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

ba ca in benthic foraminifera thermocline and middepth circulation in the north atlantic during the last glaciation 1 this geochemical investigation utilizes ba ca in the benthic foraminifer cibicides wuellerstorfi from cores taken from the bahama banks and the caribbean sea to reconstruct changes in basal thermocline ventilation 800 1000 m and middepth thermohaline circulation 1000 2000 m in the western north atlantic during the last glacial period focusing on the deglacial transition previous studies show that an increase in ventilation of the north atlantic subtropical gyre during the last glacial maximum lgm caused a 30 60 decrease in labile nutrients within the thermocline layer using foraminiferal ba ca as a proxy of refractory nutrients increased ventilation during the lgm produced a depletion of less than 20 compared to holocene values following glaciation the production of glacial north atlantic intermediate water gnaiw shut down owing to the presence of meltwater in the surface ocean which resulted in a decrease in ventilation as seen by an enrichment of barium in the basal thermocline gnaiw was subsequently replaced by barium rich southern component water in the middepth western north atlantic foraminiferal ba ca data suggest a 38 contribution from southern component water to a depth as shallow as 1475 m and a 14 contribution at 1123 m during deglaciation

incorporation of uranium in benthic foraminiferal calcite reflects seawater carbonate ion concentration the chemical and isotopic composition of foraminiferal shells so called proxies reflects the physico chemical properties of the seawater in current day paleoclimate research the reconstruction of past seawater carbonate system to infer atmospheric co2 concentrations is one of the most pressing challenges and a variety of proxies have been investigated such as foraminiferal u ca since in natural seawater and traditional co2 perturbation experiments the carbonate system parameters co vary it is not possible to determine the parameter of the carbonate system causing e g changes in u ca complicating the use of the latter as a carbonate system proxy we overcome this problem by culturing the benthic foraminifer ammonia sp at a range of carbonate chemistry manipulation treatments shell u ca values were determined to test sensitivity of u incorporation to various parameters of the carbonate system we argue that co32 is the parameter affecting the u ca ratio and consequently the partitioning coefficient for u in ammonia sp du we can confirm the strong potential of foraminiferal u ca as a co32 proxy

a simple evaluation of cleaning procedures on fossil benthic foraminiferal mg ca 1 recent studies suggest that benthic foraminiferal mg ca may be useful in reconstructing deep water temperature changes during the quaternary and on longer timescales rosenthal et al 1997 lear et al 2000 martin et al 2002 because changes in deep water temperature may be small sample preparation could play an important role in reconstructing accurate temperatures from shell mg ca a simple examination of changes in measured shell chemistry of benthic foraminifera from two intervals subjected to increasingly rigorous cleaning reveals that fossil benthic foraminiferal samples cleaned by oxidation yield lower mg ca values than samples only rinsed and weak acid leached reductive cleaning further lowered the shell mg ca of one of the two benthic species examined lower mg ca values following oxidation and reduction appear to reflect removal of contaminant mg associated with remnant organic matter and adsorbed phases

microdistribution of mg ca sr ca and ba ca ratios in pulleniatina obliquiloculata test by using a nanosims implication for the vital effect mechanism the mg ca ratio within foraminiferal calcareous tests shells is widely used to reconstruct past seawater temperature however recent studies reported that the organic components within a test affect the mg ca distribution in this study we have measured the mg ca sr ca and ba ca ratios within the planktonic foraminifera pulleniatina obliquiloculata by using a nanosims secondary ion mass spectrometer sims which has excellent spatial resolution 1 m and allows us to compare the distribution of chemical compositions with that of the organic components element compositions show banding distributions composed of alternately higher and lower values of those elemental ratios the mg ca ratios previously considered to be mainly controlled by calcification temperature show larger variations than the values expected from the seawater temperature at the habitat depth of p obliquiloculata comparison of the elemental distribution with the test microstructure reveals that the bands of high mg ca and sr ca ratios correspond with layers of the organic components such coincidence suggests that the organic components strongly affect the mg ca and sr ca ratios within a test in spite of the heterogeneous distribution temperature estimated from the averaged mg ca ratio within a test is consistent with seawater temperature at the habitat depth of p obliquiloculata indicating that whole mg ca ratio of foraminiferal test may be useful as paleotemperature proxy in contrast to the mg ca ratio the heterogenity in ba ca ratio which previously has been considered to be mainly controlled by the ambient seawater composition is not fully matched with the layers of the organic compositions although the organic components concentrate ba other unknown factors appear to also cause heterogenity in ba incorporation

controls on sr ca in benthic foraminifera and implications for seawater sr ca during the late pleistocene changes in the sr to ca ratio of sea water have important implications for the interpretation of past climate it has proven difficult to interpret sr ca of foraminiferal calcite as a measure of seawater sr ca or as reflecting the influence of deep water carbonate ion saturation co 32 on the incorporation of sr into benthic foraminiferal carbonate here we address this issue by measurements of paired benthic foraminiferal sr ca and b ca a proxy for deep water delta co 32 for core tops from the global ocean and three down cores at different settings during the last glacial textendash interglacial cycle these new data suggest a significant control of deep water delta co 32 on benthic foraminiferal sr ca and that down core shell sr ca variations can be largely accounted for by past deep water delta co 32 changes we conclude that seawater sr ca has likely remained near constant on glacial textendash interglacial timescales during the late pleistocene in agreement with model results with due caution benthic sr ca may be used as an auxiliary proxy for deep water delta co 32 if seawater sr ca is constant

effect of mg ca ratio in seawater on shell composition in shallow benthic foraminifera 1 the ratio of magnesium to calcium mg ca in caco3 shells of foraminifera is widely used to determine paleotemperatures however mg ca is highly variable within and between species suggesting a strong physiological influence on the incorporation of mg2 into the shells while most field and laboratory calibrations have focused on the effect of temperature we chose to study the effect of ambient mg ca on the calcification process and the final shell composition we cultured two species of symbiont bearing benthic foraminifera amphistegina lobifera and amphistegina lessonii in seawater with different mg ca ratios electron probe analysis of the shell mg ca revealed a positive but not entirely linear correlation with mg ca in the culturing media with slightly different curves for each species partition coefficients of mg2 dmg in the calcite shells showed a decrease by a factor of roughly 2 between the lowest and highest mg ca in the ambient water this was previously demonstrated in inorganic calcite precipitation experiments however the biogenic dmg was significantly lower than the inorganic one suggesting a physiological mechanism that reduces mg ca at the calcification site unlike inorganic experiments that display a dependence of dmg on the kinetics of precipitation the biogenic dmg is not correlated with the rate of calcification both dmg and calcification rates in our experiment were sensitive to the mg ca ratio rather than the concentration of either ca2 or mg2 the largest addition of caco3 was obtained at mg ca of 1 and not at present day seawater ratio mg ca 5 this may reflect the mg ca that prevailed during the eocene mg ca 1 5 when this genus evolved

atmospheric effects on ejecta emplacement laboratory experiments allow the investigation of complex interactions between impacts and an atmosphere although small in scale they can provide essential first order constraints on the processes affecting late stage ballistic ejecta and styles of ejecta emplacement around much larger craters on planetary surfaces the laboratory experiments involved impacting different fine grained particulate targets under varying atmospheric pressure and density different gas compositions during crater formation ballistic ejecta form the classic cone shaped profile observed under vacuum conditions as atmospheric density increases for a given pressure however the ejecta curtain bulges at the base and pinches above this systematic change in the ejecta curtain reflects the combined effects of deceleration of ejecta smaller than a critical size and entrainment of these ejecta within atmospheric vortices created as the outward moving wall of ejecta displaces the atmosphere additionally a systematic change in emplacement style occurs as a function of atmospheric pressure largely independent of density contiguous ejecta rampart superposing ballistically emplaced deposits 0 06 to 0 3 bar ejecta flow lobes 0 3 to 0 7 bar and radial patterns 0 8 bar underlying processes controlling such systematic changes in emplacement style were revealed by observing the evolution of the ejecta curtain by changing target materials including layered targets and low density particulates by varying atmospheric density by changing impact angle and by comparing the ejecta run out distances with first order models of turbidity flows three distinct ejecta emplacement processes can be characterized ejecta ramparts result from coarser clasts sorted and driven outward by vortical winds behind the outward moving ejecta curtain this style of wind modified emplacement represents minimal ejecta entrainment and is enhanced by a bimodal size distribution in the ejecta such eddy supported flows are observed to increase in run out distance scaled to crater size with increasing atmospheric pressure by analogy with turbidity flows this scaled distance should increase as r1 2 for a given atmospheric pressure and degree of entrainment ejecta flows with much greater run out distances develop as the turbulent power in atmospheric response winds increase such flows overrun and scour the inner ejecta facies thereby producing distinct inner and outer facies the degree of ejecta entrainment depends on the dimensionless ratio of drag to gravity forces acting on individual ejecta and the intensity of the winds created by the outward moving curtain entrainment increases with increasing atmospheric density and ejection velocity crater size but decreases with ejecta density and size the intensity of curtain generated winds increases with ejection velocity crater size the dimensionless drag ratio characterizing the laboratory experiments can be applied to mars since the reduced atmospheric density is offset by the increased ejection velocities for kilometer scale events for a given crater size ejection velocity and atmospheric conditions a wide range of nonballistic ejecta emplacement styles could occur simply by varying ejecta sizes even without the presence of water alternatively the onset crater diameter for nonballistic emplacement styles can reflect the range of ejecta sizes possible from the diverse martian geologic history massive basalts to fine grained aeolian deposits scaling considerations further predict that ejecta run out distances scaled to crater size on mars should increase as r1 2 hence long run out flows dependent on crater diameter need not reflect depth to a buried reservoir of water on venus however the dense atmosphere maximizes entrainment and results in ejecta flow densities approaching a constant fraction of the atmospheric density under such conditions ejecta run out distances should decrease as r 1 2

mg ca in the benthic foraminifera cibicidoides wuellerstorfi and cibicidoides mundulus temperature versus carbonate ion saturation magnesium calcium mg ca ratios in two widely used benthic foraminiferal species cibicidoides wuellerstorfi and cibicidoides mundulus cibicidoides kullenbergi picked from global ocean core tops and from six cores in the north atlantic ocean have been measured to investigate mg ca variability cleaning effect and influences from bottom water temperature bwt and deep water carbonate ion saturation co32 replicate measurements of the two species reveal mg ca variability of 0 07 0 07 mmol mol compared with mg ca in samples cleaned by oxidative cleaning mg ca ratios are significantly lowered by 0 10 0 09 mmol mol in samples cleaned by reductive cleaning likely due to preferential leaching during the reductive cleaning step the cleaning influence is large relative to glacial interglacial mg ca changes 0 05 0 31 mmol mol by this study regression of core top data from a wide range of locations show that c wuellerstorfi mg ca is strongly affected by deep water co32 with a sensitivity of 0 009 mmol mol per mol kg when bwt is included in regressions the correlation is slightly more significant with a weak bwt sensitivity on mg ca of between 0 03 0 01 and 0 07 0 02 mmol mol per c because co32 and bwt co vary for most core top samples an alternate method of separating the two effects was made by comparing glacial to interglacial changes in mg ca from a depth transect of north atlantic cores where the bwt and carbonate ion histories since the last glacial period have been well constrained results from this transect suggest that the bwt effect is 0 03 mmol mol per c weaker than inferred from the core top study therefore core top and down core data suggest that c wuellerstorfi mg ca is insensitive to bwt changes the weak bwt effect when compared with natural variability complicates the use of mg ca in this species to reconstruct past bwt taking all measured samples from various environments into account c mundulus mg ca ratios show no correlation with bwt or deep water co32

planktic foraminifers as recorders of seawater ba ca abstract recent studies have used the ba ca ratio of planktic foraminifer shells as a proxy for river run off at oceanic sites near estuaries such studies assume that the ba ca ratio in planktic foraminifer shells is primarily controlled by the ba ca concentration of seawater and that other parameters such as salinity temperature and ph do not compromise the primary ba concentration relationship here we provide new insights from culture experiments and review published studies to confirm that environmental parameters including ph temperature salinity and symbiont photosynthesis do not affect ba substitution into planktic foraminiferal calcite the partition coefficient for ba in spinose planktic foraminifers is estimated as d ba 0 15 0 05 95 confidence limits the same factor also seems applicable to the non spinose genus neogloboquadrina but not to specimens of the non spinose genus globorotalia

effects of seawater carbonate ion concentration and temperature on shell u mg and sr in cultured planktonic foraminifera we investigate the sensitivity of u ca mg ca and sr ca to changes in seawater co3 and temperature in calcite produced by the two planktonic foraminifera species orbulina universa and globige rina bulloides in laboratory culture experiments our results demonstrate that at constant temperature u ca in o universa decreases by 25 7 per 100 mol co3 k g 1 as seawater co3 increases from 110 to 470 mol kg 1 results from g bulloides suggest a similar relationship but u ca is consistently offset by 40 at the same environmental co3 in o universa u ca is insensitive to temperature between 15 c and 25 c applying the o universa relationship to three u ca records from a related species globigerinoides sacculifer we estimate that caribbean and tropical atlantic co3 was 110 70 mol kg 1 and 80 40 mol kg 1 higher respectively during the last glacial period relative to the holocene this result is consistent with estimates of the glacial interglacial change in surface water co3 based on both modeling and on boron isotope ph estimates in settings where the addition of u by diagenetic processes is not a factor down core records of foraminiferal u ca have potential to provide information about changes in the ocean s carbonate concentration below ambient ph ph 8 2 mg ca decreased by 7 5 o universa t o 16 6 g bulloides per 0 1 unit increase in ph above ambient ph the change in mg ca was not significant for either species this result suggests that mg ca based paleotemperature estimates for the quaternary during which surface ocean ph has been at or above modern levels have not been biased by variations in surface water ph sr ca increased linearly by 1 6 0 4 per 0 1 unit increase in ph shell mg ca increased exponentially with temperature in o universa where mg ca 0 85 exp 0 096 t whereas the change in sr ca with temperature was within the reproducibility of replicate measurements copyright 2004 elsevier ltd

biomineralization in perforate foraminifera in this paper we review the current understanding of biomineralization in perforate foraminifera ideas on the mechanisms responsible for the flux of ca2 and inorganic carbon from seawater into the test were originally based on light and electron microscopic observations of calcifying foraminifera from the 1980s onward tracer experiments fluorescent microscopy and high resolution test geochemical analysis have added to existing calcification models despite recent insights no general consensus on the physiological basis of foraminiferal biomineralization exists current models include seawater vacuolization transmembrane ion transport involvement of organic matrices and or ph regulation although the magnitude of these controls remain to be quantified disagreement between currently available models may be caused by the use of different foraminiferal species as subject for biomineralization experiments and or lack of a more systematic approach to study dis similarities between taxa in order to understand foraminiferal controls on element incorporation and isotope fractionation and thereby improve the value of foraminifera as paleoceanographic proxies it is necessary to identify key processes in foraminiferal biomineralization and formulate hypotheses regarding the involved physiological pathways to provide directions for future research

mg ca ratios of the benthic foraminifera oridorsalis umbonatus obtained by laser ablation from core top sediments relationship to bottom water temperature 1 a laser ablation system connected to an inductively coupled plasma mass spectrometer was used to determine mg ca ratios of the benthic foraminifera oridorsalis umbonatus a set of modern core top samples collected along a depth transect on the continental slope off namibia 320 2300 m water depth 2 9 to 10 4 c was used to calibrate the mg ca ratio against bottom water temperature the resulting mg ca bottom water temperature relationship of o umbonatus is described by the exponential equation mg ca 1 528 e0 09 bwt the temperature sensitivity of this equation is similar to previously published calibrations based on cibicidoides species suggesting that the mg ca ratio of o umbonatus is a valuable proxy for thermocline and deep water temperature

the importance of symbiont bearing benthic foraminifera for west pacific carbonate beach environments abstract in the tropical central and west pacific as well as in the east indian ocean symbiont bearing benthic foraminifera often are the main producers of calcium carbonate grains deposited at beaches the proportion of foraminiferal tests in medium sized to coarse sand grains may range from 20 to 95 this depends on two factors productivity and transport because foraminifers do not live on or in the sandy bottom near the beaches but prefer firm substrate in high energy environments close to the front of coral reefs foraminiferal tests are produced in extreme numbers on the reef crest of sesoko island okinawa japan 0 6 kg m 2 year 1 which is covered by macroalgae or in the transition zone between the crest and the reef moat 1 3 kg m 2 year 1 empty tests released by reproduction or death are entrained at the reef crest by waves and transported by currents this transport depends on the direction and intensity of currents connecting the habitat reef crest and transition to moat with the deposition area central moat lagoon beach habitat destruction and or the interruption or diversion of water flow hinders the accumulation of foraminiferal tests at the beach where deepening the moat intensifies beach parallel currents supply to and deposition at the beach are reduced while the remaining sand is eroded by tropical cyclones understanding the ecology especially population dynamics of larger foraminifera in combination with factors influencing the transport of empty tests is essential to preserve the balance between deposition and removal of sand at carbonate beaches in the west pacific and east indian ocean

a centennial reappraisal of the vredefort pseudotachylytes shaken not stirred by meteorite impact major pseudotachylyte zones constitute a spectacular component of the renowned c 2 023 ga vredefort impact structure south africa but it has always been difficult to explain how they were formed in his original account in 1916 shand interpreted the pseudotachylyte as due to cataclasis and frictional heating but pointed out two enigmas that have remained since there were no associated major faults and the pseudotachylyte volumes he observed were far greater than in similar rocks located within faults elsewhere on earth new observations show that the vredefort pseudotachylyte zones were indeed formed by cataclasis and frictional heating not by faulting but owing to impact induced seismic shaking initiated around temporarily loosened blocks in dendritic fracture systems progressive cataclasis of such loose blocks by intense high frequency oscillations of the country rock at the beginning of the cratering process led to size reduction rounding and comminution and frictional melting of feldspars and biotite in the comminuted parts most pseudotachylyte was thus not injected from anywhere but produced in situ the process of seismic shaking is well known from impacts on the moon and asteroids terrestrial earthquakes and nuclear tests but has largely been overlooked in terrestrial cratering except in the theoretical concept of acoustic fluidization

near at eros imaging and spectral results eros is a very elongated 34 kilometers by 11 kilometers by 11 kilometers asteroid most of the surface of which is saturated with craters smaller than 1 kilometer in diameter the largest crater is 5 5 kilometers across but there is a 10 kilometer saddle like depression with attributes of a large degraded crater surface lineations both grooves and ridges are prominent on eros some probably exploit planes of weakness produced by collisions on eros and or its parent body ejecta blocks 30 to 100 meters across are abundant but not uniformly distributed over the surface albedo variations are restricted to the inner walls of certain craters and may be related to downslope movement of regolith on scales of 200 meters to 1 kilometer eros is more bland in terms of color variations than gaspra or ida spectra 800 to 2500 nanometers are consistent with an ordinary chondrite composition for which the measured mean density of 2 67 0 1 grams per cubic centimeter implies internal porosities ranging from about 10 to 30 percent

impact excitation of a seismic pulse and vibrational normal modes on asteroid bennu and associated slumping of regolith we consider an impact on an asteroid that is energetic enough to cause resurfacing by seismic reverberation and just below the catastrophic disruption threshold assuming that seismic waves are not rapidly attenuated in asteroids with diameter less than 1 km we identify a regime where rare energetic impactors can excite seismic waves with frequencies near those of the asteroid s slowest normal modes in this regime the distribution of seismic reverberation is not evenly distributed across the body surface with mass spring model elastic simulations we model impact excitation of seismic waves with a force pulse exerted on the surface and using three different asteroid shape models the simulations exhibit antipodal focusing and normal mode excitation if the impulse excited vibrational energy is long lasting vibrations are highest at impact point its antipode and at high surface elevations such as an equatorial ridge a near equatorial impact launches a seismic impulse on a non spherical body that can be focused on two additional points on an the equatorial ridge we explore simple flow models for the morphology of vibration induced surface slumping we find that the initial seismic pulse is unlikely to cause large shape changes long lasting seismic reverberation on bennu caused by a near equatorial impact could have raised the height of its equatorial ridge by a few meters and raised two peaks on it one near impact site and the other near its antipode

eruption of magmatic foams on the moon formation in the waning stages of dike emplacement events as an explanation of irregular mare patches abstract volcanic eruptions on the moon take place in conditions of low gravity and negligible atmospheric pressure very different from those on earth these differences lead to characteristic lunar versions of hawaiian and strombolian explosive activity and to the production of unusual eruption products neither predicted nor observed on earth in the terminal stages of eruptions these include the unusual mounds and rough hummocky blocky floors of some small shield summit pit crater floors elongate depressions and mare flows similar to those named irregular mare patches imps by braden et al 2014 we examine the ascent and eruption of magma in the waning stages of the eruptive process in small shield summit pit crater floors and show that many imp characteristics can be plausibly explained by basaltic magma behavior as the rise rate of the ascending magma slows to zero volatiles exsolve in the dike and lava lake to form a very vesicular foam and the dike begins to close stresses in the very vesicular and porous lava lake crust produce fractures through which the foam extrudes at a rate determined by its non newtonian rheology waning stage extrusion of viscous magmatic foams to the surface produces convex mounds whose physical properties inhibit typical impact crater formation and regolith development creating an artificially young crater retention age this mechanism for the production and extrusion of very vesicular magmatic foams is also applicable to waning stage dike closure associated with pit craters atop dikes and fissure eruptions in the lunar maria providing an explanation for many irregular mare patches this mechanism implies that imps and associated mare structures small shields pit craters and fissure flows formed synchronously billions of years ago in contrast to very young ages less than 100 million years proposed for imps by some workers

boulder stranding in ejecta launched by an impact generated seismic pulse abstract we consider how an impact generated seismic pulse affects the surface of an asteroid distant from the impact site with laboratory experiments on dry polydisperse gravel mixtures we track the trajectories of particles ejected from the surface by a single strong upward propagating pressure pulse high speed video images show that ejecta trajectories are independent of particle size and collisions primarily take place upon landing when they land particles are ballistically sorted as proposed by shinbrot et al 2017 leaving larger particles on the surface and smaller particles more widely dispersed a single strong pulse can leave previously buried boulders stranded on the surface boulder stranding due to an impact excited seismic pulse is an additional mechanism that could leave large boulders present on the surface of rubble asteroids such as 162173 ryugu 101955 bennu and 25143 itokawa

oxygen and carbon isotopic variation in co existing larger foraminifera from a reef flat at akajima okinawa japan the larger foraminiferal assemblage on the reef flat at akajima ryukyu island arc is comprised of marginopora kudakajimaensis amphisorus hemprichii sorites orbiculus peneroplis planatus heterostegina depressa neorotalia calcar calcarina gaudichaudii baculogypsina sphaerulata and amphistegina lessonii the oxygen and carbon isotopic variations in several specimens of each species living under similar conditions were examined symbiosis had little to no effect on oxygen isotopic composition of the bulk carbonate of the analysed species the isotopic analysis along the ontogenetic stages indicates near equilibrium precipitation of oxygen isotopes in the early life stages and therefore the initial chambers should be microsampled in isotopic analyses for a better estimate of palaeotemperature the order of depletion of 13c parallels the order of accretion of calcium carbonate by the foraminiferal species a poor correlation between 18o and 13c and a large variation in 18o and 13c with size of the shell are the characteristic features of the symbiont bearing benthic foraminifera inhabiting reef flat environments in a deeper water species oxygen isotopic values vary little with size of the shell

ina pit crater on the moon extrusion of waning stage lava lake magmatic foam results in extremely young crater retention ages the enigmatic ina feature on the moon was recently interpreted to represent extrusive basaltic volcanic activity within the past 100 m y of lunar history an extremely young age for volcanism on the moon ina is a 2 3 km d shaped depression that consists of a host of unusual bleb like mounds surrounded by a relatively optically fresh hummocky and blocky floor documentation of magmatic volcanic processes from shield volcano summit pit craters in hawai i and new insights into shield building and dike evolution processes on the moon provide important perspectives on the origin of ina we show that the size location morphology topography and optical maturity of ina are consistent with an origin as a subsided summit pit crater lava lake on top of a broad 22 km diameter 3 5 b y old shield volcano new theoretical treatments of lunar shield building magmatic dike events predict that waning stage summit activity was characterized by the production of magmatic foam in the dike and lake the final stages of dike stress relaxation and closure cause the magmatic foam to extrude to the surface through cracks in the lava lake crust to produce the mounds the high porosity of the extruded foams 75 altered the nature of subsequent impact craters the aerogel effect causing them to be significantly smaller in diameter which could bias the crater derived model ages accounting for this effect allows for significantly older model ages to 3 5 b y contemporaneous with the underlying shield volcano thus extremely young volcanic eruptions are not required to explain the unusual nature of ina

an evaluation of benthic foraminiferal b ca and δ11b for deep ocean carbonate ion and ph reconstructions reliable reconstructions of deep ocean carbonate ion concentration co32 and ph are crucial to understand mechanisms responsible for the past atmospheric co2 variations observed in ice cores however it is challenging to reconstruct past deep water co32 and ph and literature results from different proxies conflict warranting careful investigations on possible reasons for the existing inconsistencies here we present the first down core b ca and 11b records measured in an epifaunal benthic foraminifer cibicidoides wuellerstorfi from the caribbean sea during the last 160 kyr the two proxies yield quantitatively comparable deep water co3 2 and ph results showing high values during glacials relative to inter glacials differences in co32 and ph are 35 mol kg and 0 15 respectively consistent with past ocean circulation changes in the caribbean sea our data provide convincing evidence that both proxies serve as faithful proxies to estimate deep ocean co32 and ph despite our incomplete understanding of boron incorporation into foraminiferal carbonates

u ca in benthic foraminifers a proxy for the deep sea carbonate saturation the ocean plays a major role in the global carbon cycle and attempts to reconstruct past changes in the marine carbonate system are increasing the speciation of dissolved uranium is sensitive to variations in carbonate system parameters and previous studies have shown that this is recorded in the uranium to calcium ratio u ca of the calcite shells of planktonic foraminifera here we test whether u ca ratios of deep sea benthic foraminifera are equally suited as an indicator of the carbonate system we compare u ca in two common benthic foraminifer species planulina wuellerstorfi and cibicidoides mundulus from south atlantic core top samples with the calcite saturation state co32 co32 in situ co32 sat of the ambient seawater and find significant negative correlations for both species compared with planktonic foraminifera the sensitivity of u ca in benthic foraminifera to changes in co32 is about 1 order of magnitude higher although co32 exerts the dominant control on the average foraminiferal u ca the intertest and intratest variability indicates the presence of additional factors forcing u ca

imaging of small scale features on 433 eros from near evidence for a complex regolith on 25 october 2000 the near earth asteroid rendevous near shoemaker spacecraft executed a low altitude flyover of asteroid 433 eros making it possible to image the surface at a resolution of about 1 meter per pixel the images reveal an evolved surface distinguished by an abundance of ejecta blocks a dearth of small craters and smooth material infilling some topographic lows the subdued appearance of craters of different diameters and the variety of blocks and different degrees of their burial suggest that ejecta from several impact events blanketed the region imaged at closest approach and led to the building up of a substantial and complex regolith consisting of fine materials and abundant meter sized blocks

influence of test size water depth and ecology on mg ca sr ca δ18o and δ13c in nine modern species of planktic foraminifers abstract mg ca palaeothermometry in foraminiferal calcite is a widely applied tool in palaeoceanography however our understanding of the effects of planktic foraminiferal ecology and early diagenesis on test calcite mg ca is limited here we report results of a study designed to shed new light on ecological size related and very early water column diagenetic controls on mg ca in planktic foraminiferal calcite we analysed mg ca and stable isotopes of nine modern planktic foraminiferal species across fourteen mostly 50 m window sieve fractions in a core top sample from the north atlantic ocean we also analysed mg ca in four of these nine species from plankton tow samples collected from 0 to 2500 m water depth in the north atlantic ocean and arabian sea our core top study confirms that sensitivity of mg ca to change in test size is species specific but reveals an overall decrease in mg ca with increasing test size in all but one species orbulina universa for which mg ca increases with size these findings are broadly consistent with known ecological behaviour suggesting that the size related signal is largely environmentally rather than calcification rate controlled our results underscore the need to undertake mg ca palaeothermometry on narrow size fractions of planktic foraminifers particularly for shallow dwelling species such as g bulloides and g ruber where mg ca is most sensitive to test size across the size range of 200 350 m our plankton tow data from the arabian sea are in agreement with in situ temperatures in contrast our data from the north atlantic ocean reveal large variability and marked offsets to warmer values from in situ temperatures that are interpreted to reflect lateral advection from the south storm induced vertical mixing of the water column and or the influence of surface water salinity on the mg ca signal none of our plankton tow mg ca data shows any evidence of test dissolution in the water column our study provides important verification that the mg ca signal recorded during calcification does not undergo diagenetic degradation during test transport to the sea floor thereby satisfying an important precondition of its palaeo proxy utility

response of infaunal macrobenthos to the sediment granulometry in a tropical continental margin southwest coast of india abstract surficial sediment samples collected from the continental margin of the southwest coast of india in july 2004 were examined for the grain size and soft bottom macrobenthic fauna to understand the sediment granulometry and its effect on the faunal distribution samples were collected using smith mcintyre grab from 20 to 200 m depth range consisting of mid shelf outer shelf and slope fine grained sediment located in the mid shelf and supported low faunal abundance polychaetes constituted the bulk of the fauna feeding guild changed with depth and sediment granulometry coexistence of deposit feeders and carnivores in outer shelf and deposit feeders and filter feeders in the slope region indicated the effective utilization of different food resources in general richness and diversity were high in the southern region depth wise the diversity and abundance were relatively high in the 50 75 m depth range correlation and bio env analysis showed that combination of different factors such as sediment texture sediment sorting and depth were found to influence the distribution of macrobenthos hence spatial variations observed in benthic community were presumably linked to the variations in sediment granulometry and the energy level conditions prevailing in the area

quantitative analysis of impact induced seismic signals by numerical modeling we quantify the seismicity of impact events using a combined numerical and experimental approach the objectives of this work are 1 the calibration of the numerical model by utilizing real time measurements of the elastic wave velocity and pressure amplitudes in laboratory impact experiments 2 the determination of seismic parameters such as quality factor q and seismic efficiency k for materials of different porosity and water saturation by a systematic parameter study employing the calibrated numerical model by means of numerical experiments we found that the seismic efficiency k decreases slightly with porosity from k 3 4 10 3 for nonporous quartzite to k 2 6 10 3 for 25 porous sandstone if pores are completely or partly filled with water we determined a seismic efficiency of k 8 2 10 5 which is approximately two orders of magnitude lower than in the nonporous case by measuring the attenuation of the seismic wave with distance in our numerical experiments we determined the seismic quality factor q to range between 35 for the solid quartzite and 80 for the porous dry targets for water saturated target materials q is much lower 10 the obtained values are in the range of literature values translating the seismic efficiency into seismic magnitudes we show that the seismic magnitude of an impact event is about one order of magnitude smaller considering a water saturated target in comparison to a solid or porous target obtained seismic magnitudes decrease linearly with distance to the point of impact and are consistent with empirical data for distances closer to the point of impact the seismic magnitude decreases more rapidly with distance for a water saturated material compared to a dry material

the global effects of impact induced seismic activity on fractured asteroid surface morphology abstract impact induced seismic vibrations have long been suspected of being an important surface modification process on small satellites and asteroids in this study we use a series of linked seismic and geomorphic models to investigate the process in detail we begin by developing a basic theory for the propagation of seismic energy in a highly fractured asteroid and we use this theory to model the global vibrations experienced on the surface of an asteroid following an impact these synthetic seismograms are then applied to a model of regolith resting on a slope and the resulting downslope motion is computed for a full range of impactor sizes next this computed downslope regolith flow is used in a morphological model of impact crater degradation and erasure showing how topographic erosion accumulates as a function of time and the number of impacts finally these results are applied in a stochastic cratering model for the surface of an eros like body same volume and surface area as the asteroid with craters formed by impacts and then erased by the effects of superposing craters ejecta coverage and seismic shakedown this simulation shows good agreement with the observed 433 eros cratering record at a main belt exposure age of 400 200 myr including the observed paucity of small craters the lowered equilibrium numbers loss rate production rate for craters less than 100 m in diameter is a direct result of seismic erasure which requires less than a meter of mobilized regolith to reproduce the near observations this study also points to an upper limit on asteroid size for experiencing global surface modifying seismic effects from individual impacts of about 70 100 km depending upon asteroid seismic properties larger asteroids will experience only localized regional seismic effects from individual impacts

a high resolution calibration of sr ca thermometry using the caribbean coral montastraea annularis 1 a relationship has been established between the sr ca ratio in the skeleton of the scleractinian coral montastraea annularis and sea surface water temperature in south florida in order to obtain this correlation specimens of montastraea annularis were transplanted to a site at a local reef where every two to three months throughout a 2 year period the corals were stained with alizarin red s and where water temperature which annually ranges between 20 and 30 c was continually monitored at the end of the experimental period the coral skeleton was sampled at a rate of 50 samples per year each sample corresponding to only around 20 g of calcium carbonate for the 2 5 year period the sr ca ratio exhibited excellent correlation in the first year r2 0 83 sr ca mmol mol 10 11 0 0452 sst c but a rather poorer correlation in the second year r2 0 68 sr ca mmol mol 10 09 0 0406 sst c averaging the data into monthly values for year 1 we determined a relationship of sr ca mmol mol 10 165 0 0471 sst c on the basis of the excellent correlation between temperature and sr ca we feel that this relationship is the most accurate discrepancies in the second year are suggested to arise from slight sampling errors relative to the stain lines

impact of biomineralization processes on the mg content of foraminiferal shells a biological perspective the mg ca ratio in foraminiferal shells is widely used as a proxy for paleotemperatures nevertheless it seems that the basic mg content of foraminifera is determined by biological factors as can be concluded from the large inter species and intrashell variability and the frequent deviations from inorganic behavior this paper discusses three possible ways by which foraminifera can control or modify the mg content in their shell 1 involvement of organic matrix in the precipitation process that may alter the partition coefficient of mg in biogenic calcite 2 controlled conversion of transient amorphous phases to calcite and 3 modification of the mg concentration in the parent solution from which the crystals precipitate the first two mechanisms are probably responsible for the precipitation of high mg calcite phases whole shell or sublayers while the third mechanism leads to the formation of low mg calcite phases we propose a model adapted from epithelial cells that allows massive mg2 removal from the biomineralization site this model is especially relevant to the planktonic and deep benthic low mg foraminifera that are frequently used for paleotemperature reconstructions we discuss the possible biological roles of mg in the shell in terms of the calcite polymorph conservation the in vivo chemical stability of the shell the functions of mg as a stabilizer of transient phases and as a controlling agent of the precipitation process several temperature sensitive biological processes that may influence the mg ca ratio of the shell are suggested and a model that combines biogenic and inorganic considerations is presented the model uses mg heterogeneity in the shell together with temperature response biologic and inorganic of biomineralization processes to account for the deviation of planktonic foraminifera from inorganic calcite at equilibrium with seawater

excess dissolved ca in the deep ocean a hydrothermal hypothesis abstract variations in seawater alkalinity and dissolved calcium provide information essential to establishing the integrated deep ocean calcium carbonate dissolution flux high precision ca measurements reported here confirm earlier suggestions that the deep ocean contains higher levels of dissolved ca than expected from calcium carbonate dissolution only i propose that the mid depth ca excess is a manifestation of the circulation of seawater through hydrothermal systems at mid ocean ridges qualitative agreement with 3 he distributions and evidence for deep water mg depletions support this hypothesis the magnitude of the mid depth ca excess implies a total hydrothermal flux larger than expected from the corresponding excess in 3 he and points to the relative importance of low temperature diffuse fluxes versus high temperature discrete fluxes for elements such as ca the implied total hydrothermal flux for ca is consistent with its oceanic mass balance requirements and resolves several long standing problems associated with our understanding of the chemical evolution of the ocean and in particular its low alkaline content

the geology of 433 eros the global high resolution imaging of asteroid 433 eros by the near earth asteroid rendezvous near shoemaker spacecraft has made it possible to develop the first comprehensive picture of the geology of a small s type asteroid eros displays a variety of surface features and evidence of a substantial regolith large scale facets grooves and ridges indicate the presence of at least one global planar structure directional and superposition relations of smaller structural features suggest that fracturing has occurred throughout the object as with other small objects impact craters dominate the overall shape as well as the small scale topography of eros depth diameter ratios of craters on eros average 0 13 but the freshest craters approach lunar values of 0 2 ejecta block production from craters is highly variable the majority of large blocks appear to have originated from one 7 6 km crater shoemaker the interior morphology of craters does not reveal the influence of discrete mechanical boundaries at depth in the manner of craters formed on lunar mare regolith and on some parts of phobos this lack of mechanical boundaries and the abundant evidence of regolith in nearly every high resolution image suggests a gradation in the porosity and fracturing with depth the density of small craters is deficient at sizes below 200 m relative to predicted slopes of empirical saturation this characteristic which is also found on parts of phobos and lunar highland areas probably results from the efficient obliteration of small craters on a body with significant topographic slopes and a thick regolith eros displays a variety of regolith features such as debris aprons fine grained ponded deposits talus cones and bright and dark streamers on steep slopes indicative of efficient downslope movement of regolith these processes serve to mix materials in the upper loose fragmental portion of the asteroid regolith in the instance of ponded materials and crater wall deposits there is evidence of processes that segregate finer materials into discrete deposits the near observations have shown us that surface processes on small asteroids can be very complex and result in a wide variety of morphologic features and landforms that today seem exotic future missions to comets and asteroids will surely reveal still as yet unseen processes as well as give context to those discovered by the near shoemaker spacecraft

experimental determination of trace element partition coefficients in cultured benthic foraminifera abstract we present the first trace metal partition coefficients obtained from reproducing cultures of deep sea benthic foraminifera paleoceanographically important species including juvenile bulimina marginata cibicidoides pachyderma and uvigerina peregrina were maintained in sediment microcosms at 10 c 35 psu and ph 8 for 1 3 years juvenile foraminifera were separated cleaned and dissolved under clean conditions for determination of trace metal partition coefficients on recently deposited 1 3 months foraminiferal calcite in addition to the deep sea species we analyzed a shallow water benthic foraminifer ammonia beccarii overlying water samples were collected from the microcosms concurrent to the period of calcification 3 months prior to separation ba ca partition coefficients d ba were measured in replicate for benthic foraminifera species bulimina marginata 0 24 0 07 uvigerina peregrina 0 24 0 06 ammonia beccarii 0 20 0 04 the d ba for bulimina marginata and uvigerina peregrina were found to closely match the range from the ontong java plateau sample size limitations allowed for only one analysis of d ba for cibicidoides pachyderma however our nonreplicated d ba of 0 5 0 1 falls within the accepted range of core top samples 0 37 0 06 we report a d cd for ammonia of 1 0 0 5 for cibicidoides of 4 2 for bulimina of 3 1 and for uvigerina 2 1 which all fall within the ranges reported for core top calibrations the large uncertainties in d cd reflect variation in dissolved cd concentration in the artificial seawater reservoir due to loss and replacement of cd during the course of the experiment the variability between species is probably the result of variability in pore water cd in the sediment culture system and may reflect habitat effects

magnesium and strontium compositions of recent symbiont bearing benthic foraminifera abstract minor and trace elements in foraminiferal carbonates are potential paleo proxies of climate nutrient and seawater composition there are very few reports of trace element composition of symbiont bearing larger foraminifera that are known to be important constituents of shallow marine modern and ancient carbonates in this paper we examine the range of variation in mg and sr content of recent species of these foraminifera from a lagoon of lakshadweep atoll indian ocean and akajima islands japan two hyaline species amphistegina lessonii and neorotalia calcar and two porcellaneous species amphisorus hemprichii and marginopora vertebralis were collected live from lakshadweep islands mg ca in these foraminifera is of an order of magnitude higher than the values reported for planktonic and symbiont free benthic foraminifera the sr ca values are however comparable with the reported values in other foraminiferal taxa and they are found to vary within a narrow range electron probe micro analysis of three symbiont bearing benthic species indicates spatial heterogeneity of high orders in mg ca composition in all the species the annual variation in temperature and ph of the lagoon water cannot explain the observed amplitude of the compositional variation the photosynthesis and respiration of the symbionts and host foraminifera are possibly the major cause of compositional heterogeneity in individual tests as has also been recently postulated for symbiont bearing planktonic foraminiferal species it highlights the need to isolate biological factors and necessitates species specific paleotemperature scale in paleoclimatic analysis we also analyzed 18 o 13 c ca mg and sr in carefully dissected chambers of a reef dwelling porcellaneous benthic foraminifer marginopora kudakajimaensis collected live in four seasons a moderate positive correlation is observed between mg ca and temperature however large inter and intra test variation in mg limits the precision of mg ca as palaeotemperature proxy the sr ca of the test calcite is unrelated to temperature of the sea water the 13 c of m kudakajimaensis does not correlate with 18 o mg ca or sr ca

experimental study on impact induced seismic wave propagation through granular materials abstract impact induced seismic waves are supposed to cause movements of regolith particles resulting in modifications of asteroidal surfaces the imparted seismic energy is thus a key parameter to determining the scale and magnitude of this seismic shaking process it is important to study the propagation velocity attenuation rate and vibration period of the impact induced seismic wave to estimate the seismic energy hence we conducted impact cratering experiments at kobe university using a 200 m glass beads target to simulate a regolith layer and measured the impact induced seismic wave using three accelerometers set on the target surface at differences ranging from 3 2 to 12 7 cm the target was impacted with three kinds of projectiles at 100 m s 1 using a one stage gas gun the propagation velocity of the seismic wave in the beads target was 108 9 m s 1 and the maximum acceleration gmax in the unit of m s 2 measured by each accelerometer showed good correlation with the distance from the impact point normalized by the crater radius x r irrespective of projectile type they also were fitted by one power law equation gmax 102 19 x r 2 21 the half period of the first peak of the measured seismic waves was 0 72 ms and this duration was almost consistent with the penetration time of each projectile into the target according to these measurements we estimated the impact seismic efficiency factor that is the ratio of seismic energy to kinetic energy of the projectile to be almost constant 5 7 10 4 inside the crater rim while it exponentially decreased with distance from the impact point outside the crater rim at a distance quadruple of the crater radius the efficiency factors were 4 4 10 5 for polycarbonate projectile and 9 5 10 5 for alumina and stainless steel projectiles

temperature and carbonate ion effects on mg ca and sr ca ratios in benthic foraminifera aragonitic species hoeglundina elegans received 16 march 2005 revised 20 june 2005 accepted 3 november 2005 published 21 february 2006 1 core top samples from atlantic little bahama banks lbb and pacific hawaii and indonesia depth transects have been analyzed in order to assess the influence of bottom water temperature bwt and aragonite saturation levels on mg ca and sr ca ratios in the aragonitic benthic foraminifer hoeglundina elegans both the mg ca and sr ca ratios in h elegans tests show a general decrease with increasing water depth although at each site the decreasing trends are consistent with the in situ temperature profile mg ca and sr ca ratios in lbb are substantially higher than in indonesia and hawaii at comparable water depths with a greater difference observed with increasing water depth because we find no significant difference between results obtained on live and dead specimens we propose that these differences are due to primary effects on the metal uptake during test formation evaluation of the water column properties at each site suggests that in situ co3 ion concentrations play an important role in determining the h elegans mg ca and sr ca ratios the co3 ion effect is limited however only to aragonite saturation levels dco3 aragonite below 15 mmol kg 1 above this level temperature exerts a dominant effect accordingly we propose that mg ca and sr ca in h elegans tests can be used to reconstruct thermocline temperatures only in waters oversaturated with respect to the mineral aragonite using the following relationships mg ca 0 034 0 002 bwt 0 96 0 03 and sr ca 0 060 0 002 bwt 1 53 0 03 for dco3 aragonite 1 5mmol kg 1 the standard error associated with these equations is about 1 1 c reconstruction of deeper water temperatures is complicated because in undersaturated waters changes in mg ca and sr ca ratios reflect a combination of changes in co3 and bwt overall we find that sr ca rather than mg ca in h elegans may be a more accurate proxy for reconstructing paleotemperatures

uranium in foraminiferal calcite as a recorder of seawater uranium concentrations abstract we present results of an investigation of uranium calcium ratios in cleaned foraminiferal calcite as a recorder of seawater uranium concentrations for accurate reconstruction of past seawater uranium content shell calcite must incorporate uranium in proportion to seawater concentration and must preserve its original uranium composition over time laboratory culture experiments with live benthic amphistegina lobifera and live planktonic globigerinella calida foraminifera show that the u ca ratio of cleaned calcite tests is proportional to the concentration of uranium in solution after correcting results for the presence of initial calcite the apparent distribution coefficient d u ca calcite u ca solution 10 6 0 3 10 3 for a lobifera and d 7 9 0 1 10 3 for g calida u ca ratios in planktonic foraminifera from core tops collected above 3900 m in the equatorial atlantic and above 2100 m in the pacific ocean show no significant difference among the species analyzed d estimated from core top samples ranges from 7 6 0 4 10 3 for o universa to 8 4 0 5 10 3 for g ruber in benthic species c wuellerstorfi d 7 0 0 8 10 3 u ca and mg ca in g tumida and g sacculifer from core tops taken near and below the regional lysocline decrease with water depth smaller decreases in u ca and mg ca with depth were observed in c wuellerstorfi in the planktonic species we believe that u ca and mg ca are lower in the more dissolution resistant fraction of calcite leading to lower u ca in more highly dissolved samples

temperature control on the incorporation of magnesium strontium fluorine and cadmium into benthic foraminiferal shells from little bahama bank prospects for thermocline paleoceanography surface sediments from little bahama bank lbb intersecting the subtropical thermocline were used to assess the influence of temperature on the incorporation of mg sr f and cd into shells of benthic foraminifera samples were obtained from twelve cores along the southern slope of lbb covering a temperature range of 18 4 5 c between 301 and 1585 m we studied the composition of ten calcitic and one aragonitic species which are often used in paleochemical reconstructions mg ca ratios decrease with increasing water depth in all benthic species both with calcitic and aragonitic mineralogy showing a strong correlation with water temperature similar decrease is seen in sr ca but with no correlation with temperature none of the benthic species studied here exhibits a depth or temperature related change in f ca similar trends are observed when using an ocean wide dataset which includes shallow and deep core tops 300 5000 m we suggest that temperature is the primary control on the mg content of benthic foraminifera based on inorganic precipitation experiments and thermodynamic considerations presented here a 30 40 decrease in the mg distribution coefficient in calcite may be expected as a result of a temperature change from 25 c to 5 c which is about half the observed change in lbb a calibration curve applied to c pachyderma data from core tops along the slope of little bahama bank suggests that water temperature may be inferred from mg ca ratios with an uncertainty of about 0 8 c therefore the mg content of benthic foraminifera may provide a new independent temperature proxy for studying shallow waters paleoceanography the linear decrease in sr ca with increasing depth is not correlated with temperature the trend is constant from the ocean surface down to 5 km suggesting that pressure related effects on the calcification process are a more likely explanation than post depositional dissolution mg ca ratios in aragonitic shells of h elegans covary with temperature in accord with recent observations from corals in contrast the sr and f chemistry of h elegans is very different than that of corals and inorganically precipitated aragonites the disparities between the elemental composition of biogenic and inorganic phases and the large intergeneric and interspecific differences observed both in planktonic and benthic foraminifera implicate temperature related physiological processes in regulating the coprecipitation of elements in foraminiferal shells our work demonstrates that cd ca ratios of shallow calcitic species reflect the vertical distribution of nutrients no significant influence of temperature on the partitioning of cd into the shells was found our data extend the previous deep water calibration boyle 1992 thereby allowing for the reconstruction of the nutrient chemistry of shallow thermocline waters

the impact of salinity on the mg ca and sr ca ratio in the benthic foraminifera ammonia tepida results from culture experiments abstract over the last decade sea surface temperature sst reconstructed from the mg ca ratio of foraminiferal calcite has increasingly been used in combination with the 18o signal measured on the same material to calculate the 18ow a proxy for sea surface salinity sss a number of studies however have shown that the mg ca ratio is also sensitive to other parameters such as ph or co 3 2 and salinity to increase the reliability of foraminiferal mg ca ratios as temperature proxies these effects should be quantified in isolation individuals of the benthic foraminifera ammonia tepida were cultured at three different salinities 20 33 and 40 psu and two temperatures 10 15 c the mg ca and sr ca ratios of newly formed calcite were analyzed by laser ablation icp ms and demonstrate that the mg concentration in a tepida is overall relatively low mean value per experimental condition between 0 5 and 1 3 mmol mol when compared to other foraminiferal species sr being similar to other foraminiferal species the mg and sr incorporation are both enhanced with increasing temperatures however the temperature dependency for sr disappears when the distribution factor dsr is plotted as a function of calcite saturation state this suggests that a kinetic process related to is responsible for the observed dependency of sr incorporation on sea water temperature the inferred relative increase in dmg per unit salinity is 2 8 at 10 c and 3 3 at 15 c for the salinity interval 20 40 psu this implies that a salinity increase of 2 psu results in enhanced mg incorporation equivalent to 1 c temperature increase the dsr increase per unit salinity is 0 8 at 10 c and 1 3 at 15 c for the salinity interval 20 40 psu

the cauchy 5 small low volume lunar shield volcano evidence for volatile exsolution eruption patterns and type 1 type 2 hybrid irregular mare patch formation the lunar shield volcano cauchy 5 sitting at the low diameter height volume end of the population is the only known example containing two different types of irregular mare patches imps in very close association 1 the pit crater interior type 1 imp composed of bleb like mounds surrounded by a hummocky and blocky floor unit and 2 type 2 imps small often optically immature pits less than 5 m deep located on the generally block deficient shield flanks a four phase lunar magma ascent eruption model predicts that during a relatively brief eruption low magma rise rates maximize volatile exsolution in lava filling the pit crater bubble rich magmas overtop the pit crater and form extremely vesicular flows on the shield flanks exposure of the flanking flows to vacuum produces a fragmental layer of exploded glassy bubble walls subsequent second boiling upon cooling of the flanking flow interiors releases additional volatiles which migrate and collect forming magmatic foams and gas pockets as magma rise rates slow trapped gas and magmatic foam build up below the cooling pit crater floor magmatic foams are extruded to form type 1 imp deposits type 2 imps on the flanks are interpreted to be due primarily to subsequent impacts causing collapse of the flow surface layer into the extremely vesicle and void rich flow interior anomalously young pit crater floor shield flank crater retention ages compared with surrounding maria ages may be due to effects of cauchy 5 substrate characteristics extreme micro and macroporosity foamy nature and glassy auto regolith on superposed crater formation and retention

a cenozoic seawater sr ca record from benthic foraminiferal calcite and its application in determining global weathering fluxes a cenozoic multi species record of benthic foraminiferal calcite sr ca has been produced and is corrected for inter specific offsets typically less than 0 3 mmol mol and for the linear relationship between decreasing benthic foraminiferal sr ca and increasing water depth the water depth correction determined from holocene late glacial maximum and eocene paleowater depth transects is not vert similar0 1 mmol mol km the corrected cenozoic benthic foraminiferal sr ca record ranges from 1 2 to 2 0 mmol mol and has been interpreted in terms of long term changes in seawater sr ca enabling issues related to higher resolution variability in sr ca to be ignored we estimate that seawater sr ca was not vert similar1 5 times modern values in the late cretaceous but declined rapidly into the paleogene following a minimum in the eocene seawater sr ca increased gradually through to the present day with a minimum superimposed on this trend centered in the late miocene by assuming scenarios for changing seawater calcium concentration and using published carbonate accumulation rate data combined with suitable values for sr partition coefficients into carbonates the seawater sr ca record is used to estimate global average river sr fluxes these fluxes are used in conjunction with the seawater strontium isotope curve and estimates of hydrothermal activity tectonic outgassing to calculate changes in global average river 87sr 86sr through the cenozoic the absolute magnitude of sr fluxes and isotopic compositions calculated in this way are subject to relatively large uncertainties nevertheless our results suggest that river sr flux increased from 35 ma to the present day roughly two fold accompanied by an overall increase in 87sr 86sr by not vert similar0 to 0 001 between 75 and 35 ma river 87sr 86sr also increased by not vert similar0 001 to 0 002 but was accompanied by a decrease two to three fold in river sr flux

environmental versus biological controls on mg ca variability in globigerinoides ruber white from core top and plankton tow samples in the southwest pacific ocean 1 laser ablation inductively coupled plasma mass spectrometry was used to analyze the individual chambers from tests of foraminiferal fossil and plankton tow globigerinoides ruber from the southwest pacific ocean from latitudes 3 s to 42 s the variability of mg ca between chambers of an individual intraindividual and individuals of the same population interindividual is such that when converted to temperature the extent of intra individual and interindividual variability appears to exceed that attributable to either calcification or seasonal temperature variability the pooled mean chamber mg ca from each core top and plankton tow site demonstrates a significant p 0 05 positive correlation with temperature we derive chamber specific calibrations where mg cach f 2 0 798 exp0 070 t mg cach f 1 0 891 exp0 067 t and mg cach f 0 590 exp0 072 t we do not observe any bias between the two morphotypes gs ruber ruber and gs ruber pyramidalis the chamber specific calibrations potentially offset mg ca based temperature reconstructions if used on bulk whole test mg ca or applied to misidentified chambers nevertheless these calibrations can be used to reliably estimate sea surface temperature although there is a general overriding temperature control on mg ca we show that removal of the effect of temperature at each site reveals a lognormal mg ca distribution this suggests that mg ca variability at each site is also affected by biological mechanism s that may control the distribution of interindividual mg ca in addition other te ca data al ca and mn ca from laser ablation trace element depth profiles can be used to identify detrital or diagenetic phases that may bias the trace element ca signal

seismic detection of meteorite impacts on mars abstract meteorite impacts provide a potentially important seismic source for probing mars interior it has recently been shown that new craters can be detected from orbit using high resolution imaging which means the location of any impact related seismic event could be accurately determined thus improving the constraints that could be placed on internal structure using a single seismic station this is not true of other seismic sources on mars such as sub surface faulting which require location using multiple seismic stations this study aims to determine the seismic detectability of meteorite impacts and assess whether they are a viable means of probing deep internal structure first we derive a relation between crater diameter and equivalent seismic moment based on observational data compiled from impact tests controlled explosions and earthquake seismology second this relation was combined with updated cratering rates based on newly observed craters to derive the impact induced seismicity on mars which we estimate to total 10 13 10 14 n m per year finally seismic waveform modelling was used to determine the detectability of these impacts based on reasonable assumptions about likely seismometer performance and background noise levels for our nominal noise instrument case we find that detectable impacts at teleseismic distances source receiver offsets greater than 60 are very rare and occur approximately once every 10 years for our most optimistic noise instrument case approximately one such event occurs each year this suggests that using solely meteorite impacts is not a reliable way of probing the martian interior although local impacts are more frequently detectable and could provide important constraints on near surface seismic properties

carbonate ion effect on mg ca sr ca and stable isotopes on the benthic foraminifera oridorsalis umbonatus off namibia abstract we investigate the influence of carbonate system parameters carbonate ion concentration co32 carbonate ion saturation co32 on the trace element and stable isotope ratios in the endobenthic foraminifera oridorsalis umbonatus data from modern core top samples from the namibian continental slope suggest that the shell composition of this species is influenced by the chemistry of the pore water for these organic rich sediments the impact of ocean bottom water properties on both pore water and shell chemistry is surprisingly small sr ca correlates positively with co32 and to a lesser extent with co32 which is opposed to previous results a co32 decrease of 10 mol kg leads to an increase of 0 05 mmol mol in sr ca we observe a correlation between shell 18o corrected for temperature and 18o seawater and co32 however the variability of the corrected 18o is close to the analytical limit no clear dependences were observed for 13c and mg ca

a biomineralization model for the incorporation of trace elements into foraminiferal calcium carbonate measurements of srca of benthic foraminifera show a linear decrease with water depth which is superimposed upon significant variability identified by analyses of individual foraminifera new data for cdca support previous work in defining a contrast between waters shallower and deeper than 2500 m measured element partition coefficients in foraminiferal calcium carbonate relative to sea water d have been described by means of a one box model in which elements are extracted by rayleigh distillation from a biomineralization reservoir that serves for calcification with a constant fractionation factor such that d 1 f 1 f where f is the proportion of ca remaining after precipitation a modification to the model recognises differences in element speciation the model is consistent with differences between dsr dba and dcd in benthic but not planktonic foraminifera depth variations in d for sr and ba are consistent with the model as are differences in depth variation of dcd in calcitic and aragonitic benthic foraminifera the shallower depth variations may reflect increasing calcification rates with increasing water depth to an optimum of about 2500 m observations of unusually lower dcd for some deep waters not accompanied by similar dsr or dba may be because of dissolution or a calcification response to a lower carbonate saturation state

sr ca in multiple species of planktonic foraminifera implications for reconstructions of seawater sr ca sr ca ratios were measured on eight species of planktonic foraminifera from a core top transect of the north atlantic five of the species globigerinoides ruber globigerina bulloides neogloboquadrina pachyderma globigerinoides sacculifer globigerinella siphonifera show remarkably little within species variability in sr ca 1 2 0 1 three globorotaliid species globorotalia hirsuta globorotalia inflata globorotalia truncatulinoides show somewhat greater variability 3 7 interspecies variations are of 10 the variability in globorotaliid sr ca is explained either by a greater temperature sensitivity than for other species or by depth dependent dissolution other than this effect the overwhelming control on foraminiferal sr ca appears to be seawater sr ca in contrast time series sr ca records of four species from a north atlantic sediment core over a glacial interglacial cycle show very significant differences n pachyderma shows large amplitude changes in sr ca 9 7 in phase with 18o whereas g ruber shows the smallest amplitude changes 2 6 out of phase with 18o and most similar to model predictions for temporal changes in seawater sr ca records of g inflata and g bulloides are intermediate amplitude changes of 3 3 4 7 and out of phase with 18o the lack of coherence in the time series records between the species shows that factors in additional to changing seawater sr ca must affect planktonic foraminiferal sr ca

the relationship between shell size and mg ca sr ca δ18o and δ13c of species of planktonic foraminifera the relationship between shell size and mg ca sr ca 18o and 13c of planktonic foraminiferal calcite has been investigated using seventeen species in six different size fractions mg ca increases and sr ca decreases with increasing size except for two globorotaliid species which show the opposite trend the changes in mg ca broadly follow 18o calcification temperatures except that surface and near surface dwelling species show larger changes in mg ca than can be accounted for by differences in calcification temperature derived from 18o the increases in mg ca and decreases in sr ca vary linearly with the well established increase in 13c with size this is consistent with smaller individuals calcifying faster than larger individuals and larger individuals forming calcite that more closely reflects seawater temperature and composition it appears that variations in calcification rate affect mg and sr shell chemistry the observations may account for part of the temporal variability in foraminiferal sr ca within a single size fraction that has been attributed to changes in seawater sr ca

timescale of asteroid resurfacing by regolith convection resulting from the impact induced global seismic shaking abstract a model for the asteroid resurfacing by regolith convection is built to estimate its timescale in the model regolith convection is driven by the impact induced global seismic shaking the model consists of three steps i intermittent impact of meteoroids ii impact induced global vibration seismic shaking and iii vibration induced regolith convection in order to assess the feasibility of the resurfacing process driven by regolith convection we estimate the resurfacing timescale as a function of the size of a target asteroid in the estimate a set of parameter values is assumed on the basis of previous works however some of them e g seismic quality factor q seismic efficiency and seismic frequency f are very uncertain although these parameter values might depend on asteroid size we employ the standard values to estimate the representative behavior to clarify the parameter dependences we develop an approximated scaling form for the resurfacing timescale according to the estimated result we find that the regolith convection based resurfacing timescale is shorter than the mean collisional lifetime in most of the parameter uncertainty ranges these parameter ranges are within those reported by previous works for small asteroids this means that the regolith convection can be a possible mechanism for the asteroid resurfacing process

an artificial impact on the asteroid 162173 ryugu formed a crater in the gravity dominated regime the hayabusa2 spacecraft investigated the small asteroid ryugu which has a rubble pile structure we describe an impact experiment on ryugu using hayabusa2 s small carry on impactor the impact produced an artificial crater with a diameter 10 meters which has a semicircular shape an elevated rim and a central pit images of the impact and resulting ejecta were recorded by the deployable camera 3 for 8 minutes showing the growth of an ejecta curtain the outer edge of the ejecta and deposition of ejecta onto the surface the ejecta curtain was asymmetric and heterogeneous and it never fully detached from the surface the crater formed in the gravity dominated regime in other words crater growth was limited by gravity not surface strength we discuss implications for ryugu s surface age

impacts on asteroids fragmentation regolith transport and disruption abstract we use a numerical hydrocode model to examine the outcomes of various size impacts into targets the sizes of asteroids 951 gaspra and 243 ida which were imaged by the galileo spacecraft a shock wave fractures the asteroid in advance of crater excavation flow thus for impactors larger than 100 m impacting at 5 3 km s 1 tensile strength is unimportant in these bodies whether they are initially intact or are rubble piles because of the shock induced fracture impact results are controlled by gravity therefore these asteroids are much more resistant to catastrophic disruption than predicted by previous estimates which had assumed that strength was controlling these processes for rock targets the rubble and regolith produced by this fracture can be jolted by the impact redistributing surface material and globally erasing craters the crater ejecta can produce tens of meters of regolith per large event likely consisting of 100 m size boulders mixed with smaller particles the response of kilometer size asteroids to impacts is qualitatively different from that of few centimeter targets in terrestrial experiments making prediction based on such experiments difficult the compositional distribution of delivered meteorites depends on the outcomes of such asteroid impacts

measurements of seismic waves induced by high velocity impacts implications for seismic shaking surrounding impact craters on asteroids abstract on asteroids impact induced seismic shaking is an important geological process related to the modifications of the surface features that are due to the movement of regolith grains on the asteroid surface mass movements caused by seismic shaking e g landslides and crater erasures were recently observed by several spacecrafts to elucidate the seismic shaking areas induced by impacts on asteroids it is necessary to determine the excitation and the decay processes of impact induced seismic waves here we conducted impact cratering experiments using 500 m quartz sand to simulate an asteroid surface at the institute of space and astronautical science isas japan aerospace exploration agency jaxa we used 4 75 mm and 2 mm diameter projectiles with density from 14 9 to 1 2 g cm 3 the impact velocity ranged from 7 to 0 2 km s 1 we measured the acceleration waveform by using three to five accelerometers setting on the target surface and we examined three parameters characterizing the impact induced seismic wave with varying distances from the impact point the propagation velocity vprop the maximum acceleration gmax and the half period of the first upward peak thalf the vprop was obtained to be 52 4 7 2 m s 1 regardless of the impact velocity and the projectile properties and the thalf slightly depended on the impact velocity as v i 0 14 but was independent of the projectile properties the gmax had a close relationship with the distance from the impact point normalized by the crater rim radius x rrim regardless of the impact velocity and the projectile properties the obtained empirical equation was shown as gmax 102 21 x rrim 3 18 by using the empirical equations we obtained herein we observed that the seismic energy normalized by the kinetic energy of a projectile es ek decreased with the increase of the normalized distance x rrim we also estimated the area of impact induced seismic shaking on an idealized small 500 m in diameter body at the impact velocity of 5 km s 1