gravity field determination and characteristics retrospective and prospective gravimetry has had a long history using pendulums torsion balances and static spring gravimeters relative accuracy adequate for many geophysical problems was already attained by 1900 but it took another half century to build readily portable gravimeters calibration and datum definition remained problems until the 1970s when free fall absolute gravimeters were developed that now have a precision of 10 3 mgal the problems of geographic inaccessibility and field party costs notably in areas of greatest tectonic interest are now being overcome by airborne gravimetry that has already achieved accuracies of 1 3 mgal with resolutions of 10 to 20 km satellite techniques are the best way to determine the long wavelength variations of the gravity field the resolution of the models has steadily improved with the number of satellites and the precision of the observations the best current model includes tracking data from more than 30 satellites satellite altimetry and surface gravimetry and has a resolution of about 290 km harmonic degree 70 with the most recent improvements coming from doppler orbitography and radiopositioning integrated by satellite doris tracking of the spot 2 satellite and satellite laser ranging slr doris and global positioning system gps tracking of the topex poseidon satellite meanwhile radar altimetry has become the dominant technique to infer the marine geoid with a resolution of tens of kilometers or shorter similarly the gravity fields of the moon venus and mars have been determined to harmonic degrees 70 75 and 50 respectively although tracking limitations result in variations of spatial resolution modeling earth s gravity field from the abundance of precise data has become an increasingly complex task with which the development of computer capacity has kept pace contemporary solutions now entail about 10 000 parameters half of them for effects other than the fixed gravity field of earth temporal variations arising from tides have long been well modeled and nontidal changes are now being identified the improvement in gravitational models engendered corresponding advances in geophysical interpretation isostatic models were refined and expanded to account for regional thermal and tectonic histories interpretation of the long wavelength gravity field determined by satellite techniques has been mainly in terms of plate tectonics as a manifestation of mantle convection gravity has been significant in inferring that there must be a large increase in viscosity with depth most strongly from the apparent slow sinking of subducted slabs the prospects for increasing accuracy and resolution in the determination of earth s gravity field rest primarily with the development of new measurement systems airborne gravimetry is taking promising new steps using gps but significant global model improvement awaits a dedicated satellite gravimetry system and future satellite altimeter missions will do more for ocean dynamics studies than geoid improvement advances in interpretation will occur through the development of other data such as seismic tomography and larger scale computer modeling of tectonics and convection

an evaluation of controls on planktonic foraminiferal sr ca comparison of water column and core top data from a north atlantic transect sr ca in planktonic foraminifera recovered from the water column over 0 800 m along a meridional transect in the north atlantic ocean from 30 to 60 n were compared with data from core top samples on the same transect and with in situ temperatures determined from water column ctd profiles species belonging to the globorotaliid genus show significant variability in sr ca from place to place whereas non globorotaliid species show no significant variability this variability for the globorotaliid species in core top samples has already been shown to covary with calcification temperature derived from 18o but it also covaries with bottom depth symptomatic of a dissolution artifact these alternatives are distinguishable from the water column data for which the globorotaliid species show a small temperature dependence of 0 025 mmol mol c within the range 5 15 c however temperature dependence is not supported by glacial interglacial differences in sr ca for globorotaliid and non globorotaliid species and at least from this perspective a co3 2 influence seems more likely

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

planktic foraminiferal sedimentation and the marine calcite budget 1 the vertical flux and sedimentation rate of planktic foraminiferal tests are quantified and a global planktic foraminiferal cac0 3 budget is presented test and calcite flux rates are calculated according to the distribution of species obtained from multinet and sediment trap samples modern planktic foraminiferal population dynamics are discussed as a prerequisite for the quantification of the calcite budget highlighting the importance of ecological autecological e g reproduction and biogeochemical conditions that determine the presence or absence of species to complete the open marine particulate caco 3 inventory the contribution of coccolithophores pteropods and calcareous dinophytes is discussed based on the studied regions the global planktic foraminiferal calcite flux rate at 100 m depth amounts to 1 3 3 2 gt yr 1 equivalent to 23 56 of the total open marine caco 3 flux the preservation of tests varies on a regional and temporal scale and is affected by local hydrography and dissolution during most of the year off peak periods many tests dissolve above 700 m water depth while settling through the water column with on average only 1 3 of the initially exported caco 3 reaching the deep seafloor pulsed flux events mass dumps of fast settling particles yield a major contribution of tests to the formation of deep sea sediments on average 25 of the initially produced planktic foraminiferal test cac0 3 settles on the seafloor the total planktic foraminiferal contribution of caco 3 to global surface sediments amounts to 0 36 0 88 gt yr 1 32 80 of the total deep marine calcite budget

1991 1992 gps measurements across the nepal himalaya in march 1991 35 control points were measured in the collision zone between the indian and asian plates using the global positioning system gps twenty eight points are located in the nepal himalaya and 7 in s and e tibet in october 1992 6 of the nepal points were remeasured together with 3 bedrock points in bihar state india 5 points in e tibet and one in urumchi the average wrms gps position repeatability between 1991 and 1992 improved from 8 mm to 5 mm in the north 16 mm to 7 mm in the east and 32 mm to 25 mm in the vertical components himalayan convergence rates of 20 mm yr may be resolved to 10 accuracy within 5 years with these uncertainties unless improved vertical measurement techniques are introduced many decades must elapse before regional secular vertical motions may be resolved the 1991 3 1992 8 measurements are consistent with geologically determined himalayan convergence rates of less than 20 mm year

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

variability of mg ca and sr ca between and within the planktonic foraminifers globigerina bulloides and globorotalia truncatulinoides the variability in mg ca and sr ca within individual tests and chambers of tests and samples consisting of differing numbers of individuals was determined for globigerina bulloides and globorotalia truncatulinoides in a north atlantic core top sample 52 918 n 16 917 w the variability in mg ca and sr ca within individual tests and chambers was determined by electron microprobe and samples consisting of variable sample size were measured using inductively coupled plasma optical emission spectrometer icp oes large compositional heterogeneity was found within individual chambers and within the test as a whole of the two species and the presence of regions with up to 10 mmol mol mg ca especially in g bulloides mean mg ca decreases in successive chambers of g bulloides especially the 300 355 m fraction and is accompanied by decreasing variance but is not statistical significant sr ca is much more homogeneously distributed with a normal distribution and shows no differences from chamber to chamber the variability of mg ca and sr ca decreases with increasing sample size from single to five to twenty tests per sample approximately as for a normal distribution with greater variability for g bulloides than for g truncatulinoides equivalent to uncertainties in temperature n 20 of 1 1 c and 0 7 c for the two species within the whole of the sediment mixed layer

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

deep sea temperature and ice volume changes across the pliocene pleistocene climate transitions earth has undergone profound changes since the late pliocene which led to the development 2 7 million years ago ma and intensification 0 9 ma of large scale northern hemisphere ice sheets recorded as transitions in the benthic foraminiferal oxygen isotope 18ob record here we present an orbitally resolved record of deep ocean temperature derived from benthic foraminiferal magnesium calcium ratios from the north atlantic which shows that temperature variations are a substantial portion of the global 18ob signal the record shows two distinct cooling events associated with the late pliocene lpt 2 5 to 3 ma and mid pleistocene mpt 1 2 to 0 85 ma climate transitions whereas the lpt increase in ice volume is attributed directly to global cooling the shift to 100 000 year cycles at the mpt is more likely to be a response to an additional change in ice sheet dynamics

an estimate of equatorial gravity from terrestrial and satellite data equatorial gravity has been estimated from terrestrial gravity data and from satellite implied data the terrestrial estimate was based on the analysis of 43271 1 1 mean free air gravity anomalies the value estimated was 978032 35 0 5 mgals this value may be slightly 0 to 1 5 mgals too low because of the neglect of the downward continuation of surface free air anomalies to the geoid an alternate estimate based on the comparison of terrestrial anomalies and altimeter derived anomalies yields 978032 6 mgals equatorial gravity from space data depends on gm from lageos and lunar laser data and on a new estimate 6378136 2 0 5 m of the equatorial radius based on doppler tracking station positions and a new spherical harmonic expansion of the earth s gravity field to degree 360 the resultant equatorial gravity is 978032 78 0 2 mgals the difference between the two terrestrial estimates is 0 4 and 0 2 mgals or 0 4 ppm or 0 2 ppm the agreement is within the accuracy of the two separate estimates these comparisons can put constraints on parameters of non newtonian force models

variations in mg ca and sr ca ratios of planktonic foraminifera caused by postdepositional dissolution evidence of shallow mg dependent dissolution a comparative study has been made of two species of planktonic foraminifera g tumida and g sacculifer in a depth transect on the ontong java plateau western equatorial pacific g tumida tests from core top sediments showed decreasing mg ca 2 65 1 25 mmol mol and sr ca 1 50 1 16 mmol mol ratios with increasing water depth 1600 4400 m while no such variation was found in g sacculifer tests in excess of 355 m average mg ca 3 6 mmol mol sr ca 1 4 mmol mol artificial dissolution of g tumida tests led to a decrease in both mg ca and sr ca but in g sacculifer there was no significant change in the ratios analyses by electron microprobe revealed that mg ca of the inner chamber calcite in g tumida tests was much higher than that of the calcite crust keel whereas sr ca was only slightly elevated there were no consistent spatial differences in either mg ca or sr ca for g sacculifer tests dissolution in the oceans gives rise to the removal of the chamber calcite in g tumida about 30 of the total calcite leaving the keel calcite although g tumida is thought of as a dissolution resistant form the majority of mg ca and sr ca depletion and chamber loss occurs above the lysocline it is also possible that much of the mg enriched gametogenic calcite has been lost by dissolution from g sacculifer above 1600 m mg content has a significant effect on the dissolution susceptibility of planktonic foraminifera calculations show that the saturation horizon for mg rich parts of tests may be elevated by several hundred meters compared with normal calcite

absolute gravity a reconnaissance tool for studying vertical crustal motions a major effort is underway to develop highly portable absolute gravimeters having an ultimate accuracy of 3 5 gal an accuracy which translates into a height sensitivity of several centimeters we are just finishing the construction of six such units measurements at the joint institute for laboratory astrophysics with one of these new instruments agree well with the earlier measurements made in 1981 and 1982 with a previous generation instrument recent measurements at the international bureau of weights and measures in sevres france as a part of an international intercomparison of absolute gravimeters also show good agreement with the other instruments

controls on shell mg ca and sr ca in cultured planktonic foraminiferan globigerinoides ruber white mg ca and sr ca ratios were determined on a single species of planktonic foraminiferan globigerinoides ruber white collected from the gulf of eilat and cultured in seawater at five different salinities 32 to 44 five temperatures 18 to 30 c and four ph values 7 9 to 8 4 the mg ca temperature calibration of cultured g ruber with an exponential slope of 8 3 c agrees well with previously published calibrations from core tops and sediment traps however the dependence of mg ca on salinity with an exponential slope of 5 3 psu is also significant and should be included in the calibration equation with this purpose we calculated a calibration equation for g ruber dependent on both temperature and salinity within the 95 confidence limits mg ca mmol mol exp 0 06 0 02 s psu 0 08 0 02 t c 2 8 1 0 r2 0 95 the influence of ph on mg ca ratios is negligible at ambient seawater ph 8 1 to 8 3 however we observe a dominating ph control on shell mg ca when the ph of seawater is lower than 8 0 sr ca in g ruber shows a significant positive correlation with average growth rate presumably part of the variability in shell sr ca in the geological record is linked to changes in growth rates of foraminifera as a response to changing environmental conditions

independent impacts of calcium and carbonate ion concentration on mg and sr incorporation in cultured benthic foraminifera abstract laboratory culture experiments were conducted to determine effects of seawater carbonate ion concentration co32 and thereby calcite saturation state on mg and sr incorporation into calcite of two species of shallow water benthic foraminifera ammonia tepida and heterostegina depressa impact on mg and sr incorporation by increased seawater co32 and thereby higher is absent in either species comparison to results from a similar culturing experiment in which was varied as a function of ca2 reveals that saturation state affects incorporation of mg and sr through calcium rather than carbonate availability the similarity in response by both species is surprising since the average mg ca ratio is 70 times higher in h depressa than in a tepida furthermore these results suggest that the ions involved in biomineralization i e ca2 and dic are processed by separate cellular transport mechanisms the similar response of mg and sr incorporation in this study suggests that only differences in the ca2 transport mechanism affect divalent cation partitioning

epeirogeny and eustatic sea level changes as inferred from cretaceous shoreline deposits applications to the central and western united states uplift and subsidence histories of continental margins are by now reasonably well understood in the context of plate tectonics but the epeirogenic movements of continental interiors have been neither well documented nor properly understood epeirogenic movements are important to recognize when reconstructing paleogeography and may yield information regarding mantle dynamics and the amplitudes wavelengths and rates of lithospheric flexure sediments deposited at or near sea level can be used as a worldwide datum against which to measure postdepositional epeirogenic movements the present elevations of shoreline sediments of epicontinental seas deposited during sea level highstands at particular times in the past define a warped surface documenting subsequent epeirogeny of continental interiors when the amplitude of sea level rise during transgression is small relative to the observed epeirogenic motions the diachronous shoreline deposits represented in the entire transgressive surface can be used as a datum in the analysis thus greatly augmenting the available data and areal coverage if a stable frame of reference can be defined a eustatic sea level correction can be applied to every continent the elevation of the upper cenomanian mid cretaceous shoreline gives little evidence of warping tilting or uplift in central cratonic north america but indicates that a large area of the western united states including the colorado plateau has undergone more than 2 km of post cenomanian epeirogenic uplift

absolute gravity measurements in california 1984 1989 repeated absolute gravity measurements have been made at 12 sites in california between 1984 3 and 1989 7 as determined in laboratory tests the instrument used has an estimated accuracy of 10 gal approximately 10 8 g the repeatability of the measurements is consistent with this accuracy assessment no gravity changes above the limits set by instrumental uncertainty and environmental noise are observed in california during this period the field observations provide upper limits on the rates of secular gravity changes which could be attributed to crustal deformation with a resolution corresponding to vertical displacement rates of 1 2 cm yr

micromapping of mg ca values in cultured specimens of the high magnesium benthic foraminifera 1 this study measured mg ca values in cross sections of the benthic foraminifer planoglabratella opercularis d orbigny using an electron probe microanalyzer epma spot size 2 m 1000 analyses we cultured clonal juveniles of this species under controlled temperatures this species precipitates high magnesium calcite as its test material mean mg ca values increased linearly with the culture temperature therefore mg ca values in walls of subsequently formed chambers reflected changes in temperature during the experiment foraminiferal specimens yielded variable mg ca values within their test walls which resulted from the pattern of chamber formation and from minor variations of mg ca within one chamber wall

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

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

earthquakes and sea level space and terrestrial metrology on a changing planet the complacency with which man inhabits continent ocean margins or plate boundaries is based on the assumption that sea level rise and periodic seismicity are acceptable risks the forecast of future sea level or future seismicity is essential for informed assessment of these risks the historical data from which forecasts may be derived are in each case of limited antiquity and uneven spatial distribution developments in space geodesy and crustal deformation metrology in the past two decades offer the means to acquire a homogeneous global data set for monitoring relative vertical and horizontal motions of the earth s surface to within several millimeters these new tools are reviewed in terms of their application to forecasting trends in sea level rise and forecasting damaging earthquakes

variability of the gravity to height ratio due to surface loads we study the ratio between the gravity variation and vertical displacement on the surface of a self gravitating earth model when a surface load is applied we adopt a theoretical and numerical point of view excluding any observations first we investigate the spectral behavior of the ratio of the harmonic components of the gravity variation and vertical displacement then we model the gravity to height ratio for different surface loads continental hydrology atmospheric pressure ocean tides using outputs of global numerical models in order to relate the predicted spatial values to theoretical mean values deduced from the spectral domain for locations inside loaded areas the ratio is highly variable because of the newtonian attraction of the local masses and depends on the size of the load for the hydrological loading soil moisture and snow the mean ratio over the continents is 0 87 gal mm 1 but increases with decreasing size of the river basins for the atmospheric loading assuming an inverted barometer response of the ocean the ratio is positive with larger values for high latitudes 0 49 gal mm 1 particularly on the coasts than for lower latitudes 0 30 gal mm 1 the ratio however is much less variable outside the loaded areas in desert areas such as the sahara and arabia its mean value is 0 28 gal mm 1 for the ocean tidal loading we find a mean ratio of 0 26 gal mm 1 over the continents for the diurnal tidal waves both results are close to the theoretical mean value of 0 26 gal mm 1 combining elastic and remote attraction contributions

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

atmospheric carbon dioxide concentration across the mid pleistocene transition the dominant period of pleistocene glacial cycles changed during the mid pleistocene from 40 000 years to 100 000 years for as yet unknown reasons here we present a 2 1 million year record of sea surface partial pressure of co2 pco2 based on boron isotopes in planktic foraminifer shells which suggests that the atmospheric partial pressure of co2 pco2 was relatively stable before the mid pleistocene climate transition glacial pco2 was approximately 31 microatmospheres higher before the transition more than 1 million years ago but interglacial pco2 was similar to that of late pleistocene interglacial cycles 450 000 years ago these estimates are consistent with a close linkage between atmospheric co2 concentration and global climate but the lack of a gradual decrease in interglacial pco2 does not support the suggestion that a long term drawdown of atmospheric co2 was the main cause of the climate transition

contemporary plate motion and crustal deformation the measurement of relative plate velocities during the past few years is a signal accomplishment in earth science leading to refinement of the precepts of steady motion of plate interiors and cyclic deformation along plate margins regrettably deformation premonitory to an earthquake has yet to be detected with confidence delineation of the spatial and temporal buildup of strain between earthquakes however has put limits on models of the earthquake cycle a diverse set of fault structures and crustal rheologic conditions can explain the pattern of surface strain accumulation and release along strike slip faults in contrast the geometry of thrusts and normal faults revealed by earthquake deformation has been found to differ markedly from expectations geodetic observations have proved vital to monitor the ascent of magma through the earth s crust and to predict volcanic eruptions at the earth s surface episodic vertical and horizontal deformation in southern california remains a subject of dispute if anything it is less certain than it once seemed

the mg ca temperature relationship of benthic foraminiferal calcite new core top calibrations in the 4 c temperature range abstract calcite magnesium calcium ratios were determined for four species of benthic foraminifera cibicidoides wuellerstorfi cibicidoides mundulus oridorsalis umbonatus and pyrgo murrhina from core top samples collected from the atlantic indian and pacific oceans where modern bottom water temperatures are less than 4 c mg ca of all four species increase with increasing temperature and the mg ca temperature relationship does not appear to be necessarily exponential mg ca of c mundulus is consistently higher than c wuellerstorfi implying differences in the uptake of mg by different species within this genus the observed mg ca for c wuellerstorfi at temperatures less than 3 c is lower than those predicted from published mg ca temperature relationships derived for cibicidoides spp at higher temperatures previous studies have attributed this change in the mg ca temperature relationship of c wuellerstorfi to the effect of decreased carbonate ion saturation co32 on mg ca at low temperatures a relationship between the co32 and mg ca of 0 0083 0 002 mmol mol mol kg has been established for c wuellerstorfi from this study