correspondingly ph was 0 15 units higher and aqueous pco2 was 95 atm lower at this site at the last glacial maximum the covariation between reconstructed pco2 and the atmospheric pco2 from the vostok ice core demonstrates the feasibility of using b ca in planktonic foraminifera for reconstructing past variations in ph and pco2

model of seawater composition for the phanerozoic we present an inverse model of phanerozoic seawater com position calibrated against updated paleoseawater compositions from fluid inclusions in marine halites the model considers step wise alteration of seawater composition via 1 variable input of river water 2 variable rates of alteration of seawater through reactions at mid ocean ridges and 3 variable rates of alteration of seawater through reactions on ridge flanks and across the ocean floor in general the model achieves agreement with paleoseawater fluid inclusion data for na 1 c a 2 1 s o 4 2 2 and k 1 particularly when variable runoff is considered variable rates of basalt seawater interactions at both ridges and ridge flanks are required to understand the evolution of seawater particularly the observed near constant concentration of k 1 through time

evaluating the planktic foraminiferal b ca proxy for application to deep time paleoceanography abstract the cenozoic era has been characterized by large perturbations to the oceanic carbon cycle and global climatic changes but quantifying the magnitude and cause of these shifts is still subject to considerable uncertainty the boron calcium b ca ratio of fossil planktic foraminifera shells is a promising tool for reconstructing surface ocean carbonate chemistry during such events previous studies indicate that symbiont bearing planktic foraminiferal b ca depends on the b oh 4 dic ratio of seawater and potentially when combined with foraminiferal 11 b proxy reconstructions of b oh 4 an opportunity to reconstruct surface ocean dic in the geologic past there are however two barriers towards interpreting records from the pre pleistocene era 1 changes in seawater major ion chemistry in the past might have affected foraminiferal b ca and 2 modern foraminifera species show variable b ca calibration sensitivities that cannot be constrained in now extinct species here we address these challenges with new experiments in which we have cultured modern symbiont bearing foraminifera globigerinoides ruber pink and trilobatus sacculifer in seawater with simulated early cenozoic seawater chemistry high ca low mg and low b t we explore mechanisms that can account for the inter species trends that are observed in foraminiferal b ca and propose a framework that can be used to apply b ca calibrations to now extinct species for reconstructing climate perturbations under varying seawater chemistries

coupled evolution of temperature and carbonate chemistry during the paleocene eocene new trace element records from the low latitude indian ocean abstract the early paleogene represents the most recent interval in earth s history characterized by global greenhouse warmth on multi million year timescales yet our understanding of long term climate and carbon cycle evolution in the low latitudes and in particular the indian ocean remains very poorly constrained here we present the first long term sub eccentricity resolution stable isotope 13 c and 18 o and trace element mg ca and b ca records spanning the late paleocene early eocene 58 53 ma across a surface deep hydrographic reconstruction of the northern indian ocean resolving late paleocene 405 kyr paced cyclicity and a portion of the petm recovery our new records reveal a long term warming of 4 5 c at all depths in the water column with absolute surface ocean temperatures and magnitudes of warming comparable to the low latitude pacific as a result of warming we observe a long term increase in 18 o sw of the mixed layer implying an increase in net evaporation we also observe a collapse in the temperature gradient between mixed layer and thermocline dwelling species from 57 54 ma potentially due to either the development of a more homogeneous water column with a thicker mixed layer or depth migration of the morozovella in response to warming synchronous warming at both low and high latitudes along with decreasing b ca ratios in planktic foraminifera indicating a decrease in ocean ph and or increasing dissolved inorganic carbon suggest that global climate was forced by rising atmospheric co2 concentrations during this time

a re evaluation of eclogite facies metamorphism in sw japan proposal for an eclogite nappe known eclogite occurrences in the sanbagawa metamorphic belt of sw japan are dominantly in metagabbro bodies which have complex polyphase metamorphic histories these bodies are generally described as tectonic blocks and their relationship to the sanbagawa metamorphism is unclear new findings of foliated eclogite in the seba and kotsu areas show that eclogite facies metamorphism is much more widespread than generally thought evidence that the foliated eclogite units originated as lavas or sediments implies that these units can be treated as a high grade part of the subduction related sanbagawa metamorphism although separated by an along strike distance of 80 km the seba and kotsu eclogites have very similar garnet and omphacite compositions suggesting that they were formed under similar metamorphic conditions however differences in the associated retrograde assemblages epidote amphibolite in the seba unit and epidote blueschist in the kotsu unit suggest contrasting p t paths in both units the eclogite rocks occupy the highest structural level of the sanbagawa belt and overlie rocks metamorphosed at lower pressure the lower boundary to the eclogite units is therefore a major tectonic discontinuity locally decorated with lenses of exotic material these features can help trace the boundary into other areas the previously known outcrops of eclogite show enough similarities with the newly found areas to suggest that all the eclogite facies rocks in the sanbagawa belt constitute a single nappe that lies at the highest structural levels of the orogen

p t d path of eclogite from the sambagawa belt deduced from combination of petrological and microstructural analyses both structural and petrological data can be used to constrain the introduction p t path of an eclogitic schist unit the seba basic schist in the metamorphism of the sambagawa belt of sw japan was sambagawa belt of sw japan the relationships between these classified by miyashiro 1973 as an intermediate hightwo sets of data are well defined by porphyroblastic and other pressure facies series petrological chronological and microstructures the derived p t path for the seba basic schist structural data suggest that the evolution of the sambahas an overall clockwise trajectory with the decompression or gawa belt is in general compatible with the predictions exhumation related path taking place under a lower p t gradient made for metamorphism in the deeper parts of an acthan the burial or subduction related path the clockwise nature cretionary wedge e g banno sakai 1989 enami et of the p t path is qualitatively supported by chemical zoning of al 1994 takasu et al 1994 wallis 1998 the belt is amphibole coexisting with eclogitic minerals the significant feature composed mainly of metamorphosed sediments that have of the p t path is the presence of two temperature maxima the pelitic basic or siliceous compositions the mineral asfirst in the eclogite facies and the second in the epidote amphibolite semblages of most rocks are characteristic of metafacies the existence of two temperature maxima gives a simple morphism under greenschist blueschist or epidoteexplanation for the observation that metamorphic zonal boundaries amphibolite facies conditions however eclogite facies postdating the eclogite facies metamorphism cross cut the distribution mineral assemblages have also been reported e g takasu of the main eclogite bodies in the sambagawa belt estimates of 1989 which occur dominantly within metagabbro bodmetamorphic pressure using the jadeite content of clinopyroxene in ies most of these eclogite bearing bodies are located in the seba area demonstrate the existence of a tectonic discontinuity the besshi district fig 1 the estimated p t paths between the eclogitic schist and surrounding non eclogitic schist for the eclogite bearing bodies are distinct from those structural studies show that although these two units have experienced estimated for the surrounding epidote amphibolite grade very different peak metamorphic conditions they became juxtaposed rocks and show considerable variation amongst them

history of carbonate ion concentration over the last 100 million years abstract instead of having been more or less constant as once assumed it is now apparent that the major ion chemistry of the oceans has varied substantially over time for instance independent lines of evidence suggest that calcium concentration ca2 has approximately halved and magnesium concentration mg2 approximately doubled over the last 100 million years on the other hand the calcite compensation depth and hence the caco3 saturation has varied little over the last 100 my as documented in deep sea sediments we combine these pieces of evidence to develop a proxy for seawater carbonate ion concentration co32 over this period of time from the calcite saturation state which is proportional to the product of ca2 times co32 but also affected by mg2 we can calculate seawater co32 our results show that co32 has nearly quadrupled since the cretaceous furthermore by combining our co32 proxy with other carbonate system proxies we provide calculations of the entire seawater carbonate system and atmospheric co2 based on this reconstructed atmospheric co2 is relatively low in the miocene but high in the eocene finally we make a strong case that seawater ph has increased over the last 100 my

origin of eclogitic metagabbro mass in the sambagawa belt geological and geochemical constraints abstract eclogite bearing metagabbro masses in the high p t sambagawa metamorphic belt in sw japan have long been regarded as tectonic blocks derived from the mantle wedge or hanging wall side of the former sambagawa subduction zone the origin of one of the metagabbro masses the seba metagabbro is reexamined by i geological chemico structural study focusing on the relationship between this body and the surrounding metasedimentary schists and ii comparative major and trace element bulk chemistry with other gabbros metagabbros from the world the geological studies reveal the presence of a marginal shear zone that i is located between the enveloping pelitic schist and the central metagabbro ii has a bulk chemical composition intermediate between the two and iii shows up to 10 cm scale prominent mafic felsic banding based on the difficulty of forming such marginal shear zones by a tectonic block hypotheses and key field observations in neighboring regions indicating formation of the marginal shear zone as sediments the seba metagabbro is concluded to have originated on the ocean floor as an olistolith comparative bulk chemical studies show that sr content of the seba metagabbro is too high for gabbros derived from fracture zones associated with a spreading ridge a comparison with other eclogitic metagabbro masses in the sanbagawa belt reveals numerous similarities with the seba metagabbro this suggests all the metagabbro masses can be regarded as members of an olistostrome complex that subducted and underwent the eclogite facies metamorphism the eclogitic complex includes the western iratsu mass that is considered to be an ancient seamount this suggests that the metagabbro masses represent fragments of the ancient western iratsu seamount

surface water conditions and calcium carbonate preservation in the fram strait during marine isotope stage 2 28 8 15 4 kyr 1 we present a high resolution record of calcium carbonate preservation alongside the distribution pattern of planktic foraminifera from the fram strait the record covers the marine isotope stage mis 2 28 8 to 15 4 kyr including the last glacial maximum lgm and the early deglaciation in multidecadal temporal resolution the investigation is based on the distribution patterns of planktic foraminifera stable isotopes mean shell weight of neogloboquadrina pachyderma the degree of fragmentation of planktic shells caco3 content and geochemical and sedimentological data the dissolution proxies indicate long lasting periods of markedly reduced preservation of calcium carbonate at 28 8 27 2 24 1 23 2 and 16 6 15 4 kyr in addition to a number of short lasting periods 300 year during the lgm these periods are accompanied by a simultaneous and significant reduction in specimens of subpolar planktic foraminifera indicating a southward expansion of arctic surface water masses prolonged periods with high abundances of subpolar foraminiferal species and good preservation of calcium carbonate are attributed to increased influence of atlantic water masses which appears to persist throughout most of the mis 2 comparison to holocene mis 1 shell weight records shows that the preservation during mis 2 was overall better even during the events of dissolution this was probably a reflection of the low concentration of atmospheric co2 at the time

the higher grade metamorphic zonation of the sambagawa metamorphic belt in central shikoku japan the higher grade metamorphic zonation of the sambagawa sanbagawa belt is established for the first time for the whole area of central shikoku as discontinuous reactions to define the isograd are absent the metamorphic grade is primarily determined by the mg fe partitioning between garnet and chlorite along representative traverses however for regional mapping mineralogical features of the pelitic schists such as using mineral assemblages of more than divariant equilibrium the modal garnet to chlorite ratio and the optical properties of chlorite are employed as auxiliary criteria the presence of the highest grade mineral zone in the middle of the structural level is confirmed but its spatial distribution is far more complex than hitherto accepted thermal axes are now confirmed at three different structural levels a model is presented in which the stacking of thrust sheets of different grade took place while metamorphic reactions were in progress thermal readjustment brought a continuous metamorphic temperature gradient across and within the thrust sheets tectonic blocks of metagabbro and ultramafic rock were emplaced synchronously with thinning and subsequently also re equilibrated local anomalies of metamorphic grade represented by mixing of schists of different metamorphic grade exist but they are due to a later stage event

globally detected volcanic lightning and umbrella dynamics during the 2014 eruption of kelud indonesia abstract volcanic lightning shows considerable promise as a monitoring and research tool to characterize explosive eruptions its key strengths are rapid and remote detection because the radio signals produced by lightning can propagate thousands of km at the speed of light despite these tantalizing properties the scientific work on volcanic lightning has only recently started gaining momentum much more is needed to understand what lightning reveals about the evolution of an eruption in near real time here we examine the timing and energy release of lightning generated by the eruption of kelud volcano in indonesia on 13 february 2014 as detected by the world wide lightning location network wwlln the eruption column reached at least 26 km above sea level representing the highest plume since the advent of global lightning networks in the last decade therefore it provides valuable constraints on the electrification of end member sustained plinian columns we investigate the lightning in context with satellite images photographs and other published studies results show that the earliest satellite detected activity was a thermal anomaly at 15 46 utc corresponding to a directed blast at the onset of eruption and only a few lightning strokes following a brief pause the eruption produced a sustained column and umbrella cloud that spread outward into the tropical stratosphere rates of umbrella expansion provide an average mass eruption rate mer in the range of 8 107 1 108 kg s 1 a more nuanced picture emerges from the time varying mers determined between each satellite pass which show rapid intensification during the first hour of eruption followed by constant mer for about an hour and waning toward the end after 17 50 utc at this stage decreasing flux into the umbrella cloud coincides with column instability and formation of pyroclastic density currents as recorded by photos from the ground 17 45 utc we infer that some of the erupted mass partitioned into ground hugging currents leading to a lower apparent mer interestingly there is not a 1 1 correlation between lightning intensity and mer over the course of eruption stroke rates increase sharply within the first 30 40 min during rapid intensification of the plume and then drop below 2 strokes per min once the mer remains constant this suggests that electrification was controlled by the rate of increase in mer in other words the acceleration of particles out of the vent we also show that lightning stroke rates and energies are greatest within 50 km of the vent even when the ash cloud extends 200 km downwind indicating that lightning was focused in the regions of highest particle concentration and turbulence overall we conclude that abrupt changes in lightning rates are clearly linked to changes in eruption behavior and that rapid detection could aid monitoring efforts to characterize eruption rates or styles

the effects of secular calcium and magnesium concentration changes on the thermodynamics of seawater acid base chemistry implications for eocene and cretaceous ocean carbon chemistry and buffering reconstructed changes in seawater calcium and magnesium concentration ca2 mg2 predictably affect the ocean s acid base and carbon chemistry yet inaccurate formulations of chemical equilibrium constants are currently in use to account for these changes here we develop an efficient implementation of the miami ionic interactionmodel to predict all chemical equilibrium constants required for carbon chemistry calculations under variable ca2 and mg2 we investigate the impact of ca2 and mg2 on the relationships among the ocean s ph co2 dissolved inorganic carbon dic saturation state of caco3 and buffer capacity increasing ca2 and or mg2 enhances ion pairing which increases seawater buffering by increasing the concentration ratio of total to free uncomplexed carbonate ion an increase in ca2 however also causes a decline in carbonate ion to maintain a given thereby overwhelming the ion pairing effect and decreasing seawater buffering given the reconstructions of eocene ca2 and mg2 ca2 20mm mg2 30mm eocene seawater would have required essentially the same dic as today to simultaneously explain a similar to modern and the estimated eocene atmospheric co2 of 1000 ppm during the cretaceous at 4 times modern ca2 ocean buffering would have been at a minimum overall during times of high seawater ca2 caco3 saturation ph and atmospheric co2 were more susceptible to perturbations of the global carbon cycle for example given both eocene and cretaceous seawater ca2 and mg2 a doubling of atmospheric co2 would require less carbon addition to the ocean atmosphere system than under modern seawater composition moreover increasing seawater buffering since the cretaceous may have been a driver of evolution by raising energetic demands of biologically controlled calcification and co2 concentration mechanisms that aid photosynthesis

volcanic lightning global observations and constraints on source mechanisms lightning and electrification at volcanoes are important because they represent a hazard in their own right they are a component of the global electrical circuit and because they contribute to ash particle aggregation and modification within ash plumes the role of water substance water in all forms in particular has not been well studied here data are presented from a comprehensive global database of volcanic lightning lightning has been documented at 80 volcanoes in association with 212 eruptions the volcanic explosivity index vei could be determined for 177 eruptions eight percent of vei 3 5 eruptions have reported lightning and 10 of vei 6 but less than 2 of those with vei 1 2 these findings suggest consistent reporting for larger eruptions but either less lightning or possible under reporting for small eruptions ash plume heights 142 observations show a bimodal distribution with main peaks at 7 12 km and 1 4 km the former are similar to heights of typical thunderstorms and suggest involvement of water substance whereas the latter suggest other factors contributing to electrical behavior closer to the vent reporting of lightning is more common at night 56 and less common in daylight 44 reporting also varied substantially from year to year suggesting that a more systematic observational strategy is needed several weak trends in lightning occurrence based on magma composition were found the bimodal ash plume heights are obvious only for andesite to dacite basalt and basaltic andesite evenly span the range of heights and rhyolites are poorly represented the distributions of the latitudes of volcanoes with lightning and eruptions with lightning roughly mimic the distribution of all volcanoes which is generally flat with latitude meteorological lightning on the other hand is common in the tropics and decreases markedly with increasing latitude as the ability of the atmosphere to hold water decreases poleward this finding supports the idea that if lightning in large deep eruptions depends on water substance then the origin of the water is primarily magma and not entrainment from the surrounding atmosphere seasonal effects show that more eruptions with lightning were reported in winter bounded by the respective autumnal and vernal equinoxes than in summer this result also runs counter to the expectations based on entrainment of local water vapor

evolution of the sambagawa metamorphic belt japan abstract the high pressure sambagawa metamorphic belt evolved within a mesozoic accretionary prism that developed in the convergent margin along the east of the eurasian continent although extensively researched recent studies in this region have revealed a number of important features that allow more complete reconstruction of the tectonic history i the grouping of radiometric ages suggests the existence of three major structural units with distinct metamorphic histories one of these has since been completely eroded away ii the difference of ages recorded by different minerals is in many cases small suggesting rapid exhumation after reaching peak metamorphic conditions iii the dominant ductile deformation of the sanbagawa belt representing major orogen parallel flow is commonly related to retrograde metamorphic reactions this shows that the associated fabric developed during exhumation not subduction iv kinematic studies suggest that the main ductile deformation caused major ductile thinning of the region which was probably a significant factor in causing exhumation of the region

changes to the turbulent kinematics of a volcanic plume inferred from lightning data the 2009 redoubt volcano eruption produced a series of explosive events the largest of which produced episodes of volcanic lightning similar to thunderstorms flash energy spectra were calculated from lightning mapping data collected during the eruption the spectra were compared to the turbulence characteristics expected from each stage of plume development small flash length scales present at early times were associated with the gas thrust and initial convective stages increases in flash length scales and flash energy as the explosive events progressed were associated with an increase in volume of the plume spectra with a large range in flash length scales 0 2 10 km and a spectral peak at small flash length scales 1 km were associated with a superposition of spectra from gas thrust convective and umbrella ash cloud regions an approximate 5 3 power law slope was observed on the order of 10 min after gas thrust forcing had ended and the transition to a drifting ash cloud was underway which may reflect the dissipating state of the drifting ash cloud

exhuming the sanbagawa metamorphic belt the importance of tectonic discontinuities tectonic processes that have been proposed to explain the transport to the surface of regional metamorphic belts can be broadly divided into two types i corner flow within a convergent margin bounded by two essentially rigid plates associated with extension at shallow levels this type of model assumes deformation is distributed throughout the margin and that any discontinuities are of secondary importance ii expulsion or extrusion of coherent metamorphic nappes in this second idea tectonic discontinuities are fundamental in the transport to the surface of metamorphic rocks the wealth of geological data available from a variety of studies in the sanbagawa metamorphic belt southwest japan makes it well suited for studying the relative importance of continuous vs discontinuous deformation in the process of exhumation in the sanbagawa belt a sudden decrease in metamorphic pressure going down section of several kilobars suggests the presence of a major tectonic contact separating two major regional nappes an overlying higher pressure besshi nappe and an underlying lower pressure oboke nappe major tectonic discontinuities have also been proposed within the besshi nappe however indicators of metamorphic temperature the results of radiometric age dating and microstructural studies all suggest that post metamorphic discontinuities are minor and that this nappe formed and remained as an essentially coherent unit lithological associations and petrological studies suggest the following positions for the two nappes the besshi nappe formed deep within the former accretionary wedge adjacent to the overlying mantle wedge and with a dip of roughly 30 c in contrast the oboke nappe formed at moderate depths within the accretionary wedge was distant from the mantle wedge and was roughly horizontal penetrative deformation that post dates the peak of metamorphism has affected nearly all of the sanbagawa belt and has played an important role in its exhumation however the presence of a broad coherent besshi nappe overlying the lower pressure oboke nappe suggests that some process such as buoyancy driven extrusion was also important in the exhumation process and in forming the structure of the sanbagawa metamorphic belt

thermal calculation for high pressure contact metamorphism application to eclogite formation in the sebadani area the sambagawa belt sw japan abstract eclogite a high pressure temperature metamorphic rock characterized by garnet omphacite is usually considered to be a product of regional metamorphism under a low geothermal gradient however in the sebadani area of the sambagawa metamorphic belt most petrologists agree that the eclogite formed by localized contact metamorphism due to intrusion of a body in the solid state the sebadani mass this process is termed high pressure contact metamorphism however geological considerations suggest that the effect of such a process would be limited firstly because the speed of emplacement for solid state material will generally be much lower than that for magma and secondly because in the solid state there is no heat of fusion in the body available for thermal effects thermal modelling of a solid state intrusion based on the heat conduction equation allows the relationship between size of intrusion velocity of emplacement and thermal effects to be calculated two cases have been considered 1 a hot model where none of the heat conducted into the surroundings is lost during the rise of the body and 2 a cold model where all the heat conducted into the surroundings is lost these models bracket possible thermal histories of the body calculations suggest that in the sebadani region production of the observed metamorphic features requires unrealistically high velocity and a much larger intruded body than is observed these conclusions suggest that it is unlikely that eclogite in the sebadani area was formed by high pressure contact metamorphism but rather that it represents the highest grade part of the regional sambagawa metamorphism

effect of ambient mg ca ratio on mg fractionation in calcareous marine invertebrates a record of the oceanic mg ca ratio over the phanerozoic the mg ca ratio of seawater has changed significantly over the phanerozoic primarily as a function of the rate of ocean crust production echinoids crabs shrimps and calcareous serpulid worms grown in artificial seawaters encompassing the range of mg ca ratios that existed throughout the phanerozoic exhibit a direct nonlinear relationship between skeletal and ambient mg ca specimens grown in seawater with the lowest mg ca 1 changed their mineralogy to low mg calcite 4 mol mgco3 suggesting that these high mg calcareous organisms would have produced low mg calcite in the cretaceous when oceanic mg ca was lowest 1 these results support the empirical evidence that the skeletal chemistry of calcareous organisms has varied significantly over the phanerozoic as a function of the mg ca of seawater and that the mg ca of unaltered fossils of such organisms may be a record of oceanic mg ca throughout the phanerozoic mg fractionation algorithms which relate skeletal mg ca seawater mg ca and temperature were derived from these and other experiments they can be used to estimate paleoceanic mg ca ratios and temperatures from fossil skeletal mg ca of the organisms evaluated paleoceanic mg ca ratios recalculated by using the echinoderm mg fractionation algorithm from published fossil echinoid mg ca crinoid mg ca and paleotemperature data are consistent with other estimates and models of oceanic mg ca over the phanerozoic

late carboniferous high pressure metamorphism of the kassan metamorphic complex kyrgyz tianshan and assembly of the sw central asian orogenic belt abstract high pressure hp metamorphism of the kassan metamorphic complex kmc in the western kyrgyz tianshan has been related to either late ordovician or late carboniferous permian subduction processes we report sm nd ages for retrogressed eclogite samples and 40ar 39ar cooling ages for enclosing garnet muscovite samples from the kmc as new age constraints on hp metamorphism and rock exhumation these data will be used for an upgraded paleogeographic model for late paleozoic crustal consolidation in the southwestern central asian orogenic belt the retrogressed eclogite samples have transitional alkaline to tholeiitic affinity and trace element patterns consistent with protoliths derived from garnet bearing mantle sources at rifting plate margins geothermobarometric data for a retrogressed eclogite sample indicate peak metamorphic conditions of 540 30 c at 1 6 0 1 gpa samples from different lithotectonic units of the kmc provide coherent sm nd garnet whole rock ages of 317 4 ma and 316 3 ma 2 the prograde major element zoning in the mm sized garnets in combination with the moderate peak metamorphic temperature support our interpretation of the sm nd garnet ages as unambiguous evidence for late carboniferous hp metamorphism the sm nd garnet growth ages overlap within error with the 40ar 39ar mica cooling ages of 314 2 ma and 313 2 ma 2 indicating rapid uplift of the subduction complex after peak metamorphism the ca 317 313 ma hp exhumation event of the kmc is contemporaneous with those of the atbashi and akeyazi ca 500 km east in nw china hp complexes and implies similar collision histories at the south tianshan suture to the east and west of the talas fergana fault tff the exhumation of the kmc and atbashi hp complexes overlaps with the initiation of the tff rolland et al 2013 suggesting incipient separation of the chatkal and atbashi complexes during rock exhumation and early plate collision

calibration of the b ca proxy in the planktic foraminifer orbulina universa to paleocene seawater conditions the b ca ratio of planktic foraminiferal calcite a proxy for the surface ocean carbonate system displays large negative excursions during the paleocene eocene thermal maximum petm 55 9 ma consistent with rapid ocean acidification at that time however the b ca excursion measured at the petm exceeds a magnitude that modern ph calibrations can explain numerous other controls on the proxy have been suggested including foraminiferal growth rate and the total concentration of dissolved inorganic carbon dic here we present new calibrations for b ca versus the combined effects of ph and dic in the symbiont bearing planktic foraminifer orbulina universa grown in culture solutions with simulated paleocene seawater elemental composition high ca low mg and low total boron concentration b t we also investigate the isolated effects of low seawater b t high ca reduced symbiont photosynthetic activity and average shell growth rate on o universa b ca in order to further understand the proxy systematics and to determine other possible influences on the petm records we find that average shell growth rate does not appear to determine b ca in high calcite saturation experiments in addition our paleocene calibration shows higher sensitivity than the modern calibration at low b oh 4 dic given a large dic pulse at the petm this amplification of the b ca response can more fully explain the petm b ca excursion however further calibrations with other foraminifer species are needed to determine the range of foraminifer species specific proxy sensitivities under these conditions for quantitative reconstruction of large carbon cycle perturbations

structural and petrological constraints on the tectonic evolution of the garnet lherzolite facies higashi akaishi peridotite body sanbagawa belt sw japan 1 the higashi akaishi peridotite body in the sanbagawa metamorphic belt is a unique example of a kilometer scale body including garnet lherzolite facies rocks from an oceanic subduction type orogen in this body four distinct deformational phases d1 d2 d3 and d4 can be defined the tectonic significance of d1 is unclear microstructural observations and application of garnet orthopyroxene geothermobarometry suggest that d2 took place during high temperature subduction up to depths of 100 km from 2 3 gpa to above 2 8 gpa at temperature of 700 800 c or more d3 represents a major phase of exhumation after exhumation the higashi akaishi body became juxtaposed with the adjacent besshi and eclogite units at a depth of around 35 km 1 gpa the common history of the two units after d3 is shown by the intertectonic growth of tremolite between d3 and d4 that corresponds to a stage of intertectonic growth of plagioclase in the besshi and eclogite units both the spatial distribution and the estimated pressure temperature p t conditions of this intertectonic phase of mineral growth in the different units are in excellent agreement the development of an antigorite schistosity during the late stage of d2 indicates an anticlockwise p t path with cooling at depths of around 100 km the association of the antigorite bearing fabric and the onset of exhumation after the d2 stage suggest that the density decrease due to antigorite formation may have been sufficient to trigger the exhumation of dense ultramafic body from uhp conditions in subduction zones syn d2 water introduction and the anticlockwise p t path are expected when convection in the mantle wedge brings peridotite toward a subduction boundary through mantle wedge or when peridotite is dragged down along a subduction boundary that is progressively cooling immediately after initiation of subduction

experimental generation of volcanic lightning explosive volcanic eruptions are commonly associated with intense electrical activity and lightning direct measurement of the electric potential at the vent where the electric activity in the volcanic plume is first observed is severely impeded limiting progress in its investigation we have achieved volcanic lightning in the laboratory during rapid decompression experiments of gas particle mixtures under controlled conditions and recorded it using a high speed camera and two antennas we find that lightning is controlled by the dynamics of the particle laden jet and by the abundance of fine particles the relative movement of clusters of charged particles generates the electrical potential which is necessary for lightning the experimental generation of volcanic lightning suggests that rapid progress can now be expected in understanding electrical phenomena in volcanic plumes to implement lightning monitoring systems and the forecasting of volcanic ash emissions

application of calcite mg partitioning functions to the reconstruction of paleocean mg ca abstract calcite mg ca is usually assumed to vary linearly with solution mg ca that a constant partition coefficient describes the relationship between these two ratios numerous published empirical datasets suggests that this relationship is better described by a power function we provide a compilation of these literature data for biotic and abiotic calcite in the form of calcite mg ca f solution mg ca h where f and h are empirically determined fitting parameters describing the slope and deviation from linearity respectively of the function this is equivalent to freundlich sorption behavior controlling mg incorporation in calcite using a power function instead of a partition coefficient lowers phanerozoic seawater mg ca estimates based on echinoderm skeletal material by on average 0 5 mol mol from previous estimates these functions can also be used to model the primary skeletal calcite mg ca of numerous calcite phases through geologic time such modeling suggests that the mg ca of all calcite precipitated from seawater has varied through the phanerozoic in response to changing seawater mg ca and that the overall range in mg ca measured among various calcite phases would be greatest when seawater mg ca was also high e g aragonite seas and lowest when seawater mg ca was low e g calcite seas it follows that during times of calcite seas when the seawater mg ca is presumed to have been lower deposition of calcite with low mg contents would have resulted in a depressed drive for diagenetic stabilization of shelfal carbonate and in turn lead to greater preservation of crystal and skeletal microfabrics and primary chemistries in biotic and abiotic calcites

environmental controls on b ca in calcite tests of the tropical planktic foraminifer species globigerinoides ruber and globigerinoides sacculifer abstract the ratio of boron to calcium b ca in the calcite tests of planktic foraminifers may serve as a proxy for past seawater chemistry but controls on b incorporation are not yet certain here we present the results of laboratory culture experiments with live specimens of globigerinoides ruber pink and globigerinoides sacculifer which provide new insight into b incorporation controls we find that in g sacculifer b ca increases with increasing ph lower hco3 higher co32 and b oh 4 but decreases with increasing total dissolved inorganic carbon dic higher hco3 and co32 constant b oh 4 this suggests competition between aqueous boron and carbon species for inclusion into the calcite lattice similar to previous experiments with the subtropical temperate orbulina universa b ca increases with salinity but not with temperature we evaluate possible carbonate system control parameters and compare our tropical culture calibrations with new and published core top data