oxygen and carbon isotope record of east pacific core v19 30 implications for the formation of deep water in the late pleistocene north atlantic abstract a detailed oxygen and carbon isotope record has been obtained from benthic foraminifera in core v19 30 from the carnegie ridge on the south side of the panama basin expressing these records and the oxygen and carbon isotope records previously published for atlantic core m 12392 on a common timescale it is apparent that the oxygen isotope records are very similar but that the carbon isotope records are quite different by obtaining the carbon isotope gradient between the two sites as a function of time we show that the production of north atlantic deep water has varied over a wide range during the late pleistocene and that the pattern of variation is not simply related to the well known oxygen isotope record although the two oxygen isotope records are very similar changes in the interoceanic gradient are detectable and support the hypothesis that in the glacial mode the north atlantic was colder and less oxygenated than it is today shackleton s 1 1977 interpretation whereby the carbon isotope record from the atlantic core reflects changes in the terrestrial biomass is an over simplification however the record from the pacific core v19 30 probably can be explained in these terms since it probably approximates the carbon isotope record of global mean oceanic dissolved co 2

antarctic marine temperatures late campanian through early paleocene an oxygen isotope paleotemperature study of benthic foraminifera from the upper campanian through lower paleocene section at seymour island near the coast of antarctica was done in conjunction with careful scanning electron microscope observations to monitor the state of foraminiferal preservation the isotopic compositions of those samples which were deemed to be well preserved were the basis of the conclusion that campanian through paleocene high latitude shelf waters near antarctica had temperatures between approximately 4 5 and 10 5 c temperatures during early and middle maastrichtian time were slightly higher than those of either the late campanian or late maastrichtian the inference of temperate climatic conditions in antarctica is in agreement with paleoclimatic conclusions drawn on the species composition of the planktonic foraminiferal assemblages and the character of the planktonic foraminifera as well as with published conclusions based upon paleobotanical evidence the maastrichtian and campanian water temperatures at seymour island are similar to those inferred from published isotope ratios of pacific late cretaceous benthic foraminifera from low latitudes indicating that campanian through early paleocene deep ocean waters at least in the pacific and perhaps elsewhere as well could have formed by sinking of surface waters in polar regions

monitoring velocity variations in the crust using earthquake doublets an application to the calaveras fault california we present a technique that greatly improves the precision in measuring temporal variations of crustal velocities using an earthquake doublet or pair of microearthquakes that have nearly identical waveforms and the same hypocenter and magnitude but occur on different dates we compute differences in arrival times between seismograms recorded at the same station in the freqency domain by cross correlation of short windows of signal a moving window analysis of the entire seismograms including the coda gives t the difference in arrival times versus running time along the seismogram the time resolution of the method is an order of magnitude better than the digitization interval the t technique is illustrated with a pair of microearthquakes m 1 7 and 2 0 that occurred before and after the coyote lake california earthquake m 5 9 of august 6 1979 and on the same segment of the calaveras fault that ruptured during the earthquake the coda wave arrivals for some stations are progressively delayed for the second earthquake in the doublet so that its seismogram appears as a stretched version of the earlier event we interpret this systematic variation in t along the coda as a change in the average s velocity in the upper crust in the time interval between the two doublets s wave velocities appear to have decreased by 0 2 in an oblong region 5 10 km in radius at the south end of the aftershock zone

paleoceanography of the cretaceous tertiary boundary event inferences from stable isotopic and other data we report the results of new stable oxygen and carbon isotope analyses on carbonate fine fraction whole rock and benthic foraminifers caco3 and coarse fraction percentage determinations and trace element sr analyses on carbonate constituents across the cretaceous tertiary k t boundary in deep sea drilling project dsdp sites 47 2 356 384 and 577 and compare them with published results from k t boundary sections in other dsdp sites we used the trace element data and scanning electron microscope examination to evaluate possible diagenetic alteration and relative preservation of the samples analyzed in this study the 18o data when interpreted as isotopic paleotemperatures indicate relative stable surface water and deepwater temperatures in the late maestrichtian followed by somewhat fluctuating temperatures in the early paleocene however there is no indication of either a significant warming or cooling at or following the k t boundary several sites do exhibit somewhat heavier 18o values by about 0 5 across the boundary which might suggest a 2 3 c cooling at most however we interpret these somewhat heavier 18o values as reflecting slightly better preservation of 18o of carbonate constitutents in relatively clay rich intervals e g lower diagentic potential characteristic of the k t boundary the 13c values of carbonate fine fraction and planktonic foraminifers indicate a major negative excursion in surface water total dissolved carbon across the boundary the surface water and deepwater 13c values from benthic foraminifers combined with calculated decreases in carbonate accumulation rates at all sites in the earliest paleocene are consistent with a major decrease in productivity across the k t boundary the decrease in caco3 accumulation rates is due not to increased rates of dissolution but to decreased production in surface waters the low productivity episode lasted at least 1 m y beyond the k t boundary crisis suggesting that hypothesized catastrophic events alone such as impact of an apollo object are not the only explanation for the observed long term decrease in productivity there is also an indication in the 13c curves from several sites that the surface water 13c decrease began in the latest maestrichtian suggesting that the decrease in productivity may have been independent of a hypothesized impact event

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

monitoring stress changes in a concrete bridge with coda wave interferometry coda wave interferometry is a recent analysis method now widely used in seismology it uses the increased sensitivity of multiply scattered elastic waves with long travel times for monitoring weak changes in a medium while its application for structural monitoring has been shown to work under laboratory conditions the usability on a real structure with known material changes had yet to be proven this article presents experiments on a concrete bridge during construction the results show that small velocity perturbations induced by a changing stress state in the structure can be determined even under adverse conditions theoretical estimations based on the stress calculations by the structural engineers are in good agreement with the measured velocity variations

lapse time dependent coda wave depth sensitivity to local velocity perturbations in 3 d heterogeneous elastic media in the context of seismic monitoring recent studies made successful use of seismic coda waves to locate medium changes on the horizontal plane locating the depth of the changes however remains a challenge in this paper we use 3 d wavefield simulations to address two problems first we evaluate the contribution of surface and body wave sensitivity to a change at depth we introduce a thin layer with a perturbed velocity at different depths and measure the apparent relative velocity changes due to this layer at different times in the coda and for different degrees of heterogeneity of the model we show that the depth sensitivity can be modelled as a linear combination of body and surface wave sensitivity the lapse time dependent sensitivity ratio of body waves and surface waves can be used to build 3 d sensitivity kernels for imaging purposes second we compare the lapse time behaviour in the presence of a perturbation in horizontal and vertical slabs to address for instance the origin of the velocity changes detected after large earthquakes

paleocene to eocene benthic foraminiferal isotopes and assemblages implications for deepwater circulation early paleogene warm climates may have been linked to different modes and sources of deepwater formation warm polar temperatures of the paleocene and eocene may have resulted from either increased atmospheric trace gases or increased heat transport through deep and intermediate waters the possibility of increasing ocean heat transport through the production of warm saline deep waters wsdw in the tethyan region has generated considerable interest in addition general circulation model results indicate that deepwater source regions may be highly sensitive to changing basin configurations to decipher deepwater changes we examined detailed benthic foraminiferal faunal and isotopic records of the late paleocene through the early eocene 60 to 50 ma from two critical regions the north atlantic bay of biscay site 401 and the pacific shatsky rise site 577 these records are compared with published data from the southern ocean maud rise site 690 islas orcadas rise site 702 during the late paleocene similar benthic foraminiferal 18o values were recorded at all four sites this indicates uniform deepwater temperatures consistent with a single source of deep water the highest 13c values were recorded in the southern ocean and were 0 5 more positive than those of the pacific we infer that the southern ocean was proximal to a source of nutrient depleted deep water during the late paleocene upper paleocene reflector ab was cut on the western bermuda rise by cyclonically circulating bottom water also suggesting a vigorous source of bottom water in the southern ocean a dramatic negative excursion in both carbon and oxygen isotopes occurred in the latest paleocene in the southern ocean this is a short term 100 kyr globally synchronous event which also is apparent in both the atlantic and pacific records as a carbon isotopic excursion of approximately 1 faunal analyses from the north atlantic and pacific sites indicate that the largest benthic foraminiferal faunal turnover of the cenozoic was synchronous with the isotopic excursion lending support to the hypothesis that the extinctions were caused by a change in deepwater circulation we speculate that the southern ocean deepwater source was reduced or eliminated at the time of the excursion during the early eocene southern ocean 13c values remained enriched relative to the north atlantic and pacific however the southern ocean was also enriched in 18o relative to these basins we interpret that these patterns indicate that although the southern ocean was proximal to a source of cool nutrient depleted water the intermediate to upper deep water sites of the north atlantic and pacific were ventilated by a different source that probably originated in low latitudes i e wsdw

atlantic mediterranean water exchange during the late neocene the nature of water exchange between the mediterranean and the atlantic is examined for three time periods during the late neogene in order to assess the impact of flow patterns between these basins on bottom water conditions in the oceans the large volume of carbonates and evaporites deposited in the mediterranean during the messinian salinity crisis appears to have caused the open ocean to become more undersaturated in calcium carbonate resulting in increased dissolution of deep sea carbonates during the latest miocene during the earliest pliocene an estuarine type of flow existed between the atlantic and mediterranean waters entered the mediterranean at depth and flowed out at the surface benthic foraminiferal stable isotopic evidence from the north atlantic indicates that north atlantic deep water nadw was produced throughout the early pliocene and that the absence of saline mediterranean outflow did not have a significant effect on bottom water production eustatic lowering of sea level during the last glacial maximum 18 000 years b p reduced water exchange between the atlantic and the mediterranean as a result salinities in the mediterranean increased substantially but it seems unlikely that diminished nadw production during the last glacial episode can be attributed to a reduction in mediterranean outflow

time lapse monitoring of rock properties with coda wave interferometry 1 the coda of seismic waves consists of that part of the signal after the directly arriving phases in a finite medium or in one that is strongly heterogeneous the coda is dominated by waves which have repeatedly sampled the medium small changes in a medium which may have no detectable influence on the first arrivals are amplified by this repeated sampling and may thus be detectable in the coda we refer to this use of multiple sampling coda waveforms as coda wave interferometry we have exploited ultrasonic coda waves to monitor time varying rock properties in a laboratory environment we have studied the dependence of velocity on uniaxial stress in berea sandstone the temperature dependence of velocity in granite and in aluminum and the change in velocity due to an increase of water saturation in sandstone there are many other possible applications of coda wave interferometry in geophysics including dam and volcano monitoring time lapse reservoir characterization earthquake relocation and stress monitoring in mining and rock physics

geophysical monitoring of moisture induced landslides a review author s whiteley js chambers je uhlemann s wilkinson pb kendall jm abstract 2018 the authors geophysical monitoring of landslides can provide insights into spatial and temporal variations of subsurface properties associated with slope failure recent improvements in equipment data analysis and field operations have led to a significant increase in the use of such techniques in monitoring geophysical methods complement intrusive approaches which sample only a very small proportion of the subsurface and walk over or remotely sensed data which principally provide information only at the ground surface in particular recent studies show that advances in geophysical instrumentation data processing modeling and interpretation in the context of landslide monitoring are significantly improving the characterization of hillslope hydrology and soil and rock hydrology and strength and their dynamics over time this review appraises the state of the art of geophysical monitoring as applied to moisture induced landslides here we focus on technical and practical uses of time lapse methods in geophysics applied to monitoring moisture induced landslide the case studies identified in this review show that several geophysical techniques are currently used in the monitoring of subsurface landslide processes these geophysical contributions to monitoring and predicting the evolution of landslide processes are currently underrealized hence the further integration of multiple parametric and geotechnically coupled geophysical monitoring systems has considerable potential the complementary nature of certain methods to map the distribution of subsurface moisture and elastic moduli will greatly increase the predictive and monitoring capacity of early warning systems in moisture induced landslide settings

glacio eustatic sea level control on red sea salinity previous studies of the red sea demonstrated that glacial surface and bottom water salinities in the basin were significantly higher than at present the very low abundance of planktonic foraminifera the so called aplanktonic zone during the last glacial indicates that surface water conditions approached or exceeded the tolerance limits of this plankton group1 2 glacial sediments are also characterized by high concentrations of magnesian calcite3 4 dolomite3 inorganically precipitated aragonite4 5 and benthic foraminifera typical of hypersaline environments3 6 additional evidence from oxygen isotope records of planktonic2 7 and benthic foraminifera8 9 as well as pteropods2 demonstrate that glacial interglacial contrasts in the red sea have an amplitude much larger than typically observed in open ocean records here we use both oxygen isotope data and a fractional overmixing model to estimate the impact of the most recent 18 000 yr bp pleistocene glacio eustatic sea level lowering on red sea salinity we estimate that during the last glacial maximum surface salinities in the central red sea were more than 10 0 higher than at present deep water salinities were also higher during the last glaciation and remained unusually high through deglaciation the combination of very high bottom salinities and the onset of pluvial conditions during deglaciation in the red sea region prevented ventilation of red sea bottom waters and resulted in the accumulation of organic rich sediments

coda wave interferometry for estimating nonlinear behavior in seismic velocity in coda wave interferometry one records multiply scattered waves at a limited number of receivers to infer changes in the medium over time with this technique we have determined the nonlinear dependence of the seismic velocity in granite on temperature and the associated acoustic emissions this technique can be used in warning mode to detect the presence of temporal changes in the medium or in diagnostic mode where the temporal change in the medium is quantified

abrupt climate change and transient climates during the paleogene a marine perspective detailed investigations of high latitude sequences recently collected by the ocean drilling program odp indicate that periods of rapid climate change often culminated in brief transient climates with more extreme conditions than subsequent long term climates two examples of such events have been identified in the paleogene the first in latest paleocene time in the middle of a warming trend that began several million years earlier the second in earliest oligocene time near the end of a middle eocene to late oligocene global cooling trend superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice sheet on antarctica in both cases the climate extremes were not stable lasting for less than a few hundred thousand years indicating a temporary or transient climate state geochemical and sedimentolog

the value of seismic amplitude we have always observed amplitude in the seismic signal but in the early days we were concerned with its existence and not its magnitude because our objectives were only structural digital processing today generally seeks to preserve true amplitude so that stratigraphic inferences can be made from it and more subsurface information extracted from our seismic data but how true are these amplitudes and how much can we infer from them a workshop at the 1985 seg annual meeting in washington focused on this subject and concluded that our ability to control and understand seismic amplitude is far from perfect this is undoubtedly true but there is nevertheless much valuable information in seismic amplitude that we must use to the full in our seismic interpretations and in our critical exploration and development decision making

improving temporal resolution in ambient noise monitoring of seismic wave speed 1 the use of ambient seismic noise has been intensively investigated to perform passive tomography at various scales besides passive tomography passive monitoring is another application of seismic noise correlation as was shown by the recent observation of postseismic velocity changes around the san andreas fault in parkfield california one of the drawbacks of using ambient noise correlation for passive monitoring is the need to average the correlations over a long time period in order to obtain a sufficient signal to noise ratio snr for the phase fluctuations to be measured accurately for the application to passive monitoring one wants the possibility of following short term velocity variations 1 day or less using noise correlation functions calculated on short time windows another difficulty may then appear when the spatial distribution of noise sources also evolves with time the aim of this paper is to introduce an adaptive filter to the parkfield data set in order to improve the snr output of the ambient noise correlation functions when applied to passive monitoring the temporal resolution can be increased from 30 days up to 1 day with this improved temporal resolution the velocity drop observed at parkfield is shown to be cosesimic with the 24 september 2004 mw 6 0 event the relationship between the measured velocity fluctuations and the time evolution of the spatial distribution of the noise wavefield is also investigated finally the error bar in the amplitudes of the velocity variations is compared with a theoretical expectation

ultrasonic imaging of the onset and growth of fractures within partially saturated whitby mudstone using coda wave decorrelation inversion using active ultrasonic source survey data coda wave decorrelation cwd time lapse imaging during the triaxial compression of whitby mudstone cores provides a 3 d description of the evolution and

warm saline bottom water in the ancient ocean considerable isotopic evidence indicates that oceanic bottom water was much warmer in the geological past a simple convection model driven by multiple turbulent buoyant plumes and observations of present deep water formation have led to the development of a theory for the formation of warm saline bottom water it is suggested that changes in the size and configuration of marginal seas in net evaporation zones due to lithospheric plate motions and eustatic sea level change caused these seas to become sources of warm saline bottom water evidence from the palaeotemperature record and palaeogeography during the late cretaceous is used to reinforce the hypothesis climatic and chemical consequences of the formation of warm saline bottom water are discussed

low productivity and slow deep water circulation in mid cretaceous oceans paleofertility estimates are derived from organic carbon accumulation rates determined in nonbioturbated mid cretaceous deep sea deposits using organic carbon preservation factors observed in laminated sediments from anoxic holocene environments the estimated mid cretaceous primary production rates are as much as an order of magnitude lower than those measured in today s oceans an evaluation of dissolved oxygen budgets using a simple oceanic circulation model indicates very low deep water renewal rates in mid cretaceous oceans 28 references 2 tables 4 figures

variability in the deep and intermediate water circulation of the atlantic ocean during the past 25 000 years northern hemisphere modulation of the southern ocean the relative flux of north atlantic deep water nadw out of the atlantic can be monitored in the southern ocean where high 13c nadw mixes rapidly with low 13c recirculated pacific water before forming antarctic bottom water aabw by using 13c measured in benthic foraminifera as a water mass tracer it is shown that the southern ocean was dominated by pacific water with little nadw contribution during the last glaciation these tracer results document the direct physical connection between insolation controlled northern hemisphere oscillations and changes in the chemical and physical properties of southern ocean water the 13c records from the deep tropical atlantic document the transition from an atlantic dominated by southern ocean water during the last glaciation to an atlantic dominated by nadw during the holocene with more southern ocean water in the deep atlantic during the last glaciation the boundary between nadw and southern ocean water was north of its modern position allowing more southern ocean water to enter the eastern atlantic through the romanche fracture zone carbon isotope records from the caribbean and mediterranean seas suggest that the influence of mediterranean overflow water mow extended to the caribbean during the last glaciation and therefore was a volumetrically much more important water mass in the intermediate depth atlantic than it is today

reduced advection into atlantic ocean deep eastern basins during last glaciation maximum causes of change in deep water 13c can be either global or local in extent global causes include 1 climatically induced changes in the amount of terrestrial biomass which alter the average carbon isotopic composition of the oceanic reservoir1 and 2 erosion and deposition of organic rich continental shelf sediments during sea level fluctuations which change the mean oceanic carbon phosphorus ratio2 regional gradients of 13c are created by remineralization of organic detritus within the deep ocean itself thus reflecting the distribution of water masses and modern thermohaline flow changes in a single geological record of benthic foraminiferal 13c can result from any combination of these global and abyssal circulation effects by sampling a large number of cores collected over a wide bathymetric range yet confined to a small geographical region we have minimized the ambiguity we can assume that each 13c record was equally affected by global causes of 13c variation the differences seen between the 13c records must therefore reflect changes in the distribution of 13c in the deep ocean we interpret these differences in distribution in terms of changes in the ocean s abyssal circulation benthic foraminiferal carbon isotopic evidence from a suite of sierra leone rise cores indicates that the deeper parts of the eastern atlantic basins underwent a reduction in o2 during the maximum of the last glaciation reduced advection of o2 rich deep water through low latitude fracture zones associated with increased delivery of organic matter to the deep ocean lowered the 13c of deep water co2 at all depths below the sill separating the eastern and western atlantic basins 3 this decreased advection into the eastern atlantic ocean coincides with the overall decrease in deep water production in the north atlantic during the last glacial maximum4 7

structural monitoring of a highway bridge using passive noise recordings from street traffic structural damage on bridges presents a hazard to public safety and can lead to fatalities this article contributes to the development of an alternative monitoring system for civil structures based on passive measurements of seismic elastic waves cross correlations of traffic noise recorded at geophone receiver pairs were found to be sufficiently stable for comparison and sensitive to velocity changes in the medium as such velocity variations could be caused by damage their detection would be valuable in structural health monitoring systems a method originally introduced for seismological applications and named passive image interferometry was used to quantify small velocity fluctuations in the medium and thereby observe structural changes evaluation of more than 2 months of continuous geophone recordings at a reinforced concrete bridge yielded velocity variations v v in the range of 1 5 to 2 1 the observed fluctuations correlate with associated temperature time series with a striking resem

application of seismic interferometry by multidimensional deconvolution to ambient seismic noise recorded in malargue argentina obtaining new seismic responses from existing recordings is generally referred to as seismic interferometry si conventionally the si responses are retrieved by simple crosscorrelation of recordings made by separate receivers one of the receivers acts as a virtual source whose response is retrieved at the other receivers when si is applied to recordings of ambient seismic noise mostly surface waves are retrieved the newly retrieved surface wave responses can be used to extract receiver receiver phase velocities these phase velocities often serve as input parameters for tomographic inverse problems another application of si exploits the tempo ral stability of the multiply scattered arrivals of the newly retrieved surface wave responses temporal variations in the stability and or arrival time of these multiply scattered arrivals can often be linked to temporally varying parameters such as hydrocarbon production and precip itation for all applications however the accuracy of the retrieved responses is paramount correct response retrieval relies on a uniform illumination of the receivers irregularities in the illumination pattern degrade the accuracy of the newly retrieved responses in practice the illumination pattern is often far from uniform in that case simple crosscorrelation of separate receiver recordings only yields an estimate of the actual correct virtual source response re formulating the theory underlying si by crosscorrelation as a multidimensional deconvolution mdd process allows this estimate to be improved si by mdd corrects for the non uniform illumination pattern by means of a so called point spread function psf which captures the irregularities in the illumination pattern deconvolution by this psf removes the imprint of the irregularities on the responses obtained through simple crosscorrelation we apply si by mdd to surface wave data recorded by themalargue seismic array in western argentina the aperture of the array is approximately 60 km and it is located on a plateau just east of the andean mountain range the array has a t shape the receivers along one of the two lines act as virtual sources whose responses are recorded by the receivers along the other perpendicular line we select time windows dominated by surface wave noise travelling in a favourable direction that is traversing the line of virtual sources before arriving at the receivers at which we aim to retrieve the virtual source responses these time windows are selected through a frequency dependent slowness analysis along the two receiver lines from the selected time windows estimates of virtual source responses are retrieved by means of crosscorrelations similarly crosscorrelations between the positions of the virtual sources are computed to build the psf we use the psf to deconvolve the effect of illumination irregularities and the source function from the virtual source responses retrieved by crosscorrelation the combined effect of time window selection and mdd results in more accurate and temporally stable surface wave responses