integrated seismic and borehole geophysical study of the sudbury igneous complex reflection seismic and borehole geophysical data place important constraints on the subsurface geometry of the sudbury structure which is the site of the world s largest ni cu camp seismic reflections can be traced from outcrop within the sudbury north range to about 4 5 km depth beneath the center of the sudbury basin where the layer thickens abruptly from 1 to 3 km further south the north range norite can be followed to about 10 km depth beneath the south range borehole studies show systematic variations of p and s wave velocity poisson s ratio and density within the igneous complex quartz rich granophyre is distinguished from the norite and footwall rocks by relatively low poisson s ratios 0 20 0 23 versus 0 23 0 25 these changes in physical rock properties define an important subdivision of the igneous complex compatible with a simple model involving differentiation of melted crustal rock into dominantly felsic and mafic components this study documents the importance of interlayering to the seismic reflection response of the crystalline crust

identification of diagenetic artifacts in foraminiferal shells using carbon and oxygen isotopes abstract we have analyzed carbon and oxygen isotopes of two groups of planktonic foraminiferal shells from sediments near the pliocene pleistocene p p and the miocene pliocene m p boundaries in the lower gutingkeng formation in southwestern taiwan the p p shells display heavier isotopic compositions 18 o 1 5 13 c 1 5 over a narrow range suggesting a pristine environmental signature on the other hand the m p shells are much lighter 18 o 3 to 7 13 c 1 to 1 5 and more scattered associated with secondary carbonate diagenesis our detailed sem examination confirms this proposition the p p shells display a clean micro texture and are free from carbonate recrystallization however there are abundant secondary calcite crystals in the m p shells therefore the extreme shift of 18o and 13c in foraminiferal shells provides a guideline for evaluation of diagenetic artifacts of deeply buried sediments that have been uplifted on land

oxygen isotopic composition of multiple species of planktonic foraminifera recorders of the modern photic zone temperature gradient abundances of 12 species of planktonic foraminifera collected in two plankton tows from the east tropical atlantic are compared to the chlorophyll content and the temperature of the sea water from which they were collected as expected from previous work in the tropics all dominant tropical species occur in greatest abundance within the photic zone many species occur in greatest abundances in the seasonal thermocline in association with the maximum chlorophyll concentration while a few algal symbiont bearing species occur in greatest abundance in the mixed layer the 18o measurements of planktonic foraminifera shells from core top sediment samples confirm the vertical stratification within the photic zone that is suggested by the relationship between hydrography and abundances found in the plankton tows and found in the statistical study by ravelo et al 1990 comparison between the measured 18o values of planktonic foraminifera with the predicted 18o profiles of the overlying water column at three core locations indicate that species abundances in the sediment record the seasonally integrated conditions of the photic zone and suggests that the abundance of a species in the sediment depends on whether the preferred ecological conditions of that species may be found within the photic zone of the overlying water column sometime during the year species which calcify below the photic zone have only trace relative abundances finally it appears that the total range of 18o values of the dominant species approximates the predicted annual 18o of calcite range in the upper 80 m of the water column

invasion of anthropogenic co2 recorded in planktonic foraminifera from the northern gulf of aqaba the stable carbon isotopic composition of the planktonic foraminifera globigerinoides sacculifer and g ruber white and sedimentary organic matter from the northern gulf of aqaba have been investigated to estimate changes in 13cdic in surface waters during the last 1 000 years the high sedimentation rates at the core sites about 54 cm kyear provide high temporal resolution 10 years recent sediments at the top of the cores reflect conditions younger than 1950 the 13c records of the planktonic foraminifera from three multicores display similar trends showing a uniform and consistent pattern before the 1750s and a gradual decrease of approximately 0 63 over the last two centuries this decrease seems to track the decrease of 13cdic in surface waters which is mainly caused by the increase of anthropogenic input of 13c depleted co2 into the atmosphere similarly a trend towards lighter values of the carbon isotopic composition of sedimentary organic matter 13corg during the last 200 years supports the interpretation obtained from the planktonic foraminiferal 13c furthermore direct measurements of seawater show that 13c of the dissolved inorganic carbon dic in the northern gulf of aqaba has decreased by about 0 44 during the period 1979 2000 the average annual decrease is 0 021 which is similar to that observed globally the 13c values of planktonic foraminifera combined with organic matter 13c from marine sediments are good indicators for reconstructing past changes in atmospheric co2 concentrations from the northern gulf of aqaba

stable isotopes of carbon and sulphur as indicators of environmental change past and present stable isotopes of carbon 12 c and 13 c and sulphur 32 s and 34 s are fractionated during some of the transformations between reservoirs in the global carbon and sulphur cycles the main processes controlling the isotopic composition of earth surface reservoirs are for carbon photosynthesis respiration and equilibration between oceanic dissolved inorganic carbon and atmospheric co 2 and for sulphur bacterial sulphate reduction and sulphide reoxidation thus the different reservoirs of carbon and sulphur in the global cycles attain characteristic isotopic compositions that can be used as a fingerprint for different carbon and sulphur sources and to track changes in the balance of carbon and sulphur stored in different reservoirs these isotopic signals can be used both to examine contemporary anthropogenic impacts on the cycling of carbon and sulphur and where isotopic compositions are faithfully preserved in ancient sediments to examine historical changes in global geochemical cycles through geological time a number of case studies are discussed to illustrate how isotopic techniques represent one of the most powerful and important tools available in the study of both the causes and affects of ancient and modern global environmental change

glacial holocene biogenic sedimentation patterns in the south china sea productivity variations and surface water pco2 a bathymetric transect of cores in the south china sea extending from 4200 m to less than 1000 m water depth has been examined for glacial interglacial changes in carbonate and organic carbon sedimentation typical pacific carbonate cycles high carbonate content during glacials and low carbonate content during interglacials characterize cores from water depths deeper than 3500 m in contrast atlantic carbonate cycles low carbonate during glacials and high carbonate during interglacials are observed in cores from depths shallower than 3000 m as a result of increased dilution of carbonate by terrigenous material during glacial low stands of sea level glacial interglacial changes in the carbonate chemistry of south china sea intermediate and deep waters resulted in significant changes in the positions of the carbonate compensation depth ccd and the aragonite compensation depth acd during the last glacial the ccd and acd were at least 400 and 1200 m deeper respectively than at present organic carbon accumulation rates in the south china sea were approximately 2 times higher during the last glacial than the holocene carbon isotopic analyses and c n ratios of the organic matter indicate that only a small fraction of the increase in glacial organic carbon accumulation can be attributed to input of terrestrial carbon on the basis of this we conclude that surface water productivity in the south china sea was approximately 2 times higher during the last glacial maximum this is consistent with previous studies which have demonstrated that glacial productivity was higher in low to mid latitude regions of the atlantic and eastern pacific the deglacial decrease in organic carbon accumulation is accompanied by a decrease in 13corg using the relationship between 13corg and co2 aq developed by popp et al 1989 we estimate that surface water pco2 values in the south china sea during the last 25 000 years were very similar to atmospheric co2 concentrations

attenuation of broad band 50 1500 hz seismic waves in granitic rocks near the earth surface we report q estimates from borehole to tunnel seismic experiments at nagra s grimsel test site gts the probed granitic rocks are cut by brittle faults but do not show any signs of pervasive weathering q values estimated from p wave first arrivals by the spectral ratio and rise time methods range from about 20 to 60 with a median value of 35 and a standard error of 20 or less the surprisingly low q values inferred indicate that even outside the weathering zone seismic attenuation in some parts of the uppermost crystalline crust may be very high

attenuation of explosion generated pulse in rock masses recordings were made of seismic pulses by explosive sources in rock underground at mount isa mine queensland australia analysis of the experimental results in light of the theory of kjartansson 1979 indicates that the simple rise time law tau tau sub 0 ct q is inadequate for describing the attenuation of seismic pulses generated by a realistic source the rise time law makes no allowance for the spectral characteristics of the source except by assigning a value of tau sub 0 to each source and is an oversimplification of the process of source propagation through rocks consequently the constant c is source dependent an alternative method of estimating pulse attenuation is presented which overcomes the difficulties inherent in the rise time law

deep thermohaline circulation in the low latitude atlantic during the last glacial present day low latitude eastern and western atlantic basins are geochemically distinct below the sill depth of the mid atlantic ridge while antarctic bottom water aabw circulates freely in the western atlantic flow into the eastern atlantic is restricted below 4 km which results in filling the abyssal depths of this basin with water of geochemical similarity to nutrient depleted north atlantic deep water using carbon isotopes and cd ca ratios in benthic foraminifera we reconstruct the geochemistry of these basins during the last glacial maximum results indicate that deep eastern and western atlantic basins became geochemically identical during the last glacial this was achieved by shoaling of the upper surface of aabw above the sill depth of the mid atlantic ridge which allowed bottom waters in both basins to be filled with the same water mass although aabw became the dominant water mass in the deep eastern atlantic basin during the glacial holocene glacial 13c po4 shifts in this basin are in redfield proportions unlike the disproportionate holocene glacial 13c po4 shifts observed in the southern ocean by examining the composition of deep and intermediate waters throughout the atlantic we show that this effect was induced by a change in gradient of the 13c po4 deepwater mixing line during glacial times evidence from high latitude planktonic data suggests that the change in gradient of the deepwater mixing line was brought about through a significant reduction in the thermodynamic effect on southern ocean surface waters by using coupled 13c po4 data to constrain the composition of end member water masses in the glacial atlantic we conclude that deep waters in the low latitude glacial atlantic were composed of a mixture of northern and southern source waters in a ratio of 1 3

seasonal stable isotopic variations in living planktonic foraminifera from bermuda plankton tows abstract seasonal variations in surface water temperature and the 18o 16o ratios of calcite tests of living planktonic foraminifera collected in the upper 10 mare are coincident in the sargasso sea off bermuda the 18o of seasonally restricted globorotalia truncatulinoides and globigerinoides ruber pink and white may be used to determine the seasonal temperature contrast of the oceans in the past a preliminary model based on yearly absolute abundance and isotopic composition of these two species is able to approximate the composite 18o of fossil specimens of these species carbon and oxygen isotopic compositions of most species are size dependent with the largest differences occuring in 13c as a function of size the calcite tests of all living species were depleted in 13c relative to the 13c of total dissolved co2 at 0 and 50 m with no seasonal pattern in 13c being discernible in any species in almost all cases fossil specimens from box core sediments are significantly enriched in 13c and slightly enriched in 18o relative to their counterparts in the living fauna because the sediment populations are generally composed of larger sized specimens compares to the plankton of larger size specimens compared to the plankton

delineating fracture zones using surface tunnel surface seismic data p s and s p mode conversions a surface tunnel surface seismic experiment was conducted at the aspo hard rock laboratoryto study the seismic response of major fracture systems intersecting the tunnel a newly developedthree com

seasonal variability in the δ18o and δ13c of planktonic foraminifera from an upwelling environment sediment trap results from the san pedro basin southern california bight stable isotopic analyses 18o and 13crpar on four species of planktonic foraminifera collected from high resolution time series sediment trap sampling indicate that rapid and significant seasonal variability occurred in response to rapid changes in both the hydrographic environment and the isotopic composition of ambient seawater specimens were collected at a depth of 500 m for 28 consecutive 1 week periods in the san pedro basin within the southern california bight a region seasonally influenced by upwelling hydrographic monitoring of the study area revealed a 6 week period late april to mid june during which pulses of upwelling occurred causing significant increases in the oxygen isotopic composition of surrounding waters while decreasing the carbon isotopic composition analyses of globigerina bulloides orbulina universa neogloboquadrina dutertrei and neogloboquadrina pachyderma right coiling indicate that during the upwelling period these species live respectively at the surface in the surface mixed layer within the thermocline and below the thermocline globigerina bulloides ascends from well below the thermocline to the surface at the onset of upwelling and increases production to its maximum simultaneously as its morphology changes to less calcified open forms both n dutertrei and n pachyderma follow isothermal ranges migrating to shallower waters during upwelling and subsequently descending after upwelling ceases neogloboquadrina dutertrei appears to inhabit the region associated with both the thermocline base and chlorophyll maximum when it is most abundant following upwelling orbulina universa increases its depth habitat as solar irradiance increases but this species decreases in abundance during upwelling the 18o signal of o universa appears to be a useful indicator of seasonal temperature variations above the thermocline whereas the 18o of g bulloides documents near surface temperatures during upwelling the 13c signal of both n dutertrei and n pachyderma appears to record the 13c of equilibrium calcite for the regions of the thermocline and just below the thermocline respectively due to the relative preservation potentials of the four species analyzed only n dutertrei and n pachyderma are likely to be preserved in the sedimentary record in regions of oxygenated bottom waters thus an actual record of hydrographic conditions during upwelling as would be found in tests of g bulloides is not preserved instead conditions before n pachyderma and just after n dutertrei are more likely recorded

core top calibration of δ18o and δ13c of g ruber white and u mediterranea along the southern adriatic coast of italy we carried out an extensive survey of the oxygen and carbon isotope composition of the planktic species g ruber white and of the benthic species u mediterranea along the southern italian coast of the adriatic sea and in the gulf of taranto comparison with seasonal satellite based sea surface temperature maps and water column profiles as well as with several sets of water samples allows estimation of the effect of salinity and different nutrient supply on the 18o and 13c of foraminifera the results indicate that g ruber white while being highly affected by different salinity and nutrient distributions related to circulation patterns of major water masses dominantly record summer temperature conditions u mediterranea reflect the recent environmental conditions such as nutrient supply and bottom water temperature characteristics along the southern italian coast and clearly show the transition from a near coastal eutrophic system to an offshore oligotrophic system

imaging of fracture zones in the finnsjon area central sweden using the seismic reflection method in 1987 the swedish nuclear fuel and waste management co skb funded the shooting of a 1 7 km long high resolution seismic profile over the finnsjon study site using a 60 channel acquisition system with a shotpoint and geophone spacing of 10 m the site is located about 140 km north of stockholm and the host rocks are mainly granodioritic the main objective of the profile was to image a known fracture zone with high hydraulic conductivity dipping gently to the west at depths of 100 to 400 m the initial processing of the data failed to image this fracture zone however a steeply dipping reflector was imaged indicating the field data were of adequate quality and that the problem lay in the processing these data have now been reprocessed and a clear image of the gently dipping zone has been obtained in addition several other reflectors were imaged in the reprocessed section both gently and steeply dipping ones correlations with borehole data indicate that the origin of these reflections are also fracture zones the improvement over the previous processing is caused mainly by 1 refraction statics 2 choice of frequency band 3 f k filtering and 4 velocity analyses in addition to reprocessing the data some further analyses were done including simulation of acquisition using only the near offset channels channels 1 30 and the far offset channels channels 31 60 and determining the damping factor q in the upper few hundred meters based upon the amplitude decay of the first arrivals the data acquisition simulation shows the far offset contribution to be significant even for shallow reflectors in this area contrary to what may be expected a q value of 10 determined from observed amplitude decay rates agrees well with theoretical ones assuming plane wave propagation in an attenuating medium

southern ocean contributions to glacial interglacial changes of atmospheric pco2 an assessment of carbon isotope records in diatoms eleven new antarctic records of diatom bound 13corg show significantly lighter values during the last glacial maximum than during the holocene with a general trend of increasing depletions southward of the modern antarctic polar front mapf in contrast glacial diatoms from cores farther north of the mapf show 13corg values which are 1 heavier than during the holocene likely causes for the low glacial 13corg in antarctic diatoms are higher co2 aq lower growth rates and changes in diatom abundance or size taken at face value the glacial depletions of 13corg suggest that antarctic surface waters south of the mapf might have been a source of atmospheric pco2 during the glacial period alternatively the glacial depletions might have been caused by either a relatively small decrease in growth rates or changes in the abundance of the two dominant diatom species or their average cell size interpretations of the subantarctic records are complicated by similar uncertainties

seasonal changes in the isotopic composition of planktonic foraminifera collected in panama basin sediment traps abstract isotopic analyses have been made on five species of planktonic foraminifera collected in two deployments of parflux mark ii time series sediment traps in the panama basin the automated sampling system on the traps provided 4 one month samples from 29 july to 16 november 1979 and 6 two month samples from december 1979 to november 1980 the 18o values of globigerinoides ruber and globigerinoides sacculifer in this region are primarily affected by a low salinity surface layer that forms during the early winter these species each show a 1 total range in 18o the 18o values of the colder water species globorotalia menardii neogloboquadrina dutertrei and globorotalia theyeri show smaller seasonal changes in 18o the 13c values of g ruber and g sacculifer exhibit small seasonal changes 0 35 and 0 4 respectively despite large seasonal changes in surface water productivity the colder water species exhibit only slightly larger changes in 13c up to 0 55 throughout the year all colder water species exhibit minimum or near minimum 13c values during february and march which is the period of maximum upwelling and primary productivity seasonal variations in the flux of foraminifera in the water column at this location will have only a small effect on the isotopic composition of the sediment assemblage extreme values of 18o and 13c do not occur during the periods which are associated with the high flux of foraminiferal tests

surficial deep sea sediments across the polar frontal system southern ocean indian sector particulate carbon content and microphyte signatures abstract two main subjects are addressed in this study concerning a complex sub antarctic hydrological system during the antares i md75 cruise southern ocean indian sector 1 the 13 c org signature in waters fluffs and sediments and their relationships with anthropogenic effects and 2 the degree of preservation of the deep sea phytodetritus a north to south gradient was observed for the deep sea microphytes signatures with the higher concentrations in the higher latitude chaetoceros spores dominant species chaetoceros cf neglectus were abundant in the fluffy layers from the permanent open ocean zone pooz and associated with the highest chl a concentration the diatom spores were absent in the northern part of that transect the coccolith repartition and preservation also showed a latitudinal gradient the presence of coccoliths more or less intact below the lysocline may result from different sedimentation rates along this gradient undisturbed and thick fluffs in the pooz and southern polar frontal zone stations were enriched with coccoliths and chaetoceros resting spores even at 4700 m and the revival experiments demonstrated their recent origin via a possible in mass or in pulse sedimentation a latitudinal gradient clearly appeared for 13 c org poc and chloropigments with a relationship between 13 c org and chl a direct positive for the phytoplankton and indirect negative for the fluffs and sediments these observed gradients are in part attributed to the latitudinal effects and to the physical characteristic of the water bodies differences between plankton and sediment 13 c org signatures are attributed to an anthropogenic influence however diagenetic processes leading to slight 13 c org enrichment in sediments cannot be absolutely rejected at this stage a stronger deep northward advection to the north of the polar front may also in part explain these north to south bio geochemical deep sea gradients

reconstructing estuarine conditions oyster shells as recorders of environmental change southwest florida abstract live collected shells of the oyster crassostrea virginica contain geochemical records of modern temperature and salinity so records of prehistoric conditions may be obtained from subfossil shells restoration of channelized watersheds in florida is receiving much attention and plans for targeted watersheds require information about estuarine conditions before channelization lack of historical records necessitates alternative methods to understand pre disturbance conditions a 14c calibrated amino acid geochronology based on racemization of glutamic acid yielded ages ranging from 190 1220 ad and from 1270 1860 ad for subfossil oysters from blackwater river near natural watershed and for faka union bay channelized watershed respectively 18o and 13c values of subfossil shells from blackwater river indicate salinity and summer temperatures similar to present winter temperatures recorded in shells from 190 590 720 and 1050 ad appear 1 5 c colder than present winter temperatures whereas the shell from 1220 ad records winter temperatures similar to modern winter temperatures these temperature shifts may indicate change in climate or natural seasonal variation of winter temperature from year to year subfossils from faka union bay may reflect a complicated hydrology which cannot be evaluated by isotopic compositions alone and demonstrates the need for development of independent elemental proxies for temperature and salinity decreases in 13c from subfossil to modern shells may in part result from co2 added to the atmosphere from fossil fuel burning the suess effect subfossil 13c that is 1 more positive than modern shells suggest a change in the dominant carbon sources from terrestrial c4 or aquatic plants to c3 plants mangroves

high resolution images of the lower crust deep seismic reflections from 15 to 180 hz abstract we report the results of an unconventional broad band deep seismic reflection survey undertaken on land in southwest england previous marine seismic lines in this area have shown strong layered lower crustal reflectivity the broad band survey shows near normal incidence p wave reflections from the lower continental crust and from the moho with frequencies that range from 15 to 180 hz high frequency lower crustal s wave reflections were also observed these high frequencies were obtained by placing both sources and receivers in boreholes up to 2 km deep drilled within a large homogeneous granite pluton recording down hole avoids loss of high frequency energy during transmission through heterogeneous and highly attenuative near surface layers the high frequencies were generated using explosive sources and were recorded on sub surface accelerometers and hydrophones and on a conventional array of surface geophones seismic attenuation within the granite is low the quality factor q lies above 2000 these new high frequency observations show that the lower crust does not preferentially reflect particular frequencies the data are most readily explained as resulting from the combination of a frequency independent q in the upper crust with a white reflectivity response in the lower crust the data are not consistent with crustal models which are highly tuned to reflect preferentially the frequencies employed in conventional deep seismic reflection surveys the data require relatively sharp boundaries within the lower crust significant variation in physical properties must occur over vertical distances of not more than about 10 m sharp boundaries are most easily explained if the reflections result from lithological contrasts

carbon isotope composition of tropical surface water during the past 22 000 years carbon isotope values of many species of planktonic foraminifera are size dependant values of 13c of individual size fractions are therefore an integration of low 13c values of calcite precipitated in the juvenile growth stage and high values precipitated in later stages in general the selection of a particular size fraction for downcore studies has been subjective analysis of different size fractions of planktonic foraminifera however yields different time series in downcore studies by measuring the 13c of many size fractions the 13c precipitated throughout the growth of the foraminifera can be calculated time series of the 13c of calcite precipitated in the late growth stages of planktonic foraminifera from two nearby cores from the caribbean sea result in a better correlation than time series of constant size fractions these 13c records indicate similar 13c values during the last glaciation and the late holocene and a broad deglacial minimum approximately synchronous with a minimum in the 13c records of benthic foraminifera from intermediate depth atlantic cores the deglacial minimum may be a reflection of the isotopic composition of the underlying intermediate water which may be affected by circulation changes or changes in preformed 13c values and or of the flux of water upwelled into the surface layer the small 0 2 to 0 0 glacial interglacial 13c difference in tropical surface water is also believed to be affected by the chemistry of the underlying source water

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

the imprint of anthropogenic co2 in the arctic ocean evidence from planktic δ13c data from watercolumn and sediment surfaces 13c values of n pachyderma sin from the water column and from core top sediments are compared in order to determine the 13c decrease caused by the addition of anthropogenic co2 to the atmosphere this effect which is referred to as the surface ocean suess effect is estimated to be about 0 9 0 2 within the arctic ocean halocline waters and to about 0 6 0 1 in the atlantic derived waters of the southern nansen basin this means that the area where the arctic ocean halocline waters are formed the arctic shelf regions are relatively well ventilated with respect to co2 nevertheless 13c of dissolved inorganic carbon 13cdic in the arctic ocean halocline waters is far from isotopic equilibrium absolute values of 13c of n pachyderma sin covary with the surface ocean suess effect and we interprete changes in both parameters as a reflection of the degree of ventilation of the waters on the shelf sea measurements of 13c of n pachyderma sin in the arctic ocean from plankton tows reveal a vital effect of about 2 significantly different from other published values a first order estimate of the total anthropogenic carbon inventory shows that despite of its permanent sea ice cover the arctic ocean with 2 of the global ocean area is responsible for about 4 6 of the global ocean s co2 uptake

effective q determination using frequency methods on birps data abstract an investigation to determine q for compressional waves from marine reflection seismic records is presented the spectral ratio method is used to determine values for the lower crust results from spectral modelling from a known synthetic source wavelet are used to give minimum estimates for the whole crust the effective q for the reflective lower crust around britain is found to be 500 200 which is consistent with laboratory results for dry rocks and is probably too large to allow significant amounts of fluid to be present

a critical review of marine sedimentaryδ13corg pco2 estimates new palaeorecords from the south china sea and a revisit of other low latitude δ13corg pco2 records in an attempt to understand better the local biogeochemistry of the south china sea scs and to unravel the contribution of this marginal low latitude basin to changes in atmospheric co2 concentrations we analyzed the carbon isotopic composition of organic matter 13corg in four sediment cores from throughout the scs covering the last 220 kyr higher values around 19 5 to 20 5 mark glacial stages while lower values around 21 to 22 5 are characteristic of interglacials following well established procedures the 13corg records are converted to local pco2 estimates on the basis of these and other low latitude 13corg pco2 estimates from the literature we present a critical evaluation of the use of 13c of bulk sedimentary organic matter to hindcast past changes in local co2 aq three crucial pitfalls are identified 1 given the present inability to quantify precisely the time varying amount of terrigenous corg input to marine sediments absolute values of pco2 estimates based on bulk sedimentary corg are questionable 2 none of the low latitude sedimentary 13corg pco2 records shows the expected correlation between temporal changes in upwelling intensity and co2 estimates most likely due to the antagonistic influences of co2 aq and phytoplankton growth rate on 13corg 3 a detailed comparison of marine 13corg pco2 records with the vostok co2 record reveals significant differences in phasing specifically at the end of the last deglaciation and during the oxygen isotope stage 5 4 transition however in areas where equilibrium between oceanic and atmospheric co2 occurs for example the scs and the mediterranean the timing of changes in 13corg should agree with the co2 record from ice cores if 13corg is a reliable proxy for changes in co2 aq taken together the compilation of records presented here cautions the use of 13corg as an unambiguous tracer of dissolved molecular co2 in the surface ocean and calls for a re evaluation of the role of the low latitude ocean on temporal changes in atmospheric co2

carbon isotope composition of caribbean sea surface waters response to the uptake of anthropogenic co2 1 the burning of fossil fuels and deforestation have significantly increased atmospheric co2 levels from 280 ppm prior to the industrial revolution to the present value of 390 ppm suess 1955 was the first to show that the carbon isotopic composition of the atmosphere is changing in response to the anthropogenic input of radiocarbon dead 13c depleted co2 from fossil fuel combustion here we report a high resolution planktonic foraminiferal 13c record from the caribbean sea for the last 300 years that clearly resolves the timing and magnitude of the marine 13c suess effect associated with the oceanic uptake of anthropogenically derived co2 cariaco basin sediment trap and upper most box core sediment 13c match both the trend and magnitude of observed 13c changes in atmospheric co2 over the last 15 years the longer sediment record suggests the marine suess effect to be 0 75 from pre industrial values with most of the change occurring since 1950 coincident with the rapid rise in atmospheric co2 noted in ice core and instrumental data if the current anthropogenic co2 emission trend continues extrapolating our marine 13c rate curve into the future suggests that the rate of marine 13c change caused by anthropogenic co2 will increase to 0 10 yr 1 by the end of this century an increase of more than an order of magnitude from 1950 values

appraisal of waveform repeatability for crosshole and hole to tunnel seismic monitoring of radioactive waste repositories countries worldwide are seeking solutions for the permanent removal of high level radioactive waste from the environment surrounding the waste with multiple engineered barriers and emplacement in deep geological repositories is widely accepted as a safe means of isolating it from the biosphere for the necessary 105 106 years as a precautionary measure society demands that repositories be monitored for 100 300 years after they are backfilled and sealed effective monitoring that does not compromise the engineered and natural barriers is challenging to address this issue we investigate the viability of crosshole and hole to tunnel seismic methods for remotely monitoring high level radioactive waste repositories measurements are made at two underground rock laboratories in switzerland one within granitic rock and one within clay rich sediments numerical simulations demonstrate that temporal changes of the monitored features i e bentonite plug excavation damage zone sand filled microtunnel sh

experimental comparison between spectral ratio and rise time techniques for attenuation measurement two techniques for the measurement of attenuation spectral ratio and rise time techniques were tested and compared in the laboratory the spectral ratio technique proved to be reliable and easy to implement for intermediate values 5 50 and high attenuations the spectral ratio technique is inaccurate calculating the rise time on simulated signals we found a relation between rise time and the ratio travel time to quality factor t q which could be approximated in intervals by the linear relation c t q the constants and c depend on the absolute value of t q and on the initial source signal the rise time technique performed on the first quarter period of the signal enables high attenuations q 5 to be measured the determination of the relation between and t q is possible if one knows the initial source we theoretically approximate this relation through a simulation using a realistic propagation model with laboratory measurements made on fontainebleau sandstone we show that the rise time technique using the theoretical relation t q gives comparable values of q to those obtained from the spectral ratio technique in borehole seismics where it is often difficult to remove undesired signals the rise time technique applied with the right t q relation is the best method to use

faunal and alkenone reconstructions of subtropical north atlantic surface hydrography and paleotemperature over the last 28 kyr two techniques for estimating past variations in sea surface temperature sst have been used to investigate climatic change in biogeochemical oceanic flux study bofs core 31k 19 n 20 w from the eastern subtropical atlantic high resolution sst records for the last 28 kyr have been produced using planktonic foraminiferal assemblages based on the imbrie kipp transfer function technique and the uk 37 index derived from abundances of c37 alkenones biosynthesized by prymnesiophyte algae modern observations suggest that these indices reflect particular hydrographic conditions in the upper ocean the uk 37 index corresponds to the temperature at the time of maximum coccolith productivity typically late spring early summer in the study area today whereas the faunal transfer function is calibrated for seasonal maximum and minimum temperatures in general the faunal and biomarker paleotemperature records display comparable sst variations during the last glacial and deglacial but although the overall trends are similar differences exist in the magnitude and timing of these temperature changes most notably the faunal twarm and uk 37 sst estimates diverge by 3 c between 8 ka and 6 ka and this offset persists through the late holocene this difference cannot be adequately explained by uncertainties associated with either the calibration data sets or fluctuating preservation levels we therefore propose that the deviation in sst estimates is linked to a switch in the seasonal timing of maximum coccolith production from the summer in the glacial ocean to the late spring early summer in the modern ocean our results suggest that a dual approach to sst estimation based on faunal and biomarker proxies can provide a valuable means of evaluating mixed layer and productivity changes associated with the movement of oceanographic frontal zones during the late quaternary

opening the carbon isotope vital effect black box 2 quantitative model for interpreting foraminiferal carbon isotope data interpretation of carbon isotope records from late quaternary planktonic foraminifers are confounded due to the presence of a significant physiological component in the carbon isotopic signal a quantitative carbon isotope qc model is presented which relates the carbon isotopic composition of a foraminiferal shell to the physiological processes of respiration and symbiont photosynthesis and to the 13c value of seawater co2 the qc model is calibrated with physiological and stable isotopic data from laboratory experiments with living planktonic foraminifers model simulations of chamber and shell 13c values with the symbiont bearing foraminifers orbulina universa and globigerinoides sacculifer suggest 1 variations in symbiont density and photosynthetic rate light level or habitat depth are the primary physiological parameters controlling intraspecific carbon isotopic variability in these species 2 respiration has little effect on the 13c of o universa and 3 each chamber in a multichambered foraminiferal test will have a distinct 13c value depending on its position in the test whorl size 13c value relationships reported for g sacculifer from fossil assemblages can be explained as a function of increasing symbiont density during ontogenetic development

carbon isotopes in recent planktonic foraminifera a record of anthropogenic co2 invasion of the surface ocean abstract the release of isotopically light anthropogenic co 2 into the ocean atmosphere carbon reservoir has resulted in a decrease in the carbon isotopic composition of the surface ocean in this paper we examine differences between the carbon isotope composition of planktonic foraminifera from sediment traps with older late holocene material to estimate the change in 13 c 13 c in eastern atlantic surface waters as a result of the invasion of anthropogenic co 2 using stable oxygen isotopes we demonstrate that average trap values for a variety of species are more or less identical to core top values suggesting that foraminifera recovered in sediment traps are representitive of foraminifera deposited in the sediments however carbon isotopes recorded in planktonic foraminifera from recent trap material reveal a decrease in the 13 c composition of all species relative to the core top samples although the magnitude of the decrease varies significantly between species surface dwelling foraminifera g ruber g bulloides show 13 c values of 0 53 to 0 62 which is similar to other estimates from shallow water coral and sponge records for the decrease in the 13 c composition of dissolved organic carbon in surface waters which has taken place since the start of the anthropogenic emissions the magnitude of decrease in the 13 c of surface waters suggested by these records is also close to that predicted by global carbon cycle models deeper thermocline dwelling foraminifera such as g inflata however show 13 c values 0 2 which are substantially lower than their surface dwelling counterparts this reduction in 13 c with increasing depth habitat within the mixed layer may be related to limited vertical penetration of anthropogenic co 2 as a result of the strong upwelling which is observed in the eastern atlantic along the northwest african margin

environmental change in the great plains an isotopic record from fossil horses abstract carbon and oxygen isotope ratios of fossil horse tooth enamel from nebraska and texas show evidence for late neogene environmental changes in the great plains the earliest unambiguous c4 dietary signal among texas equids coincides with the age of the classic late hemphillian age coffee ranch fauna which we suggest is 6 6 ma based on volcanic ash correlations c4 vegetation was present in the diets of a small fraction of late hemphillian equids in nebraska and was thereafter ordinary in the diets of both nebraska and texas equids there is no unequivocal evidence for abundant c4 vegetation in the diets of pre late hemphillian equids and we suggest that the ensuing dietary change reflects c4 biomass expansion in the latest miocene carbon isotope ratios of post hemphillian horses in nebraska can be divided into two statistically distinct populations on the basis of whether tortoise remains co occur with horse remains indicating that the two proxies carbon isotopes and presence absence of tort

vostok ice core provides 160 000 year record of atmospheric co2 direct evidence of past atmospheric co2 changes has been extended to the past 160 000 years from the vostok ice core these changes are most notably an inherent phenomenon of change between glacial and interglacial periods besides this major 100 000 year cycle the co2 record seems to exhibit a cyclic change with a period of some 21 000 years

carbon isotope records from extant caribbean and south pacific sponges evolution of δ13c in surface water dic stable isotope records of demosponges from the caribbean and coral sea are described for the purpose of studying the influence of fossil fuel co2 on the carbon isotopic composition of dissolved inorganic carbon dic in surface water the slow growing sponges precipitate calcium carbonate in isotopic equilibrium with ambient sea water and are used to detect changes in 13cdic from pre industrial times early 19th century to the present we observed similar shapes and ranges in 13c curves measured on caribbean specimens collected from water depths of 25 84 and 91 m as well as a specimen collected in shallow waters off new caledonia the records reveal a highly significant correlation with atmospheric 13cco2 13cdic values for caribbean and coral sea surface waters were calculated using the 13c sponge records while 13c of atmospheric co2 decreased by about 1 4 from the early 19th century to 1990 13cdic of caribbean and coral sea surface waters decreased by 0 9 0 2 and 0 7 0 3 respectively no isotopic equilibrium between surface water dic and atmospheric co2 was observed either during the pre industrial steady state or during the last 100 years the lower amount of depletion in the surface water 13cdic with respect to the atmospheric anthropogenic signal is explained by the dilution of the surface waters by biologically altered subsurface water dic the lower 13c decrease in the coral sea points to a stronger influence of the subsurface water source compared to the caribbean

carbon isotopic disequilibrium between seawater and air in the coastal northern south china sea over the past century six coastal sediment cores collected from the northern south china sea were dated by 210 pb and analyzed for stable carbon and oxygen isotope composition of planktonic foraminifer globigerinoides ruber d 13 cgr and d 18 ogr three of these cores were located east of hainan island and the other three off the pearl river estuary pre surface seawater d 18 o and dissolved inorganic carbon dic d 13 c were identified as the dominant factors controlling downcore variations of d 18 ogr and d 13 cgr respectively results of d 13 cgr were then used to study surface water d 13 cdic and its relation to d 13 c of atmospheric co2 d 13 catm over the past century downcore records showed rather constant d 13 cgr in cores off hainan island but moderate decreases of d 13 cgr at rates between 0 006 and 0 009 per year in cores off the pre isotopic disequilibrium between d 13 cdic and d 13 catm was observed with d 13 cdic apparently higher than expected at equilibrium with d 13 catm except at the site closest to the pre the relatively steady d 13 cgr values east of hainan island were explained by balanced vertical mixing and biological pump whereas the moderate d 13 cgr decreases with time off the pre were attributable to fluvial input of

seismic scattering in the upper crystalline crust based on evidence from sonic logs summary evidence from sonic logs indicates that velocity fluctuations in the upper crystalline crust are remarkably uniform this motivates a generic approach to classifying uppercrustal seismic heterogeneity and to studying implications for seismic wave propagation the resulting canonical model of upper crustal seismic structure is characterized by a spatially isotropic von karman autocovariance function with a z 100 m 0 15 and cj 300 m s small angle scattering theory is used to predict the transition from weak to strong scattering as well as phase fluctuations and scattering attenuation compared with exponential random media v 0 50 the high fractal dimension i e small values of v of upper crustal heterogeneity causes smaller phase fluctuations and transition from weak to strong scattering at lower frequencies and shorter path lengths acoustic finite difference modelling shows that seismic reflections from deterministic features surrounded by heterogeneities are severely degraded when they fall into the strong scattering regime conversely traveltime fluctuations of transmitted waves are found to be relatively insensitive to the transition from weak to strong scattering upper crustal scattering q is predicted to lie between 600 and 1500 which is one to two orders of magnitude higher than q values inferred from seismic data this suggests that seismic attenuation in the upper crystalline crust is dominated by anelastic effects rather than by scattering

does sedimentary organic δ13c record variations in quaternary ocean co2 aq ocean surface water co2 aq variations based on glacial interglacial changes in sediment delta 13corg are shown to compare favorably with reconstructions based on ice core co2 in particular an approximate 80 microatmospheres increase in atmospheric pco2 during the last glacial interglacial transition is calculated to correspond to a 3 4 micromolar increase in ocean surface water co2 aq at atmospheric equilibrium a widespread marine delta 13corg decrease of 1 2 accompanied this event and was not preceded by an equivalent isotopic change in surface water total dissolved inorganic carbon these observations support the hypothesis that co2 aq influences photosynthetic isotope fractionation between marine inorganic and organic carbon pools and therefore that plankton sediment delta 13corg may serve as a proxy for surface water co2 aq

variability of the δ13c of dissolved inorganic carbon at a site in the north pacific ocean abstract we present a depth profile of 13 c dic dissolved inorganic carbon and a time series of surface water 13 c dic from seawater samples collected at a single site during the eve cruise in the north pacific in june of 1987 our deep water results confirm those reported by kroopnick 1985 for geosecs station 213 10 west of eve site we observed a small but significant decrease in the 13 c of dic in the upper 500 m of the water column over 13 years since the geosecs survey this is likely due at least in part to the input of additional fossil fuel derived co 2 to the upper ocean we observed a significant change in surface water 13 c over a short time period 2 days that was the result of a change in the shallow surface water mass this change emphasizes the need for caution when conducting seasonal studies

q factor by spectral ratio technique for strata evaluations abstract the laboratory estimated quality factor q a function of acoustic wave speed v amplitude a and frequency f were chosen for in situ strata evaluation of rocks of the right bank canal of upper wardha maharashtra india using the spectral ratio technique eleven core samples of compact amygdaloidal and vesicular basalts were characterized by their q values the q factor determined using the spectral ratio technique with centre frequency of 500 khz is found to result in differing values for compact amygdaloidal and vesicular basalts over ranges 10 14 4 6 and 2 4 respectively the specimens belonging to amygdaloidal and vesicular basalts with secondary minerals and calcareous intrusions in the vesicles have a very low q value and a very low yield of rock mass that is not proportionate to the energy generally used in blasting operations a correlation of q 0 26rqd 3 68 between the laboratory measured q value and in situ rock quality designation rqd data obtained from the recovery of the exploratory borehole core samples provides a useful means of understanding geological strata in rock mass recovery evaluation the lower q values implied higher energy requirements for effective excavation of the rock masses

surface and deep water variability at the blake ridge nw atlantic during the plio pleistocene is linked to the closing of the central american seaway abstract the closing of the central american seaway cas during the late pliocene played an important role in global climate change as well as variation in surface and deep ocean paleoceanography restriction in the mixing of pacific ocean water with atlantic ocean water through the cas ultimately led to the enhanced production of high salinity warm gulf stream water which flowed poleward and caused the northern hemisphere glaciation nhg as well as increased production of deep northern component water ncw the timing of the final closure of the cas is still a topic of debate the present study pursued on planktic foraminifera and carbon isotopic variation in planktic foraminifera from the blake ridge to understand the variation in surface and deep ocean paleoceanography and their linkages to the timing of the closing of the cas planktic faunal turnover at around 2 2 ma along with the increased production of ncw at around 2 4 ma is considered as the ceasing period of the cas prior to 2 2 ma the dominance of globigerina bulloides orbulina universa and globigerinoides ruber indicates the existence of the opening between the two americas and invasion of pacific surface water into the atlantic through this gateway it is proposed that during this time the studied odp hole 994c was under the influence of highly productive gyre water as observed by the dominance of g bulloides and depleted 13c of neogloboquadrina dutertrei 13cnd the dominance of n dutertrei and globorotalia truncatulinoides with enriched 13cnd from 2 2 to 1 2 ma indicates the presence of high salinity less productive surface water over the studied hole 994c the closing of the cas restricted the mixing of two ocean waters and thus the intensity of the gulf stream increased significantly with the dominance of ncw at the deeper level increased cooling and intensified gulf stream shifted the gyre water eastward and deepened the thermocline and thus the studied hole was under gyre margin gulf stream water during 2 2 1 2 ma the mid pleistocene transition 1 2 to 0 8 ma is marked by the presence of high productive gyre water depleted 13cnd over hole 994c the dominance of all the species with highly variable 13cnd and 18ond during the last 0 4 ma indicates that fluctuations in surface water perhaps are linked to increased nhg

the accuracy of estimating q from seismic data a major aim of seismic interpretation is the inference of petrophysical properties of reservoir rocks because the inversion from seismic to petrophysical characteristics is far from unique this task requires a range of seismic parameters prominent among which are seismic velocity impedance and poisson s ratio the inclusion of seismic absorption in this list could add desirable complementary information for example absorption may be more sensitive to clay content than seismic velocity klimento and mccann 1990 however seismic absorption is difficult to measure particularly over depth intervals as short as most reservoir intervals

planktonic foraminiferal δ13c records from southern ocean sediment traps new estimates of the oceanic suess effect the carbon isotopic composition is measured for three species of planktonic foraminifera globigerina bulloides globorotalia inflata and neogloboquadrina pachyderma s from southern ocean sediment traps the sediment traps represent the annual flux of foraminifera in subtropical to polar frontal environments from the western pacific southern australia sector comparison between the seasonal 13c composition of the foraminifera and estimated 13c of dissolved inorganic carbon dic allows disequilibrium effects to be determined disequilibrium exhibits a latitudinal trend with greatest offsets from equilibrium at lower latitudes this effect causes a north to south increase in foraminiferal 13c while the 13cdic displays a decrease across these latitudes disequilibrium in g bulloides can be accounted for by changes in temperature the relationship between disequilibrium and temperature which we derive in this field study is consistent with the laboratory relationship of bemis et al 2000 corrected 13c for g bulloides is closely correlated to seasonal changes in nutrients at each site indicating the utility of g bulloides 13c as a nutrient tracer in southern ocean environments comparison between flux weighted sediment trap values and nearby core tops indicates a modern depletion in 13c which we attribute to the oceanic suess effect the imprint of this effect on the foraminiferal isotopes provides further evidence for the equilibration between surface waters and the atmosphere in the subantarctic zone

orbital and suborbital variability in the equatorial indian ocean as recorded in sediments of the maldives ridge odp hole 716a during the past 444 ka this study is aimed at understanding past 444 ka record of climate variability in the equatorial indian ocean using high resolution records of planktic and benthic foraminifera and pteropods from ocean drilling program hole 716a maldives ridge southeastern arabian sea in total 892 samples of 10 cm 3 volume from 444 ka old sequence were analysed at 1 cm intervals to generate census data of the foraminiferal fauna and pteropods the percent and detrended time series of mixed layer species globigerinoides ruber and globigerinoides sacculifer and thermocline species neogloboquadrina dutertrei benthic foraminifera cymbaloporetta squammosa sphaeroidina bulloides and uvigerina proboscidea and pteropods from odp hole 716a reveal significant changes in wind intensity during the past 444 ka an abrupt decrease in the cymbaloporetta squammosa population at c 300 ka across mis 8 9 suggests a weakening of equatorial wind intensity which could be linked to indian monsoon and may have driven pronounced changes in the oxygen minimum zone in the maldivian region these changes were contemporaneous with the mid brunhes climatic event the beginning of aridity in the indonesian australian region and the onset of a humid phase in equatorial east africa as observed in several oceanic and continental records this strengthens a connection between equatorial indian ocean wind intensity the indian monsoon and indonesian australian african climates